sclass AudioAdder extends AbstractAudioSample is IAddPlateau {

  new Cl<IAudioSample> sources;

  srecord SumAndSlope(double sum, double slope) {

    double sumFor(double myTime, double time) {

      ret sum+(time-myTime)*slope;

    }

  }

  // for now same value in all channels

  new TreeMap<Double, SumAndSlope> additions;

  void addSource(IAudioSample source) {

    addUnlessNull(sources, source);

  }

  void grabSpecsFromSource(IAudioSample source) {

    if (source == null) ret;

    setSampleRate(source.sampleRate());

    setChannels(source.channels());

    setBounds(source.bounds());

  }

  public void addPlateau(double start, double end, double intensity) {

    //printVars("addPlateau", +start, +end, +intensity);

    if (start >= end) ret;

    _incSlope(start, intensity);

    _incSlope(end, -intensity);

  }

  // We will probably add plateaus rather randomly throughout an area,

  // so could optimize this doing something akin to LogNArray.

  void _incSlope(double time, double intensity) {    

    if (intensity == 0) ret;

    // create, overwrite or delete

    var last = floorPair(additions, time);

    if (last == null) { // we are first node

      mapPut(additions, time, new SumAndSlope(0, intensity);

    } else if (last.a == time) { // we are our own node already

      last.b.slope += intensity;

    } else { // we are an insertion!

      mapPut(additions, time, new SumAndSlope(

        last.b.sumFor(last.a, time), last.b.slope+intensity);

    }

    recalcFrom(time);

    //printVars _incSlope(+time, +intensity, v := additions.get(time));

  }

  void recalcFrom(double time) {

    SumAndSlope me = additions.get(time);

    if (me == null) ret;

    Pair<Double, SumAndSlope> next;

    while ((next = higherPair(additions, time)) != null) {

      next.b.sum = me.sumFor(time, next.a);

      time = next.a;

      me = next.b;

    }

  }

  @Override

  public double readSumTable(int channel, int t) {

    double t2 = t+1;

    var p = floorPair(additions, t2);

    double sum = p == null ? 0.0 : p.b.sumFor(p.a, t2);

    //printVars readSumTable(+t, +p, +sum);

    for (source : sources) sum += source.readSumTable(channel, t);

    ret sum;

  }

}