lnd.xprv/lnwallet/btcwallet/btcwallet.go

package btcwallet

import (
	"bytes"
	"encoding/hex"
	"errors"
	"fmt"
	"math"
	"sync"
	"time"

	"github.com/btcsuite/btcd/btcec"
	"github.com/btcsuite/btcd/chaincfg"
	"github.com/btcsuite/btcd/chaincfg/chainhash"
	"github.com/btcsuite/btcd/txscript"
	"github.com/btcsuite/btcd/wire"
	"github.com/btcsuite/btcutil"
	"github.com/btcsuite/btcutil/hdkeychain"
	"github.com/btcsuite/btcutil/psbt"
	"github.com/btcsuite/btcwallet/chain"
	"github.com/btcsuite/btcwallet/waddrmgr"
	"github.com/btcsuite/btcwallet/wallet"
	base "github.com/btcsuite/btcwallet/wallet"
	"github.com/btcsuite/btcwallet/wallet/txauthor"
	"github.com/btcsuite/btcwallet/wallet/txrules"
	"github.com/btcsuite/btcwallet/walletdb"
	"github.com/btcsuite/btcwallet/wtxmgr"
	"github.com/lightningnetwork/lnd/blockcache"
	"github.com/lightningnetwork/lnd/channeldb/kvdb"
	"github.com/lightningnetwork/lnd/keychain"
	"github.com/lightningnetwork/lnd/lnwallet"
	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
)

const (
	defaultAccount  = uint32(waddrmgr.DefaultAccountNum)
	importedAccount = uint32(waddrmgr.ImportedAddrAccount)

	// UnconfirmedHeight is the special case end height that is used to
	// obtain unconfirmed transactions from ListTransactionDetails.
	UnconfirmedHeight int32 = -1

	// walletMetaBucket is used to store wallet metadata.
	walletMetaBucket = "lnwallet"

	// walletReadyKey is used to indicate that the wallet has been
	// initialized.
	walletReadyKey = "ready"
)

var (
	// waddrmgrNamespaceKey is the namespace key that the waddrmgr state is
	// stored within the top-level waleltdb buckets of btcwallet.
	waddrmgrNamespaceKey = []byte("waddrmgr")

	// lightningAddrSchema is the scope addr schema for all keys that we
	// derive. We'll treat them all as p2wkh addresses, as atm we must
	// specify a particular type.
	lightningAddrSchema = waddrmgr.ScopeAddrSchema{
		ExternalAddrType: waddrmgr.WitnessPubKey,
		InternalAddrType: waddrmgr.WitnessPubKey,
	}

	// errNoImportedAddrGen is an error returned when a new address is
	// requested for the default imported account within the wallet.
	errNoImportedAddrGen = errors.New("addresses cannot be generated for " +
		"the default imported account")
)

// BtcWallet is an implementation of the lnwallet.WalletController interface
// backed by an active instance of btcwallet. At the time of the writing of
// this documentation, this implementation requires a full btcd node to
// operate.
type BtcWallet struct {
	// wallet is an active instance of btcwallet.
	wallet *base.Wallet

	chain chain.Interface

	db walletdb.DB

	cfg *Config

	netParams *chaincfg.Params

	chainKeyScope waddrmgr.KeyScope

	blockCache *blockcache.BlockCache
}

// A compile time check to ensure that BtcWallet implements the
// WalletController and BlockChainIO interfaces.
var _ lnwallet.WalletController = (*BtcWallet)(nil)
var _ lnwallet.BlockChainIO = (*BtcWallet)(nil)

// New returns a new fully initialized instance of BtcWallet given a valid
// configuration struct.
func New(cfg Config, blockCache *blockcache.BlockCache) (*BtcWallet, error) {
	// Create the key scope for the coin type being managed by this wallet.
	chainKeyScope := waddrmgr.KeyScope{
		Purpose: keychain.BIP0043Purpose,
		Coin:    cfg.CoinType,
	}

	// Maybe the wallet has already been opened and unlocked by the
	// WalletUnlocker. So if we get a non-nil value from the config,
	// we assume everything is in order.
	var wallet = cfg.Wallet
	if wallet == nil {
		// No ready wallet was passed, so try to open an existing one.
		var pubPass []byte
		if cfg.PublicPass == nil {
			pubPass = defaultPubPassphrase
		} else {
			pubPass = cfg.PublicPass
		}

		loader, err := NewWalletLoader(
			cfg.NetParams, cfg.RecoveryWindow, cfg.LoaderOptions...,
		)
		if err != nil {
			return nil, err
		}
		walletExists, err := loader.WalletExists()
		if err != nil {
			return nil, err
		}

		if !walletExists {
			// Wallet has never been created, perform initial
			// set up.
			wallet, err = loader.CreateNewWallet(
				pubPass, cfg.PrivatePass, cfg.HdSeed,
				cfg.Birthday,
			)
			if err != nil {
				return nil, err
			}
		} else {
			// Wallet has been created and been initialized at
			// this point, open it along with all the required DB
			// namespaces, and the DB itself.
			wallet, err = loader.OpenExistingWallet(pubPass, false)
			if err != nil {
				return nil, err
			}
		}
	}

	return &BtcWallet{
		cfg:           &cfg,
		wallet:        wallet,
		db:            wallet.Database(),
		chain:         cfg.ChainSource,
		netParams:     cfg.NetParams,
		chainKeyScope: chainKeyScope,
		blockCache:    blockCache,
	}, nil
}

// loaderCfg holds optional wallet loader configuration.
type loaderCfg struct {
	dbDirPath      string
	noFreelistSync bool
	dbTimeout      time.Duration
	useLocalDB     bool
	externalDB     kvdb.Backend
}

