package lnwallet

import (
	"bytes"
	"crypto/sha256"
	"fmt"
	"io/ioutil"
	"math/rand"
	"os"
	"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)
)

type mockSigner struct {
	key *btcec.PrivateKey
}

func (m *mockSigner) SignOutputRaw(tx *wire.MsgTx, signDesc *SignDescriptor) ([]byte, error) {
	amt := signDesc.Output.Value
	witnessScript := signDesc.WitnessScript
	privKey := m.key

	if !privKey.PubKey().IsEqual(signDesc.PubKey) {
		return nil, fmt.Errorf("incorrect key passed")
	}

	switch {
	case signDesc.SingleTweak != nil:
		privKey = TweakPrivKey(privKey,
			signDesc.SingleTweak)
	case signDesc.DoubleTweak != nil:
		privKey = DeriveRevocationPrivKey(privKey,
			signDesc.DoubleTweak)
	}

	sig, err := txscript.RawTxInWitnessSignature(tx, signDesc.SigHashes,
		signDesc.InputIndex, amt, witnessScript, txscript.SigHashAll,
		privKey)
	if err != nil {
		return nil, err
	}

	return sig[:len(sig)-1], nil
}
func (m *mockSigner) ComputeInputScript(tx *wire.MsgTx, signDesc *SignDescriptor) (*InputScript, error) {

	// TODO(roasbeef): expose tweaked signer from lnwallet so don't need to
	// duplicate this code?

	privKey := m.key

	switch {
	case signDesc.SingleTweak != nil:
		privKey = TweakPrivKey(privKey,
			signDesc.SingleTweak)
	case signDesc.DoubleTweak != nil:
		privKey = DeriveRevocationPrivKey(privKey,
			signDesc.DoubleTweak)
	}

	witnessScript, err := txscript.WitnessSignature(tx, signDesc.SigHashes,
		signDesc.InputIndex, signDesc.Output.Value, signDesc.Output.PkScript,
		txscript.SigHashAll, privKey, true)
	if err != nil {
		return nil, err
	}

	return &InputScript{
		Witness: witnessScript,
	}, nil
}

type mockNotfier struct {
}

func (m *mockNotfier) RegisterConfirmationsNtfn(txid *chainhash.Hash, numConfs, heightHint uint32) (*chainntnfs.ConfirmationEvent, error) {
	return nil, nil
}
func (m *mockNotfier) RegisterBlockEpochNtfn() (*chainntnfs.BlockEpochEvent, error) {
	return nil, nil
}

func (m *mockNotfier) Start() error {
	return nil
}

func (m *mockNotfier) Stop() error {
	return nil
}
func (m *mockNotfier) RegisterSpendNtfn(outpoint *wire.OutPoint, heightHint uint32) (*chainntnfs.SpendEvent, error) {
	return &chainntnfs.SpendEvent{
		Spend: make(chan *chainntnfs.SpendDetail),
		Cancel: func() {
		},
	}, nil
}

// 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 channels 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) {
	aliceKeyPriv, aliceKeyPub := btcec.PrivKeyFromBytes(btcec.S256(),
		testWalletPrivKey)
	bobKeyPriv, bobKeyPub := btcec.PrivKeyFromBytes(btcec.S256(),
		bobsPrivKey)

	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)

	aliceCfg := channeldb.ChannelConfig{
		ChannelConstraints: channeldb.ChannelConstraints{
			DustLimit:        aliceDustLimit,
			MaxPendingAmount: lnwire.MilliSatoshi(rand.Int63()),
			ChanReserve:      btcutil.Amount(rand.Int63()),
			MinHTLC:          lnwire.MilliSatoshi(rand.Int63()),
			MaxAcceptedHtlcs: uint16(rand.Int31()),
		},
		CsvDelay:            uint16(csvTimeoutAlice),
		MultiSigKey:         aliceKeyPub,
		RevocationBasePoint: aliceKeyPub,
		PaymentBasePoint:    aliceKeyPub,
		DelayBasePoint:      aliceKeyPub,
	}
	bobCfg := channeldb.ChannelConfig{
		ChannelConstraints: channeldb.ChannelConstraints{
			DustLimit:        bobDustLimit,
			MaxPendingAmount: lnwire.MilliSatoshi(rand.Int63()),
			ChanReserve:      btcutil.Amount(rand.Int63()),
			MinHTLC:          lnwire.MilliSatoshi(rand.Int63()),
			MaxAcceptedHtlcs: uint16(rand.Int31()),
		},
		CsvDelay:            uint16(csvTimeoutBob),
		MultiSigKey:         bobKeyPub,
		RevocationBasePoint: bobKeyPub,
		PaymentBasePoint:    bobKeyPub,
		DelayBasePoint:      bobKeyPub,
	}

