#include "fx_overdrive.h"
#include <math.h>

void FxOverdrive_Init(FxOverdriveState *state, FxOverdriveParams *params)
{
    state->tone_lp_state = 0.0f;

    params->enabled = false;
    params->drive   = 0.4f;
    params->tone    = 0.6f;
    params->level   = 0.7f;
}

float FxOverdrive_Process(FxOverdriveState *state, const FxOverdriveParams *params, float input)
{
    if (!params->enabled)
    {
        return input;
    }

    float driven = input * (1.0f + params->drive * 20.0f);

    /* Ecretage asymetrique (exponentiel) : plus caracteristique/agressif qu'un tanh symetrique. */
    float shaped;
    if (driven >= 0.0f)
    {
        shaped = 1.0f - expf(-driven);
    }
    else
    {
        shaped = -1.0f + expf(driven);
    }

    /* Filtre passe-bas une pole pour la tonalite : coefficient = tone (0..1). */
    float coeff = 0.05f + params->tone * 0.9f;
    state->tone_lp_state += coeff * (shaped - state->tone_lp_state);

    return state->tone_lp_state * params->level;
}