package lnwallet

import (
	"bytes"
	"crypto/sha256"
	"io/ioutil"
	"math/big"
	"math/rand"
	"os"
	"reflect"
	"runtime"
	"testing"

	"github.com/davecgh/go-spew/spew"
	"github.com/lightningnetwork/lnd/chainntnfs"
	"github.com/lightningnetwork/lnd/channeldb"
	"github.com/lightningnetwork/lnd/lnwire"
	"github.com/lightningnetwork/lnd/shachain"
	"github.com/roasbeef/btcd/blockchain"
	"github.com/roasbeef/btcd/btcec"
	"github.com/roasbeef/btcd/chaincfg/chainhash"
	"github.com/roasbeef/btcd/txscript"
	"github.com/roasbeef/btcd/wire"
	"github.com/roasbeef/btcutil"
)

var (
	privPass = []byte("private-test")

	// For simplicity a single priv key controls all of our test outputs.
	testWalletPrivKey = []byte{
		0x2b, 0xd8, 0x06, 0xc9, 0x7f, 0x0e, 0x00, 0xaf,
		0x1a, 0x1f, 0xc3, 0x32, 0x8f, 0xa7, 0x63, 0xa9,
		0x26, 0x97, 0x23, 0xc8, 0xdb, 0x8f, 0xac, 0x4f,
		0x93, 0xaf, 0x71, 0xdb, 0x18, 0x6d, 0x6e, 0x90,
	}

	// We're alice :)
	bobsPrivKey = []byte{
		0x81, 0xb6, 0x37, 0xd8, 0xfc, 0xd2, 0xc6, 0xda,
		0x63, 0x59, 0xe6, 0x96, 0x31, 0x13, 0xa1, 0x17,
		0xd, 0xe7, 0x95, 0xe4, 0xb7, 0x25, 0xb8, 0x4d,
		0x1e, 0xb, 0x4c, 0xfd, 0x9e, 0xc5, 0x8c, 0xe9,
	}

	// Use a hard-coded HD seed.
	testHdSeed = chainhash.Hash{
		0xb7, 0x94, 0x38, 0x5f, 0x2d, 0x1e, 0xf7, 0xab,
		0x4d, 0x92, 0x73, 0xd1, 0x90, 0x63, 0x81, 0xb4,
		0x4f, 0x2f, 0x6f, 0x25, 0x88, 0xa3, 0xef, 0xb9,
		0x6a, 0x49, 0x18, 0x83, 0x31, 0x98, 0x47, 0x53,
	}

	// The number of confirmations required to consider any created channel
	// open.
	numReqConfs = uint16(1)
)

// initRevocationWindows simulates a new channel being opened within the p2p
// network by populating the initial revocation windows of the passed
// commitment state machines.
//
// TODO(roasbeef): rename!
func initRevocationWindows(chanA, chanB *LightningChannel, windowSize int) error {
	aliceNextRevoke, err := chanA.NextRevocationKey()
	if err != nil {
		return err
	}
	if err := chanB.InitNextRevocation(aliceNextRevoke); err != nil {
		return err
	}

	bobNextRevoke, err := chanB.NextRevocationKey()
	if err != nil {
		return err
	}
	if err := chanA.InitNextRevocation(bobNextRevoke); err != nil {
		return err
	}

	return nil
}

// forceStateTransition executes the necessary interaction between the two
// commitment state machines to transition to a new state locking in any
// pending updates.
func forceStateTransition(chanA, chanB *LightningChannel) error {
	aliceSig, aliceHtlcSigs, err := chanA.SignNextCommitment()
	if err != nil {
		return err
	}
	if err = chanB.ReceiveNewCommitment(aliceSig, aliceHtlcSigs); err != nil {
		return err
	}

	bobRevocation, _, err := chanB.RevokeCurrentCommitment()
	if err != nil {
		return err
	}
	bobSig, bobHtlcSigs, err := chanB.SignNextCommitment()
	if err != nil {
		return err
	}

	if _, err := chanA.ReceiveRevocation(bobRevocation); err != nil {
		return err
	}
	if err := chanA.ReceiveNewCommitment(bobSig, bobHtlcSigs); err != nil {
		return err
	}

	aliceRevocation, _, err := chanA.RevokeCurrentCommitment()
	if err != nil {
		return err
	}
	if _, err := chanB.ReceiveRevocation(aliceRevocation); err != nil {
		return err
	}

	return nil
}

// createTestChannels creates two test lightning channels using the provided
// notifier. The channel itself is funded with 10 BTC, with 5 BTC allocated to
// each side. Within the channel, Alice is the initiator.
func createTestChannels(revocationWindow int) (*LightningChannel,
	*LightningChannel, func(), error) {

	channelCapacity := btcutil.Amount(10 * 1e8)
	channelBal := channelCapacity / 2
	aliceDustLimit := btcutil.Amount(200)
	bobDustLimit := btcutil.Amount(1300)
	csvTimeoutAlice := uint32(5)
	csvTimeoutBob := uint32(4)

	prevOut := &wire.OutPoint{
		Hash:  chainhash.Hash(testHdSeed),
		Index: 0,
	}
	fundingTxIn := wire.NewTxIn(prevOut, nil, nil)

	// For each party, we'll create a distinct set of keys in order to
	// emulate the typical set up with live channels.
	var (
		aliceKeys []*btcec.PrivateKey
		bobKeys   []*btcec.PrivateKey
	)
	for i := 0; i < 5; i++ {
		key := make([]byte, len(testWalletPrivKey))
		copy(key[:], testWalletPrivKey[:])
		key[0] ^= byte(i + 1)

		aliceKey, _ := btcec.PrivKeyFromBytes(btcec.S256(), key)
		aliceKeys = append(aliceKeys, aliceKey)

		key = make([]byte, len(bobsPrivKey))
		copy(key[:], bobsPrivKey)
		key[0] ^= byte(i + 1)

		bobKey, _ := btcec.PrivKeyFromBytes(btcec.S256(), key)
		bobKeys = append(bobKeys, bobKey)
	}

	aliceCfg := channeldb.ChannelConfig{
		ChannelConstraints: channeldb.ChannelConstraints{
			DustLimit:        aliceDustLimit,
			MaxPendingAmount: lnwire.MilliSatoshi(rand.Int63()),
			ChanReserve:      channelCapacity / 100,
			MinHTLC:          lnwire.MilliSatoshi(rand.Int63()),
			MaxAcceptedHtlcs: uint16(rand.Int31()),
		},
		CsvDelay:            uint16(csvTimeoutAlice),
		MultiSigKey:         aliceKeys[0].PubKey(),
		RevocationBasePoint: aliceKeys[1].PubKey(),
		PaymentBasePoint:    aliceKeys[2].PubKey(),
		DelayBasePoint:      aliceKeys[3].PubKey(),
		HtlcBasePoint:       aliceKeys[4].PubKey(),
	}
	bobCfg := channeldb.ChannelConfig{
		ChannelConstraints: channeldb.ChannelConstraints{
			DustLimit:        bobDustLimit,
			MaxPendingAmount: lnwire.MilliSatoshi(rand.Int63()),
			ChanReserve:      channelCapacity / 100,
			MinHTLC:          lnwire.MilliSatoshi(rand.Int63()),
			MaxAcceptedHtlcs: uint16(rand.Int31()),
		},
		CsvDelay:            uint16(csvTimeoutBob),
		MultiSigKey:         bobKeys[0].PubKey(),
		RevocationBasePoint: bobKeys[1].PubKey(),
		PaymentBasePoint:    bobKeys[2].PubKey(),
		DelayBasePoint:      bobKeys[3].PubKey(),
		HtlcBasePoint:       bobKeys[4].PubKey(),
	}

	bobRoot := DeriveRevocationRoot(
		bobKeys[0], testHdSeed, aliceKeys[0].PubKey(),
	)
	bobPreimageProducer := shachain.NewRevocationProducer(bobRoot)
	bobFirstRevoke, err := bobPreimageProducer.AtIndex(0)
	if err != nil {
		return nil, nil, nil, err
	}
	bobCommitPoint := ComputeCommitmentPoint(bobFirstRevoke[:])

	aliceRoot := DeriveRevocationRoot(
		aliceKeys[0], testHdSeed, bobKeys[0].PubKey(),
	)
	alicePreimageProducer := shachain.NewRevocationProducer(aliceRoot)
	aliceFirstRevoke, err := alicePreimageProducer.AtIndex(0)
	if err != nil {
		return nil, nil, nil, err
	}
	aliceCommitPoint := ComputeCommitmentPoint(aliceFirstRevoke[:])

	aliceCommitTx, bobCommitTx, err := CreateCommitmentTxns(channelBal,
		channelBal, &aliceCfg, &bobCfg, aliceCommitPoint, bobCommitPoint,
		*fundingTxIn)
	if err != nil {
		return nil, nil, nil, err
	}

	alicePath, err := ioutil.TempDir("", "alicedb")
	dbAlice, err := channeldb.Open(alicePath)
	if err != nil {
		return nil, nil, nil, err
	}

	bobPath, err := ioutil.TempDir("", "bobdb")
	dbBob, err := channeldb.Open(bobPath)
	if err != nil {
		return nil, nil, nil, err
	}

	estimator := &StaticFeeEstimator{24}
	feePerWeight, err := estimator.EstimateFeePerWeight(1)
	if err != nil {
		return nil, nil, nil, err
	}
	feePerKw := feePerWeight * 1000
	commitFee := calcStaticFee(0)

	aliceCommit := channeldb.ChannelCommitment{
		CommitHeight:  0,
		LocalBalance:  lnwire.NewMSatFromSatoshis(channelBal - commitFee),
		RemoteBalance: lnwire.NewMSatFromSatoshis(channelBal),
		CommitFee:     commitFee,
		FeePerKw:      feePerKw,
		CommitTx:      aliceCommitTx,
		CommitSig:     bytes.Repeat([]byte{1}, 71),
	}
	bobCommit := channeldb.ChannelCommitment{
		CommitHeight:  0,
		LocalBalance:  lnwire.NewMSatFromSatoshis(channelBal),
		RemoteBalance: lnwire.NewMSatFromSatoshis(channelBal - commitFee),
		CommitFee:     commitFee,
		FeePerKw:      feePerKw,
		CommitTx:      bobCommitTx,
		CommitSig:     bytes.Repeat([]byte{1}, 71),
	}

	aliceChannelState := &channeldb.OpenChannel{
		LocalChanCfg:            aliceCfg,
		RemoteChanCfg:           bobCfg,
		IdentityPub:             aliceKeys[0].PubKey(),
		FundingOutpoint:         *prevOut,
		ChanType:                channeldb.SingleFunder,
		IsInitiator:             true,
		Capacity:                channelCapacity,
		RemoteCurrentRevocation: bobCommitPoint,
		RevocationProducer:      alicePreimageProducer,
		RevocationStore:         shachain.NewRevocationStore(),
		LocalCommitment:         aliceCommit,
		RemoteCommitment:        aliceCommit,
		Db:                      dbAlice,
	}
	bobChannelState := &channeldb.OpenChannel{
		LocalChanCfg:            bobCfg,
		RemoteChanCfg:           aliceCfg,
		IdentityPub:             bobKeys[0].PubKey(),
		FundingOutpoint:         *prevOut,
		ChanType:                channeldb.SingleFunder,
		IsInitiator:             false,
		Capacity:                channelCapacity,
		RemoteCurrentRevocation: aliceCommitPoint,
		RevocationProducer:      bobPreimageProducer,
		RevocationStore:         shachain.NewRevocationStore(),
		LocalCommitment:         bobCommit,
		RemoteCommitment:        bobCommit,
		Db:                      dbBob,
	}

	aliceSigner := &mockSigner{privkeys: aliceKeys}
	bobSigner := &mockSigner{privkeys: bobKeys}

	pCache := &mockPreimageCache{
		// hash -> preimage
		preimageMap: make(map[[32]byte][]byte),
	}

	// TODO(roasbeef): make mock version of pre-image store
	channelAlice, err := NewLightningChannel(
		aliceSigner, pCache, aliceChannelState,
	)
	if err != nil {
		return nil, nil, nil, err
	}
	channelBob, err := NewLightningChannel(
		bobSigner, pCache, bobChannelState,
	)
	if err != nil {
		return nil, nil, nil, err
	}

	if err := channelAlice.channelState.FullSync(); err != nil {
		return nil, nil, nil, err
	}
	if err := channelBob.channelState.FullSync(); err != nil {
		return nil, nil, nil, err
	}

	cleanUpFunc := func() {
		os.RemoveAll(bobPath)
		os.RemoveAll(alicePath)

		channelAlice.Stop()
		channelBob.Stop()
	}

	// Now that the channel are open, simulate the start of a session by
	// having Alice and Bob extend their revocation windows to each other.
	err = initRevocationWindows(channelAlice, channelBob, revocationWindow)
	if err != nil {
		return nil, nil, nil, err
	}

	return channelAlice, channelBob, cleanUpFunc, nil
}

// calcStaticFee calculates appropriate fees for commitment transactions.  This
// function provides a simple way to allow test balance assertions to take fee
// calculations into account.
//
// TODO(bvu): Refactor when dynamic fee estimation is added.
func calcStaticFee(numHTLCs int) btcutil.Amount {
	const (
		commitWeight = btcutil.Amount(724)
		htlcWeight   = 172
		feePerKw     = btcutil.Amount(24/4) * 1000
	)
	return feePerKw * (commitWeight +
		btcutil.Amount(htlcWeight*numHTLCs)) / 1000
}

// createHTLC is a utility function for generating an HTLC with a given
// preimage and a given amount.
func createHTLC(id int, amount lnwire.MilliSatoshi) (*lnwire.UpdateAddHTLC, [32]byte) {
	preimage := bytes.Repeat([]byte{byte(id)}, 32)
	paymentHash := sha256.Sum256(preimage)

	var returnPreimage [32]byte
	copy(returnPreimage[:], preimage)

	return &lnwire.UpdateAddHTLC{
		ID:          uint64(id),
		PaymentHash: paymentHash,
		Amount:      amount,
		Expiry:      uint32(5),
	}, returnPreimage
}

func assertOutputExistsByValue(t *testing.T, commitTx *wire.MsgTx,
	value btcutil.Amount) {

	for _, txOut := range commitTx.TxOut {
		if txOut.Value == int64(value) {
			return
		}
	}

	t.Fatalf("unable to find output of value %v within tx %v", value,
		spew.Sdump(commitTx))
}

// TestSimpleAddSettleWorkflow tests a simple channel scenario wherein the
// local node (Alice in this case) creates a new outgoing HTLC to bob, commits
// this change, then bob immediately commits a settlement of the HTLC after the
// initial add is fully committed in both commit chains.
//
// TODO(roasbeef): write higher level framework to exercise various states of
// the state machine
//  * DSL language perhaps?
//  * constructed via input/output files
func TestSimpleAddSettleWorkflow(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	paymentPreimage := bytes.Repeat([]byte{1}, 32)
	paymentHash := sha256.Sum256(paymentPreimage)
	htlcAmt := lnwire.NewMSatFromSatoshis(btcutil.SatoshiPerBitcoin)
	htlc := &lnwire.UpdateAddHTLC{
		PaymentHash: paymentHash,
		Amount:      htlcAmt,
		Expiry:      uint32(5),
	}

	// First Alice adds the outgoing HTLC to her local channel's state
	// update log. Then Alice sends this wire message over to Bob who adds
	// this htlc to his remote state update log.
	aliceHtlcIndex, err := aliceChannel.AddHTLC(htlc)
	if err != nil {
		t.Fatalf("unable to add htlc: %v", err)
	}

	bobHtlcIndex, err := bobChannel.ReceiveHTLC(htlc)
	if err != nil {
		t.Fatalf("unable to recv htlc: %v", err)
	}

	// Next alice commits this change by sending a signature message. Since
	// we expect the messages to be ordered, Bob will receive the HTLC we
	// just sent before he receives this signature, so the signature will
	// cover the HTLC.
	aliceSig, aliceHtlcSigs, err := aliceChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("alice unable to sign commitment: %v", err)
	}

	// Bob receives this signature message, and checks that this covers the
	// state he has in his remote log. This includes the HTLC just sent
	// from Alice.
	err = bobChannel.ReceiveNewCommitment(aliceSig, aliceHtlcSigs)
	if err != nil {
		t.Fatalf("bob unable to process alice's new commitment: %v", err)
	}

	// Bob revokes his prior commitment given to him by Alice, since he now
	// has a valid signature for a newer commitment.
	bobRevocation, _, err := bobChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("unable to generate bob revocation: %v", err)
	}

	// Bob finally send a signature for Alice's commitment transaction.
	// This signature will cover the HTLC, since Bob will first send the
	// revocation just created. The revocation also acks every received
	// HTLC up to the point where Alice sent here signature.
	bobSig, bobHtlcSigs, err := bobChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("bob unable to sign alice's commitment: %v", err)
	}

	// Alice then processes this revocation, sending her own revocation for
	// her prior commitment transaction. Alice shouldn't have any HTLCs to
	// forward since she's sending an outgoing HTLC.
	if htlcs, err := aliceChannel.ReceiveRevocation(bobRevocation); err != nil {
		t.Fatalf("alice unable to process bob's revocation: %v", err)
	} else if len(htlcs) != 0 {
		t.Fatalf("alice forwards %v htlcs, should forward none: ", len(htlcs))
	}

	// Alice then processes bob's signature, and since she just received
	// the revocation, she expect this signature to cover everything up to
	// the point where she sent her signature, including the HTLC.
	err = aliceChannel.ReceiveNewCommitment(bobSig, bobHtlcSigs)
	if err != nil {
		t.Fatalf("alice unable to process bob's new commitment: %v", err)
	}

	// Alice then generates a revocation for bob.
	aliceRevocation, _, err := aliceChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("unable to revoke alice channel: %v", err)
	}

	// Finally Bob processes Alice's revocation, at this point the new HTLC
	// is fully locked in within both commitment transactions. Bob should
	// also be able to forward an HTLC now that the HTLC has been locked
	// into both commitment transactions.
	if htlcs, err := bobChannel.ReceiveRevocation(aliceRevocation); err != nil {
		t.Fatalf("bob unable to process alice's revocation: %v", err)
	} else if len(htlcs) != 1 {
		t.Fatalf("bob should be able to forward an HTLC, instead can "+
			"forward %v", len(htlcs))
	}

	// At this point, both sides should have the proper number of satoshis
	// sent, and commitment height updated within their local channel
	// state.
	aliceSent := lnwire.MilliSatoshi(0)
	bobSent := lnwire.MilliSatoshi(0)

	if aliceChannel.channelState.TotalMSatSent != aliceSent {
		t.Fatalf("alice has incorrect milli-satoshis sent: %v vs %v",
			aliceChannel.channelState.TotalMSatSent, aliceSent)
	}
	if aliceChannel.channelState.TotalMSatReceived != bobSent {
		t.Fatalf("alice has incorrect milli-satoshis received %v vs %v",
			aliceChannel.channelState.TotalMSatReceived, bobSent)
	}
	if bobChannel.channelState.TotalMSatSent != bobSent {
		t.Fatalf("bob has incorrect milli-satoshis sent %v vs %v",
			bobChannel.channelState.TotalMSatSent, bobSent)
	}
	if bobChannel.channelState.TotalMSatReceived != aliceSent {
		t.Fatalf("bob has incorrect milli-satoshis received %v vs %v",
			bobChannel.channelState.TotalMSatReceived, aliceSent)
	}
	if bobChannel.currentHeight != 1 {
		t.Fatalf("bob has incorrect commitment height, %v vs %v",
			bobChannel.currentHeight, 1)
	}
	if aliceChannel.currentHeight != 1 {
		t.Fatalf("alice has incorrect commitment height, %v vs %v",
			aliceChannel.currentHeight, 1)
	}

	// Both commitment transactions should have three outputs, and one of
	// them should be exactly the amount of the HTLC.
	if len(aliceChannel.channelState.LocalCommitment.CommitTx.TxOut) != 3 {
		t.Fatalf("alice should have three commitment outputs, instead "+
			"have %v",
			len(aliceChannel.channelState.LocalCommitment.CommitTx.TxOut))
	}
	if len(bobChannel.channelState.LocalCommitment.CommitTx.TxOut) != 3 {
		t.Fatalf("bob should have three commitment outputs, instead "+
			"have %v",
			len(bobChannel.channelState.LocalCommitment.CommitTx.TxOut))
	}
	assertOutputExistsByValue(t,
		aliceChannel.channelState.LocalCommitment.CommitTx,
		htlcAmt.ToSatoshis())
	assertOutputExistsByValue(t,
		bobChannel.channelState.LocalCommitment.CommitTx,
		htlcAmt.ToSatoshis())