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

	aliceRoot := DeriveRevocationRoot(aliceKeyPriv, testHdSeed, bobKeyPub)
	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
	}

	var obsfucator [StateHintSize]byte
	copy(obsfucator[:], aliceFirstRevoke[:])

	estimator := &StaticFeeEstimator{24, 6}
	feePerKw := btcutil.Amount(estimator.EstimateFeePerWeight(1) * 1000)
	commitFee := calcStaticFee(0)
	aliceChannelState := &channeldb.OpenChannel{
		LocalChanCfg:            aliceCfg,
		RemoteChanCfg:           bobCfg,
		IdentityPub:             aliceKeyPub,
		CommitFee:               commitFee,
		FundingOutpoint:         *prevOut,
		ChanType:                channeldb.SingleFunder,
		FeePerKw:                feePerKw,
		IsInitiator:             true,
		Capacity:                channelCapacity,
		LocalBalance:            lnwire.NewMSatFromSatoshis(channelBal - commitFee),
		RemoteBalance:           lnwire.NewMSatFromSatoshis(channelBal),
		CommitTx:                *aliceCommitTx,
		CommitSig:               bytes.Repeat([]byte{1}, 71),
		RemoteCurrentRevocation: bobCommitPoint,
		RevocationProducer:      alicePreimageProducer,
		RevocationStore:         shachain.NewRevocationStore(),
		Db:                      dbAlice,
	}
	bobChannelState := &channeldb.OpenChannel{
		LocalChanCfg:            bobCfg,
		RemoteChanCfg:           aliceCfg,
		IdentityPub:             bobKeyPub,
		FeePerKw:                feePerKw,
		CommitFee:               commitFee,
		FundingOutpoint:         *prevOut,
		ChanType:                channeldb.SingleFunder,
		IsInitiator:             false,
		Capacity:                channelCapacity,
		LocalBalance:            lnwire.NewMSatFromSatoshis(channelBal),
		RemoteBalance:           lnwire.NewMSatFromSatoshis(channelBal - commitFee),
		CommitTx:                *bobCommitTx,
		CommitSig:               bytes.Repeat([]byte{1}, 71),
		RemoteCurrentRevocation: aliceCommitPoint,
		RevocationProducer:      bobPreimageProducer,
		RevocationStore:         shachain.NewRevocationStore(),
		Db:                      dbBob,
	}

	aliceSigner := &mockSigner{aliceKeyPriv}
	bobSigner := &mockSigner{bobKeyPriv}

	notifier := &mockNotfier{}

	channelAlice, err := NewLightningChannel(aliceSigner, notifier,
		estimator, aliceChannelState)
	if err != nil {
		return nil, nil, nil, err
	}
	channelBob, err := NewLightningChannel(bobSigner, notifier,
		estimator, bobChannelState)
	if 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(data int, amount lnwire.MilliSatoshi) (*lnwire.UpdateAddHTLC, [32]byte) {
	preimage := bytes.Repeat([]byte{byte(data)}, 32)
	paymentHash := sha256.Sum256(preimage)

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

	return &lnwire.UpdateAddHTLC{
		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.
	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)
	}

