/* Stateful box-filter resampling: phase and integration survive render quanta. */
class TranscriptionPCM extends AudioWorkletProcessor {
  constructor() {
    super();
    this.ratio = sampleRate / 16000;
    this.weight = 0;
    this.sum = 0;
    this.samples = [];
    this.stopped = false;
    this.port.onmessage = ({ data }) => {
      if (data.type === 'flush') {
        this.stopped = true;
        if (this.weight > 0) this.samples.push(this.sum / this.weight);
        this.emit();
        this.port.postMessage({ type: 'flushed' });
      }
    };
  }
  emit() {
    if (!this.samples.length) return;
    const buffer = new ArrayBuffer(this.samples.length * 2);
    const view = new DataView(buffer);
    let energy = 0;
    this.samples.forEach((value, index) => {
      const sample = Math.max(-1, Math.min(1, value));
      view.setInt16(index * 2, Math.round(sample * (sample < 0 ? 32768 : 32767)), true);
      energy += sample * sample;
    });
    this.port.postMessage({ type: 'pcm', buffer, level: Math.sqrt(energy / this.samples.length) }, [buffer]);
    this.samples = [];
  }
  process(inputs) {
    if (this.stopped) return false;
    const channels = inputs[0];
    if (!channels?.length) return true;
    for (let i = 0; i < channels[0].length; i++) {
      let value = 0;
      for (const channel of channels) value += channel[i] / channels.length;
      let remaining = 1;
      while (remaining > 1e-9) {
        const take = Math.min(remaining, this.ratio - this.weight);
        this.sum += value * take;
        this.weight += take;
        remaining -= take;
        if (this.weight >= this.ratio - 1e-9) {
          this.samples.push(this.sum / this.ratio);
          this.sum = 0;
          this.weight = 0;
          if (this.samples.length >= 2400) this.emit();
        }
      }
    }
    return true;
  }
}
registerProcessor('transcription-pcm', TranscriptionPCM);