sclass PianoSampler {
  double sampleRate = 48000;
  double currentSample;
  IAudioSample audio;
  
  persistable class Oscillator extends HasKey<Frequency> {
    double currentPeriodStart;
    // all recorded intensities
    new TreeMap<DoubleRange, Channels<Complex>> intensities;
    
    *(Frequency f) { super(f); }
    
    Frequency frequency() { ret key(); }
    double interval() { ret frequency().interval(); }
    
    void record_impl(DoubleRange r, Channels<Complex> c) {
      intensities.put(r, c);
    }
    
    void measure {
      double start = phaseMinus90(), end = start + interval();
      AudioHaarFeature haar = new(audio, start, end);
      var re = haar!;
      haar = new AudioHaarFeature(audio, currentPeriodStart, currentPeriodStart + interval());
      var im = haar!;
      record(this, doubleRange(start, end), complexChannels(re, im));
    }
    
    void start(double currentSample) {
      relocate(currentSample + startPhase());
    }
    
    void relocate(double time) {
      currentPeriodStart = time;
      completionsForSample.put(interval(), this);
    }
    
    double startPhase() { ret phase90(); }
    
    double quarterPhase() { ret interval()*.25; }
    
    double phaseMinus90() { ret currentPeriodStart - interval()*.25; }
    double phase0() { ret currentPeriodStart; }
    double phase90() { ret currentPeriodStart + interval()*.25; }
    double phase180() { ret currentPeriodStart + interval()*.5; }
    double phase270() { ret currentPeriodStart + interval()*.75; }
    double phase360() { ret currentPeriodStart + interval(); }
    double phase450() { ret currentPeriodStart + interval()*1.25; }
  }
  
  HasKeyMap<Frequency, Oscillator> oscillators = new(map(f -> new Oscillator(f), pianoFrequencies88()));
  new TreeMultiMap<Double, Oscillator> completionsForSample;
  
  *(IAudioSample *audio, double *currentSample) {}
  *(IAudioSample *audio) {} // start at time 0
  
  void init {
    for (o : oscillators)
      o.start(currentSample);
  }
  
  void stepTo(double time) {
    Double t = firstKey(completionsForSample);
    if (t != null && t <= time)
      for (Oscillator o : completionsForSample.getAndClear(t)) {
        o.measure();
        o.relocate(t);
      }
  }
  
  record RecordAdded(Oscillator oscillator, DoubleRange period, Channels<Complex> intensity) {}
  
  transient event interface onRecordAdded as OnRecordAdded shipping RecordAdded;
}