	// 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.CommitTx.TxOut) != 3 {
		t.Fatalf("alice should have three commitment outputs, instead "+
			"have %v", len(aliceChannel.channelState.CommitTx.TxOut))
	}
	if len(bobChannel.channelState.CommitTx.TxOut) != 3 {
		t.Fatalf("bob should have three commitment outputs, instead "+
			"have %v", len(bobChannel.channelState.CommitTx.TxOut))
	}
	assertOutputExistsByValue(t, &aliceChannel.channelState.CommitTx,
		htlcAmt.ToSatoshis())
	assertOutputExistsByValue(t, &bobChannel.channelState.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)
	settleIndex, _, err := bobChannel.SettleHTLC(preimage)
	if err != nil {
		t.Fatalf("bob unable to settle inbound htlc: %v", err)
	}
	if err := aliceChannel.ReceiveHTLCSettle(preimage, settleIndex); 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 := 1; 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)
		checkSize(bobChannel, i)
	}

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

		settleIndex, _, err := bobChannel.SettleHTLC(preimage)
		if err != nil {
			t.Fatalf("bob unable to settle inbound htlc: %v", err)
		}
		err = aliceChannel.ReceiveHTLCSettle(preimage, settleIndex)
		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-1)
		checkSize(bobChannel, i-1)
	}
}

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.FeePerKw)
	bobFeeRate := uint64(bobChannel.channelState.FeePerKw)

	// We'll store with both Alice and Bob creating a new close proposal
	// with the same fee.
	aliceFee := 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 := 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.
func TestForceClose(t *testing.T) {
	t.Parallel()

	// TODO(roasbeef): modify to add some HTLC's before closing?

	// 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.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)
	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 recv add htlc: %v", err)
	}
	if err := forceStateTransition(aliceChannel, bobChannel); err != nil {
		t.Fatalf("Can't update the channel state: %v", err)
	}

	// Now with the HTLC in tact, we'll perform a force close on Alice's
	// part.
	closeSummary, err := aliceChannel.ForceClose()
	if err != nil {
		t.Fatalf("unable to force close channel: %v", err)
	}

	// Alice's force close summary should have a single HTLC resolution.
	if len(closeSummary.HtlcResolutions) != 1 {
		t.Fatalf("alice htlc resolutions not populated: expected %v "+
			"htlcs, got %v htlcs",
			1, len(closeSummary.HtlcResolutions))
	}

	// The SelfOutputSignDesc should be non-nil since the output to-self is
	// non-dust.
	if closeSummary.SelfOutputSignDesc == 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 !closeSummary.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 an additional HTLC to the commitment transaction.
	totalCommitWeight := commitWeight + htlcWeight
	feePerKw := aliceChannel.channelState.FeePerKw
	commitFee := btcutil.Amount((int64(feePerKw) * totalCommitWeight) / 1000)
	expectedAmount := (aliceChannel.Capacity / 2) - htlcAmount.ToSatoshis() - commitFee
	if closeSummary.SelfOutputSignDesc.Output.Value != int64(expectedAmount) {
		t.Fatalf("alice incorrect output value in SelfOutputSignDesc, "+
			"expected %v, got %v", int64(expectedAmount),
			closeSummary.SelfOutputSignDesc.Output.Value)
	}

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

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

	// 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.
	var senderHtlcPkScript []byte
	for _, txOut := range closeSummary.CloseTx.TxOut {
		if txOut.Value == int64(htlcAmount.ToSatoshis()) {
			senderHtlcPkScript = txOut.PkScript
			break
		}
	}

	if senderHtlcPkScript == nil {
		t.Fatalf("unable to find htlc script")
	}

	// First, verify that the second level transaction can properly spend
	// the multi-sig clause within the
	htlcResolution := closeSummary.HtlcResolutions[0]
	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.CommitTx.TxHash()
	if !bytes.Equal(closeTxHash[:], commitTxHash[:]) {
		t.Fatalf("alice: incorrect close transaction txid")
	}

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

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

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

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

// 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.LocalBalance
	bobAmount := bobChannel.channelState.LocalBalance