	// Now we'll repeat a similar exchange, this time with Bob settling the
	// HTLC once he learns of the preimage.
	var preimage [32]byte
	copy(preimage[:], paymentPreimage)
	err = bobChannel.SettleHTLC(preimage, bobHtlcIndex)
	if err != nil {
		t.Fatalf("bob unable to settle inbound htlc: %v", err)
	}

	err = aliceChannel.ReceiveHTLCSettle(preimage, aliceHtlcIndex)
	if err != nil {
		t.Fatalf("alice unable to accept settle of outbound htlc: %v", err)
	}

	bobSig2, bobHtlcSigs2, err := bobChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("bob unable to sign settle commitment: %v", err)
	}
	err = aliceChannel.ReceiveNewCommitment(bobSig2, bobHtlcSigs2)
	if err != nil {
		t.Fatalf("alice unable to process bob's new commitment: %v", err)
	}

	aliceRevocation2, _, err := aliceChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("alice unable to generate revocation: %v", err)
	}
	aliceSig2, aliceHtlcSigs2, err := aliceChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("alice unable to sign new commitment: %v", err)
	}

	if htlcs, err := bobChannel.ReceiveRevocation(aliceRevocation2); err != nil {
		t.Fatalf("bob unable to process alice's revocation: %v", err)
	} else if len(htlcs) != 0 {
		t.Fatalf("bob shouldn't forward any HTLCs after outgoing settle, "+
			"instead can forward: %v", spew.Sdump(htlcs))
	}
	err = bobChannel.ReceiveNewCommitment(aliceSig2, aliceHtlcSigs2)
	if err != nil {
		t.Fatalf("bob unable to process alice's new commitment: %v", err)
	}

	bobRevocation2, _, err := bobChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("bob unable to revoke commitment: %v", err)
	}

	if htlcs, err := aliceChannel.ReceiveRevocation(bobRevocation2); err != nil {
		t.Fatalf("alice unable to process bob's revocation: %v", err)
	} else if len(htlcs) != 1 {
		// Alice should now be able to forward the settlement HTLC to
		// any down stream peers.
		t.Fatalf("alice should be able to forward a single HTLC, "+
			"instead can forward %v: %v", len(htlcs), spew.Sdump(htlcs))
	}

	// At this point, Bob should have 6 BTC settled, with Alice still having
	// 4 BTC. Alice's channel should show 1 BTC sent and Bob's channel
	// should show 1 BTC received. They should also be at commitment height
	// two, with the revocation window extended by by 1 (5).
	mSatTransferred := lnwire.NewMSatFromSatoshis(btcutil.SatoshiPerBitcoin)
	if aliceChannel.channelState.TotalMSatSent != mSatTransferred {
		t.Fatalf("alice satoshis sent incorrect %v vs %v expected",
			aliceChannel.channelState.TotalMSatSent,
			mSatTransferred)
	}
	if aliceChannel.channelState.TotalMSatReceived != 0 {
		t.Fatalf("alice satoshis received incorrect %v vs %v expected",
			aliceChannel.channelState.TotalMSatReceived, 0)
	}
	if bobChannel.channelState.TotalMSatReceived != mSatTransferred {
		t.Fatalf("bob satoshis received incorrect %v vs %v expected",
			bobChannel.channelState.TotalMSatReceived,
			mSatTransferred)
	}
	if bobChannel.channelState.TotalMSatSent != 0 {
		t.Fatalf("bob satoshis sent incorrect %v vs %v expected",
			bobChannel.channelState.TotalMSatSent, 0)
	}
	if bobChannel.currentHeight != 2 {
		t.Fatalf("bob has incorrect commitment height, %v vs %v",
			bobChannel.currentHeight, 2)
	}
	if aliceChannel.currentHeight != 2 {
		t.Fatalf("alice has incorrect commitment height, %v vs %v",
			aliceChannel.currentHeight, 2)
	}

	// The logs of both sides should now be cleared since the entry adding
	// the HTLC should have been removed once both sides receive the
	// revocation.
	if aliceChannel.localUpdateLog.Len() != 0 {
		t.Fatalf("alice's local not updated, should be empty, has %v "+
			"entries instead", aliceChannel.localUpdateLog.Len())
	}
	if aliceChannel.remoteUpdateLog.Len() != 0 {
		t.Fatalf("alice's remote not updated, should be empty, has %v "+
			"entries instead", aliceChannel.remoteUpdateLog.Len())
	}
	if len(aliceChannel.localUpdateLog.updateIndex) != 0 {
		t.Fatalf("alice's local log index not cleared, should be empty but "+
			"has %v entries", len(aliceChannel.localUpdateLog.updateIndex))
	}
	if len(aliceChannel.remoteUpdateLog.updateIndex) != 0 {
		t.Fatalf("alice's remote log index not cleared, should be empty but "+
			"has %v entries", len(aliceChannel.remoteUpdateLog.updateIndex))
	}
}

// TestCheckCommitTxSize checks that estimation size of commitment
// transaction with some degree of error corresponds to the actual size.
func TestCheckCommitTxSize(t *testing.T) {
	t.Parallel()

	checkSize := func(channel *LightningChannel, count int) {
		// Due to variable size of the signatures (70-73) in
		// witness script actual size of commitment transaction might
		// be lower on 6 weight.
		BaseCommitmentTxSizeEstimationError := 6

		commitTx, err := channel.getSignedCommitTx()
		if err != nil {
			t.Fatalf("unable to initiate alice force close: %v", err)
		}

		actualCost := blockchain.GetTransactionWeight(btcutil.NewTx(commitTx))
		estimatedCost := estimateCommitTxWeight(count, false)

		diff := int(estimatedCost - actualCost)
		if 0 > diff || BaseCommitmentTxSizeEstimationError < diff {
			t.Fatalf("estimation is wrong, diff: %v", diff)
		}

	}

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	// Check that weight estimation of the commitment transaction without
	// HTLCs is right.
	checkSize(aliceChannel, 0)
	checkSize(bobChannel, 0)

	// Adding HTLCs and check that size stays in allowable estimation
	// error window.
	for i := 0; i <= 10; i++ {
		htlc, _ := createHTLC(i, lnwire.MilliSatoshi(1e7))

		if _, err := aliceChannel.AddHTLC(htlc); err != nil {
			t.Fatalf("alice unable to add htlc: %v", err)
		}
		if _, err := bobChannel.ReceiveHTLC(htlc); err != nil {
			t.Fatalf("bob unable to receive htlc: %v", err)
		}

		if err := forceStateTransition(aliceChannel, bobChannel); err != nil {
			t.Fatalf("unable to complete state update: %v", err)
		}
		checkSize(aliceChannel, i+1)
		checkSize(bobChannel, i+1)
	}

	// Settle HTLCs and check that estimation is counting cost of settle
	// HTLCs properly.
	for i := 10; i >= 0; i-- {
		_, preimage := createHTLC(i, lnwire.MilliSatoshi(1e7))

		err := bobChannel.SettleHTLC(preimage, uint64(i))
		if err != nil {
			t.Fatalf("bob unable to settle inbound htlc: %v", err)
		}

		err = aliceChannel.ReceiveHTLCSettle(preimage, uint64(i))
		if err != nil {
			t.Fatalf("alice unable to accept settle of outbound htlc: %v", err)
		}

		if err := forceStateTransition(bobChannel, aliceChannel); err != nil {
			t.Fatalf("unable to complete state update: %v", err)
		}
		checkSize(aliceChannel, i)
		checkSize(bobChannel, i)
	}
}

func TestCooperativeChannelClosure(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	aliceDeliveryScript := bobsPrivKey[:]
	bobDeliveryScript := testHdSeed[:]

	aliceFeeRate := uint64(aliceChannel.channelState.LocalCommitment.FeePerKw)
	bobFeeRate := uint64(bobChannel.channelState.LocalCommitment.FeePerKw)

	// We'll store with both Alice and Bob creating a new close proposal
	// with the same fee.
	aliceFee := btcutil.Amount(aliceChannel.CalcFee(aliceFeeRate))
	aliceSig, _, _, err := aliceChannel.CreateCloseProposal(
		aliceFee, aliceDeliveryScript, bobDeliveryScript,
	)
	if err != nil {
		t.Fatalf("unable to create alice coop close proposal: %v", err)
	}
	aliceCloseSig := append(aliceSig, byte(txscript.SigHashAll))

	bobFee := btcutil.Amount(bobChannel.CalcFee(bobFeeRate))
	bobSig, _, _, err := bobChannel.CreateCloseProposal(
		bobFee, bobDeliveryScript, aliceDeliveryScript,
	)
	if err != nil {
		t.Fatalf("unable to create bob coop close proposal: %v", err)
	}
	bobCloseSig := append(bobSig, byte(txscript.SigHashAll))

	// With the proposals created, both sides should be able to properly
	// process the other party's signature. This indicates that the
	// transaction is well formed, and the signatures verify.
	aliceCloseTx, _, err := bobChannel.CompleteCooperativeClose(
		bobCloseSig, aliceCloseSig, bobDeliveryScript,
		aliceDeliveryScript, bobFee)
	if err != nil {
		t.Fatalf("unable to complete alice cooperative close: %v", err)
	}
	bobCloseSha := aliceCloseTx.TxHash()

	bobCloseTx, _, err := aliceChannel.CompleteCooperativeClose(
		aliceCloseSig, bobCloseSig, aliceDeliveryScript,
		bobDeliveryScript, aliceFee)
	if err != nil {
		t.Fatalf("unable to complete bob cooperative close: %v", err)
	}
	aliceCloseSha := bobCloseTx.TxHash()

	if bobCloseSha != aliceCloseSha {
		t.Fatalf("alice and bob close transactions don't match: %v", err)
	}
}

// TestForceClose checks that the resulting ForceCloseSummary is correct when a
// peer is ForceClosing the channel. Will check outputs both above and below
// the dust limit. Additionally, we'll ensure that the node which executed the
// force close generates HTLC resolutions that are capable of sweeping both
// incoming and outgoing HTLC's.
func TestForceClose(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(3)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	bobAmount := bobChannel.channelState.LocalCommitment.LocalBalance

	// First, we'll add an outgoing HTLC from Alice to Bob, such that it
	// will still be present within the broadcast commitment transaction.
	// We'll ensure that the HTLC amount is above Alice's dust limit.
	htlcAmount := lnwire.NewMSatFromSatoshis(20000)
	htlcAlice, _ := createHTLC(0, htlcAmount)
	if _, err := aliceChannel.AddHTLC(htlcAlice); err != nil {
		t.Fatalf("alice unable to add htlc: %v", err)
	}
	if _, err := bobChannel.ReceiveHTLC(htlcAlice); err != nil {
		t.Fatalf("bob unable to recv add htlc: %v", err)
	}

	// We'll also a distinct HTLC from Bob -> Alice. This way, Alice will
	// have both an incoming and outgoing HTLC on her commitment
	// transaction.
	htlcBob, preimageBob := createHTLC(0, htlcAmount)
	if _, err := bobChannel.AddHTLC(htlcBob); err != nil {
		t.Fatalf("alice unable to add htlc: %v", err)
	}
	if _, err := aliceChannel.ReceiveHTLC(htlcBob); err != nil {
		t.Fatalf("bob unable to recv add htlc: %v", err)
	}

	// Next, we'll perform two state transitions to ensure that both HTLC's
	// get fully locked-in.
	if err := forceStateTransition(aliceChannel, bobChannel); err != nil {
		t.Fatalf("Can't update the channel state: %v", err)
	}
	if err := forceStateTransition(bobChannel, aliceChannel); err != nil {
		t.Fatalf("Can't update the channel state: %v", err)
	}

	// Before we force close Alice's channel, we'll add the pre-image of
	// Bob's HTLC to her preimage cache.
	aliceChannel.pCache.AddPreimage(preimageBob[:])

	// With the cache populated, we'll now attempt the force close
	// initiated by Alice.
	closeSummary, err := aliceChannel.ForceClose()
	if err != nil {
		t.Fatalf("unable to force close channel: %v", err)
	}

	// Alice should detect that she can sweep the outgoing HTLC after a
	// timeout, but also that she's able to sweep in incoming HTLC Bob sent
	// her.
	if len(closeSummary.HtlcResolutions.OutgoingHTLCs) != 1 {
		t.Fatalf("alice out htlc resolutions not populated: expected %v "+
			"htlcs, got %v htlcs",
			1, len(closeSummary.HtlcResolutions.OutgoingHTLCs))
	}
	if len(closeSummary.HtlcResolutions.IncomingHTLCs) != 1 {
		t.Fatalf("alice in htlc resolutions not populated: expected %v "+
			"htlcs, got %v htlcs",
			1, len(closeSummary.HtlcResolutions.IncomingHTLCs))
	}

	// The SelfOutputSignDesc should be non-nil since the output to-self is
	// non-dust.
	aliceCommitResolution := closeSummary.CommitResolution
	if aliceCommitResolution == nil {
		t.Fatalf("alice fails to include to-self output in " +
			"ForceCloseSummary")
	}

	// The rest of the close summary should have been populated properly.
	aliceDelayPoint := aliceChannel.channelState.LocalChanCfg.DelayBasePoint
	if !aliceCommitResolution.SelfOutputSignDesc.PubKey.IsEqual(
		aliceDelayPoint,
	) {
		t.Fatalf("alice incorrect pubkey in SelfOutputSignDesc")
	}

	// Factoring in the fee rate, Alice's amount should properly reflect
	// that we've added two additional HTLC to the commitment transaction.
	totalCommitWeight := CommitWeight + (HtlcWeight * 2)
	feePerKw := aliceChannel.channelState.LocalCommitment.FeePerKw
	commitFee := btcutil.Amount((int64(feePerKw) * totalCommitWeight) / 1000)
	expectedAmount := (aliceChannel.Capacity / 2) - htlcAmount.ToSatoshis() - commitFee
	if aliceCommitResolution.SelfOutputSignDesc.Output.Value != int64(expectedAmount) {
		t.Fatalf("alice incorrect output value in SelfOutputSignDesc, "+
			"expected %v, got %v", int64(expectedAmount),
			aliceCommitResolution.SelfOutputSignDesc.Output.Value)
	}

	// Alice's listed CSV delay should also match the delay that was
	// pre-committed to at channel opening.
	if aliceCommitResolution.MaturityDelay !=
		uint32(aliceChannel.localChanCfg.CsvDelay) {

		t.Fatalf("alice: incorrect local CSV delay in ForceCloseSummary, "+
			"expected %v, got %v",
			aliceChannel.channelState.LocalChanCfg.CsvDelay,
			aliceCommitResolution.MaturityDelay)
	}

	// Next, we'll ensure that the second level HTLC transaction it itself
	// spendable, and also that the delivery output (with delay) itself has
	// a valid sign descriptor.
	htlcResolution := closeSummary.HtlcResolutions.OutgoingHTLCs[0]
	outHtlcIndex := htlcResolution.SignedTimeoutTx.TxIn[0].PreviousOutPoint.Index
	senderHtlcPkScript := closeSummary.CloseTx.TxOut[outHtlcIndex].PkScript

	// First, verify that the second level transaction can properly spend
	// the multi-sig clause within the output on the commitment transaction
	// that produces this HTLC.
	timeoutTx := htlcResolution.SignedTimeoutTx
	vm, err := txscript.NewEngine(senderHtlcPkScript,
		timeoutTx, 0, txscript.StandardVerifyFlags, nil,
		nil, int64(htlcAmount.ToSatoshis()))
	if err != nil {
		t.Fatalf("unable to create engine: %v", err)
	}
	if err := vm.Execute(); err != nil {
		t.Fatalf("htlc timeout spend is invalid: %v", err)
	}

	// Next, we'll ensure that we can spend the output of the second level
	// transaction given a properly crafted sweep transaction.
	sweepTx := wire.NewMsgTx(2)
	sweepTx.AddTxIn(&wire.TxIn{
		PreviousOutPoint: wire.OutPoint{
			Hash:  htlcResolution.SignedTimeoutTx.TxHash(),
			Index: 0,
		},
	})
	sweepTx.AddTxOut(&wire.TxOut{
		PkScript: senderHtlcPkScript,
		Value:    htlcResolution.SweepSignDesc.Output.Value,
	})
	htlcResolution.SweepSignDesc.InputIndex = 0
	sweepTx.TxIn[0].Witness, err = htlcSpendSuccess(aliceChannel.signer,
		&htlcResolution.SweepSignDesc, sweepTx,
		uint32(aliceChannel.channelState.LocalChanCfg.CsvDelay))
	if err != nil {
		t.Fatalf("unable to gen witness for timeout output: %v", err)
	}

	// With the witness fully populated for the success spend from the
	// second-level transaction, we ensure that the scripts properly
	// validate given the information within the htlc resolution struct.
	vm, err = txscript.NewEngine(
		htlcResolution.SweepSignDesc.Output.PkScript,
		sweepTx, 0, txscript.StandardVerifyFlags, nil,
		nil, htlcResolution.SweepSignDesc.Output.Value,
	)
	if err != nil {
		t.Fatalf("unable to create engine: %v", err)
	}
	if err := vm.Execute(); err != nil {
		t.Fatalf("htlc timeout spend is invalid: %v", err)
	}

	// Finally, the txid of the commitment transaction and the one returned
	// as the closing transaction should also match.
	closeTxHash := closeSummary.CloseTx.TxHash()
	commitTxHash := aliceChannel.channelState.LocalCommitment.CommitTx.TxHash()
	if !bytes.Equal(closeTxHash[:], commitTxHash[:]) {
		t.Fatalf("alice: incorrect close transaction txid")
	}

	// We'll now perform similar set of checks to ensure that Alice is able
	// to sweep the output that Bob sent to her on-chain with knowledge of
	// the preimage.
	inHtlcResolution := closeSummary.HtlcResolutions.IncomingHTLCs[0]
	inHtlcIndex := inHtlcResolution.SignedSuccessTx.TxIn[0].PreviousOutPoint.Index
	receiverHtlcScript := closeSummary.CloseTx.TxOut[inHtlcIndex].PkScript

	// With the original pkscript located, we'll now verify that the second
	// level transaction can spend from the multi-sig out.
	successTx := inHtlcResolution.SignedSuccessTx
	vm, err = txscript.NewEngine(receiverHtlcScript,
		successTx, 0, txscript.StandardVerifyFlags, nil,
		nil, int64(htlcAmount.ToSatoshis()))
	if err != nil {
		t.Fatalf("unable to create engine: %v", err)
	}
	if err := vm.Execute(); err != nil {
		t.Fatalf("htlc success spend is invalid: %v", err)
	}

	// Finally, we'll construct a transaction to spend the produced
	// second-level output with the attached SignDescriptor.
	sweepTx = wire.NewMsgTx(2)
	sweepTx.AddTxIn(&wire.TxIn{
		PreviousOutPoint: inHtlcResolution.ClaimOutpoint,
	})
	sweepTx.AddTxOut(&wire.TxOut{
		PkScript: receiverHtlcScript,
		Value:    inHtlcResolution.SweepSignDesc.Output.Value,
	})
	inHtlcResolution.SweepSignDesc.InputIndex = 0
	sweepTx.TxIn[0].Witness, err = htlcSpendSuccess(aliceChannel.signer,
		&inHtlcResolution.SweepSignDesc, sweepTx,
		uint32(aliceChannel.channelState.LocalChanCfg.CsvDelay))
	if err != nil {
		t.Fatalf("unable to gen witness for timeout output: %v", err)
	}

	// The spend we create above spending the second level HTLC output
	// should validate without any issues.
	vm, err = txscript.NewEngine(
		inHtlcResolution.SweepSignDesc.Output.PkScript,
		sweepTx, 0, txscript.StandardVerifyFlags, nil,
		nil, inHtlcResolution.SweepSignDesc.Output.Value,
	)
	if err != nil {
		t.Fatalf("unable to create engine: %v", err)
	}
	if err := vm.Execute(); err != nil {
		t.Fatalf("htlc timeout spend is invalid: %v", err)
	}

	// Check the same for Bob's ForceCloseSummary.
	closeSummary, err = bobChannel.ForceClose()
	if err != nil {
		t.Fatalf("unable to force close channel: %v", err)
	}
	bobCommitResolution := closeSummary.CommitResolution
	if bobCommitResolution == nil {
		t.Fatalf("bob fails to include to-self output in ForceCloseSummary")
	}
	bobDelayPoint := bobChannel.channelState.LocalChanCfg.DelayBasePoint
	if !bobCommitResolution.SelfOutputSignDesc.PubKey.IsEqual(bobDelayPoint) {
		t.Fatalf("bob incorrect pubkey in SelfOutputSignDesc")
	}
	if bobCommitResolution.SelfOutputSignDesc.Output.Value !=
		int64(bobAmount.ToSatoshis()-htlcAmount.ToSatoshis()) {

		t.Fatalf("bob incorrect output value in SelfOutputSignDesc, "+
			"expected %v, got %v",
			bobAmount.ToSatoshis(),
			int64(bobCommitResolution.SelfOutputSignDesc.Output.Value))
	}
	if bobCommitResolution.MaturityDelay !=
		uint32(bobChannel.channelState.LocalChanCfg.CsvDelay) {

		t.Fatalf("bob: incorrect local CSV delay in ForceCloseSummary, "+
			"expected %v, got %v",
			bobChannel.channelState.LocalChanCfg.CsvDelay,
			bobCommitResolution.MaturityDelay)
	}

	closeTxHash = closeSummary.CloseTx.TxHash()
	commitTxHash = bobChannel.channelState.LocalCommitment.CommitTx.TxHash()
	if !bytes.Equal(closeTxHash[:], commitTxHash[:]) {
		t.Fatalf("bob: incorrect close transaction txid")
	}

