// mod_audio_adsr.omfx — OmniScript Modulator
// Audio-triggered ADSR envelope. Detects transients above a threshold
// and fires a classic four-stage envelope. Perfect for sidechain-style
// ducking, audio-reactive filter sweeps, or "VCA-on-transient" effects.

@name: Audio-Triggered ADSR
@desc: Fires an ADSR envelope when audio crosses a threshold
@mode: modulator

@param[0] name="Threshold" min=-60.0 max=0.0   default=-20.0 unit="dB"
@param[1] name="Attack"    min=0.1   max=500   default=5     unit="ms"
@param[2] name="Decay"     min=1     max=2000  default=100   unit="ms"
@param[3] name="Sustain"   min=0.0   max=1.0   default=0.5
@param[4] name="Release"   min=1     max=3000  default=200   unit="ms"
@param[5] name="Hold"      min=0     max=2000  default=0     unit="ms"

fn db_to_linear(db) {
    return pow(10.0, db * 0.05);
}

fn time_coeff(ms, sr) {
    return exp(-1.0 / max(ms * 0.001 * sr, 1.0));
}

// Stage: 0=idle 1=attack 2=hold 3=decay 4=sustain 5=release
@init
  stage = 0;
  level = 0.0;
  hold_counter = 0.0;
  retrigger_guard = 0.0;
  env_in = 0.0;

@sample
  // Fast envelope follower on input (peak with quick decay)
  rect = max(abs(spl0), abs(spl1));
  if rect > env_in {
    env_in = rect;
  } else {
    env_in = env_in * 0.999;
  }

  thr = db_to_linear(param[0]);

  // Retrigger guard prevents double-fires on single transients
  if retrigger_guard > 0.0 { retrigger_guard = retrigger_guard - 1.0; }

  // Trigger detection: rising edge above threshold
  if env_in > thr && retrigger_guard < 0.5 && stage < 0.5 {
    stage = 1;
    retrigger_guard = sample_rate * 0.010;  // 10 ms lockout
  }

  // Stage 1 — Attack
  if stage > 0.5 && stage < 1.5 {
    a = time_coeff(param[1], sample_rate);
    level = level * a + 1.0 * (1.0 - a);
    if level > 0.99 {
      level = 1.0;
      stage = 2;
      hold_counter = param[5] * 0.001 * sample_rate;
    }
  }

  // Stage 2 — Hold
  if stage > 1.5 && stage < 2.5 {
    hold_counter = hold_counter - 1.0;
    if hold_counter <= 0.0 { stage = 3; }
  }

  // Stage 3 — Decay to sustain
  if stage > 2.5 && stage < 3.5 {
    d = time_coeff(param[2], sample_rate);
    level = level * d + param[3] * (1.0 - d);
    if abs(level - param[3]) < 0.001 { stage = 4; }
  }

  // Stage 4 — Sustain (hold until input drops)
  if stage > 3.5 && stage < 4.5 {
    level = param[3];
    if env_in < thr * 0.5 { stage = 5; }
  }

  // Stage 5 — Release
  if stage > 4.5 {
    r = time_coeff(param[4], sample_rate);
    level = level * r;
    if level < 0.0005 {
      level = 0.0;
      stage = 0;
    }
  }

  output = clamp(level, 0.0, 1.0);