	// Have Bobs' to-self output be below her dust limit and check
	// ForceCloseSummary again on both peers.
	htlc, preimage := createHTLC(0, bobAmount-htlcAmount)
	if _, err := bobChannel.AddHTLC(htlc); err != nil {
		t.Fatalf("alice unable to add htlc: %v", err)
	}
	if _, err := aliceChannel.ReceiveHTLC(htlc); 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.
	settleIndex, _, err := aliceChannel.SettleHTLC(preimage)
	if err != nil {
		t.Fatalf("bob unable to settle inbound htlc: %v", err)
	}
	err = bobChannel.ReceiveHTLCSettle(preimage, settleIndex)
	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.LocalBalance
	bobAmount = bobChannel.channelState.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.
	if closeSummary.SelfOutputSignDesc == nil {
		t.Fatalf("alice fails to include to-self output in ForceCloseSummary")
	}
	if !closeSummary.SelfOutputSignDesc.PubKey.IsEqual(
		aliceChannel.channelState.LocalChanCfg.DelayBasePoint,
	) {
		t.Fatalf("alice incorrect pubkey in SelfOutputSignDesc")
	}
	if closeSummary.SelfOutputSignDesc.Output.Value !=
		int64(aliceAmount.ToSatoshis()) {
		t.Fatalf("alice incorrect output value in SelfOutputSignDesc, "+
			"expected %v, got %v",
			aliceChannel.channelState.LocalBalance.ToSatoshis(),
			closeSummary.SelfOutputSignDesc.Output.Value)
	}

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

	closeTxHash := closeSummary.CloseTx.TxHash()
	commitTxHash := aliceChannel.channelState.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.
	if closeSummary.SelfOutputSignDesc != nil {
		t.Fatalf("bob incorrectly includes to-self output in " +
			"ForceCloseSummary")
	}

	closeTxHash = closeSummary.CloseTx.TxHash()
	commitTxHash = bobChannel.channelState.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.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.LocalBalance +
		aliceChannel.channelState.RemoteBalance +
		lnwire.NewMSatFromSatoshis(aliceChannel.channelState.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.LocalBalance +
		bobChannel.channelState.RemoteBalance +
		lnwire.NewMSatFromSatoshis(bobChannel.channelState.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.CommitFee != defaultFee {
		t.Fatalf("dust htlc amounts not subtracted from commitment fee "+
			"expected %v, got %v", defaultFee,
			aliceChannel.channelState.CommitFee)
	}
	if bobChannel.channelState.CommitFee != defaultFee {
		t.Fatalf("dust htlc amounts not subtracted from commitment fee "+
			"expected %v, got %v", defaultFee,
			bobChannel.channelState.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.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.FeePerKw))
	htlcAmount := lnwire.NewMSatFromSatoshis(htlcSat)

	htlc, preimage := 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)
	}

	// 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.CommitFee != defaultFee {
		t.Fatalf("dust htlc amount was subtracted from commitment fee "+
			"expected %v, got %v", defaultFee,
			bobChannel.channelState.CommitFee)
	}

	// Settle HTLC and create a new commitment state.
	settleIndex, _, err := bobChannel.SettleHTLC(preimage)
	if err != nil {
		t.Fatalf("bob unable to settle inbound htlc: %v", err)
	}
	err = aliceChannel.ReceiveHTLCSettle(preimage, settleIndex)
	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.LocalBalance.ToSatoshis()
	htlcSat := aliceBalance - defaultFee
	htlcSat += htlcSuccessFee(aliceChannel.channelState.FeePerKw)

	htlcAmount := lnwire.NewMSatFromSatoshis(htlcSat)

	htlc, preimage := 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("state transition error: %v", err)
	}
	settleIndex, _, err := bobChannel.SettleHTLC(preimage)
	if err != nil {
		t.Fatalf("bob unable to settle inbound htlc: %v", err)
	}
	err = aliceChannel.ReceiveHTLCSettle(preimage, settleIndex)
	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()

	if err := aliceChannel.channelState.FullSync(); err != nil {
		t.Fatalf("unable to sync alice's channel: %v", err)
	}
	if err := bobChannel.channelState.FullSync(); err != nil {
		t.Fatalf("unable to sync bob's channel: %v", err)
	}

	const numHtlcs = 4
	htlcAmt := lnwire.NewMSatFromSatoshis(20000)

