12375116696

Committed 17 Dec 2024 02:29PM UTC coverage: 58.366% (-0.2%) from 58.595%

Build # 12375116696

Build Type

Pull #8777

github

Committed by

ziggie1984

Commit Message

docs: add release-notes

Pull Request Pull Request #8777: multi: make deletion of edge atomic.

Run Details

132 of 177 new or added lines in 6 files covered. (74.58%)

670 existing lines in 37 files now uncovered.

133926 of 229458 relevant lines covered (58.37%)

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77.26

/graph/db/graph.go

package graphdb

import (
        "bytes"
        "crypto/sha256"
        "encoding/binary"
        "errors"
        "fmt"
        "io"
        "math"
        "net"
        "sort"
        "sync"
        "testing"
        "time"

        "github.com/btcsuite/btcd/btcec/v2"
        "github.com/btcsuite/btcd/chaincfg/chainhash"
        "github.com/btcsuite/btcd/txscript"
        "github.com/btcsuite/btcd/wire"
        "github.com/lightningnetwork/lnd/aliasmgr"
        "github.com/lightningnetwork/lnd/batch"
        "github.com/lightningnetwork/lnd/graph/db/models"
        "github.com/lightningnetwork/lnd/input"
        "github.com/lightningnetwork/lnd/kvdb"
        "github.com/lightningnetwork/lnd/lnwire"
        "github.com/lightningnetwork/lnd/routing/route"
)

var (
        // nodeBucket is a bucket which houses all the vertices or nodes within
        // the channel graph. This bucket has a single-sub bucket which adds an
        // additional index from pubkey -> alias. Within the top-level of this
        // bucket, the key space maps a node's compressed public key to the
        // serialized information for that node. Additionally, there's a
        // special key "source" which stores the pubkey of the source node. The
        // source node is used as the starting point for all graph/queries and
        // traversals. The graph is formed as a star-graph with the source node
        // at the center.
        //
        // maps: pubKey -> nodeInfo
        // maps: source -> selfPubKey
        nodeBucket = []byte("graph-node")

        // nodeUpdateIndexBucket is a sub-bucket of the nodeBucket. This bucket
        // will be used to quickly look up the "freshness" of a node's last
        // update to the network. The bucket only contains keys, and no values,
        // it's mapping:
        //
        // maps: updateTime || nodeID -> nil
        nodeUpdateIndexBucket = []byte("graph-node-update-index")

        // sourceKey is a special key that resides within the nodeBucket. The
        // sourceKey maps a key to the public key of the "self node".
        sourceKey = []byte("source")

        // aliasIndexBucket is a sub-bucket that's nested within the main
        // nodeBucket. This bucket maps the public key of a node to its
        // current alias. This bucket is provided as it can be used within a
        // future UI layer to add an additional degree of confirmation.
        aliasIndexBucket = []byte("alias")

        // edgeBucket is a bucket which houses all of the edge or channel
        // information within the channel graph. This bucket essentially acts
        // as an adjacency list, which in conjunction with a range scan, can be
        // used to iterate over all the incoming and outgoing edges for a
        // particular node. Key in the bucket use a prefix scheme which leads
        // with the node's public key and sends with the compact edge ID.
        // For each chanID, there will be two entries within the bucket, as the
        // graph is directed: nodes may have different policies w.r.t to fees
        // for their respective directions.
        //
        // maps: pubKey || chanID -> channel edge policy for node
        edgeBucket = []byte("graph-edge")

        // unknownPolicy is represented as an empty slice. It is
        // used as the value in edgeBucket for unknown channel edge policies.
        // Unknown policies are still stored in the database to enable efficient
        // lookup of incoming channel edges.
        unknownPolicy = []byte{}

        // chanStart is an array of all zero bytes which is used to perform
        // range scans within the edgeBucket to obtain all of the outgoing
        // edges for a particular node.
        chanStart [8]byte

        // edgeIndexBucket is an index which can be used to iterate all edges
        // in the bucket, grouping them according to their in/out nodes.
        // Additionally, the items in this bucket also contain the complete
        // edge information for a channel. The edge information includes the
        // capacity of the channel, the nodes that made the channel, etc. This
        // bucket resides within the edgeBucket above. Creation of an edge
        // proceeds in two phases: first the edge is added to the edge index,
        // afterwards the edgeBucket can be updated with the latest details of
        // the edge as they are announced on the network.
        //
        // maps: chanID -> pubKey1 || pubKey2 || restofEdgeInfo
        edgeIndexBucket = []byte("edge-index")

        // edgeUpdateIndexBucket is a sub-bucket of the main edgeBucket. This
        // bucket contains an index which allows us to gauge the "freshness" of
        // a channel's last updates.
        //
        // maps: updateTime || chanID -> nil
        edgeUpdateIndexBucket = []byte("edge-update-index")

        // channelPointBucket maps a channel's full outpoint (txid:index) to
        // its short 8-byte channel ID. This bucket resides within the
        // edgeBucket above, and can be used to quickly remove an edge due to
        // the outpoint being spent, or to query for existence of a channel.
        //
        // maps: outPoint -> chanID
        channelPointBucket = []byte("chan-index")

        // zombieBucket is a sub-bucket of the main edgeBucket bucket
        // responsible for maintaining an index of zombie channels. Each entry
        // exists within the bucket as follows:
        //
        // maps: chanID -> pubKey1 || pubKey2
        //
        // The chanID represents the channel ID of the edge that is marked as a
        // zombie and is used as the key, which maps to the public keys of the
        // edge's participants.
        zombieBucket = []byte("zombie-index")

        // disabledEdgePolicyBucket is a sub-bucket of the main edgeBucket
        // bucket responsible for maintaining an index of disabled edge
        // policies. Each entry exists within the bucket as follows:
        //
        // maps: <chanID><direction> -> []byte{}
        //
        // The chanID represents the channel ID of the edge and the direction is
        // one byte representing the direction of the edge. The main purpose of
        // this index is to allow pruning disabled channels in a fast way without
        // the need to iterate all over the graph.
        disabledEdgePolicyBucket = []byte("disabled-edge-policy-index")

        // graphMetaBucket is a top-level bucket which stores various meta-deta
        // related to the on-disk channel graph. Data stored in this bucket
        // includes the block to which the graph has been synced to, the total
        // number of channels, etc.
        graphMetaBucket = []byte("graph-meta")

        // pruneLogBucket is a bucket within the graphMetaBucket that stores
        // a mapping from the block height to the hash for the blocks used to
        // prune the graph.
        // Once a new block is discovered, any channels that have been closed
        // (by spending the outpoint) can safely be removed from the graph, and
        // the block is added to the prune log. We need to keep such a log for
        // the case where a reorg happens, and we must "rewind" the state of the
        // graph by removing channels that were previously confirmed. In such a
        // case we'll remove all entries from the prune log with a block height
        // that no longer exists.
        pruneLogBucket = []byte("prune-log")

        // closedScidBucket is a top-level bucket that stores scids for
        // channels that we know to be closed. This is used so that we don't
        // need to perform expensive validation checks if we receive a channel
        // announcement for the channel again.
        //
        // maps: scid -> []byte{}
        closedScidBucket = []byte("closed-scid")
)

const (
        // MaxAllowedExtraOpaqueBytes is the largest amount of opaque bytes that
        // we'll permit to be written to disk. We limit this as otherwise, it
        // would be possible for a node to create a ton of updates and slowly
        // fill our disk, and also waste bandwidth due to relaying.
        MaxAllowedExtraOpaqueBytes = 10000
)

// ChannelGraph is a persistent, on-disk graph representation of the Lightning
// Network. This struct can be used to implement path finding algorithms on top
// of, and also to update a node's view based on information received from the
// p2p network. Internally, the graph is stored using a modified adjacency list
// representation with some added object interaction possible with each
// serialized edge/node. The graph is stored is directed, meaning that are two
// edges stored for each channel: an inbound/outbound edge for each node pair.
// Nodes, edges, and edge information can all be added to the graph
// independently. Edge removal results in the deletion of all edge information
// for that edge.
type ChannelGraph struct {
        db kvdb.Backend

        // cacheMu guards all caches (rejectCache, chanCache, graphCache). If
        // this mutex will be acquired at the same time as the DB mutex then
        // the cacheMu MUST be acquired first to prevent deadlock.
        cacheMu     sync.RWMutex
        rejectCache *rejectCache
        chanCache   *channelCache
        graphCache  *GraphCache

        chanScheduler batch.Scheduler
        nodeScheduler batch.Scheduler
}

// NewChannelGraph allocates a new ChannelGraph backed by a DB instance. The
// returned instance has its own unique reject cache and channel cache.
func NewChannelGraph(db kvdb.Backend, options ...OptionModifier) (*ChannelGraph,
        error) {

        opts := DefaultOptions()
        for _, o := range options {
                o(opts)
        }

        if !opts.NoMigration {
                if err := initChannelGraph(db); err != nil {
                        return nil, err
                }
        }

        g := &ChannelGraph{
                db:          db,
                rejectCache: newRejectCache(opts.RejectCacheSize),
                chanCache:   newChannelCache(opts.ChannelCacheSize),
        }
        g.chanScheduler = batch.NewTimeScheduler(
                db, &g.cacheMu, opts.BatchCommitInterval,
        )
        g.nodeScheduler = batch.NewTimeScheduler(
                db, nil, opts.BatchCommitInterval,
        )

        // The graph cache can be turned off (e.g. for mobile users) for a
        // speed/memory usage tradeoff.
        if opts.UseGraphCache {
                g.graphCache = NewGraphCache(opts.PreAllocCacheNumNodes)
                startTime := time.Now()
                log.Debugf("Populating in-memory channel graph, this might " +
                        "take a while...")

                err := g.ForEachNodeCacheable(
                        func(tx kvdb.RTx, node GraphCacheNode) error {
                                g.graphCache.AddNodeFeatures(node)

                                return nil
                        },
                )
                if err != nil {
                        return nil, err
                }

                err = g.ForEachChannel(func(info *models.ChannelEdgeInfo,
                        policy1, policy2 *models.ChannelEdgePolicy) error {

                        g.graphCache.AddChannel(info, policy1, policy2)

                        return nil
                })
                if err != nil {
                        return nil, err
                }

                log.Debugf("Finished populating in-memory channel graph (took "+
                        "%v, %s)", time.Since(startTime), g.graphCache.Stats())
        }

        return g, nil
}

// channelMapKey is the key structure used for storing channel edge policies.
type channelMapKey struct {
        nodeKey route.Vertex
        chanID  [8]byte
}

// getChannelMap loads all channel edge policies from the database and stores
// them in a map.
func (c *ChannelGraph) getChannelMap(edges kvdb.RBucket) (
        map[channelMapKey]*models.ChannelEdgePolicy, error) {

        // Create a map to store all channel edge policies.
        channelMap := make(map[channelMapKey]*models.ChannelEdgePolicy)

        err := kvdb.ForAll(edges, func(k, edgeBytes []byte) error {
                // Skip embedded buckets.
                if bytes.Equal(k, edgeIndexBucket) ||
                        bytes.Equal(k, edgeUpdateIndexBucket) ||
                        bytes.Equal(k, zombieBucket) ||
                        bytes.Equal(k, disabledEdgePolicyBucket) ||
                        bytes.Equal(k, channelPointBucket) {

                        return nil
                }

                // Validate key length.
                if len(k) != 33+8 {
                        return fmt.Errorf("invalid edge key %x encountered", k)
                }

                var key channelMapKey
                copy(key.nodeKey[:], k[:33])
                copy(key.chanID[:], k[33:])

                // No need to deserialize unknown policy.
                if bytes.Equal(edgeBytes, unknownPolicy) {
                        return nil
                }

                edgeReader := bytes.NewReader(edgeBytes)
                edge, err := deserializeChanEdgePolicyRaw(
                        edgeReader,
                )

                switch {
                // If the db policy was missing an expected optional field, we
                // return nil as if the policy was unknown.
                case err == ErrEdgePolicyOptionalFieldNotFound:
                        return nil

                case err != nil:
                        return err
                }

                channelMap[key] = edge

                return nil
        })
        if err != nil {
                return nil, err
        }

        return channelMap, nil
}

var graphTopLevelBuckets = [][]byte{
        nodeBucket,
        edgeBucket,
        graphMetaBucket,
        closedScidBucket,
}

// Wipe completely deletes all saved state within all used buckets within the
// database. The deletion is done in a single transaction, therefore this
// operation is fully atomic.
func (c *ChannelGraph) Wipe() error {
        err := kvdb.Update(c.db, func(tx kvdb.RwTx) error {
                for _, tlb := range graphTopLevelBuckets {
                        err := tx.DeleteTopLevelBucket(tlb)
                        if err != nil && err != kvdb.ErrBucketNotFound {
                                return err
                        }
                }
                return nil
        }, func() {})
        if err != nil {
                return err
        }

        return initChannelGraph(c.db)
}

// createChannelDB creates and initializes a fresh version of  In
// the case that the target path has not yet been created or doesn't yet exist,
// then the path is created. Additionally, all required top-level buckets used
// within the database are created.
func initChannelGraph(db kvdb.Backend) error {
        err := kvdb.Update(db, func(tx kvdb.RwTx) error {
                for _, tlb := range graphTopLevelBuckets {
                        if _, err := tx.CreateTopLevelBucket(tlb); err != nil {
                                return err
                        }
                }

                nodes := tx.ReadWriteBucket(nodeBucket)
                _, err := nodes.CreateBucketIfNotExists(aliasIndexBucket)
                if err != nil {
                        return err
                }
                _, err = nodes.CreateBucketIfNotExists(nodeUpdateIndexBucket)
                if err != nil {
                        return err
                }

                edges := tx.ReadWriteBucket(edgeBucket)
                _, err = edges.CreateBucketIfNotExists(edgeIndexBucket)
                if err != nil {
                        return err
                }
                _, err = edges.CreateBucketIfNotExists(edgeUpdateIndexBucket)
                if err != nil {
                        return err
                }
                _, err = edges.CreateBucketIfNotExists(channelPointBucket)
                if err != nil {
                        return err
                }
                _, err = edges.CreateBucketIfNotExists(zombieBucket)
                if err != nil {
                        return err
                }

                graphMeta := tx.ReadWriteBucket(graphMetaBucket)
                _, err = graphMeta.CreateBucketIfNotExists(pruneLogBucket)
                return err
        }, func() {})
        if err != nil {
                return fmt.Errorf("unable to create new channel graph: %w", err)
        }

        return nil
}

// NewPathFindTx returns a new read transaction that can be used for a single
// path finding session. Will return nil if the graph cache is enabled.
func (c *ChannelGraph) NewPathFindTx() (kvdb.RTx, error) {
        if c.graphCache != nil {
                return nil, nil
        }

        return c.db.BeginReadTx()
}

// AddrsForNode returns all known addresses for the target node public key that
// the graph DB is aware of. The returned boolean indicates if the given node is
// unknown to the graph DB or not.
//
// NOTE: this is part of the channeldb.AddrSource interface.
func (c *ChannelGraph) AddrsForNode(nodePub *btcec.PublicKey) (bool, []net.Addr,
        error) {

        pubKey, err := route.NewVertexFromBytes(nodePub.SerializeCompressed())
        if err != nil {
                return false, nil, err
        }

        node, err := c.FetchLightningNode(pubKey)
        // We don't consider it an error if the graph is unaware of the node.
        switch {
        case err != nil && !errors.Is(err, ErrGraphNodeNotFound):
                return false, nil, err

        case errors.Is(err, ErrGraphNodeNotFound):
                return false, nil, nil
        }

        return true, node.Addresses, nil
}

// ForEachChannel iterates through all the channel edges stored within the
// graph and invokes the passed callback for each edge. The callback takes two
// edges as since this is a directed graph, both the in/out edges are visited.
// If the callback returns an error, then the transaction is aborted and the
// iteration stops early.
//
// NOTE: If an edge can't be found, or wasn't advertised, then a nil pointer
// for that particular channel edge routing policy will be passed into the
// callback.
func (c *ChannelGraph) ForEachChannel(cb func(*models.ChannelEdgeInfo,
        *models.ChannelEdgePolicy, *models.ChannelEdgePolicy) error) error {

        return c.db.View(func(tx kvdb.RTx) error {
                edges := tx.ReadBucket(edgeBucket)
                if edges == nil {
                        return ErrGraphNoEdgesFound
                }

                // First, load all edges in memory indexed by node and channel
                // id.
                channelMap, err := c.getChannelMap(edges)
                if err != nil {
                        return err
                }

                edgeIndex := edges.NestedReadBucket(edgeIndexBucket)
                if edgeIndex == nil {
                        return ErrGraphNoEdgesFound
                }

                // Load edge index, recombine each channel with the policies
                // loaded above and invoke the callback.
                return kvdb.ForAll(
                        edgeIndex, func(k, edgeInfoBytes []byte) error {
                                var chanID [8]byte
                                copy(chanID[:], k)

                                edgeInfoReader := bytes.NewReader(edgeInfoBytes)
                                info, err := deserializeChanEdgeInfo(
                                        edgeInfoReader,
                                )
                                if err != nil {
                                        return err
                                }

                                policy1 := channelMap[channelMapKey{
                                        nodeKey: info.NodeKey1Bytes,
                                        chanID:  chanID,
                                }]

                                policy2 := channelMap[channelMapKey{
                                        nodeKey: info.NodeKey2Bytes,
                                        chanID:  chanID,
                                }]

                                return cb(&info, policy1, policy2)
                        },
                )
        }, func() {})
}

// ForEachNodeDirectedChannel iterates through all channels of a given node,
// executing the passed callback on the directed edge representing the channel
// and its incoming policy. If the callback returns an error, then the iteration
// is halted with the error propagated back up to the caller.
//
// Unknown policies are passed into the callback as nil values.
func (c *ChannelGraph) ForEachNodeDirectedChannel(tx kvdb.RTx,
        node route.Vertex, cb func(channel *DirectedChannel) error) error {

        if c.graphCache != nil {
                return c.graphCache.ForEachChannel(node, cb)
        }

        // Fallback that uses the database.
        toNodeCallback := func() route.Vertex {
                return node
        }
        toNodeFeatures, err := c.FetchNodeFeatures(node)
        if err != nil {
                return err
        }

        dbCallback := func(tx kvdb.RTx, e *models.ChannelEdgeInfo, p1,
                p2 *models.ChannelEdgePolicy) error {

                var cachedInPolicy *models.CachedEdgePolicy
                if p2 != nil {
                        cachedInPolicy = models.NewCachedPolicy(p2)
                        cachedInPolicy.ToNodePubKey = toNodeCallback
                        cachedInPolicy.ToNodeFeatures = toNodeFeatures
                }

                var inboundFee lnwire.Fee
                if p1 != nil {
                        // Extract inbound fee. If there is a decoding error,
                        // skip this edge.
                        _, err := p1.ExtraOpaqueData.ExtractRecords(&inboundFee)
                        if err != nil {
                                return nil
                        }
                }

                directedChannel := &DirectedChannel{
                        ChannelID:    e.ChannelID,
                        IsNode1:      node == e.NodeKey1Bytes,
                        OtherNode:    e.NodeKey2Bytes,
                        Capacity:     e.Capacity,
                        OutPolicySet: p1 != nil,
                        InPolicy:     cachedInPolicy,
                        InboundFee:   inboundFee,
                }

                if node == e.NodeKey2Bytes {
                        directedChannel.OtherNode = e.NodeKey1Bytes
                }

                return cb(directedChannel)
        }
        return nodeTraversal(tx, node[:], c.db, dbCallback)
}

