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

#define FX_SATURATION_DC_BLOCK_R 0.995f

void FxSaturation_Init(FxSaturationState *state, FxSaturationParams *params)
{
    state->dc_block_x1 = 0.0f;
    state->dc_block_y1 = 0.0f;

    params->enabled = false;
    params->drive   = 0.3f;
    params->level   = 0.8f;
}

float FxSaturation_Process(FxSaturationState *state, const FxSaturationParams *params, float input)
{
    if (!params->enabled)
    {
        return input;
    }

    float driven = input * (1.0f + params->drive * 12.0f);
    float shaped = tanhf(driven);

    /* Le tanh sur un signal non symetrique introduit un leger DC : filtre bloqueur de DC. */
    float y = shaped - state->dc_block_x1 + FX_SATURATION_DC_BLOCK_R * state->dc_block_y1;
    state->dc_block_x1 = shaped;
    state->dc_block_y1 = y;

    return y * params->level;
}