// LoaderOption is a functional option to update the optional loader config.
type LoaderOption func(*loaderCfg)

// LoaderWithLocalWalletDB configures the wallet loader to use the local db.
func LoaderWithLocalWalletDB(dbDirPath string, noFreelistSync bool,
	dbTimeout time.Duration) LoaderOption {

	return func(cfg *loaderCfg) {
		cfg.dbDirPath = dbDirPath
		cfg.noFreelistSync = noFreelistSync
		cfg.dbTimeout = dbTimeout
		cfg.useLocalDB = true
	}
}

// LoaderWithExternalWalletDB configures the wallet loadr to use an external db.
func LoaderWithExternalWalletDB(db kvdb.Backend) LoaderOption {
	return func(cfg *loaderCfg) {
		cfg.externalDB = db
	}
}

// NewWalletLoader constructs a wallet loader.
func NewWalletLoader(chainParams *chaincfg.Params, recoveryWindow uint32,
	opts ...LoaderOption) (*wallet.Loader, error) {

	cfg := &loaderCfg{}

	// Apply all functional options.
	for _, o := range opts {
		o(cfg)
	}

	if cfg.externalDB != nil && cfg.useLocalDB {
		return nil, fmt.Errorf("wallet can either be in the local or " +
			"an external db")
	}

	if cfg.externalDB != nil {
		loader, err := base.NewLoaderWithDB(
			chainParams, recoveryWindow, cfg.externalDB,
			func() (bool, error) {
				return externalWalletExists(cfg.externalDB)
			},
		)
		if err != nil {
			return nil, err
		}

		// Decorate wallet db with out own key such that we
		// can always check whether the wallet exists or not.
		loader.OnWalletCreated(onWalletCreated)
		return loader, nil
	}

	return base.NewLoader(
		chainParams, cfg.dbDirPath, cfg.noFreelistSync,
		cfg.dbTimeout, recoveryWindow,
	), nil
}

// externalWalletExists is a helper function that we use to template btcwallet's
// Loader in order to be able check if the wallet database has been initialized
// in an external DB.
func externalWalletExists(db kvdb.Backend) (bool, error) {
	exists := false
	err := kvdb.View(db, func(tx kvdb.RTx) error {
		metaBucket := tx.ReadBucket([]byte(walletMetaBucket))
		if metaBucket != nil {
			walletReady := metaBucket.Get([]byte(walletReadyKey))
			exists = string(walletReady) == walletReadyKey
		}

		return nil
	}, func() {})

	return exists, err
}

// onWalletCreated is executed when btcwallet creates the wallet the first time.
func onWalletCreated(tx kvdb.RwTx) error {
	metaBucket, err := tx.CreateTopLevelBucket([]byte(walletMetaBucket))
	if err != nil {
		return err
	}

	return metaBucket.Put([]byte(walletReadyKey), []byte(walletReadyKey))
}

// BackEnd returns the underlying ChainService's name as a string.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) BackEnd() string {
	if b.chain != nil {
		return b.chain.BackEnd()
	}

	return ""
}

// InternalWallet returns a pointer to the internal base wallet which is the
// core of btcwallet.
func (b *BtcWallet) InternalWallet() *base.Wallet {
	return b.wallet
}

// Start initializes the underlying rpc connection, the wallet itself, and
// begins syncing to the current available blockchain state.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) Start() error {
	// We'll start by unlocking the wallet and ensuring that the KeyScope:
	// (1017, 1) exists within the internal waddrmgr. We'll need this in
	// order to properly generate the keys required for signing various
	// contracts.
	if err := b.wallet.Unlock(b.cfg.PrivatePass, nil); err != nil {
		return err
	}
	_, err := b.wallet.Manager.FetchScopedKeyManager(b.chainKeyScope)
	if err != nil {
		// If the scope hasn't yet been created (it wouldn't been
		// loaded by default if it was), then we'll manually create the
		// scope for the first time ourselves.
		err := walletdb.Update(b.db, func(tx walletdb.ReadWriteTx) error {
			addrmgrNs := tx.ReadWriteBucket(waddrmgrNamespaceKey)

			_, err := b.wallet.Manager.NewScopedKeyManager(
				addrmgrNs, b.chainKeyScope, lightningAddrSchema,
			)
			return err
		})
		if err != nil {
			return err
		}
	}

	// Establish an RPC connection in addition to starting the goroutines
	// in the underlying wallet.
	if err := b.chain.Start(); err != nil {
		return err
	}

	// Start the underlying btcwallet core.
	b.wallet.Start()

	// Pass the rpc client into the wallet so it can sync up to the
	// current main chain.
	b.wallet.SynchronizeRPC(b.chain)

	return nil
}

// Stop signals the wallet for shutdown. Shutdown may entail closing
// any active sockets, database handles, stopping goroutines, etc.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) Stop() error {
	b.wallet.Stop()

	b.wallet.WaitForShutdown()

	b.chain.Stop()

	return nil
}

// ConfirmedBalance returns the sum of all the wallet's unspent outputs that
// have at least confs confirmations. If confs is set to zero, then all unspent
// outputs, including those currently in the mempool will be included in the
// final sum. The account parameter serves as a filter to retrieve the balance
// for a specific account. When empty, the confirmed balance of all wallet
// accounts is returned.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) ConfirmedBalance(confs int32,
	accountFilter string) (btcutil.Amount, error) {

	var balance btcutil.Amount

	witnessOutputs, err := b.ListUnspentWitness(
		confs, math.MaxInt32, accountFilter,
	)
	if err != nil {
		return 0, err
	}

