export class AudioManager {
  constructor() {
    this.context = null;
    this.rawStream = null;
    this.outputStream = null;
    this.source = null;
    this.gainNode = null;
    this.analyser = null;
    this.meterSink = null;
    this.meterData = new Float32Array(1024);
    this.gain = Number(localStorage.getItem('voicepoc.micGain') || 1);
  }

  async ensureContext() {
    if (!this.context) this.context = new AudioContext();
    await this.context.resume().catch(() => {});
    return this.context;
  }

  async attachInput(stream) {
    await this.ensureContext();
    this.detachInput();
    this.rawStream = stream;
    this.source = this.context.createMediaStreamSource(stream);
    this.gainNode = this.context.createGain();
    this.gainNode.gain.value = this.gain;
    this.analyser = this.context.createAnalyser();
    this.analyser.fftSize = 1024;
    this.meterSink = this.context.createGain();
    this.meterSink.gain.value = 0;
    const destination = this.context.createMediaStreamDestination();
    this.source.connect(this.gainNode).connect(this.analyser);
    // Keep the analyser alive without sending the microphone to the speakers.
    this.analyser.connect(this.meterSink).connect(this.context.destination);
    this.gainNode.connect(destination);
    this.outputStream = destination.stream;
    return this.outputStream;
  }

  detachInput() {
    for (const node of [this.source, this.gainNode, this.analyser, this.meterSink]) {
      try { node?.disconnect(); } catch {}
    }
    this.outputStream?.getTracks().forEach((track) => track.stop());
    this.rawStream?.getTracks().forEach((track) => track.stop());
    this.source = this.gainNode = this.analyser = this.meterSink = null;
    this.outputStream = this.rawStream = null;
  }

  setGain(value) {
    this.gain = Math.max(0, Math.min(2, Number(value) || 0));
    localStorage.setItem('voicepoc.micGain', String(this.gain));
    if (this.gainNode) this.gainNode.gain.setTargetAtTime(this.gain, this.context.currentTime, 0.015);
  }

  getLevel() {
    if (!this.analyser) return { rms: 0, peak: 0, clipping: false };
    this.analyser.getFloatTimeDomainData(this.meterData);
    let sum = 0;
    let peak = 0;
    for (const sample of this.meterData) {
      const magnitude = Math.abs(sample);
      sum += sample * sample;
      peak = Math.max(peak, magnitude);
    }
    const rms = Math.sqrt(sum / this.meterData.length);
    return { rms, peak, clipping: peak >= 0.98 };
  }

  stop() {
    this.detachInput();
  }
}