	// As we didn't add the preimage of Alice's HTLC to bob's preimage
	// cache, he should only detect that he can sweep only his outgoing
	// HTLC upon force close.
	if len(closeSummary.HtlcResolutions.OutgoingHTLCs) != 1 {
		t.Fatalf("alice out htlc resolutions not populated: expected %v "+
			"htlcs, got %v htlcs",
			1, len(closeSummary.HtlcResolutions.OutgoingHTLCs))
	}

	// Bob should recognize that the incoming HTLC is there, but the
	// preimage should be empty as he doesn't have the knowledge required
	// to sweep it.
	if len(closeSummary.HtlcResolutions.IncomingHTLCs) != 1 {
		t.Fatalf("bob in htlc resolutions not populated: expected %v "+
			"htlcs, got %v htlcs",
			1, len(closeSummary.HtlcResolutions.IncomingHTLCs))
	}
	var zeroHash [32]byte
	if closeSummary.HtlcResolutions.IncomingHTLCs[0].Preimage != zeroHash {
		t.Fatalf("bob shouldn't know preimage but does")
	}
}

// TestForceCloseDustOutput tests that if either side force closes with an
// active dust output (for only a single party due to asymmetric dust values),
// then the force close summary is well crafted.
func TestForceCloseDustOutput(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(3)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	htlcAmount := lnwire.NewMSatFromSatoshis(500)

	aliceAmount := aliceChannel.channelState.LocalCommitment.LocalBalance
	bobAmount := bobChannel.channelState.LocalCommitment.LocalBalance

	// Have Bobs' to-self output be below her dust limit and check
	// ForceCloseSummary again on both peers.
	htlc, preimage := createHTLC(0, bobAmount-htlcAmount)
	bobHtlcIndex, err := bobChannel.AddHTLC(htlc)
	if err != nil {
		t.Fatalf("alice unable to add htlc: %v", err)
	}
	aliceHtlcIndex, err := aliceChannel.ReceiveHTLC(htlc)
	if err != nil {
		t.Fatalf("bob unable to receive htlc: %v", err)
	}
	if err := forceStateTransition(bobChannel, aliceChannel); err != nil {
		t.Fatalf("Can't update the channel state: %v", err)
	}

	// Settle HTLC and sign new commitment.
	err = aliceChannel.SettleHTLC(preimage, aliceHtlcIndex)
	if err != nil {
		t.Fatalf("bob unable to settle inbound htlc: %v", err)
	}
	err = bobChannel.ReceiveHTLCSettle(preimage, bobHtlcIndex)
	if err != nil {
		t.Fatalf("alice unable to accept settle of outbound htlc: %v", err)
	}
	if err := forceStateTransition(aliceChannel, bobChannel); err != nil {
		t.Fatalf("Can't update the channel state: %v", err)
	}

	aliceAmount = aliceChannel.channelState.LocalCommitment.LocalBalance
	bobAmount = bobChannel.channelState.LocalCommitment.RemoteBalance

	closeSummary, err := aliceChannel.ForceClose()
	if err != nil {
		t.Fatalf("unable to force close channel: %v", err)
	}

	// Alice's to-self output should still be in the commitment
	// transaction.
	commitResolution := closeSummary.CommitResolution
	if commitResolution == nil {
		t.Fatalf("alice fails to include to-self output in " +
			"ForceCloseSummary")
	}
	if !commitResolution.SelfOutputSignDesc.PubKey.IsEqual(
		aliceChannel.channelState.LocalChanCfg.DelayBasePoint,
	) {
		t.Fatalf("alice incorrect pubkey in SelfOutputSignDesc")
	}
	if commitResolution.SelfOutputSignDesc.Output.Value !=
		int64(aliceAmount.ToSatoshis()) {
		t.Fatalf("alice incorrect output value in SelfOutputSignDesc, "+
			"expected %v, got %v",
			aliceChannel.channelState.LocalCommitment.LocalBalance.ToSatoshis(),
			commitResolution.SelfOutputSignDesc.Output.Value)
	}

	if commitResolution.MaturityDelay !=
		uint32(aliceChannel.channelState.LocalChanCfg.CsvDelay) {
		t.Fatalf("alice: incorrect local CSV delay in ForceCloseSummary, "+
			"expected %v, got %v",
			aliceChannel.channelState.LocalChanCfg.CsvDelay,
			commitResolution.MaturityDelay)
	}

	closeTxHash := closeSummary.CloseTx.TxHash()
	commitTxHash := aliceChannel.channelState.LocalCommitment.CommitTx.TxHash()
	if !bytes.Equal(closeTxHash[:], commitTxHash[:]) {
		t.Fatalf("alice: incorrect close transaction txid")
	}

	closeSummary, err = bobChannel.ForceClose()
	if err != nil {
		t.Fatalf("unable to force close channel: %v", err)
	}

	// Bob's to-self output is below Bob's dust value and should be
	// reflected in the ForceCloseSummary.
	commitResolution = closeSummary.CommitResolution
	if commitResolution != nil {
		t.Fatalf("bob incorrectly includes to-self output in " +
			"ForceCloseSummary")
	}

	closeTxHash = closeSummary.CloseTx.TxHash()
	commitTxHash = bobChannel.channelState.LocalCommitment.CommitTx.TxHash()
	if !bytes.Equal(closeTxHash[:], commitTxHash[:]) {
		t.Fatalf("bob: incorrect close transaction txid")
	}
}

// TestDustHTLCFees checks that fees are calculated correctly when HTLCs fall
// below the nodes' dust limit. In these cases, the amount of the dust HTLCs
// should be applied to the commitment transaction fee.
func TestDustHTLCFees(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(3)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	aliceStartingBalance := aliceChannel.channelState.LocalCommitment.LocalBalance

	// This HTLC amount should be lower than the dust limits of both nodes.
	htlcAmount := lnwire.NewMSatFromSatoshis(100)
	htlc, _ := createHTLC(0, htlcAmount)
	if _, err := aliceChannel.AddHTLC(htlc); err != nil {
		t.Fatalf("alice unable to add htlc: %v", err)
	}
	if _, err := bobChannel.ReceiveHTLC(htlc); err != nil {
		t.Fatalf("bob unable to receive htlc: %v", err)
	}
	if err := forceStateTransition(aliceChannel, bobChannel); err != nil {
		t.Fatalf("Can't update the channel state: %v", err)
	}

	// After the transition, we'll ensure that we performed fee accounting
	// properly. Namely, the local+remote+commitfee values should add up to
	// the total capacity of the channel. This same should hold for both
	// sides.
	totalSatoshisAlice := (aliceChannel.channelState.LocalCommitment.LocalBalance +
		aliceChannel.channelState.LocalCommitment.RemoteBalance +
		lnwire.NewMSatFromSatoshis(aliceChannel.channelState.LocalCommitment.CommitFee))
	if totalSatoshisAlice+htlcAmount != lnwire.NewMSatFromSatoshis(aliceChannel.Capacity) {
		t.Fatalf("alice's funds leaked: total satoshis are %v, but channel "+
			"capacity is %v", int64(totalSatoshisAlice),
			int64(aliceChannel.Capacity))
	}
	totalSatoshisBob := (bobChannel.channelState.LocalCommitment.LocalBalance +
		bobChannel.channelState.LocalCommitment.RemoteBalance +
		lnwire.NewMSatFromSatoshis(bobChannel.channelState.LocalCommitment.CommitFee))
	if totalSatoshisBob+htlcAmount != lnwire.NewMSatFromSatoshis(bobChannel.Capacity) {
		t.Fatalf("bob's funds leaked: total satoshis are %v, but channel "+
			"capacity is %v", int64(totalSatoshisBob),
			int64(bobChannel.Capacity))
	}

	// The commitment fee paid should be the same, as there have been no
	// new material outputs added.
	defaultFee := calcStaticFee(0)
	if aliceChannel.channelState.LocalCommitment.CommitFee != defaultFee {
		t.Fatalf("dust htlc amounts not subtracted from commitment fee "+
			"expected %v, got %v", defaultFee,
			aliceChannel.channelState.LocalCommitment.CommitFee)
	}
	if bobChannel.channelState.LocalCommitment.CommitFee != defaultFee {
		t.Fatalf("dust htlc amounts not subtracted from commitment fee "+
			"expected %v, got %v", defaultFee,
			bobChannel.channelState.LocalCommitment.CommitFee)
	}

	// Alice's final balance should reflect the HTLC deficit even though
	// the HTLC was paid to fees as it was trimmed.
	aliceEndBalance := aliceChannel.channelState.LocalCommitment.LocalBalance
	aliceExpectedBalance := aliceStartingBalance - htlcAmount
	if aliceEndBalance != aliceExpectedBalance {
		t.Fatalf("alice not credited for dust: expected %v, got %v",
			aliceExpectedBalance, aliceEndBalance)
	}
}

// TestHTLCDustLimit checks the situation in which an HTLC is larger than one
// channel participant's dust limit, but smaller than the other participant's
// dust limit. In this case, the participants' commitment chains will diverge.
// In one commitment chain, the HTLC will be added as normal, in the other
// chain, the amount of the HTLC will contribute to the fees to be paid.
func TestHTLCDustLimit(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(3)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	// The amount of the HTLC should be above Alice's dust limit and below
	// Bob's dust limit.
	htlcSat := (btcutil.Amount(500) +
		htlcTimeoutFee(aliceChannel.channelState.LocalCommitment.FeePerKw))
	htlcAmount := lnwire.NewMSatFromSatoshis(htlcSat)

	htlc, preimage := createHTLC(0, htlcAmount)
	aliceHtlcIndex, err := aliceChannel.AddHTLC(htlc)
	if err != nil {
		t.Fatalf("alice unable to add htlc: %v", err)
	}
	bobHtlcIndex, err := bobChannel.ReceiveHTLC(htlc)
	if err != nil {
		t.Fatalf("bob unable to receive htlc: %v", err)
	}
	if err := forceStateTransition(aliceChannel, bobChannel); err != nil {
		t.Fatalf("Can't update the channel state: %v", err)
	}

	// At this point, Alice's commitment transaction should have an HTLC,
	// while Bob's should not, because the value falls beneath his dust
	// limit. The amount of the HTLC should be applied to fees in Bob's
	// commitment transaction.
	aliceCommitment := aliceChannel.localCommitChain.tip()
	if len(aliceCommitment.txn.TxOut) != 3 {
		t.Fatalf("incorrect # of outputs: expected %v, got %v",
			3, len(aliceCommitment.txn.TxOut))
	}
	bobCommitment := bobChannel.localCommitChain.tip()
	if len(bobCommitment.txn.TxOut) != 2 {
		t.Fatalf("incorrect # of outputs: expected %v, got %v",
			2, len(bobCommitment.txn.TxOut))
	}
	defaultFee := calcStaticFee(0)
	if bobChannel.channelState.LocalCommitment.CommitFee != defaultFee {
		t.Fatalf("dust htlc amount was subtracted from commitment fee "+
			"expected %v, got %v", defaultFee,
			bobChannel.channelState.LocalCommitment.CommitFee)
	}

	// Settle HTLC and create a new commitment state.
	err = bobChannel.SettleHTLC(preimage, bobHtlcIndex)
	if err != nil {
		t.Fatalf("bob unable to settle inbound htlc: %v", err)
	}
	err = aliceChannel.ReceiveHTLCSettle(preimage, aliceHtlcIndex)
	if err != nil {
		t.Fatalf("alice unable to accept settle of outbound htlc: %v", err)
	}
	if err := forceStateTransition(bobChannel, aliceChannel); err != nil {
		t.Fatalf("state transition error: %v", err)
	}

	// At this point, for Alice's commitment chains, the value of the HTLC
	// should have been added to Alice's balance and TotalSatoshisSent.
	commitment := aliceChannel.localCommitChain.tip()
	if len(commitment.txn.TxOut) != 2 {
		t.Fatalf("incorrect # of outputs: expected %v, got %v",
			2, len(commitment.txn.TxOut))
	}
	if aliceChannel.channelState.TotalMSatSent != htlcAmount {
		t.Fatalf("alice satoshis sent incorrect: expected %v, got %v",
			htlcAmount, aliceChannel.channelState.TotalMSatSent)
	}
}

// TestChannelBalanceDustLimit tests the condition when the remaining balance
// for one of the channel participants is so small as to be considered dust. In
// this case, the output for that participant is removed and all funds (minus
// fees) in the commitment transaction are allocated to the remaining channel
// participant.
//
// TODO(roasbeef): test needs to be fixed after reserve limits are done
func TestChannelBalanceDustLimit(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(3)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	// This amount should leave an amount larger than Alice's dust limit
	// once fees have been subtracted, but smaller than Bob's dust limit.
	// We account in fees for the HTLC we will be adding.
	defaultFee := calcStaticFee(1)
	aliceBalance := aliceChannel.channelState.LocalCommitment.LocalBalance.ToSatoshis()
	htlcSat := aliceBalance - defaultFee
	htlcSat += htlcSuccessFee(
		aliceChannel.channelState.LocalCommitment.FeePerKw,
	)

	htlcAmount := lnwire.NewMSatFromSatoshis(htlcSat)

	htlc, preimage := createHTLC(0, htlcAmount)
	aliceHtlcIndex, err := aliceChannel.AddHTLC(htlc)
	if err != nil {
		t.Fatalf("alice unable to add htlc: %v", err)
	}
	bobHtlcIndex, err := bobChannel.ReceiveHTLC(htlc)
	if err != nil {
		t.Fatalf("bob unable to receive htlc: %v", err)
	}
	if err := forceStateTransition(aliceChannel, bobChannel); err != nil {
		t.Fatalf("state transition error: %v", err)
	}
	err = bobChannel.SettleHTLC(preimage, bobHtlcIndex)
	if err != nil {
		t.Fatalf("bob unable to settle inbound htlc: %v", err)
	}
	err = aliceChannel.ReceiveHTLCSettle(preimage, aliceHtlcIndex)
	if err != nil {
		t.Fatalf("alice unable to accept settle of outbound htlc: %v", err)
	}
	if err := forceStateTransition(bobChannel, aliceChannel); err != nil {
		t.Fatalf("state transition error: %v", err)
	}

	// At the conclusion of this test, in Bob's commitment chains, the
	// output for Alice's balance should have been removed as dust, leaving
	// only a single output that will send the remaining funds in the
	// channel to Bob.
	commitment := bobChannel.localCommitChain.tip()
	if len(commitment.txn.TxOut) != 1 {
		t.Fatalf("incorrect # of outputs: expected %v, got %v",
			1, len(commitment.txn.TxOut))
	}
	if aliceChannel.channelState.TotalMSatSent != htlcAmount {
		t.Fatalf("alice satoshis sent incorrect: expected %v, got %v",
			htlcAmount, aliceChannel.channelState.TotalMSatSent)
	}
}

func TestStateUpdatePersistence(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	const numHtlcs = 4
	htlcAmt := lnwire.NewMSatFromSatoshis(5000)

	var fakeOnionBlob [lnwire.OnionPacketSize]byte
	copy(fakeOnionBlob[:], bytes.Repeat([]byte{0x05}, lnwire.OnionPacketSize))

	// Alice adds 3 HTLCs to the update log, while Bob adds a single HTLC.
	var alicePreimage [32]byte
	copy(alicePreimage[:], bytes.Repeat([]byte{0xaa}, 32))
	var bobPreimage [32]byte
	copy(bobPreimage[:], bytes.Repeat([]byte{0xbb}, 32))
	for i := 0; i < 3; i++ {
		rHash := sha256.Sum256(alicePreimage[:])
		h := &lnwire.UpdateAddHTLC{
			ID:          uint64(i),
			PaymentHash: rHash,
			Amount:      htlcAmt,
			Expiry:      uint32(10),
			OnionBlob:   fakeOnionBlob,
		}

		if _, err := aliceChannel.AddHTLC(h); err != nil {
			t.Fatalf("unable to add alice's htlc: %v", err)
		}
		if _, err := bobChannel.ReceiveHTLC(h); err != nil {
			t.Fatalf("unable to recv alice's htlc: %v", err)
		}
	}
	rHash := sha256.Sum256(bobPreimage[:])
	bobh := &lnwire.UpdateAddHTLC{
		PaymentHash: rHash,
		Amount:      htlcAmt,
		Expiry:      uint32(10),
		OnionBlob:   fakeOnionBlob,
	}
	if _, err := bobChannel.AddHTLC(bobh); err != nil {
		t.Fatalf("unable to add bob's htlc: %v", err)
	}
	if _, err := aliceChannel.ReceiveHTLC(bobh); err != nil {
		t.Fatalf("unable to recv bob's htlc: %v", err)
	}

	// Next, Alice initiates a state transition to include the HTLC's she
	// added above in a new commitment state.
	if err := forceStateTransition(aliceChannel, bobChannel); err != nil {
		t.Fatalf("unable to complete alice's state transition: %v", err)
	}

	// Since the HTLC Bob sent wasn't included in Bob's version of the
	// commitment transaction (but it was in Alice's, as he ACK'd her
	// changes before creating a new state), Bob needs to trigger another
	// state update in order to re-sync their states.
	if err := forceStateTransition(bobChannel, aliceChannel); err != nil {
		t.Fatalf("unable to complete bob's state transition: %v", err)
	}

	// The latest commitment from both sides should have all the HTLCs.
	numAliceOutgoing := aliceChannel.localCommitChain.tail().outgoingHTLCs
	numAliceIncoming := aliceChannel.localCommitChain.tail().incomingHTLCs
	if len(numAliceOutgoing) != 3 {
		t.Fatalf("expected %v htlcs, instead got %v", 3, numAliceOutgoing)
	}
	if len(numAliceIncoming) != 1 {
		t.Fatalf("expected %v htlcs, instead got %v", 1, numAliceIncoming)
	}
	numBobOutgoing := bobChannel.localCommitChain.tail().outgoingHTLCs
	numBobIncoming := bobChannel.localCommitChain.tail().incomingHTLCs
	if len(numBobOutgoing) != 1 {
		t.Fatalf("expected %v htlcs, instead got %v", 1, numBobOutgoing)
	}
	if len(numBobIncoming) != 3 {
		t.Fatalf("expected %v htlcs, instead got %v", 3, numBobIncoming)
	}

	// TODO(roasbeef): also ensure signatures were stored
	//  * ensure expiry matches

	// Now fetch both of the channels created above from disk to simulate a
	// node restart with persistence.
	alicePub := aliceChannel.channelState.IdentityPub
	aliceChannels, err := aliceChannel.channelState.Db.FetchOpenChannels(
		alicePub,
	)
	if err != nil {
		t.Fatalf("unable to fetch channel: %v", err)
	}
	bobPub := bobChannel.channelState.IdentityPub
	bobChannels, err := bobChannel.channelState.Db.FetchOpenChannels(bobPub)
	if err != nil {
		t.Fatalf("unable to fetch channel: %v", err)
	}
	aliceChannelNew, err := NewLightningChannel(
		aliceChannel.signer, nil, aliceChannels[0],
	)
	if err != nil {
		t.Fatalf("unable to create new channel: %v", err)
	}
	bobChannelNew, err := NewLightningChannel(
		bobChannel.signer, nil, bobChannels[0],
	)
	if err != nil {
		t.Fatalf("unable to create new channel: %v", err)
	}

	// The state update logs of the new channels and the old channels
	// should now be identical other than the height the HTLCs were added.
	if aliceChannel.localUpdateLog.logIndex !=
		aliceChannelNew.localUpdateLog.logIndex {
		t.Fatalf("alice log counter: expected %v, got %v",
			aliceChannel.localUpdateLog.logIndex,
			aliceChannelNew.localUpdateLog.logIndex)
	}
	if aliceChannel.remoteUpdateLog.logIndex !=
		aliceChannelNew.remoteUpdateLog.logIndex {
		t.Fatalf("alice log counter: expected %v, got %v",
			aliceChannel.remoteUpdateLog.logIndex,
			aliceChannelNew.remoteUpdateLog.logIndex)
	}
	if aliceChannel.localUpdateLog.Len() !=
		aliceChannelNew.localUpdateLog.Len() {
		t.Fatalf("alice log len: expected %v, got %v",
			aliceChannel.localUpdateLog.Len(),
			aliceChannelNew.localUpdateLog.Len())
	}
	if aliceChannel.remoteUpdateLog.Len() !=
		aliceChannelNew.remoteUpdateLog.Len() {
		t.Fatalf("alice log len: expected %v, got %v",
			aliceChannel.remoteUpdateLog.Len(),
			aliceChannelNew.remoteUpdateLog.Len())
	}
	if bobChannel.localUpdateLog.logIndex !=
		bobChannelNew.localUpdateLog.logIndex {
		t.Fatalf("bob log counter: expected %v, got %v",
			bobChannel.localUpdateLog.logIndex,
			bobChannelNew.localUpdateLog.logIndex)
	}
	if bobChannel.remoteUpdateLog.logIndex !=
		bobChannelNew.remoteUpdateLog.logIndex {
		t.Fatalf("bob log counter: expected %v, got %v",
			bobChannel.remoteUpdateLog.logIndex,
			bobChannelNew.remoteUpdateLog.logIndex)
	}
	if bobChannel.localUpdateLog.Len() !=
		bobChannelNew.localUpdateLog.Len() {
		t.Fatalf("bob log len: expected %v, got %v",
			bobChannel.localUpdateLog.Len(),
			bobChannelNew.localUpdateLog.Len())
	}
	if bobChannel.remoteUpdateLog.Len() !=
		bobChannelNew.remoteUpdateLog.Len() {
		t.Fatalf("bob log len: expected %v, got %v",
			bobChannel.remoteUpdateLog.Len(),
			bobChannelNew.remoteUpdateLog.Len())
	}