	for _, witnessOutput := range witnessOutputs {
		balance += witnessOutput.Value
	}

	return balance, nil
}

// NewAddress returns the next external or internal address for the wallet
// dictated by the value of the `change` parameter. If change is true, then an
// internal address will be returned, otherwise an external address should be
// returned. The account parameter must be non-empty as it determines which
// account the address should be generated from.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) NewAddress(t lnwallet.AddressType, change bool,
	accountName string) (btcutil.Address, error) {

	var (
		keyScope waddrmgr.KeyScope
		account  uint32
	)
	switch accountName {
	case waddrmgr.ImportedAddrAccountName:
		return nil, errNoImportedAddrGen

	case lnwallet.DefaultAccountName:
		switch t {
		case lnwallet.WitnessPubKey:
			keyScope = waddrmgr.KeyScopeBIP0084
		case lnwallet.NestedWitnessPubKey:
			keyScope = waddrmgr.KeyScopeBIP0049Plus
		default:
			return nil, fmt.Errorf("unknown address type")
		}
		account = defaultAccount

	default:
		var err error
		keyScope, account, err = b.wallet.LookupAccount(accountName)
		if err != nil {
			return nil, err
		}
	}

	if change {
		return b.wallet.NewChangeAddress(account, keyScope)
	}
	return b.wallet.NewAddress(account, keyScope)
}

// LastUnusedAddress returns the last *unused* address known by the wallet. An
// address is unused if it hasn't received any payments. This can be useful in
// UIs in order to continually show the "freshest" address without having to
// worry about "address inflation" caused by continual refreshing. Similar to
// NewAddress it can derive a specified address type, and also optionally a
// change address. The account parameter must be non-empty as it determines
// which account the address should be generated from.
func (b *BtcWallet) LastUnusedAddress(addrType lnwallet.AddressType,
	accountName string) (btcutil.Address, error) {

	var (
		keyScope waddrmgr.KeyScope
		account  uint32
	)
	switch accountName {
	case waddrmgr.ImportedAddrAccountName:
		return nil, errNoImportedAddrGen

	case lnwallet.DefaultAccountName:
		switch addrType {
		case lnwallet.WitnessPubKey:
			keyScope = waddrmgr.KeyScopeBIP0084
		case lnwallet.NestedWitnessPubKey:
			keyScope = waddrmgr.KeyScopeBIP0049Plus
		default:
			return nil, fmt.Errorf("unknown address type")
		}
		account = defaultAccount

	default:
		var err error
		keyScope, account, err = b.wallet.LookupAccount(accountName)
		if err != nil {
			return nil, err
		}
	}

	return b.wallet.CurrentAddress(account, keyScope)
}

// IsOurAddress checks if the passed address belongs to this wallet
//
// This is a part of the WalletController interface.
func (b *BtcWallet) IsOurAddress(a btcutil.Address) bool {
	result, err := b.wallet.HaveAddress(a)
	return result && (err == nil)
}

// ListAccounts retrieves all accounts belonging to the wallet by default. A
// name and key scope filter can be provided to filter through all of the wallet
// accounts and return only those matching.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) ListAccounts(name string,
	keyScope *waddrmgr.KeyScope) ([]*waddrmgr.AccountProperties, error) {

	var res []*waddrmgr.AccountProperties
	switch {
	// If both the name and key scope filters were provided, we'll return
	// the existing account matching those.
	case name != "" && keyScope != nil:
		account, err := b.wallet.AccountPropertiesByName(*keyScope, name)
		if err != nil {
			return nil, err
		}
		res = append(res, account)

	// Only the name filter was provided.
	case name != "" && keyScope == nil:
		// If the name corresponds to the default or imported accounts,
		// we'll return them for both of our supported key scopes.
		if name == lnwallet.DefaultAccountName ||
			name == waddrmgr.ImportedAddrAccountName {

			a1, err := b.wallet.AccountPropertiesByName(
				waddrmgr.KeyScopeBIP0049Plus, name,
			)
			if err != nil {
				return nil, err
			}
			res = append(res, a1)

			a2, err := b.wallet.AccountPropertiesByName(
				waddrmgr.KeyScopeBIP0084, name,
			)
			if err != nil {
				return nil, err
			}
			res = append(res, a2)
			break
		}

		// Otherwise, we'll retrieve the single account that's mapped by
		// the given name.
		scope, acctNum, err := b.wallet.LookupAccount(name)
		if err != nil {
			return nil, err
		}
		account, err := b.wallet.AccountProperties(scope, acctNum)
		if err != nil {
			return nil, err
		}
		res = append(res, account)

	// Only the key scope filter was provided, so we'll return all accounts
	// matching it.
	case name == "" && keyScope != nil:
		accounts, err := b.wallet.Accounts(*keyScope)
		if err != nil {
			return nil, err
		}
		for _, account := range accounts.Accounts {
			account := account
			res = append(res, &account.AccountProperties)
		}

