13566028875

Committed 27 Feb 2025 12:09PM UTC coverage: 49.396% (-9.4%) from 58.748%

Build # 13566028875

Build Type

Pull #9555

github

Committed by

ellemouton

Commit Message

graph/db: populate the graph cache in Start instead of during construction

In this commit, we move the graph cache population logic out of the
ChannelGraph constructor and into its Start method instead.

Pull Request Pull Request #9555: graph: extract cache from CRUD [6]

Run Details

34 of 54 new or added lines in 4 files covered. (62.96%)

27464 existing lines in 436 files now uncovered.

101095 of 204664 relevant lines covered (49.4%)

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Source File
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67.58

/graph/db/kv_store.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/btcsuite/btcwallet/walletdb"
        "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"
        "github.com/stretchr/testify/require"
)

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
)

// KVStore 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 KVStore struct {
        db kvdb.Backend

        // cacheMu guards all caches (rejectCache and chanCache). 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

        chanScheduler batch.Scheduler
        nodeScheduler batch.Scheduler
}

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

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

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

        g := &KVStore{
                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,
        )

        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 *KVStore) 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 errors.Is(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 *KVStore) Wipe() error {
        err := kvdb.Update(c.db, func(tx kvdb.RwTx) error {
                for _, tlb := range graphTopLevelBuckets {
                        err := tx.DeleteTopLevelBucket(tlb)
                        if err != nil &&
                                !errors.Is(err, kvdb.ErrBucketNotFound) {

                                return err
                        }
                }

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

        return initKVStore(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 initKVStore(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
}

// 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 *KVStore) 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 *KVStore) 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. An optional read
// transaction may be provided. If none is provided, a new one will be created.
//
// Unknown policies are passed into the callback as nil values.
func (c *KVStore) forEachNodeDirectedChannel(tx kvdb.RTx,
        node route.Vertex, cb func(channel *DirectedChannel) error) error {

        // Fallback that uses the database.
        toNodeCallback := func() route.Vertex {
                return node
        }
        toNodeFeatures, err := c.fetchNodeFeatures(tx, 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. An optional read
// transaction may be provided. If none is provided, a new one will be created.
func (c *KVStore) fetchNodeFeatures(tx kvdb.RTx,
        node route.Vertex) (*lnwire.FeatureVector, error) {

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

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

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

// 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.
//
// NOTE: this is part of the graphdb.NodeTraverser interface.
func (c *KVStore) ForEachNodeDirectedChannel(nodePub route.Vertex,
        cb func(channel *DirectedChannel) error) error {

        return c.forEachNodeDirectedChannel(nil, nodePub, cb)
}

// FetchNodeFeatures returns the features of the given node. If no features are
// known for the node, an empty feature vector is returned.
//
// NOTE: this is part of the graphdb.NodeTraverser interface.
func (c *KVStore) FetchNodeFeatures(nodePub route.Vertex) (
        *lnwire.FeatureVector, error) {

        return c.fetchNodeFeatures(nil, nodePub)
}

// ForEachNodeCached is similar to forEachNode, but it returns DirectedChannel
// data to the call-back.
//
// NOTE: The callback contents MUST not be modified.
func (c *KVStore) ForEachNodeCached(cb func(node route.Vertex,
        chans map[uint64]*DirectedChannel) error) error {

        // 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(
                                        tx, 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 *KVStore) 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. Any operations performed on the NodeTx passed to the call-back are
// executed under the same read transaction and so, methods on the NodeTx object
// _MUST_ only be called from within the call-back.
func (c *KVStore) ForEachNode(cb func(tx NodeRTx) error) error {
        return c.forEachNode(func(tx kvdb.RTx,
                node *models.LightningNode) error {

                return cb(newChanGraphNodeTx(tx, c, node))
        })
}

// 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 *KVStore) 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 *KVStore) ForEachNodeCacheable(cb func(route.Vertex,
        *lnwire.FeatureVector) 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, features, err := deserializeLightningNodeCacheable( //nolint:ll
                                nodeReader,
                        )
                        if err != nil {
                                return err
                        }

