import java.math.*;

class SongIterator implements AudioSignal {
  long time;
  BigInteger current;
  int sampleRate, sampleLength, samplePosition,
    noteLength, notePosition,
    fadeLength;
  float[] notes;
  float[] fade;
  SongIterator(int sampleRate, float[] notes, int fadeLength) {
    this.sampleRate = sampleRate;
    this.fadeLength = fadeLength;
    reset(notes);
  }
  void reset(float[] notes) {
    this.notes = notes;  
    sampleLength = (int) Math.ceil(sampleRate / notes[0]);
    time = 0;
    samplePosition = 0;
    notePosition = 0;
    current = new BigInteger("1");
    fade = new float[fadeLength];
    
    float normalize =  TWO_PI / sampleRate;
    for(int i = 0; i < notes.length; i++)
      this.notes[i] *= normalize;
  }
  void random(int bits) {
    current = new BigInteger(bits, new Random());
  }
  void generate(float[] samp) {
    boolean resync = false;   
    for(int i = 0; i < samp.length; i++) {   
      int total = current.bitLength();
      noteLength = (int) Math.ceil((float) total / notes.length);
     
      if(samplePosition < fadeLength) {
        float fadeValue = (float) samplePosition / fadeLength;
        samp[i] = (getSample(time) * fadeValue) + ((1 - fadeValue) * fade[samplePosition]);
      } else {
        samp[i] = getSample(time);
      }
      time++;
    
      samplePosition++;
      if(samplePosition % sampleLength == 0) {
        for(int j = 0; j < fadeLength; j++)
          fade[j] = getSample(time + j);
        
        samplePosition = 0;
        notePosition++;
        if(notePosition % noteLength == 0) {
          notePosition = 0;
          current = current.add(BigInteger.ONE);
        }
      }
    }
  }
  float getSample(long time) {
    float sample = 0;
    float on = 0;
    for(int i = notes.length * notePosition; i < notes.length * (notePosition + 1); i++) {
      int ai = i % notes.length;
      if(current.testBit(i)) {
        sample += sin(notes[ai] * time);
        on++;
      }
    }            
    return sample / on;
  }
  void generate(float[] left, float[] right) {
    generate(left);
    generate(right);
  }
}