// Copyright 2011 Mark Cavage <mcavage@gmail.com> All rights reserved.

const assert = require('assert')
const ASN1 = require('./types')
const errors = require('./errors')

// --- Globals

const newInvalidAsn1Error = errors.newInvalidAsn1Error

const DEFAULT_OPTS = {
  size: 1024,
  growthFactor: 8
}

// --- Helpers

function merge (from, to) {
  assert.ok(from)
  assert.equal(typeof (from), 'object')
  assert.ok(to)
  assert.equal(typeof (to), 'object')

  const keys = Object.getOwnPropertyNames(from)
  keys.forEach(function (key) {
    if (to[key]) { return }

    const value = Object.getOwnPropertyDescriptor(from, key)
    Object.defineProperty(to, key, value)
  })

  return to
}

// --- API

function Writer (options) {
  options = merge(DEFAULT_OPTS, options || {})

  this._buf = Buffer.alloc(options.size || 1024)
  this._size = this._buf.length
  this._offset = 0
  this._options = options

  // A list of offsets in the buffer where we need to insert
  // sequence tag/len pairs.
  this._seq = []
}

Object.defineProperty(Writer.prototype, Symbol.toStringTag, { value: 'BerWriter' })

Object.defineProperty(Writer.prototype, 'buffer', {
  get: function () {
    if (this._seq.length) { throw newInvalidAsn1Error(this._seq.length + ' unended sequence(s)') }

    return (this._buf.slice(0, this._offset))
  }
})

/**
 * Append a raw buffer to the current writer instance. No validation to
 * determine if the buffer represents a valid BER encoding is performed.
 *
 * @param {Buffer} buffer The buffer to append. If this is not a valid BER
 * sequence of data, it will invalidate the BER represented by the `BerWriter`.
 *
 * @throws If the input is not an instance of Buffer.
 */
Writer.prototype.appendBuffer = function appendBuffer (buffer) {
  if (Buffer.isBuffer(buffer) === false) {
    throw Error('buffer must be an instance of Buffer')
  }
  for (const b of buffer.values()) {
    this.writeByte(b)
  }
}

Writer.prototype.writeByte = function (b) {
  if (typeof (b) !== 'number') { throw new TypeError('argument must be a Number') }

  this._ensure(1)
  this._buf[this._offset++] = b
}

Writer.prototype.writeInt = function (i, tag) {
  if (typeof (i) !== 'number') { throw new TypeError('argument must be a Number') }
  if (typeof (tag) !== 'number') { tag = ASN1.Integer }

  let sz = 4

  while ((((i & 0xff800000) === 0) || ((i & 0xff800000) === 0xff800000 >> 0)) &&
        (sz > 1)) {
    sz--
    i <<= 8
  }

  if (sz > 4) { throw newInvalidAsn1Error('BER ints cannot be > 0xffffffff') }

  this._ensure(2 + sz)
  this._buf[this._offset++] = tag
  this._buf[this._offset++] = sz

  while (sz-- > 0) {
    this._buf[this._offset++] = ((i & 0xff000000) >>> 24)
    i <<= 8
  }
}

Writer.prototype.writeNull = function () {
  this.writeByte(ASN1.Null)
  this.writeByte(0x00)
}

Writer.prototype.writeEnumeration = function (i, tag) {
  if (typeof (i) !== 'number') { throw new TypeError('argument must be a Number') }
  if (typeof (tag) !== 'number') { tag = ASN1.Enumeration }

  return this.writeInt(i, tag)
}

Writer.prototype.writeBoolean = function (b, tag) {
  if (typeof (b) !== 'boolean') { throw new TypeError('argument must be a Boolean') }
  if (typeof (tag) !== 'number') { tag = ASN1.Boolean }

  this._ensure(3)
  this._buf[this._offset++] = tag
  this._buf[this._offset++] = 0x01
  this._buf[this._offset++] = b ? 0xff : 0x00
}

Writer.prototype.writeString = function (s, tag) {
  if (typeof (s) !== 'string') { throw new TypeError('argument must be a string (was: ' + typeof (s) + ')') }
  if (typeof (tag) !== 'number') { tag = ASN1.OctetString }

  const len = Buffer.byteLength(s)
  this.writeByte(tag)
  this.writeLength(len)
  if (len) {
    this._ensure(len)
    this._buf.write(s, this._offset)
    this._offset += len
  }
}

Writer.prototype.writeBuffer = function (buf, tag) {
  if (typeof (tag) !== 'number') { throw new TypeError('tag must be a number') }
  if (!Buffer.isBuffer(buf)) { throw new TypeError('argument must be a buffer') }

  this.writeByte(tag)
  this.writeLength(buf.length)
  this._ensure(buf.length)
  buf.copy(this._buf, this._offset, 0, buf.length)
  this._offset += buf.length
}