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

        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 *KVStore) 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 *KVStore) 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 *KVStore) 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 *KVStore) AddLightningNode(node *models.LightningNode,
        op ...batch.SchedulerOption) error {

        r := &batch.Request{
                Update: func(tx kvdb.RwTx) error {
                        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 *KVStore) 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 *KVStore) 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
                }

                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 *KVStore) 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 *KVStore) 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 errors.Is(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 *KVStore) 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
        }

        // 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 errors.Is(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: %w", edge.NodeKey1Bytes, err)
                }
        case node1Err != nil:
                return node1Err
        }

        _, node2Err := fetchLightningNode(nodes, edge.NodeKey2Bytes[:])
        switch {
        case errors.Is(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: %w", edge.NodeKey2Bytes, err)
                }
        case node2Err != nil:
                return node2Err
        }

        // 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[:])
}

// 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 *KVStore) 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
}

// AddEdgeProof sets the proof of an existing edge in the graph database.
func (c *KVStore) AddEdgeProof(chanID lnwire.ShortChannelID,
        proof *models.ChannelAuthProof) error {

        // Construct the channel's primary key which is the 8-byte channel ID.
        var chanKey [8]byte
        binary.BigEndian.PutUint64(chanKey[:], chanID.ToUint64())

        return 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
                }

                edge, err := fetchChanEdgeInfo(edgeIndex, chanKey[:])
                if err != nil {
                        return err
                }

                edge.AuthProof = proof

                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 along with any pruned nodes are returned if the function
// succeeds without error.
func (c *KVStore) PruneGraph(spentOutputs []*wire.OutPoint,
        blockHash *chainhash.Hash, blockHeight uint32) (
        []*models.ChannelEdgeInfo, []route.Vertex, error) {

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

        var (
                chansClosed []*models.ChannelEdgeInfo
                prunedNodes []route.Vertex
        )

        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
                        }

                        // 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.
                        edgeInfo, 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.
                prunedNodes, err = c.pruneGraphNodes(nodes, edgeIndex)

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

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

        return chansClosed, prunedNodes, 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 *KVStore) PruneGraphNodes() ([]route.Vertex, error) {
        var prunedNodes []route.Vertex
        err := 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
                }

                var err error
                prunedNodes, err = c.pruneGraphNodes(nodes, edgeIndex)
                if err != nil {
                        return err
                }

                return nil
        }, func() {
                prunedNodes = nil
        })

        return prunedNodes, err
}

// 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 *KVStore) pruneGraphNodes(nodes kvdb.RwBucket,
        edgeIndex kvdb.RwBucket) ([]route.Vertex, 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 nil, 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 nil, 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 nil, 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 pruned []route.Vertex
        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 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 nil, err
                }

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

                pruned = append(pruned, nodePubKey)
        }

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

        return pruned, err
}

// 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 *KVStore) 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, _ := cursor.Seek(chanIDStart[:]); k != nil &&
                        bytes.Compare(k, chanIDEnd[:]) < 0; k, _ = cursor.Next() {
                        keys = append(keys, k)
                }

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

                        removedChans = append(removedChans, edgeInfo)
                }

                // 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 *KVStore) 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 *KVStore) DeleteChannelEdges(strictZombiePruning, markZombie bool,
        chanIDs ...uint64) ([]*models.ChannelEdgeInfo, 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()

        var infos []*models.ChannelEdgeInfo
        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)
                        edgeInfo, err := c.delChannelEdgeUnsafe(
                                edges, edgeIndex, chanIndex, zombieIndex,
                                rawChanID[:], markZombie, strictZombiePruning,
                        )
                        if err != nil {
                                return err
                        }

                        infos = append(infos, edgeInfo)
                }

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

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

        return infos, 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 *KVStore) 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 *KVStore) 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 && !errors.Is(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 *KVStore) 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 errors.Is(err, ErrGraphNoEdgesFound):
                fallthrough
        case errors.Is(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 *KVStore) 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 errors.Is(err, ErrGraphNoEdgesFound):
                fallthrough
        case errors.Is(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. The ChannelUpdateInfos for the
// known zombies is also returned.
func (c *KVStore) FilterKnownChanIDs(chansInfo []ChannelUpdateInfo) ([]uint64,
        []ChannelUpdateInfo, error) {

        var (
                newChanIDs   []uint64
                knownZombies []ChannelUpdateInfo
        )

