17830307614

Committed 18 Sep 2025 01:29PM UTC coverage: 54.617% (-12.0%) from 66.637%

Build # 17830307614

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Pull #10200

github

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web-flow

Commit Message

Merge 181a0a7bc into b34fc964b

Pull Request Pull Request #10200: github: change to form-based issue template

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67.87

/chainntnfs/interface.go

package chainntnfs

import (
        "bytes"
        "encoding/hex"
        "errors"
        "fmt"
        "strings"
        "sync"

        "github.com/btcsuite/btcd/blockchain"
        "github.com/btcsuite/btcd/btcjson"
        "github.com/btcsuite/btcd/btcutil"
        "github.com/btcsuite/btcd/chaincfg/chainhash"
        "github.com/btcsuite/btcd/wire"
        "github.com/lightningnetwork/lnd/fn/v2"
)

var (
        // ErrChainNotifierShuttingDown is used when we are trying to
        // measure a spend notification when notifier is already stopped.
        ErrChainNotifierShuttingDown = errors.New("chain notifier shutting down")
)

// TxConfStatus denotes the status of a transaction's lookup.
type TxConfStatus uint8

const (
        // TxFoundMempool denotes that the transaction was found within the
        // backend node's mempool.
        TxFoundMempool TxConfStatus = iota

        // TxFoundIndex denotes that the transaction was found within the
        // backend node's txindex.
        TxFoundIndex

        // TxNotFoundIndex denotes that the transaction was not found within the
        // backend node's txindex.
        TxNotFoundIndex

        // TxFoundManually denotes that the transaction was found within the
        // chain by scanning for it manually.
        TxFoundManually

        // TxNotFoundManually denotes that the transaction was not found within
        // the chain by scanning for it manually.
        TxNotFoundManually
)

// String returns the string representation of the TxConfStatus.
func (t TxConfStatus) String() string {
        switch t {
        case TxFoundMempool:
                return "TxFoundMempool"

        case TxFoundIndex:
                return "TxFoundIndex"

        case TxNotFoundIndex:
                return "TxNotFoundIndex"

        case TxFoundManually:
                return "TxFoundManually"

        case TxNotFoundManually:
                return "TxNotFoundManually"

        default:
                return "unknown"
        }
}

// NotifierOptions is a set of functional options that allow callers to further
// modify the type of chain event notifications they receive.
type NotifierOptions struct {
        // IncludeBlock if true, then the dispatched confirmation notification
        // will include the block that mined the transaction.
        IncludeBlock bool
}

// DefaultNotifierOptions returns the set of default options for the notifier.
func DefaultNotifierOptions() *NotifierOptions {
        return &NotifierOptions{}
}

// NotifierOption is a functional option that allows a caller to modify the
// events received from the notifier.
type NotifierOption func(*NotifierOptions)

// WithIncludeBlock is an optional argument that allows the caller to specify
// that the block that mined a transaction should be included in the response.
func WithIncludeBlock() NotifierOption {
        return func(o *NotifierOptions) {
                o.IncludeBlock = true
        }
}

// ChainNotifier represents a trusted source to receive notifications concerning
// targeted events on the Bitcoin blockchain. The interface specification is
// intentionally general in order to support a wide array of chain notification
// implementations such as: btcd's websockets notifications, Bitcoin Core's
// ZeroMQ notifications, various Bitcoin API services, Electrum servers, etc.
//
// Concrete implementations of ChainNotifier should be able to support multiple
// concurrent client requests, as well as multiple concurrent notification events.
type ChainNotifier interface {
        // RegisterConfirmationsNtfn registers an intent to be notified once
        // txid reaches numConfs confirmations. We also pass in the pkScript as
        // the default light client instead needs to match on scripts created in
        // the block. If a nil txid is passed in, then not only should we match
        // on the script, but we should also dispatch once the transaction
        // containing the script reaches numConfs confirmations. This can be
        // useful in instances where we only know the script in advance, but not
        // the transaction containing it.
        //
        // The returned ConfirmationEvent should properly notify the client once
        // the specified number of confirmations has been reached for the txid,
        // as well as if the original tx gets re-org'd out of the mainchain. The
        // heightHint parameter is provided as a convenience to light clients.
        // It heightHint denotes the earliest height in the blockchain in which
        // the target txid _could_ have been included in the chain. This can be
        // used to bound the search space when checking to see if a notification
        // can immediately be dispatched due to historical data.
        //
        // NOTE: Dispatching notifications to multiple clients subscribed to
        // the same (txid, numConfs) tuple MUST be supported.
        RegisterConfirmationsNtfn(txid *chainhash.Hash, pkScript []byte,
                numConfs, heightHint uint32,
                opts ...NotifierOption) (*ConfirmationEvent, error)