// FetchNodeFeatures returns the features of a given node. If no features are
// known for the node, an empty feature vector is returned.
func (c *ChannelGraph) FetchNodeFeatures(
        node route.Vertex) (*lnwire.FeatureVector, error) {

        if c.graphCache != nil {
                return c.graphCache.GetFeatures(node), nil
        }

        // Fallback that uses the database.
        targetNode, err := c.FetchLightningNode(node)
        switch err {
        // If the node exists and has features, return them directly.
        case nil:
                return targetNode.Features, nil

        // If we couldn't find a node announcement, populate a blank feature
        // vector.
        case ErrGraphNodeNotFound:
                return lnwire.EmptyFeatureVector(), nil

        // Otherwise, bubble the error up.
        default:
                return nil, err
        }
}

// ForEachNodeCached is similar to ForEachNode, but it utilizes the channel
// graph cache instead. Note that this doesn't return all the information the
// regular ForEachNode method does.
//
// NOTE: The callback contents MUST not be modified.
func (c *ChannelGraph) ForEachNodeCached(cb func(node route.Vertex,
        chans map[uint64]*DirectedChannel) error) error {

        if c.graphCache != nil {
                return c.graphCache.ForEachNode(cb)
        }

        // Otherwise call back to a version that uses the database directly.
        // We'll iterate over each node, then the set of channels for each
        // node, and construct a similar callback functiopn signature as the
        // main funcotin expects.
        return c.ForEachNode(func(tx kvdb.RTx,
                node *models.LightningNode) error {

                channels := make(map[uint64]*DirectedChannel)

                err := c.ForEachNodeChannelTx(tx, node.PubKeyBytes,
                        func(tx kvdb.RTx, e *models.ChannelEdgeInfo,
                                p1 *models.ChannelEdgePolicy,
                                p2 *models.ChannelEdgePolicy) error {

                                toNodeCallback := func() route.Vertex {
                                        return node.PubKeyBytes
                                }
                                toNodeFeatures, err := c.FetchNodeFeatures(
                                        node.PubKeyBytes,
                                )
                                if err != nil {
                                        return err
                                }

                                var cachedInPolicy *models.CachedEdgePolicy
                                if p2 != nil {
                                        cachedInPolicy =
                                                models.NewCachedPolicy(p2)
                                        cachedInPolicy.ToNodePubKey =
                                                toNodeCallback
                                        cachedInPolicy.ToNodeFeatures =
                                                toNodeFeatures
                                }

                                directedChannel := &DirectedChannel{
                                        ChannelID: e.ChannelID,
                                        IsNode1: node.PubKeyBytes ==
                                                e.NodeKey1Bytes,
                                        OtherNode:    e.NodeKey2Bytes,
                                        Capacity:     e.Capacity,
                                        OutPolicySet: p1 != nil,
                                        InPolicy:     cachedInPolicy,
                                }

                                if node.PubKeyBytes == e.NodeKey2Bytes {
                                        directedChannel.OtherNode =
                                                e.NodeKey1Bytes
                                }

                                channels[e.ChannelID] = directedChannel

                                return nil
                        })
                if err != nil {
                        return err
                }

                return cb(node.PubKeyBytes, channels)
        })
}

// DisabledChannelIDs returns the channel ids of disabled channels.
// A channel is disabled when two of the associated ChanelEdgePolicies
// have their disabled bit on.
func (c *ChannelGraph) DisabledChannelIDs() ([]uint64, error) {
        var disabledChanIDs []uint64
        var chanEdgeFound map[uint64]struct{}

        err := kvdb.View(c.db, func(tx kvdb.RTx) error {
                edges := tx.ReadBucket(edgeBucket)
                if edges == nil {
                        return ErrGraphNoEdgesFound
                }

                disabledEdgePolicyIndex := edges.NestedReadBucket(
                        disabledEdgePolicyBucket,
                )
                if disabledEdgePolicyIndex == nil {
                        return nil
                }

                // We iterate over all disabled policies and we add each channel
                // that has more than one disabled policy to disabledChanIDs
                // array.
                return disabledEdgePolicyIndex.ForEach(
                        func(k, v []byte) error {
                                chanID := byteOrder.Uint64(k[:8])
                                _, edgeFound := chanEdgeFound[chanID]
                                if edgeFound {
                                        delete(chanEdgeFound, chanID)
                                        disabledChanIDs = append(
                                                disabledChanIDs, chanID,
                                        )

                                        return nil
                                }

                                chanEdgeFound[chanID] = struct{}{}

                                return nil
                        },
                )
        }, func() {
                disabledChanIDs = nil
                chanEdgeFound = make(map[uint64]struct{})
        })
        if err != nil {
                return nil, err
        }

        return disabledChanIDs, nil
}

// ForEachNode iterates through all the stored vertices/nodes in the graph,
// executing the passed callback with each node encountered. If the callback
// returns an error, then the transaction is aborted and the iteration stops
// early.
//
// TODO(roasbeef): add iterator interface to allow for memory efficient graph
// traversal when graph gets mega
func (c *ChannelGraph) ForEachNode(
        cb func(kvdb.RTx, *models.LightningNode) error) error {

        traversal := func(tx kvdb.RTx) error {
                // First grab the nodes bucket which stores the mapping from
                // pubKey to node information.
                nodes := tx.ReadBucket(nodeBucket)
                if nodes == nil {
                        return ErrGraphNotFound
                }

                return nodes.ForEach(func(pubKey, nodeBytes []byte) error {
                        // If this is the source key, then we skip this
                        // iteration as the value for this key is a pubKey
                        // rather than raw node information.
                        if bytes.Equal(pubKey, sourceKey) || len(pubKey) != 33 {
                                return nil
                        }

                        nodeReader := bytes.NewReader(nodeBytes)
                        node, err := deserializeLightningNode(nodeReader)
                        if err != nil {
                                return err
                        }

                        // Execute the callback, the transaction will abort if
                        // this returns an error.
                        return cb(tx, &node)
                })
        }

        return kvdb.View(c.db, traversal, func() {})
}

// ForEachNodeCacheable iterates through all the stored vertices/nodes in the
// graph, executing the passed callback with each node encountered. If the
// callback returns an error, then the transaction is aborted and the iteration
// stops early.
func (c *ChannelGraph) ForEachNodeCacheable(cb func(kvdb.RTx,
        GraphCacheNode) error) error {

        traversal := func(tx kvdb.RTx) error {
                // First grab the nodes bucket which stores the mapping from
                // pubKey to node information.
                nodes := tx.ReadBucket(nodeBucket)
                if nodes == nil {
                        return ErrGraphNotFound
                }

                return nodes.ForEach(func(pubKey, nodeBytes []byte) error {
                        // If this is the source key, then we skip this
                        // iteration as the value for this key is a pubKey
                        // rather than raw node information.
                        if bytes.Equal(pubKey, sourceKey) || len(pubKey) != 33 {
                                return nil
                        }

                        nodeReader := bytes.NewReader(nodeBytes)
                        cacheableNode, err := deserializeLightningNodeCacheable(
                                nodeReader,
                        )
                        if err != nil {
                                return err
                        }

                        // Execute the callback, the transaction will abort if
                        // this returns an error.
                        return cb(tx, cacheableNode)
                })
        }

        return kvdb.View(c.db, traversal, func() {})
}

// SourceNode returns the source node of the graph. The source node is treated
// as the center node within a star-graph. This method may be used to kick off
// a path finding algorithm in order to explore the reachability of another
// node based off the source node.
func (c *ChannelGraph) SourceNode() (*models.LightningNode, error) {
        var source *models.LightningNode
        err := kvdb.View(c.db, func(tx kvdb.RTx) error {
                // First grab the nodes bucket which stores the mapping from
                // pubKey to node information.
                nodes := tx.ReadBucket(nodeBucket)
                if nodes == nil {
                        return ErrGraphNotFound
                }

                node, err := c.sourceNode(nodes)
                if err != nil {
                        return err
                }
                source = node

                return nil
        }, func() {
                source = nil
        })
        if err != nil {
                return nil, err
        }

        return source, nil
}

// sourceNode uses an existing database transaction and returns the source node
// of the graph. The source node is treated as the center node within a
// star-graph. This method may be used to kick off a path finding algorithm in
// order to explore the reachability of another node based off the source node.
func (c *ChannelGraph) sourceNode(nodes kvdb.RBucket) (*models.LightningNode,
        error) {

        selfPub := nodes.Get(sourceKey)
        if selfPub == nil {
                return nil, ErrSourceNodeNotSet
        }

        // With the pubKey of the source node retrieved, we're able to
        // fetch the full node information.
        node, err := fetchLightningNode(nodes, selfPub)
        if err != nil {
                return nil, err
        }

        return &node, nil
}

// SetSourceNode sets the source node within the graph database. The source
// node is to be used as the center of a star-graph within path finding
// algorithms.
func (c *ChannelGraph) SetSourceNode(node *models.LightningNode) error {
        nodePubBytes := node.PubKeyBytes[:]

        return kvdb.Update(c.db, func(tx kvdb.RwTx) error {
                // First grab the nodes bucket which stores the mapping from
                // pubKey to node information.
                nodes, err := tx.CreateTopLevelBucket(nodeBucket)
                if err != nil {
                        return err
                }

                // Next we create the mapping from source to the targeted
                // public key.
                if err := nodes.Put(sourceKey, nodePubBytes); err != nil {
                        return err
                }

                // Finally, we commit the information of the lightning node
                // itself.
                return addLightningNode(tx, node)
        }, func() {})
}

// AddLightningNode adds a vertex/node to the graph database. If the node is not
// in the database from before, this will add a new, unconnected one to the
// graph. If it is present from before, this will update that node's
// information. Note that this method is expected to only be called to update an
// already present node from a node announcement, or to insert a node found in a
// channel update.
//
// TODO(roasbeef): also need sig of announcement
func (c *ChannelGraph) AddLightningNode(node *models.LightningNode,
        op ...batch.SchedulerOption) error {

        r := &batch.Request{
                Update: func(tx kvdb.RwTx) error {
                        if c.graphCache != nil {
                                cNode := newGraphCacheNode(
                                        node.PubKeyBytes, node.Features,
                                )
                                err := c.graphCache.AddNode(tx, cNode)
                                if err != nil {
                                        return err
                                }
                        }

                        return addLightningNode(tx, node)
                },
        }

        for _, f := range op {
                f(r)
        }

        return c.nodeScheduler.Execute(r)
}

func addLightningNode(tx kvdb.RwTx, node *models.LightningNode) error {
        nodes, err := tx.CreateTopLevelBucket(nodeBucket)
        if err != nil {
                return err
        }

        aliases, err := nodes.CreateBucketIfNotExists(aliasIndexBucket)
        if err != nil {
                return err
        }

        updateIndex, err := nodes.CreateBucketIfNotExists(
                nodeUpdateIndexBucket,
        )
        if err != nil {
                return err
        }

        return putLightningNode(nodes, aliases, updateIndex, node)
}

// LookupAlias attempts to return the alias as advertised by the target node.
// TODO(roasbeef): currently assumes that aliases are unique...
func (c *ChannelGraph) LookupAlias(pub *btcec.PublicKey) (string, error) {
        var alias string

        err := kvdb.View(c.db, func(tx kvdb.RTx) error {
                nodes := tx.ReadBucket(nodeBucket)
                if nodes == nil {
                        return ErrGraphNodesNotFound
                }

                aliases := nodes.NestedReadBucket(aliasIndexBucket)
                if aliases == nil {
                        return ErrGraphNodesNotFound
                }

                nodePub := pub.SerializeCompressed()
                a := aliases.Get(nodePub)
                if a == nil {
                        return ErrNodeAliasNotFound
                }

                // TODO(roasbeef): should actually be using the utf-8
                // package...
                alias = string(a)
                return nil
        }, func() {
                alias = ""
        })
        if err != nil {
                return "", err
        }

        return alias, nil
}

// DeleteLightningNode starts a new database transaction to remove a vertex/node
// from the database according to the node's public key.
func (c *ChannelGraph) DeleteLightningNode(nodePub route.Vertex) error {
        // TODO(roasbeef): ensure dangling edges are removed...
        return kvdb.Update(c.db, func(tx kvdb.RwTx) error {
                nodes := tx.ReadWriteBucket(nodeBucket)
                if nodes == nil {
                        return ErrGraphNodeNotFound
                }

                if c.graphCache != nil {
                        c.graphCache.RemoveNode(nodePub)
                }

                return c.deleteLightningNode(nodes, nodePub[:])
        }, func() {})
}

// deleteLightningNode uses an existing database transaction to remove a
// vertex/node from the database according to the node's public key.
func (c *ChannelGraph) deleteLightningNode(nodes kvdb.RwBucket,
        compressedPubKey []byte) error {

        aliases := nodes.NestedReadWriteBucket(aliasIndexBucket)
        if aliases == nil {
                return ErrGraphNodesNotFound
        }

        if err := aliases.Delete(compressedPubKey); err != nil {
                return err
        }

        // Before we delete the node, we'll fetch its current state so we can
        // determine when its last update was to clear out the node update
        // index.
        node, err := fetchLightningNode(nodes, compressedPubKey)
        if err != nil {
                return err
        }

        if err := nodes.Delete(compressedPubKey); err != nil {
                return err
        }

        // Finally, we'll delete the index entry for the node within the
        // nodeUpdateIndexBucket as this node is no longer active, so we don't
        // need to track its last update.
        nodeUpdateIndex := nodes.NestedReadWriteBucket(nodeUpdateIndexBucket)
        if nodeUpdateIndex == nil {
                return ErrGraphNodesNotFound
        }

        // In order to delete the entry, we'll need to reconstruct the key for
        // its last update.
        updateUnix := uint64(node.LastUpdate.Unix())
        var indexKey [8 + 33]byte
        byteOrder.PutUint64(indexKey[:8], updateUnix)
        copy(indexKey[8:], compressedPubKey)

        return nodeUpdateIndex.Delete(indexKey[:])
}

// AddChannelEdge adds a new (undirected, blank) edge to the graph database. An
// undirected edge from the two target nodes are created. The information stored
// denotes the static attributes of the channel, such as the channelID, the keys
// involved in creation of the channel, and the set of features that the channel
// supports. The chanPoint and chanID are used to uniquely identify the edge
// globally within the database.
func (c *ChannelGraph) AddChannelEdge(edge *models.ChannelEdgeInfo,
        op ...batch.SchedulerOption) error {

        var alreadyExists bool
        r := &batch.Request{
                Reset: func() {
                        alreadyExists = false
                },
                Update: func(tx kvdb.RwTx) error {
                        err := c.addChannelEdge(tx, edge)

                        // Silence ErrEdgeAlreadyExist so that the batch can
                        // succeed, but propagate the error via local state.
                        if err == ErrEdgeAlreadyExist {
                                alreadyExists = true
                                return nil
                        }

                        return err
                },
                OnCommit: func(err error) error {
                        switch {
                        case err != nil:
                                return err
                        case alreadyExists:
                                return ErrEdgeAlreadyExist
                        default:
                                c.rejectCache.remove(edge.ChannelID)
                                c.chanCache.remove(edge.ChannelID)
                                return nil
                        }
                },
        }

        for _, f := range op {
                if f == nil {
                        return fmt.Errorf("nil scheduler option was used")
                }

                f(r)
        }

        return c.chanScheduler.Execute(r)
}

// addChannelEdge is the private form of AddChannelEdge that allows callers to
// utilize an existing db transaction.
func (c *ChannelGraph) addChannelEdge(tx kvdb.RwTx,
        edge *models.ChannelEdgeInfo) error {

        // Construct the channel's primary key which is the 8-byte channel ID.
        var chanKey [8]byte
        binary.BigEndian.PutUint64(chanKey[:], edge.ChannelID)

        nodes, err := tx.CreateTopLevelBucket(nodeBucket)
        if err != nil {
                return err
        }
        edges, err := tx.CreateTopLevelBucket(edgeBucket)
        if err != nil {
                return err
        }
        edgeIndex, err := edges.CreateBucketIfNotExists(edgeIndexBucket)
        if err != nil {
                return err
        }
        chanIndex, err := edges.CreateBucketIfNotExists(channelPointBucket)
        if err != nil {
                return err
        }

        // First, attempt to check if this edge has already been created. If
        // so, then we can exit early as this method is meant to be idempotent.
        if edgeInfo := edgeIndex.Get(chanKey[:]); edgeInfo != nil {
                return ErrEdgeAlreadyExist
        }

        if c.graphCache != nil {
                c.graphCache.AddChannel(edge, nil, nil)
        }

        // Before we insert the channel into the database, we'll ensure that
        // both nodes already exist in the channel graph. If either node
        // doesn't, then we'll insert a "shell" node that just includes its
        // public key, so subsequent validation and queries can work properly.
        _, node1Err := fetchLightningNode(nodes, edge.NodeKey1Bytes[:])
        switch {
        case node1Err == ErrGraphNodeNotFound:
                node1Shell := models.LightningNode{
                        PubKeyBytes:          edge.NodeKey1Bytes,
                        HaveNodeAnnouncement: false,
                }
                err := addLightningNode(tx, &node1Shell)
                if err != nil {
                        return fmt.Errorf("unable to create shell node "+
                                "for: %x", edge.NodeKey1Bytes)
                }
        case node1Err != nil:
                return err
        }

        _, node2Err := fetchLightningNode(nodes, edge.NodeKey2Bytes[:])
        switch {
        case node2Err == ErrGraphNodeNotFound:
                node2Shell := models.LightningNode{
                        PubKeyBytes:          edge.NodeKey2Bytes,
                        HaveNodeAnnouncement: false,
                }
                err := addLightningNode(tx, &node2Shell)
                if err != nil {
                        return fmt.Errorf("unable to create shell node "+
                                "for: %x", edge.NodeKey2Bytes)
                }
        case node2Err != nil:
                return err
        }

        // If the edge hasn't been created yet, then we'll first add it to the
        // edge index in order to associate the edge between two nodes and also
        // store the static components of the channel.
        if err := putChanEdgeInfo(edgeIndex, edge, chanKey); err != nil {
                return err
        }

        // Mark edge policies for both sides as unknown. This is to enable
        // efficient incoming channel lookup for a node.
        keys := []*[33]byte{
                &edge.NodeKey1Bytes,
                &edge.NodeKey2Bytes,
        }
        for _, key := range keys {
                err := putChanEdgePolicyUnknown(edges, edge.ChannelID, key[:])
                if err != nil {
                        return err
                }
        }

        // Finally we add it to the channel index which maps channel points
        // (outpoints) to the shorter channel ID's.
        var b bytes.Buffer
        if err := WriteOutpoint(&b, &edge.ChannelPoint); err != nil {
                return err
        }
        return chanIndex.Put(b.Bytes(), chanKey[:])
}

