const Buffer = require('safe-buffer').Buffer
const bcrypto = require('./crypto')
const bscript = require('./script')
const bufferutils = require('./bufferutils')
const opcodes = require('bitcoin-ops')
const typeforce = require('typeforce')
const types = require('./types')
const varuint = require('varuint-bitcoin')

function varSliceSize (someScript) {
  const length = someScript.length

  return varuint.encodingLength(length) + length
}

function vectorSize (someVector) {
  const length = someVector.length

  return varuint.encodingLength(length) + someVector.reduce(function (sum, witness) {
    return sum + varSliceSize(witness)
  }, 0)
}

function Transaction () {
  this.version = 1
  this.locktime = 0
  this.ins = []
  this.outs = []
}

Transaction.DEFAULT_SEQUENCE = 0xffffffff
Transaction.SIGHASH_ALL = 0x01
Transaction.SIGHASH_NONE = 0x02
Transaction.SIGHASH_SINGLE = 0x03
Transaction.SIGHASH_ANYONECANPAY = 0x80
Transaction.ADVANCED_TRANSACTION_MARKER = 0x00
Transaction.ADVANCED_TRANSACTION_FLAG = 0x01

const EMPTY_SCRIPT = Buffer.allocUnsafe(0)
const EMPTY_WITNESS = []
const ZERO = Buffer.from('0000000000000000000000000000000000000000000000000000000000000000', 'hex')
const ONE = Buffer.from('0000000000000000000000000000000000000000000000000000000000000001', 'hex')
const VALUE_UINT64_MAX = Buffer.from('ffffffffffffffff', 'hex')
const BLANK_OUTPUT = {
  script: EMPTY_SCRIPT,
  valueBuffer: VALUE_UINT64_MAX
}

Transaction.fromBuffer = function (buffer, __noStrict) {
  let offset = 0
  function readSlice (n) {
    offset += n
    return buffer.slice(offset - n, offset)
  }

  function readUInt32 () {
    const i = buffer.readUInt32LE(offset)
    offset += 4
    return i
  }

  function readInt32 () {
    const i = buffer.readInt32LE(offset)
    offset += 4
    return i
  }

  function readUInt64 () {
    const i = bufferutils.readUInt64LE(buffer, offset)
    offset += 8
    return i
  }

  function readVarInt () {
    const vi = varuint.decode(buffer, offset)
    offset += varuint.decode.bytes
    return vi
  }

  function readVarSlice () {
    return readSlice(readVarInt())
  }

  function readVector () {
    const count = readVarInt()
    const vector = []
    for (var i = 0; i < count; i++) vector.push(readVarSlice())
    return vector
  }

  const tx = new Transaction()
  tx.version = readInt32()

  const marker = buffer.readUInt8(offset)
  const flag = buffer.readUInt8(offset + 1)

  let hasWitnesses = false
  if (marker === Transaction.ADVANCED_TRANSACTION_MARKER &&
      flag === Transaction.ADVANCED_TRANSACTION_FLAG) {
    offset += 2
    hasWitnesses = true
  }

  const vinLen = readVarInt()
  for (var i = 0; i < vinLen; ++i) {
    tx.ins.push({
      hash: readSlice(32),
      index: readUInt32(),
      script: readVarSlice(),
      sequence: readUInt32(),
      witness: EMPTY_WITNESS
    })
  }

  const voutLen = readVarInt()
  for (i = 0; i < voutLen; ++i) {
    tx.outs.push({
      value: readUInt64(),
      script: readVarSlice()
    })
  }

  if (hasWitnesses) {
    for (i = 0; i < vinLen; ++i) {
      tx.ins[i].witness = readVector()
    }

    // was this pointless?
    if (!tx.hasWitnesses()) throw new Error('Transaction has superfluous witness data')
  }

  tx.locktime = readUInt32()

  if (__noStrict) return tx
  if (offset !== buffer.length) throw new Error('Transaction has unexpected data')

  return tx
}

Transaction.fromHex = function (hex) {
  return Transaction.fromBuffer(Buffer.from(hex, 'hex'))
}

