// For audio recognition, we need a double-precision (16 bit)
// integral image. We simply turn the sample data into pixels and
// have ourselves a verybig*1 image.
sclass AudioRecognizer {
  IAudioSample mainSample;
  
  interface IAudioSample {
    int channels();
    double length();
    double sampleSum(int channel, double start, double end);
    
    public default double getPixel(int channel, double start, double end) {
      ret doubleRatio(sampleSum(channel, start, end), end-start);
    }
  }
  
  // the 16 bit per channel 1D integral image
  // we use to represent audio samples
  class AudioSample implements IAudioSample {
    int channels;
    int length;
    long[] data;

    public int channels() { ret channels; }
    public double length() { ret length; }
    
    public double sampleSum(int channel, double start, double end) {
      int a = ifloor(start), b = ifloor(end);
      ret getEntry(channel, b)-getEntry(channel, a-1);
    }
    
    // get an entry of the sum table
    long getEntry(int channel, int i) {
      if (i < 0) ret 0;
      i = min(i, length-1);
      ret data[i*channels+channel];
    }
    
    *(short[] samples, int *channels) {
      length = l(samples)/channels;
      data = new long[length*channels];
      long[] sums = new[channels];
      int iSample = 0;
      for i to length:
        for c to channels: {
          data[iSample] = (sums[c] += samples[iSample]);
          iSample++;
        }
    }
    
    *(L<short[]> samples, int *channels) {
      length = lengthLevel2_shortArrays(samples);
      data = new long[length*channels];
      long[] sums = new[channels];
      int iSample = 0, iChunk = 0, iInArray = 0;
      short[] chunk = null;
      for i to length: {
        if (chunk == null || iInArray >= chunk.length) {
          chunk = samples.get(iChunk++);
          iInArray = 0;
        }
        
        for c to channels:
          data[iSample++] = (sums[c] += chunk[iInArray++]);
      }
    }
  }
  
  *() {}
  *(L<short[]> samples, int channels) {
    mainSample = new AudioSample(samples, channels);
  }
}