/**
 * One-shot playback of a sample range with a playhead callback, shared by
 * the explorer (runs) and the clip editor (recorded clips). Only one
 * range plays per Player; starting again stops what was playing.
 */
export class Player {
  private ctx: () => AudioContext;
  private cur: { src: AudioBufferSourceNode; ctxT0: number; startT: number; endT: number; raf: number } | null = null;
  /** Playhead position in seconds while playing, then null once stopped. */
  onTick: ((t: number | null) => void) | null = null;
  /** Fired on every start and stop, for button labels. */
  onStateChange: (() => void) | null = null;

  constructor(ctx: () => AudioContext) {
    this.ctx = ctx;
  }

  get playing(): boolean {
    return this.cur !== null;
  }

  stop(): void {
    if (!this.cur) return;
    cancelAnimationFrame(this.cur.raf);
    try { this.cur.src.stop(); } catch { /* already ended */ }
    this.cur = null;
    this.onTick?.(null);
    this.onStateChange?.();
  }

  /** Play samples[startT*sr .. endT*sr); times are in seconds. */
  start(samples: Float32Array, sr: number, startT: number, endT: number): void {
    this.stop();
    const s0 = Math.max(0, Math.round(startT * sr));
    const s1 = Math.min(samples.length, Math.round(endT * sr));
    if (s1 - s0 < 1) return;
    const ctx = this.ctx();
    const buf = ctx.createBuffer(1, s1 - s0, sr);
    buf.getChannelData(0).set(samples.subarray(s0, s1));
    const src = ctx.createBufferSource();
    src.buffer = buf;
    src.connect(ctx.destination);
    src.onended = () => { if (this.cur?.src === src) this.stop(); };
    const begin = () => {
      src.start();
      this.cur = { src, ctxT0: ctx.currentTime, startT, endT, raf: 0 };
      const tick = () => {
        if (this.cur?.src !== src) return;
        this.onTick?.(Math.min(this.cur.endT, this.cur.startT + (ctx.currentTime - this.cur.ctxT0)));
        this.cur.raf = requestAnimationFrame(tick);
      };
      this.cur.raf = requestAnimationFrame(tick);
      this.onStateChange?.();
    };
    if (ctx.state === 'suspended') void ctx.resume().then(begin);
    else begin();
  }
}