// ReAddChannelEdge removes the edge with the given channel ID from the
// database and adds the new edge to guarantee atomicity.
// This is important for option-scid-alias channel which might over the course
// of their lifetime change their SCID (e.g. public zero-conf channels).
func (c *ChannelGraph) ReAddChannelEdge(
        chanID uint64, newEdge *models.ChannelEdgeInfo,
        ourPolicy *models.ChannelEdgePolicy) error {

        c.cacheMu.Lock()
        defer c.cacheMu.Unlock()

        err := kvdb.Update(c.db, func(tx kvdb.RwTx) error {
                edges := tx.ReadWriteBucket(edgeBucket)
                if edges == nil {
                        return ErrEdgeNotFound
                }
                edgeIndex := edges.NestedReadWriteBucket(edgeIndexBucket)
                if edgeIndex == nil {
                        return ErrEdgeNotFound
                }
                chanIndex := edges.NestedReadWriteBucket(channelPointBucket)
                if chanIndex == nil {
                        return ErrEdgeNotFound
                }
                nodes := tx.ReadWriteBucket(nodeBucket)
                if nodes == nil {
                        return ErrGraphNodeNotFound
                }

                var rawChanID [8]byte
                byteOrder.PutUint64(rawChanID[:], chanID)

                // We don't mark this channel as zombie, because we are readding
                // it immediately after deleting it below. This method also
                // deletes the channel from the graph cache, however there is
                // no entry in the cache because we only add it if we have
                // received the proof(signatures).
                err := c.delChannelEdgeUnsafe(
                        edges, edgeIndex, chanIndex, nil,
                        rawChanID[:], false, false,
                )
                if err != nil {
                        return err
                }

                // Now we add the channel with the new edge info.
                err = c.addChannelEdge(tx, newEdge)
                if err != nil {
                        return err
                }

                // Also add the new channel update from our side.
                _, err = updateEdgePolicy(tx, ourPolicy, c.graphCache)

                return err
        }, func() {})
        if err != nil {
                return err
        }

        // Remove the Cache entries.
        c.rejectCache.remove(chanID)
        c.chanCache.remove(chanID)

        return nil
}

// HasChannelEdge returns true if the database knows of a channel edge with the
// passed channel ID, and false otherwise. If an edge with that ID is found
// within the graph, then two time stamps representing the last time the edge
// was updated for both directed edges are returned along with the boolean. If
// it is not found, then the zombie index is checked and its result is returned
// as the second boolean.
func (c *ChannelGraph) HasChannelEdge(
        chanID uint64) (time.Time, time.Time, bool, bool, error) {

        var (
                upd1Time time.Time
                upd2Time time.Time
                exists   bool
                isZombie bool
        )

        // We'll query the cache with the shared lock held to allow multiple
        // readers to access values in the cache concurrently if they exist.
        c.cacheMu.RLock()
        if entry, ok := c.rejectCache.get(chanID); ok {
                c.cacheMu.RUnlock()
                upd1Time = time.Unix(entry.upd1Time, 0)
                upd2Time = time.Unix(entry.upd2Time, 0)
                exists, isZombie = entry.flags.unpack()
                return upd1Time, upd2Time, exists, isZombie, nil
        }
        c.cacheMu.RUnlock()

        c.cacheMu.Lock()
        defer c.cacheMu.Unlock()

        // The item was not found with the shared lock, so we'll acquire the
        // exclusive lock and check the cache again in case another method added
        // the entry to the cache while no lock was held.
        if entry, ok := c.rejectCache.get(chanID); ok {
                upd1Time = time.Unix(entry.upd1Time, 0)
                upd2Time = time.Unix(entry.upd2Time, 0)
                exists, isZombie = entry.flags.unpack()
                return upd1Time, upd2Time, exists, isZombie, nil
        }

        if err := kvdb.View(c.db, func(tx kvdb.RTx) error {
                edges := tx.ReadBucket(edgeBucket)
                if edges == nil {
                        return ErrGraphNoEdgesFound
                }
                edgeIndex := edges.NestedReadBucket(edgeIndexBucket)
                if edgeIndex == nil {
                        return ErrGraphNoEdgesFound
                }

                var channelID [8]byte
                byteOrder.PutUint64(channelID[:], chanID)

                // If the edge doesn't exist, then we'll also check our zombie
                // index.
                if edgeIndex.Get(channelID[:]) == nil {
                        exists = false
                        zombieIndex := edges.NestedReadBucket(zombieBucket)
                        if zombieIndex != nil {
                                isZombie, _, _ = isZombieEdge(
                                        zombieIndex, chanID,
                                )
                        }

                        return nil
                }

                exists = true
                isZombie = false

                // If the channel has been found in the graph, then retrieve
                // the edges itself so we can return the last updated
                // timestamps.
                nodes := tx.ReadBucket(nodeBucket)
                if nodes == nil {
                        return ErrGraphNodeNotFound
                }

                e1, e2, err := fetchChanEdgePolicies(
                        edgeIndex, edges, channelID[:],
                )
                if err != nil {
                        return err
                }

                // As we may have only one of the edges populated, only set the
                // update time if the edge was found in the database.
                if e1 != nil {
                        upd1Time = e1.LastUpdate
                }
                if e2 != nil {
                        upd2Time = e2.LastUpdate
                }

                return nil
        }, func() {}); err != nil {
                return time.Time{}, time.Time{}, exists, isZombie, err
        }

        c.rejectCache.insert(chanID, rejectCacheEntry{
                upd1Time: upd1Time.Unix(),
                upd2Time: upd2Time.Unix(),
                flags:    packRejectFlags(exists, isZombie),
        })

        return upd1Time, upd2Time, exists, isZombie, nil
}

// UpdateChannelEdge retrieves and update edge of the graph database. Method
// only reserved for updating an edge info after its already been created.
// In order to maintain this constraints, we return an error in the scenario
// that an edge info hasn't yet been created yet, but someone attempts to update
// it.
func (c *ChannelGraph) UpdateChannelEdge(edge *models.ChannelEdgeInfo) error {
        // Construct the channel's primary key which is the 8-byte channel ID.
        var chanKey [8]byte
        binary.BigEndian.PutUint64(chanKey[:], edge.ChannelID)

        return kvdb.Update(c.db, func(tx kvdb.RwTx) error {
                edges := tx.ReadWriteBucket(edgeBucket)
                if edge == nil {
                        return ErrEdgeNotFound
                }

                edgeIndex := edges.NestedReadWriteBucket(edgeIndexBucket)
                if edgeIndex == nil {
                        return ErrEdgeNotFound
                }

                if edgeInfo := edgeIndex.Get(chanKey[:]); edgeInfo == nil {
                        return ErrEdgeNotFound
                }

                if c.graphCache != nil {
                        c.graphCache.UpdateChannel(edge)
                }

                return putChanEdgeInfo(edgeIndex, edge, chanKey)
        }, func() {})
}

const (
        // pruneTipBytes is the total size of the value which stores a prune
        // entry of the graph in the prune log. The "prune tip" is the last
        // entry in the prune log, and indicates if the channel graph is in
        // sync with the current UTXO state. The structure of the value
        // is: blockHash, taking 32 bytes total.
        pruneTipBytes = 32
)

// PruneGraph prunes newly closed channels from the channel graph in response
// to a new block being solved on the network. Any transactions which spend the
// funding output of any known channels within he graph will be deleted.
// Additionally, the "prune tip", or the last block which has been used to
// prune the graph is stored so callers can ensure the graph is fully in sync
// with the current UTXO state. A slice of channels that have been closed by
// the target block are returned if the function succeeds without error.
func (c *ChannelGraph) PruneGraph(spentOutputs []*wire.OutPoint,
        blockHash *chainhash.Hash, blockHeight uint32) (
        []*models.ChannelEdgeInfo, error) {

        c.cacheMu.Lock()
        defer c.cacheMu.Unlock()

        var chansClosed []*models.ChannelEdgeInfo

        err := kvdb.Update(c.db, func(tx kvdb.RwTx) error {
                // First grab the edges bucket which houses the information
                // we'd like to delete
                edges, err := tx.CreateTopLevelBucket(edgeBucket)
                if err != nil {
                        return err
                }

                // Next grab the two edge indexes which will also need to be
                // updated.
                edgeIndex, err := edges.CreateBucketIfNotExists(edgeIndexBucket)
                if err != nil {
                        return err
                }
                chanIndex, err := edges.CreateBucketIfNotExists(
                        channelPointBucket,
                )
                if err != nil {
                        return err
                }
                nodes := tx.ReadWriteBucket(nodeBucket)
                if nodes == nil {
                        return ErrSourceNodeNotSet
                }
                zombieIndex, err := edges.CreateBucketIfNotExists(zombieBucket)
                if err != nil {
                        return err
                }

                // For each of the outpoints that have been spent within the
                // block, we attempt to delete them from the graph as if that
                // outpoint was a channel, then it has now been closed.
                for _, chanPoint := range spentOutputs {
                        // TODO(roasbeef): load channel bloom filter, continue
                        // if NOT if filter

                        var opBytes bytes.Buffer
                        err := WriteOutpoint(&opBytes, chanPoint)
                        if err != nil {
                                return err
                        }

                        // First attempt to see if the channel exists within
                        // the database, if not, then we can exit early.
                        chanID := chanIndex.Get(opBytes.Bytes())
                        if chanID == nil {
                                continue
                        }

                        // However, if it does, then we'll read out the full
                        // version so we can add it to the set of deleted
                        // channels.
                        edgeInfo, err := fetchChanEdgeInfo(edgeIndex, chanID)
                        if err != nil {
                                return err
                        }

                        // Attempt to delete the channel, an ErrEdgeNotFound
                        // will be returned if that outpoint isn't known to be
                        // a channel. If no error is returned, then a channel
                        // was successfully pruned.
                        err = c.delChannelEdgeUnsafe(
                                edges, edgeIndex, chanIndex, zombieIndex,
                                chanID, false, false,
                        )
                        if err != nil && !errors.Is(err, ErrEdgeNotFound) {
                                return err
                        }

                        chansClosed = append(chansClosed, &edgeInfo)
                }

                metaBucket, err := tx.CreateTopLevelBucket(graphMetaBucket)
                if err != nil {
                        return err
                }

                pruneBucket, err := metaBucket.CreateBucketIfNotExists(
                        pruneLogBucket,
                )
                if err != nil {
                        return err
                }

                // With the graph pruned, add a new entry to the prune log,
                // which can be used to check if the graph is fully synced with
                // the current UTXO state.
                var blockHeightBytes [4]byte
                byteOrder.PutUint32(blockHeightBytes[:], blockHeight)

                var newTip [pruneTipBytes]byte
                copy(newTip[:], blockHash[:])

                err = pruneBucket.Put(blockHeightBytes[:], newTip[:])
                if err != nil {
                        return err
                }

                // Now that the graph has been pruned, we'll also attempt to
                // prune any nodes that have had a channel closed within the
                // latest block.
                return c.pruneGraphNodes(nodes, edgeIndex)
        }, func() {
                chansClosed = nil
        })
        if err != nil {
                return nil, err
        }

        for _, channel := range chansClosed {
                c.rejectCache.remove(channel.ChannelID)
                c.chanCache.remove(channel.ChannelID)
        }

        if c.graphCache != nil {
                log.Debugf("Pruned graph, cache now has %s",
                        c.graphCache.Stats())
        }

        return chansClosed, nil
}

// PruneGraphNodes is a garbage collection method which attempts to prune out
// any nodes from the channel graph that are currently unconnected. This ensure
// that we only maintain a graph of reachable nodes. In the event that a pruned
// node gains more channels, it will be re-added back to the graph.
func (c *ChannelGraph) PruneGraphNodes() error {
        return kvdb.Update(c.db, func(tx kvdb.RwTx) error {
                nodes := tx.ReadWriteBucket(nodeBucket)
                if nodes == nil {
                        return ErrGraphNodesNotFound
                }
                edges := tx.ReadWriteBucket(edgeBucket)
                if edges == nil {
                        return ErrGraphNotFound
                }
                edgeIndex := edges.NestedReadWriteBucket(edgeIndexBucket)
                if edgeIndex == nil {
                        return ErrGraphNoEdgesFound
                }

                return c.pruneGraphNodes(nodes, edgeIndex)
        }, func() {})
}

// pruneGraphNodes attempts to remove any nodes from the graph who have had a
// channel closed within the current block. If the node still has existing
// channels in the graph, this will act as a no-op.
func (c *ChannelGraph) pruneGraphNodes(nodes kvdb.RwBucket,
        edgeIndex kvdb.RwBucket) error {

        log.Trace("Pruning nodes from graph with no open channels")

        // We'll retrieve the graph's source node to ensure we don't remove it
        // even if it no longer has any open channels.
        sourceNode, err := c.sourceNode(nodes)
        if err != nil {
                return err
        }

        // We'll use this map to keep count the number of references to a node
        // in the graph. A node should only be removed once it has no more
        // references in the graph.
        nodeRefCounts := make(map[[33]byte]int)
        err = nodes.ForEach(func(pubKey, nodeBytes []byte) error {
                // If this is the source key, then we skip this
                // iteration as the value for this key is a pubKey
                // rather than raw node information.
                if bytes.Equal(pubKey, sourceKey) || len(pubKey) != 33 {
                        return nil
                }

                var nodePub [33]byte
                copy(nodePub[:], pubKey)
                nodeRefCounts[nodePub] = 0

                return nil
        })
        if err != nil {
                return err
        }

        // To ensure we never delete the source node, we'll start off by
        // bumping its ref count to 1.
        nodeRefCounts[sourceNode.PubKeyBytes] = 1

        // Next, we'll run through the edgeIndex which maps a channel ID to the
        // edge info. We'll use this scan to populate our reference count map
        // above.
        err = edgeIndex.ForEach(func(chanID, edgeInfoBytes []byte) error {
                // The first 66 bytes of the edge info contain the pubkeys of
                // the nodes that this edge attaches. We'll extract them, and
                // add them to the ref count map.
                var node1, node2 [33]byte
                copy(node1[:], edgeInfoBytes[:33])
                copy(node2[:], edgeInfoBytes[33:])

                // With the nodes extracted, we'll increase the ref count of
                // each of the nodes.
                nodeRefCounts[node1]++
                nodeRefCounts[node2]++

                return nil
        })
        if err != nil {
                return err
        }

        // Finally, we'll make a second pass over the set of nodes, and delete
        // any nodes that have a ref count of zero.
        var numNodesPruned int
        for nodePubKey, refCount := range nodeRefCounts {
                // If the ref count of the node isn't zero, then we can safely
                // skip it as it still has edges to or from it within the
                // graph.
                if refCount != 0 {
                        continue
                }

                if c.graphCache != nil {
                        c.graphCache.RemoveNode(nodePubKey)
                }

                // If we reach this point, then there are no longer any edges
                // that connect this node, so we can delete it.
                err := c.deleteLightningNode(nodes, nodePubKey[:])
                if err != nil {
                        if errors.Is(err, ErrGraphNodeNotFound) ||
                                errors.Is(err, ErrGraphNodesNotFound) {

                                log.Warnf("Unable to prune node %x from the "+
                                        "graph: %v", nodePubKey, err)
                                continue
                        }

                        return err
                }

                log.Infof("Pruned unconnected node %x from channel graph",
                        nodePubKey[:])

                numNodesPruned++
        }

        if numNodesPruned > 0 {
                log.Infof("Pruned %v unconnected nodes from the channel graph",
                        numNodesPruned)
        }

        return nil
}

// DisconnectBlockAtHeight is used to indicate that the block specified
// by the passed height has been disconnected from the main chain. This
// will "rewind" the graph back to the height below, deleting channels
// that are no longer confirmed from the graph. The prune log will be
// set to the last prune height valid for the remaining chain.
// Channels that were removed from the graph resulting from the
// disconnected block are returned.
func (c *ChannelGraph) DisconnectBlockAtHeight(height uint32) (
        []*models.ChannelEdgeInfo, error) {

        // Every channel having a ShortChannelID starting at 'height'
        // will no longer be confirmed.
        startShortChanID := lnwire.ShortChannelID{
                BlockHeight: height,
        }

        // Delete everything after this height from the db up until the
        // SCID alias range.
        endShortChanID := aliasmgr.StartingAlias

        // The block height will be the 3 first bytes of the channel IDs.
        var chanIDStart [8]byte
        byteOrder.PutUint64(chanIDStart[:], startShortChanID.ToUint64())
        var chanIDEnd [8]byte
        byteOrder.PutUint64(chanIDEnd[:], endShortChanID.ToUint64())

        c.cacheMu.Lock()
        defer c.cacheMu.Unlock()

        // Keep track of the channels that are removed from the graph.
        var removedChans []*models.ChannelEdgeInfo

        if err := kvdb.Update(c.db, func(tx kvdb.RwTx) error {
                edges, err := tx.CreateTopLevelBucket(edgeBucket)
                if err != nil {
                        return err
                }
                edgeIndex, err := edges.CreateBucketIfNotExists(edgeIndexBucket)
                if err != nil {
                        return err
                }
                chanIndex, err := edges.CreateBucketIfNotExists(
                        channelPointBucket,
                )
                if err != nil {
                        return err
                }
                zombieIndex, err := edges.CreateBucketIfNotExists(zombieBucket)
                if err != nil {
                        return err
                }

                // Scan from chanIDStart to chanIDEnd, deleting every
                // found edge.
                // NOTE: we must delete the edges after the cursor loop, since
                // modifying the bucket while traversing is not safe.
                // NOTE: We use a < comparison in bytes.Compare instead of <=
                // so that the StartingAlias itself isn't deleted.
                var keys [][]byte
                cursor := edgeIndex.ReadWriteCursor()

                //nolint:ll
                for k, v := cursor.Seek(chanIDStart[:]); k != nil &&
                        bytes.Compare(k, chanIDEnd[:]) < 0; k, v = cursor.Next() {
                        edgeInfoReader := bytes.NewReader(v)
                        edgeInfo, err := deserializeChanEdgeInfo(edgeInfoReader)
                        if err != nil {
                                return err
                        }

                        keys = append(keys, k)
                        removedChans = append(removedChans, &edgeInfo)
                }

                for _, k := range keys {
                        err = c.delChannelEdgeUnsafe(
                                edges, edgeIndex, chanIndex, zombieIndex,
                                k, false, false,
                        )
                        if err != nil && !errors.Is(err, ErrEdgeNotFound) {
                                return err
                        }
                }

                // Delete all the entries in the prune log having a height
                // greater or equal to the block disconnected.
                metaBucket, err := tx.CreateTopLevelBucket(graphMetaBucket)
                if err != nil {
                        return err
                }

                pruneBucket, err := metaBucket.CreateBucketIfNotExists(
                        pruneLogBucket,
                )
                if err != nil {
                        return err
                }

                var pruneKeyStart [4]byte
                byteOrder.PutUint32(pruneKeyStart[:], height)

                var pruneKeyEnd [4]byte
                byteOrder.PutUint32(pruneKeyEnd[:], math.MaxUint32)

                // To avoid modifying the bucket while traversing, we delete
                // the keys in a second loop.
                var pruneKeys [][]byte
                pruneCursor := pruneBucket.ReadWriteCursor()
                //nolint:ll
                for k, _ := pruneCursor.Seek(pruneKeyStart[:]); k != nil &&
                        bytes.Compare(k, pruneKeyEnd[:]) <= 0; k, _ = pruneCursor.Next() {
                        pruneKeys = append(pruneKeys, k)
                }

                for _, k := range pruneKeys {
                        if err := pruneBucket.Delete(k); err != nil {
                                return err
                        }
                }

                return nil
        }, func() {
                removedChans = nil
        }); err != nil {
                return nil, err
        }

        for _, channel := range removedChans {
                c.rejectCache.remove(channel.ChannelID)
                c.chanCache.remove(channel.ChannelID)
        }

        return removedChans, nil
}

// PruneTip returns the block height and hash of the latest block that has been
// used to prune channels in the graph. Knowing the "prune tip" allows callers
// to tell if the graph is currently in sync with the current best known UTXO
// state.
func (c *ChannelGraph) PruneTip() (*chainhash.Hash, uint32, error) {
        var (
                tipHash   chainhash.Hash
                tipHeight uint32
        )

        err := kvdb.View(c.db, func(tx kvdb.RTx) error {
                graphMeta := tx.ReadBucket(graphMetaBucket)
                if graphMeta == nil {
                        return ErrGraphNotFound
                }
                pruneBucket := graphMeta.NestedReadBucket(pruneLogBucket)
                if pruneBucket == nil {
                        return ErrGraphNeverPruned
                }

                pruneCursor := pruneBucket.ReadCursor()

