let ecdsa = require('./ecdsa')
let randomBytes = require('randombytes')
let typeforce = require('typeforce')
let types = require('./types')
let wif = require('wif')

let NETWORKS = require('./networks')
let BigInteger = require('bigi')

let ecurve = require('ecurve')
let secp256k1 = ecdsa.__curve

function ECPair (d, Q, options) {
  if (options) {
    typeforce({
      compressed: types.maybe(types.Boolean),
      network: types.maybe(types.Network)
    }, options)
  }

  options = options || {}

  if (d) {
    if (d.signum() <= 0) throw new Error('Private key must be greater than 0')
    if (d.compareTo(secp256k1.n) >= 0) throw new Error('Private key must be less than the curve order')
    if (Q) throw new TypeError('Unexpected publicKey parameter')

    this.d = d
  } else {
    typeforce(types.ECPoint, Q)

    this.__Q = Q
  }

  this.compressed = options.compressed === undefined ? true : options.compressed
  this.network = options.network || NETWORKS.bitcoin
}

Object.defineProperty(ECPair.prototype, 'Q', {
  get: function () {
    if (!this.__Q && this.d) {
      this.__Q = secp256k1.G.multiply(this.d)
    }

    return this.__Q
  }
})

ECPair.fromPublicKeyBuffer = function (buffer, network) {
  var Q = ecurve.Point.decodeFrom(secp256k1, buffer)

  return new ECPair(null, Q, {
    compressed: Q.compressed,
    network: network
  })
}

ECPair.fromWIF = function (string, network) {
  var decoded = wif.decode(string)
  var version = decoded.version

  // list of networks?
  if (types.Array(network)) {
    network = network.filter(function (x) {
      return version === x.wif
    }).pop()

    if (!network) throw new Error('Unknown network version')

  // otherwise, assume a network object (or default to bitcoin)
  } else {
    network = network || NETWORKS.bitcoin

    if (version !== network.wif) throw new Error('Invalid network version')
  }

  var d = BigInteger.fromBuffer(decoded.privateKey)

  return new ECPair(d, null, {
    compressed: decoded.compressed,
    network: network
  })
}

ECPair.makeRandom = function (options) {
  options = options || {}

  var rng = options.rng || randomBytes

  var d
  do {
    var buffer = rng(32)
    typeforce(types.Buffer256bit, buffer)

    d = BigInteger.fromBuffer(buffer)
  } while (d.signum() <= 0 || d.compareTo(secp256k1.n) >= 0)

  return new ECPair(d, null, options)
}

ECPair.prototype.getNetwork = function () {
  return this.network
}

ECPair.prototype.getPublicKeyBuffer = function () {
  return this.Q.getEncoded(this.compressed)
}

ECPair.prototype.sign = function (hash) {
  if (!this.d) throw new Error('Missing private key')

  let signature = ecdsa.sign(hash, this.d)
  return Buffer.concat([signature.r.toBuffer(32), signature.s.toBuffer(32)], 64)
}

ECPair.prototype.toWIF = function () {
  if (!this.d) throw new Error('Missing private key')

  return wif.encode(this.network.wif, this.d.toBuffer(32), this.compressed)
}

ECPair.prototype.verify = function (hash, signature) {
  signature = {
    r: BigInteger.fromBuffer(signature.slice(0, 32)),
    s: BigInteger.fromBuffer(signature.slice(32, 64))
  }

  return ecdsa.verify(hash, signature, this.Q)
}

module.exports = ECPair