        // RegisterSpendNtfn registers an intent to be notified once the target
        // outpoint is successfully spent within a transaction. The script that
        // the outpoint creates must also be specified. This allows this
        // interface to be implemented by BIP 158-like filtering. If a nil
        // outpoint is passed in, then not only should we match on the script,
        // but we should also dispatch once a transaction spends the output
        // containing said script. This can be useful in instances where we only
        // know the script in advance, but not the outpoint itself.
        //
        // The returned SpendEvent will receive a send on the 'Spend'
        // transaction once a transaction spending the input is detected on the
        // blockchain. The heightHint parameter is provided as a convenience to
        // light clients. It denotes the earliest height in the blockchain in
        // which the target output could have been spent.
        //
        // NOTE: The notification should only be triggered when the spending
        // transaction receives a single confirmation.
        //
        // NOTE: Dispatching notifications to multiple clients subscribed to a
        // spend of the same outpoint MUST be supported.
        RegisterSpendNtfn(outpoint *wire.OutPoint, pkScript []byte,
                heightHint uint32) (*SpendEvent, error)

        // RegisterBlockEpochNtfn registers an intent to be notified of each
        // new block connected to the tip of the main chain. The returned
        // BlockEpochEvent struct contains a channel which will be sent upon
        // for each new block discovered.
        //
        // Clients have the option of passing in their best known block.
        // If they specify a block, the ChainNotifier checks whether the client
        // is behind on blocks. If they are, the ChainNotifier sends a backlog
        // of block notifications for the missed blocks. If they do not provide
        // one, then a notification will be dispatched immediately for the
        // current tip of the chain upon a successful registration.
        RegisterBlockEpochNtfn(*BlockEpoch) (*BlockEpochEvent, error)

        // Start the ChainNotifier. Once started, the implementation should be
        // ready, and able to receive notification registrations from clients.
        Start() error

        // Started returns true if this instance has been started, and false otherwise.
        Started() bool

        // Stops the concrete ChainNotifier. Once stopped, the ChainNotifier
        // should disallow any future requests from potential clients.
        // Additionally, all pending client notifications will be canceled
        // by closing the related channels on the *Event's.
        Stop() error
}

// TxConfirmation carries some additional block-level details of the exact
// block that specified transactions was confirmed within.
type TxConfirmation struct {
        // BlockHash is the hash of the block that confirmed the original
        // transition.
        BlockHash *chainhash.Hash

        // BlockHeight is the height of the block in which the transaction was
        // confirmed within.
        BlockHeight uint32

        // TxIndex is the index within the block of the ultimate confirmed
        // transaction.
        TxIndex uint32

        // Tx is the transaction for which the notification was requested for.
        Tx *wire.MsgTx

        // Block is the block that contains the transaction referenced above.
        //
        // NOTE: This is only specified if the confirmation request opts to
        // have the response include the block itself.
        Block *wire.MsgBlock
}

// TxUpdateInfo contains information about a transaction before it has reached
// its required number of confirmations. Transactions are registered for
// notification for a specific number of "required" confirmations, this struct
// will update the caller incrementally after each new block is found as long as
// the transaction is not yet fully regarded as confirmed.
type TxUpdateInfo struct {
        // BlockHeight is the height of the block that contains the transaction.
        BlockHeight uint32

        // NumConfsLeft is the number of confirmations left for the transaction
        // to be regarded as fully confirmed.
        NumConfsLeft uint32
}