                // The prune key with the largest block height will be our
                // prune tip.
                k, v := pruneCursor.Last()
                if k == nil {
                        return ErrGraphNeverPruned
                }

                // Once we have the prune tip, the value will be the block hash,
                // and the key the block height.
                copy(tipHash[:], v[:])
                tipHeight = byteOrder.Uint32(k[:])

                return nil
        }, func() {})
        if err != nil {
                return nil, 0, err
        }

        return &tipHash, tipHeight, nil
}

// DeleteChannelEdges removes edges with the given channel IDs from the
// database and marks them as zombies. This ensures that we're unable to re-add
// it to our database once again. If an edge does not exist within the
// database, then ErrEdgeNotFound will be returned. If strictZombiePruning is
// true, then when we mark these edges as zombies, we'll set up the keys such
// that we require the node that failed to send the fresh update to be the one
// that resurrects the channel from its zombie state. The markZombie bool
// denotes whether or not to mark the channel as a zombie.
func (c *ChannelGraph) DeleteChannelEdges(strictZombiePruning, markZombie bool,
        chanIDs ...uint64) error {

        // TODO(roasbeef): possibly delete from node bucket if node has no more
        // channels
        // TODO(roasbeef): don't delete both edges?

        c.cacheMu.Lock()
        defer c.cacheMu.Unlock()

        err := kvdb.Update(c.db, func(tx kvdb.RwTx) error {
                edges := tx.ReadWriteBucket(edgeBucket)
                if edges == nil {
                        return ErrEdgeNotFound
                }
                edgeIndex := edges.NestedReadWriteBucket(edgeIndexBucket)
                if edgeIndex == nil {
                        return ErrEdgeNotFound
                }
                chanIndex := edges.NestedReadWriteBucket(channelPointBucket)
                if chanIndex == nil {
                        return ErrEdgeNotFound
                }
                nodes := tx.ReadWriteBucket(nodeBucket)
                if nodes == nil {
                        return ErrGraphNodeNotFound
                }
                zombieIndex, err := edges.CreateBucketIfNotExists(zombieBucket)
                if err != nil {
                        return err
                }

                var rawChanID [8]byte
                for _, chanID := range chanIDs {
                        byteOrder.PutUint64(rawChanID[:], chanID)
                        err := c.delChannelEdgeUnsafe(
                                edges, edgeIndex, chanIndex, zombieIndex,
                                rawChanID[:], markZombie, strictZombiePruning,
                        )
                        if err != nil {
                                return err
                        }
                }

                return nil
        }, func() {})
        if err != nil {
                return err
        }

        for _, chanID := range chanIDs {
                c.rejectCache.remove(chanID)
                c.chanCache.remove(chanID)
        }

        return nil
}

// ChannelID attempt to lookup the 8-byte compact channel ID which maps to the
// passed channel point (outpoint). If the passed channel doesn't exist within
// the database, then ErrEdgeNotFound is returned.
func (c *ChannelGraph) ChannelID(chanPoint *wire.OutPoint) (uint64, error) {
        var chanID uint64
        if err := kvdb.View(c.db, func(tx kvdb.RTx) error {
                var err error
                chanID, err = getChanID(tx, chanPoint)
                return err
        }, func() {
                chanID = 0
        }); err != nil {
                return 0, err
        }

        return chanID, nil
}

// getChanID returns the assigned channel ID for a given channel point.
func getChanID(tx kvdb.RTx, chanPoint *wire.OutPoint) (uint64, error) {
        var b bytes.Buffer
        if err := WriteOutpoint(&b, chanPoint); err != nil {
                return 0, err
        }

        edges := tx.ReadBucket(edgeBucket)
        if edges == nil {
                return 0, ErrGraphNoEdgesFound
        }
        chanIndex := edges.NestedReadBucket(channelPointBucket)
        if chanIndex == nil {
                return 0, ErrGraphNoEdgesFound
        }

        chanIDBytes := chanIndex.Get(b.Bytes())
        if chanIDBytes == nil {
                return 0, ErrEdgeNotFound
        }

        chanID := byteOrder.Uint64(chanIDBytes)

        return chanID, nil
}

// TODO(roasbeef): allow updates to use Batch?

// HighestChanID returns the "highest" known channel ID in the channel graph.
// This represents the "newest" channel from the PoV of the chain. This method
// can be used by peers to quickly determine if they're graphs are in sync.
func (c *ChannelGraph) HighestChanID() (uint64, error) {
        var cid uint64

        err := kvdb.View(c.db, func(tx kvdb.RTx) error {
                edges := tx.ReadBucket(edgeBucket)
                if edges == nil {
                        return ErrGraphNoEdgesFound
                }
                edgeIndex := edges.NestedReadBucket(edgeIndexBucket)
                if edgeIndex == nil {
                        return ErrGraphNoEdgesFound
                }

                // In order to find the highest chan ID, we'll fetch a cursor
                // and use that to seek to the "end" of our known rage.
                cidCursor := edgeIndex.ReadCursor()

                lastChanID, _ := cidCursor.Last()

                // If there's no key, then this means that we don't actually
                // know of any channels, so we'll return a predicable error.
                if lastChanID == nil {
                        return ErrGraphNoEdgesFound
                }

                // Otherwise, we'll de serialize the channel ID and return it
                // to the caller.
                cid = byteOrder.Uint64(lastChanID)
                return nil
        }, func() {
                cid = 0
        })
        if err != nil && err != ErrGraphNoEdgesFound {
                return 0, err
        }

        return cid, nil
}

// ChannelEdge represents the complete set of information for a channel edge in
// the known channel graph. This struct couples the core information of the
// edge as well as each of the known advertised edge policies.
type ChannelEdge struct {
        // Info contains all the static information describing the channel.
        Info *models.ChannelEdgeInfo

        // Policy1 points to the "first" edge policy of the channel containing
        // the dynamic information required to properly route through the edge.
        Policy1 *models.ChannelEdgePolicy

        // Policy2 points to the "second" edge policy of the channel containing
        // the dynamic information required to properly route through the edge.
        Policy2 *models.ChannelEdgePolicy

        // Node1 is "node 1" in the channel. This is the node that would have
        // produced Policy1 if it exists.
        Node1 *models.LightningNode

        // Node2 is "node 2" in the channel. This is the node that would have
        // produced Policy2 if it exists.
        Node2 *models.LightningNode
}

// ChanUpdatesInHorizon returns all the known channel edges which have at least
// one edge that has an update timestamp within the specified horizon.
func (c *ChannelGraph) ChanUpdatesInHorizon(startTime,
        endTime time.Time) ([]ChannelEdge, error) {

        // To ensure we don't return duplicate ChannelEdges, we'll use an
        // additional map to keep track of the edges already seen to prevent
        // re-adding it.
        var edgesSeen map[uint64]struct{}
        var edgesToCache map[uint64]ChannelEdge
        var edgesInHorizon []ChannelEdge

        c.cacheMu.Lock()
        defer c.cacheMu.Unlock()

        var hits int
        err := kvdb.View(c.db, func(tx kvdb.RTx) error {
                edges := tx.ReadBucket(edgeBucket)
                if edges == nil {
                        return ErrGraphNoEdgesFound
                }
                edgeIndex := edges.NestedReadBucket(edgeIndexBucket)
                if edgeIndex == nil {
                        return ErrGraphNoEdgesFound
                }
                edgeUpdateIndex := edges.NestedReadBucket(edgeUpdateIndexBucket)
                if edgeUpdateIndex == nil {
                        return ErrGraphNoEdgesFound
                }

                nodes := tx.ReadBucket(nodeBucket)
                if nodes == nil {
                        return ErrGraphNodesNotFound
                }

                // We'll now obtain a cursor to perform a range query within
                // the index to find all channels within the horizon.
                updateCursor := edgeUpdateIndex.ReadCursor()

                var startTimeBytes, endTimeBytes [8 + 8]byte
                byteOrder.PutUint64(
                        startTimeBytes[:8], uint64(startTime.Unix()),
                )
                byteOrder.PutUint64(
                        endTimeBytes[:8], uint64(endTime.Unix()),
                )

                // With our start and end times constructed, we'll step through
                // the index collecting the info and policy of each update of
                // each channel that has a last update within the time range.
                //
                //nolint:ll
                for indexKey, _ := updateCursor.Seek(startTimeBytes[:]); indexKey != nil &&
                        bytes.Compare(indexKey, endTimeBytes[:]) <= 0; indexKey, _ = updateCursor.Next() {

                        // We have a new eligible entry, so we'll slice of the
                        // chan ID so we can query it in the DB.
                        chanID := indexKey[8:]

                        // If we've already retrieved the info and policies for
                        // this edge, then we can skip it as we don't need to do
                        // so again.
                        chanIDInt := byteOrder.Uint64(chanID)
                        if _, ok := edgesSeen[chanIDInt]; ok {
                                continue
                        }

                        if channel, ok := c.chanCache.get(chanIDInt); ok {
                                hits++
                                edgesSeen[chanIDInt] = struct{}{}
                                edgesInHorizon = append(edgesInHorizon, channel)
                                continue
                        }

                        // First, we'll fetch the static edge information.
                        edgeInfo, err := fetchChanEdgeInfo(edgeIndex, chanID)
                        if err != nil {
                                chanID := byteOrder.Uint64(chanID)
                                return fmt.Errorf("unable to fetch info for "+
                                        "edge with chan_id=%v: %v", chanID, err)
                        }

                        // With the static information obtained, we'll now
                        // fetch the dynamic policy info.
                        edge1, edge2, err := fetchChanEdgePolicies(
                                edgeIndex, edges, chanID,
                        )
                        if err != nil {
                                chanID := byteOrder.Uint64(chanID)
                                return fmt.Errorf("unable to fetch policies "+
                                        "for edge with chan_id=%v: %v", chanID,
                                        err)
                        }

                        node1, err := fetchLightningNode(
                                nodes, edgeInfo.NodeKey1Bytes[:],
                        )
                        if err != nil {
                                return err
                        }

                        node2, err := fetchLightningNode(
                                nodes, edgeInfo.NodeKey2Bytes[:],
                        )
                        if err != nil {
                                return err
                        }

                        // Finally, we'll collate this edge with the rest of
                        // edges to be returned.
                        edgesSeen[chanIDInt] = struct{}{}
                        channel := ChannelEdge{
                                Info:    &edgeInfo,
                                Policy1: edge1,
                                Policy2: edge2,
                                Node1:   &node1,
                                Node2:   &node2,
                        }
                        edgesInHorizon = append(edgesInHorizon, channel)
                        edgesToCache[chanIDInt] = channel
                }

                return nil
        }, func() {
                edgesSeen = make(map[uint64]struct{})
                edgesToCache = make(map[uint64]ChannelEdge)
                edgesInHorizon = nil
        })
        switch {
        case err == ErrGraphNoEdgesFound:
                fallthrough
        case err == ErrGraphNodesNotFound:
                break

        case err != nil:
                return nil, err
        }

        // Insert any edges loaded from disk into the cache.
        for chanid, channel := range edgesToCache {
                c.chanCache.insert(chanid, channel)
        }

        log.Debugf("ChanUpdatesInHorizon hit percentage: %f (%d/%d)",
                float64(hits)/float64(len(edgesInHorizon)), hits,
                len(edgesInHorizon))

        return edgesInHorizon, nil
}

// NodeUpdatesInHorizon returns all the known lightning node which have an
// update timestamp within the passed range. This method can be used by two
// nodes to quickly determine if they have the same set of up to date node
// announcements.
func (c *ChannelGraph) NodeUpdatesInHorizon(startTime,
        endTime time.Time) ([]models.LightningNode, error) {

        var nodesInHorizon []models.LightningNode

        err := kvdb.View(c.db, func(tx kvdb.RTx) error {
                nodes := tx.ReadBucket(nodeBucket)
                if nodes == nil {
                        return ErrGraphNodesNotFound
                }

                nodeUpdateIndex := nodes.NestedReadBucket(nodeUpdateIndexBucket)
                if nodeUpdateIndex == nil {
                        return ErrGraphNodesNotFound
                }

                // We'll now obtain a cursor to perform a range query within
                // the index to find all node announcements within the horizon.
                updateCursor := nodeUpdateIndex.ReadCursor()

                var startTimeBytes, endTimeBytes [8 + 33]byte
                byteOrder.PutUint64(
                        startTimeBytes[:8], uint64(startTime.Unix()),
                )
                byteOrder.PutUint64(
                        endTimeBytes[:8], uint64(endTime.Unix()),
                )

                // With our start and end times constructed, we'll step through
                // the index collecting info for each node within the time
                // range.
                //
                //nolint:ll
                for indexKey, _ := updateCursor.Seek(startTimeBytes[:]); indexKey != nil &&
                        bytes.Compare(indexKey, endTimeBytes[:]) <= 0; indexKey, _ = updateCursor.Next() {

                        nodePub := indexKey[8:]
                        node, err := fetchLightningNode(nodes, nodePub)
                        if err != nil {
                                return err
                        }

                        nodesInHorizon = append(nodesInHorizon, node)
                }

                return nil
        }, func() {
                nodesInHorizon = nil
        })
        switch {
        case err == ErrGraphNoEdgesFound:
                fallthrough
        case err == ErrGraphNodesNotFound:
                break

        case err != nil:
                return nil, err
        }

        return nodesInHorizon, nil
}

// FilterKnownChanIDs takes a set of channel IDs and return the subset of chan
// ID's that we don't know and are not known zombies of the passed set. In other
// words, we perform a set difference of our set of chan ID's and the ones
// passed in. This method can be used by callers to determine the set of
// channels another peer knows of that we don't.
func (c *ChannelGraph) FilterKnownChanIDs(chansInfo []ChannelUpdateInfo,
        isZombieChan func(time.Time, time.Time) bool) ([]uint64, error) {

        var newChanIDs []uint64

        c.cacheMu.Lock()
        defer c.cacheMu.Unlock()

        err := kvdb.Update(c.db, func(tx kvdb.RwTx) error {
                edges := tx.ReadBucket(edgeBucket)
                if edges == nil {
                        return ErrGraphNoEdgesFound
                }
                edgeIndex := edges.NestedReadBucket(edgeIndexBucket)
                if edgeIndex == nil {
                        return ErrGraphNoEdgesFound
                }

                // Fetch the zombie index, it may not exist if no edges have
                // ever been marked as zombies. If the index has been
                // initialized, we will use it later to skip known zombie edges.
                zombieIndex := edges.NestedReadBucket(zombieBucket)

                // We'll run through the set of chanIDs and collate only the
                // set of channel that are unable to be found within our db.
                var cidBytes [8]byte
                for _, info := range chansInfo {
                        scid := info.ShortChannelID.ToUint64()
                        byteOrder.PutUint64(cidBytes[:], scid)

                        // If the edge is already known, skip it.
                        if v := edgeIndex.Get(cidBytes[:]); v != nil {
                                continue
                        }

                        // If the edge is a known zombie, skip it.
                        if zombieIndex != nil {
                                isZombie, _, _ := isZombieEdge(
                                        zombieIndex, scid,
                                )

                                // TODO(ziggie): Make sure that for the strict
                                // pruning case we compare the pubkeys and
                                // whether the right timestamp is not older than
                                // the `ChannelPruneExpiry`.
                                //
                                // NOTE: The timestamp data has no verification
                                // attached to it in the `ReplyChannelRange` msg
                                // so we are trusting this data at this point.
                                // However it is not critical because we are
                                // just removing the channel from the db when
                                // the timestamps are more recent. During the
                                // querying of the gossip msg verification
                                // happens as usual.
                                // However we should start punishing peers when
                                // they don't provide us honest data ?
                                isStillZombie := isZombieChan(
                                        info.Node1UpdateTimestamp,
                                        info.Node2UpdateTimestamp,
                                )

                                switch {
                                // If the edge is a known zombie and if we
                                // would still consider it a zombie given the
                                // latest update timestamps, then we skip this
                                // channel.
                                case isZombie && isStillZombie:
                                        continue

                                // Otherwise, if we have marked it as a zombie
                                // but the latest update timestamps could bring
                                // it back from the dead, then we mark it alive,
                                // and we let it be added to the set of IDs to
                                // query our peer for.
                                case isZombie && !isStillZombie:
                                        err := c.markEdgeLiveUnsafe(tx, scid)
                                        if err != nil {
                                                return err
                                        }
                                }
                        }

                        newChanIDs = append(newChanIDs, scid)
                }

                return nil
        }, func() {
                newChanIDs = nil
        })
        switch {
        // If we don't know of any edges yet, then we'll return the entire set
        // of chan IDs specified.
        case err == ErrGraphNoEdgesFound:
                ogChanIDs := make([]uint64, len(chansInfo))
                for i, info := range chansInfo {
                        ogChanIDs[i] = info.ShortChannelID.ToUint64()
                }

                return ogChanIDs, nil

        case err != nil:
                return nil, err
        }

        return newChanIDs, nil
}

// ChannelUpdateInfo couples the SCID of a channel with the timestamps of the
// latest received channel updates for the channel.
type ChannelUpdateInfo struct {
        // ShortChannelID is the SCID identifier of the channel.
        ShortChannelID lnwire.ShortChannelID

        // Node1UpdateTimestamp is the timestamp of the latest received update
        // from the node 1 channel peer. This will be set to zero time if no
        // update has yet been received from this node.
        Node1UpdateTimestamp time.Time

        // Node2UpdateTimestamp is the timestamp of the latest received update
        // from the node 2 channel peer. This will be set to zero time if no
        // update has yet been received from this node.
        Node2UpdateTimestamp time.Time
}

// NewChannelUpdateInfo is a constructor which makes sure we initialize the
// timestamps with zero seconds unix timestamp which equals
// `January 1, 1970, 00:00:00 UTC` in case the value is `time.Time{}`.
func NewChannelUpdateInfo(scid lnwire.ShortChannelID, node1Timestamp,
        node2Timestamp time.Time) ChannelUpdateInfo {

        chanInfo := ChannelUpdateInfo{
                ShortChannelID:       scid,
                Node1UpdateTimestamp: node1Timestamp,
                Node2UpdateTimestamp: node2Timestamp,
        }

        if node1Timestamp.IsZero() {
                chanInfo.Node1UpdateTimestamp = time.Unix(0, 0)
        }

        if node2Timestamp.IsZero() {
                chanInfo.Node2UpdateTimestamp = time.Unix(0, 0)
        }

        return chanInfo
}

// BlockChannelRange represents a range of channels for a given block height.
type BlockChannelRange struct {
        // Height is the height of the block all of the channels below were
        // included in.
        Height uint32