	// TODO(roasbeef): expand test to also ensure state revocation log has
	// proper pk scripts

	// Newly generated pkScripts for HTLCs should be the same as in the old channel.
	for _, entry := range aliceChannel.localUpdateLog.htlcIndex {
		htlc := entry.Value.(*PaymentDescriptor)
		restoredHtlc := aliceChannelNew.localUpdateLog.lookupHtlc(htlc.HtlcIndex)
		if !bytes.Equal(htlc.ourPkScript, restoredHtlc.ourPkScript) {
			t.Fatalf("alice ourPkScript in ourLog: expected %X, got %X",
				htlc.ourPkScript[:5], restoredHtlc.ourPkScript[:5])
		}
		if !bytes.Equal(htlc.theirPkScript, restoredHtlc.theirPkScript) {
			t.Fatalf("alice theirPkScript in ourLog: expected %X, got %X",
				htlc.theirPkScript[:5], restoredHtlc.theirPkScript[:5])
		}
	}
	for _, entry := range aliceChannel.remoteUpdateLog.htlcIndex {
		htlc := entry.Value.(*PaymentDescriptor)
		restoredHtlc := aliceChannelNew.remoteUpdateLog.lookupHtlc(htlc.HtlcIndex)
		if !bytes.Equal(htlc.ourPkScript, restoredHtlc.ourPkScript) {
			t.Fatalf("alice ourPkScript in theirLog: expected %X, got %X",
				htlc.ourPkScript[:5], restoredHtlc.ourPkScript[:5])
		}
		if !bytes.Equal(htlc.theirPkScript, restoredHtlc.theirPkScript) {
			t.Fatalf("alice theirPkScript in theirLog: expected %X, got %X",
				htlc.theirPkScript[:5], restoredHtlc.theirPkScript[:5])
		}
	}
	for _, entry := range bobChannel.localUpdateLog.htlcIndex {
		htlc := entry.Value.(*PaymentDescriptor)
		restoredHtlc := bobChannelNew.localUpdateLog.lookupHtlc(htlc.HtlcIndex)
		if !bytes.Equal(htlc.ourPkScript, restoredHtlc.ourPkScript) {
			t.Fatalf("bob ourPkScript in ourLog: expected %X, got %X",
				htlc.ourPkScript[:5], restoredHtlc.ourPkScript[:5])
		}
		if !bytes.Equal(htlc.theirPkScript, restoredHtlc.theirPkScript) {
			t.Fatalf("bob theirPkScript in ourLog: expected %X, got %X",
				htlc.theirPkScript[:5], restoredHtlc.theirPkScript[:5])
		}
	}
	for _, entry := range bobChannel.remoteUpdateLog.htlcIndex {
		htlc := entry.Value.(*PaymentDescriptor)
		restoredHtlc := bobChannelNew.remoteUpdateLog.lookupHtlc(htlc.HtlcIndex)
		if !bytes.Equal(htlc.ourPkScript, restoredHtlc.ourPkScript) {
			t.Fatalf("bob ourPkScript in theirLog: expected %X, got %X",
				htlc.ourPkScript[:5], restoredHtlc.ourPkScript[:5])
		}
		if !bytes.Equal(htlc.theirPkScript, restoredHtlc.theirPkScript) {
			t.Fatalf("bob theirPkScript in theirLog: expected %X, got %X",
				htlc.theirPkScript[:5], restoredHtlc.theirPkScript[:5])
		}
	}

	// Now settle all the HTLCs, then force a state update. The state
	// update should succeed as both sides have identical.
	for i := 0; i < 3; i++ {
		err := bobChannelNew.SettleHTLC(alicePreimage, uint64(i))
		if err != nil {
			t.Fatalf("unable to settle htlc #%v: %v", i, err)
		}
		err = aliceChannelNew.ReceiveHTLCSettle(alicePreimage, uint64(i))
		if err != nil {
			t.Fatalf("unable to settle htlc#%v: %v", i, err)
		}
	}
	err = aliceChannelNew.SettleHTLC(bobPreimage, 0)
	if err != nil {
		t.Fatalf("unable to settle htlc: %v", err)
	}
	err = bobChannelNew.ReceiveHTLCSettle(bobPreimage, 0)
	if err != nil {
		t.Fatalf("unable to settle htlc: %v", err)
	}

	// Similar to the two transitions above, as both Bob and Alice added
	// entries to the update log before a state transition was initiated by
	// either side, both sides are required to trigger an update in order
	// to lock in their changes.
	if err := forceStateTransition(aliceChannelNew, bobChannelNew); err != nil {
		t.Fatalf("unable to update commitments: %v", err)
	}
	if err := forceStateTransition(bobChannelNew, aliceChannelNew); err != nil {
		t.Fatalf("unable to update commitments: %v", err)
	}

	// The amounts transferred should been updated as per the amounts in
	// the HTLCs
	if aliceChannelNew.channelState.TotalMSatSent != htlcAmt*3 {
		t.Fatalf("expected %v alice satoshis sent, got %v",
			htlcAmt*3, aliceChannelNew.channelState.TotalMSatSent)
	}
	if aliceChannelNew.channelState.TotalMSatReceived != htlcAmt {
		t.Fatalf("expected %v alice satoshis received, got %v",
			htlcAmt, aliceChannelNew.channelState.TotalMSatReceived)
	}
	if bobChannelNew.channelState.TotalMSatSent != htlcAmt {
		t.Fatalf("expected %v bob satoshis sent, got %v",
			htlcAmt, bobChannel.channelState.TotalMSatSent)
	}
	if bobChannelNew.channelState.TotalMSatReceived != htlcAmt*3 {
		t.Fatalf("expected %v bob satoshis sent, got %v",
			htlcAmt*3, bobChannel.channelState.TotalMSatReceived)
	}

	// As a final test, we'll ensure that the HTLC counters for both sides
	// has been persisted properly. If we instruct Alice to add a new HTLC,
	// it should have an index of 3. If we instruct Bob to do the
	// same, it should have an index of 1.
	aliceHtlcIndex, err := aliceChannel.AddHTLC(bobh)
	if err != nil {
		t.Fatalf("unable to add htlc: %v", err)
	}
	if aliceHtlcIndex != 3 {
		t.Fatalf("wrong htlc index: expected %v, got %v", 3, aliceHtlcIndex)
	}
	bobHtlcIndex, err := bobChannel.AddHTLC(bobh)
	if err != nil {
		t.Fatalf("unable to add htlc: %v", err)
	}
	if bobHtlcIndex != 1 {
		t.Fatalf("wrong htlc index: expected %v, got %v", 1, aliceHtlcIndex)
	}
}

func TestCancelHTLC(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(5)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	// Add a new HTLC from Alice to Bob, then trigger a new state
	// transition in order to include it in the latest state.
	htlcAmt := lnwire.NewMSatFromSatoshis(btcutil.SatoshiPerBitcoin)

	var preImage [32]byte
	copy(preImage[:], bytes.Repeat([]byte{0xaa}, 32))
	htlc := &lnwire.UpdateAddHTLC{
		PaymentHash: sha256.Sum256(preImage[:]),
		Amount:      htlcAmt,
		Expiry:      10,
	}

	aliceHtlcIndex, err := aliceChannel.AddHTLC(htlc)
	if err != nil {
		t.Fatalf("unable to add alice htlc: %v", err)
	}
	bobHtlcIndex, err := bobChannel.ReceiveHTLC(htlc)
	if err != nil {
		t.Fatalf("unable to add bob htlc: %v", err)
	}
	if err := forceStateTransition(aliceChannel, bobChannel); err != nil {
		t.Fatalf("unable to create new commitment state: %v", err)
	}

	// With the HTLC committed, Alice's balance should reflect the clearing
	// of the new HTLC.
	aliceExpectedBalance := btcutil.Amount(btcutil.SatoshiPerBitcoin*4) -
		calcStaticFee(1)
	if aliceChannel.channelState.LocalCommitment.LocalBalance.ToSatoshis() !=
		aliceExpectedBalance {
		t.Fatalf("Alice's balance is wrong: expected %v, got %v",
			aliceExpectedBalance,
			aliceChannel.channelState.LocalCommitment.LocalBalance.ToSatoshis())
	}

	// Now, with the HTLC committed on both sides, trigger a cancellation
	// from Bob to Alice, removing the HTLC.
	err = bobChannel.FailHTLC(bobHtlcIndex, []byte("failreason"))
	if err != nil {
		t.Fatalf("unable to cancel HTLC: %v", err)
	}
	err = aliceChannel.ReceiveFailHTLC(aliceHtlcIndex, []byte("bad"))
	if err != nil {
		t.Fatalf("unable to recv htlc cancel: %v", err)
	}

	// Now trigger another state transition, the HTLC should now be removed
	// from both sides, with balances reflected.
	if err := forceStateTransition(bobChannel, aliceChannel); err != nil {
		t.Fatalf("unable to create new commitment: %v", err)
	}

	// Now HTLCs should be present on the commitment transaction for either
	// side.
	if len(aliceChannel.localCommitChain.tip().outgoingHTLCs) != 0 ||
		len(aliceChannel.remoteCommitChain.tip().outgoingHTLCs) != 0 {
		t.Fatalf("htlc's still active from alice's POV")
	}
	if len(aliceChannel.localCommitChain.tip().incomingHTLCs) != 0 ||
		len(aliceChannel.remoteCommitChain.tip().incomingHTLCs) != 0 {
		t.Fatalf("htlc's still active from alice's POV")
	}
	if len(bobChannel.localCommitChain.tip().outgoingHTLCs) != 0 ||
		len(bobChannel.remoteCommitChain.tip().outgoingHTLCs) != 0 {
		t.Fatalf("htlc's still active from bob's POV")
	}
	if len(bobChannel.localCommitChain.tip().incomingHTLCs) != 0 ||
		len(bobChannel.remoteCommitChain.tip().incomingHTLCs) != 0 {
		t.Fatalf("htlc's still active from bob's POV")
	}

	expectedBalance := btcutil.Amount(btcutil.SatoshiPerBitcoin * 5)
	if aliceChannel.channelState.LocalCommitment.LocalBalance.ToSatoshis() !=
		expectedBalance-calcStaticFee(0) {

		t.Fatalf("balance is wrong: expected %v, got %v",
			aliceChannel.channelState.LocalCommitment.LocalBalance.ToSatoshis(),
			expectedBalance-calcStaticFee(0))
	}
	if aliceChannel.channelState.LocalCommitment.RemoteBalance.ToSatoshis() !=
		expectedBalance {

		t.Fatalf("balance is wrong: expected %v, got %v",
			aliceChannel.channelState.LocalCommitment.RemoteBalance.ToSatoshis(),
			expectedBalance)
	}
	if bobChannel.channelState.LocalCommitment.LocalBalance.ToSatoshis() !=
		expectedBalance {

		t.Fatalf("balance is wrong: expected %v, got %v",
			bobChannel.channelState.LocalCommitment.LocalBalance.ToSatoshis(),
			expectedBalance)
	}
	if bobChannel.channelState.LocalCommitment.RemoteBalance.ToSatoshis() !=
		expectedBalance-calcStaticFee(0) {

		t.Fatalf("balance is wrong: expected %v, got %v",
			bobChannel.channelState.LocalCommitment.RemoteBalance.ToSatoshis(),
			expectedBalance-calcStaticFee(0))
	}
}

func TestCooperativeCloseDustAdherence(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(5)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	aliceFeeRate := uint64(aliceChannel.channelState.LocalCommitment.FeePerKw)
	bobFeeRate := uint64(bobChannel.channelState.LocalCommitment.FeePerKw)

	setDustLimit := func(dustVal btcutil.Amount) {
		aliceChannel.channelState.LocalChanCfg.DustLimit = dustVal
		aliceChannel.channelState.RemoteChanCfg.DustLimit = dustVal
		bobChannel.channelState.LocalChanCfg.DustLimit = dustVal
		bobChannel.channelState.RemoteChanCfg.DustLimit = dustVal
	}

	resetChannelState := func() {
		aliceChannel.status = channelOpen
		bobChannel.status = channelOpen
	}

	setBalances := func(aliceBalance, bobBalance lnwire.MilliSatoshi) {
		aliceChannel.channelState.LocalCommitment.LocalBalance = aliceBalance
		aliceChannel.channelState.LocalCommitment.RemoteBalance = bobBalance
		bobChannel.channelState.LocalCommitment.LocalBalance = bobBalance
		bobChannel.channelState.LocalCommitment.RemoteBalance = aliceBalance
	}

	aliceDeliveryScript := bobsPrivKey[:]
	bobDeliveryScript := testHdSeed[:]

	// We'll start be initializing the limit of both Alice and Bob to 10k
	// satoshis.
	dustLimit := btcutil.Amount(10000)
	setDustLimit(dustLimit)

	// Both sides currently have over 1 BTC settled as part of their
	// balances. As a result, performing a cooperative closure now result
	// in both sides having an output within the closure transaction.
	aliceFee := btcutil.Amount(aliceChannel.CalcFee(aliceFeeRate)) + 1000
	aliceSig, _, _, err := aliceChannel.CreateCloseProposal(aliceFee,
		aliceDeliveryScript, bobDeliveryScript)
	if err != nil {
		t.Fatalf("unable to close channel: %v", err)
	}
	aliceCloseSig := append(aliceSig, byte(txscript.SigHashAll))

	bobFee := btcutil.Amount(bobChannel.CalcFee(bobFeeRate)) + 1000
	bobSig, _, _, err := bobChannel.CreateCloseProposal(bobFee,
		bobDeliveryScript, aliceDeliveryScript)
	if err != nil {
		t.Fatalf("unable to close channel: %v", err)
	}
	bobCloseSig := append(bobSig, byte(txscript.SigHashAll))

	closeTx, _, err := bobChannel.CompleteCooperativeClose(
		bobCloseSig, aliceCloseSig,
		bobDeliveryScript, aliceDeliveryScript, bobFee)
	if err != nil {
		t.Fatalf("unable to accept channel close: %v", err)
	}

	// The closure transaction should have exactly two outputs.
	if len(closeTx.TxOut) != 2 {
		t.Fatalf("close tx has wrong number of outputs: expected %v "+
			"got %v", 2, len(closeTx.TxOut))
	}

	// We'll reset the channel states before proceeding to our nest test.
	resetChannelState()

	// Next we'll modify the current balances and dust limits such that
	// Bob's current balance is above _below_ his dust limit.
	aliceBal := lnwire.NewMSatFromSatoshis(btcutil.SatoshiPerBitcoin)
	bobBal := lnwire.NewMSatFromSatoshis(250)
	setBalances(aliceBal, bobBal)

	// Attempt another cooperative channel closure. It should succeed
	// without any issues.
	aliceSig, _, _, err = aliceChannel.CreateCloseProposal(aliceFee,
		aliceDeliveryScript, bobDeliveryScript)
	if err != nil {
		t.Fatalf("unable to close channel: %v", err)
	}
	aliceCloseSig = append(aliceSig, byte(txscript.SigHashAll))

	bobSig, _, _, err = bobChannel.CreateCloseProposal(bobFee,
		bobDeliveryScript, aliceDeliveryScript)
	if err != nil {
		t.Fatalf("unable to close channel: %v", err)
	}
	bobCloseSig = append(bobSig, byte(txscript.SigHashAll))

	closeTx, _, err = bobChannel.CompleteCooperativeClose(
		bobCloseSig, aliceCloseSig,
		bobDeliveryScript, aliceDeliveryScript, bobFee)
	if err != nil {
		t.Fatalf("unable to accept channel close: %v", err)
	}

	// The closure transaction should only have a single output, and that
	// output should be Alice's balance.
	if len(closeTx.TxOut) != 1 {
		t.Fatalf("close tx has wrong number of outputs: expected %v "+
			"got %v", 1, len(closeTx.TxOut))
	}
	commitFee := aliceChannel.channelState.LocalCommitment.CommitFee
	aliceExpectedBalance := aliceBal.ToSatoshis() - aliceFee + commitFee
	if closeTx.TxOut[0].Value != int64(aliceExpectedBalance) {
		t.Fatalf("alice's balance is incorrect: expected %v, got %v",
			aliceExpectedBalance,
			int64(closeTx.TxOut[0].Value))
	}

	// Finally, we'll modify the current balances and dust limits such that
	// Alice's current balance is _below_ his her limit.
	setBalances(bobBal, aliceBal)
	resetChannelState()

	// Our final attempt at another cooperative channel closure. It should
	// succeed without any issues.
	aliceSig, _, _, err = aliceChannel.CreateCloseProposal(
		aliceFee, aliceDeliveryScript, bobDeliveryScript,
	)
	if err != nil {
		t.Fatalf("unable to close channel: %v", err)
	}
	aliceCloseSig = append(aliceSig, byte(txscript.SigHashAll))

	bobSig, _, _, err = bobChannel.CreateCloseProposal(
		bobFee, bobDeliveryScript, aliceDeliveryScript,
	)
	if err != nil {
		t.Fatalf("unable to close channel: %v", err)
	}
	bobCloseSig = append(bobSig, byte(txscript.SigHashAll))

	closeTx, _, err = bobChannel.CompleteCooperativeClose(
		bobCloseSig, aliceCloseSig,
		bobDeliveryScript, aliceDeliveryScript, bobFee)
	if err != nil {
		t.Fatalf("unable to accept channel close: %v", err)
	}

	// The closure transaction should only have a single output, and that
	// output should be Bob's balance.
	if len(closeTx.TxOut) != 1 {
		t.Fatalf("close tx has wrong number of outputs: expected %v "+
			"got %v", 1, len(closeTx.TxOut))
	}
	if closeTx.TxOut[0].Value != int64(aliceBal.ToSatoshis()) {
		t.Fatalf("bob's balance is incorrect: expected %v, got %v",
			aliceBal.ToSatoshis(), closeTx.TxOut[0].Value)
	}
}

// TestUpdateFeeFail tests that the signature verification will fail if they
// fee updates are out of sync.
func TestUpdateFeeFail(t *testing.T) {
	t.Parallel()

	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	// Bob receives the update, that will apply to his commitment
	// transaction.
	bobChannel.ReceiveUpdateFee(111)

	// Alice sends signature for commitment that does not cover any fee
	// update.
	aliceSig, aliceHtlcSigs, err := aliceChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("alice unable to sign commitment: %v", err)
	}

	// Bob verifies this commit, meaning that he checks that it is
	// consistent everything he has received. This should fail, since he got
	// the fee update, but Alice never sent it.
	err = bobChannel.ReceiveNewCommitment(aliceSig, aliceHtlcSigs)
	if err == nil {
		t.Fatalf("expected bob to fail receiving alice's signature")
	}

}

// TestUpdateFeeSenderCommits verifies that the state machine progresses as
// expected if we send a fee update, and then the sender of the fee update
// sends a commitment signature.
func TestUpdateFeeSenderCommits(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	paymentPreimage := bytes.Repeat([]byte{1}, 32)
	paymentHash := sha256.Sum256(paymentPreimage)
	htlc := &lnwire.UpdateAddHTLC{
		PaymentHash: paymentHash,
		Amount:      btcutil.SatoshiPerBitcoin,
		Expiry:      uint32(5),
	}

	// First Alice adds the outgoing HTLC to her local channel's state
	// update log. Then Alice sends this wire message over to Bob who
	// adds this htlc to his remote state update log.
	if _, err := aliceChannel.AddHTLC(htlc); err != nil {
		t.Fatalf("unable to add htlc: %v", err)
	}
	if _, err := bobChannel.ReceiveHTLC(htlc); err != nil {
		t.Fatalf("unable to recv htlc: %v", err)
	}

	// Simulate Alice sending update fee message to bob.
	fee := btcutil.Amount(111)
	aliceChannel.UpdateFee(fee)
	bobChannel.ReceiveUpdateFee(fee)

	// Alice signs a commitment, which will cover everything sent to Bob
	// (the HTLC and the fee update), and everything acked by Bob (nothing
	// so far).
	aliceSig, aliceHtlcSigs, err := aliceChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("alice unable to sign commitment: %v", err)
	}

	// Bob receives this signature message, and verifies that it is
	// consistent with the state he had for Alice, including the received
	// HTLC and fee update.
	err = bobChannel.ReceiveNewCommitment(aliceSig, aliceHtlcSigs)
	if err != nil {
		t.Fatalf("bob unable to process alice's new commitment: %v", err)
	}

	if bobChannel.channelState.LocalCommitment.FeePerKw == fee {
		t.Fatalf("bob's feePerKw was unexpectedly locked in")
	}

	// Bob can revoke the prior commitment he had. This should lock in the
	// fee update for him.
	bobRevocation, _, err := bobChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("unable to generate bob revocation: %v", err)
	}

	if bobChannel.channelState.LocalCommitment.FeePerKw != fee {
		t.Fatalf("bob's feePerKw was not locked in")
	}