Writer.prototype.writeStringArray = function (strings) {
  if (Array.isArray(strings) === false) { throw new TypeError('argument must be an Array[String]') }

  const self = this
  strings.forEach(function (s) {
    self.writeString(s)
  })
}

// This is really to solve DER cases, but whatever for now
Writer.prototype.writeOID = function (s, tag) {
  if (typeof (s) !== 'string') { throw new TypeError('argument must be a string') }
  if (typeof (tag) !== 'number') { tag = ASN1.OID }

  if (!/^([0-9]+\.){3,}[0-9]+$/.test(s)) { throw new Error('argument is not a valid OID string') }

  function encodeOctet (bytes, octet) {
    if (octet < 128) {
      bytes.push(octet)
    } else if (octet < 16384) {
      bytes.push((octet >>> 7) | 0x80)
      bytes.push(octet & 0x7F)
    } else if (octet < 2097152) {
      bytes.push((octet >>> 14) | 0x80)
      bytes.push(((octet >>> 7) | 0x80) & 0xFF)
      bytes.push(octet & 0x7F)
    } else if (octet < 268435456) {
      bytes.push((octet >>> 21) | 0x80)
      bytes.push(((octet >>> 14) | 0x80) & 0xFF)
      bytes.push(((octet >>> 7) | 0x80) & 0xFF)
      bytes.push(octet & 0x7F)
    } else {
      bytes.push(((octet >>> 28) | 0x80) & 0xFF)
      bytes.push(((octet >>> 21) | 0x80) & 0xFF)
      bytes.push(((octet >>> 14) | 0x80) & 0xFF)
      bytes.push(((octet >>> 7) | 0x80) & 0xFF)
      bytes.push(octet & 0x7F)
    }
  }

  const tmp = s.split('.')
  const bytes = []
  bytes.push(parseInt(tmp[0], 10) * 40 + parseInt(tmp[1], 10))
  tmp.slice(2).forEach(function (b) {
    encodeOctet(bytes, parseInt(b, 10))
  })

  const self = this
  this._ensure(2 + bytes.length)
  this.writeByte(tag)
  this.writeLength(bytes.length)
  bytes.forEach(function (b) {
    self.writeByte(b)
  })
}

Writer.prototype.writeLength = function (len) {
  if (typeof (len) !== 'number') { throw new TypeError('argument must be a Number') }

  this._ensure(4)

  if (len <= 0x7f) {
    this._buf[this._offset++] = len
  } else if (len <= 0xff) {
    this._buf[this._offset++] = 0x81
    this._buf[this._offset++] = len
  } else if (len <= 0xffff) {
    this._buf[this._offset++] = 0x82
    this._buf[this._offset++] = len >> 8
    this._buf[this._offset++] = len
  } else if (len <= 0xffffff) {
    this._buf[this._offset++] = 0x83
    this._buf[this._offset++] = len >> 16
    this._buf[this._offset++] = len >> 8
    this._buf[this._offset++] = len
  } else {
    throw newInvalidAsn1Error('Length too long (> 4 bytes)')
  }
}

Writer.prototype.startSequence = function (tag) {
  if (typeof (tag) !== 'number') { tag = ASN1.Sequence | ASN1.Constructor }

  this.writeByte(tag)
  this._seq.push(this._offset)
  this._ensure(3)
  this._offset += 3
}

Writer.prototype.endSequence = function () {
  const seq = this._seq.pop()
  const start = seq + 3
  const len = this._offset - start

  if (len <= 0x7f) {
    this._shift(start, len, -2)
    this._buf[seq] = len
  } else if (len <= 0xff) {
    this._shift(start, len, -1)
    this._buf[seq] = 0x81
    this._buf[seq + 1] = len
  } else if (len <= 0xffff) {
    this._buf[seq] = 0x82
    this._buf[seq + 1] = len >> 8
    this._buf[seq + 2] = len
  } else if (len <= 0xffffff) {
    this._shift(start, len, 1)
    this._buf[seq] = 0x83
    this._buf[seq + 1] = len >> 16
    this._buf[seq + 2] = len >> 8
    this._buf[seq + 3] = len
  } else {
    throw newInvalidAsn1Error('Sequence too long')
  }
}

Writer.prototype._shift = function (start, len, shift) {
  assert.ok(start !== undefined)
  assert.ok(len !== undefined)
  assert.ok(shift)

  this._buf.copy(this._buf, start + shift, start, start + len)
  this._offset += shift
}

Writer.prototype._ensure = function (len) {
  assert.ok(len)

  if (this._size - this._offset < len) {
    let sz = this._size * this._options.growthFactor
    if (sz - this._offset < len) { sz += len }

    const buf = Buffer.alloc(sz)

    this._buf.copy(buf, 0, 0, this._offset)
    this._buf = buf
    this._size = sz
  }
}

// --- Exported API

module.exports = Writer