        // Channels is the list of channels identified by their short ID
        // representation known to us that were included in the block height
        // above. The list may include channel update timestamp information if
        // requested.
        Channels []ChannelUpdateInfo
}

// FilterChannelRange returns the channel ID's of all known channels which were
// mined in a block height within the passed range. The channel IDs are grouped
// by their common block height. This method can be used to quickly share with a
// peer the set of channels we know of within a particular range to catch them
// up after a period of time offline. If withTimestamps is true then the
// timestamp info of the latest received channel update messages of the channel
// will be included in the response.
func (c *ChannelGraph) FilterChannelRange(startHeight,
        endHeight uint32, withTimestamps bool) ([]BlockChannelRange, error) {

        startChanID := &lnwire.ShortChannelID{
                BlockHeight: startHeight,
        }

        endChanID := lnwire.ShortChannelID{
                BlockHeight: endHeight,
                TxIndex:     math.MaxUint32 & 0x00ffffff,
                TxPosition:  math.MaxUint16,
        }

        // As we need to perform a range scan, we'll convert the starting and
        // ending height to their corresponding values when encoded using short
        // channel ID's.
        var chanIDStart, chanIDEnd [8]byte
        byteOrder.PutUint64(chanIDStart[:], startChanID.ToUint64())
        byteOrder.PutUint64(chanIDEnd[:], endChanID.ToUint64())

        var channelsPerBlock map[uint32][]ChannelUpdateInfo
        err := kvdb.View(c.db, func(tx kvdb.RTx) error {
                edges := tx.ReadBucket(edgeBucket)
                if edges == nil {
                        return ErrGraphNoEdgesFound
                }
                edgeIndex := edges.NestedReadBucket(edgeIndexBucket)
                if edgeIndex == nil {
                        return ErrGraphNoEdgesFound
                }

                cursor := edgeIndex.ReadCursor()

                // We'll now iterate through the database, and find each
                // channel ID that resides within the specified range.
                //
                //nolint:ll
                for k, v := cursor.Seek(chanIDStart[:]); k != nil &&
                        bytes.Compare(k, chanIDEnd[:]) <= 0; k, v = cursor.Next() {
                        // Don't send alias SCIDs during gossip sync.
                        edgeReader := bytes.NewReader(v)
                        edgeInfo, err := deserializeChanEdgeInfo(edgeReader)
                        if err != nil {
                                return err
                        }

                        if edgeInfo.AuthProof == nil {
                                continue
                        }

                        // This channel ID rests within the target range, so
                        // we'll add it to our returned set.
                        rawCid := byteOrder.Uint64(k)
                        cid := lnwire.NewShortChanIDFromInt(rawCid)

                        chanInfo := NewChannelUpdateInfo(
                                cid, time.Time{}, time.Time{},
                        )

                        if !withTimestamps {
                                channelsPerBlock[cid.BlockHeight] = append(
                                        channelsPerBlock[cid.BlockHeight],
                                        chanInfo,
                                )

                                continue
                        }

                        node1Key, node2Key := computeEdgePolicyKeys(&edgeInfo)

                        rawPolicy := edges.Get(node1Key)
                        if len(rawPolicy) != 0 {
                                r := bytes.NewReader(rawPolicy)

                                edge, err := deserializeChanEdgePolicyRaw(r)
                                if err != nil && !errors.Is(
                                        err, ErrEdgePolicyOptionalFieldNotFound,
                                ) {

                                        return err
                                }

                                chanInfo.Node1UpdateTimestamp = edge.LastUpdate
                        }

                        rawPolicy = edges.Get(node2Key)
                        if len(rawPolicy) != 0 {
                                r := bytes.NewReader(rawPolicy)

                                edge, err := deserializeChanEdgePolicyRaw(r)
                                if err != nil && !errors.Is(
                                        err, ErrEdgePolicyOptionalFieldNotFound,
                                ) {

                                        return err
                                }

                                chanInfo.Node2UpdateTimestamp = edge.LastUpdate
                        }

                        channelsPerBlock[cid.BlockHeight] = append(
                                channelsPerBlock[cid.BlockHeight], chanInfo,
                        )
                }

                return nil
        }, func() {
                channelsPerBlock = make(map[uint32][]ChannelUpdateInfo)
        })

        switch {
        // If we don't know of any channels yet, then there's nothing to
        // filter, so we'll return an empty slice.
        case err == ErrGraphNoEdgesFound || len(channelsPerBlock) == 0:
                return nil, nil

        case err != nil:
                return nil, err
        }

        // Return the channel ranges in ascending block height order.
        blocks := make([]uint32, 0, len(channelsPerBlock))
        for block := range channelsPerBlock {
                blocks = append(blocks, block)
        }
        sort.Slice(blocks, func(i, j int) bool {
                return blocks[i] < blocks[j]
        })

        channelRanges := make([]BlockChannelRange, 0, len(channelsPerBlock))
        for _, block := range blocks {
                channelRanges = append(channelRanges, BlockChannelRange{
                        Height:   block,
                        Channels: channelsPerBlock[block],
                })
        }

        return channelRanges, nil
}

// FetchChanInfos returns the set of channel edges that correspond to the passed
// channel ID's. If an edge is the query is unknown to the database, it will
// skipped and the result will contain only those edges that exist at the time
// of the query. This can be used to respond to peer queries that are seeking to
// fill in gaps in their view of the channel graph.
func (c *ChannelGraph) FetchChanInfos(chanIDs []uint64) ([]ChannelEdge, error) {
        return c.fetchChanInfos(nil, chanIDs)
}

// fetchChanInfos returns the set of channel edges that correspond to the passed
// channel ID's. If an edge is the query is unknown to the database, it will
// skipped and the result will contain only those edges that exist at the time
// of the query. This can be used to respond to peer queries that are seeking to
// fill in gaps in their view of the channel graph.
//
// NOTE: An optional transaction may be provided. If none is provided, then a
// new one will be created.
func (c *ChannelGraph) fetchChanInfos(tx kvdb.RTx, chanIDs []uint64) (
        []ChannelEdge, error) {
        // TODO(roasbeef): sort cids?

        var (
                chanEdges []ChannelEdge
                cidBytes  [8]byte
        )

        fetchChanInfos := func(tx kvdb.RTx) error {
                edges := tx.ReadBucket(edgeBucket)
                if edges == nil {
                        return ErrGraphNoEdgesFound
                }
                edgeIndex := edges.NestedReadBucket(edgeIndexBucket)
                if edgeIndex == nil {
                        return ErrGraphNoEdgesFound
                }
                nodes := tx.ReadBucket(nodeBucket)
                if nodes == nil {
                        return ErrGraphNotFound
                }

                for _, cid := range chanIDs {
                        byteOrder.PutUint64(cidBytes[:], cid)

                        // First, we'll fetch the static edge information. If
                        // the edge is unknown, we will skip the edge and
                        // continue gathering all known edges.
                        edgeInfo, err := fetchChanEdgeInfo(
                                edgeIndex, cidBytes[:],
                        )
                        switch {
                        case errors.Is(err, ErrEdgeNotFound):
                                continue
                        case err != nil:
                                return err
                        }

                        // With the static information obtained, we'll now
                        // fetch the dynamic policy info.
                        edge1, edge2, err := fetchChanEdgePolicies(
                                edgeIndex, edges, cidBytes[:],
                        )
                        if err != nil {
                                return err
                        }

                        node1, err := fetchLightningNode(
                                nodes, edgeInfo.NodeKey1Bytes[:],
                        )
                        if err != nil {
                                return err
                        }

                        node2, err := fetchLightningNode(
                                nodes, edgeInfo.NodeKey2Bytes[:],
                        )
                        if err != nil {
                                return err
                        }

                        chanEdges = append(chanEdges, ChannelEdge{
                                Info:    &edgeInfo,
                                Policy1: edge1,
                                Policy2: edge2,
                                Node1:   &node1,
                                Node2:   &node2,
                        })
                }
                return nil
        }

        if tx == nil {
                err := kvdb.View(c.db, fetchChanInfos, func() {
                        chanEdges = nil
                })
                if err != nil {
                        return nil, err
                }

                return chanEdges, nil
        }

        err := fetchChanInfos(tx)
        if err != nil {
                return nil, err
        }

        return chanEdges, nil
}

func delEdgeUpdateIndexEntry(edgesBucket kvdb.RwBucket, chanID uint64,
        edge1, edge2 *models.ChannelEdgePolicy) error {

        // First, we'll fetch the edge update index bucket which currently
        // stores an entry for the channel we're about to delete.
        updateIndex := edgesBucket.NestedReadWriteBucket(edgeUpdateIndexBucket)
        if updateIndex == nil {
                // No edges in bucket, return early.
                return nil
        }

        // Now that we have the bucket, we'll attempt to construct a template
        // for the index key: updateTime || chanid.
        var indexKey [8 + 8]byte
        byteOrder.PutUint64(indexKey[8:], chanID)

        // With the template constructed, we'll attempt to delete an entry that
        // would have been created by both edges: we'll alternate the update
        // times, as one may had overridden the other.
        if edge1 != nil {
                byteOrder.PutUint64(
                        indexKey[:8], uint64(edge1.LastUpdate.Unix()),
                )
                if err := updateIndex.Delete(indexKey[:]); err != nil {
                        return err
                }
        }

        // We'll also attempt to delete the entry that may have been created by
        // the second edge.
        if edge2 != nil {
                byteOrder.PutUint64(
                        indexKey[:8], uint64(edge2.LastUpdate.Unix()),
                )
                if err := updateIndex.Delete(indexKey[:]); err != nil {
                        return err
                }
        }

        return nil
}

// delChannelEdgeUnsafe deletes the edge with the given chanID from the graph
// cache. It then goes on to delete any policy info and edge info for this
// channel from the DB and finally, if isZombie is true, it will add an entry
// for this channel in the zombie index.
//
// NOTE: this method MUST only be called if the cacheMu has already been
// acquired.
func (c *ChannelGraph) delChannelEdgeUnsafe(edges, edgeIndex, chanIndex,
        zombieIndex kvdb.RwBucket, chanID []byte, isZombie,
        strictZombie bool) error {

        edgeInfo, err := fetchChanEdgeInfo(edgeIndex, chanID)
        if err != nil {
                return err
        }

        if c.graphCache != nil {
                c.graphCache.RemoveChannel(
                        edgeInfo.NodeKey1Bytes, edgeInfo.NodeKey2Bytes,
                        edgeInfo.ChannelID,
                )
        }

        // We'll also remove the entry in the edge update index bucket before
        // we delete the edges themselves so we can access their last update
        // times.
        cid := byteOrder.Uint64(chanID)
        edge1, edge2, err := fetchChanEdgePolicies(edgeIndex, edges, chanID)
        if err != nil {
                return err
        }
        err = delEdgeUpdateIndexEntry(edges, cid, edge1, edge2)
        if err != nil {
                return err
        }

        // The edge key is of the format pubKey || chanID. First we construct
        // the latter half, populating the channel ID.
        var edgeKey [33 + 8]byte
        copy(edgeKey[33:], chanID)

        // With the latter half constructed, copy over the first public key to
        // delete the edge in this direction, then the second to delete the
        // edge in the opposite direction.
        copy(edgeKey[:33], edgeInfo.NodeKey1Bytes[:])
        if edges.Get(edgeKey[:]) != nil {
                if err := edges.Delete(edgeKey[:]); err != nil {
                        return err
                }
        }
        copy(edgeKey[:33], edgeInfo.NodeKey2Bytes[:])
        if edges.Get(edgeKey[:]) != nil {
                if err := edges.Delete(edgeKey[:]); err != nil {
                        return err
                }
        }

        // As part of deleting the edge we also remove all disabled entries
        // from the edgePolicyDisabledIndex bucket. We do that for both
        // directions.
        updateEdgePolicyDisabledIndex(edges, cid, false, false)
        updateEdgePolicyDisabledIndex(edges, cid, true, false)

        // With the edge data deleted, we can purge the information from the two
        // edge indexes.
        if err := edgeIndex.Delete(chanID); err != nil {
                return err
        }
        var b bytes.Buffer
        if err := WriteOutpoint(&b, &edgeInfo.ChannelPoint); err != nil {
                return err
        }
        if err := chanIndex.Delete(b.Bytes()); err != nil {
                return err
        }

        // Finally, we'll mark the edge as a zombie within our index if it's
        // being removed due to the channel becoming a zombie. We do this to
        // ensure we don't store unnecessary data for spent channels.
        if !isZombie {
                return nil
        }

        nodeKey1, nodeKey2 := edgeInfo.NodeKey1Bytes, edgeInfo.NodeKey2Bytes
        if strictZombie {
                nodeKey1, nodeKey2 = makeZombiePubkeys(&edgeInfo, edge1, edge2)
        }

        return markEdgeZombie(
                zombieIndex, byteOrder.Uint64(chanID), nodeKey1, nodeKey2,
        )
}

// makeZombiePubkeys derives the node pubkeys to store in the zombie index for a
// particular pair of channel policies. The return values are one of:
//  1. (pubkey1, pubkey2)
//  2. (pubkey1, blank)
//  3. (blank, pubkey2)
//
// A blank pubkey means that corresponding node will be unable to resurrect a
// channel on its own. For example, node1 may continue to publish recent
// updates, but node2 has fallen way behind. After marking an edge as a zombie,
// we don't want another fresh update from node1 to resurrect, as the edge can
// only become live once node2 finally sends something recent.
//
// In the case where we have neither update, we allow either party to resurrect
// the channel. If the channel were to be marked zombie again, it would be
// marked with the correct lagging channel since we received an update from only
// one side.
func makeZombiePubkeys(info *models.ChannelEdgeInfo,
        e1, e2 *models.ChannelEdgePolicy) ([33]byte, [33]byte) {

        switch {
        // If we don't have either edge policy, we'll return both pubkeys so
        // that the channel can be resurrected by either party.
        case e1 == nil && e2 == nil:
                return info.NodeKey1Bytes, info.NodeKey2Bytes

        // If we're missing edge1, or if both edges are present but edge1 is
        // older, we'll return edge1's pubkey and a blank pubkey for edge2. This
        // means that only an update from edge1 will be able to resurrect the
        // channel.
        case e1 == nil || (e2 != nil && e1.LastUpdate.Before(e2.LastUpdate)):
                return info.NodeKey1Bytes, [33]byte{}

        // Otherwise, we're missing edge2 or edge2 is the older side, so we
        // return a blank pubkey for edge1. In this case, only an update from
        // edge2 can resurect the channel.
        default:
                return [33]byte{}, info.NodeKey2Bytes
        }
}

// UpdateEdgePolicy updates the edge routing policy for a single directed edge
// within the database for the referenced channel. The `flags` attribute within
// the ChannelEdgePolicy determines which of the directed edges are being
// updated. If the flag is 1, then the first node's information is being
// updated, otherwise it's the second node's information. The node ordering is
// determined by the lexicographical ordering of the identity public keys of the
// nodes on either side of the channel.
func (c *ChannelGraph) UpdateEdgePolicy(edge *models.ChannelEdgePolicy,
        op ...batch.SchedulerOption) error {

        var (
                isUpdate1    bool
                edgeNotFound bool
        )

        r := &batch.Request{
                Reset: func() {
                        isUpdate1 = false
                        edgeNotFound = false
                },
                Update: func(tx kvdb.RwTx) error {
                        var err error
                        isUpdate1, err = updateEdgePolicy(
                                tx, edge, c.graphCache,
                        )

                        // Silence ErrEdgeNotFound so that the batch can
                        // succeed, but propagate the error via local state.
                        if errors.Is(err, ErrEdgeNotFound) {
                                edgeNotFound = true
                                return nil
                        }

                        return err
                },
                OnCommit: func(err error) error {
                        switch {
                        case err != nil:
                                return err
                        case edgeNotFound:
                                return ErrEdgeNotFound
                        default:
                                c.updateEdgeCache(edge, isUpdate1)
                                return nil
                        }
                },
        }

        for _, f := range op {
                f(r)
        }

        return c.chanScheduler.Execute(r)
}

func (c *ChannelGraph) updateEdgeCache(e *models.ChannelEdgePolicy,
        isUpdate1 bool) {

        // If an entry for this channel is found in reject cache, we'll modify
        // the entry with the updated timestamp for the direction that was just
        // written. If the edge doesn't exist, we'll load the cache entry lazily
        // during the next query for this edge.
        if entry, ok := c.rejectCache.get(e.ChannelID); ok {
                if isUpdate1 {
                        entry.upd1Time = e.LastUpdate.Unix()
                } else {
                        entry.upd2Time = e.LastUpdate.Unix()
                }
                c.rejectCache.insert(e.ChannelID, entry)
        }

        // If an entry for this channel is found in channel cache, we'll modify
        // the entry with the updated policy for the direction that was just
        // written. If the edge doesn't exist, we'll defer loading the info and
        // policies and lazily read from disk during the next query.
        if channel, ok := c.chanCache.get(e.ChannelID); ok {
                if isUpdate1 {
                        channel.Policy1 = e
                } else {
                        channel.Policy2 = e
                }
                c.chanCache.insert(e.ChannelID, channel)
        }
}

// updateEdgePolicy attempts to update an edge's policy within the relevant
// buckets using an existing database transaction. The returned boolean will be
// true if the updated policy belongs to node1, and false if the policy belonged
// to node2.
func updateEdgePolicy(tx kvdb.RwTx, edge *models.ChannelEdgePolicy,
        graphCache *GraphCache) (bool, error) {

        edges := tx.ReadWriteBucket(edgeBucket)
        if edges == nil {
                return false, ErrEdgeNotFound
        }
        edgeIndex := edges.NestedReadWriteBucket(edgeIndexBucket)
        if edgeIndex == nil {
                return false, ErrEdgeNotFound
        }

        // Create the channelID key be converting the channel ID
        // integer into a byte slice.
        var chanID [8]byte
        byteOrder.PutUint64(chanID[:], edge.ChannelID)

        // With the channel ID, we then fetch the value storing the two
        // nodes which connect this channel edge.
        nodeInfo := edgeIndex.Get(chanID[:])
        if nodeInfo == nil {
                return false, ErrEdgeNotFound
        }

        // Depending on the flags value passed above, either the first
        // or second edge policy is being updated.
        var fromNode, toNode []byte
        var isUpdate1 bool
        if edge.ChannelFlags&lnwire.ChanUpdateDirection == 0 {
                fromNode = nodeInfo[:33]
                toNode = nodeInfo[33:66]
                isUpdate1 = true
        } else {
                fromNode = nodeInfo[33:66]
                toNode = nodeInfo[:33]
                isUpdate1 = false
        }

        // Finally, with the direction of the edge being updated
        // identified, we update the on-disk edge representation.
        err := putChanEdgePolicy(edges, edge, fromNode, toNode)
        if err != nil {
                return false, err
        }

        var (
                fromNodePubKey route.Vertex
                toNodePubKey   route.Vertex
        )
        copy(fromNodePubKey[:], fromNode)
        copy(toNodePubKey[:], toNode)

        if graphCache != nil {
                graphCache.UpdatePolicy(
                        edge, fromNodePubKey, toNodePubKey, isUpdate1,
                )
        }

        return isUpdate1, nil
}

// isPublic determines whether the node is seen as public within the graph from
// the source node's point of view. An existing database transaction can also be
// specified.
func (c *ChannelGraph) isPublic(tx kvdb.RTx, nodePub route.Vertex,
        sourcePubKey []byte) (bool, error) {