	// Neither of the filters were provided, so return all accounts for our
	// supported key scopes.
	case name == "" && keyScope == nil:
		accounts, err := b.wallet.Accounts(waddrmgr.KeyScopeBIP0049Plus)
		if err != nil {
			return nil, err
		}
		for _, account := range accounts.Accounts {
			account := account
			res = append(res, &account.AccountProperties)
		}

		accounts, err = b.wallet.Accounts(waddrmgr.KeyScopeBIP0084)
		if err != nil {
			return nil, err
		}
		for _, account := range accounts.Accounts {
			account := account
			res = append(res, &account.AccountProperties)
		}
	}

	return res, nil
}

// ImportAccount imports an account backed by an account extended public key.
// The master key fingerprint denotes the fingerprint of the root key
// corresponding to the account public key (also known as the key with
// derivation path m/). This may be required by some hardware wallets for proper
// identification and signing.
//
// The address type can usually be inferred from the key's version, but may be
// required for certain keys to map them into the proper scope.
//
// For BIP-0044 keys, an address type must be specified as we intend to not
// support importing BIP-0044 keys into the wallet using the legacy
// pay-to-pubkey-hash (P2PKH) scheme. A nested witness address type will force
// the standard BIP-0049 derivation scheme, while a witness address type will
// force the standard BIP-0084 derivation scheme.
//
// For BIP-0049 keys, an address type must also be specified to make a
// distinction between the standard BIP-0049 address schema (nested witness
// pubkeys everywhere) and our own BIP-0049Plus address schema (nested pubkeys
// externally, witness pubkeys internally).
//
// This is a part of the WalletController interface.
func (b *BtcWallet) ImportAccount(name string, accountPubKey *hdkeychain.ExtendedKey,
	masterKeyFingerprint uint32, addrType *waddrmgr.AddressType) error {

	_, err := b.wallet.ImportAccount(
		name, accountPubKey, masterKeyFingerprint, addrType,
	)
	return err
}

// ImportPublicKey imports a single derived public key into the wallet. The
// address type can usually be inferred from the key's version, but in the case
// of legacy versions (xpub, tpub), an address type must be specified as we
// intend to not support importing BIP-44 keys into the wallet using the legacy
// pay-to-pubkey-hash (P2PKH) scheme.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) ImportPublicKey(pubKey *btcec.PublicKey,
	addrType waddrmgr.AddressType) error {

	return b.wallet.ImportPublicKey(pubKey, addrType)
}

// SendOutputs funds, signs, and broadcasts a Bitcoin transaction paying out to
// the specified outputs. In the case the wallet has insufficient funds, or the
// outputs are non-standard, a non-nil error will be returned.
//
// NOTE: This method requires the global coin selection lock to be held.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) SendOutputs(outputs []*wire.TxOut,
	feeRate chainfee.SatPerKWeight, minConfs int32, label string) (*wire.MsgTx, error) {

	// Convert our fee rate from sat/kw to sat/kb since it's required by
	// SendOutputs.
	feeSatPerKB := btcutil.Amount(feeRate.FeePerKVByte())

	// Sanity check outputs.
	if len(outputs) < 1 {
		return nil, lnwallet.ErrNoOutputs
	}

	// Sanity check minConfs.
	if minConfs < 0 {
		return nil, lnwallet.ErrInvalidMinconf
	}

	return b.wallet.SendOutputs(
		outputs, nil, defaultAccount, minConfs, feeSatPerKB, label,
	)
}

// CreateSimpleTx creates a Bitcoin transaction paying to the specified
// outputs. The transaction is not broadcasted to the network, but a new change
// address might be created in the wallet database. In the case the wallet has
// insufficient funds, or the outputs are non-standard, an error should be
// returned. This method also takes the target fee expressed in sat/kw that
// should be used when crafting the transaction.
//
// NOTE: The dryRun argument can be set true to create a tx that doesn't alter
// the database. A tx created with this set to true SHOULD NOT be broadcasted.
//
// NOTE: This method requires the global coin selection lock to be held.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) CreateSimpleTx(outputs []*wire.TxOut,
	feeRate chainfee.SatPerKWeight, minConfs int32,
	dryRun bool) (*txauthor.AuthoredTx, error) {

	// The fee rate is passed in using units of sat/kw, so we'll convert
	// this to sat/KB as the CreateSimpleTx method requires this unit.
	feeSatPerKB := btcutil.Amount(feeRate.FeePerKVByte())

	// Sanity check outputs.
	if len(outputs) < 1 {
		return nil, lnwallet.ErrNoOutputs
	}

	// Sanity check minConfs.
	if minConfs < 0 {
		return nil, lnwallet.ErrInvalidMinconf
	}

	for _, output := range outputs {
		// When checking an output for things like dusty-ness, we'll
		// use the default mempool relay fee rather than the target
		// effective fee rate to ensure accuracy. Otherwise, we may
		// mistakenly mark small-ish, but not quite dust output as
		// dust.
		err := txrules.CheckOutput(
			output, txrules.DefaultRelayFeePerKb,
		)
		if err != nil {
			return nil, err
		}
	}

	return b.wallet.CreateSimpleTx(
		nil, defaultAccount, outputs, minConfs, feeSatPerKB, dryRun,
	)
}

// LockOutpoint marks an outpoint as locked meaning it will no longer be deemed
// as eligible for coin selection. Locking outputs are utilized in order to
// avoid race conditions when selecting inputs for usage when funding a
// channel.
//
// NOTE: This method requires the global coin selection lock to be held.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) LockOutpoint(o wire.OutPoint) {
	b.wallet.LockOutpoint(o)
}

// UnlockOutpoint unlocks a previously locked output, marking it eligible for
// coin selection.
//
// NOTE: This method requires the global coin selection lock to be held.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) UnlockOutpoint(o wire.OutPoint) {
	b.wallet.UnlockOutpoint(o)
}

// LeaseOutput locks an output to the given ID, preventing it from being
// available for any future coin selection attempts. The absolute time of the
// lock's expiration is returned. The expiration of the lock can be extended by
// successive invocations of this call. Outputs can be unlocked before their
// expiration through `ReleaseOutput`.
//
// If the output is not known, wtxmgr.ErrUnknownOutput is returned. If the
// output has already been locked to a different ID, then
// wtxmgr.ErrOutputAlreadyLocked is returned.
//
// NOTE: This method requires the global coin selection lock to be held.
func (b *BtcWallet) LeaseOutput(id wtxmgr.LockID, op wire.OutPoint,
	duration time.Duration) (time.Time, error) {

