package lnwallet

import (
	"crypto/rand"
	"encoding/binary"
	"encoding/hex"
	"io"
	"io/ioutil"
	prand "math/rand"
	"net"
	"os"

	"github.com/btcsuite/btcd/btcec"
	"github.com/btcsuite/btcd/chaincfg/chainhash"
	"github.com/btcsuite/btcd/wire"
	"github.com/btcsuite/btcutil"
	"github.com/lightningnetwork/lnd/channeldb"
	"github.com/lightningnetwork/lnd/input"
	"github.com/lightningnetwork/lnd/keychain"
	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
	"github.com/lightningnetwork/lnd/lnwire"
	"github.com/lightningnetwork/lnd/shachain"
)

var (
	// 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,
	}

	// A serializable txn for testing funding txn.
	testTx = &wire.MsgTx{
		Version: 1,
		TxIn: []*wire.TxIn{
			{
				PreviousOutPoint: wire.OutPoint{
					Hash:  chainhash.Hash{},
					Index: 0xffffffff,
				},
				SignatureScript: []byte{0x04, 0x31, 0xdc, 0x00, 0x1b, 0x01, 0x62},
				Sequence:        0xffffffff,
			},
		},
		TxOut: []*wire.TxOut{
			{
				Value: 5000000000,
				PkScript: []byte{
					0x41, // OP_DATA_65
					0x04, 0xd6, 0x4b, 0xdf, 0xd0, 0x9e, 0xb1, 0xc5,
					0xfe, 0x29, 0x5a, 0xbd, 0xeb, 0x1d, 0xca, 0x42,
					0x81, 0xbe, 0x98, 0x8e, 0x2d, 0xa0, 0xb6, 0xc1,
					0xc6, 0xa5, 0x9d, 0xc2, 0x26, 0xc2, 0x86, 0x24,
					0xe1, 0x81, 0x75, 0xe8, 0x51, 0xc9, 0x6b, 0x97,
					0x3d, 0x81, 0xb0, 0x1c, 0xc3, 0x1f, 0x04, 0x78,
					0x34, 0xbc, 0x06, 0xd6, 0xd6, 0xed, 0xf6, 0x20,
					0xd1, 0x84, 0x24, 0x1a, 0x6a, 0xed, 0x8b, 0x63,
					0xa6, // 65-byte signature
					0xac, // OP_CHECKSIG
				},
			},
		},
		LockTime: 5,
	}

	// A valid, DER-encoded signature (taken from btcec unit tests).
	testSigBytes = []byte{
		0x30, 0x44, 0x02, 0x20, 0x4e, 0x45, 0xe1, 0x69,
		0x32, 0xb8, 0xaf, 0x51, 0x49, 0x61, 0xa1, 0xd3,
		0xa1, 0xa2, 0x5f, 0xdf, 0x3f, 0x4f, 0x77, 0x32,
		0xe9, 0xd6, 0x24, 0xc6, 0xc6, 0x15, 0x48, 0xab,
		0x5f, 0xb8, 0xcd, 0x41, 0x02, 0x20, 0x18, 0x15,
		0x22, 0xec, 0x8e, 0xca, 0x07, 0xde, 0x48, 0x60,
		0xa4, 0xac, 0xdd, 0x12, 0x90, 0x9d, 0x83, 0x1c,
		0xc5, 0x6c, 0xbb, 0xac, 0x46, 0x22, 0x08, 0x22,
		0x21, 0xa8, 0x76, 0x8d, 0x1d, 0x09,
	}
)

// CreateTestChannels creates to fully populated channels to be used within
// testing fixtures. The channels will be returned as if the funding process
// has just completed.  The channel itself is funded with 10 BTC, with 5 BTC
// allocated to each side. Within the channel, Alice is the initiator. The
// function also returns a "cleanup" function that is meant to be called once
// the test has been finalized. The clean up function will remote all temporary
// files created. If tweaklessCommits is true, then the commits within the
// channels will use the new format, otherwise the legacy format.
func CreateTestChannels(chanType channeldb.ChannelType) (
	*LightningChannel, *LightningChannel, func(), error) {

	channelCapacity, err := btcutil.NewAmount(10)
	if err != nil {
		return nil, nil, nil, err
	}