// ConfirmationEvent encapsulates a confirmation notification. With this struct,
// callers can be notified of: the instance the target txid reaches the targeted
// number of confirmations, how many confirmations are left for the target txid
// to be fully confirmed at every new block height, and also in the event that
// the original txid becomes disconnected from the blockchain as a result of a
// re-org.
//
// Once the txid reaches the specified number of confirmations, the 'Confirmed'
// channel will be sent upon fulfilling the notification.
//
// If the event that the original transaction becomes re-org'd out of the main
// chain, the 'NegativeConf' will be sent upon with a value representing the
// depth of the re-org.
//
// NOTE: If the caller wishes to cancel their registered spend notification,
// the Cancel closure MUST be called.
type ConfirmationEvent struct {
        // Confirmed is a channel that will be sent upon once the transaction
        // has been fully confirmed. The struct sent will contain all the
        // details of the channel's confirmation.
        //
        // NOTE: This channel must be buffered.
        Confirmed chan *TxConfirmation

        // Updates is a channel that will sent upon, at every incremental
        // confirmation, how many confirmations are left to declare the
        // transaction as fully confirmed, along with the height of the block
        // that contains the transaction.
        //
        // NOTE: This channel must be buffered with the number of required
        // confirmations.
        Updates chan TxUpdateInfo

        // NegativeConf is a channel that will be sent upon if the transaction
        // confirms, but is later reorged out of the chain. The integer sent
        // through the channel represents the reorg depth.
        //
        // NOTE: This channel must be buffered.
        NegativeConf chan int32

        // Done is a channel that gets sent upon once the confirmation request
        // is no longer under the risk of being reorged out of the chain.
        //
        // NOTE: This channel must be buffered.
        Done chan struct{}

        // Cancel is a closure that should be executed by the caller in the case
        // that they wish to prematurely abandon their registered confirmation
        // notification.
        Cancel func()
}

// NewConfirmationEvent constructs a new ConfirmationEvent with newly opened
// channels.
func NewConfirmationEvent(numConfs uint32, cancel func()) *ConfirmationEvent {
        return &ConfirmationEvent{
                // We cannot rely on the subscriber to immediately read from
                // the channel so we need to create a larger buffer to avoid
                // blocking the notifier.
                Confirmed:    make(chan *TxConfirmation, 1),
                Updates:      make(chan TxUpdateInfo, numConfs),
                NegativeConf: make(chan int32, 1),
                Done:         make(chan struct{}, 1),
                Cancel:       cancel,
        }
}

// SpendDetail contains details pertaining to a spent output. This struct itself
// is the spentness notification. It includes the original outpoint which triggered
// the notification, the hash of the transaction spending the output, the
// spending transaction itself, and finally the input index which spent the
// target output.
type SpendDetail struct {
        SpentOutPoint     *wire.OutPoint
        SpenderTxHash     *chainhash.Hash
        SpendingTx        *wire.MsgTx
        SpenderInputIndex uint32
        SpendingHeight    int32
}

// HasSpenderWitness returns true if the spending transaction has non-empty
// witness.
func (s *SpendDetail) HasSpenderWitness() bool {
        tx := s.SpendingTx

        // If there are no inputs, then there is no witness.
        if len(tx.TxIn) == 0 {
                return false
        }

        // If the spender input index is larger than the number of inputs, then
        // we don't have a witness and this is an error case so we log it.
        if uint32(len(tx.TxIn)) <= s.SpenderInputIndex {
                Log.Errorf("SpenderInputIndex %d is out of range for tx %v",
                        s.SpenderInputIndex, tx.TxHash())

                return false
        }

        // If the witness is empty, then there is no witness.
        if len(tx.TxIn[s.SpenderInputIndex].Witness) == 0 {
                return false
        }

        // If the witness is non-empty, then we have a witness.
        return true
}

// String returns a string representation of SpendDetail.
func (s *SpendDetail) String() string {
        return fmt.Sprintf("%v[%d] spending %v at height=%v", s.SpenderTxHash,
                s.SpenderInputIndex, s.SpentOutPoint, s.SpendingHeight)
}