	// Make sure we don't attempt to double lock an output that's been
	// locked by the in-memory implementation.
	if b.wallet.LockedOutpoint(op) {
		return time.Time{}, wtxmgr.ErrOutputAlreadyLocked
	}

	return b.wallet.LeaseOutput(id, op, duration)
}

// ListLeasedOutputs returns a list of all currently locked outputs.
func (b *BtcWallet) ListLeasedOutputs() ([]*wtxmgr.LockedOutput, error) {
	return b.wallet.ListLeasedOutputs()
}

// ReleaseOutput unlocks an output, allowing it to be available for coin
// selection if it remains unspent. The ID should match the one used to
// originally lock the output.
//
// NOTE: This method requires the global coin selection lock to be held.
func (b *BtcWallet) ReleaseOutput(id wtxmgr.LockID, op wire.OutPoint) error {
	return b.wallet.ReleaseOutput(id, op)
}

// ListUnspentWitness returns all unspent outputs which are version 0 witness
// programs. The 'minConfs' and 'maxConfs' parameters indicate the minimum
// and maximum number of confirmations an output needs in order to be returned
// by this method. Passing -1 as 'minConfs' indicates that even unconfirmed
// outputs should be returned. Using MaxInt32 as 'maxConfs' implies returning
// all outputs with at least 'minConfs'. The account parameter serves as a
// filter to retrieve the unspent outputs for a specific account.  When empty,
// the unspent outputs of all wallet accounts are returned.
//
// NOTE: This method requires the global coin selection lock to be held.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) ListUnspentWitness(minConfs, maxConfs int32,
	accountFilter string) ([]*lnwallet.Utxo, error) {

	// First, grab all the unfiltered currently unspent outputs.
	unspentOutputs, err := b.wallet.ListUnspent(
		minConfs, maxConfs, accountFilter,
	)
	if err != nil {
		return nil, err
	}

	// Next, we'll run through all the regular outputs, only saving those
	// which are p2wkh outputs or a p2wsh output nested within a p2sh output.
	witnessOutputs := make([]*lnwallet.Utxo, 0, len(unspentOutputs))
	for _, output := range unspentOutputs {
		pkScript, err := hex.DecodeString(output.ScriptPubKey)
		if err != nil {
			return nil, err
		}

		addressType := lnwallet.UnknownAddressType
		if txscript.IsPayToWitnessPubKeyHash(pkScript) {
			addressType = lnwallet.WitnessPubKey
		} else if txscript.IsPayToScriptHash(pkScript) {
			// TODO(roasbeef): This assumes all p2sh outputs returned by the
			// wallet are nested p2pkh. We can't check the redeem script because
			// the btcwallet service does not include it.
			addressType = lnwallet.NestedWitnessPubKey
		}

		if addressType == lnwallet.WitnessPubKey ||
			addressType == lnwallet.NestedWitnessPubKey {

			txid, err := chainhash.NewHashFromStr(output.TxID)
			if err != nil {
				return nil, err
			}

			// We'll ensure we properly convert the amount given in
			// BTC to satoshis.
			amt, err := btcutil.NewAmount(output.Amount)
			if err != nil {
				return nil, err
			}

			utxo := &lnwallet.Utxo{
				AddressType: addressType,
				Value:       amt,
				PkScript:    pkScript,
				OutPoint: wire.OutPoint{
					Hash:  *txid,
					Index: output.Vout,
				},
				Confirmations: output.Confirmations,
			}
			witnessOutputs = append(witnessOutputs, utxo)
		}

	}

	return witnessOutputs, nil
}

// PublishTransaction performs cursory validation (dust checks, etc), then
// finally broadcasts the passed transaction to the Bitcoin network. If
// publishing the transaction fails, an error describing the reason is returned
// (currently ErrDoubleSpend). If the transaction is already published to the
// network (either in the mempool or chain) no error will be returned.
func (b *BtcWallet) PublishTransaction(tx *wire.MsgTx, label string) error {
	if err := b.wallet.PublishTransaction(tx, label); err != nil {

		// If we failed to publish the transaction, check whether we
		// got an error of known type.
		switch err.(type) {

		// If the wallet reports a double spend, convert it to our
		// internal ErrDoubleSpend and return.
		case *base.ErrDoubleSpend:
			return lnwallet.ErrDoubleSpend

		// If the wallet reports a replacement error, return
		// ErrDoubleSpend, as we currently are never attempting to
		// replace transactions.
		case *base.ErrReplacement:
			return lnwallet.ErrDoubleSpend

		default:
			return err
		}
	}
	return nil
}

// LabelTransaction adds a label to a transaction. If the tx already
// has a label, this call will fail unless the overwrite parameter
// is set. Labels must not be empty, and they are limited to 500 chars.
//
// Note: it is part of the WalletController interface.
func (b *BtcWallet) LabelTransaction(hash chainhash.Hash, label string,
	overwrite bool) error {

	return b.wallet.LabelTransaction(hash, label, overwrite)
}

// extractBalanceDelta extracts the net balance delta from the PoV of the
// wallet given a TransactionSummary.
func extractBalanceDelta(
	txSummary base.TransactionSummary,
	tx *wire.MsgTx,
) (btcutil.Amount, error) {
	// For each input we debit the wallet's outflow for this transaction,
	// and for each output we credit the wallet's inflow for this
	// transaction.
	var balanceDelta btcutil.Amount
	for _, input := range txSummary.MyInputs {
		balanceDelta -= input.PreviousAmount
	}
	for _, output := range txSummary.MyOutputs {
		balanceDelta += btcutil.Amount(tx.TxOut[output.Index].Value)
	}

