import TimedEvent from './timedEvent';

/**
 * TimedTone generates a pure tone using the Web Audio API. It maps the
 * oscillator lifecycle to TimedEvent lifecycle methods. Note: OscillatorNodes
 * cannot always be restarted after they are stopped, so resume creates a
 * fresh oscillator when necessary.
 *
 * constructor(duration=0, frequency=440, waveform='sine', gain=1.0)
 *  - duration: milliseconds (0 unknown, -1 loop)
 *  - frequency: Hz of the oscillator
 *  - waveform: oscillator type (sine, square, sawtooth, triangle, 'custom')
 *  - gain: output gain (0.0 - 1.0)
 */
export default class TimedTone extends TimedEvent {
  frequency: number;
  waveform: OscillatorType;
  gain: number;

  oscillatorNode: OscillatorNode | null;
  gainNode: GainNode | null;

  constructor(duration = 0, frequency = 440, waveform: OscillatorType = 'sine', gain = 1.0) {
    // create audio nodes without using `this` (so we can call super first)
    const context = new AudioContext();
    const osc = new OscillatorNode(context, { type: waveform, frequency });
    const g = new GainNode(context, { gain });
    osc.connect(g).connect(context.destination);

    super(duration);

    this.frequency = frequency;
    this.waveform = waveform;
    this.gain = gain;
    this.oscillatorNode = osc;
    this.gainNode = g;
  }

  start() {
    if (this.started) return;
    this.oscillatorNode?.start();
    super.start();
  }

  pause() {
    if (this.paused) return;
    this.oscillatorNode?.stop();
    super.pause();
  }

  resume() {
    if (!this.paused) return;
    // WebAudio OscillatorNodes cannot be restarted once stopped in many browsers.
    // To resume, create a new oscillator and reconnect.
    if (this.gainNode) {
      const ctx = (this.gainNode as GainNode).context;
      const newOsc = new OscillatorNode(ctx, { type: this.waveform, frequency: this.frequency });
      newOsc.connect(this.gainNode);
      newOsc.start();
      this.oscillatorNode = newOsc;
    }
    super.resume();
  }

  cancel() {
    this.oscillatorNode?.stop();
    super.cancel();
  }

  setVolume(gain = 1.0) {
    this.gain = gain;
    if (this.gainNode) this.gainNode.gain.value = gain;
  }
}