// SpendEvent encapsulates a spentness notification. Its only field 'Spend' will
// be sent upon once the target output passed into RegisterSpendNtfn has been
// spent on the blockchain.
//
// NOTE: If the caller wishes to cancel their registered spend notification,
// the Cancel closure MUST be called.
type SpendEvent struct {
        // Spend is a receive only channel which will be sent upon once the
        // target outpoint has been spent.
        //
        // NOTE: This channel must be buffered.
        Spend chan *SpendDetail

        // Reorg is a channel that will be sent upon once we detect the spending
        // transaction of the outpoint in question has been reorged out of the
        // chain.
        //
        // NOTE: This channel must be buffered.
        Reorg chan struct{}

        // Done is a channel that gets sent upon once the confirmation request
        // is no longer under the risk of being reorged out of the chain.
        //
        // NOTE: This channel must be buffered.
        Done chan struct{}

        // Cancel is a closure that should be executed by the caller in the case
        // that they wish to prematurely abandon their registered spend
        // notification.
        Cancel func()
}

// NewSpendEvent constructs a new SpendEvent with newly opened channels.
func NewSpendEvent(cancel func()) *SpendEvent {
        return &SpendEvent{
                Spend:  make(chan *SpendDetail, 1),
                Reorg:  make(chan struct{}, 1),
                Done:   make(chan struct{}, 1),
                Cancel: cancel,
        }
}

// BlockEpoch represents metadata concerning each new block connected to the
// main chain.
type BlockEpoch struct {
        // Hash is the block hash of the latest block to be added to the tip of
        // the main chain.
        Hash *chainhash.Hash

        // Height is the height of the latest block to be added to the tip of
        // the main chain.
        Height int32

        // BlockHeader is the block header of this new height.
        BlockHeader *wire.BlockHeader
}

// BlockEpochEvent encapsulates an on-going stream of block epoch
// notifications. Its only field 'Epochs' will be sent upon for each new block
// connected to the main-chain.
//
// NOTE: If the caller wishes to cancel their registered block epoch
// notification, the Cancel closure MUST be called.
type BlockEpochEvent struct {
        // Epochs is a receive only channel that will be sent upon each time a
        // new block is connected to the end of the main chain.
        //
        // NOTE: This channel must be buffered.
        Epochs <-chan *BlockEpoch

        // Cancel is a closure that should be executed by the caller in the case
        // that they wish to abandon their registered block epochs notification.
        Cancel func()
}

// NotifierDriver represents a "driver" for a particular interface. A driver is
// identified by a globally unique string identifier along with a 'New()'
// method which is responsible for initializing a particular ChainNotifier
// concrete implementation.
type NotifierDriver struct {
        // NotifierType is a string which uniquely identifies the ChainNotifier
        // that this driver, drives.
        NotifierType string

        // New creates a new instance of a concrete ChainNotifier
        // implementation given a variadic set up arguments. The function takes
        // a variadic number of interface parameters in order to provide
        // initialization flexibility, thereby accommodating several potential
        // ChainNotifier implementations.
        New func(args ...interface{}) (ChainNotifier, error)
}

var (
        notifiers   = make(map[string]*NotifierDriver)
        registerMtx sync.Mutex
)

// RegisteredNotifiers returns a slice of all currently registered notifiers.
//
// NOTE: This function is safe for concurrent access.
func RegisteredNotifiers() []*NotifierDriver {
        registerMtx.Lock()
        defer registerMtx.Unlock()

        drivers := make([]*NotifierDriver, 0, len(notifiers))
        for _, driver := range notifiers {
                drivers = append(drivers, driver)
        }

        return drivers
}

// RegisterNotifier registers a NotifierDriver which is capable of driving a
// concrete ChainNotifier interface. In the case that this driver has already
// been registered, an error is returned.
//
// NOTE: This function is safe for concurrent access.
func RegisterNotifier(driver *NotifierDriver) error {
        registerMtx.Lock()
        defer registerMtx.Unlock()

        if _, ok := notifiers[driver.NotifierType]; ok {
                return fmt.Errorf("notifier already registered")
        }