Transaction.isCoinbaseHash = function (buffer) {
  typeforce(types.Hash256bit, buffer)
  for (var i = 0; i < 32; ++i) {
    if (buffer[i] !== 0) return false
  }
  return true
}

Transaction.prototype.isCoinbase = function () {
  return this.ins.length === 1 && Transaction.isCoinbaseHash(this.ins[0].hash)
}

Transaction.prototype.addInput = function (hash, index, sequence, scriptSig) {
  typeforce(types.tuple(
    types.Hash256bit,
    types.UInt32,
    types.maybe(types.UInt32),
    types.maybe(types.Buffer)
  ), arguments)

  if (types.Null(sequence)) {
    sequence = Transaction.DEFAULT_SEQUENCE
  }

  // Add the input and return the input's index
  return (this.ins.push({
    hash: hash,
    index: index,
    script: scriptSig || EMPTY_SCRIPT,
    sequence: sequence,
    witness: EMPTY_WITNESS
  }) - 1)
}

Transaction.prototype.addOutput = function (scriptPubKey, value) {
  typeforce(types.tuple(types.Buffer, types.Satoshi), arguments)

  // Add the output and return the output's index
  return (this.outs.push({
    script: scriptPubKey,
    value: value
  }) - 1)
}

Transaction.prototype.hasWitnesses = function () {
  return this.ins.some(function (x) {
    return x.witness.length !== 0
  })
}

Transaction.prototype.weight = function () {
  const base = this.__byteLength(false)
  const total = this.__byteLength(true)
  return base * 3 + total
}

Transaction.prototype.virtualSize = function () {
  return Math.ceil(this.weight() / 4)
}

Transaction.prototype.byteLength = function () {
  return this.__byteLength(true)
}

Transaction.prototype.__byteLength = function (__allowWitness) {
  const hasWitnesses = __allowWitness && this.hasWitnesses()

  return (
    (hasWitnesses ? 10 : 8) +
    varuint.encodingLength(this.ins.length) +
    varuint.encodingLength(this.outs.length) +
    this.ins.reduce(function (sum, input) { return sum + 40 + varSliceSize(input.script) }, 0) +
    this.outs.reduce(function (sum, output) { return sum + 8 + varSliceSize(output.script) }, 0) +
    (hasWitnesses ? this.ins.reduce(function (sum, input) { return sum + vectorSize(input.witness) }, 0) : 0)
  )
}

Transaction.prototype.clone = function () {
  const newTx = new Transaction()
  newTx.version = this.version
  newTx.locktime = this.locktime

  newTx.ins = this.ins.map(function (txIn) {
    return {
      hash: txIn.hash,
      index: txIn.index,
      script: txIn.script,
      sequence: txIn.sequence,
      witness: txIn.witness
    }
  })

  newTx.outs = this.outs.map(function (txOut) {
    return {
      script: txOut.script,
      value: txOut.value
    }
  })

  return newTx
}

/**
 * Hash transaction for signing a specific input.
 *
 * Bitcoin uses a different hash for each signed transaction input.
 * This method copies the transaction, makes the necessary changes based on the
 * hashType, and then hashes the result.
 * This hash can then be used to sign the provided transaction input.
 */
Transaction.prototype.hashForSignature = function (inIndex, prevOutScript, hashType) {
  typeforce(types.tuple(types.UInt32, types.Buffer, /* types.UInt8 */ types.Number), arguments)

  // https://github.com/bitcoin/bitcoin/blob/master/src/test/sighash_tests.cpp#L29
  if (inIndex >= this.ins.length) return ONE

  // ignore OP_CODESEPARATOR
  const ourScript = bscript.compile(bscript.decompile(prevOutScript).filter(function (x) {
    return x !== opcodes.OP_CODESEPARATOR
  }))

  const txTmp = this.clone()

  // SIGHASH_NONE: ignore all outputs? (wildcard payee)
  if ((hashType & 0x1f) === Transaction.SIGHASH_NONE) {
    txTmp.outs = []

