/* Recorder.js worker — https://github.com/mattdiamond/Recorderjs */
var recLength = 0,
  recBuffers = [],
  sampleRate,
  numChannels;

this.onmessage = function(e) {
  switch (e.data.command) {
    case 'init':    init(e.data.config);    break;
    case 'record':  record(e.data.buffer);  break;
    case 'exportWAV': exportWAV(e.data.type); break;
    case 'getBuffer': getBuffer();           break;
    case 'clear':   clear();                break;
  }
};

function init(config) {
  sampleRate = config.sampleRate;
  numChannels = config.numChannels;
  initBuffers();
}

function record(inputBuffer) {
  for (var channel = 0; channel < numChannels; channel++) {
    recBuffers[channel].push(inputBuffer[channel]);
  }
  recLength += inputBuffer[0].length;
}

function exportWAV(type) {
  var buffers = [];
  for (var channel = 0; channel < numChannels; channel++) {
    buffers.push(mergeBuffers(recBuffers[channel], recLength));
  }
  var interleaved = numChannels === 2
    ? interleave(buffers[0], buffers[1])
    : buffers[0];
  var dataview = encodeWAV(interleaved);
  var audioBlob = new Blob([dataview], { type: type });
  this.postMessage({ command: 'exportWAV', data: audioBlob });
}

function getBuffer() {
  var buffers = [];
  for (var channel = 0; channel < numChannels; channel++) {
    buffers.push(mergeBuffers(recBuffers[channel], recLength));
  }
  this.postMessage({ command: 'getBuffer', data: buffers });
}

function clear() {
  recLength = 0;
  recBuffers = [];
  initBuffers();
}

function initBuffers() {
  for (var channel = 0; channel < numChannels; channel++) {
    recBuffers[channel] = [];
  }
}

function mergeBuffers(recBuffers, recLength) {
  var result = new Float32Array(recLength);
  var offset = 0;
  for (var i = 0; i < recBuffers.length; i++) {
    result.set(recBuffers[i], offset);
    offset += recBuffers[i].length;
  }
  return result;
}

function interleave(inputL, inputR) {
  var length = inputL.length + inputR.length;
  var result = new Float32Array(length);
  var index = 0, inputIndex = 0;
  while (inputIndex < inputL.length) {
    result[index++] = inputL[inputIndex];
    result[index++] = inputR[inputIndex];
    inputIndex++;
  }
  return result;
}

function floatTo16BitPCM(output, offset, input) {
  for (var i = 0; i < input.length; i++, offset += 2) {
    var s = Math.max(-1, Math.min(1, input[i]));
    output.setInt16(offset, s < 0 ? s * 0x8000 : s * 0x7FFF, true);
  }
}

function writeString(view, offset, string) {
  for (var i = 0; i < string.length; i++) {
    view.setUint8(offset + i, string.charCodeAt(i));
  }
}

function encodeWAV(samples) {
  var buffer = new ArrayBuffer(44 + samples.length * 2);
  var view = new DataView(buffer);
  writeString(view, 0, 'RIFF');
  view.setUint32(4, 36 + samples.length * 2, true);
  writeString(view, 8, 'WAVE');
  writeString(view, 12, 'fmt ');
  view.setUint32(16, 16, true);
  view.setUint16(20, 1, true);
  view.setUint16(22, numChannels, true);
  view.setUint32(24, sampleRate, true);
  view.setUint32(28, sampleRate * numChannels * 2, true);
  view.setUint16(32, numChannels * 2, true);
  view.setUint16(34, 16, true);
  writeString(view, 36, 'data');
  view.setUint32(40, samples.length * 2, true);
  floatTo16BitPCM(view, 44, samples);
  return view;
}