        // In order to determine whether this node is publicly advertised within
        // the graph, we'll need to look at all of its edges and check whether
        // they extend to any other node than the source node. errDone will be
        // used to terminate the check early.
        nodeIsPublic := false
        errDone := errors.New("done")
        err := c.ForEachNodeChannelTx(tx, nodePub, func(tx kvdb.RTx,
                info *models.ChannelEdgeInfo, _ *models.ChannelEdgePolicy,
                _ *models.ChannelEdgePolicy) error {

                // If this edge doesn't extend to the source node, we'll
                // terminate our search as we can now conclude that the node is
                // publicly advertised within the graph due to the local node
                // knowing of the current edge.
                if !bytes.Equal(info.NodeKey1Bytes[:], sourcePubKey) &&
                        !bytes.Equal(info.NodeKey2Bytes[:], sourcePubKey) {

                        nodeIsPublic = true
                        return errDone
                }

                // Since the edge _does_ extend to the source node, we'll also
                // need to ensure that this is a public edge.
                if info.AuthProof != nil {
                        nodeIsPublic = true
                        return errDone
                }

                // Otherwise, we'll continue our search.
                return nil
        })
        if err != nil && err != errDone {
                return false, err
        }

        return nodeIsPublic, nil
}

// FetchLightningNodeTx attempts to look up a target node by its identity
// public key. If the node isn't found in the database, then
// ErrGraphNodeNotFound is returned. An optional transaction may be provided.
// If none is provided, then a new one will be created.
func (c *ChannelGraph) FetchLightningNodeTx(tx kvdb.RTx, nodePub route.Vertex) (
        *models.LightningNode, error) {

        return c.fetchLightningNode(tx, nodePub)
}

// FetchLightningNode attempts to look up a target node by its identity public
// key. If the node isn't found in the database, then ErrGraphNodeNotFound is
// returned.
func (c *ChannelGraph) FetchLightningNode(nodePub route.Vertex) (
        *models.LightningNode, error) {

        return c.fetchLightningNode(nil, nodePub)
}

// fetchLightningNode attempts to look up a target node by its identity public
// key. If the node isn't found in the database, then ErrGraphNodeNotFound is
// returned. An optional transaction may be provided. If none is provided, then
// a new one will be created.
func (c *ChannelGraph) fetchLightningNode(tx kvdb.RTx,
        nodePub route.Vertex) (*models.LightningNode, error) {

        var node *models.LightningNode
        fetch := func(tx kvdb.RTx) error {
                // First grab the nodes bucket which stores the mapping from
                // pubKey to node information.
                nodes := tx.ReadBucket(nodeBucket)
                if nodes == nil {
                        return ErrGraphNotFound
                }

                // If a key for this serialized public key isn't found, then
                // the target node doesn't exist within the database.
                nodeBytes := nodes.Get(nodePub[:])
                if nodeBytes == nil {
                        return ErrGraphNodeNotFound
                }

                // If the node is found, then we can de deserialize the node
                // information to return to the user.
                nodeReader := bytes.NewReader(nodeBytes)
                n, err := deserializeLightningNode(nodeReader)
                if err != nil {
                        return err
                }

                node = &n

                return nil
        }

        if tx == nil {
                err := kvdb.View(
                        c.db, fetch, func() {
                                node = nil
                        },
                )
                if err != nil {
                        return nil, err
                }

                return node, nil
        }

        err := fetch(tx)
        if err != nil {
                return nil, err
        }

        return node, nil
}

// graphCacheNode is a struct that wraps a LightningNode in a way that it can be
// cached in the graph cache.
type graphCacheNode struct {
        pubKeyBytes route.Vertex
        features    *lnwire.FeatureVector
}

// newGraphCacheNode returns a new cache optimized node.
func newGraphCacheNode(pubKey route.Vertex,
        features *lnwire.FeatureVector) *graphCacheNode {

        return &graphCacheNode{
                pubKeyBytes: pubKey,
                features:    features,
        }
}

// PubKey returns the node's public identity key.
func (n *graphCacheNode) PubKey() route.Vertex {
        return n.pubKeyBytes
}

// Features returns the node's features.
func (n *graphCacheNode) Features() *lnwire.FeatureVector {
        return n.features
}

// ForEachChannel iterates through all channels of this node, executing the
// passed callback with an edge info structure and the policies of each end
// of the channel. The first edge policy is the outgoing edge *to* the
// connecting node, while the second is the incoming edge *from* the
// connecting node. If the callback returns an error, then the iteration is
// halted with the error propagated back up to the caller.
//
// Unknown policies are passed into the callback as nil values.
func (n *graphCacheNode) ForEachChannel(tx kvdb.RTx,
        cb func(kvdb.RTx, *models.ChannelEdgeInfo, *models.ChannelEdgePolicy,
                *models.ChannelEdgePolicy) error) error {

        return nodeTraversal(tx, n.pubKeyBytes[:], nil, cb)
}

var _ GraphCacheNode = (*graphCacheNode)(nil)

// HasLightningNode determines if the graph has a vertex identified by the
// target node identity public key. If the node exists in the database, a
// timestamp of when the data for the node was lasted updated is returned along
// with a true boolean. Otherwise, an empty time.Time is returned with a false
// boolean.
func (c *ChannelGraph) HasLightningNode(nodePub [33]byte) (time.Time, bool,
        error) {

        var (
                updateTime time.Time
                exists     bool
        )

        err := kvdb.View(c.db, func(tx kvdb.RTx) error {
                // First grab the nodes bucket which stores the mapping from
                // pubKey to node information.
                nodes := tx.ReadBucket(nodeBucket)
                if nodes == nil {
                        return ErrGraphNotFound
                }

                // If a key for this serialized public key isn't found, we can
                // exit early.
                nodeBytes := nodes.Get(nodePub[:])
                if nodeBytes == nil {
                        exists = false
                        return nil
                }

                // Otherwise we continue on to obtain the time stamp
                // representing the last time the data for this node was
                // updated.
                nodeReader := bytes.NewReader(nodeBytes)
                node, err := deserializeLightningNode(nodeReader)
                if err != nil {
                        return err
                }

                exists = true
                updateTime = node.LastUpdate
                return nil
        }, func() {
                updateTime = time.Time{}
                exists = false
        })
        if err != nil {
                return time.Time{}, exists, err
        }

        return updateTime, exists, nil
}

// nodeTraversal is used to traverse all channels of a node given by its
// public key and passes channel information into the specified callback.
func nodeTraversal(tx kvdb.RTx, nodePub []byte, db kvdb.Backend,
        cb func(kvdb.RTx, *models.ChannelEdgeInfo, *models.ChannelEdgePolicy,
                *models.ChannelEdgePolicy) error) error {

        traversal := func(tx kvdb.RTx) error {
                edges := tx.ReadBucket(edgeBucket)
                if edges == nil {
                        return ErrGraphNotFound
                }
                edgeIndex := edges.NestedReadBucket(edgeIndexBucket)
                if edgeIndex == nil {
                        return ErrGraphNoEdgesFound
                }

                // In order to reach all the edges for this node, we take
                // advantage of the construction of the key-space within the
                // edge bucket. The keys are stored in the form: pubKey ||
                // chanID. Therefore, starting from a chanID of zero, we can
                // scan forward in the bucket, grabbing all the edges for the
                // node. Once the prefix no longer matches, then we know we're
                // done.
                var nodeStart [33 + 8]byte
                copy(nodeStart[:], nodePub)
                copy(nodeStart[33:], chanStart[:])

                // Starting from the key pubKey || 0, we seek forward in the
                // bucket until the retrieved key no longer has the public key
                // as its prefix. This indicates that we've stepped over into
                // another node's edges, so we can terminate our scan.
                edgeCursor := edges.ReadCursor()
                for nodeEdge, _ := edgeCursor.Seek(nodeStart[:]); bytes.HasPrefix(nodeEdge, nodePub); nodeEdge, _ = edgeCursor.Next() { //nolint:ll
                        // If the prefix still matches, the channel id is
                        // returned in nodeEdge. Channel id is used to lookup
                        // the node at the other end of the channel and both
                        // edge policies.
                        chanID := nodeEdge[33:]
                        edgeInfo, err := fetchChanEdgeInfo(edgeIndex, chanID)
                        if err != nil {
                                return err
                        }

                        outgoingPolicy, err := fetchChanEdgePolicy(
                                edges, chanID, nodePub,
                        )
                        if err != nil {
                                return err
                        }

                        otherNode, err := edgeInfo.OtherNodeKeyBytes(nodePub)
                        if err != nil {
                                return err
                        }

                        incomingPolicy, err := fetchChanEdgePolicy(
                                edges, chanID, otherNode[:],
                        )
                        if err != nil {
                                return err
                        }

                        // Finally, we execute the callback.
                        err = cb(tx, &edgeInfo, outgoingPolicy, incomingPolicy)
                        if err != nil {
                                return err
                        }
                }

                return nil
        }

        // If no transaction was provided, then we'll create a new transaction
        // to execute the transaction within.
        if tx == nil {
                return kvdb.View(db, traversal, func() {})
        }

        // Otherwise, we re-use the existing transaction to execute the graph
        // traversal.
        return traversal(tx)
}

// ForEachNodeChannel iterates through all channels of the given node,
// executing the passed callback with an edge info structure and the policies
// of each end of the channel. The first edge policy is the outgoing edge *to*
// the connecting node, while the second is the incoming edge *from* the
// connecting node. If the callback returns an error, then the iteration is
// halted with the error propagated back up to the caller.
//
// Unknown policies are passed into the callback as nil values.
func (c *ChannelGraph) ForEachNodeChannel(nodePub route.Vertex,
        cb func(kvdb.RTx, *models.ChannelEdgeInfo, *models.ChannelEdgePolicy,
                *models.ChannelEdgePolicy) error) error {

        return nodeTraversal(nil, nodePub[:], c.db, cb)
}

// ForEachNodeChannelTx iterates through all channels of the given node,
// executing the passed callback with an edge info structure and the policies
// of each end of the channel. The first edge policy is the outgoing edge *to*
// the connecting node, while the second is the incoming edge *from* the
// connecting node. If the callback returns an error, then the iteration is
// halted with the error propagated back up to the caller.
//
// Unknown policies are passed into the callback as nil values.
//
// If the caller wishes to re-use an existing boltdb transaction, then it
// should be passed as the first argument.  Otherwise, the first argument should
// be nil and a fresh transaction will be created to execute the graph
// traversal.
func (c *ChannelGraph) ForEachNodeChannelTx(tx kvdb.RTx,
        nodePub route.Vertex, cb func(kvdb.RTx, *models.ChannelEdgeInfo,
                *models.ChannelEdgePolicy,
                *models.ChannelEdgePolicy) error) error {

        return nodeTraversal(tx, nodePub[:], c.db, cb)
}

// FetchOtherNode attempts to fetch the full LightningNode that's opposite of
// the target node in the channel. This is useful when one knows the pubkey of
// one of the nodes, and wishes to obtain the full LightningNode for the other
// end of the channel.
func (c *ChannelGraph) FetchOtherNode(tx kvdb.RTx,
        channel *models.ChannelEdgeInfo, thisNodeKey []byte) (
        *models.LightningNode, error) {

        // Ensure that the node passed in is actually a member of the channel.
        var targetNodeBytes [33]byte
        switch {
        case bytes.Equal(channel.NodeKey1Bytes[:], thisNodeKey):
                targetNodeBytes = channel.NodeKey2Bytes
        case bytes.Equal(channel.NodeKey2Bytes[:], thisNodeKey):
                targetNodeBytes = channel.NodeKey1Bytes
        default:
                return nil, fmt.Errorf("node not participating in this channel")
        }

        var targetNode *models.LightningNode
        fetchNodeFunc := func(tx kvdb.RTx) error {
                // First grab the nodes bucket which stores the mapping from
                // pubKey to node information.
                nodes := tx.ReadBucket(nodeBucket)
                if nodes == nil {
                        return ErrGraphNotFound
                }

                node, err := fetchLightningNode(nodes, targetNodeBytes[:])
                if err != nil {
                        return err
                }

                targetNode = &node

                return nil
        }

        // If the transaction is nil, then we'll need to create a new one,
        // otherwise we can use the existing db transaction.
        var err error
        if tx == nil {
                err = kvdb.View(c.db, fetchNodeFunc, func() {
                        targetNode = nil
                })
        } else {
                err = fetchNodeFunc(tx)
        }

        return targetNode, err
}

// computeEdgePolicyKeys is a helper function that can be used to compute the
// keys used to index the channel edge policy info for the two nodes of the
// edge. The keys for node 1 and node 2 are returned respectively.
func computeEdgePolicyKeys(info *models.ChannelEdgeInfo) ([]byte, []byte) {
        var (
                node1Key [33 + 8]byte
                node2Key [33 + 8]byte
        )

        copy(node1Key[:], info.NodeKey1Bytes[:])
        copy(node2Key[:], info.NodeKey2Bytes[:])

        byteOrder.PutUint64(node1Key[33:], info.ChannelID)
        byteOrder.PutUint64(node2Key[33:], info.ChannelID)

        return node1Key[:], node2Key[:]
}

// FetchChannelEdgesByOutpoint attempts to lookup the two directed edges for
// the channel identified by the funding outpoint. If the channel can't be
// found, then ErrEdgeNotFound is returned. A struct which houses the general
// information for the channel itself is returned as well as two structs that
// contain the routing policies for the channel in either direction.
func (c *ChannelGraph) FetchChannelEdgesByOutpoint(op *wire.OutPoint) (
        *models.ChannelEdgeInfo, *models.ChannelEdgePolicy,
        *models.ChannelEdgePolicy, error) {

        var (
                edgeInfo *models.ChannelEdgeInfo
                policy1  *models.ChannelEdgePolicy
                policy2  *models.ChannelEdgePolicy
        )

        err := kvdb.View(c.db, func(tx kvdb.RTx) error {
                // First, grab the node bucket. This will be used to populate
                // the Node pointers in each edge read from disk.
                nodes := tx.ReadBucket(nodeBucket)
                if nodes == nil {
                        return ErrGraphNotFound
                }

                // Next, grab the edge bucket which stores the edges, and also
                // the index itself so we can group the directed edges together
                // logically.
                edges := tx.ReadBucket(edgeBucket)
                if edges == nil {
                        return ErrGraphNoEdgesFound
                }
                edgeIndex := edges.NestedReadBucket(edgeIndexBucket)
                if edgeIndex == nil {
                        return ErrGraphNoEdgesFound
                }

                // If the channel's outpoint doesn't exist within the outpoint
                // index, then the edge does not exist.
                chanIndex := edges.NestedReadBucket(channelPointBucket)
                if chanIndex == nil {
                        return ErrGraphNoEdgesFound
                }
                var b bytes.Buffer
                if err := WriteOutpoint(&b, op); err != nil {
                        return err
                }
                chanID := chanIndex.Get(b.Bytes())
                if chanID == nil {
                        return fmt.Errorf("%w: op=%v", ErrEdgeNotFound, op)
                }

                // If the channel is found to exists, then we'll first retrieve
                // the general information for the channel.
                edge, err := fetchChanEdgeInfo(edgeIndex, chanID)
                if err != nil {
                        return fmt.Errorf("%w: chanID=%x", err, chanID)
                }
                edgeInfo = &edge

                // Once we have the information about the channels' parameters,
                // we'll fetch the routing policies for each for the directed
                // edges.
                e1, e2, err := fetchChanEdgePolicies(edgeIndex, edges, chanID)
                if err != nil {
                        return fmt.Errorf("failed to find policy: %w", err)
                }

                policy1 = e1
                policy2 = e2
                return nil
        }, func() {
                edgeInfo = nil
                policy1 = nil
                policy2 = nil
        })
        if err != nil {
                return nil, nil, nil, err
        }

        return edgeInfo, policy1, policy2, nil
}

// FetchChannelEdgesByID attempts to lookup the two directed edges for the
// channel identified by the channel ID. If the channel can't be found, then
// ErrEdgeNotFound is returned. A struct which houses the general information
// for the channel itself is returned as well as two structs that contain the
// routing policies for the channel in either direction.
//
// ErrZombieEdge an be returned if the edge is currently marked as a zombie
// within the database. In this case, the ChannelEdgePolicy's will be nil, and
// the ChannelEdgeInfo will only include the public keys of each node.
func (c *ChannelGraph) FetchChannelEdgesByID(chanID uint64) (
        *models.ChannelEdgeInfo, *models.ChannelEdgePolicy,
        *models.ChannelEdgePolicy, error) {

        var (
                edgeInfo  *models.ChannelEdgeInfo
                policy1   *models.ChannelEdgePolicy
                policy2   *models.ChannelEdgePolicy
                channelID [8]byte
        )

        err := kvdb.View(c.db, func(tx kvdb.RTx) error {
                // First, grab the node bucket. This will be used to populate
                // the Node pointers in each edge read from disk.
                nodes := tx.ReadBucket(nodeBucket)
                if nodes == nil {
                        return ErrGraphNotFound
                }

                // Next, grab the edge bucket which stores the edges, and also
                // the index itself so we can group the directed edges together
                // logically.
                edges := tx.ReadBucket(edgeBucket)
                if edges == nil {
                        return ErrGraphNoEdgesFound
                }
                edgeIndex := edges.NestedReadBucket(edgeIndexBucket)
                if edgeIndex == nil {
                        return ErrGraphNoEdgesFound
                }

                byteOrder.PutUint64(channelID[:], chanID)

                // Now, attempt to fetch edge.
                edge, err := fetchChanEdgeInfo(edgeIndex, channelID[:])

                // If it doesn't exist, we'll quickly check our zombie index to
                // see if we've previously marked it as so.
                if errors.Is(err, ErrEdgeNotFound) {
                        // If the zombie index doesn't exist, or the edge is not
                        // marked as a zombie within it, then we'll return the
                        // original ErrEdgeNotFound error.
                        zombieIndex := edges.NestedReadBucket(zombieBucket)
                        if zombieIndex == nil {
                                return ErrEdgeNotFound
                        }

                        isZombie, pubKey1, pubKey2 := isZombieEdge(
                                zombieIndex, chanID,
                        )
                        if !isZombie {
                                return ErrEdgeNotFound
                        }

                        // Otherwise, the edge is marked as a zombie, so we'll
                        // populate the edge info with the public keys of each
                        // party as this is the only information we have about
                        // it and return an error signaling so.
                        edgeInfo = &models.ChannelEdgeInfo{
                                NodeKey1Bytes: pubKey1,
                                NodeKey2Bytes: pubKey2,
                        }
                        return ErrZombieEdge
                }