    // ignore sequence numbers (except at inIndex)
    txTmp.ins.forEach(function (input, i) {
      if (i === inIndex) return

      input.sequence = 0
    })

  // SIGHASH_SINGLE: ignore all outputs, except at the same index?
  } else if ((hashType & 0x1f) === Transaction.SIGHASH_SINGLE) {
    // https://github.com/bitcoin/bitcoin/blob/master/src/test/sighash_tests.cpp#L60
    if (inIndex >= this.outs.length) return ONE

    // truncate outputs after
    txTmp.outs.length = inIndex + 1

    // "blank" outputs before
    for (var i = 0; i < inIndex; i++) {
      txTmp.outs[i] = BLANK_OUTPUT
    }

    // ignore sequence numbers (except at inIndex)
    txTmp.ins.forEach(function (input, y) {
      if (y === inIndex) return

      input.sequence = 0
    })
  }

  // SIGHASH_ANYONECANPAY: ignore inputs entirely?
  if (hashType & Transaction.SIGHASH_ANYONECANPAY) {
    txTmp.ins = [txTmp.ins[inIndex]]
    txTmp.ins[0].script = ourScript

  // SIGHASH_ALL: only ignore input scripts
  } else {
    // "blank" others input scripts
    txTmp.ins.forEach(function (input) { input.script = EMPTY_SCRIPT })
    txTmp.ins[inIndex].script = ourScript
  }

  // serialize and hash
  const buffer = Buffer.allocUnsafe(txTmp.__byteLength(false) + 4)
  buffer.writeInt32LE(hashType, buffer.length - 4)
  txTmp.__toBuffer(buffer, 0, false)

  return bcrypto.hash256(buffer)
}

Transaction.prototype.hashForWitnessV0 = function (inIndex, prevOutScript, value, hashType) {
  typeforce(types.tuple(types.UInt32, types.Buffer, types.Satoshi, types.UInt32), arguments)

  let tbuffer, toffset
  function writeSlice (slice) { toffset += slice.copy(tbuffer, toffset) }
  function writeUInt32 (i) { toffset = tbuffer.writeUInt32LE(i, toffset) }
  function writeUInt64 (i) { toffset = bufferutils.writeUInt64LE(tbuffer, i, toffset) }
  function writeVarInt (i) {
    varuint.encode(i, tbuffer, toffset)
    toffset += varuint.encode.bytes
  }
  function writeVarSlice (slice) { writeVarInt(slice.length); writeSlice(slice) }

  let hashOutputs = ZERO
  let hashPrevouts = ZERO
  let hashSequence = ZERO

  if (!(hashType & Transaction.SIGHASH_ANYONECANPAY)) {
    tbuffer = Buffer.allocUnsafe(36 * this.ins.length)
    toffset = 0

    this.ins.forEach(function (txIn) {
      writeSlice(txIn.hash)
      writeUInt32(txIn.index)
    })

    hashPrevouts = bcrypto.hash256(tbuffer)
  }

  if (!(hashType & Transaction.SIGHASH_ANYONECANPAY) &&
       (hashType & 0x1f) !== Transaction.SIGHASH_SINGLE &&
       (hashType & 0x1f) !== Transaction.SIGHASH_NONE) {
    tbuffer = Buffer.allocUnsafe(4 * this.ins.length)
    toffset = 0

    this.ins.forEach(function (txIn) {
      writeUInt32(txIn.sequence)
    })

    hashSequence = bcrypto.hash256(tbuffer)
  }

  if ((hashType & 0x1f) !== Transaction.SIGHASH_SINGLE &&
      (hashType & 0x1f) !== Transaction.SIGHASH_NONE) {
    const txOutsSize = this.outs.reduce(function (sum, output) {
      return sum + 8 + varSliceSize(output.script)
    }, 0)

    tbuffer = Buffer.allocUnsafe(txOutsSize)
    toffset = 0

    this.outs.forEach(function (out) {
      writeUInt64(out.value)
      writeVarSlice(out.script)
    })

