declare name        "Drifting Echo";
declare subtitle    "Delay Effect";
declare description "Warm analog echo with gently drifting modulated repeats and soft tape-style saturation.";
declare author      "Chaos Audio";
declare copyright   "(c) Chaos Audio 2025";

import("stdfaust.lib");

// Controls (max 9 chars)
timeKnob    = hslider("Time[stratus:0]", 380, 40, 1000, 1) : si.smoo;      // ms
repeatsKnob = hslider("Repeats[stratus:1]", 45, 0, 100, 0.1) : si.smoo;    // %
toneKnob    = hslider("Tone[stratus:2]", 50, 0, 100, 1) : si.smoo;        // Warm/Bright
depthKnob   = hslider("Depth[stratus:3]", 30, 0, 100, 1) : si.smoo;       // %
rateKnob    = hslider("Rate[stratus:4]", 1.2, 0.1, 6.0, 0.05) : si.smoo;  // Hz
mixKnob     = hslider("Mix[stratus:5]", 35, 0, 100, 1) : si.smoo;         // %
driftToggle = hslider("Drift[stratus:6]", 1, 0, 1, 1) : si.smoo;          // 0 or 1

// Maximum delay line allocation (1.2 seconds)
maxDelaySamples = int(1.2 * 192000);

// Base delay in samples
baseDelaySamples = timeKnob * 0.001 * ma.SR;

// Multi-speed drift LFO: subtle non-repeating movement when Drift is active
// Combine primary LFO with two slow, inharmonic drift LFOs
lfo1 = os.osc(rateKnob);
driftLfo1 = os.osc(0.17) * 0.6;
driftLfo2 = os.osc(0.073) * 0.4;
driftFactor = (driftLfo1 + driftLfo2) * driftToggle;

// Modulation depth mapped to sample excursion (up to ~3.5ms vibrato / drift)
modAmount = (depthKnob * 0.01) * (0.0035 * ma.SR);
totalMod = (lfo1 * 0.7 + driftFactor * 0.8) * modAmount;

// Clamped total delay in samples
targetDelay = max(10, min(maxDelaySamples - 10, baseDelaySamples + totalMod));

// Repeats feedback gain (0.0 to ~0.96 so it oscillates softly without runaway at 100%)
fbGain = repeatsKnob * 0.0096;

// Tone filter: warm lowpass + gentle highpass to avoid muddy sub-bass
// Tone knob scales cutoff from warm/dark (1.2 kHz) to open (6.5 kHz)
lpCutoff = 1200.0 + (toneKnob * 0.01) * 5300.0;
hpCutoff = 80.0;

// Soft saturation for warm repeats: tanh based saturator
softSat(x) = ma.tanh(x * 1.25) * 0.8;

// Delay loop with recursive feedback
delayFeedbackLoop = (+ : de.fdelay(maxDelaySamples, targetDelay)) ~ (
    fi.highpass(1, hpCutoff)
    : fi.lowpass(2, lpCutoff)
    : softSat
    : *(fbGain)
);

// Mix staging: keep dry crisp and 100% transparent, mix repeats smoothly
wetGain = mixKnob * 0.01;
dryGain = 1.0;

process(x) = (x * dryGain + wetSignal * wetGain) : fi.dcblocker : ma.tanh
with {
    wetSignal = delayFeedbackLoop(x);
};