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

        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
                }

                // 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,
                                )

                                if isZombie {
                                        knownZombies = append(
                                                knownZombies, info,
                                        )

                                        continue
                                }
                        }

                        newChanIDs = append(newChanIDs, scid)
                }

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

                return ogChanIDs, nil, nil

        case err != nil:
                return nil, nil, err
        }

        return newChanIDs, knownZombies, 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 *KVStore) 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 errors.Is(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 *KVStore) 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 *KVStore) 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 *KVStore) delChannelEdgeUnsafe(edges, edgeIndex, chanIndex,
        zombieIndex kvdb.RwBucket, chanID []byte, isZombie,
        strictZombie bool) (*models.ChannelEdgeInfo, error) {

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

        // 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 nil, err
        }
        err = delEdgeUpdateIndexEntry(edges, cid, edge1, edge2)
        if err != nil {
                return nil, 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 nil, err
                }
        }
        copy(edgeKey[:33], edgeInfo.NodeKey2Bytes[:])
        if edges.Get(edgeKey[:]) != nil {
                if err := edges.Delete(edgeKey[:]); err != nil {
                        return nil, err
                }
        }

        // As part of deleting the edge we also remove all disabled entries
        // from the edgePolicyDisabledIndex bucket. We do that for both
        // directions.
        err = updateEdgePolicyDisabledIndex(edges, cid, false, false)
        if err != nil {
                return nil, err
        }
        err = updateEdgePolicyDisabledIndex(edges, cid, true, false)
        if err != nil {
                return nil, err
        }

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

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

        return &edgeInfo, 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 *KVStore) UpdateEdgePolicy(edge *models.ChannelEdgePolicy,
        op ...batch.SchedulerOption) (route.Vertex, route.Vertex, error) {

        var (
                isUpdate1    bool
                edgeNotFound bool
                from, to     route.Vertex
        )

        r := &batch.Request{
                Reset: func() {
                        isUpdate1 = false
                        edgeNotFound = false
                },
                Update: func(tx kvdb.RwTx) error {
                        var err error
                        from, to, isUpdate1, err = updateEdgePolicy(tx, edge)
                        if err != nil {
                                log.Errorf("UpdateEdgePolicy faild: %v", err)
                        }

                        // 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)
        }

        err := c.chanScheduler.Execute(r)

        return from, to, err
}

func (c *KVStore) 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) (
        route.Vertex, route.Vertex, bool, error) {

        var noVertex route.Vertex

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

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

        return fromNodePubKey, toNodePubKey, 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 *KVStore) 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 && !errors.Is(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 *KVStore) 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 *KVStore) 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 *KVStore) 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
}

// 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 *KVStore) 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 *KVStore) 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 *KVStore) 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 *KVStore) 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 *KVStore) 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 *KVStore) 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 errors.Is(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 *KVStore) 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 *KVStore) 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 *KVStore) 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)
                }

                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 *KVStore) 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 *KVStore) 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)

        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 *KVStore) 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 *KVStore) 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 *KVStore) 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 *KVStore) 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
}

// GraphSession will provide the call-back with access to a NodeTraverser
// instance which can be used to perform queries against the channel graph.
func (c *KVStore) GraphSession(cb func(graph NodeTraverser) error) error {
        return c.db.View(func(tx walletdb.ReadTx) error {
                return cb(&nodeTraverserSession{
                        db: c,
                        tx: tx,
                })
        }, func() {})
}

// nodeTraverserSession implements the NodeTraverser interface but with a
// backing read only transaction for a consistent view of the graph.
type nodeTraverserSession struct {
        tx kvdb.RTx
        db *KVStore
}