        notifiers[driver.NotifierType] = driver

        return nil
}

// SupportedNotifiers returns a slice of strings that represent the database
// drivers that have been registered and are therefore supported.
//
// NOTE: This function is safe for concurrent access.
func SupportedNotifiers() []string {
        registerMtx.Lock()
        defer registerMtx.Unlock()

        supportedNotifiers := make([]string, 0, len(notifiers))
        for driverName := range notifiers {
                supportedNotifiers = append(supportedNotifiers, driverName)
        }

        return supportedNotifiers
}

// ChainConn enables notifiers to pass in their chain backend to interface
// functions that require it.
type ChainConn interface {
        // GetBlockHeader returns the block header for a hash.
        GetBlockHeader(blockHash *chainhash.Hash) (*wire.BlockHeader, error)

        // GetBlockHeaderVerbose returns the verbose block header for a hash.
        GetBlockHeaderVerbose(blockHash *chainhash.Hash) (
                *btcjson.GetBlockHeaderVerboseResult, error)

        // GetBlockHash returns the hash from a block height.
        GetBlockHash(blockHeight int64) (*chainhash.Hash, error)
}

// GetCommonBlockAncestorHeight takes in:
// (1) the hash of a block that has been reorged out of the main chain
// (2) the hash of the block of the same height from the main chain
// It returns the height of the nearest common ancestor between the two hashes,
// or an error
func GetCommonBlockAncestorHeight(chainConn ChainConn, reorgHash,
        chainHash chainhash.Hash) (int32, error) {

        for reorgHash != chainHash {
                reorgHeader, err := chainConn.GetBlockHeader(&reorgHash)
                if err != nil {
                        return 0, fmt.Errorf("unable to get header for "+
                                "hash=%v: %w", reorgHash, err)
                }
                chainHeader, err := chainConn.GetBlockHeader(&chainHash)
                if err != nil {
                        return 0, fmt.Errorf("unable to get header for "+
                                "hash=%v: %w", chainHash, err)
                }
                reorgHash = reorgHeader.PrevBlock
                chainHash = chainHeader.PrevBlock
        }

        verboseHeader, err := chainConn.GetBlockHeaderVerbose(&chainHash)
        if err != nil {
                return 0, fmt.Errorf("unable to get verbose header for "+
                        "hash=%v: %w", chainHash, err)
        }

        return verboseHeader.Height, nil
}

// GetClientMissedBlocks uses a client's best block to determine what blocks
// it missed being notified about, and returns them in a slice. Its
// backendStoresReorgs parameter tells it whether or not the notifier's
// chainConn stores information about blocks that have been reorged out of the
// chain, which allows GetClientMissedBlocks to find out whether the client's
// best block has been reorged out of the chain, rewind to the common ancestor
// and return blocks starting right after the common ancestor.
func GetClientMissedBlocks(chainConn ChainConn, clientBestBlock *BlockEpoch,
        notifierBestHeight int32, backendStoresReorgs bool) ([]BlockEpoch, error) {

        startingHeight := clientBestBlock.Height
        if backendStoresReorgs {
                // If a reorg causes the client's best hash to be incorrect,
                // retrieve the closest common ancestor and dispatch
                // notifications from there.
                hashAtBestHeight, err := chainConn.GetBlockHash(
                        int64(clientBestBlock.Height))
                if err != nil {
                        return nil, fmt.Errorf("unable to find blockhash for "+
                                "height=%d: %v", clientBestBlock.Height, err)
                }

                startingHeight, err = GetCommonBlockAncestorHeight(
                        chainConn, *clientBestBlock.Hash, *hashAtBestHeight,
                )
                if err != nil {
                        return nil, fmt.Errorf("unable to find common ancestor: "+
                                "%v", err)
                }
        }

