/* global BigInt */
const { inherits } = require('util')

const Node = require('../base/node')
const der = require('../constants/der')

function DEREncoder (entity) {
  this.enc = 'der'
  this.name = entity.name
  this.entity = entity

  // Construct base tree
  this.tree = new DERNode()
  this.tree._init(entity.body)
}

DEREncoder.prototype.encode = function encode (data, reporter) {
  return this.tree._encode(data, reporter).join()
}

// Tree methods

function DERNode (parent) {
  Node.call(this, 'der', parent)
}
inherits(DERNode, Node)

DERNode.prototype._encodeComposite = function encodeComposite (tag,
  primitive,
  cls,
  content) {
  const encodedTag = encodeTag(tag, primitive, cls, this.reporter)

  // Short form
  if (content.length < 0x80) {
    const header = Buffer.alloc(2)
    header[0] = encodedTag
    header[1] = content.length
    return this._createEncoderBuffer([header, content])
  }

  // Long form
  // Count octets required to store length
  let lenOctets = 1
  for (let i = content.length; i >= 0x100; i >>= 8) { lenOctets++ }

  const header = Buffer.alloc(1 + 1 + lenOctets)
  header[0] = encodedTag
  header[1] = 0x80 | lenOctets

  for (let i = 1 + lenOctets, j = content.length; j > 0; i--, j >>= 8) { header[i] = j & 0xff }

  return this._createEncoderBuffer([header, content])
}

DERNode.prototype._encodeStr = function encodeStr (str, tag) {
  if (tag === 'bitstr') {
    return this._createEncoderBuffer([str.unused | 0, str.data])
  } else if (tag === 'bmpstr') {
    const buf = Buffer.alloc(str.length * 2)
    for (let i = 0; i < str.length; i++) {
      buf.writeUInt16BE(str.charCodeAt(i), i * 2)
    }
    return this._createEncoderBuffer(buf)
  } else if (tag === 'numstr') {
    if (!this._isNumstr(str)) {
      return this.reporter.error('Encoding of string type: numstr supports only digits and space')
    }
    return this._createEncoderBuffer(str)
  } else if (tag === 'printstr') {
    if (!this._isPrintstr(str)) {
      return this.reporter.error('Encoding of string type: printstr supports only latin upper and lower case letters, digits, space, apostrophe, left and rigth parenthesis, plus sign, comma, hyphen, dot, slash, colon, equal sign, question mark')
    }
    return this._createEncoderBuffer(str)
  } else if (/str$/.test(tag)) {
    return this._createEncoderBuffer(str)
  } else if (tag === 'objDesc') {
    return this._createEncoderBuffer(str)
  } else {
    return this.reporter.error(`Encoding of string type: ${tag} unsupported`)
  }
}

DERNode.prototype._encodeObjid = function encodeObjid (id, values, relative) {
  if (typeof id === 'string') {
    if (!values) { return this.reporter.error('string objid given, but no values map found') }
    if (!Object.prototype.hasOwnProperty.call(values, id)) { return this.reporter.error('objid not found in values map') }
    id = values[id].split(/[\s.]+/g)
    for (let i = 0; i < id.length; i++) { id[i] |= 0 }
  } else if (Array.isArray(id)) {
    id = id.slice()
    for (let i = 0; i < id.length; i++) { id[i] |= 0 }
  }

  if (!Array.isArray(id)) {
    return this.reporter.error(`objid() should be either array or string, got: ${JSON.stringify(id)}`)
  }

  if (!relative) {
    if (id[1] >= 40) { return this.reporter.error('Second objid identifier OOB') }
    id.splice(0, 2, id[0] * 40 + id[1])
  }

  // Count number of octets
  let size = 0
  for (let i = 0; i < id.length; i++) {
    let ident = id[i]
    for (size++; ident >= 0x80; ident >>= 7) { size++ }
  }

  const objid = Buffer.alloc(size)
  let offset = objid.length - 1
  for (let i = id.length - 1; i >= 0; i--) {
    let ident = id[i]
    objid[offset--] = ident & 0x7f
    while ((ident >>= 7) > 0) { objid[offset--] = 0x80 | (ident & 0x7f) }
  }

  return this._createEncoderBuffer(objid)
}

function two (num) {
  if (num < 10) { return `0${num}` } else { return num }
}

DERNode.prototype._encodeTime = function encodeTime (time, tag) {
  let str
  const date = new Date(time)