    hashOutputs = bcrypto.hash256(tbuffer)
  } else if ((hashType & 0x1f) === Transaction.SIGHASH_SINGLE && inIndex < this.outs.length) {
    const output = this.outs[inIndex]

    tbuffer = Buffer.allocUnsafe(8 + varSliceSize(output.script))
    toffset = 0
    writeUInt64(output.value)
    writeVarSlice(output.script)

    hashOutputs = bcrypto.hash256(tbuffer)
  }

  tbuffer = Buffer.allocUnsafe(156 + varSliceSize(prevOutScript))
  toffset = 0

  const input = this.ins[inIndex]
  writeUInt32(this.version)
  writeSlice(hashPrevouts)
  writeSlice(hashSequence)
  writeSlice(input.hash)
  writeUInt32(input.index)
  writeVarSlice(prevOutScript)
  writeUInt64(value)
  writeUInt32(input.sequence)
  writeSlice(hashOutputs)
  writeUInt32(this.locktime)
  writeUInt32(hashType)
  return bcrypto.hash256(tbuffer)
}

Transaction.prototype.getHash = function () {
  return bcrypto.hash256(this.__toBuffer(undefined, undefined, false))
}

Transaction.prototype.getId = function () {
  // transaction hash's are displayed in reverse order
  return this.getHash().reverse().toString('hex')
}

Transaction.prototype.toBuffer = function (buffer, initialOffset) {
  return this.__toBuffer(buffer, initialOffset, true)
}

Transaction.prototype.__toBuffer = function (buffer, initialOffset, __allowWitness) {
  if (!buffer) buffer = Buffer.allocUnsafe(this.__byteLength(__allowWitness))

  let offset = initialOffset || 0
  function writeSlice (slice) { offset += slice.copy(buffer, offset) }
  function writeUInt8 (i) { offset = buffer.writeUInt8(i, offset) }
  function writeUInt32 (i) { offset = buffer.writeUInt32LE(i, offset) }
  function writeInt32 (i) { offset = buffer.writeInt32LE(i, offset) }
  function writeUInt64 (i) { offset = bufferutils.writeUInt64LE(buffer, i, offset) }
  function writeVarInt (i) {
    varuint.encode(i, buffer, offset)
    offset += varuint.encode.bytes
  }
  function writeVarSlice (slice) { writeVarInt(slice.length); writeSlice(slice) }
  function writeVector (vector) { writeVarInt(vector.length); vector.forEach(writeVarSlice) }

  writeInt32(this.version)

  const hasWitnesses = __allowWitness && this.hasWitnesses()

  if (hasWitnesses) {
    writeUInt8(Transaction.ADVANCED_TRANSACTION_MARKER)
    writeUInt8(Transaction.ADVANCED_TRANSACTION_FLAG)
  }

  writeVarInt(this.ins.length)

  this.ins.forEach(function (txIn) {
    writeSlice(txIn.hash)
    writeUInt32(txIn.index)
    writeVarSlice(txIn.script)
    writeUInt32(txIn.sequence)
  })

  writeVarInt(this.outs.length)
  this.outs.forEach(function (txOut) {
    if (!txOut.valueBuffer) {
      writeUInt64(txOut.value)
    } else {
      writeSlice(txOut.valueBuffer)
    }

    writeVarSlice(txOut.script)
  })

  if (hasWitnesses) {
    this.ins.forEach(function (input) {
      writeVector(input.witness)
    })
  }

  writeUInt32(this.locktime)

  // avoid slicing unless necessary
  if (initialOffset !== undefined) return buffer.slice(initialOffset, offset)
  return buffer
}

Transaction.prototype.toHex = function () {
  return this.toBuffer().toString('hex')
}

Transaction.prototype.setInputScript = function (index, scriptSig) {
  typeforce(types.tuple(types.Number, types.Buffer), arguments)

  this.ins[index].script = scriptSig
}

Transaction.prototype.setWitness = function (index, witness) {
  typeforce(types.tuple(types.Number, [types.Buffer]), arguments)

  this.ins[index].witness = witness
}

module.exports = Transaction