// sf-fx-realtime.js — AudioWorkletProcessor nối WebAudio → SHM FX engine.
// process() gom 128-sample quantum thành block 256 stereo float32 (khớp
// FXRT_BLOCK trong FxRealtimeIPC.h) → postMessage cho main thread gửi WS;
// nhận block đã xử lý từ main thread → queue → phát ra output. Queue rỗng →
// zero fill (WS chưa kịp round-trip).
//
// Latency ~2 block; backlog > 32 block (~190ms) → drop block cũ nhất. Cap cao
// hấp thụ jitter main thread (rAF renderFrame nặng khi mở MASTERING PANEL) mà
// không drop. ponytail: thay drop bằng adaptive stretch khi cần chất lượng cao.
class SfFxRealtimeProcessor extends AudioWorkletProcessor {
  constructor() {
    super();
    this.BLOCK = 256;          // FXRT_BLOCK
    this.inL = new Float32Array(this.BLOCK);
    this.inR = new Float32Array(this.BLOCK);
    this.inCount = 0;
    this.outQueue = [];        // [{l: Float32Array, r: Float32Array}]
    this.outPos = 0;
    this.port.onmessage = (e) => {
      const d = e.data;
      if (!d || d.type !== 'out' || !d.l || !d.r) return;
      this.outQueue.push({ l: d.l, r: d.r });
      while (this.outQueue.length > 32) this.outQueue.shift();
    };
  }
  process(inputs, outputs) {
    const input = inputs[0];
    const output = outputs[0];
    const n = output[0] ? output[0].length : 128;
    const outL = output[0];
    const outR = output[1];

    // Góp input thành block 256 → gửi main thread (transferable buffer).
    if (input && input[0]) {
      const inL = input[0];
      const inR = input[1] || input[0];
      for (let i = 0; i < n; i++) {
        if (this.inCount < this.BLOCK) {
          this.inL[this.inCount] = inL[i];
          this.inR[this.inCount] = inR[i];
        }
        this.inCount++;
        if (this.inCount >= this.BLOCK) {
          const inter = new Float32Array(this.BLOCK * 2);
          for (let j = 0; j < this.BLOCK; j++) {
            inter[j * 2] = this.inL[j];
            inter[j * 2 + 1] = this.inR[j];
          }
          this.port.postMessage({ type: 'in', data: inter.buffer }, [inter.buffer]);
          this.inCount = 0;
        }
      }
    }

    // Phát output từ queue; rỗng → zero.
    for (let i = 0; i < n; i++) {
      if (this.outQueue.length === 0) {
        outL[i] = 0;
        if (outR) outR[i] = 0;
        continue;
      }
      const blk = this.outQueue[0];
      outL[i] = blk.l[this.outPos];
      if (outR) outR[i] = blk.r[this.outPos];
      this.outPos++;
      if (this.outPos >= this.BLOCK) {
        this.outQueue.shift();
        this.outPos = 0;
      }
    }
    return true;
  }
}

registerProcessor('sf-fx-realtime', SfFxRealtimeProcessor);