	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: prand.Uint32(),
	}
	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.NewMSatFromSatoshis(channelCapacity),
			ChanReserve:      channelCapacity / 100,
			MinHTLC:          0,
			MaxAcceptedHtlcs: input.MaxHTLCNumber / 2,
			CsvDelay:         uint16(csvTimeoutAlice),
		},
		MultiSigKey: keychain.KeyDescriptor{
			PubKey: aliceKeys[0].PubKey(),
		},
		RevocationBasePoint: keychain.KeyDescriptor{
			PubKey: aliceKeys[1].PubKey(),
		},
		PaymentBasePoint: keychain.KeyDescriptor{
			PubKey: aliceKeys[2].PubKey(),
		},
		DelayBasePoint: keychain.KeyDescriptor{
			PubKey: aliceKeys[3].PubKey(),
		},
		HtlcBasePoint: keychain.KeyDescriptor{
			PubKey: aliceKeys[4].PubKey(),
		},
	}
	bobCfg := channeldb.ChannelConfig{
		ChannelConstraints: channeldb.ChannelConstraints{
			DustLimit:        bobDustLimit,
			MaxPendingAmount: lnwire.NewMSatFromSatoshis(channelCapacity),
			ChanReserve:      channelCapacity / 100,
			MinHTLC:          0,
			MaxAcceptedHtlcs: input.MaxHTLCNumber / 2,
			CsvDelay:         uint16(csvTimeoutBob),
		},
		MultiSigKey: keychain.KeyDescriptor{
			PubKey: bobKeys[0].PubKey(),
		},
		RevocationBasePoint: keychain.KeyDescriptor{
			PubKey: bobKeys[1].PubKey(),
		},
		PaymentBasePoint: keychain.KeyDescriptor{
			PubKey: bobKeys[2].PubKey(),
		},
		DelayBasePoint: keychain.KeyDescriptor{
			PubKey: bobKeys[3].PubKey(),
		},
		HtlcBasePoint: keychain.KeyDescriptor{
			PubKey: bobKeys[4].PubKey(),
		},
	}

	bobRoot, err := chainhash.NewHash(bobKeys[0].Serialize())
	if err != nil {
		return nil, nil, nil, err
	}
	bobPreimageProducer := shachain.NewRevocationProducer(*bobRoot)
	bobFirstRevoke, err := bobPreimageProducer.AtIndex(0)
	if err != nil {
		return nil, nil, nil, err
	}
	bobCommitPoint := input.ComputeCommitmentPoint(bobFirstRevoke[:])

	aliceRoot, err := chainhash.NewHash(aliceKeys[0].Serialize())
	if err != nil {
		return nil, nil, nil, err
	}
	alicePreimageProducer := shachain.NewRevocationProducer(*aliceRoot)
	aliceFirstRevoke, err := alicePreimageProducer.AtIndex(0)
	if err != nil {
		return nil, nil, nil, err
	}
	aliceCommitPoint := input.ComputeCommitmentPoint(aliceFirstRevoke[:])

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

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

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

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

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

	estimator := chainfee.NewStaticEstimator(6000, 0)
	feePerKw, err := estimator.EstimateFeePerKW(1)
	if err != nil {
		return nil, nil, nil, err
	}
	commitFee := calcStaticFee(chanType, 0)
	var anchorAmt btcutil.Amount
	if chanType.HasAnchors() {
		anchorAmt += 2 * anchorSize
	}

	aliceBalance := lnwire.NewMSatFromSatoshis(
		channelBal - commitFee - anchorAmt,
	)
	bobBalance := lnwire.NewMSatFromSatoshis(channelBal)

	aliceLocalCommit := channeldb.ChannelCommitment{
		CommitHeight:  0,
		LocalBalance:  aliceBalance,
		RemoteBalance: bobBalance,
		CommitFee:     commitFee,
		FeePerKw:      btcutil.Amount(feePerKw),
		CommitTx:      aliceCommitTx,
		CommitSig:     testSigBytes,
	}
	aliceRemoteCommit := channeldb.ChannelCommitment{
		CommitHeight:  0,
		LocalBalance:  aliceBalance,
		RemoteBalance: bobBalance,
		CommitFee:     commitFee,
		FeePerKw:      btcutil.Amount(feePerKw),
		CommitTx:      bobCommitTx,
		CommitSig:     testSigBytes,
	}
	bobLocalCommit := channeldb.ChannelCommitment{
		CommitHeight:  0,
		LocalBalance:  bobBalance,
		RemoteBalance: aliceBalance,
		CommitFee:     commitFee,
		FeePerKw:      btcutil.Amount(feePerKw),
		CommitTx:      bobCommitTx,
		CommitSig:     testSigBytes,
	}
	bobRemoteCommit := channeldb.ChannelCommitment{
		CommitHeight:  0,
		LocalBalance:  bobBalance,
		RemoteBalance: aliceBalance,
		CommitFee:     commitFee,
		FeePerKw:      btcutil.Amount(feePerKw),
		CommitTx:      aliceCommitTx,
		CommitSig:     testSigBytes,
	}

	var chanIDBytes [8]byte
	if _, err := io.ReadFull(rand.Reader, chanIDBytes[:]); err != nil {
		return nil, nil, nil, err
	}

	shortChanID := lnwire.NewShortChanIDFromInt(
		binary.BigEndian.Uint64(chanIDBytes[:]),
	)

