export function PCMPlayer(option) {
  this.init(option)
}

PCMPlayer.prototype.init = function(option) {
  var defaults = {
    encoding: "16bitInt",
    channels: 1,
    sampleRate: 8000,
    flushingTime: 1000
  }
  this.option = Object.assign({}, defaults, option)
  this.samples = new Float32Array()
  this.flush = this.flush.bind(this)
  this.interval = setInterval(this.flush, this.option.flushingTime)
  this.maxValue = this.getMaxValue()
  this.typedArray = this.getTypedArray()
  this.createContext()
}

PCMPlayer.prototype.getMaxValue = function() {
  var encodings = {
    "8bitInt": 128,
    "16bitInt": 32768,
    "32bitInt": 2147483648,
    "32bitFloat": 1
  }

  return encodings[this.option.encoding] ? encodings[this.option.encoding] : encodings["16bitInt"]
}

PCMPlayer.prototype.getTypedArray = function() {
  var typedArrays = {
    "8bitInt": Int8Array,
    "16bitInt": Int16Array,
    "32bitInt": Int32Array,
    "32bitFloat": Float32Array
  }

  return typedArrays[this.option.encoding] ? typedArrays[this.option.encoding] : typedArrays["16bitInt"]
}

PCMPlayer.prototype.createContext = function() {
  this.audioCtx = new (window.AudioContext || window.webkitAudioContext)()
  this.gainNode = this.audioCtx.createGain()
  this.gainNode.gain.value = 1
  this.gainNode.connect(this.audioCtx.destination)
  this.startTime = this.audioCtx.currentTime
}

PCMPlayer.prototype.isTypedArray = function(data) {
  return data.byteLength && data.buffer && data.buffer.constructor == ArrayBuffer
}

PCMPlayer.prototype.feed = function(data) {
  if (!this.isTypedArray(data)) return
  data = this.getFormatedValue(data)
  var tmp = new Float32Array(this.samples.length + data.length)
  tmp.set(this.samples, 0)
  tmp.set(data, this.samples.length)
  this.samples = tmp
}

PCMPlayer.prototype.getFormatedValue = function(data) {
  var data = new this.typedArray(data.buffer),
    float32 = new Float32Array(data.length),
    i

  for (i = 0; i < data.length; i++) {
    float32[i] = data[i] / this.maxValue
  }
  return float32
}

PCMPlayer.prototype.volume = function(volume) {
  this.gainNode.gain.value = volume
}

PCMPlayer.prototype.destroy = function() {
  if (this.interval) {
    clearInterval(this.interval)
  }
  this.samples = null
  this.audioCtx.close()
  this.audioCtx = null
}

PCMPlayer.prototype.flush = function() {
  if (!this.samples.length) return
  var bufferSource = this.audioCtx.createBufferSource(),
    length = this.samples.length / this.option.channels,
    audioBuffer = this.audioCtx.createBuffer(this.option.channels, length, this.option.sampleRate),
    audioData,
    channel,
    offset,
    i,
    decrement

  for (channel = 0; channel < this.option.channels; channel++) {
    audioData = audioBuffer.getChannelData(channel)
    offset = channel
    decrement = 50
    for (i = 0; i < length; i++) {
      audioData[i] = this.samples[offset]
      /* fadein */
      if (i < 50) {
        audioData[i] = (audioData[i] * i) / 50
      }
      /* fadeout*/
      if (i >= length - 51) {
        audioData[i] = (audioData[i] * decrement--) / 50
      }
      offset += this.option.channels
    }
  }

  if (this.startTime < this.audioCtx.currentTime) {
    this.startTime = this.audioCtx.currentTime
  }
  //console.log('start vs current '+this.startTime+' vs '+this.audioCtx.currentTime+' duration: '+audioBuffer.duration);
  bufferSource.buffer = audioBuffer
  bufferSource.connect(this.gainNode)
  bufferSource.start(this.startTime)
  this.startTime += audioBuffer.duration
  this.samples = new Float32Array()
}

PCMPlayer.prototype.getTimestamp = function() {
  if (this.audioCtx) {
    return this.audioCtx.currentTime
  } else {
    return 0
  }
}

PCMPlayer.prototype.play = function(data) {
  if (!this.isTypedArray(data)) {
    return
  }

  data = this.getFormatedValue(data)
  if (!data.length) {
    return
  }

  var bufferSource = this.audioCtx.createBufferSource(),
    length = data.length / this.option.channels,
    audioBuffer = this.audioCtx.createBuffer(this.option.channels, length, this.option.sampleRate),
    audioData,
    channel,
    offset,
    i,
    decrement

  for (channel = 0; channel < this.option.channels; channel++) {
    audioData = audioBuffer.getChannelData(channel)
    offset = channel
    decrement = 50
    for (i = 0; i < length; i++) {
      audioData[i] = data[offset]
      /* fadein */
      if (i < 50) {
        audioData[i] = (audioData[i] * i) / 50
      }
      /* fadeout*/
      if (i >= length - 51) {
        audioData[i] = (audioData[i] * decrement--) / 50
      }
      offset += this.option.channels
    }
  }

  if (this.startTime < this.audioCtx.currentTime) {
    this.startTime = this.audioCtx.currentTime
  }
  //console.log('start vs current '+this.startTime+' vs '+this.audioCtx.currentTime+' duration: '+audioBuffer.duration);
  bufferSource.buffer = audioBuffer
  bufferSource.connect(this.gainNode)
  bufferSource.start(this.startTime)
  this.startTime += audioBuffer.duration
}

PCMPlayer.prototype.pause = function() {
  if (this.audioCtx.state === "running") {
    this.audioCtx.suspend()
  }
}

PCMPlayer.prototype.resume = function() {
  if (this.audioCtx.state === "suspended") {
    this.audioCtx.resume()
  }
}