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package sweep
import (
"context"
"fmt"
"github.com/btcsuite/btcd/btcec"
"github.com/btcsuite/btcd/txscript"
"github.com/btcsuite/btcd/wire"
"github.com/btcsuite/btcutil"
"github.com/lightninglabs/lndclient"
"github.com/lightninglabs/loop/swap"
"github.com/lightningnetwork/lnd/input"
"github.com/lightningnetwork/lnd/keychain"
)
// Sweeper creates htlc sweep txes.
type Sweeper struct {
Lnd *lndclient.LndServices
}
// CreateSweepTx creates an htlc sweep tx.
func (s *Sweeper) CreateSweepTx(
globalCtx context.Context, height int32, sequence uint32,
htlc *swap.Htlc, htlcOutpoint wire.OutPoint,
keyBytes [33]byte,
witnessFunc func(sig []byte) (wire.TxWitness, error),
amount, fee btcutil.Amount,
destAddr btcutil.Address) (*wire.MsgTx, error) {
// Compose tx.
sweepTx := wire.NewMsgTx(2)
sweepTx.LockTime = uint32(height)
// Add HTLC input.
sweepTx.AddTxIn(&wire.TxIn{
PreviousOutPoint: htlcOutpoint,
SignatureScript: htlc.SigScript,
Sequence: sequence,
})
// Add output for the destination address.
sweepPkScript, err := txscript.PayToAddrScript(destAddr)
if err != nil {
return nil, err
}
sweepTx.AddTxOut(&wire.TxOut{
PkScript: sweepPkScript,
Value: int64(amount - fee),
})
// Generate a signature for the swap htlc transaction.
key, err := btcec.ParsePubKey(keyBytes[:], btcec.S256())
if err != nil {
return nil, err
}
signDesc := lndclient.SignDescriptor{
WitnessScript: htlc.Script(),
Output: &wire.TxOut{
Value: int64(amount),
},
HashType: txscript.SigHashAll,
InputIndex: 0,
KeyDesc: keychain.KeyDescriptor{
PubKey: key,
},
}
rawSigs, err := s.Lnd.Signer.SignOutputRaw(
globalCtx, sweepTx, []*lndclient.SignDescriptor{&signDesc},
)
if err != nil {
return nil, fmt.Errorf("signing: %v", err)
}
sig := rawSigs[0]
// Add witness stack to the tx input.
sweepTx.TxIn[0].Witness, err = witnessFunc(sig)
if err != nil {
return nil, err
}
return sweepTx, nil
}
// GetSweepFee calculates the required tx fee to spend to P2WKH. It takes a
// function that is expected to add the weight of the input to the weight
// estimator.
func (s *Sweeper) GetSweepFee(ctx context.Context,
addInputEstimate func(*input.TxWeightEstimator),
destAddr btcutil.Address, sweepConfTarget int32) (
btcutil.Amount, error) {
// Get fee estimate from lnd.
feeRate, err := s.Lnd.WalletKit.EstimateFee(ctx, sweepConfTarget)
if err != nil {
return 0, fmt.Errorf("estimate fee: %v", err)
}
// Calculate weight for this tx.
var weightEstimate input.TxWeightEstimator
switch destAddr.(type) {
case *btcutil.AddressWitnessScriptHash:
weightEstimate.AddP2WSHOutput()
case *btcutil.AddressWitnessPubKeyHash:
weightEstimate.AddP2WKHOutput()
case *btcutil.AddressScriptHash:
weightEstimate.AddP2SHOutput()
case *btcutil.AddressPubKeyHash:
weightEstimate.AddP2PKHOutput()
default:
return 0, fmt.Errorf("unknown address type %T", destAddr)
}
addInputEstimate(&weightEstimate)
weight := weightEstimate.Weight()
return feeRate.FeeForWeight(int64(weight)), nil
}