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staticaddr: deposit state machine
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2 files changed

+381
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‎staticaddr/actions.go‎

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package staticaddr
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import (
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"errors"
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"fmt"
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"github.com/btcsuite/btcd/wire"
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"github.com/lightninglabs/lndclient"
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"github.com/lightninglabs/loop/fsm"
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"github.com/lightninglabs/loop/staticaddr/script"
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)
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const (
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defaultConfTarget = 3
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)
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// PublishExpiredDepositAction creates and publishes the timeout transaction
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// that spends the deposit from the static address timeout leaf to the
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// predefined timeout sweep pkscript.
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func (f *FSM) PublishExpiredDepositAction(_ fsm.EventContext) fsm.EventType {
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msgTx := wire.NewMsgTx(2)
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// Add the deposit outpoint as input to the transaction.
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msgTx.AddTxIn(&wire.TxIn{
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PreviousOutPoint: f.deposit.OutPoint,
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Sequence: f.addressParameters.Expiry,
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SignatureScript: nil,
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})
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// Estimate the fee rate of an expiry spend transaction.
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feeRateEstimator, err := f.cfg.WalletKit.EstimateFeeRate(
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f.ctx, defaultConfTarget,
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)
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if err != nil {
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return f.HandleError(fmt.Errorf("timeout sweep fee "+
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"estimation failed: %v", err))
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}
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weight := script.ExpirySpendWeight()
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fee := feeRateEstimator.FeeForWeight(weight)
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// We cap the fee at 20% of the deposit value.
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if fee > f.deposit.Value/5 {
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return f.HandleError(errors.New("fee is greater than 20% of " +
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"the deposit value"))
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}
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output := &wire.TxOut{
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Value: int64(f.deposit.Value - fee),
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PkScript: f.deposit.TimeOutSweepPkScript,
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}
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msgTx.AddTxOut(output)
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txOut := &wire.TxOut{
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Value: int64(f.deposit.Value),
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PkScript: f.addressParameters.PkScript,
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}
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prevOut := []*wire.TxOut{txOut}
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signDesc, err := f.SignDescriptor()
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if err != nil {
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return f.HandleError(err)
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}
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rawSigs, err := f.cfg.Signer.SignOutputRaw(
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f.ctx, msgTx, []*lndclient.SignDescriptor{&signDesc}, prevOut,
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)
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if err != nil {
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return f.HandleError(err)
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}
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sig := rawSigs[0]
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msgTx.TxIn[0].Witness, err = f.staticAddress.GenTimeoutWitness(sig)
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if err != nil {
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return f.HandleError(err)
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}
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err = f.cfg.WalletKit.PublishTransaction(
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f.ctx, msgTx, f.deposit.OutPoint.Hash.String()+"-close-sweep",
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)
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if err != nil {
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return f.HandleError(err)
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}
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f.Debugf("published timeout sweep with txid: %v", msgTx.TxHash())
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return OnExpiryPublished
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}
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// WaitForExpirySweepAction waits for a sufficient number of confirmations
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// before a timeout sweep is considered successful.
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func (f *FSM) WaitForExpirySweepAction(_ fsm.EventContext) fsm.EventType {
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spendChan, errSpendChan, err := f.cfg.ChainNotifier.RegisterConfirmationsNtfn( //nolint:lll
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f.ctx, nil, f.deposit.TimeOutSweepPkScript, defaultConfTarget,
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int32(f.deposit.ConfirmationHeight),
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)
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if err != nil {
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return f.HandleError(err)
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}
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select {
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case err := <-errSpendChan:
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log.Debugf("spend expired deposit error: %v", err)
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return fsm.OnError
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case <-spendChan:
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return OnExpirySwept
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case <-f.ctx.Done():
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return fsm.OnError
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}
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}
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// SweptExpiredDepositAction is the final action of the FSM. It signals to the
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// manager that the deposit has been swept and the FSM can be removed. It also
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// ends the state machine main loop by cancelling its context.
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func (f *FSM) SweptExpiredDepositAction(_ fsm.EventContext) fsm.EventType {
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select {
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case <-f.ctx.Done():
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return fsm.OnError
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default:
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f.finalizedDepositChan <- f.deposit.OutPoint
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f.ctx.Done()
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}
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return fsm.NoOp
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}

