// app/static/js/services/bridgeAudioWorklet.js
// VSTi crackle fix: audio sink chay tren audio thread (khong jank main thread).
// - Ring block 256 mau, toi da 32 block (~170ms @48k) — hap thu jitter pump
//   (V45.27: 16->32 de dung crackle VST2 loop/tremolo — render loop C++ bi
//   stall khi instrument xu li loop/tremolo nang CPU; 8->16 truoc do da dung
//   tremolo crackle, 16 van chua du cho stall >85ms). Flush o play start
//   (app.jsx) xoa ring nen do tre khong tang: ring thuong can o preview.
// - Underrun: fade ve 0 thay vi click (hard silence).
// - Resume sau silence: fade vao tu 0.
// - Overrun: drop block cu nhat + crossfade 64 mau tai diem drop (het click).
// - Stats: dem overrun/underrun, gui ve main thread moi ~0.5s — kiem tra
//   con crackle nao la do ring can (underrun) hay ring tran (overrun).
class BridgeAudioSinkProcessor extends AudioWorkletProcessor {
  constructor() {
    super();
    this._ring = [];
    this._MAX = 32;
    this._gain = 1.0;
    this._lastOutL = 0.0;
    this._lastOutR = 0.0;
    this._skipFade = 0;      // >0: con lai cua crossfade dang chay sau overrun drop
    this._fadeLen = 0;       // tong chieu dai crossfade hien tai (cap 1024)
    this._skipFromL = 0.0;
    this._skipFromR = 0.0;
    this._wasUnderrun = false;
    this._statAccum = 0;
    this._stats = { overruns: 0, underruns: 0 };
    this.port.onmessage = (e) => {
      const m = e.data;
      if (!m) return;
      if (m.type === 'audio') {
        this._ring.push({ l: m.l, r: m.r });
        while (this._ring.length > this._MAX) {
          // overrun: bo block cu nhat; lan consume toi se crossfade ranh gioi
          // V45.32: crossfade tich luy — moi block drop cong 256 mau fade, cap
          // 1024 (~21ms) thay vi co dinh 64 mau (1.3ms qua ngan -> blip/wow khi
          // drop loat block o chord nhieu voice = crackle VST2 tremolo/loop)
          this._ring.shift();
          this._skipFade = Math.min(this._skipFade + 256, 1024);
          this._fadeLen = this._skipFade;
          this._stats.overruns++;
        }
      } else if (m.type === 'flush') {
        this._ring.length = 0;
        this._gain = 1.0;
        this._skipFade = 0;
        this._fadeLen = 0;
      }
    };
  }
  process(inputs, outputs) {
    const out = outputs[0];
    if (!out || out.length < 2) return true;
    const L = out[0];
    const R = out[1];
    const n = L.length;
    let w = 0;
    while (w < n) {
      if (this._ring.length) {
        if (this._wasUnderrun) this._wasUnderrun = false;
        const blk = this._ring[0];
        const avail = blk.l.length;
        const take = Math.min(avail, n - w);
        if (this._skipFade > 0) {
          const done = this._fadeLen - this._skipFade;
          for (let i = 0; i < take; i++) {
            const t = (done + i) / this._fadeLen;
            L[w + i] = (this._lastOutL * (1 - t) + blk.l[i] * t) * this._gain;
            R[w + i] = (this._lastOutR * (1 - t) + blk.r[i] * t) * this._gain;
          }
          this._skipFade = Math.max(0, this._skipFade - take);
        } else {
          for (let i = 0; i < take; i++) {
            L[w + i] = blk.l[i] * this._gain;
            R[w + i] = blk.r[i] * this._gain;
          }
        }
        this._lastOutL = L[w + take - 1];
        this._lastOutR = R[w + take - 1];
        if (this._gain < 1.0) this._gain = Math.min(1.0, this._gain + take / 256.0);
        w += take;
        if (take >= avail) {
          this._ring.shift();
        } else {
          blk.l = blk.l.subarray(take);
          blk.r = blk.r.subarray(take);
        }
      } else {
        // underrun: fade ve 0 (khong click) — dem 1 lan moi lan roi vao trang thai trong
        if (!this._wasUnderrun) { this._wasUnderrun = true; this._stats.underruns++; }
        for (let i = w; i < n; i++) {
          this._gain = Math.max(0, this._gain - 1.0 / 256.0);
          L[i] = this._lastOutL * this._gain;
          R[i] = this._lastOutR * this._gain;
        }
        this._lastOutL *= this._gain;
        this._lastOutR *= this._gain;
        w = n;
      }
    }
    // Stats: gui ve main thread moi ~0.5s (24000 mau @48k) — log overrun/underrun
    this._statAccum += n;
    if (this._statAccum >= 24000) {
      this._statAccum = 0;
      try {
        this.port.postMessage({
          type: 'stats',
          overruns: this._stats.overruns,
          underruns: this._stats.underruns,
          ring: this._ring.length,
          max: this._MAX
        });
      } catch (e) {}
    }
    return true;
  }
}
registerProcessor('bridge-audio-sink', BridgeAudioSinkProcessor);