	// 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{
			PaymentHash: rHash,
			Amount:      htlcAmt,
			Expiry:      uint32(10),
		}

		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),
	}
	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)
	}
	notifier := aliceChannel.channelEvents
	aliceChannelNew, err := NewLightningChannel(aliceChannel.signer,
		notifier, aliceChannel.feeEstimator, aliceChannels[0])
	if err != nil {
		t.Fatalf("unable to create new channel: %v", err)
	}
	bobChannelNew, err := NewLightningChannel(bobChannel.signer, notifier,
		bobChannel.feeEstimator, 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.updateIndex {
		htlc := entry.Value.(*PaymentDescriptor)
		restoredHtlc := aliceChannelNew.localUpdateLog.lookup(htlc.Index)
		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.updateIndex {
		htlc := entry.Value.(*PaymentDescriptor)
		restoredHtlc := aliceChannelNew.remoteUpdateLog.lookup(htlc.Index)
		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.updateIndex {
		htlc := entry.Value.(*PaymentDescriptor)
		restoredHtlc := bobChannelNew.localUpdateLog.lookup(htlc.Index)
		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.updateIndex {
		htlc := entry.Value.(*PaymentDescriptor)
		restoredHtlc := bobChannelNew.remoteUpdateLog.lookup(htlc.Index)
		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++ {
		settleIndex, _, err := bobChannelNew.SettleHTLC(alicePreimage)
		if err != nil {
			t.Fatalf("unable to settle htlc: %v", err)
		}
		err = aliceChannelNew.ReceiveHTLCSettle(alicePreimage, settleIndex)
		if err != nil {
			t.Fatalf("unable to settle htlc: %v", err)
		}
	}
	settleIndex, _, err := aliceChannelNew.SettleHTLC(bobPreimage)
	if err != nil {
		t.Fatalf("unable to settle htlc: %v", err)
	}
	err = bobChannelNew.ReceiveHTLCSettle(bobPreimage, settleIndex)
	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)
	}
}

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,
	}
	paymentHash := htlc.PaymentHash

	if _, err := aliceChannel.AddHTLC(htlc); err != nil {
		t.Fatalf("unable to add alice htlc: %v", err)
	}
	if _, err := bobChannel.ReceiveHTLC(htlc); 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.LocalBalance.ToSatoshis() != aliceExpectedBalance {
		t.Fatalf("Alice's balance is wrong: expected %v, got %v",
			aliceExpectedBalance,
			aliceChannel.channelState.LocalBalance.ToSatoshis())
	}

	// Now, with the HTLC committed on both sides, trigger a cancellation
	// from Bob to Alice, removing the HTLC.
	htlcCancelIndex, err := bobChannel.FailHTLC(paymentHash)
	if err != nil {
		t.Fatalf("unable to cancel HTLC: %v", err)
	}
	if _, err := aliceChannel.ReceiveFailHTLC(htlcCancelIndex); 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.LocalBalance.ToSatoshis() !=
		expectedBalance-calcStaticFee(0) {

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

		t.Fatalf("balance is wrong: expected %v, got %v",
			bobChannel.channelState.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.FeePerKw)
	bobFeeRate := uint64(bobChannel.channelState.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.LocalBalance = aliceBalance
		aliceChannel.channelState.RemoteBalance = bobBalance
		bobChannel.channelState.LocalBalance = bobBalance
		bobChannel.channelState.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 := aliceChannel.CalcFee(aliceFeeRate)
	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 := bobChannel.CalcFee(bobFeeRate)
	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))
	}
	if closeTx.TxOut[0].Value != int64(aliceBal.ToSatoshis()-calcStaticFee(0)) {
		t.Fatalf("alice's balance is incorrect: expected %v, got %v",
			int64(aliceBal.ToSatoshis()-calcStaticFee(0)),
			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 veriefies 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.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.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 rocess 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.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.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 rocess 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.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.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 revokation 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.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.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.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.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 rocess 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.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.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)
	}
}