	return balanceDelta, nil
}

// minedTransactionsToDetails is a helper function which converts a summary
// information about mined transactions to a TransactionDetail.
func minedTransactionsToDetails(
	currentHeight int32,
	block base.Block,
	chainParams *chaincfg.Params,
) ([]*lnwallet.TransactionDetail, error) {

	details := make([]*lnwallet.TransactionDetail, 0, len(block.Transactions))
	for _, tx := range block.Transactions {
		wireTx := &wire.MsgTx{}
		txReader := bytes.NewReader(tx.Transaction)

		if err := wireTx.Deserialize(txReader); err != nil {
			return nil, err
		}

		var destAddresses []btcutil.Address
		for _, txOut := range wireTx.TxOut {
			_, outAddresses, _, err := txscript.ExtractPkScriptAddrs(
				txOut.PkScript, chainParams,
			)
			if err != nil {
				// Skip any unsupported addresses to prevent
				// other transactions from not being returned.
				continue
			}

			destAddresses = append(destAddresses, outAddresses...)
		}

		txDetail := &lnwallet.TransactionDetail{
			Hash:             *tx.Hash,
			NumConfirmations: currentHeight - block.Height + 1,
			BlockHash:        block.Hash,
			BlockHeight:      block.Height,
			Timestamp:        block.Timestamp,
			TotalFees:        int64(tx.Fee),
			DestAddresses:    destAddresses,
			RawTx:            tx.Transaction,
			Label:            tx.Label,
		}

		balanceDelta, err := extractBalanceDelta(tx, wireTx)
		if err != nil {
			return nil, err
		}
		txDetail.Value = balanceDelta

		details = append(details, txDetail)
	}

	return details, nil
}

// unminedTransactionsToDetail is a helper function which converts a summary
// for an unconfirmed transaction to a transaction detail.
func unminedTransactionsToDetail(
	summary base.TransactionSummary,
	chainParams *chaincfg.Params,
) (*lnwallet.TransactionDetail, error) {

	wireTx := &wire.MsgTx{}
	txReader := bytes.NewReader(summary.Transaction)

	if err := wireTx.Deserialize(txReader); err != nil {
		return nil, err
	}

	var destAddresses []btcutil.Address
	for _, txOut := range wireTx.TxOut {
		_, outAddresses, _, err :=
			txscript.ExtractPkScriptAddrs(txOut.PkScript, chainParams)
		if err != nil {
			// Skip any unsupported addresses to prevent other
			// transactions from not being returned.
			continue
		}

		destAddresses = append(destAddresses, outAddresses...)
	}

	txDetail := &lnwallet.TransactionDetail{
		Hash:          *summary.Hash,
		TotalFees:     int64(summary.Fee),
		Timestamp:     summary.Timestamp,
		DestAddresses: destAddresses,
		RawTx:         summary.Transaction,
		Label:         summary.Label,
	}

	balanceDelta, err := extractBalanceDelta(summary, wireTx)
	if err != nil {
		return nil, err
	}
	txDetail.Value = balanceDelta

	return txDetail, nil
}

// ListTransactionDetails returns a list of all transactions which are relevant
// to the wallet over [startHeight;endHeight]. If start height is greater than
// end height, the transactions will be retrieved in reverse order. To include
// unconfirmed transactions, endHeight should be set to the special value -1.
// This will return transactions from the tip of the chain until the start
// height (inclusive) and unconfirmed transactions. The account parameter serves
// as a filter to retrieve the transactions relevant to a specific account. When
// empty, transactions of all wallet accounts are returned.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) ListTransactionDetails(startHeight, endHeight int32,
	accountFilter string) ([]*lnwallet.TransactionDetail, error) {

	// Grab the best block the wallet knows of, we'll use this to calculate
	// # of confirmations shortly below.
	bestBlock := b.wallet.Manager.SyncedTo()
	currentHeight := bestBlock.Height

	// We'll attempt to find all transactions from start to end height.
	start := base.NewBlockIdentifierFromHeight(startHeight)
	stop := base.NewBlockIdentifierFromHeight(endHeight)
	txns, err := b.wallet.GetTransactions(start, stop, accountFilter, nil)
	if err != nil {
		return nil, err
	}

	txDetails := make([]*lnwallet.TransactionDetail, 0,
		len(txns.MinedTransactions)+len(txns.UnminedTransactions))

	// For both confirmed and unconfirmed transactions, create a
	// TransactionDetail which re-packages the data returned by the base
	// wallet.
	for _, blockPackage := range txns.MinedTransactions {
		details, err := minedTransactionsToDetails(
			currentHeight, blockPackage, b.netParams,
		)
		if err != nil {
			return nil, err
		}

		txDetails = append(txDetails, details...)
	}
	for _, tx := range txns.UnminedTransactions {
		detail, err := unminedTransactionsToDetail(tx, b.netParams)
		if err != nil {
			return nil, err
		}

		txDetails = append(txDetails, detail)
	}

	return txDetails, nil
}

// FundPsbt creates a fully populated PSBT packet that contains enough inputs to
// fund the outputs specified in the passed in packet with the specified fee
// rate. If there is change left, a change output from the internal wallet is
// added and the index of the change output is returned. Otherwise no additional
// output is created and the index -1 is returned.
//
// NOTE: If the packet doesn't contain any inputs, coin selection is performed
// automatically. The account parameter must be non-empty as it determines which
// set of coins are eligible for coin selection. If the packet does contain any
// inputs, it is assumed that full coin selection happened externally and no
// additional inputs are added. If the specified inputs aren't enough to fund
// the outputs with the given fee rate, an error is returned. No lock lease is
// acquired for any of the selected/validated inputs. It is in the caller's
// responsibility to lock the inputs before handing them out.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) FundPsbt(packet *psbt.Packet,
	feeRate chainfee.SatPerKWeight, accountName string) (int32, error) {