‎staticaddr/fsm.go‎

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package staticaddr
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import (
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"context"
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"github.com/btcsuite/btcd/txscript"
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"github.com/btcsuite/btcd/wire"
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"github.com/lightninglabs/lndclient"
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"github.com/lightninglabs/loop/fsm"
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"github.com/lightninglabs/loop/staticaddr/script"
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"github.com/lightningnetwork/lnd/input"
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"github.com/lightningnetwork/lnd/keychain"
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)
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const (
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DefaultObserverSize = 20
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)
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// States.
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var (
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Deposited = fsm.StateType("Deposited")
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PublishExpiredDeposit = fsm.StateType("PublishExpiredDeposit")
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WaitForExpirySweep = fsm.StateType("WaitForExpirySweep")
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SweptExpiredDeposit = fsm.StateType("SweptExpiredDeposit")
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Failed = fsm.StateType("DepositFailed")
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)
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// Events.
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var (
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OnStart = fsm.EventType("OnStart")
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OnExpiry = fsm.EventType("OnExpiry")
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OnExpiryPublished = fsm.EventType("OnExpiryPublished")
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OnExpirySwept = fsm.EventType("OnExpirySwept")
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OnRecover = fsm.EventType("OnRecover")
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)
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// FSM is the state machine that handles the instant out.
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type FSM struct {
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*fsm.StateMachine
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cfg *ManagerConfig
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addressParameters *AddressParameters
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staticAddress *script.StaticAddress
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deposit *Deposit
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ctx context.Context
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blockNtfnChan chan uint32
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finalizedDepositChan chan wire.OutPoint
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}
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// NewFSM creates a new state machine that can action on all static address
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// feature requests.
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func NewFSM(ctx context.Context, addressParameters *AddressParameters,
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staticAddress *script.StaticAddress, deposit *Deposit,
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cfg *ManagerConfig, finalizedDepositChan chan wire.OutPoint,
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recoverStateMachine bool) (*FSM, error) {
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depoFsm := &FSM{
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cfg: cfg,
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addressParameters: addressParameters,
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staticAddress: staticAddress,
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deposit: deposit,
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ctx: ctx,
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blockNtfnChan: make(chan uint32),
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finalizedDepositChan: finalizedDepositChan,
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}
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if recoverStateMachine {
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depoFsm.StateMachine = fsm.NewStateMachineWithState(
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depoFsm.DepositStates(), deposit.State,
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DefaultObserverSize,
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)
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} else {
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depoFsm.StateMachine = fsm.NewStateMachine(
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depoFsm.DepositStates(), DefaultObserverSize,
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)
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}
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depoFsm.ActionEntryFunc = depoFsm.updateDeposit
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go func() {
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for {
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select {
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case currentHeight := <-depoFsm.blockNtfnChan:
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depoFsm.handleBlockNotification(currentHeight)
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case <-ctx.Done():
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return
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}
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}
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}()
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return depoFsm, nil
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}
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func (f *FSM) handleBlockNotification(currentHeight uint32) {
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isExpired := func() bool {
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return currentHeight >= uint32(f.deposit.ConfirmationHeight)+
107+
f.addressParameters.Expiry
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}
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if isExpired() && f.deposit.State != WaitForExpirySweep &&
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!f.deposit.IsFinal() {
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go func() {
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err := f.SendEvent(OnExpiry, nil)
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if err != nil {
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log.Debugf("error sending OnExpiry event: %v",
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err)
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}
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}()
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}
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}
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// DepositStates returns the states a deposit can be in.
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func (f *FSM) DepositStates() fsm.States {
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return fsm.States{
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fsm.EmptyState: fsm.State{
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Transitions: fsm.Transitions{
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OnStart: Deposited,
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},
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Action: fsm.NoOpAction,
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},
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Deposited: fsm.State{
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Transitions: fsm.Transitions{