        // We want to start dispatching historical notifications from the block
        // right after the client's best block, to avoid a redundant notification.
        missedBlocks, err := getMissedBlocks(
                chainConn, startingHeight+1, notifierBestHeight+1,
        )
        if err != nil {
                return nil, fmt.Errorf("unable to get missed blocks: %w", err)
        }

        return missedBlocks, nil
}

// RewindChain handles internal state updates for the notifier's TxNotifier. It
// has no effect if given a height greater than or equal to our current best
// known height. It returns the new best block for the notifier.
func RewindChain(chainConn ChainConn, txNotifier *TxNotifier,
        currBestBlock BlockEpoch, targetHeight int32) (BlockEpoch, error) {

        newBestBlock := BlockEpoch{
                Height:      currBestBlock.Height,
                Hash:        currBestBlock.Hash,
                BlockHeader: currBestBlock.BlockHeader,
        }

        for height := currBestBlock.Height; height > targetHeight; height-- {
                hash, err := chainConn.GetBlockHash(int64(height - 1))
                if err != nil {
                        return newBestBlock, fmt.Errorf("unable to "+
                                "find blockhash for disconnected height=%d: %v",
                                height, err)
                }
                header, err := chainConn.GetBlockHeader(hash)
                if err != nil {
                        return newBestBlock, fmt.Errorf("unable to get block "+
                                "header for height=%v", height-1)
                }

                Log.Infof("Block disconnected from main chain: "+
                        "height=%v, sha=%v", height, newBestBlock.Hash)

                err = txNotifier.DisconnectTip(uint32(height))
                if err != nil {
                        return newBestBlock, fmt.Errorf("unable to "+
                                " disconnect tip for height=%d: %v",
                                height, err)
                }
                newBestBlock.Height = height - 1
                newBestBlock.Hash = hash
                newBestBlock.BlockHeader = header
        }

        return newBestBlock, nil
}

// HandleMissedBlocks is called when the chain backend for a notifier misses a
// series of blocks, handling a reorg if necessary. Its backendStoresReorgs
// parameter tells it whether or not the notifier's chainConn stores
// information about blocks that have been reorged out of the chain, which allows
// HandleMissedBlocks to check whether the notifier's best block has been
// reorged out, and rewind the chain accordingly. It returns the best block for
// the notifier and a slice of the missed blocks. The new best block needs to be
// returned in case a chain rewind occurs and partially completes before
// erroring. In the case where there is no rewind, the notifier's
// current best block is returned.
func HandleMissedBlocks(chainConn ChainConn, txNotifier *TxNotifier,
        currBestBlock BlockEpoch, newHeight int32,
        backendStoresReorgs bool) (BlockEpoch, []BlockEpoch, error) {

        startingHeight := currBestBlock.Height

        if backendStoresReorgs {
                // If a reorg causes our best hash to be incorrect, rewind the
                // chain so our best block is set to the closest common
                // ancestor, then dispatch notifications from there.
                hashAtBestHeight, err := chainConn.GetBlockHash(
                        int64(currBestBlock.Height),
                )
                if err != nil {
                        return currBestBlock, nil, fmt.Errorf("unable to find "+
                                "blockhash for height=%d: %v",
                                currBestBlock.Height, err)
                }

                startingHeight, err = GetCommonBlockAncestorHeight(
                        chainConn, *currBestBlock.Hash, *hashAtBestHeight,
                )
                if err != nil {
                        return currBestBlock, nil, fmt.Errorf("unable to find "+
                                "common ancestor: %v", err)
                }

                currBestBlock, err = RewindChain(
                        chainConn, txNotifier, currBestBlock, startingHeight,
                )
                if err != nil {
                        return currBestBlock, nil, fmt.Errorf("unable to "+
                                "rewind chain: %v", err)
                }
        }

        // We want to start dispatching historical notifications from the block
        // right after our best block, to avoid a redundant notification.
        missedBlocks, err := getMissedBlocks(chainConn, startingHeight+1, newHeight)
        if err != nil {
                return currBestBlock, nil, fmt.Errorf("unable to get missed "+
                        "blocks: %v", err)
        }

        return currBestBlock, missedBlocks, nil
}

// getMissedBlocks returns a slice of blocks: [startingHeight, endingHeight)
// fetched from the chain.
func getMissedBlocks(chainConn ChainConn, startingHeight,
        endingHeight int32) ([]BlockEpoch, error) {