	// The fee rate is passed in using units of sat/kw, so we'll convert
	// this to sat/KB as the CreateSimpleTx method requires this unit.
	feeSatPerKB := btcutil.Amount(feeRate.FeePerKVByte())

	var (
		keyScope   *waddrmgr.KeyScope
		accountNum uint32
	)
	switch accountName {
	// If the default/imported account name was specified, we'll provide a
	// nil key scope to FundPsbt, allowing it to select inputs from both key
	// scopes (NP2WKH, P2WKH).
	case lnwallet.DefaultAccountName:
		accountNum = defaultAccount

	case waddrmgr.ImportedAddrAccountName:
		accountNum = importedAccount

	// Otherwise, map the account name to its key scope and internal account
	// number to only select inputs from said account.
	default:
		scope, account, err := b.wallet.LookupAccount(accountName)
		if err != nil {
			return 0, err
		}
		keyScope = &scope
		accountNum = account
	}

	// Let the wallet handle coin selection and/or fee estimation based on
	// the partial TX information in the packet.
	return b.wallet.FundPsbt(packet, keyScope, accountNum, feeSatPerKB)
}

// FinalizePsbt expects a partial transaction with all inputs and outputs fully
// declared and tries to sign all inputs that belong to the specified account.
// Lnd must be the last signer of the transaction. That means, if there are any
// unsigned non-witness inputs or inputs without UTXO information attached or
// inputs without witness data that do not belong to lnd's wallet, this method
// will fail. If no error is returned, the PSBT is ready to be extracted and the
// final TX within to be broadcast.
//
// NOTE: This method does NOT publish the transaction after it's been
// finalized successfully.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) FinalizePsbt(packet *psbt.Packet, accountName string) error {
	var (
		keyScope   *waddrmgr.KeyScope
		accountNum uint32
	)
	switch accountName {
	// If the default/imported account name was specified, we'll provide a
	// nil key scope to FundPsbt, allowing it to sign inputs from both key
	// scopes (NP2WKH, P2WKH).
	case lnwallet.DefaultAccountName:
		accountNum = defaultAccount

	case waddrmgr.ImportedAddrAccountName:
		accountNum = importedAccount

	// Otherwise, map the account name to its key scope and internal account
	// number to determine if the inputs belonging to this account should be
	// signed.
	default:
		scope, account, err := b.wallet.LookupAccount(accountName)
		if err != nil {
			return err
		}
		keyScope = &scope
		accountNum = account
	}

	return b.wallet.FinalizePsbt(keyScope, accountNum, packet)
}

// txSubscriptionClient encapsulates the transaction notification client from
// the base wallet. Notifications received from the client will be proxied over
// two distinct channels.
type txSubscriptionClient struct {
	txClient base.TransactionNotificationsClient

	confirmed   chan *lnwallet.TransactionDetail
	unconfirmed chan *lnwallet.TransactionDetail

	w *base.Wallet

	wg   sync.WaitGroup
	quit chan struct{}
}

// ConfirmedTransactions returns a channel which will be sent on as new
// relevant transactions are confirmed.
//
// This is part of the TransactionSubscription interface.
func (t *txSubscriptionClient) ConfirmedTransactions() chan *lnwallet.TransactionDetail {
	return t.confirmed
}

// UnconfirmedTransactions returns a channel which will be sent on as
// new relevant transactions are seen within the network.
//
// This is part of the TransactionSubscription interface.
func (t *txSubscriptionClient) UnconfirmedTransactions() chan *lnwallet.TransactionDetail {
	return t.unconfirmed
}

// Cancel finalizes the subscription, cleaning up any resources allocated.
//
// This is part of the TransactionSubscription interface.
func (t *txSubscriptionClient) Cancel() {
	close(t.quit)
	t.wg.Wait()

	t.txClient.Done()
}

// notificationProxier proxies the notifications received by the underlying
// wallet's notification client to a higher-level TransactionSubscription
// client.
func (t *txSubscriptionClient) notificationProxier() {
	defer t.wg.Done()

out:
	for {
		select {
		case txNtfn := <-t.txClient.C:
			// TODO(roasbeef): handle detached blocks
			currentHeight := t.w.Manager.SyncedTo().Height

			// Launch a goroutine to re-package and send
			// notifications for any newly confirmed transactions.
			go func() {
				for _, block := range txNtfn.AttachedBlocks {
					details, err := minedTransactionsToDetails(currentHeight, block, t.w.ChainParams())
					if err != nil {
						continue
					}

					for _, d := range details {
						select {
						case t.confirmed <- d:
						case <-t.quit:
							return
						}
					}
				}

			}()

			// Launch a goroutine to re-package and send
			// notifications for any newly unconfirmed transactions.
			go func() {
				for _, tx := range txNtfn.UnminedTransactions {
					detail, err := unminedTransactionsToDetail(
						tx, t.w.ChainParams(),
					)
					if err != nil {
						continue
					}

					select {
					case t.unconfirmed <- detail:
					case <-t.quit:
						return
					}
				}
			}()
		case <-t.quit:
			break out
		}
	}
}