	// Bob commits to all updates he has received from Alice. This includes
	// the HTLC he received, and the fee update.
	bobSig, bobHtlcSigs, err := bobChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("bob unable to sign alice's commitment: %v", err)
	}

	// Alice receives the revocation of the old one, and can now assume
	// that Bob's received everything up to the signature she sent,
	// including the HTLC and fee update.
	if _, err := aliceChannel.ReceiveRevocation(bobRevocation); err != nil {
		t.Fatalf("alice unable to process bob's revocation: %v", err)
	}

	// Alice receives new signature from Bob, and assumes this covers the
	// changes.
	err = aliceChannel.ReceiveNewCommitment(bobSig, bobHtlcSigs)
	if err != nil {
		t.Fatalf("alice unable to process bob's new commitment: %v", err)
	}

	if aliceChannel.channelState.LocalCommitment.FeePerKw == fee {
		t.Fatalf("alice's feePerKw was unexpectedly locked in")
	}

	// Alice can revoke the old commitment, which will lock in the fee
	// update.
	aliceRevocation, _, err := aliceChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("unable to revoke alice channel: %v", err)
	}

	if aliceChannel.channelState.LocalCommitment.FeePerKw != fee {
		t.Fatalf("alice's feePerKw was not locked in")
	}

	// Bob receives revocation from Alice.
	if _, err := bobChannel.ReceiveRevocation(aliceRevocation); err != nil {
		t.Fatalf("bob unable to process alice's revocation: %v", err)
	}

}

// TestUpdateFeeReceiverCommits tests that the state machine progresses as
// expected if we send a fee update, and then the receiver of the fee update
// sends a commitment signature.
func TestUpdateFeeReceiverCommits(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	paymentPreimage := bytes.Repeat([]byte{1}, 32)
	paymentHash := sha256.Sum256(paymentPreimage)
	htlc := &lnwire.UpdateAddHTLC{
		PaymentHash: paymentHash,
		Amount:      btcutil.SatoshiPerBitcoin,
		Expiry:      uint32(5),
	}

	// First Alice adds the outgoing HTLC to her local channel's state
	// update log. Then Alice sends this wire message over to Bob who
	// adds this htlc to his remote state update log.
	if _, err := aliceChannel.AddHTLC(htlc); err != nil {
		t.Fatalf("unable to add htlc: %v", err)
	}
	if _, err := bobChannel.ReceiveHTLC(htlc); err != nil {
		t.Fatalf("unable to recv htlc: %v", err)
	}

	// Simulate Alice sending update fee message to bob
	fee := btcutil.Amount(111)
	aliceChannel.UpdateFee(fee)
	bobChannel.ReceiveUpdateFee(fee)

	// Bob commits to every change he has sent since last time (none). He
	// does not commit to the received HTLC and fee update, since Alice
	// cannot know if he has received them.
	bobSig, bobHtlcSigs, err := bobChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("alice unable to sign commitment: %v", err)
	}

	// Alice receives this signature message, and verifies that it is
	// consistent with the remote state, not including any of the updates.
	err = aliceChannel.ReceiveNewCommitment(bobSig, bobHtlcSigs)
	if err != nil {
		t.Fatalf("bob unable to process alice's new commitment: %v", err)
	}

	// Alice can revoke the prior commitment she had, this will ack
	// everything received before last commitment signature, but in this
	// case that is nothing.
	aliceRevocation, _, err := aliceChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("unable to generate bob revocation: %v", err)
	}

	// Bob receives the revocation of the old commitment
	if _, err := bobChannel.ReceiveRevocation(aliceRevocation); err != nil {
		t.Fatalf("alice unable to process bob's revocation: %v", err)
	}

	// Alice will sign next commitment. Since she sent the revocation, she
	// also ack'ed everything received, but in this case this is nothing.
	// Since she sent the two updates, this signature will cover those two.
	aliceSig, aliceHtlcSigs, err := aliceChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("bob unable to sign alice's commitment: %v", err)
	}

	// Bob gets the signature for the new commitment from Alice. He assumes
	// this covers everything received from alice, including the two updates.
	err = bobChannel.ReceiveNewCommitment(aliceSig, aliceHtlcSigs)
	if err != nil {
		t.Fatalf("alice unable to process bob's new commitment: %v", err)
	}

	if bobChannel.channelState.LocalCommitment.FeePerKw == fee {
		t.Fatalf("bob's feePerKw was unexpectedly locked in")
	}

	// Bob can revoke the old commitment. This will ack what he has
	// received, including the HTLC and fee update. This will lock in the
	// fee update for bob.
	bobRevocation, _, err := bobChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("unable to revoke alice channel: %v", err)
	}

	if bobChannel.channelState.LocalCommitment.FeePerKw != fee {
		t.Fatalf("bob's feePerKw was not locked in")
	}

	// Bob will send a new signature, which will cover what he just acked:
	// the HTLC and fee update.
	bobSig, bobHtlcSigs, err = bobChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("alice unable to sign commitment: %v", err)
	}

	// Alice receives revocation from Bob, and can now be sure that Bob
	// received the two updates, and they are considered locked in.
	if _, err := aliceChannel.ReceiveRevocation(bobRevocation); err != nil {
		t.Fatalf("bob unable to process alice's revocation: %v", err)
	}

	// Alice will receive the signature from Bob, which will cover what was
	// just acked by his revocation.
	err = aliceChannel.ReceiveNewCommitment(bobSig, bobHtlcSigs)
	if err != nil {
		t.Fatalf("alice unable to process bob's new commitment: %v", err)
	}

	if aliceChannel.channelState.LocalCommitment.FeePerKw == fee {
		t.Fatalf("alice's feePerKw was unexpectedly locked in")
	}

	// After Alice now revokes her old commitment, the fee update should
	// lock in.
	aliceRevocation, _, err = aliceChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("unable to generate bob revocation: %v", err)
	}

	if aliceChannel.channelState.LocalCommitment.FeePerKw != fee {
		t.Fatalf("Alice's feePerKw was not locked in")
	}

	// Bob receives revocation from Alice.
	if _, err := bobChannel.ReceiveRevocation(aliceRevocation); err != nil {
		t.Fatalf("bob unable to process alice's revocation: %v", err)
	}
}

// TestUpdateFeeReceiverSendsUpdate tests that receiving a fee update as channel
// initiator fails, and that trying to initiate fee update as non-initiation
// fails.
func TestUpdateFeeReceiverSendsUpdate(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	// Since Alice is the channel initiator, she should fail when receiving
	// fee update
	fee := btcutil.Amount(111)
	err = aliceChannel.ReceiveUpdateFee(fee)
	if err == nil {
		t.Fatalf("expected alice to fail receiving fee update")
	}

	// Similarly, initiating fee update should fail for Bob.
	err = bobChannel.UpdateFee(fee)
	if err == nil {
		t.Fatalf("expected bob to fail initiating fee update")
	}
}

// Test that if multiple update fee messages are sent consecutively, then the
// last one is the one that is being committed to.
func TestUpdateFeeMultipleUpdates(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	// Simulate Alice sending update fee message to bob.
	fee1 := btcutil.Amount(111)
	fee2 := btcutil.Amount(222)
	fee := btcutil.Amount(333)
	aliceChannel.UpdateFee(fee1)
	aliceChannel.UpdateFee(fee2)
	aliceChannel.UpdateFee(fee)

	// Alice signs a commitment, which will cover everything sent to Bob
	// (the HTLC and the fee update), and everything acked by Bob (nothing
	// so far).
	aliceSig, aliceHtlcSigs, err := aliceChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("alice unable to sign commitment: %v", err)
	}

	bobChannel.ReceiveUpdateFee(fee1)
	bobChannel.ReceiveUpdateFee(fee2)
	bobChannel.ReceiveUpdateFee(fee)

	// Bob receives this signature message, and verifies that it is
	// consistent with the state he had for Alice, including the received
	// HTLC and fee update.
	err = bobChannel.ReceiveNewCommitment(aliceSig, aliceHtlcSigs)
	if err != nil {
		t.Fatalf("bob unable to process alice's new commitment: %v", err)
	}

	if bobChannel.channelState.LocalCommitment.FeePerKw == fee {
		t.Fatalf("bob's feePerKw was unexpectedly locked in")
	}

	// Alice sending more fee updates now should not mess up the old fee
	// they both committed to.
	fee3 := btcutil.Amount(444)
	fee4 := btcutil.Amount(555)
	fee5 := btcutil.Amount(666)
	aliceChannel.UpdateFee(fee3)
	aliceChannel.UpdateFee(fee4)
	aliceChannel.UpdateFee(fee5)
	bobChannel.ReceiveUpdateFee(fee3)
	bobChannel.ReceiveUpdateFee(fee4)
	bobChannel.ReceiveUpdateFee(fee5)

	// Bob can revoke the prior commitment he had. This should lock in the
	// fee update for him.
	bobRevocation, _, err := bobChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("unable to generate bob revocation: %v", err)
	}

	if bobChannel.channelState.LocalCommitment.FeePerKw != fee {
		t.Fatalf("bob's feePerKw was not locked in")
	}

	// Bob commits to all updates he has received from Alice. This includes
	// the HTLC he received, and the fee update.
	bobSig, bobHtlcSigs, err := bobChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("bob unable to sign alice's commitment: %v", err)
	}

	// Alice receives the revocation of the old one, and can now assume that
	// Bob's received everything up to the signature she sent, including the
	// HTLC and fee update.
	if _, err := aliceChannel.ReceiveRevocation(bobRevocation); err != nil {
		t.Fatalf("alice unable to process bob's revocation: %v", err)
	}

	// Alice receives new signature from Bob, and assumes this covers the
	// changes.
	if err := aliceChannel.ReceiveNewCommitment(bobSig, bobHtlcSigs); err != nil {
		t.Fatalf("alice unable to process bob's new commitment: %v", err)
	}

	if aliceChannel.channelState.LocalCommitment.FeePerKw == fee {
		t.Fatalf("alice's feePerKw was unexpectedly locked in")
	}

	// Alice can revoke the old commitment, which will lock in the fee
	// update.
	aliceRevocation, _, err := aliceChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("unable to revoke alice channel: %v", err)
	}

	if aliceChannel.channelState.LocalCommitment.FeePerKw != fee {
		t.Fatalf("alice's feePerKw was not locked in")
	}

	// Bob receives revocation from Alice.
	if _, err := bobChannel.ReceiveRevocation(aliceRevocation); err != nil {
		t.Fatalf("bob unable to process alice's revocation: %v", err)
	}
}

// TestAddHTLCNegativeBalance tests that if enough HTLC's are added to the
// state machine to drive the balance to zero, then the next HTLC attempted to
// be added will result in an error being returned.
func TestAddHTLCNegativeBalance(t *testing.T) {
	t.Parallel()

	// We'll kick off the test by creating our channels which both are
	// loaded with 5 BTC each.
	aliceChannel, _, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	// First, we'll add 5 HTLCs of 1 BTC each to Alice's commitment.
	const numHTLCs = 4
	htlcAmt := lnwire.NewMSatFromSatoshis(btcutil.SatoshiPerBitcoin)
	for i := 0; i < numHTLCs; i++ {
		htlc, _ := createHTLC(i, htlcAmt)
		if _, err := aliceChannel.AddHTLC(htlc); err != nil {
			t.Fatalf("unable to add htlc: %v", err)
		}
	}

	// We'll then craft another HTLC with 2 BTC to add to Alice's channel.
	// This attempt should put Alice in the negative, meaning she should
	// reject the HTLC.
	htlc, _ := createHTLC(numHTLCs+1, htlcAmt*2)
	_, err = aliceChannel.AddHTLC(htlc)
	if err != ErrInsufficientBalance {
		t.Fatalf("expected insufficient balance, instead got: %v", err)
	}
}

// assertNoChanSyncNeeded is a helper function that asserts that upon restart,
// two channels conclude that they're fully synchronized and don't need to
// retransmit any new messages.
func assertNoChanSyncNeeded(t *testing.T, aliceChannel *LightningChannel,
	bobChannel *LightningChannel) {

	_, _, line, _ := runtime.Caller(1)

	aliceChanSyncMsg, err := aliceChannel.ChanSyncMsg()
	if err != nil {
		t.Fatalf("line #%v: unable to produce chan sync msg: %v",
			line, err)
	}
	bobMsgsToSend, err := bobChannel.ProcessChanSyncMsg(aliceChanSyncMsg)
	if err != nil {
		t.Fatalf("line #%v: unable to process ChannelReestablish "+
			"msg: %v", line, err)
	}
	if len(bobMsgsToSend) != 0 {
		t.Fatalf("line #%v: bob shouldn't have to send any messages, "+
			"instead wants to send: %v", line, spew.Sdump(bobMsgsToSend))
	}

	bobChanSyncMsg, err := bobChannel.ChanSyncMsg()
	if err != nil {
		t.Fatalf("line #%v: unable to produce chan sync msg: %v",
			line, err)
	}
	aliceMsgsToSend, err := aliceChannel.ProcessChanSyncMsg(bobChanSyncMsg)
	if err != nil {
		t.Fatalf("line #%v: unable to process ChannelReestablish "+
			"msg: %v", line, err)
	}
	if len(bobMsgsToSend) != 0 {
		t.Fatalf("line #%v: alice shouldn't have to send any "+
			"messages, instead wants to send: %v", line,
			spew.Sdump(aliceMsgsToSend))
	}
}

// TestChanSyncFullySynced tests that after a successful commitment exchange,
// and a forced restart, both nodes conclude that they're fully synchronized
// and don't need to retransmit any messages.
func TestChanSyncFullySynced(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	// If we exchange channel sync messages from the get-go , then both
	// sides should conclude that no further synchronization is needed.
	assertNoChanSyncNeeded(t, aliceChannel, bobChannel)

	// Next, we'll create an HTLC for Alice to extend to Bob.
	var paymentPreimage [32]byte
	copy(paymentPreimage[:], bytes.Repeat([]byte{1}, 32))
	paymentHash := sha256.Sum256(paymentPreimage[:])
	htlcAmt := lnwire.NewMSatFromSatoshis(btcutil.SatoshiPerBitcoin)
	htlc := &lnwire.UpdateAddHTLC{
		PaymentHash: paymentHash,
		Amount:      htlcAmt,
		Expiry:      uint32(5),
	}
	aliceHtlcIndex, err := aliceChannel.AddHTLC(htlc)
	if err != nil {
		t.Fatalf("unable to add htlc: %v", err)
	}
	bobHtlcIndex, err := bobChannel.ReceiveHTLC(htlc)
	if err != nil {
		t.Fatalf("unable to recv htlc: %v", err)
	}

	// Then we'll initiate a state transition to lock in this new HTLC.
	if err := forceStateTransition(aliceChannel, bobChannel); err != nil {
		t.Fatalf("unable to complete alice's state transition: %v", err)
	}

	// At this point, if both sides generate a ChannelReestablish message,
	// they should both conclude that they're fully in sync.
	assertNoChanSyncNeeded(t, aliceChannel, bobChannel)

	// If bob settles the HTLC, and then initiates a state transition, they
	// should both still think that they're in sync.
	err = bobChannel.SettleHTLC(paymentPreimage, bobHtlcIndex)
	if err != nil {
		t.Fatalf("unable to settle htlc: %v", err)
	}
	err = aliceChannel.ReceiveHTLCSettle(paymentPreimage, aliceHtlcIndex)
	if err != nil {
		t.Fatalf("unable to settle htlc: %v", err)
	}

	// Next, we'll complete Bob's state transition, and assert again that
	// they think they're fully synced.
	if err := forceStateTransition(bobChannel, aliceChannel); err != nil {
		t.Fatalf("unable to complete bob's state transition: %v", err)
	}
	assertNoChanSyncNeeded(t, aliceChannel, bobChannel)

	// Finally, if we simulate a restart on both sides, then both should
	// still conclude that they don't need to synchronize their state.
	alicePub := aliceChannel.channelState.IdentityPub
	aliceChannels, err := aliceChannel.channelState.Db.FetchOpenChannels(
		alicePub,
	)
	if err != nil {
		t.Fatalf("unable to fetch channel: %v", err)
	}
	bobPub := bobChannel.channelState.IdentityPub
	bobChannels, err := bobChannel.channelState.Db.FetchOpenChannels(bobPub)
	if err != nil {
		t.Fatalf("unable to fetch channel: %v", err)
	}
	aliceChannelNew, err := NewLightningChannel(
		aliceChannel.signer, nil, aliceChannels[0],
	)
	if err != nil {
		t.Fatalf("unable to create new channel: %v", err)
	}
	defer aliceChannelNew.Stop()
	bobChannelNew, err := NewLightningChannel(
		bobChannel.signer, nil, bobChannels[0],
	)
	if err != nil {
		t.Fatalf("unable to create new channel: %v", err)
	}
	defer bobChannelNew.Stop()

	assertNoChanSyncNeeded(t, aliceChannelNew, bobChannelNew)
}

// restartChannel reads the passe channel from disk, and returns a newly
// initialized instance. This simulates one party restarting and losing their
// in memory state.
func restartChannel(channelOld *LightningChannel) (*LightningChannel, error) {
	nodePub := channelOld.channelState.IdentityPub
	nodeChannels, err := channelOld.channelState.Db.FetchOpenChannels(
		nodePub,
	)
	if err != nil {
		return nil, err
	}

	channelNew, err := NewLightningChannel(
		channelOld.signer, channelOld.pCache, nodeChannels[0],
	)
	if err != nil {
		return nil, err
	}

	return channelNew, nil
}

// TestChanSyncOweCommitment tests that if Bob restarts (and then Alice) before
// he receives Alice's CommitSig message, then Alice concludes that she needs
// to re-send the CommitDiff. After the diff has been sent, both nodes should
// resynchronize and be able to complete the dangling commit.
func TestChanSyncOweCommitment(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	var fakeOnionBlob [lnwire.OnionPacketSize]byte
	copy(fakeOnionBlob[:], bytes.Repeat([]byte{0x05}, lnwire.OnionPacketSize))

	// We'll start off the scenario with Bob sending 3 HTLC's to Alice in a
	// single state update.
	htlcAmt := lnwire.NewMSatFromSatoshis(20000)
	const numBobHtlcs = 3
	var bobPreimage [32]byte
	copy(bobPreimage[:], bytes.Repeat([]byte{0xbb}, 32))
	for i := 0; i < 3; i++ {
		rHash := sha256.Sum256(bobPreimage[:])
		h := &lnwire.UpdateAddHTLC{
			PaymentHash: rHash,
			Amount:      htlcAmt,
			Expiry:      uint32(10),
			OnionBlob:   fakeOnionBlob,
		}

		htlcIndex, err := bobChannel.AddHTLC(h)
		if err != nil {
			t.Fatalf("unable to add bob's htlc: %v", err)
		}

		h.ID = htlcIndex
		if _, err := aliceChannel.ReceiveHTLC(h); err != nil {
			t.Fatalf("unable to recv bob's htlc: %v", err)
		}
	}

	chanID := lnwire.NewChanIDFromOutPoint(
		&aliceChannel.channelState.FundingOutpoint,
	)

	// With the HTLC's applied to both update logs, we'll initiate a state
	// transition from Bob.
	if err := forceStateTransition(bobChannel, aliceChannel); err != nil {
		t.Fatalf("unable to complete bob's state transition: %v", err)
	}

	// Next, Alice's settles all 3 HTLC's from Bob, and also adds a new
	// HTLC of her own.
	for i := 0; i < 3; i++ {
		err := aliceChannel.SettleHTLC(bobPreimage, uint64(i))
		if err != nil {
			t.Fatalf("unable to settle htlc: %v", err)
		}
		err = bobChannel.ReceiveHTLCSettle(bobPreimage, uint64(i))
		if err != nil {
			t.Fatalf("unable to settle htlc: %v", err)
		}
	}
	var alicePreimage [32]byte
	copy(alicePreimage[:], bytes.Repeat([]byte{0xaa}, 32))
	rHash := sha256.Sum256(alicePreimage[:])
	aliceHtlc := &lnwire.UpdateAddHTLC{
		ChanID:      chanID,
		PaymentHash: rHash,
		Amount:      htlcAmt,
		Expiry:      uint32(10),
		OnionBlob:   fakeOnionBlob,
	}
	aliceHtlcIndex, err := aliceChannel.AddHTLC(aliceHtlc)
	if err != nil {
		t.Fatalf("unable to add alice's htlc: %v", err)
	}
	bobHtlcIndex, err := bobChannel.ReceiveHTLC(aliceHtlc)
	if err != nil {
		t.Fatalf("unable to recv alice's htlc: %v", err)
	}

	// Now we'll begin the core of the test itself. Alice will extend a new
	// commitment to Bob, but the connection drops before Bob can process
	// it.
	aliceSig, aliceHtlcSigs, err := aliceChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("unable to sign commitment: %v", err)
	}

	// Bob doesn't get this message so upon reconnection, they need to
	// synchronize. Alice should conclude that she owes Bob a commitment,
	// while Bob should think he's properly synchronized.
	aliceSyncMsg, err := aliceChannel.ChanSyncMsg()
	if err != nil {
		t.Fatalf("unable to produce chan sync msg: %v", err)
	}
	bobSyncMsg, err := bobChannel.ChanSyncMsg()
	if err != nil {
		t.Fatalf("unable to produce chan sync msg: %v", err)
	}