        numMissedBlocks := endingHeight - startingHeight
        if numMissedBlocks < 0 {
                return nil, fmt.Errorf("starting height %d is greater than "+
                        "ending height %d", startingHeight, endingHeight)
        }

        missedBlocks := make([]BlockEpoch, 0, numMissedBlocks)
        for height := startingHeight; height < endingHeight; height++ {
                hash, err := chainConn.GetBlockHash(int64(height))
                if err != nil {
                        return nil, fmt.Errorf("unable to find blockhash for "+
                                "height=%d: %v", height, err)
                }
                header, err := chainConn.GetBlockHeader(hash)
                if err != nil {
                        return nil, fmt.Errorf("unable to find block header "+
                                "for height=%d: %v", height, err)
                }

                missedBlocks = append(
                        missedBlocks,
                        BlockEpoch{
                                Hash:        hash,
                                Height:      height,
                                BlockHeader: header,
                        },
                )
        }

        return missedBlocks, nil
}

// TxIndexConn abstracts an RPC backend with txindex enabled.
type TxIndexConn interface {
        // GetRawTransactionVerbose returns the transaction identified by the
        // passed chain hash, and returns additional information such as the
        // block that the transaction confirmed.
        GetRawTransactionVerbose(*chainhash.Hash) (*btcjson.TxRawResult, error)

        // GetBlock returns the block identified by the chain hash.
        GetBlock(*chainhash.Hash) (*wire.MsgBlock, error)
}

// ConfDetailsFromTxIndex looks up whether a transaction is already included in
// a block in the active chain by using the backend node's transaction index.
// If the transaction is found its TxConfStatus is returned. If it was found in
// the mempool this will be TxFoundMempool, if it is found in a block this will
// be TxFoundIndex. Otherwise TxNotFoundIndex is returned. If the tx is found
// in a block its confirmation details are also returned.
func ConfDetailsFromTxIndex(chainConn TxIndexConn, r ConfRequest,
        txNotFoundErr string) (*TxConfirmation, TxConfStatus, error) {

        // If the transaction has some or all of its confirmations required,
        // then we may be able to dispatch it immediately.
        rawTxRes, err := chainConn.GetRawTransactionVerbose(&r.TxID)
        if err != nil {
                // If the transaction lookup was successful, but it wasn't found
                // within the index itself, then we can exit early. We'll also
                // need to look at the error message returned as the error code
                // is used for multiple errors.
                jsonErr, ok := err.(*btcjson.RPCError)
                if ok && jsonErr.Code == btcjson.ErrRPCNoTxInfo &&
                        strings.Contains(jsonErr.Message, txNotFoundErr) {

                        return nil, TxNotFoundIndex, nil
                }

                return nil, TxNotFoundIndex,
                        fmt.Errorf("unable to query for txid %v: %w",
                                r.TxID, err)
        }

        // Deserialize the hex-encoded transaction to include it in the
        // confirmation details.
        rawTx, err := hex.DecodeString(rawTxRes.Hex)
        if err != nil {
                return nil, TxNotFoundIndex,
                        fmt.Errorf("unable to deserialize tx %v: %w",
                                r.TxID, err)
        }
        var tx wire.MsgTx
        if err := tx.Deserialize(bytes.NewReader(rawTx)); err != nil {
                return nil, TxNotFoundIndex,
                        fmt.Errorf("unable to deserialize tx %v: %w",
                                r.TxID, err)
        }

        // Ensure the transaction matches our confirmation request in terms of
        // txid and pkscript.
        if !r.MatchesTx(&tx) {
                return nil, TxNotFoundIndex,
                        fmt.Errorf("unable to locate tx %v", r.TxID)
        }

        // Make sure we actually retrieved a transaction that is included in a
        // block. If not, the transaction must be unconfirmed (in the mempool),
        // and we'll return TxFoundMempool together with a nil TxConfirmation.
        if rawTxRes.BlockHash == "" {
                return nil, TxFoundMempool, nil
        }

