// ****************************************************
//
// Parser for RIFF WAVE files.
//
// ****************************************************

//
// **** WaveParser object
//

function WaveParser(filename){

  if(typeof filename == 'string'){
    this.loadFile(filename);
  };

};

//
// **** Load a file into the WaveParser instance
//

WaveParser.prototype.loadFile = function(filename){

  try{
    this.file = fso.openTextFile(filename);
  }

  catch(e){
    log("WaveParser couldn't open " + filename);
    log("Error read:");
    log(e.description);
  }

};

//
// **** Parse the RIFF header and cue the file pointer to the start of sample data
//

WaveParser.prototype.parse = function(){

  var metadata = {};
      layout = WaveParser.waveFormatEx;

  for(var i = 0; i < layout.length; i++){

    var id = layout[i].id,
        len = layout[i].len,
        val = this.file.read(len).toString();

    switch(layout[i].type){

      case RIFFMEMBER_TYPE_ASCII:
        // Nothing doing
      break;

      default:
        val = val.reverse().toInt();

    };

    metadata[id] = val;

  }

  if(metadata.mainChunkId != 'RIFF'){
    throw WaveParser.Exception("File is not a RIFF.");
  }

  if(metadata.riffFormat != 'WAVE'){
    throw WaveParser.Exception("File is not a WAVE.");
  }

  if(metadata.audioType != 1){
    throw WaveParser.Exception("Timecode reader can only parse uncompressed PCM data.");
  }

  this.meta = metadata;

};

//
// **** Wave header layout; lengths in big-endian bytes
//

WaveParser.waveFormatEx = [

  {
    id : 'mainChunkId',
    len : 4,
    type : RIFFMEMBER_TYPE_ASCII
  },
  {
    id : 'mainChunkSz',
    len : 4
  },
  {
    id : 'riffFormat',
    len : 4,
    type : RIFFMEMBER_TYPE_ASCII
  },
  {
    id : 'fmtChunkId',
    len : 4,
    type : RIFFMEMBER_TYPE_ASCII
  },
  {
    id : 'fmtChunkSz',
    len : 4
  },
  {
    id : 'audioType',
    len : 2
  },
  {
    id : 'channels',
    len : 2
  },
  {
    id : 'sampleRate',
    len : 4
  },
  {
    id : 'byteRate',
    len : 4
  },
  {
    id : 'blockAlign',
    len : 2
  },
  {
    id : 'bits',
    len : 2
  }

];

//
// **** Exception generator
//

WaveParser.Exception = function(msg){
  return new Error(-1,'Wave parser - ' + msg);
};

//
// **** End of RIFF WAVE parser
//