// SubscribeTransactions returns a TransactionSubscription client which
// is capable of receiving async notifications as new transactions
// related to the wallet are seen within the network, or found in
// blocks.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) SubscribeTransactions() (lnwallet.TransactionSubscription, error) {
	walletClient := b.wallet.NtfnServer.TransactionNotifications()

	txClient := &txSubscriptionClient{
		txClient:    walletClient,
		confirmed:   make(chan *lnwallet.TransactionDetail),
		unconfirmed: make(chan *lnwallet.TransactionDetail),
		w:           b.wallet,
		quit:        make(chan struct{}),
	}
	txClient.wg.Add(1)
	go txClient.notificationProxier()

	return txClient, nil
}

// IsSynced returns a boolean indicating if from the PoV of the wallet, it has
// fully synced to the current best block in the main chain.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) IsSynced() (bool, int64, error) {
	// Grab the best chain state the wallet is currently aware of.
	syncState := b.wallet.Manager.SyncedTo()

	// We'll also extract the current best wallet timestamp so the caller
	// can get an idea of where we are in the sync timeline.
	bestTimestamp := syncState.Timestamp.Unix()

	// Next, query the chain backend to grab the info about the tip of the
	// main chain.
	bestHash, bestHeight, err := b.cfg.ChainSource.GetBestBlock()
	if err != nil {
		return false, 0, err
	}

	// Make sure the backing chain has been considered synced first.
	if !b.wallet.ChainSynced() {
		bestHeader, err := b.cfg.ChainSource.GetBlockHeader(bestHash)
		if err != nil {
			return false, 0, err
		}
		bestTimestamp = bestHeader.Timestamp.Unix()
		return false, bestTimestamp, nil
	}

	// If the wallet hasn't yet fully synced to the node's best chain tip,
	// then we're not yet fully synced.
	if syncState.Height < bestHeight {
		return false, bestTimestamp, nil
	}

	// If the wallet is on par with the current best chain tip, then we
	// still may not yet be synced as the chain backend may still be
	// catching up to the main chain. So we'll grab the block header in
	// order to make a guess based on the current time stamp.
	blockHeader, err := b.cfg.ChainSource.GetBlockHeader(bestHash)
	if err != nil {
		return false, 0, err
	}

	// If the timestamp on the best header is more than 2 hours in the
	// past, then we're not yet synced.
	minus24Hours := time.Now().Add(-2 * time.Hour)
	if blockHeader.Timestamp.Before(minus24Hours) {
		return false, bestTimestamp, nil
	}

	return true, bestTimestamp, nil
}

// GetRecoveryInfo returns a boolean indicating whether the wallet is started
// in recovery mode. It also returns a float64, ranging from 0 to 1,
// representing the recovery progress made so far.
//
// This is a part of the WalletController interface.
func (b *BtcWallet) GetRecoveryInfo() (bool, float64, error) {
	isRecoveryMode := true
	progress := float64(0)

	// A zero value in RecoveryWindow indicates there is no trigger of
	// recovery mode.
	if b.cfg.RecoveryWindow == 0 {
		isRecoveryMode = false
		return isRecoveryMode, progress, nil
	}

	// Query the wallet's birthday block height from db.
	var birthdayBlock waddrmgr.BlockStamp
	err := walletdb.View(b.db, func(tx walletdb.ReadTx) error {
		var err error
		addrmgrNs := tx.ReadBucket(waddrmgrNamespaceKey)
		birthdayBlock, _, err = b.wallet.Manager.BirthdayBlock(addrmgrNs)
		if err != nil {
			return err
		}
		return nil
	})

	if err != nil {
		// The wallet won't start until the backend is synced, thus the birthday
		// block won't be set and this particular error will be returned. We'll
		// catch this error and return a progress of 0 instead.
		if waddrmgr.IsError(err, waddrmgr.ErrBirthdayBlockNotSet) {
			return isRecoveryMode, progress, nil
		}

		return isRecoveryMode, progress, err
	}

	// Grab the best chain state the wallet is currently aware of.
	syncState := b.wallet.Manager.SyncedTo()

	// Next, query the chain backend to grab the info about the tip of the
	// main chain.
	//
	// NOTE: The actual recovery process is handled by the btcsuite/btcwallet.
	// The process purposefully doesn't update the best height. It might create
	// a small difference between the height queried here and the height used
	// in the recovery process, ie, the bestHeight used here might be greater,
	// showing the recovery being unfinished while it's actually done. However,
	// during a wallet rescan after the recovery, the wallet's synced height
	// will catch up and this won't be an issue.
	_, bestHeight, err := b.cfg.ChainSource.GetBestBlock()
	if err != nil {
		return isRecoveryMode, progress, err
	}

	// The birthday block height might be greater than the current synced height
	// in a newly restored wallet, and might be greater than the chain tip if a
	// rollback happens. In that case, we will return zero progress here.
	if syncState.Height < birthdayBlock.Height ||
		bestHeight < birthdayBlock.Height {
		return isRecoveryMode, progress, nil
	}

	// progress is the ratio of the [number of blocks processed] over the [total
	// number of blocks] needed in a recovery mode, ranging from 0 to 1, in
	// which,
	// - total number of blocks is the current chain's best height minus the
	//   wallet's birthday height plus 1.
	// - number of blocks processed is the wallet's synced height minus its
	//   birthday height plus 1.
	// - If the wallet is born very recently, the bestHeight can be equal to
	//   the birthdayBlock.Height, and it will recovery instantly.
	progress = float64(syncState.Height-birthdayBlock.Height+1) /
		float64(bestHeight-birthdayBlock.Height+1)

	return isRecoveryMode, progress, nil
}