const { inherits } = require('util')

const { Reporter } = require('../base/reporter')

function DecoderBuffer (base, options) {
  Reporter.call(this, options)
  if (!Buffer.isBuffer(base)) {
    this.error('Input not Buffer')
    return
  }

  this.base = base
  this.offset = 0
  this.length = base.length
}
inherits(DecoderBuffer, Reporter)

DecoderBuffer.isDecoderBuffer = function isDecoderBuffer (data) {
  if (data instanceof DecoderBuffer) {
    return true
  }

  // Or accept compatible API
  const isCompatible = typeof data === 'object' &&
    Buffer.isBuffer(data.base) &&
    data.constructor.name === 'DecoderBuffer' &&
    typeof data.offset === 'number' &&
    typeof data.length === 'number' &&
    typeof data.save === 'function' &&
    typeof data.restore === 'function' &&
    typeof data.isEmpty === 'function' &&
    typeof data.readUInt8 === 'function' &&
    typeof data.skip === 'function' &&
    typeof data.raw === 'function'

  return isCompatible
}

DecoderBuffer.prototype.save = function save () {
  return { offset: this.offset, reporter: Reporter.prototype.save.call(this) }
}

DecoderBuffer.prototype.restore = function restore (save) {
  // Return skipped data
  const res = new DecoderBuffer(this.base)
  res.offset = save.offset
  res.length = this.offset

  this.offset = save.offset
  Reporter.prototype.restore.call(this, save.reporter)

  return res
}

DecoderBuffer.prototype.isEmpty = function isEmpty () {
  return this.offset === this.length
}

DecoderBuffer.prototype.readUInt8 = function readUInt8 (fail) {
  if (this.offset + 1 <= this.length) { return this.base.readUInt8(this.offset++, true) } else { return this.error(fail || 'DecoderBuffer overrun') }
}

DecoderBuffer.prototype.skip = function skip (bytes, fail) {
  if (!(this.offset + bytes <= this.length)) { return this.error(fail || 'DecoderBuffer overrun') }

  const res = new DecoderBuffer(this.base)

  // Share reporter state
  res._reporterState = this._reporterState

  res.offset = this.offset
  res.length = this.offset + bytes
  this.offset += bytes
  return res
}

DecoderBuffer.prototype.raw = function raw (save) {
  return this.base.slice(save ? save.offset : this.offset, this.length)
}

function EncoderBuffer (value, reporter) {
  if (Array.isArray(value)) {
    this.length = 0
    this.value = value.map(function (item) {
      if (!EncoderBuffer.isEncoderBuffer(item)) { item = new EncoderBuffer(item, reporter) }
      this.length += item.length
      return item
    }, this)
  } else if (typeof value === 'number') {
    if (!(value >= 0 && value <= 0xff)) { return reporter.error('non-byte EncoderBuffer value') }
    this.value = value
    this.length = 1
  } else if (typeof value === 'string') {
    this.value = value
    this.length = Buffer.byteLength(value)
  } else if (Buffer.isBuffer(value)) {
    this.value = value
    this.length = value.length
  } else {
    return reporter.error(`Unsupported type: ${typeof value}`)
  }
}

EncoderBuffer.isEncoderBuffer = function isEncoderBuffer (data) {
  if (data instanceof EncoderBuffer) {
    return true
  }

  // Or accept compatible API
  const isCompatible = typeof data === 'object' &&
    data.constructor.name === 'EncoderBuffer' &&
    typeof data.length === 'number' &&
    typeof data.join === 'function'

  return isCompatible
}

EncoderBuffer.prototype.join = function join (out, offset) {
  if (!out) { out = Buffer.alloc(this.length) }
  if (!offset) { offset = 0 }

  if (this.length === 0) { return out }

  if (Array.isArray(this.value)) {
    this.value.forEach(function (item) {
      item.join(out, offset)
      offset += item.length
    })
  } else {
    if (typeof this.value === 'number') { out[offset] = this.value } else if (typeof this.value === 'string') { out.write(this.value, offset) } else if (Buffer.isBuffer(this.value)) { this.value.copy(out, offset) }
    offset += this.length
  }

  return out
}

module.exports = {
  DecoderBuffer,
  EncoderBuffer
}