// ForEachNodeDirectedChannel calls the callback for every channel of the given
// node.
//
// NOTE: Part of the NodeTraverser interface.
func (c *nodeTraverserSession) ForEachNodeDirectedChannel(nodePub route.Vertex,
        cb func(channel *DirectedChannel) error) error {

        return c.db.forEachNodeDirectedChannel(c.tx, nodePub, cb)
}

// FetchNodeFeatures returns the features of the given node. If the node is
// unknown, assume no additional features are supported.
//
// NOTE: Part of the NodeTraverser interface.
func (c *nodeTraverserSession) FetchNodeFeatures(nodePub route.Vertex) (
        *lnwire.FeatureVector, error) {

        return c.db.fetchNodeFeatures(c.tx, nodePub)
}

func putLightningNode(nodeBucket, aliasBucket, 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) (route.Vertex,
        *lnwire.FeatureVector, error) {

        var (
                pubKey      route.Vertex
                features    = lnwire.EmptyFeatureVector()
                nodeScratch [8]byte
        )

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

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

        // Read the node announcement flag.
        if _, err := r.Read(nodeScratch[:2]); err != nil {
                return pubKey, 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 pubKey, features, 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 pubKey, nil, err
        }
        if err := binary.Read(r, byteOrder, &rgb); err != nil {
                return pubKey, nil, err
        }
        if err := binary.Read(r, byteOrder, &rgb); err != nil {
                return pubKey, nil, err
        }

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

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

        return pubKey, features, 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 errors.Is(err, io.ErrUnexpectedEOF):
        case errors.Is(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 errors.Is(err, io.ErrUnexpectedEOF):
        case errors.Is(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 &&
                        !errors.Is(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
        }

        err = updateEdgePolicyDisabledIndex(
                edges, edge.ChannelID,
                edge.ChannelFlags&lnwire.ChanUpdateDirection > 0,
                edge.IsDisabled(),
        )
        if err != nil {
                return err
        }

        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 errors.Is(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 &&
                !errors.Is(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 errors.Is(err, io.ErrUnexpectedEOF):
        case errors.Is(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
}

// chanGraphNodeTx is an implementation of the NodeRTx interface backed by the
// KVStore and a kvdb.RTx.
type chanGraphNodeTx struct {
        tx   kvdb.RTx
        db   *KVStore
        node *models.LightningNode
}

// A compile-time constraint to ensure chanGraphNodeTx implements the NodeRTx
// interface.
var _ NodeRTx = (*chanGraphNodeTx)(nil)

func newChanGraphNodeTx(tx kvdb.RTx, db *KVStore,
        node *models.LightningNode) *chanGraphNodeTx {

        return &chanGraphNodeTx{
                tx:   tx,
                db:   db,
                node: node,
        }
}

// Node returns the raw information of the node.
//
// NOTE: This is a part of the NodeRTx interface.
func (c *chanGraphNodeTx) Node() *models.LightningNode {
        return c.node
}

// FetchNode fetches the node with the given pub key under the same transaction
// used to fetch the current node. The returned node is also a NodeRTx and any
// operations on that NodeRTx will also be done under the same transaction.
//
// NOTE: This is a part of the NodeRTx interface.
func (c *chanGraphNodeTx) FetchNode(nodePub route.Vertex) (NodeRTx, error) {
        node, err := c.db.FetchLightningNodeTx(c.tx, nodePub)
        if err != nil {
                return nil, err
        }

        return newChanGraphNodeTx(c.tx, c.db, node), nil
}

// ForEachChannel can be used to iterate over the node's channels under
// the same transaction used to fetch the node.
//
// NOTE: This is a part of the NodeRTx interface.
func (c *chanGraphNodeTx) ForEachChannel(f func(*models.ChannelEdgeInfo,
        *models.ChannelEdgePolicy, *models.ChannelEdgePolicy) error) error {

        return c.db.ForEachNodeChannelTx(c.tx, c.node.PubKeyBytes,
                func(_ kvdb.RTx, info *models.ChannelEdgeInfo, policy1,
                        policy2 *models.ChannelEdgePolicy) error {

                        return f(info, policy1, policy2)
                },
        )
}

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

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

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

                return nil, err
        }

        graph, err := NewChannelGraph(&Config{
                KVDB:        backend,
                KVStoreOpts: modifiers,
        })
        if err != nil {
                backendCleanup()

                return nil, err
        }
        require.NoError(t, graph.Start())

        t.Cleanup(func() {
                _ = backend.Close()
                backendCleanup()
                require.NoError(t, graph.Stop())
        })

        return graph, nil
}

lightningnetwork / lnd / 13566028875

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