                // Otherwise, we'll just return the error if any.
                if err != nil {
                        return err
                }

                edgeInfo = &edge

                // Then we'll attempt to fetch the accompanying policies of this
                // edge.
                e1, e2, err := fetchChanEdgePolicies(
                        edgeIndex, edges, channelID[:],
                )
                if err != nil {
                        return err
                }

                policy1 = e1
                policy2 = e2
                return nil
        }, func() {
                edgeInfo = nil
                policy1 = nil
                policy2 = nil
        })
        if err == ErrZombieEdge {
                return edgeInfo, nil, nil, err
        }
        if err != nil {
                return nil, nil, nil, err
        }

        return edgeInfo, policy1, policy2, nil
}

// IsPublicNode is a helper method that determines whether the node with the
// given public key is seen as a public node in the graph from the graph's
// source node's point of view.
func (c *ChannelGraph) IsPublicNode(pubKey [33]byte) (bool, error) {
        var nodeIsPublic bool
        err := kvdb.View(c.db, func(tx kvdb.RTx) error {
                nodes := tx.ReadBucket(nodeBucket)
                if nodes == nil {
                        return ErrGraphNodesNotFound
                }
                ourPubKey := nodes.Get(sourceKey)
                if ourPubKey == nil {
                        return ErrSourceNodeNotSet
                }
                node, err := fetchLightningNode(nodes, pubKey[:])
                if err != nil {
                        return err
                }

                nodeIsPublic, err = c.isPublic(tx, node.PubKeyBytes, ourPubKey)
                return err
        }, func() {
                nodeIsPublic = false
        })
        if err != nil {
                return false, err
        }

        return nodeIsPublic, nil
}

// genMultiSigP2WSH generates the p2wsh'd multisig script for 2 of 2 pubkeys.
func genMultiSigP2WSH(aPub, bPub []byte) ([]byte, error) {
        witnessScript, err := input.GenMultiSigScript(aPub, bPub)
        if err != nil {
                return nil, err
        }

        // With the witness script generated, we'll now turn it into a p2wsh
        // script:
        //  * OP_0 <sha256(script)>
        bldr := txscript.NewScriptBuilder(
                txscript.WithScriptAllocSize(input.P2WSHSize),
        )
        bldr.AddOp(txscript.OP_0)
        scriptHash := sha256.Sum256(witnessScript)
        bldr.AddData(scriptHash[:])

        return bldr.Script()
}

// EdgePoint couples the outpoint of a channel with the funding script that it
// creates. The FilteredChainView will use this to watch for spends of this
// edge point on chain. We require both of these values as depending on the
// concrete implementation, either the pkScript, or the out point will be used.
type EdgePoint struct {
        // FundingPkScript is the p2wsh multi-sig script of the target channel.
        FundingPkScript []byte

        // OutPoint is the outpoint of the target channel.
        OutPoint wire.OutPoint
}

// String returns a human readable version of the target EdgePoint. We return
// the outpoint directly as it is enough to uniquely identify the edge point.
func (e *EdgePoint) String() string {
        return e.OutPoint.String()
}

// ChannelView returns the verifiable edge information for each active channel
// within the known channel graph. The set of UTXO's (along with their scripts)
// returned are the ones that need to be watched on chain to detect channel
// closes on the resident blockchain.
func (c *ChannelGraph) ChannelView() ([]EdgePoint, error) {
        var edgePoints []EdgePoint
        if err := kvdb.View(c.db, func(tx kvdb.RTx) error {
                // We're going to iterate over the entire channel index, so
                // we'll need to fetch the edgeBucket to get to the index as
                // it's a sub-bucket.
                edges := tx.ReadBucket(edgeBucket)
                if edges == nil {
                        return ErrGraphNoEdgesFound
                }
                chanIndex := edges.NestedReadBucket(channelPointBucket)
                if chanIndex == nil {
                        return ErrGraphNoEdgesFound
                }
                edgeIndex := edges.NestedReadBucket(edgeIndexBucket)
                if edgeIndex == nil {
                        return ErrGraphNoEdgesFound
                }

                // Once we have the proper bucket, we'll range over each key
                // (which is the channel point for the channel) and decode it,
                // accumulating each entry.
                return chanIndex.ForEach(
                        func(chanPointBytes, chanID []byte) error {
                                chanPointReader := bytes.NewReader(
                                        chanPointBytes,
                                )

                                var chanPoint wire.OutPoint
                                err := ReadOutpoint(chanPointReader, &chanPoint)
                                if err != nil {
                                        return err
                                }

                                edgeInfo, err := fetchChanEdgeInfo(
                                        edgeIndex, chanID,
                                )
                                if err != nil {
                                        return err
                                }

                                pkScript, err := genMultiSigP2WSH(
                                        edgeInfo.BitcoinKey1Bytes[:],
                                        edgeInfo.BitcoinKey2Bytes[:],
                                )
                                if err != nil {
                                        return err
                                }

                                edgePoints = append(edgePoints, EdgePoint{
                                        FundingPkScript: pkScript,
                                        OutPoint:        chanPoint,
                                })

                                return nil
                        },
                )
        }, func() {
                edgePoints = nil
        }); err != nil {
                return nil, err
        }

        return edgePoints, nil
}

// MarkEdgeZombie attempts to mark a channel identified by its channel ID as a
// zombie. This method is used on an ad-hoc basis, when channels need to be
// marked as zombies outside the normal pruning cycle.
func (c *ChannelGraph) MarkEdgeZombie(chanID uint64,
        pubKey1, pubKey2 [33]byte) error {

        c.cacheMu.Lock()
        defer c.cacheMu.Unlock()

        err := kvdb.Batch(c.db, func(tx kvdb.RwTx) error {
                edges := tx.ReadWriteBucket(edgeBucket)
                if edges == nil {
                        return ErrGraphNoEdgesFound
                }
                zombieIndex, err := edges.CreateBucketIfNotExists(zombieBucket)
                if err != nil {
                        return fmt.Errorf("unable to create zombie "+
                                "bucket: %w", err)
                }

                if c.graphCache != nil {
                        c.graphCache.RemoveChannel(pubKey1, pubKey2, chanID)
                }

                return markEdgeZombie(zombieIndex, chanID, pubKey1, pubKey2)
        })
        if err != nil {
                return err
        }

        c.rejectCache.remove(chanID)
        c.chanCache.remove(chanID)

        return nil
}

// markEdgeZombie marks an edge as a zombie within our zombie index. The public
// keys should represent the node public keys of the two parties involved in the
// edge.
func markEdgeZombie(zombieIndex kvdb.RwBucket, chanID uint64, pubKey1,
        pubKey2 [33]byte) error {

        var k [8]byte
        byteOrder.PutUint64(k[:], chanID)

        var v [66]byte
        copy(v[:33], pubKey1[:])
        copy(v[33:], pubKey2[:])

        return zombieIndex.Put(k[:], v[:])
}

// MarkEdgeLive clears an edge from our zombie index, deeming it as live.
func (c *ChannelGraph) MarkEdgeLive(chanID uint64) error {
        c.cacheMu.Lock()
        defer c.cacheMu.Unlock()

        return c.markEdgeLiveUnsafe(nil, chanID)
}

// markEdgeLiveUnsafe clears an edge from the zombie index. This method can be
// called with an existing kvdb.RwTx or the argument can be set to nil in which
// case a new transaction will be created.
//
// NOTE: this method MUST only be called if the cacheMu has already been
// acquired.
func (c *ChannelGraph) markEdgeLiveUnsafe(tx kvdb.RwTx, chanID uint64) error {
        dbFn := func(tx kvdb.RwTx) error {
                edges := tx.ReadWriteBucket(edgeBucket)
                if edges == nil {
                        return ErrGraphNoEdgesFound
                }
                zombieIndex := edges.NestedReadWriteBucket(zombieBucket)
                if zombieIndex == nil {
                        return nil
                }

                var k [8]byte
                byteOrder.PutUint64(k[:], chanID)

                if len(zombieIndex.Get(k[:])) == 0 {
                        return ErrZombieEdgeNotFound
                }

                return zombieIndex.Delete(k[:])
        }

        // If the transaction is nil, we'll create a new one. Otherwise, we use
        // the existing transaction
        var err error
        if tx == nil {
                err = kvdb.Update(c.db, dbFn, func() {})
        } else {
                err = dbFn(tx)
        }
        if err != nil {
                return err
        }

        c.rejectCache.remove(chanID)
        c.chanCache.remove(chanID)

        // We need to add the channel back into our graph cache, otherwise we
        // won't use it for path finding.
        if c.graphCache != nil {
                edgeInfos, err := c.fetchChanInfos(tx, []uint64{chanID})
                if err != nil {
                        return err
                }

                for _, edgeInfo := range edgeInfos {
                        c.graphCache.AddChannel(
                                edgeInfo.Info, edgeInfo.Policy1,
                                edgeInfo.Policy2,
                        )
                }
        }

        return nil
}

// IsZombieEdge returns whether the edge is considered zombie. If it is a
// zombie, then the two node public keys corresponding to this edge are also
// returned.
func (c *ChannelGraph) IsZombieEdge(chanID uint64) (bool, [33]byte, [33]byte) {
        var (
                isZombie         bool
                pubKey1, pubKey2 [33]byte
        )

        err := kvdb.View(c.db, func(tx kvdb.RTx) error {
                edges := tx.ReadBucket(edgeBucket)
                if edges == nil {
                        return ErrGraphNoEdgesFound
                }
                zombieIndex := edges.NestedReadBucket(zombieBucket)
                if zombieIndex == nil {
                        return nil
                }

                isZombie, pubKey1, pubKey2 = isZombieEdge(zombieIndex, chanID)
                return nil
        }, func() {
                isZombie = false
                pubKey1 = [33]byte{}
                pubKey2 = [33]byte{}
        })
        if err != nil {
                return false, [33]byte{}, [33]byte{}
        }

        return isZombie, pubKey1, pubKey2
}

// isZombieEdge returns whether an entry exists for the given channel in the
// zombie index. If an entry exists, then the two node public keys corresponding
// to this edge are also returned.
func isZombieEdge(zombieIndex kvdb.RBucket,
        chanID uint64) (bool, [33]byte, [33]byte) {

        var k [8]byte
        byteOrder.PutUint64(k[:], chanID)

        v := zombieIndex.Get(k[:])
        if v == nil {
                return false, [33]byte{}, [33]byte{}
        }

        var pubKey1, pubKey2 [33]byte
        copy(pubKey1[:], v[:33])
        copy(pubKey2[:], v[33:])

        return true, pubKey1, pubKey2
}

// NumZombies returns the current number of zombie channels in the graph.
func (c *ChannelGraph) NumZombies() (uint64, error) {
        var numZombies uint64
        err := kvdb.View(c.db, func(tx kvdb.RTx) error {
                edges := tx.ReadBucket(edgeBucket)
                if edges == nil {
                        return nil
                }
                zombieIndex := edges.NestedReadBucket(zombieBucket)
                if zombieIndex == nil {
                        return nil
                }

                return zombieIndex.ForEach(func(_, _ []byte) error {
                        numZombies++
                        return nil
                })
        }, func() {
                numZombies = 0
        })
        if err != nil {
                return 0, err
        }

        return numZombies, nil
}

// PutClosedScid stores a SCID for a closed channel in the database. This is so
// that we can ignore channel announcements that we know to be closed without
// having to validate them and fetch a block.
func (c *ChannelGraph) PutClosedScid(scid lnwire.ShortChannelID) error {
        return kvdb.Update(c.db, func(tx kvdb.RwTx) error {
                closedScids, err := tx.CreateTopLevelBucket(closedScidBucket)
                if err != nil {
                        return err
                }

                var k [8]byte
                byteOrder.PutUint64(k[:], scid.ToUint64())

                return closedScids.Put(k[:], []byte{})
        }, func() {})
}

// IsClosedScid checks whether a channel identified by the passed in scid is
// closed. This helps avoid having to perform expensive validation checks.
// TODO: Add an LRU cache to cut down on disc reads.
func (c *ChannelGraph) IsClosedScid(scid lnwire.ShortChannelID) (bool, error) {
        var isClosed bool
        err := kvdb.View(c.db, func(tx kvdb.RTx) error {
                closedScids := tx.ReadBucket(closedScidBucket)
                if closedScids == nil {
                        return ErrClosedScidsNotFound
                }

                var k [8]byte
                byteOrder.PutUint64(k[:], scid.ToUint64())

                if closedScids.Get(k[:]) != nil {
                        isClosed = true
                        return nil
                }

                return nil
        }, func() {
                isClosed = false
        })
        if err != nil {
                return false, err
        }

        return isClosed, nil
}

func putLightningNode(nodeBucket kvdb.RwBucket, aliasBucket kvdb.RwBucket, // nolint:dupl
        updateIndex kvdb.RwBucket, node *models.LightningNode) error {

        var (
                scratch [16]byte
                b       bytes.Buffer
        )

        pub, err := node.PubKey()
        if err != nil {
                return err
        }
        nodePub := pub.SerializeCompressed()

        // If the node has the update time set, write it, else write 0.
        updateUnix := uint64(0)
        if node.LastUpdate.Unix() > 0 {
                updateUnix = uint64(node.LastUpdate.Unix())
        }

        byteOrder.PutUint64(scratch[:8], updateUnix)
        if _, err := b.Write(scratch[:8]); err != nil {
                return err
        }

        if _, err := b.Write(nodePub); err != nil {
                return err
        }

        // If we got a node announcement for this node, we will have the rest
        // of the data available. If not we don't have more data to write.
        if !node.HaveNodeAnnouncement {
                // Write HaveNodeAnnouncement=0.
                byteOrder.PutUint16(scratch[:2], 0)
                if _, err := b.Write(scratch[:2]); err != nil {
                        return err
                }

                return nodeBucket.Put(nodePub, b.Bytes())
        }

        // Write HaveNodeAnnouncement=1.
        byteOrder.PutUint16(scratch[:2], 1)
        if _, err := b.Write(scratch[:2]); err != nil {
                return err
        }

        if err := binary.Write(&b, byteOrder, node.Color.R); err != nil {
                return err
        }
        if err := binary.Write(&b, byteOrder, node.Color.G); err != nil {
                return err
        }
        if err := binary.Write(&b, byteOrder, node.Color.B); err != nil {
                return err
        }

        if err := wire.WriteVarString(&b, 0, node.Alias); err != nil {
                return err
        }

        if err := node.Features.Encode(&b); err != nil {
                return err
        }

        numAddresses := uint16(len(node.Addresses))
        byteOrder.PutUint16(scratch[:2], numAddresses)
        if _, err := b.Write(scratch[:2]); err != nil {
                return err
        }

        for _, address := range node.Addresses {
                if err := SerializeAddr(&b, address); err != nil {
                        return err
                }
        }

        sigLen := len(node.AuthSigBytes)
        if sigLen > 80 {
                return fmt.Errorf("max sig len allowed is 80, had %v",
                        sigLen)
        }

        err = wire.WriteVarBytes(&b, 0, node.AuthSigBytes)
        if err != nil {
                return err
        }

        if len(node.ExtraOpaqueData) > MaxAllowedExtraOpaqueBytes {
                return ErrTooManyExtraOpaqueBytes(len(node.ExtraOpaqueData))
        }
        err = wire.WriteVarBytes(&b, 0, node.ExtraOpaqueData)
        if err != nil {
                return err
        }

        if err := aliasBucket.Put(nodePub, []byte(node.Alias)); err != nil {
                return err
        }

        // With the alias bucket updated, we'll now update the index that
        // tracks the time series of node updates.
        var indexKey [8 + 33]byte
        byteOrder.PutUint64(indexKey[:8], updateUnix)
        copy(indexKey[8:], nodePub)

        // If there was already an old index entry for this node, then we'll
        // delete the old one before we write the new entry.
        if nodeBytes := nodeBucket.Get(nodePub); nodeBytes != nil {
                // Extract out the old update time to we can reconstruct the
                // prior index key to delete it from the index.
                oldUpdateTime := nodeBytes[:8]

                var oldIndexKey [8 + 33]byte
                copy(oldIndexKey[:8], oldUpdateTime)
                copy(oldIndexKey[8:], nodePub)

                if err := updateIndex.Delete(oldIndexKey[:]); err != nil {
                        return err
                }
        }

        if err := updateIndex.Put(indexKey[:], nil); err != nil {
                return err
        }

        return nodeBucket.Put(nodePub, b.Bytes())
}

func fetchLightningNode(nodeBucket kvdb.RBucket,
        nodePub []byte) (models.LightningNode, error) {

        nodeBytes := nodeBucket.Get(nodePub)
        if nodeBytes == nil {
                return models.LightningNode{}, ErrGraphNodeNotFound
        }

        nodeReader := bytes.NewReader(nodeBytes)
        return deserializeLightningNode(nodeReader)
}

func deserializeLightningNodeCacheable(r io.Reader) (*graphCacheNode, error) {
        // Always populate a feature vector, even if we don't have a node
        // announcement and short circuit below.
        node := newGraphCacheNode(
                route.Vertex{},
                lnwire.EmptyFeatureVector(),
        )

        var nodeScratch [8]byte

        // Skip ahead:
        // - LastUpdate (8 bytes)
        if _, err := r.Read(nodeScratch[:]); err != nil {
                return nil, err
        }

        if _, err := io.ReadFull(r, node.pubKeyBytes[:]); err != nil {
                return nil, err
        }

        // Read the node announcement flag.
        if _, err := r.Read(nodeScratch[:2]); err != nil {
                return nil, err
        }
        hasNodeAnn := byteOrder.Uint16(nodeScratch[:2])

        // The rest of the data is optional, and will only be there if we got a
        // node announcement for this node.
        if hasNodeAnn == 0 {
                return node, nil
        }

        // We did get a node announcement for this node, so we'll have the rest
        // of the data available.
        var rgb uint8
        if err := binary.Read(r, byteOrder, &rgb); err != nil {
                return nil, err
        }
        if err := binary.Read(r, byteOrder, &rgb); err != nil {
                return nil, err
        }
        if err := binary.Read(r, byteOrder, &rgb); err != nil {
                return nil, err
        }

        if _, err := wire.ReadVarString(r, 0); err != nil {
                return nil, err
        }

        if err := node.features.Decode(r); err != nil {
                return nil, err
        }

        return node, nil
}

func deserializeLightningNode(r io.Reader) (models.LightningNode, error) {
        var (
                node    models.LightningNode
                scratch [8]byte
                err     error
        )

        // Always populate a feature vector, even if we don't have a node
        // announcement and short circuit below.
        node.Features = lnwire.EmptyFeatureVector()

        if _, err := r.Read(scratch[:]); err != nil {
                return models.LightningNode{}, err
        }

        unix := int64(byteOrder.Uint64(scratch[:]))
        node.LastUpdate = time.Unix(unix, 0)

        if _, err := io.ReadFull(r, node.PubKeyBytes[:]); err != nil {
                return models.LightningNode{}, err
        }

        if _, err := r.Read(scratch[:2]); err != nil {
                return models.LightningNode{}, err
        }

        hasNodeAnn := byteOrder.Uint16(scratch[:2])
        if hasNodeAnn == 1 {
                node.HaveNodeAnnouncement = true
        } else {
                node.HaveNodeAnnouncement = false
        }

        // The rest of the data is optional, and will only be there if we got a
        // node announcement for this node.
        if !node.HaveNodeAnnouncement {
                return node, nil
        }

        // We did get a node announcement for this node, so we'll have the rest
        // of the data available.
        if err := binary.Read(r, byteOrder, &node.Color.R); err != nil {
                return models.LightningNode{}, err
        }
        if err := binary.Read(r, byteOrder, &node.Color.G); err != nil {
                return models.LightningNode{}, err
        }
        if err := binary.Read(r, byteOrder, &node.Color.B); err != nil {
                return models.LightningNode{}, err
        }

        node.Alias, err = wire.ReadVarString(r, 0)
        if err != nil {
                return models.LightningNode{}, err
        }

        err = node.Features.Decode(r)
        if err != nil {
                return models.LightningNode{}, err
        }

        if _, err := r.Read(scratch[:2]); err != nil {
                return models.LightningNode{}, err
        }
        numAddresses := int(byteOrder.Uint16(scratch[:2]))

        var addresses []net.Addr
        for i := 0; i < numAddresses; i++ {
                address, err := DeserializeAddr(r)
                if err != nil {
                        return models.LightningNode{}, err
                }
                addresses = append(addresses, address)
        }
        node.Addresses = addresses

        node.AuthSigBytes, err = wire.ReadVarBytes(r, 0, 80, "sig")
        if err != nil {
                return models.LightningNode{}, err
        }