	// This is a helper function that asserts Alice concludes that she
	// needs to retransmit the exact commitment that we failed to send
	// above.
	assertAliceCommitRetransmit := func() {
		aliceMsgsToSend, err := aliceChannel.ProcessChanSyncMsg(
			bobSyncMsg,
		)
		if err != nil {
			t.Fatalf("unable to process chan sync msg: %v", err)
		}
		if len(aliceMsgsToSend) != 5 {
			t.Fatalf("expected alice to send %v messages instead "+
				"will send %v: %v", 5, len(aliceMsgsToSend),
				spew.Sdump(aliceMsgsToSend))
		}

		// Each of the settle messages that Alice sent should match her
		// original intent.
		for i := 0; i < 3; i++ {
			settleMsg, ok := aliceMsgsToSend[i].(*lnwire.UpdateFulfillHTLC)
			if !ok {
				t.Fatalf("expected a htlc settle message, "+
					"instead have %v", spew.Sdump(settleMsg))
			}
			if settleMsg.ID != uint64(i) {
				t.Fatalf("wrong ID in settle msg: expected %v, "+
					"got %v", i, settleMsg.ID)
			}
			if settleMsg.ChanID != chanID {
				t.Fatalf("incorrect chan id: expected %v, got %v",
					chanID, settleMsg.ChanID)
			}
			if settleMsg.PaymentPreimage != bobPreimage {
				t.Fatalf("wrong pre-image: expected %v, got %v",
					alicePreimage, settleMsg.PaymentPreimage)
			}
		}

		// The HTLC add message should be identical.
		if _, ok := aliceMsgsToSend[3].(*lnwire.UpdateAddHTLC); !ok {
			t.Fatalf("expected a htlc add message, instead have %v",
				spew.Sdump(aliceMsgsToSend[3]))
		}
		if !reflect.DeepEqual(aliceHtlc, aliceMsgsToSend[3]) {
			t.Fatalf("htlc msg doesn't match exactly: "+
				"expected %v got %v", spew.Sdump(aliceHtlc),
				spew.Sdump(aliceMsgsToSend[3]))
		}

		// Next, we'll ensure that the CommitSig message exactly
		// matches what Alice originally intended to send.
		commitSigMsg, ok := aliceMsgsToSend[4].(*lnwire.CommitSig)
		if !ok {
			t.Fatalf("expected a CommitSig message, instead have %v",
				spew.Sdump(aliceMsgsToSend[4]))
		}
		if !commitSigMsg.CommitSig.IsEqual(aliceSig) {
			t.Fatalf("commit sig msgs don't match: expected %x got %x",
				aliceSig.Serialize(), commitSigMsg.CommitSig.Serialize())
		}
		if len(commitSigMsg.HtlcSigs) != len(aliceHtlcSigs) {
			t.Fatalf("wrong number of htlc sigs: expected %v, got %v",
				len(aliceHtlcSigs), len(commitSigMsg.HtlcSigs))
		}
		for i, htlcSig := range commitSigMsg.HtlcSigs {
			if !htlcSig.IsEqual(aliceHtlcSigs[i]) {
				t.Fatalf("htlc sig msgs don't match: "+
					"expected %x got %x",
					aliceHtlcSigs[i].Serialize(),
					htlcSig.Serialize())
			}
		}
	}

	// Alice should detect that she needs to re-send 5 messages: the 3
	// settles, her HTLC add, and finally her commit sig message.
	assertAliceCommitRetransmit()

	// From Bob's Pov he has nothing else to send, so he should conclude he
	// has no further action remaining.
	bobMsgsToSend, err := bobChannel.ProcessChanSyncMsg(aliceSyncMsg)
	if err != nil {
		t.Fatalf("unable to process chan sync msg: %v", err)
	}
	if len(bobMsgsToSend) != 0 {
		t.Fatalf("expected bob to send %v messages instead will "+
			"send %v: %v", 5, len(bobMsgsToSend),
			spew.Sdump(bobMsgsToSend))
	}

	// If we restart Alice, she should still conclude that she needs to
	// send the exact same set of messages.
	aliceChannel, err = restartChannel(aliceChannel)
	if err != nil {
		t.Fatalf("unable to restart alice: %v", err)
	}
	defer aliceChannel.Stop()
	assertAliceCommitRetransmit()

	// TODO(roasbeef): restart bob as well???

	// At this point, we should be able to resume the prior state update
	// without any issues, resulting in Alice settling the 3 htlc's, and
	// adding one of her own.
	err = bobChannel.ReceiveNewCommitment(aliceSig, aliceHtlcSigs)
	if err != nil {
		t.Fatalf("bob unable to process alice's commitment: %v", err)
	}
	bobRevocation, _, err := bobChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("unable to revoke bob commitment: %v", err)
	}
	bobSig, bobHtlcSigs, err := bobChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("bob unable to sign commitment: %v", err)
	}
	_, err = aliceChannel.ReceiveRevocation(bobRevocation)
	if err != nil {
		t.Fatalf("alice unable to recv revocation: %v", err)
	}
	err = aliceChannel.ReceiveNewCommitment(bobSig, bobHtlcSigs)
	if err != nil {
		t.Fatalf("alice unable to rev bob's commitment: %v", err)
	}
	aliceRevocation, _, err := aliceChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("alice unable to revoke commitment: %v", err)
	}
	if _, err := bobChannel.ReceiveRevocation(aliceRevocation); err != nil {
		t.Fatalf("bob unable to recv revocation: %v", err)
	}

	// At this point, we'll now assert that their log states are what we
	// expect.
	//
	// Alice's local log counter should be 4 and her HTLC index 3. She
	// should detect Bob's remote log counter as being 3 and his HTLC index
	// 3 as well.
	if aliceChannel.localUpdateLog.logIndex != 4 {
		t.Fatalf("incorrect log index: expected %v, got %v", 4,
			aliceChannel.localUpdateLog.logIndex)
	}
	if aliceChannel.localUpdateLog.htlcCounter != 1 {
		t.Fatalf("incorrect htlc index: expected %v, got %v", 1,
			aliceChannel.localUpdateLog.htlcCounter)
	}
	if aliceChannel.remoteUpdateLog.logIndex != 3 {
		t.Fatalf("incorrect log index: expected %v, got %v", 3,
			aliceChannel.localUpdateLog.logIndex)
	}
	if aliceChannel.remoteUpdateLog.htlcCounter != 3 {
		t.Fatalf("incorrect htlc index: expected %v, got %v", 3,
			aliceChannel.localUpdateLog.htlcCounter)
	}

	// Bob should also have the same state, but mirrored.
	if bobChannel.localUpdateLog.logIndex != 3 {
		t.Fatalf("incorrect log index: expected %v, got %v", 3,
			bobChannel.localUpdateLog.logIndex)
	}
	if bobChannel.localUpdateLog.htlcCounter != 3 {
		t.Fatalf("incorrect htlc index: expected %v, got %v", 3,
			bobChannel.localUpdateLog.htlcCounter)
	}
	if bobChannel.remoteUpdateLog.logIndex != 4 {
		t.Fatalf("incorrect log index: expected %v, got %v", 4,
			bobChannel.localUpdateLog.logIndex)
	}
	if bobChannel.remoteUpdateLog.htlcCounter != 1 {
		t.Fatalf("incorrect htlc index: expected %v, got %v", 1,
			bobChannel.localUpdateLog.htlcCounter)
	}

	// We'll conclude the test by having Bob settle Alice's HTLC, then
	// initiate a state transition.
	err = bobChannel.SettleHTLC(alicePreimage, bobHtlcIndex)
	if err != nil {
		t.Fatalf("unable to settle htlc: %v", err)
	}
	err = aliceChannel.ReceiveHTLCSettle(alicePreimage, aliceHtlcIndex)
	if err != nil {
		t.Fatalf("unable to settle htlc: %v", err)
	}
	if err := forceStateTransition(bobChannel, aliceChannel); err != nil {
		t.Fatalf("unable to complete bob's state transition: %v", err)
	}

	// At this point, the final balances of both parties should properly
	// reflect the amount of HTLC's sent.
	bobMsatSent := numBobHtlcs * htlcAmt
	if aliceChannel.channelState.TotalMSatSent != htlcAmt {
		t.Fatalf("wrong value for msat sent: expected %v, got %v",
			htlcAmt, aliceChannel.channelState.TotalMSatSent)
	}
	if aliceChannel.channelState.TotalMSatReceived != bobMsatSent {
		t.Fatalf("wrong value for msat recv: expected %v, got %v",
			bobMsatSent, aliceChannel.channelState.TotalMSatReceived)
	}
	if bobChannel.channelState.TotalMSatSent != bobMsatSent {
		t.Fatalf("wrong value for msat sent: expected %v, got %v",
			bobMsatSent, bobChannel.channelState.TotalMSatSent)
	}
	if bobChannel.channelState.TotalMSatReceived != htlcAmt {
		t.Fatalf("wrong value for msat recv: expected %v, got %v",
			htlcAmt, bobChannel.channelState.TotalMSatReceived)
	}
}

// TestChanSyncOweRevocation tests that if Bob restarts (and then Alice) before
// he receiver's Alice's RevokeAndAck message, then Alice concludes that she
// needs to re-send the RevokeAndAck. After the revocation has been sent, both
// nodes should be able to successfully complete another state transition.
func TestChanSyncOweRevocation(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	chanID := lnwire.NewChanIDFromOutPoint(
		&aliceChannel.channelState.FundingOutpoint,
	)

	// We'll start the test with Bob extending a single HTLC to Alice, and
	// then initiating a state transition.
	htlcAmt := lnwire.NewMSatFromSatoshis(20000)
	var bobPreimage [32]byte
	copy(bobPreimage[:], bytes.Repeat([]byte{0xaa}, 32))
	rHash := sha256.Sum256(bobPreimage[:])
	bobHtlc := &lnwire.UpdateAddHTLC{
		ChanID:      chanID,
		PaymentHash: rHash,
		Amount:      htlcAmt,
		Expiry:      uint32(10),
	}
	bobHtlcIndex, err := bobChannel.AddHTLC(bobHtlc)
	if err != nil {
		t.Fatalf("unable to add bob's htlc: %v", err)
	}
	aliceHtlcIndex, err := aliceChannel.ReceiveHTLC(bobHtlc)
	if err != nil {
		t.Fatalf("unable to recv bob's htlc: %v", err)
	}
	if err := forceStateTransition(bobChannel, aliceChannel); err != nil {
		t.Fatalf("unable to complete bob's state transition: %v", err)
	}

	// Next, Alice will settle that single HTLC, the _begin_ the start of a
	// state transition.
	err = aliceChannel.SettleHTLC(bobPreimage, aliceHtlcIndex)
	if err != nil {
		t.Fatalf("unable to settle htlc: %v", err)
	}
	err = bobChannel.ReceiveHTLCSettle(bobPreimage, bobHtlcIndex)
	if err != nil {
		t.Fatalf("unable to settle htlc: %v", err)
	}

	// We'll model the state transition right up until Alice needs to send
	// her revocation message to complete the state transition.
	//
	// Alice signs the next state, then Bob receives and sends his
	// revocation message.
	aliceSig, aliceHtlcSigs, err := aliceChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("unable to sign commitment: %v", err)
	}
	err = bobChannel.ReceiveNewCommitment(aliceSig, aliceHtlcSigs)
	if err != nil {
		t.Fatalf("bob unable to process alice's commitment: %v", err)
	}

	bobRevocation, _, err := bobChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("unable to revoke bob commitment: %v", err)
	}
	bobSig, bobHtlcSigs, err := bobChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("bob unable to sign commitment: %v", err)
	}

	_, err = aliceChannel.ReceiveRevocation(bobRevocation)
	if err != nil {
		t.Fatalf("alice unable to recv revocation: %v", err)
	}
	err = aliceChannel.ReceiveNewCommitment(bobSig, bobHtlcSigs)
	if err != nil {
		t.Fatalf("alice unable to rev bob's commitment: %v", err)
	}

	// At this point, we'll simulate the connection breaking down by Bob's
	// lack of knowledge of the revocation message that Alice just sent.
	aliceRevocation, _, err := aliceChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("alice unable to revoke commitment: %v", err)
	}

	// If we fetch the channel sync messages at this state, then Alice
	// should report that she owes Bob a revocation message, while Bob
	// thinks they're fully in sync.
	aliceSyncMsg, err := aliceChannel.ChanSyncMsg()
	if err != nil {
		t.Fatalf("unable to produce chan sync msg: %v", err)
	}
	bobSyncMsg, err := bobChannel.ChanSyncMsg()
	if err != nil {
		t.Fatalf("unable to produce chan sync msg: %v", err)
	}

	assertAliceOwesRevoke := func() {
		aliceMsgsToSend, err := aliceChannel.ProcessChanSyncMsg(bobSyncMsg)
		if err != nil {
			t.Fatalf("unable to process chan sync msg: %v", err)
		}
		if len(aliceMsgsToSend) != 1 {
			t.Fatalf("expected single message retransmission from Alice, "+
				"instead got %v", spew.Sdump(aliceMsgsToSend))
		}
		aliceReRevoke, ok := aliceMsgsToSend[0].(*lnwire.RevokeAndAck)
		if !ok {
			t.Fatalf("expected to retransmit revocation msg, instead "+
				"have: %v", spew.Sdump(aliceMsgsToSend[0]))
		}

		// Alice should re-send the revocation message for her prior
		// state.
		expectedRevocation, err := aliceChannel.generateRevocation(
			aliceChannel.currentHeight - 1,
		)
		if err != nil {
			t.Fatalf("unable to regenerate revocation: %v", err)
		}
		if !reflect.DeepEqual(expectedRevocation, aliceReRevoke) {
			t.Fatalf("wrong re-revocation: expected %v, got %v",
				expectedRevocation, aliceReRevoke)
		}
	}

	// From Bob's PoV he shouldn't think that he owes Alice any messages.
	bobMsgsToSend, err := bobChannel.ProcessChanSyncMsg(aliceSyncMsg)
	if err != nil {
		t.Fatalf("unable to process chan sync msg: %v", err)
	}
	if len(bobMsgsToSend) != 0 {
		t.Fatalf("expected bob to not retransmit, instead has: %v",
			spew.Sdump(bobMsgsToSend))
	}

	// Alice should detect that she owes Bob a revocation message, and only
	// that single message.
	assertAliceOwesRevoke()

	// If we restart Alice, then she should still decide that she owes a
	// revocation message to Bob.
	aliceChannel, err = restartChannel(aliceChannel)
	if err != nil {
		t.Fatalf("unable to restart alice: %v", err)
	}
	defer aliceChannel.Stop()
	assertAliceOwesRevoke()

	// TODO(roasbeef): restart bob too???

	// We'll continue by then allowing bob to process Alice's revocation message.
	if _, err := bobChannel.ReceiveRevocation(aliceRevocation); err != nil {
		t.Fatalf("bob unable to recv revocation: %v", err)
	}

	// Finally, Alice will add an HTLC over her own such that we assert the
	// channel can continue to receive updates.
	var alicePreimage [32]byte
	copy(bobPreimage[:], bytes.Repeat([]byte{0xaa}, 32))
	rHash = sha256.Sum256(alicePreimage[:])
	aliceHtlc := &lnwire.UpdateAddHTLC{
		ChanID:      chanID,
		PaymentHash: rHash,
		Amount:      htlcAmt,
		Expiry:      uint32(10),
	}
	if _, err := aliceChannel.AddHTLC(aliceHtlc); err != nil {
		t.Fatalf("unable to add alice's htlc: %v", err)
	}
	if _, err := bobChannel.ReceiveHTLC(aliceHtlc); err != nil {
		t.Fatalf("unable to recv alice's htlc: %v", err)
	}
	if err := forceStateTransition(aliceChannel, bobChannel); err != nil {
		t.Fatalf("unable to complete alice's state transition: %v", err)
	}

	// At this point, both sides should detect that they're fully synced.
	assertNoChanSyncNeeded(t, aliceChannel, bobChannel)
}

// TestChanSyncOweRevocationAndCommit tests that if Alice initiates a state
// transition with Bob and Bob sends both a RevokeAndAck and CommitSig message
// but Alice doesn't receive them before the connection dies, then he'll
// retransmit them both.
func TestChanSyncOweRevocationAndCommit(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	htlcAmt := lnwire.NewMSatFromSatoshis(20000)

	// We'll kick off the test by having Bob send Alice an HTLC, then lock
	// it in with a state transition.
	var bobPreimage [32]byte
	copy(bobPreimage[:], bytes.Repeat([]byte{0xaa}, 32))
	rHash := sha256.Sum256(bobPreimage[:])
	bobHtlc := &lnwire.UpdateAddHTLC{
		PaymentHash: rHash,
		Amount:      htlcAmt,
		Expiry:      uint32(10),
	}
	bobHtlcIndex, err := bobChannel.AddHTLC(bobHtlc)
	if err != nil {
		t.Fatalf("unable to add bob's htlc: %v", err)
	}
	aliceHtlcIndex, err := aliceChannel.ReceiveHTLC(bobHtlc)
	if err != nil {
		t.Fatalf("unable to recv bob's htlc: %v", err)
	}
	if err := forceStateTransition(bobChannel, aliceChannel); err != nil {
		t.Fatalf("unable to complete bob's state transition: %v", err)
	}

	// Next, Alice will settle that incoming HTLC, then we'll start the
	// core of the test itself.
	err = aliceChannel.SettleHTLC(bobPreimage, aliceHtlcIndex)
	if err != nil {
		t.Fatalf("unable to settle htlc: %v", err)
	}
	err = bobChannel.ReceiveHTLCSettle(bobPreimage, bobHtlcIndex)
	if err != nil {
		t.Fatalf("unable to settle htlc: %v", err)
	}

	// Progressing the exchange: Alice will send her signature, Bob will
	// receive, send a revocation and also a signature for Alice's state.
	aliceSig, aliceHtlcSigs, err := aliceChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("unable to sign commitment: %v", err)
	}
	err = bobChannel.ReceiveNewCommitment(aliceSig, aliceHtlcSigs)
	if err != nil {
		t.Fatalf("bob unable to process alice's commitment: %v", err)
	}

	// Bob generates the revoke and sig message, but the messages don't
	// reach Alice before the connection dies.
	bobRevocation, _, err := bobChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("unable to revoke bob commitment: %v", err)
	}
	bobSig, bobHtlcSigs, err := bobChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("bob unable to sign commitment: %v", err)
	}

	// If we now attempt to resync, then Alice should conclude that she
	// doesn't need any further updates, while Bob concludes that he needs
	// to re-send both his revocation and commit sig message.
	aliceSyncMsg, err := aliceChannel.ChanSyncMsg()
	if err != nil {
		t.Fatalf("unable to produce chan sync msg: %v", err)
	}
	bobSyncMsg, err := bobChannel.ChanSyncMsg()
	if err != nil {
		t.Fatalf("unable to produce chan sync msg: %v", err)
	}

	aliceMsgsToSend, err := aliceChannel.ProcessChanSyncMsg(bobSyncMsg)
	if err != nil {
		t.Fatalf("unable to process chan sync msg: %v", err)
	}
	if len(aliceMsgsToSend) != 0 {
		t.Fatalf("expected alice to not retransmit, instead she's "+
			"sending: %v", spew.Sdump(aliceMsgsToSend))
	}

	assertBobSendsRevokeAndCommit := func() {
		bobMsgsToSend, err := bobChannel.ProcessChanSyncMsg(aliceSyncMsg)
		if err != nil {
			t.Fatalf("unable to process chan sync msg: %v", err)
		}
		if len(bobMsgsToSend) != 2 {
			t.Fatalf("expected bob to send %v messages, instead "+
				"sends: %v", 2, spew.Sdump(bobMsgsToSend))
		}
		bobReRevoke, ok := bobMsgsToSend[0].(*lnwire.RevokeAndAck)
		if !ok {
			t.Fatalf("expected bob to re-send revoke, instead sending: %v",
				spew.Sdump(bobMsgsToSend[0]))
		}
		if !reflect.DeepEqual(bobReRevoke, bobRevocation) {
			t.Fatalf("revocation msgs don't match: expected %v, got %v",
				bobRevocation, bobReRevoke)
		}

		bobReCommitSigMsg, ok := bobMsgsToSend[1].(*lnwire.CommitSig)
		if !ok {
			t.Fatalf("expected bob to re-send commit sig, instead sending: %v",
				spew.Sdump(bobMsgsToSend[1]))
		}
		if !bobReCommitSigMsg.CommitSig.IsEqual(bobSig) {
			t.Fatalf("commit sig msgs don't match: expected %x got %x",
				bobSig.Serialize(), bobReCommitSigMsg.CommitSig.Serialize())
		}
		if len(bobReCommitSigMsg.HtlcSigs) != len(bobHtlcSigs) {
			t.Fatalf("wrong number of htlc sigs: expected %v, got %v",
				len(bobHtlcSigs), len(bobReCommitSigMsg.HtlcSigs))
		}
		for i, htlcSig := range bobReCommitSigMsg.HtlcSigs {
			if !htlcSig.IsEqual(aliceHtlcSigs[i]) {
				t.Fatalf("htlc sig msgs don't match: "+
					"expected %x got %x",
					bobHtlcSigs[i].Serialize(),
					htlcSig.Serialize())
			}
		}
	}