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OnExpiry: PublishExpiredDeposit,
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OnRecover: Deposited,
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},
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Action: fsm.NoOpAction,
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},
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PublishExpiredDeposit: fsm.State{
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Transitions: fsm.Transitions{
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OnRecover: PublishExpiredDeposit,
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OnExpiryPublished: WaitForExpirySweep,
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// If the timeout sweep failed we go back to
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// Deposited, hoping that another timeout sweep
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// attempt will be successful. Alternatively,
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// the client can try to coop-spend the deposit.
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fsm.OnError: Deposited,
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},
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Action: f.PublishExpiredDepositAction,
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},
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WaitForExpirySweep: fsm.State{
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Transitions: fsm.Transitions{
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OnExpirySwept: SweptExpiredDeposit,
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OnRecover: PublishExpiredDeposit,
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// If the timeout sweep failed we go back to
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// Deposited, hoping that another timeout sweep
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// attempt will be successful. Alternatively,
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// the client can try to coop-spend the deposit.
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fsm.OnError: Deposited,
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},
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Action: f.WaitForExpirySweepAction,
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},
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SweptExpiredDeposit: fsm.State{
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Transitions: fsm.Transitions{
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OnExpiry: SweptExpiredDeposit,
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},
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Action: f.SweptExpiredDepositAction,
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},
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Failed: fsm.State{
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Action: fsm.NoOpAction,
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},
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}
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}
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// DepositEntryFunction is called after every action and updates the deposit in
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// the db.
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func (f *FSM) updateDeposit(notification fsm.Notification) {
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if f.deposit == nil {
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return
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}
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f.Debugf("NextState: %v, PreviousState: %v, Event: %v",
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notification.NextState, notification.PreviousState,
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notification.Event,
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)
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f.deposit.State = notification.NextState
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// Don't update the deposit if we are in an initial state or if we
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// are transitioning from an initial state to a failed state.
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state := f.deposit.State
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if state == fsm.EmptyState || state == Deposited ||
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(notification.PreviousState == Deposited && state == Failed) {
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return
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}
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err := f.cfg.Store.UpdateDeposit(f.ctx, f.deposit)
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if err != nil {
200+
f.Errorf("unable to update deposit: %v", err)
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}
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}
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// Infof logs an info message with the deposit outpoint.
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func (f *FSM) Infof(format string, args ...interface{}) {
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log.Infof(
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"Deposit %v: "+format,
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append(
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[]interface{}{f.deposit.OutPoint},
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args...,
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)...,
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)
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}
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// Debugf logs a debug message with the deposit outpoint.
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func (f *FSM) Debugf(format string, args ...interface{}) {
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log.Debugf(
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"Deposit %v: "+format,
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append(
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[]interface{}{f.deposit.OutPoint},
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args...,
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)...,
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)
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}
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// Errorf logs an error message with the deposit outpoint.
227+
func (f *FSM) Errorf(format string, args ...interface{}) {
228+
log.Errorf(
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"Deposit %v: "+format,
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append(
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[]interface{}{f.deposit.OutPoint},
232+
args...,
233+
)...,
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)
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}
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// SignDescriptor returns the sign descriptor for the static address output.
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func (f *FSM) SignDescriptor() (lndclient.SignDescriptor, error) {
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return lndclient.SignDescriptor{
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WitnessScript: f.staticAddress.TimeoutLeaf.Script,
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KeyDesc: keychain.KeyDescriptor{
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PubKey: f.addressParameters.ClientPubkey,
243+
},
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Output: wire.NewTxOut(
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int64(f.deposit.Value), f.addressParameters.PkScript,
246+
),
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HashType: txscript.SigHashDefault,
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InputIndex: 0,
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SignMethod: input.TaprootScriptSpendSignMethod,
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}, nil
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}

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