        // We'll try and see if there are any opaque bytes left, if not, then
        // we'll ignore the EOF error and return the node as is.
        node.ExtraOpaqueData, err = wire.ReadVarBytes(
                r, 0, MaxAllowedExtraOpaqueBytes, "blob",
        )
        switch {
        case err == io.ErrUnexpectedEOF:
        case err == io.EOF:
        case err != nil:
                return models.LightningNode{}, err
        }

        return node, nil
}

func putChanEdgeInfo(edgeIndex kvdb.RwBucket,
        edgeInfo *models.ChannelEdgeInfo, chanID [8]byte) error {

        var b bytes.Buffer

        if _, err := b.Write(edgeInfo.NodeKey1Bytes[:]); err != nil {
                return err
        }
        if _, err := b.Write(edgeInfo.NodeKey2Bytes[:]); err != nil {
                return err
        }
        if _, err := b.Write(edgeInfo.BitcoinKey1Bytes[:]); err != nil {
                return err
        }
        if _, err := b.Write(edgeInfo.BitcoinKey2Bytes[:]); err != nil {
                return err
        }

        if err := wire.WriteVarBytes(&b, 0, edgeInfo.Features); err != nil {
                return err
        }

        authProof := edgeInfo.AuthProof
        var nodeSig1, nodeSig2, bitcoinSig1, bitcoinSig2 []byte
        if authProof != nil {
                nodeSig1 = authProof.NodeSig1Bytes
                nodeSig2 = authProof.NodeSig2Bytes
                bitcoinSig1 = authProof.BitcoinSig1Bytes
                bitcoinSig2 = authProof.BitcoinSig2Bytes
        }

        if err := wire.WriteVarBytes(&b, 0, nodeSig1); err != nil {
                return err
        }
        if err := wire.WriteVarBytes(&b, 0, nodeSig2); err != nil {
                return err
        }
        if err := wire.WriteVarBytes(&b, 0, bitcoinSig1); err != nil {
                return err
        }
        if err := wire.WriteVarBytes(&b, 0, bitcoinSig2); err != nil {
                return err
        }

        if err := WriteOutpoint(&b, &edgeInfo.ChannelPoint); err != nil {
                return err
        }
        err := binary.Write(&b, byteOrder, uint64(edgeInfo.Capacity))
        if err != nil {
                return err
        }
        if _, err := b.Write(chanID[:]); err != nil {
                return err
        }
        if _, err := b.Write(edgeInfo.ChainHash[:]); err != nil {
                return err
        }

        if len(edgeInfo.ExtraOpaqueData) > MaxAllowedExtraOpaqueBytes {
                return ErrTooManyExtraOpaqueBytes(len(edgeInfo.ExtraOpaqueData))
        }
        err = wire.WriteVarBytes(&b, 0, edgeInfo.ExtraOpaqueData)
        if err != nil {
                return err
        }

        return edgeIndex.Put(chanID[:], b.Bytes())
}

func fetchChanEdgeInfo(edgeIndex kvdb.RBucket,
        chanID []byte) (models.ChannelEdgeInfo, error) {

        edgeInfoBytes := edgeIndex.Get(chanID)
        if edgeInfoBytes == nil {
                return models.ChannelEdgeInfo{}, ErrEdgeNotFound
        }

        edgeInfoReader := bytes.NewReader(edgeInfoBytes)
        return deserializeChanEdgeInfo(edgeInfoReader)
}

func deserializeChanEdgeInfo(r io.Reader) (models.ChannelEdgeInfo, error) {
        var (
                err      error
                edgeInfo models.ChannelEdgeInfo
        )

        if _, err := io.ReadFull(r, edgeInfo.NodeKey1Bytes[:]); err != nil {
                return models.ChannelEdgeInfo{}, err
        }
        if _, err := io.ReadFull(r, edgeInfo.NodeKey2Bytes[:]); err != nil {
                return models.ChannelEdgeInfo{}, err
        }
        if _, err := io.ReadFull(r, edgeInfo.BitcoinKey1Bytes[:]); err != nil {
                return models.ChannelEdgeInfo{}, err
        }
        if _, err := io.ReadFull(r, edgeInfo.BitcoinKey2Bytes[:]); err != nil {
                return models.ChannelEdgeInfo{}, err
        }

        edgeInfo.Features, err = wire.ReadVarBytes(r, 0, 900, "features")
        if err != nil {
                return models.ChannelEdgeInfo{}, err
        }

        proof := &models.ChannelAuthProof{}

        proof.NodeSig1Bytes, err = wire.ReadVarBytes(r, 0, 80, "sigs")
        if err != nil {
                return models.ChannelEdgeInfo{}, err
        }
        proof.NodeSig2Bytes, err = wire.ReadVarBytes(r, 0, 80, "sigs")
        if err != nil {
                return models.ChannelEdgeInfo{}, err
        }
        proof.BitcoinSig1Bytes, err = wire.ReadVarBytes(r, 0, 80, "sigs")
        if err != nil {
                return models.ChannelEdgeInfo{}, err
        }
        proof.BitcoinSig2Bytes, err = wire.ReadVarBytes(r, 0, 80, "sigs")
        if err != nil {
                return models.ChannelEdgeInfo{}, err
        }

        if !proof.IsEmpty() {
                edgeInfo.AuthProof = proof
        }

        edgeInfo.ChannelPoint = wire.OutPoint{}
        if err := ReadOutpoint(r, &edgeInfo.ChannelPoint); err != nil {
                return models.ChannelEdgeInfo{}, err
        }
        if err := binary.Read(r, byteOrder, &edgeInfo.Capacity); err != nil {
                return models.ChannelEdgeInfo{}, err
        }
        if err := binary.Read(r, byteOrder, &edgeInfo.ChannelID); err != nil {
                return models.ChannelEdgeInfo{}, err
        }

        if _, err := io.ReadFull(r, edgeInfo.ChainHash[:]); err != nil {
                return models.ChannelEdgeInfo{}, err
        }

        // We'll try and see if there are any opaque bytes left, if not, then
        // we'll ignore the EOF error and return the edge as is.
        edgeInfo.ExtraOpaqueData, err = wire.ReadVarBytes(
                r, 0, MaxAllowedExtraOpaqueBytes, "blob",
        )
        switch {
        case err == io.ErrUnexpectedEOF:
        case err == io.EOF:
        case err != nil:
                return models.ChannelEdgeInfo{}, err
        }

        return edgeInfo, nil
}

func putChanEdgePolicy(edges kvdb.RwBucket, edge *models.ChannelEdgePolicy,
        from, to []byte) error {

        var edgeKey [33 + 8]byte
        copy(edgeKey[:], from)
        byteOrder.PutUint64(edgeKey[33:], edge.ChannelID)

        var b bytes.Buffer
        if err := serializeChanEdgePolicy(&b, edge, to); err != nil {
                return err
        }

        // Before we write out the new edge, we'll create a new entry in the
        // update index in order to keep it fresh.
        updateUnix := uint64(edge.LastUpdate.Unix())
        var indexKey [8 + 8]byte
        byteOrder.PutUint64(indexKey[:8], updateUnix)
        byteOrder.PutUint64(indexKey[8:], edge.ChannelID)

        updateIndex, err := edges.CreateBucketIfNotExists(edgeUpdateIndexBucket)
        if err != nil {
                return err
        }

        // If there was already an entry for this edge, then we'll need to
        // delete the old one to ensure we don't leave around any after-images.
        // An unknown policy value does not have a update time recorded, so
        // it also does not need to be removed.
        if edgeBytes := edges.Get(edgeKey[:]); edgeBytes != nil &&
                !bytes.Equal(edgeBytes[:], unknownPolicy) {

                // In order to delete the old entry, we'll need to obtain the
                // *prior* update time in order to delete it. To do this, we'll
                // need to deserialize the existing policy within the database
                // (now outdated by the new one), and delete its corresponding
                // entry within the update index. We'll ignore any
                // ErrEdgePolicyOptionalFieldNotFound error, as we only need
                // the channel ID and update time to delete the entry.
                // TODO(halseth): get rid of these invalid policies in a
                // migration.
                oldEdgePolicy, err := deserializeChanEdgePolicy(
                        bytes.NewReader(edgeBytes),
                )
                if err != nil && err != ErrEdgePolicyOptionalFieldNotFound {
                        return err
                }

                oldUpdateTime := uint64(oldEdgePolicy.LastUpdate.Unix())

                var oldIndexKey [8 + 8]byte
                byteOrder.PutUint64(oldIndexKey[:8], oldUpdateTime)
                byteOrder.PutUint64(oldIndexKey[8:], edge.ChannelID)

                if err := updateIndex.Delete(oldIndexKey[:]); err != nil {
                        return err
                }
        }

        if err := updateIndex.Put(indexKey[:], nil); err != nil {
                return err
        }

        updateEdgePolicyDisabledIndex(
                edges, edge.ChannelID,
                edge.ChannelFlags&lnwire.ChanUpdateDirection > 0,
                edge.IsDisabled(),
        )

        return edges.Put(edgeKey[:], b.Bytes()[:])
}

// updateEdgePolicyDisabledIndex is used to update the disabledEdgePolicyIndex
// bucket by either add a new disabled ChannelEdgePolicy or remove an existing
// one.
// The direction represents the direction of the edge and disabled is used for
// deciding whether to remove or add an entry to the bucket.
// In general a channel is disabled if two entries for the same chanID exist
// in this bucket.
// Maintaining the bucket this way allows a fast retrieval of disabled
// channels, for example when prune is needed.
func updateEdgePolicyDisabledIndex(edges kvdb.RwBucket, chanID uint64,
        direction bool, disabled bool) error {

        var disabledEdgeKey [8 + 1]byte
        byteOrder.PutUint64(disabledEdgeKey[0:], chanID)
        if direction {
                disabledEdgeKey[8] = 1
        }

        disabledEdgePolicyIndex, err := edges.CreateBucketIfNotExists(
                disabledEdgePolicyBucket,
        )
        if err != nil {
                return err
        }

        if disabled {
                return disabledEdgePolicyIndex.Put(disabledEdgeKey[:], []byte{})
        }

        return disabledEdgePolicyIndex.Delete(disabledEdgeKey[:])
}

// putChanEdgePolicyUnknown marks the edge policy as unknown
// in the edges bucket.
func putChanEdgePolicyUnknown(edges kvdb.RwBucket, channelID uint64,
        from []byte) error {

        var edgeKey [33 + 8]byte
        copy(edgeKey[:], from)
        byteOrder.PutUint64(edgeKey[33:], channelID)

        if edges.Get(edgeKey[:]) != nil {
                return fmt.Errorf("cannot write unknown policy for channel %v "+
                        " when there is already a policy present", channelID)
        }

        return edges.Put(edgeKey[:], unknownPolicy)
}

func fetchChanEdgePolicy(edges kvdb.RBucket, chanID []byte,
        nodePub []byte) (*models.ChannelEdgePolicy, error) {

        var edgeKey [33 + 8]byte
        copy(edgeKey[:], nodePub)
        copy(edgeKey[33:], chanID[:])

        edgeBytes := edges.Get(edgeKey[:])
        if edgeBytes == nil {
                return nil, ErrEdgeNotFound
        }

        // No need to deserialize unknown policy.
        if bytes.Equal(edgeBytes[:], unknownPolicy) {
                return nil, nil
        }

        edgeReader := bytes.NewReader(edgeBytes)

        ep, err := deserializeChanEdgePolicy(edgeReader)
        switch {
        // If the db policy was missing an expected optional field, we return
        // nil as if the policy was unknown.
        case err == ErrEdgePolicyOptionalFieldNotFound:
                return nil, nil

        case err != nil:
                return nil, err
        }

        return ep, nil
}

func fetchChanEdgePolicies(edgeIndex kvdb.RBucket, edges kvdb.RBucket,
        chanID []byte) (*models.ChannelEdgePolicy, *models.ChannelEdgePolicy,
        error) {

        edgeInfo := edgeIndex.Get(chanID)
        if edgeInfo == nil {
                return nil, nil, fmt.Errorf("%w: chanID=%x", ErrEdgeNotFound,
                        chanID)
        }

        // The first node is contained within the first half of the edge
        // information. We only propagate the error here and below if it's
        // something other than edge non-existence.
        node1Pub := edgeInfo[:33]
        edge1, err := fetchChanEdgePolicy(edges, chanID, node1Pub)
        if err != nil {
                return nil, nil, fmt.Errorf("%w: node1Pub=%x", ErrEdgeNotFound,
                        node1Pub)
        }

        // Similarly, the second node is contained within the latter
        // half of the edge information.
        node2Pub := edgeInfo[33:66]
        edge2, err := fetchChanEdgePolicy(edges, chanID, node2Pub)
        if err != nil {
                return nil, nil, fmt.Errorf("%w: node2Pub=%x", ErrEdgeNotFound,
                        node2Pub)
        }

        return edge1, edge2, nil
}

func serializeChanEdgePolicy(w io.Writer, edge *models.ChannelEdgePolicy,
        to []byte) error {

        err := wire.WriteVarBytes(w, 0, edge.SigBytes)
        if err != nil {
                return err
        }

        if err := binary.Write(w, byteOrder, edge.ChannelID); err != nil {
                return err
        }

        var scratch [8]byte
        updateUnix := uint64(edge.LastUpdate.Unix())
        byteOrder.PutUint64(scratch[:], updateUnix)
        if _, err := w.Write(scratch[:]); err != nil {
                return err
        }

        if err := binary.Write(w, byteOrder, edge.MessageFlags); err != nil {
                return err
        }
        if err := binary.Write(w, byteOrder, edge.ChannelFlags); err != nil {
                return err
        }
        if err := binary.Write(w, byteOrder, edge.TimeLockDelta); err != nil {
                return err
        }
        if err := binary.Write(w, byteOrder, uint64(edge.MinHTLC)); err != nil {
                return err
        }
        err = binary.Write(w, byteOrder, uint64(edge.FeeBaseMSat))
        if err != nil {
                return err
        }
        err = binary.Write(
                w, byteOrder, uint64(edge.FeeProportionalMillionths),
        )
        if err != nil {
                return err
        }

        if _, err := w.Write(to); err != nil {
                return err
        }

        // If the max_htlc field is present, we write it. To be compatible with
        // older versions that wasn't aware of this field, we write it as part
        // of the opaque data.
        // TODO(halseth): clean up when moving to TLV.
        var opaqueBuf bytes.Buffer
        if edge.MessageFlags.HasMaxHtlc() {
                err := binary.Write(&opaqueBuf, byteOrder, uint64(edge.MaxHTLC))
                if err != nil {
                        return err
                }
        }

        if len(edge.ExtraOpaqueData) > MaxAllowedExtraOpaqueBytes {
                return ErrTooManyExtraOpaqueBytes(len(edge.ExtraOpaqueData))
        }
        if _, err := opaqueBuf.Write(edge.ExtraOpaqueData); err != nil {
                return err
        }

        if err := wire.WriteVarBytes(w, 0, opaqueBuf.Bytes()); err != nil {
                return err
        }
        return nil
}

func deserializeChanEdgePolicy(r io.Reader) (*models.ChannelEdgePolicy, error) {
        // Deserialize the policy. Note that in case an optional field is not
        // found, both an error and a populated policy object are returned.
        edge, deserializeErr := deserializeChanEdgePolicyRaw(r)
        if deserializeErr != nil &&
                deserializeErr != ErrEdgePolicyOptionalFieldNotFound {

                return nil, deserializeErr
        }

        return edge, deserializeErr
}

func deserializeChanEdgePolicyRaw(r io.Reader) (*models.ChannelEdgePolicy,
        error) {

        edge := &models.ChannelEdgePolicy{}

        var err error
        edge.SigBytes, err = wire.ReadVarBytes(r, 0, 80, "sig")
        if err != nil {
                return nil, err
        }

        if err := binary.Read(r, byteOrder, &edge.ChannelID); err != nil {
                return nil, err
        }

        var scratch [8]byte
        if _, err := r.Read(scratch[:]); err != nil {
                return nil, err
        }
        unix := int64(byteOrder.Uint64(scratch[:]))
        edge.LastUpdate = time.Unix(unix, 0)

        if err := binary.Read(r, byteOrder, &edge.MessageFlags); err != nil {
                return nil, err
        }
        if err := binary.Read(r, byteOrder, &edge.ChannelFlags); err != nil {
                return nil, err
        }
        if err := binary.Read(r, byteOrder, &edge.TimeLockDelta); err != nil {
                return nil, err
        }

        var n uint64
        if err := binary.Read(r, byteOrder, &n); err != nil {
                return nil, err
        }
        edge.MinHTLC = lnwire.MilliSatoshi(n)

        if err := binary.Read(r, byteOrder, &n); err != nil {
                return nil, err
        }
        edge.FeeBaseMSat = lnwire.MilliSatoshi(n)

        if err := binary.Read(r, byteOrder, &n); err != nil {
                return nil, err
        }
        edge.FeeProportionalMillionths = lnwire.MilliSatoshi(n)

        if _, err := r.Read(edge.ToNode[:]); err != nil {
                return nil, err
        }

        // We'll try and see if there are any opaque bytes left, if not, then
        // we'll ignore the EOF error and return the edge as is.
        edge.ExtraOpaqueData, err = wire.ReadVarBytes(
                r, 0, MaxAllowedExtraOpaqueBytes, "blob",
        )
        switch {
        case err == io.ErrUnexpectedEOF:
        case err == io.EOF:
        case err != nil:
                return nil, err
        }

        // See if optional fields are present.
        if edge.MessageFlags.HasMaxHtlc() {
                // The max_htlc field should be at the beginning of the opaque
                // bytes.
                opq := edge.ExtraOpaqueData

                // If the max_htlc field is not present, it might be old data
                // stored before this field was validated. We'll return the
                // edge along with an error.
                if len(opq) < 8 {
                        return edge, ErrEdgePolicyOptionalFieldNotFound
                }

                maxHtlc := byteOrder.Uint64(opq[:8])
                edge.MaxHTLC = lnwire.MilliSatoshi(maxHtlc)

                // Exclude the parsed field from the rest of the opaque data.
                edge.ExtraOpaqueData = opq[8:]
        }

        return edge, nil
}

// MakeTestGraph creates a new instance of the ChannelGraph for testing
// purposes.
func MakeTestGraph(t testing.TB, modifiers ...OptionModifier) (*ChannelGraph,
        error) {

        opts := DefaultOptions()
        for _, modifier := range modifiers {
                modifier(opts)
        }

        // Next, create channelgraph for the first time.
        backend, backendCleanup, err := kvdb.GetTestBackend(t.TempDir(), "cgr")
        if err != nil {
                backendCleanup()
                return nil, err
        }

        graph, err := NewChannelGraph(backend)
        if err != nil {
                backendCleanup()
                return nil, err
        }

        t.Cleanup(func() {
                _ = backend.Close()
                backendCleanup()
        })

        return graph, nil
}

lightningnetwork / lnd / 12375116696

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