मेट्रोनोम - टैप टेम्पो BPM डिटेक्टर और क्लिक ट्रैक ऑनलाइन

// Web Audio API Metronome with Lookahead Scheduler

class Metronome {
  constructor(bpm = 120, beatsPerMeasure = 4) {
    this.bpm = bpm;
    this.beatsPerMeasure = beatsPerMeasure;
    this.isPlaying = false;
    this.currentBeat = 0;
    this.nextNoteTime = 0;
    this.timerID = null;
    this.audioContext = null;
  }

  start() {
    if (this.isPlaying) return;
    this.audioContext = new AudioContext();
    this.isPlaying = true;
    this.currentBeat = 0;
    this.nextNoteTime = this.audioContext.currentTime;
    this.timerID = setInterval(() => this._scheduler(), 25);
  }

  stop() {
    this.isPlaying = false;
    if (this.timerID) clearInterval(this.timerID);
    if (this.audioContext) this.audioContext.close();
  }

  _scheduler() {
    while (this.nextNoteTime < this.audioContext.currentTime + 0.1) {
      this._playClick(this.nextNoteTime, this.currentBeat === 0);
      this.nextNoteTime += 60.0 / this.bpm;
      this.currentBeat = (this.currentBeat + 1) % this.beatsPerMeasure;
    }
  }

  _playClick(time, isAccent) {
    const osc = this.audioContext.createOscillator();
    const gain = this.audioContext.createGain();
    osc.frequency.value = isAccent ? 1000 : 800;
    gain.gain.setValueAtTime(isAccent ? 1.0 : 0.7, time);
    gain.gain.exponentialRampToValueAtTime(0.001, time + 0.03);
    osc.connect(gain);
    gain.connect(this.audioContext.destination);
    osc.start(time);
    osc.stop(time + 0.03);
  }
}

// Tap Tempo Detector
function createTapDetector(maxTaps = 8, resetMs = 2000) {
  const taps = [];
  let resetTimer = null;

  return {
    tap() {
      const now = performance.now();
      if (resetTimer) clearTimeout(resetTimer);
      resetTimer = setTimeout(() => { taps.length = 0; }, resetMs);

      taps.push(now);
      if (taps.length > maxTaps) taps.shift();
      if (taps.length < 2) return null;

      const intervals = [];
      for (let i = 1; i < taps.length; i++) {
        intervals.push(taps[i] - taps[i - 1]);
      }
      const avg = intervals.reduce((a, b) => a + b) / intervals.length;
      return Math.round(60000 / avg);
    },
    reset() {
      taps.length = 0;
    },
  };
}

// Usage
const metronome = new Metronome(120, 4);
metronome.start();
setTimeout(() => metronome.stop(), 5000);