  if (tag === 'gentime') {
    str = [
      two(date.getUTCFullYear()),
      two(date.getUTCMonth() + 1),
      two(date.getUTCDate()),
      two(date.getUTCHours()),
      two(date.getUTCMinutes()),
      two(date.getUTCSeconds()),
      'Z'
    ].join('')
  } else if (tag === 'utctime') {
    str = [
      two(date.getUTCFullYear() % 100),
      two(date.getUTCMonth() + 1),
      two(date.getUTCDate()),
      two(date.getUTCHours()),
      two(date.getUTCMinutes()),
      two(date.getUTCSeconds()),
      'Z'
    ].join('')
  } else {
    this.reporter.error(`Encoding ${tag} time is not supported yet`)
  }

  return this._encodeStr(str, 'octstr')
}

DERNode.prototype._encodeNull = function encodeNull () {
  return this._createEncoderBuffer('')
}

function bnToBuf (bn) {
  var hex = BigInt(bn).toString(16)
  if (hex.length % 2) { hex = '0' + hex }

  var len = hex.length / 2
  var u8 = new Uint8Array(len)

  var i = 0
  var j = 0
  while (i < len) {
    u8[i] = parseInt(hex.slice(j, j + 2), 16)
    i += 1
    j += 2
  }

  return u8
}

DERNode.prototype._encodeInt = function encodeInt (num, values) {
  if (typeof num === 'string') {
    if (!values) { return this.reporter.error('String int or enum given, but no values map') }
    if (!Object.prototype.hasOwnProperty.call(values, num)) {
      return this.reporter.error(`Values map doesn't contain: ${JSON.stringify(num)}`)
    }
    num = values[num]
  }

  if (typeof num === 'bigint') {
    const numArray = [...bnToBuf(num)]
    if (numArray[0] & 0x80) {
      numArray.unshift(0)
    }
    num = Buffer.from(numArray)
  }

  if (Buffer.isBuffer(num)) {
    let size = num.length
    if (num.length === 0) { size++ }

    const out = Buffer.alloc(size)
    num.copy(out)
    if (num.length === 0) { out[0] = 0 }
    return this._createEncoderBuffer(out)
  }

  if (num < 0x80) { return this._createEncoderBuffer(num) }

  if (num < 0x100) { return this._createEncoderBuffer([0, num]) }

  let size = 1
  for (let i = num; i >= 0x100; i >>= 8) { size++ }

  const out = new Array(size)
  for (let i = out.length - 1; i >= 0; i--) {
    out[i] = num & 0xff
    num >>= 8
  }
  if (out[0] & 0x80) {
    out.unshift(0)
  }

  return this._createEncoderBuffer(Buffer.from(out))
}

DERNode.prototype._encodeBool = function encodeBool (value) {
  return this._createEncoderBuffer(value ? 0xff : 0)
}

DERNode.prototype._use = function use (entity, obj) {
  if (typeof entity === 'function') { entity = entity(obj) }
  return entity._getEncoder('der').tree
}

DERNode.prototype._skipDefault = function skipDefault (dataBuffer, reporter, parent) {
  const state = this._baseState
  let i
  if (state.default === null) { return false }

  const data = dataBuffer.join()
  if (state.defaultBuffer === undefined) { state.defaultBuffer = this._encodeValue(state.default, reporter, parent).join() }

  if (data.length !== state.defaultBuffer.length) { return false }

  for (i = 0; i < data.length; i++) {
    if (data[i] !== state.defaultBuffer[i]) { return false }
  }

  return true
}

// Utility methods

function encodeTag (tag, primitive, cls, reporter) {
  let res

  if (tag === 'seqof') { tag = 'seq' } else if (tag === 'setof') { tag = 'set' }

  if (Object.prototype.hasOwnProperty.call(der.tagByName, tag)) { res = der.tagByName[tag] } else if (typeof tag === 'number' && (tag | 0) === tag) { res = tag } else { return reporter.error(`Unknown tag: ${tag}`) }

  if (res >= 0x1f) { return reporter.error('Multi-octet tag encoding unsupported') }

  if (!primitive) { res |= 0x20 }

  res |= (der.tagClassByName[cls || 'universal'] << 6)

  return res
}

module.exports = DEREncoder