#include "fx_reverb.h"
#include <string.h>

/* Lignes a retard inspirees de Freeverb (Jezar), redimensionnees de 44.1kHz vers 48kHz. */
#define FX_REVERB_COMB0 1215U
#define FX_REVERB_COMB1 1293U
#define FX_REVERB_COMB2 1390U
#define FX_REVERB_COMB3 1476U
#define FX_REVERB_COMB4 1548U
#define FX_REVERB_COMB5 1623U
#define FX_REVERB_COMB6 1695U
#define FX_REVERB_COMB7 1761U

#define FX_REVERB_ALLPASS0 605U
#define FX_REVERB_ALLPASS1 480U
#define FX_REVERB_ALLPASS2 371U
#define FX_REVERB_ALLPASS3 245U

static float fx_reverb_comb_buf0[FX_REVERB_COMB0];
static float fx_reverb_comb_buf1[FX_REVERB_COMB1];
static float fx_reverb_comb_buf2[FX_REVERB_COMB2];
static float fx_reverb_comb_buf3[FX_REVERB_COMB3];
static float fx_reverb_comb_buf4[FX_REVERB_COMB4];
static float fx_reverb_comb_buf5[FX_REVERB_COMB5];
static float fx_reverb_comb_buf6[FX_REVERB_COMB6];
static float fx_reverb_comb_buf7[FX_REVERB_COMB7];

static float fx_reverb_allpass_buf0[FX_REVERB_ALLPASS0];
static float fx_reverb_allpass_buf1[FX_REVERB_ALLPASS1];
static float fx_reverb_allpass_buf2[FX_REVERB_ALLPASS2];
static float fx_reverb_allpass_buf3[FX_REVERB_ALLPASS3];

static float FxComb_Process(FxCombState *c, float input, float feedback, float damp1, float damp2)
{
    float output = c->buffer[c->idx];
    c->filter_store = (output * damp2) + (c->filter_store * damp1);
    c->buffer[c->idx] = input + (c->filter_store * feedback);
    c->idx = (c->idx + 1U) % c->size;
    return output;
}

static float FxAllpass_Process(FxAllpassState *a, float input, float feedback)
{
    float buf_out = a->buffer[a->idx];
    float output = -input + buf_out;
    a->buffer[a->idx] = input + buf_out * feedback;
    a->idx = (a->idx + 1U) % a->size;
    return output;
}

void FxReverb_Init(FxReverbState *state, FxReverbParams *params)
{
    params->enabled   = false;
    params->room_size = 0.5f;
    params->damping   = 0.5f;
    params->mix       = 0.3f;

    float *comb_buffers[FX_REVERB_NUM_COMBS] = {
        fx_reverb_comb_buf0, fx_reverb_comb_buf1, fx_reverb_comb_buf2, fx_reverb_comb_buf3,
        fx_reverb_comb_buf4, fx_reverb_comb_buf5, fx_reverb_comb_buf6, fx_reverb_comb_buf7
    };
    uint32_t comb_sizes[FX_REVERB_NUM_COMBS] = {
        FX_REVERB_COMB0, FX_REVERB_COMB1, FX_REVERB_COMB2, FX_REVERB_COMB3,
        FX_REVERB_COMB4, FX_REVERB_COMB5, FX_REVERB_COMB6, FX_REVERB_COMB7
    };
    for (uint32_t i = 0; i < FX_REVERB_NUM_COMBS; i++)
    {
        state->combs[i].buffer = comb_buffers[i];
        state->combs[i].size = comb_sizes[i];
        state->combs[i].idx = 0;
        state->combs[i].filter_store = 0.0f;
        memset(comb_buffers[i], 0, comb_sizes[i] * sizeof(float));
    }

    float *allpass_buffers[FX_REVERB_NUM_ALLPASS] = {
        fx_reverb_allpass_buf0, fx_reverb_allpass_buf1, fx_reverb_allpass_buf2, fx_reverb_allpass_buf3
    };
    uint32_t allpass_sizes[FX_REVERB_NUM_ALLPASS] = {
        FX_REVERB_ALLPASS0, FX_REVERB_ALLPASS1, FX_REVERB_ALLPASS2, FX_REVERB_ALLPASS3
    };
    for (uint32_t i = 0; i < FX_REVERB_NUM_ALLPASS; i++)
    {
        state->allpass[i].buffer = allpass_buffers[i];
        state->allpass[i].size = allpass_sizes[i];
        state->allpass[i].idx = 0;
        memset(allpass_buffers[i], 0, allpass_sizes[i] * sizeof(float));
    }
}

float FxReverb_Process(FxReverbState *state, const FxReverbParams *params, float input)
{
    if (!params->enabled)
    {
        return input;
    }

    float feedback = 0.28f + params->room_size * 0.7f;
    float damp1 = params->damping * 0.4f;
    float damp2 = 1.0f - damp1;

    float out = 0.0f;
    for (uint32_t i = 0; i < FX_REVERB_NUM_COMBS; i++)
    {
        out += FxComb_Process(&state->combs[i], input, feedback, damp1, damp2);
    }
    out /= (float)FX_REVERB_NUM_COMBS;

    for (uint32_t i = 0; i < FX_REVERB_NUM_ALLPASS; i++)
    {
        out = FxAllpass_Process(&state->allpass[i], out, 0.5f);
    }

    return input * (1.0f - params->mix) + out * params->mix;
}