	// We expect Bob to send exactly two messages: first his revocation
	// message to Alice, and second his original commit sig message.
	assertBobSendsRevokeAndCommit()

	// At this point we simulate the connection failing with a restart from
	// Bob. He should still re-send the exact same set of messages.
	bobChannel, err = restartChannel(bobChannel)
	if err != nil {
		t.Fatalf("unable to restart channel: %v", err)
	}
	defer bobChannel.Stop()
	assertBobSendsRevokeAndCommit()

	// We'll now finish the state transition by having Alice process both
	// messages, and send her final revocation.
	_, err = aliceChannel.ReceiveRevocation(bobRevocation)
	if err != nil {
		t.Fatalf("alice unable to recv revocation: %v", err)
	}
	err = aliceChannel.ReceiveNewCommitment(bobSig, bobHtlcSigs)
	if err != nil {
		t.Fatalf("alice unable to rev bob's commitment: %v", err)
	}
	aliceRevocation, _, err := aliceChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("alice unable to revoke commitment: %v", err)
	}
	if _, err := bobChannel.ReceiveRevocation(aliceRevocation); err != nil {
		t.Fatalf("bob unable to recv revocation: %v", err)
	}
}

// TestChanSyncOweRevocationAndCommitForceTransition tests that if Alice
// initiates a state transition with Bob, but Alice fails to receive his
// RevokeAndAck and the connection dies before Bob sends his CommitSig message,
// then Bob will re-send her RevokeAndAck message. Bob will also send and
// _identical_ CommitSig as he detects his commitment chain is ahead of
// Alice's.
func TestChanSyncOweRevocationAndCommitForceTransition(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	htlcAmt := lnwire.NewMSatFromSatoshis(20000)

	// We'll kick off the test by having Bob send Alice an HTLC, then lock
	// it in with a state transition.
	var bobPreimage [32]byte
	copy(bobPreimage[:], bytes.Repeat([]byte{0xaa}, 32))
	rHash := sha256.Sum256(bobPreimage[:])
	bobHtlc := &lnwire.UpdateAddHTLC{
		PaymentHash: rHash,
		Amount:      htlcAmt,
		Expiry:      uint32(10),
	}
	bobHtlcIndex, err := bobChannel.AddHTLC(bobHtlc)
	if err != nil {
		t.Fatalf("unable to add bob's htlc: %v", err)
	}
	aliceHtlcIndex, err := aliceChannel.ReceiveHTLC(bobHtlc)
	if err != nil {
		t.Fatalf("unable to recv bob's htlc: %v", err)
	}
	if err := forceStateTransition(bobChannel, aliceChannel); err != nil {
		t.Fatalf("unable to complete bob's state transition: %v", err)
	}

	// Next, Alice will settle that incoming HTLC, then we'll start the
	// core of the test itself.
	err = aliceChannel.SettleHTLC(bobPreimage, aliceHtlcIndex)
	if err != nil {
		t.Fatalf("unable to settle htlc: %v", err)
	}
	err = bobChannel.ReceiveHTLCSettle(bobPreimage, bobHtlcIndex)
	if err != nil {
		t.Fatalf("unable to settle htlc: %v", err)
	}

	// Progressing the exchange: Alice will send her signature, with Bob
	// processing the new state locally.
	aliceSig, aliceHtlcSigs, err := aliceChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("unable to sign commitment: %v", err)
	}
	err = bobChannel.ReceiveNewCommitment(aliceSig, aliceHtlcSigs)
	if err != nil {
		t.Fatalf("bob unable to process alice's commitment: %v", err)
	}

	// Bob then sends his revocation message, but before Alice can process
	// it (and before he scan send his CommitSig message), then connection
	// dies.
	bobRevocation, _, err := bobChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("unable to revoke bob commitment: %v", err)
	}

	// Now if we attempt to synchronize states at this point, Alice should
	// detect that she owes nothing, while Bob should re-send both his
	// RevokeAndAck as well as his commitment message.
	aliceSyncMsg, err := aliceChannel.ChanSyncMsg()
	if err != nil {
		t.Fatalf("unable to produce chan sync msg: %v", err)
	}
	bobSyncMsg, err := bobChannel.ChanSyncMsg()
	if err != nil {
		t.Fatalf("unable to produce chan sync msg: %v", err)
	}

	aliceMsgsToSend, err := aliceChannel.ProcessChanSyncMsg(bobSyncMsg)
	if err != nil {
		t.Fatalf("unable to process chan sync msg: %v", err)
	}
	if len(aliceMsgsToSend) != 0 {
		t.Fatalf("expected alice to not retransmit, instead she's "+
			"sending: %v", spew.Sdump(aliceMsgsToSend))
	}

	// If we process Alice's sync message from Bob's PoV, then he should
	// send his RevokeAndAck message again. Additionally, the CommitSig
	// message that he sends should be sufficient to finalize the state
	// transition.
	bobMsgsToSend, err := bobChannel.ProcessChanSyncMsg(aliceSyncMsg)
	if err != nil {
		t.Fatalf("unable to process chan sync msg: %v", err)
	}
	if len(bobMsgsToSend) != 2 {
		t.Fatalf("expected bob to send %v messages, instead "+
			"sends: %v", 2, spew.Sdump(bobMsgsToSend))
	}
	bobReRevoke, ok := bobMsgsToSend[0].(*lnwire.RevokeAndAck)
	if !ok {
		t.Fatalf("expected bob to re-send revoke, instead sending: %v",
			spew.Sdump(bobMsgsToSend[0]))
	}
	if !reflect.DeepEqual(bobReRevoke, bobRevocation) {
		t.Fatalf("revocation msgs don't match: expected %v, got %v",
			bobRevocation, bobReRevoke)
	}

	// The second message should be his CommitSig message that he never
	// sent, but will send in order to force both states to synchronize.
	bobReCommitSigMsg, ok := bobMsgsToSend[1].(*lnwire.CommitSig)
	if !ok {
		t.Fatalf("expected bob to re-send commit sig, instead sending: %v",
			spew.Sdump(bobMsgsToSend[1]))
	}

	// At this point we simulate the connection failing with a restart from
	// Bob. He should still re-send the exact same set of messages.
	bobChannel, err = restartChannel(bobChannel)
	if err != nil {
		t.Fatalf("unable to restart channel: %v", err)
	}
	defer bobChannel.Stop()
	if len(bobMsgsToSend) != 2 {
		t.Fatalf("expected bob to send %v messages, instead "+
			"sends: %v", 2, spew.Sdump(bobMsgsToSend))
	}
	bobReRevoke, ok = bobMsgsToSend[0].(*lnwire.RevokeAndAck)
	if !ok {
		t.Fatalf("expected bob to re-send revoke, instead sending: %v",
			spew.Sdump(bobMsgsToSend[0]))
	}
	bobSigMsg, ok := bobMsgsToSend[1].(*lnwire.CommitSig)
	if !ok {
		t.Fatalf("expected bob to re-send commit sig, instead sending: %v",
			spew.Sdump(bobMsgsToSend[1]))
	}
	if !reflect.DeepEqual(bobReRevoke, bobRevocation) {
		t.Fatalf("revocation msgs don't match: expected %v, got %v",
			bobRevocation, bobReRevoke)
	}
	if !bobReCommitSigMsg.CommitSig.IsEqual(bobSigMsg.CommitSig) {
		t.Fatalf("commit sig msgs don't match: expected %x got %x",
			bobSigMsg.CommitSig.Serialize(),
			bobReCommitSigMsg.CommitSig.Serialize())
	}
	if len(bobReCommitSigMsg.HtlcSigs) != len(bobSigMsg.HtlcSigs) {
		t.Fatalf("wrong number of htlc sigs: expected %v, got %v",
			len(bobSigMsg.HtlcSigs), len(bobReCommitSigMsg.HtlcSigs))
	}
	for i, htlcSig := range bobReCommitSigMsg.HtlcSigs {
		if htlcSig.IsEqual(bobSigMsg.HtlcSigs[i]) {
			t.Fatalf("htlc sig msgs don't match: "+
				"expected %x got %x",
				bobSigMsg.HtlcSigs[i].Serialize(),
				htlcSig.Serialize())
		}
	}

	// Now, we'll continue the exchange, sending Bob's revocation and
	// signature message to Alice, ending with Alice sending her revocation
	// message to Bob.
	_, err = aliceChannel.ReceiveRevocation(bobRevocation)
	if err != nil {
		t.Fatalf("alice unable to recv revocation: %v", err)
	}
	err = aliceChannel.ReceiveNewCommitment(
		bobSigMsg.CommitSig, bobSigMsg.HtlcSigs,
	)
	if err != nil {
		t.Fatalf("alice unable to rev bob's commitment: %v", err)
	}
	aliceRevocation, _, err := aliceChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("alice unable to revoke commitment: %v", err)
	}
	if _, err := bobChannel.ReceiveRevocation(aliceRevocation); err != nil {
		t.Fatalf("bob unable to recv revocation: %v", err)
	}
}

// TestFeeUpdateRejectInsaneFee tests that if the initiator tries to attach a
// fee that would put them below their current reserve, then it's rejected by
// the state machine.
func TestFeeUpdateRejectInsaneFee(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, _, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	// Next, we'll try to add a fee rate to Alice which is 1,000,000x her
	// starting fee rate.
	startingFeeRate := aliceChannel.channelState.LocalCommitment.FeePerKw
	newFeeRate := startingFeeRate * 1000000

	// Both Alice and Bob should reject this new fee rate as it it far too
	// large.
	if err := aliceChannel.UpdateFee(newFeeRate); err == nil {
		t.Fatalf("alice should have rejected fee update")
	}
}

// TestChannelRetransmissionFeeUpdate tests that the initiator will include any
// pending fee updates if it needs to retransmit signatures.
func TestChannelRetransmissionFeeUpdate(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	// First, we'll fetch the current fee rate present within the
	// commitment transactions.
	startingFeeRate := aliceChannel.channelState.LocalCommitment.FeePerKw

	// Next, we'll start a commitment update, with Alice sending a new
	// update to double the fee rate of the commitment.
	newFeeRate := startingFeeRate * 2
	if err := aliceChannel.UpdateFee(newFeeRate); err != nil {
		t.Fatalf("unable to update fee for Alice's channel: %v", err)
	}
	if err := bobChannel.ReceiveUpdateFee(newFeeRate); err != nil {
		t.Fatalf("unable to update fee for Bob's channel: %v", err)
	}

	// Now, Alice will send a new commitment to Bob, but we'll simulate a
	// connection failure, so Bob doesn't get her signature.
	aliceSig, aliceHtlcSigs, err := aliceChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("unable to sign commitment: %v", err)
	}

	// Restart both channels to simulate a connection restart.
	aliceChannel, err = restartChannel(aliceChannel)
	if err != nil {
		t.Fatalf("unable to restart alice: %v", err)
	}
	defer aliceChannel.Stop()
	bobChannel, err = restartChannel(bobChannel)
	if err != nil {
		t.Fatalf("unable to restart channel: %v", err)
	}
	defer bobChannel.Stop()

	// Bob doesn't get this message so upon reconnection, they need to
	// synchronize. Alice should conclude that she owes Bob a commitment,
	// while Bob should think he's properly synchronized.
	aliceSyncMsg, err := aliceChannel.ChanSyncMsg()
	if err != nil {
		t.Fatalf("unable to produce chan sync msg: %v", err)
	}
	bobSyncMsg, err := bobChannel.ChanSyncMsg()
	if err != nil {
		t.Fatalf("unable to produce chan sync msg: %v", err)
	}

	// Bob should detect that he doesn't need to send anything to Alice.
	bobMsgsToSend, err := bobChannel.ProcessChanSyncMsg(aliceSyncMsg)
	if err != nil {
		t.Fatalf("unable to process chan sync msg: %v", err)
	}
	if len(bobMsgsToSend) != 0 {
		t.Fatalf("expected bob to send %v messages instead "+
			"will send %v: %v", 0, len(bobMsgsToSend),
			spew.Sdump(bobMsgsToSend))
	}

	// When Alice processes Bob's chan sync message, she should realize
	// that she needs to first send a new UpdateFee message, and also a
	// CommitSig.
	aliceMsgsToSend, err := aliceChannel.ProcessChanSyncMsg(
		bobSyncMsg,
	)
	if err != nil {
		t.Fatalf("unable to process chan sync msg: %v", err)
	}
	if len(aliceMsgsToSend) != 2 {
		t.Fatalf("expected alice to send %v messages instead "+
			"will send %v: %v", 2, len(aliceMsgsToSend),
			spew.Sdump(aliceMsgsToSend))
	}

	// The first message should be an UpdateFee message.
	retransFeeMsg, ok := aliceMsgsToSend[0].(*lnwire.UpdateFee)
	if !ok {
		t.Fatalf("expected UpdateFee message, instead have: %v",
			spew.Sdump(aliceMsgsToSend[0]))
	}

	// The fee should match exactly the new fee update we applied above.
	if retransFeeMsg.FeePerKw != uint32(newFeeRate) {
		t.Fatalf("fee update doesn't match: expected %v, got %v",
			uint32(newFeeRate), retransFeeMsg)
	}

	// The second, should be a CommitSig message, and be identical to the
	// sig message she sent prior.
	commitSigMsg, ok := aliceMsgsToSend[1].(*lnwire.CommitSig)
	if !ok {
		t.Fatalf("expected a CommitSig message, instead have %v",
			spew.Sdump(aliceMsgsToSend[1]))
	}
	if !commitSigMsg.CommitSig.IsEqual(aliceSig) {
		t.Fatalf("commit sig msgs don't match: expected %x got %x",
			aliceSig.Serialize(), commitSigMsg.CommitSig.Serialize())
	}
	if len(commitSigMsg.HtlcSigs) != len(aliceHtlcSigs) {
		t.Fatalf("wrong number of htlc sigs: expected %v, got %v",
			len(aliceHtlcSigs), len(commitSigMsg.HtlcSigs))
	}
	for i, htlcSig := range commitSigMsg.HtlcSigs {
		if !htlcSig.IsEqual(aliceHtlcSigs[i]) {
			t.Fatalf("htlc sig msgs don't match: "+
				"expected %x got %x",
				aliceHtlcSigs[i].Serialize(),
				htlcSig.Serialize())
		}
	}

	// Now, we if re-apply the updates to Bob, we should be able to resume
	// the commitment update as normal.
	if err := bobChannel.ReceiveUpdateFee(newFeeRate); err != nil {
		t.Fatalf("unable to update fee for Bob's channel: %v", err)
	}

	err = bobChannel.ReceiveNewCommitment(aliceSig, aliceHtlcSigs)
	if err != nil {
		t.Fatalf("bob unable to process alice's commitment: %v", err)
	}
	bobRevocation, _, err := bobChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("unable to revoke bob commitment: %v", err)
	}
	bobSig, bobHtlcSigs, err := bobChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("bob unable to sign commitment: %v", err)
	}
	_, err = aliceChannel.ReceiveRevocation(bobRevocation)
	if err != nil {
		t.Fatalf("alice unable to recv revocation: %v", err)
	}
	err = aliceChannel.ReceiveNewCommitment(bobSig, bobHtlcSigs)
	if err != nil {
		t.Fatalf("alice unable to rev bob's commitment: %v", err)
	}
	aliceRevocation, _, err := aliceChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatalf("alice unable to revoke commitment: %v", err)
	}
	if _, err := bobChannel.ReceiveRevocation(aliceRevocation); err != nil {
		t.Fatalf("bob unable to recv revocation: %v", err)
	}

	// Both parties should now have the latest fee rate locked-in.
	if aliceChannel.channelState.LocalCommitment.FeePerKw != newFeeRate {
		t.Fatalf("alice's feePerKw was not locked in")
	}
	if bobChannel.channelState.LocalCommitment.FeePerKw != newFeeRate {
		t.Fatalf("bob's feePerKw was not locked in")
	}

	// Finally, we'll add with adding a new HTLC, then forcing a state
	// transition. This should also proceed as normal.
	var bobPreimage [32]byte
	copy(bobPreimage[:], bytes.Repeat([]byte{0xaa}, 32))
	rHash := sha256.Sum256(bobPreimage[:])
	bobHtlc := &lnwire.UpdateAddHTLC{
		PaymentHash: rHash,
		Amount:      lnwire.NewMSatFromSatoshis(20000),
		Expiry:      uint32(10),
	}
	if _, err := bobChannel.AddHTLC(bobHtlc); err != nil {
		t.Fatalf("unable to add bob's htlc: %v", err)
	}
	if _, err := aliceChannel.ReceiveHTLC(bobHtlc); err != nil {
		t.Fatalf("unable to recv bob's htlc: %v", err)
	}
	if err := forceStateTransition(bobChannel, aliceChannel); err != nil {
		t.Fatalf("unable to complete bob's state transition: %v", err)
	}
}

// TestChanSyncUnableToSync tests that if Alice or Bob receive an invalid
// ChannelReestablish messages,then they reject the message and declare the
// channel un-continuable by returning ErrCannotSyncCommitChains.
func TestChanSyncUnableToSync(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	// If we immediately send both sides a "bogus" ChanSync message, then
	// they both should conclude that they're unable to synchronize the
	// state.
	badChanSync := &lnwire.ChannelReestablish{
		ChanID: lnwire.NewChanIDFromOutPoint(
			&aliceChannel.channelState.FundingOutpoint,
		),
		NextLocalCommitHeight:  1000,
		RemoteCommitTailHeight: 9000,
	}
	_, err = bobChannel.ProcessChanSyncMsg(badChanSync)
	if err != ErrCannotSyncCommitChains {
		t.Fatalf("expected error instead have: %v", err)
	}
	_, err = aliceChannel.ProcessChanSyncMsg(badChanSync)
	if err != ErrCannotSyncCommitChains {
		t.Fatalf("expected error instead have: %v", err)
	}
}

// TestChanSyncInvalidLastSecret ensures that if Alice and Bob have completed
// state transitions in an existing channel, and then send a ChannelReestablish
// message after a restart, the following holds: if Alice has lost data, so she
// sends an invalid commit secret then both parties recognize this as possible
// data loss.
func TestChanSyncInvalidLastSecret(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	// We'll create a new instances of Alice before doing any state updates
	// such that we have the initial in memory state at the start of the
	// channel.
	aliceOld, err := restartChannel(aliceChannel)
	if err != nil {
		t.Fatalf("unable to restart alice")
	}

	// First, we'll add an HTLC, and then initiate a state transition
	// between the two parties such that we actually have a prior
	// revocation to send.
	var paymentPreimage [32]byte
	copy(paymentPreimage[:], bytes.Repeat([]byte{1}, 32))
	paymentHash := sha256.Sum256(paymentPreimage[:])
	htlcAmt := lnwire.NewMSatFromSatoshis(btcutil.SatoshiPerBitcoin)
	htlc := &lnwire.UpdateAddHTLC{
		PaymentHash: paymentHash,
		Amount:      htlcAmt,
		Expiry:      uint32(5),
	}
	if _, err := aliceChannel.AddHTLC(htlc); err != nil {
		t.Fatalf("unable to add htlc: %v", err)
	}
	if _, err := bobChannel.ReceiveHTLC(htlc); err != nil {
		t.Fatalf("unable to recv htlc: %v", err)
	}

	// Then we'll initiate a state transition to lock in this new HTLC.
	if err := forceStateTransition(aliceChannel, bobChannel); err != nil {
		t.Fatalf("unable to complete alice's state transition: %v", err)
	}

	// Next, we'll restart both parties in order to simulate a connection
	// re-establishment.
	aliceChannel, err = restartChannel(aliceChannel)
	if err != nil {
		t.Fatalf("unable to restart alice: %v", err)
	}
	bobChannel, err = restartChannel(bobChannel)
	if err != nil {
		t.Fatalf("unable to restart bob: %v", err)
	}

	// Next, we'll produce the ChanSync messages for both parties.
	aliceChanSync, err := aliceChannel.ChanSyncMsg()
	if err != nil {
		t.Fatalf("unable to generate chan sync msg: %v", err)
	}
	bobChanSync, err := bobChannel.ChanSyncMsg()
	if err != nil {
		t.Fatalf("unable to generate chan sync msg: %v", err)
	}

	// We'll modify Alice's sync message to have an invalid commitment
	// secret.
	aliceChanSync.LastRemoteCommitSecret[4] ^= 0x01

	// Alice's former self should conclude that she possibly lost data as
	// Bob is sending a valid commit secret for the latest state.
	_, err = aliceOld.ProcessChanSyncMsg(bobChanSync)
	if err != ErrCommitSyncDataLoss {
		t.Fatalf("wrong error, expected ErrCommitSyncDataLoss "+
			"instead got: %v", err)
	}

	// Bob should conclude that he should force close the channel, as Alice
	// cannot continue operation.
	_, err = bobChannel.ProcessChanSyncMsg(aliceChanSync)
	if err != ErrInvalidLastCommitSecret {
		t.Fatalf("wrong error, expected ErrInvalidLastCommitSecret, "+
			"instead got: %v", err)
	}
}