        // As we need to fully populate the returned TxConfirmation struct,
        // grab the block in which the transaction was confirmed so we can
        // locate its exact index within the block.
        blockHash, err := chainhash.NewHashFromStr(rawTxRes.BlockHash)
        if err != nil {
                return nil, TxNotFoundIndex,
                        fmt.Errorf("unable to get block hash %v for "+
                                "historical dispatch: %w", rawTxRes.BlockHash,
                                err)
        }
        block, err := chainConn.GetBlock(blockHash)
        if err != nil {
                return nil, TxNotFoundIndex,
                        fmt.Errorf("unable to get block with hash %v for "+
                                "historical dispatch: %w", blockHash, err)
        }

        // In the modern chain (the only one we really care about for LN), the
        // coinbase transaction of all blocks will include the block height.
        // Therefore we can save another query, and just use that height
        // directly.
        blockHeight, err := blockchain.ExtractCoinbaseHeight(
                btcutil.NewTx(block.Transactions[0]),
        )
        if err != nil {
                return nil, TxNotFoundIndex, fmt.Errorf("unable to extract "+
                        "coinbase height: %w", err)
        }

        // If the block was obtained, locate the transaction's index within the
        // block so we can give the subscriber full confirmation details.
        for txIndex, blockTx := range block.Transactions {
                if blockTx.TxHash() != r.TxID {
                        continue
                }

                return &TxConfirmation{
                        Tx:          tx.Copy(),
                        BlockHash:   blockHash,
                        BlockHeight: uint32(blockHeight),
                        TxIndex:     uint32(txIndex),
                        Block:       block,
                }, TxFoundIndex, nil
        }

        // We return an error because we should have found the transaction
        // within the block, but didn't.
        return nil, TxNotFoundIndex, fmt.Errorf("unable to locate "+
                "tx %v in block %v", r.TxID, blockHash)
}

// SpendHintCache is an interface whose duty is to cache spend hints for
// outpoints. A spend hint is defined as the earliest height in the chain at
// which an outpoint could have been spent within.
type SpendHintCache interface {
        // CommitSpendHint commits a spend hint for the outpoints to the cache.
        CommitSpendHint(height uint32, spendRequests ...SpendRequest) error

        // QuerySpendHint returns the latest spend hint for an outpoint.
        // ErrSpendHintNotFound is returned if a spend hint does not exist
        // within the cache for the outpoint.
        QuerySpendHint(spendRequest SpendRequest) (uint32, error)

        // PurgeSpendHint removes the spend hint for the outpoints from the
        // cache.
        PurgeSpendHint(spendRequests ...SpendRequest) error
}

// ConfirmHintCache is an interface whose duty is to cache confirm hints for
// transactions. A confirm hint is defined as the earliest height in the chain
// at which a transaction could have been included in a block.
type ConfirmHintCache interface {
        // CommitConfirmHint commits a confirm hint for the transactions to the
        // cache.
        CommitConfirmHint(height uint32, confRequests ...ConfRequest) error

        // QueryConfirmHint returns the latest confirm hint for a transaction
        // hash. ErrConfirmHintNotFound is returned if a confirm hint does not
        // exist within the cache for the transaction hash.
        QueryConfirmHint(confRequest ConfRequest) (uint32, error)

        // PurgeConfirmHint removes the confirm hint for the transactions from
        // the cache.
        PurgeConfirmHint(confRequests ...ConfRequest) error
}

// MempoolWatcher defines an interface that allows the caller to query
// information in the mempool.
type MempoolWatcher interface {
        // SubscribeMempoolSpent allows the caller to register a subscription
        // to watch for a spend of an outpoint in the mempool.The event will be
        // dispatched once the outpoint is spent in the mempool.
        SubscribeMempoolSpent(op wire.OutPoint) (*MempoolSpendEvent, error)

        // CancelMempoolSpendEvent allows the caller to cancel a subscription to
        // watch for a spend of an outpoint in the mempool.
        CancelMempoolSpendEvent(sub *MempoolSpendEvent)

        // LookupInputMempoolSpend looks up the mempool to find a spending tx
        // which spends the given outpoint. A fn.None is returned if it's not
        // found.
        LookupInputMempoolSpend(op wire.OutPoint) fn.Option[wire.MsgTx]
}

lightningnetwork / lnd / 17830307614

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