// 音效：WebAudio 合成，不需要资源文件。GDD §6：落子短音（音高随步号上升，12 后循环）、冲突闷音、过关和弦。
// Cocos 版换成 AudioSource 播放几段短音即可，接口保持 step/conflict/cleared/reject。

export interface Sfx {
  unlock(): void;
  step(n: number): void;
  conflict(): void;
  cleared(): void;
  reject(): void;
  enabled: boolean;
}

export class WebAudioSfx implements Sfx {
  enabled = true;
  private ctx: AudioContext | null = null;

  /** 必须在用户手势里调用一次，iOS 才放行 */
  unlock(): void {
    if (!this.ctx) {
      const AC = window.AudioContext ?? (window as unknown as { webkitAudioContext?: typeof AudioContext }).webkitAudioContext;
      if (!AC) return;
      this.ctx = new AC();
    }
    if (this.ctx.state === 'suspended') void this.ctx.resume();
  }

  private tone(freq: number, dur: number, type: OscillatorType, gain: number, when = 0): void {
    if (!this.enabled || !this.ctx) return;
    const ctx = this.ctx;
    const t0 = ctx.currentTime + when;
    const osc = ctx.createOscillator();
    const g = ctx.createGain();
    osc.type = type;
    osc.frequency.setValueAtTime(freq, t0);
    g.gain.setValueAtTime(0.0001, t0);
    g.gain.exponentialRampToValueAtTime(gain, t0 + 0.008);
    g.gain.exponentialRampToValueAtTime(0.0001, t0 + dur);
    osc.connect(g).connect(ctx.destination);
    osc.start(t0);
    osc.stop(t0 + dur + 0.02);
  }

  step(n: number): void {
    const semi = (n - 1) % 12;
    const f = 523.25 * Math.pow(2, semi / 12);
    this.tone(f, 0.09, 'sine', 0.18);
  }

  conflict(): void {
    this.tone(130, 0.16, 'square', 0.08);
  }

  cleared(): void {
    const base = 523.25;
    [0, 4, 7, 12].forEach((semi, i) => this.tone(base * Math.pow(2, semi / 12), 0.22, 'triangle', 0.16, i * 0.07));
  }

  reject(): void {
    this.tone(220, 0.06, 'triangle', 0.06);
  }
}