// TestChanAvailableBandwidth tests the accuracy of the AvailableBalance()
// method. The value returned from this message should reflect the value
// returned within the commitment state of a channel after the transition is
// initiated.
func TestChanAvailableBandwidth(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	assertBandwidthEstimateCorrect := func(aliceInitiate bool) {
		// With the HTLC's added, we'll now query the AvailableBalance
		// method for the current available channel bandwidth from
		// Alice's PoV.
		aliceAvailableBalance := aliceChannel.AvailableBalance()

		// With this balance obtained, we'll now trigger a state update
		// to actually determine what the current up to date balance
		// is.
		if aliceInitiate {
			err := forceStateTransition(aliceChannel, bobChannel)
			if err != nil {
				t.Fatalf("unable to complete alice's state "+
					"transition: %v", err)
			}
		} else {
			err := forceStateTransition(bobChannel, aliceChannel)
			if err != nil {
				t.Fatalf("unable to complete alice's state "+
					"transition: %v", err)
			}
		}

		// Now, we'll obtain the current available bandwidth in Alice's
		// latest commitment and compare that to the prior estimate.
		aliceBalance := aliceChannel.channelState.LocalCommitment.LocalBalance
		if aliceBalance != aliceAvailableBalance {
			_, _, line, _ := runtime.Caller(1)
			t.Fatalf("line: %v, incorrect balance: expected %v, "+
				"got %v", line, aliceBalance,
				aliceAvailableBalance)
		}
	}

	// First, we'll add 3 outgoing HTLC's from Alice to Bob.
	const numHtlcs = 3
	var htlcAmt lnwire.MilliSatoshi = 100000
	alicePreimages := make([][32]byte, numHtlcs)
	for i := 0; i < numHtlcs; i++ {
		htlc, preImage := createHTLC(i, htlcAmt)
		if _, err := aliceChannel.AddHTLC(htlc); err != nil {
			t.Fatalf("unable to add htlc: %v", err)
		}
		if _, err := bobChannel.ReceiveHTLC(htlc); err != nil {
			t.Fatalf("unable to recv htlc: %v", err)
		}

		alicePreimages[i] = preImage
	}

	assertBandwidthEstimateCorrect(true)

	// We'll repeat the same exercise, but with non-dust HTLCs. So we'll
	// crank up the value of the HTLC's we're adding to the commitment
	// transaction.
	htlcAmt = lnwire.NewMSatFromSatoshis(30000)
	for i := 0; i < numHtlcs; i++ {
		htlc, preImage := createHTLC(numHtlcs+i, htlcAmt)
		if _, err := aliceChannel.AddHTLC(htlc); err != nil {
			t.Fatalf("unable to add htlc: %v", err)
		}
		if _, err := bobChannel.ReceiveHTLC(htlc); err != nil {
			t.Fatalf("unable to recv htlc: %v", err)
		}

		alicePreimages = append(alicePreimages, preImage)
	}

	assertBandwidthEstimateCorrect(true)

	// Next, we'll have Bob 5 of Alice's HTLC's, and cancel one of them (in
	// the update log).
	for i := 0; i < (numHtlcs*2)-1; i++ {
		preImage := alicePreimages[i]
		err := bobChannel.SettleHTLC(preImage, uint64(i))
		if err != nil {
			t.Fatalf("unable to settle htlc: %v", err)
		}
		err = aliceChannel.ReceiveHTLCSettle(preImage, uint64(i))
		if err != nil {
			t.Fatalf("unable to settle htlc: %v", err)
		}
	}

	htlcIndex := uint64((numHtlcs * 2) - 1)
	err = bobChannel.FailHTLC(htlcIndex, []byte("f"))
	if err != nil {
		t.Fatalf("unable to cancel HTLC: %v", err)
	}
	err = aliceChannel.ReceiveFailHTLC(htlcIndex, []byte("bad"))
	if err != nil {
		t.Fatalf("unable to recv htlc cancel: %v", err)
	}

	// We must do a state transition before the balance is available
	// for Alice.
	if err := forceStateTransition(aliceChannel, bobChannel); err != nil {
		t.Fatalf("unable to complete alice's state "+
			"transition: %v", err)
	}

	// With the HTLC's settled in the log, we'll now assert that if we
	// initiate a state transition, then our guess was correct.
	assertBandwidthEstimateCorrect(false)

	// TODO(roasbeef): additional tests from diff starting conditions
}

// TestSignCommitmentFailNotLockedIn tests that a channel will not attempt to
// create a new state if it doesn't yet know of the next revocation point for
// the remote party.
func TestSignCommitmentFailNotLockedIn(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, _, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	// Next, we'll modify Alice's internal state to omit knowledge of Bob's
	// next revocation point.
	aliceChannel.channelState.RemoteNextRevocation = nil

	// If we now try to initiate a state update, then it should fail as
	// Alice is unable to actually create a new state.
	_, _, err = aliceChannel.SignNextCommitment()
	if err != ErrNoWindow {
		t.Fatalf("expected ErrNoWindow, instead have: %v", err)
	}
}

// TestLockedInHtlcForwardingSkipAfterRestart ensures that after a restart, a
// state machine doesn't attempt to re-forward any HTLC's that were already
// locked in, but in a prior state.
func TestLockedInHtlcForwardingSkipAfterRestart(t *testing.T) {
	t.Parallel()

	// First, we'll make a channel between Alice and Bob.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	// We'll now add two HTLC's from Bob to Alice, then Bob will initiate a
	// state transition.
	var htlcAmt lnwire.MilliSatoshi = 100000
	htlc, _ := createHTLC(0, htlcAmt)
	if _, err := aliceChannel.AddHTLC(htlc); err != nil {
		t.Fatalf("unable to add htlc: %v", err)
	}
	if _, err := bobChannel.ReceiveHTLC(htlc); err != nil {
		t.Fatalf("unable to recv htlc: %v", err)
	}
	htlc2, _ := createHTLC(1, htlcAmt)
	if _, err := aliceChannel.AddHTLC(htlc2); err != nil {
		t.Fatalf("unable to add htlc2: %v", err)
	}
	if _, err := bobChannel.ReceiveHTLC(htlc2); err != nil {
		t.Fatalf("unable to recv htlc2: %v", err)
	}

	// We'll now manually initiate a state transition between Alice and
	// bob.
	aliceSig, aliceHtlcSigs, err := aliceChannel.SignNextCommitment()
	if err != nil {
		t.Fatal(err)
	}
	err = bobChannel.ReceiveNewCommitment(aliceSig, aliceHtlcSigs)
	if err != nil {
		t.Fatal(err)
	}
	bobRevocation, _, err := bobChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatal(err)
	}
	bobSig, bobHtlcSigs, err := bobChannel.SignNextCommitment()
	if err != nil {
		t.Fatal(err)
	}

	// Alice should detect that she doesn't need to forward any HTLC's.
	aliceHtlcsToForward, err := aliceChannel.ReceiveRevocation(
		bobRevocation,
	)
	if err != nil {
		t.Fatal(err)
	}
	if len(aliceHtlcsToForward) != 0 {
		t.Fatalf("alice shouldn't forward any HTLC's, instead wants to "+
			"forward %v htlcs", len(aliceHtlcsToForward))
	}

	err = aliceChannel.ReceiveNewCommitment(bobSig, bobHtlcSigs)
	if err != nil {
		t.Fatal(err)
	}
	aliceRevocation, _, err := aliceChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatal(err)
	}

	// Bob on the other hand, should detect that he now has 2 incoming
	// HTLC's that he can forward along.
	bobHtlcsToForward, err := bobChannel.ReceiveRevocation(aliceRevocation)
	if err != nil {
		t.Fatal(err)
	}
	if len(bobHtlcsToForward) != 2 {
		t.Fatalf("bob should forward 2 hltcs, instead has %v",
			len(bobHtlcsToForward))
	}

	// We'll now restart both Alice and Bob. This emulates a reconnection
	// between the two peers.
	aliceChannel, err = restartChannel(aliceChannel)
	if err != nil {
		t.Fatalf("unable to restart alice: %v", err)
	}
	bobChannel, err = restartChannel(bobChannel)
	if err != nil {
		t.Fatalf("unable to restart bob: %v", err)
	}

	// With both nodes restarted, Bob will now attempt to cancel one of
	// Alice's HTLC's.
	err = bobChannel.FailHTLC(htlc2.ID, []byte("failreason"))
	if err != nil {
		t.Fatalf("unable to cancel HTLC: %v", err)
	}
	err = aliceChannel.ReceiveFailHTLC(htlc2.ID, []byte("bad"))
	if err != nil {
		t.Fatalf("unable to recv htlc cancel: %v", err)
	}

	// We'll now initiate another state transition, but this time Bob will
	// lead.
	bobSig, bobHtlcSigs, err = bobChannel.SignNextCommitment()
	if err != nil {
		t.Fatal(err)
	}
	err = aliceChannel.ReceiveNewCommitment(bobSig, bobHtlcSigs)
	if err != nil {
		t.Fatal(err)
	}
	aliceRevocation, _, err = aliceChannel.RevokeCurrentCommitment()
	if err != nil {
		t.Fatal(err)
	}
	aliceSig, aliceHtlcSigs, err = aliceChannel.SignNextCommitment()
	if err != nil {
		t.Fatal(err)
	}

	// At this point, Bob receives the revocation from Alice, which is now
	// his signal to examine all the HTLC's that have been locked in to
	// process.
	bobHtlcsToForward, err = bobChannel.ReceiveRevocation(aliceRevocation)
	if err != nil {
		t.Fatal(err)
	}

	// Bob should detect that he doesn't need to forward *any* HTLC's, as
	// he was the one that initiated extending the commitment chain of
	// Alice.
	if len(bobHtlcsToForward) != 0 {
		t.Fatalf("bob shouldn't forward any htlcs, but has: %v",
			spew.Sdump(bobHtlcsToForward))
	}
}

// TestInvalidCommitSigError tests that if the remote party sends us an invalid
// commitment signature, then we'll reject it and return a special error that
// contains information to allow the remote party to debug their issues.
func TestInvalidCommitSigError(t *testing.T) {
	t.Parallel()

	// First, we'll make a channel between Alice and Bob.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	// With the channel established, we'll now send a single HTLC from
	// Alice to Bob.
	var htlcAmt lnwire.MilliSatoshi = 100000
	htlc, _ := createHTLC(0, htlcAmt)
	if _, err := aliceChannel.AddHTLC(htlc); err != nil {
		t.Fatalf("unable to add htlc: %v", err)
	}
	if _, err := bobChannel.ReceiveHTLC(htlc); err != nil {
		t.Fatalf("unable to recv htlc: %v", err)
	}

	// Alice will now attempt to initiate a state transition.
	aliceSig, aliceHtlcSigs, err := aliceChannel.SignNextCommitment()
	if err != nil {
		t.Fatalf("unable to sign new commit: %v", err)
	}

	// Before the signature gets to Bob, we'll mutate it, such that the
	// signature is now actually invalid.
	aliceSig.R.Add(aliceSig.R, new(big.Int).SetInt64(1))

	// Bob should reject this new state, and return the proper error.
	err = bobChannel.ReceiveNewCommitment(aliceSig, aliceHtlcSigs)
	if err == nil {
		t.Fatalf("bob accepted invalid state but shouldn't have")
	}
	if _, ok := err.(*InvalidCommitSigError); !ok {
		t.Fatalf("bob sent incorrect error, expected %T, got %T",
			&InvalidCommitSigError{}, err)
	}
}

// TestChannelUnilateralCloseHtlcResolution tests that in the case of a
// unilateral channel closure, then the party that didn't broadcast the
// commitment is able to properly sweep all relevant outputs.
func TestChannelUnilateralCloseHtlcResolution(t *testing.T) {
	t.Parallel()

	// Create a test channel which will be used for the duration of this
	// unittest. The channel will be funded evenly with Alice having 5 BTC,
	// and Bob having 5 BTC.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(3)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	// We'll start off the test by adding an HTLC in both directions, then
	// initiating enough state transitions to lock both of them in.
	htlcAmount := lnwire.NewMSatFromSatoshis(20000)
	htlcAlice, _ := createHTLC(0, htlcAmount)
	if _, err := aliceChannel.AddHTLC(htlcAlice); err != nil {
		t.Fatalf("alice unable to add htlc: %v", err)
	}
	if _, err := bobChannel.ReceiveHTLC(htlcAlice); err != nil {
		t.Fatalf("bob unable to recv add htlc: %v", err)
	}
	htlcBob, preimageBob := createHTLC(0, htlcAmount)
	if _, err := bobChannel.AddHTLC(htlcBob); err != nil {
		t.Fatalf("bob unable to add htlc: %v", err)
	}
	if _, err := aliceChannel.ReceiveHTLC(htlcBob); err != nil {
		t.Fatalf("alice unable to recv add htlc: %v", err)
	}
	if err := forceStateTransition(aliceChannel, bobChannel); err != nil {
		t.Fatalf("Can't update the channel state: %v", err)
	}
	if err := forceStateTransition(bobChannel, aliceChannel); err != nil {
		t.Fatalf("Can't update the channel state: %v", err)
	}

	// With both HTLC's locked in, we'll now simulate Bob force closing the
	// transaction on Alice.
	bobForceClose, err := bobChannel.ForceClose()
	if err != nil {
		t.Fatalf("unable to close: %v", err)
	}

	// Now that Bob has force closed, we'll modify Alice's pre image cache
	// such that she now gains the ability to also settle the incoming HTLC
	// from Bob.
	aliceChannel.pCache.AddPreimage(preimageBob[:])

	// We'll then use Bob's transaction to trigger a spend notification for
	// Alice.
	closeTx := bobForceClose.CloseTx
	commitTxHash := closeTx.TxHash()
	spendDetail := &chainntnfs.SpendDetail{
		SpendingTx:    closeTx,
		SpenderTxHash: &commitTxHash,
	}
	aliceCloseSummary, err := NewUnilateralCloseSummary(
		aliceChannel.channelState, aliceChannel.signer, aliceChannel.pCache,
		spendDetail, aliceChannel.channelState.RemoteCommitment,
	)
	if err != nil {
		t.Fatalf("unable to create alice close summary: %v", err)
	}

	// She should detect that she can sweep both the outgoing HTLC as well
	// as the incoming one from Bob.
	if len(aliceCloseSummary.HtlcResolutions.OutgoingHTLCs) != 1 {
		t.Fatalf("alice out htlc resolutions not populated: expected %v "+
			"htlcs, got %v htlcs",
			1, len(aliceCloseSummary.HtlcResolutions.OutgoingHTLCs))
	}
	if len(aliceCloseSummary.HtlcResolutions.IncomingHTLCs) != 1 {
		t.Fatalf("alice in htlc resolutions not populated: expected %v "+
			"htlcs, got %v htlcs",
			1, len(aliceCloseSummary.HtlcResolutions.IncomingHTLCs))
	}

	outHtlcResolution := aliceCloseSummary.HtlcResolutions.OutgoingHTLCs[0]
	inHtlcResolution := aliceCloseSummary.HtlcResolutions.IncomingHTLCs[0]

	// First, we'll ensure that Alice can directly spend the outgoing HTLC
	// given a transaction with the proper lock time set.
	receiverHtlcScript := closeTx.TxOut[outHtlcResolution.ClaimOutpoint.Index].PkScript
	sweepTx := wire.NewMsgTx(2)
	sweepTx.AddTxIn(&wire.TxIn{
		PreviousOutPoint: outHtlcResolution.ClaimOutpoint,
	})
	sweepTx.AddTxOut(&wire.TxOut{
		PkScript: receiverHtlcScript,
		Value:    outHtlcResolution.SweepSignDesc.Output.Value,
	})
	outHtlcResolution.SweepSignDesc.InputIndex = 0
	outHtlcResolution.SweepSignDesc.SigHashes = txscript.NewTxSigHashes(
		sweepTx,
	)
	sweepTx.LockTime = outHtlcResolution.Expiry

	// With the transaction constructed, we'll generate a witness that
	// should be valid for it, and verify using an instance of Script.
	sweepTx.TxIn[0].Witness, err = receiverHtlcSpendTimeout(
		aliceChannel.signer, &outHtlcResolution.SweepSignDesc,
		sweepTx, int32(outHtlcResolution.Expiry),
	)
	if err != nil {
		t.Fatalf("unable to witness: %v", err)
	}
	vm, err := txscript.NewEngine(
		outHtlcResolution.SweepSignDesc.Output.PkScript,
		sweepTx, 0, txscript.StandardVerifyFlags, nil,
		nil, outHtlcResolution.SweepSignDesc.Output.Value,
	)
	if err != nil {
		t.Fatalf("unable to create engine: %v", err)
	}
	if err := vm.Execute(); err != nil {
		t.Fatalf("htlc timeout spend is invalid: %v", err)
	}

	// Next, we'll ensure that we're able to sweep the incoming HTLC with a
	// similar sweep transaction, this time using the payment pre-image.
	senderHtlcScript := closeTx.TxOut[inHtlcResolution.ClaimOutpoint.Index].PkScript
	sweepTx = wire.NewMsgTx(2)
	sweepTx.AddTxIn(&wire.TxIn{
		PreviousOutPoint: inHtlcResolution.ClaimOutpoint,
	})
	sweepTx.AddTxOut(&wire.TxOut{
		PkScript: senderHtlcScript,
		Value:    inHtlcResolution.SweepSignDesc.Output.Value,
	})
	inHtlcResolution.SweepSignDesc.InputIndex = 0
	inHtlcResolution.SweepSignDesc.SigHashes = txscript.NewTxSigHashes(
		sweepTx,
	)
	sweepTx.TxIn[0].Witness, err = SenderHtlcSpendRedeem(
		aliceChannel.signer, &inHtlcResolution.SweepSignDesc,
		sweepTx, preimageBob[:],
	)
	if err != nil {
		t.Fatalf("unable to generate witness for success "+
			"output: %v", err)
	}

	// Finally, we'll verify the constructed witness to ensure that Alice
	// can properly sweep the output.
	vm, err = txscript.NewEngine(
		inHtlcResolution.SweepSignDesc.Output.PkScript,
		sweepTx, 0, txscript.StandardVerifyFlags, nil,
		nil, inHtlcResolution.SweepSignDesc.Output.Value,
	)
	if err != nil {
		t.Fatalf("unable to create engine: %v", err)
	}
	if err := vm.Execute(); err != nil {
		t.Fatalf("htlc timeout spend is invalid: %v", err)
	}
}

// TestDesyncHTLCs checks that we cannot add HTLCs that would make the
// balance negative, when the remote and local update logs are desynced.
func TestDesyncHTLCs(t *testing.T) {
	t.Parallel()

	// We'll kick off the test by creating our channels which both are
	// loaded with 5 BTC each.
	aliceChannel, bobChannel, cleanUp, err := createTestChannels(1)
	if err != nil {
		t.Fatalf("unable to create test channels: %v", err)
	}
	defer cleanUp()

	// First add one HTLC of value 4.1 BTC.
	htlcAmt := lnwire.NewMSatFromSatoshis(4.1 * btcutil.SatoshiPerBitcoin)
	htlc, _ := createHTLC(0, htlcAmt)
	aliceIndex, err := aliceChannel.AddHTLC(htlc)
	if err != nil {
		t.Fatalf("unable to add htlc: %v", err)
	}
	bobIndex, err := bobChannel.ReceiveHTLC(htlc)
	if err != nil {
		t.Fatalf("unable to recv htlc: %v", err)
	}

	// Lock this HTLC in.
	if err := forceStateTransition(aliceChannel, bobChannel); err != nil {
		t.Fatalf("unable to complete state update: %v", err)
	}

	// Now let let Bob fail this HTLC.
	if err := bobChannel.FailHTLC(bobIndex, []byte("failreason")); err != nil {
		t.Fatalf("unable to cancel HTLC: %v", err)
	}
	if err := aliceChannel.ReceiveFailHTLC(aliceIndex, []byte("bad")); err != nil {
		t.Fatalf("unable to recv htlc cancel: %v", err)
	}

	// Alice now has gotten all here original balance (5 BTC) back,
	// however, adding a new HTLC at this point SHOULD fail, since
	// if she add the HTLC and sign the next state, Bob cannot assume
	// she received the FailHTLC, and must assume she doesn't have
	// the necessary balance available.
	//
	// We try adding an HTLC of value 1 BTC, which should fail
	// because the balance is unavailable.
	htlcAmt = lnwire.NewMSatFromSatoshis(1 * btcutil.SatoshiPerBitcoin)
	htlc, _ = createHTLC(1, htlcAmt)
	if _, err = aliceChannel.AddHTLC(htlc); err != ErrInsufficientBalance {
		t.Fatalf("expected ErrInsufficientBalance, instead received: %v",
			err)
	}

	// Now do a state transition, which will ACK the FailHTLC, making
	// Alice able to add the new HTLC.
	if err := forceStateTransition(aliceChannel, bobChannel); err != nil {
		t.Fatalf("unable to complete state update: %v", err)
	}
	if _, err = aliceChannel.AddHTLC(htlc); err != nil {
		t.Fatalf("unable to add htlc: %v", err)
	}
}

// TODO(roasbeef): testing.Quick test case for retrans!!!