	aliceChannelState := &channeldb.OpenChannel{
		LocalChanCfg:            aliceCfg,
		RemoteChanCfg:           bobCfg,
		IdentityPub:             aliceKeys[0].PubKey(),
		FundingOutpoint:         *prevOut,
		ShortChannelID:          shortChanID,
		ChanType:                chanType,
		IsInitiator:             true,
		Capacity:                channelCapacity,
		RemoteCurrentRevocation: bobCommitPoint,
		RevocationProducer:      alicePreimageProducer,
		RevocationStore:         shachain.NewRevocationStore(),
		LocalCommitment:         aliceLocalCommit,
		RemoteCommitment:        aliceRemoteCommit,
		Db:                      dbAlice,
		Packager:                channeldb.NewChannelPackager(shortChanID),
		FundingTxn:              testTx,
	}
	bobChannelState := &channeldb.OpenChannel{
		LocalChanCfg:            bobCfg,
		RemoteChanCfg:           aliceCfg,
		IdentityPub:             bobKeys[0].PubKey(),
		FundingOutpoint:         *prevOut,
		ShortChannelID:          shortChanID,
		ChanType:                chanType,
		IsInitiator:             false,
		Capacity:                channelCapacity,
		RemoteCurrentRevocation: aliceCommitPoint,
		RevocationProducer:      bobPreimageProducer,
		RevocationStore:         shachain.NewRevocationStore(),
		LocalCommitment:         bobLocalCommit,
		RemoteCommitment:        bobRemoteCommit,
		Db:                      dbBob,
		Packager:                channeldb.NewChannelPackager(shortChanID),
	}

	aliceSigner := &input.MockSigner{Privkeys: aliceKeys}
	bobSigner := &input.MockSigner{Privkeys: bobKeys}

	// TODO(roasbeef): make mock version of pre-image store

	alicePool := NewSigPool(1, aliceSigner)
	channelAlice, err := NewLightningChannel(
		aliceSigner, aliceChannelState, alicePool,
	)
	if err != nil {
		return nil, nil, nil, err
	}
	alicePool.Start()

	obfuscator := createStateHintObfuscator(aliceChannelState)

	bobPool := NewSigPool(1, bobSigner)
	channelBob, err := NewLightningChannel(
		bobSigner, bobChannelState, bobPool,
	)
	if err != nil {
		return nil, nil, nil, err
	}
	bobPool.Start()

	err = SetStateNumHint(
		aliceCommitTx, 0, obfuscator,
	)
	if err != nil {
		return nil, nil, nil, err
	}
	err = SetStateNumHint(
		bobCommitTx, 0, obfuscator,
	)
	if err != nil {
		return nil, nil, nil, err
	}

	addr := &net.TCPAddr{
		IP:   net.ParseIP("127.0.0.1"),
		Port: 18556,
	}
	if err := channelAlice.channelState.SyncPending(addr, 101); err != nil {
		return nil, nil, nil, err
	}

	addr = &net.TCPAddr{
		IP:   net.ParseIP("127.0.0.1"),
		Port: 18555,
	}

	if err := channelBob.channelState.SyncPending(addr, 101); err != nil {
		return nil, nil, nil, err
	}

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

		alicePool.Stop()
		bobPool.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)
	if err != nil {
		return nil, nil, nil, err
	}

	return channelAlice, channelBob, cleanUpFunc, nil
}

// initRevocationWindows simulates a new channel being opened within the p2p
// network by populating the initial revocation windows of the passed
// commitment state machines.
func initRevocationWindows(chanA, chanB *LightningChannel) 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
}

// pubkeyFromHex parses a Bitcoin public key from a hex encoded string.
func pubkeyFromHex(keyHex string) (*btcec.PublicKey, error) {
	bytes, err := hex.DecodeString(keyHex)
	if err != nil {
		return nil, err
	}
	return btcec.ParsePubKey(bytes, btcec.S256())
}

// privkeyFromHex parses a Bitcoin private key from a hex encoded string.
func privkeyFromHex(keyHex string) (*btcec.PrivateKey, error) {
	bytes, err := hex.DecodeString(keyHex)
	if err != nil {
		return nil, err
	}
	key, _ := btcec.PrivKeyFromBytes(btcec.S256(), bytes)
	return key, nil

}

// blockFromHex parses a full Bitcoin block from a hex encoded string.
func blockFromHex(blockHex string) (*btcutil.Block, error) {
	bytes, err := hex.DecodeString(blockHex)
	if err != nil {
		return nil, err
	}
	return btcutil.NewBlockFromBytes(bytes)
}

// txFromHex parses a full Bitcoin transaction from a hex encoded string.
func txFromHex(txHex string) (*btcutil.Tx, error) {
	bytes, err := hex.DecodeString(txHex)
	if err != nil {
		return nil, err
	}
	return btcutil.NewTxFromBytes(bytes)
}

// 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(chanType channeldb.ChannelType, numHTLCs int) btcutil.Amount {
	const (
		htlcWeight = 172
		feePerKw   = btcutil.Amount(24/4) * 1000
	)
	return feePerKw *
		(btcutil.Amount(CommitWeight(chanType) +
			htlcWeight*int64(numHTLCs))) / 1000
}

// ForceStateTransition executes the necessary interaction between the two
// commitment state machines to transition to a new state locking in any
// pending updates. This method is useful when testing interactions between two
// live state machines.
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
}
