/*
 * Copyright (C) 2015 Bastian Bloessl <bloessl@ccs-labs.org>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "comb.h"

using namespace gr::ieee802_11::equalizer;

void comb::equalize(gr_complex* in,
                    int n,
                    gr_complex* symbols,
                    uint8_t* bits,
                    std::shared_ptr<gr::digital::constellation> mod)
{

    gr_complex pilot[4];

    if (n < 2) {
        pilot[0] = in[11];
        pilot[1] = -in[25];
        pilot[2] = in[39];
        pilot[3] = in[53];
    } else {
        gr_complex p = POLARITY[(n - 2) % 127];
        pilot[0] = in[11] * p;
        pilot[1] = in[25] * p;
        pilot[2] = in[39] * p;
        pilot[3] = in[53] * -p;
    }

    gr_complex avg = (pilot[0] + pilot[1] + pilot[2] + pilot[3]) / gr_complex(4, 0);

    for (int i = 0; i < 64; i++) {
        gr_complex H;
        if (i <= 11) {
            H = gr_complex((11 - i) / 11.0, 0) * avg + gr_complex(i / 11.0, 0) * pilot[0];
        } else if (i <= 25) {
            H = gr_complex((25 - i) / 14.0, 0) * pilot[0] +
                gr_complex((i - 11) / 14.0, 0) * pilot[1];
        } else if (i <= 39) {
            H = gr_complex((39 - i) / 14.0, 0) * pilot[1] +
                gr_complex((i - 25) / 14.0, 0) * pilot[2];
        } else if (i <= 53) {
            H = gr_complex((53 - i) / 14.0, 0) * pilot[2] +
                gr_complex((i - 39) / 14.0, 0) * pilot[3];
        } else {
            H = gr_complex((64 - i) / 11.0, 0) * pilot[3] +
                gr_complex((i - 53) / 11.0, 0) * avg;
        }

        if (n == 0) {
            d_H[i] = H;
        } else {
            d_H[i] = gr_complex(1 - alpha, 0) * d_H[i] + gr_complex(alpha, 0) * H;
        }
    }

    int c = 0;
    for (int i = 0; i < 64; i++) {
        if ((i == 11) || (i == 25) || (i == 32) || (i == 39) || (i == 53) || (i < 6) ||
            (i > 58)) {
            continue;
        } else {
            symbols[c] = in[i] / d_H[i];
            bits[c] = mod->decision_maker(&symbols[c]);
            c++;
        }
    }
}

double comb::get_snr() { return 42; }