/*
   Copyright (C) 2007, 2008, 2009, 2010, 2011 Her Majesty the Queen in
   Right of Canada (Communications Research Center Canada)

   Copyright (C) 2017
   Matthias P. Braendli, matthias.braendli@mpb.li
   Andreas Steger, andreas.steger@digris.ch

    http://opendigitalradio.org

   This block implements a memoryless polynom for digital predistortion.
   For better performance, multiplying is done in another thread, leading
   to a pipeline delay of two calls to MemlessPoly::process
 */
/*
   This file is part of ODR-DabMod.

   ODR-DabMod 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.

   ODR-DabMod 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 ODR-DabMod.  If not, see <http://www.gnu.org/licenses/>.
 */

#pragma GCC optimize ("O3")

#include "MemlessPoly.h"
#include "PcDebug.h"
#include "Utils.h"

#include <stdio.h>
#include <stdexcept>

#include <future>
#include <array>
#include <iostream>
#include <fstream>
#include <memory>
#include <complex>

using namespace std;

#define NUM_COEFS 5

MemlessPoly::MemlessPoly(const std::string& coefs_file, unsigned int num_threads) :
    PipelinedModCodec(),
    RemoteControllable("memlesspoly"),
    m_num_threads(num_threads),
    m_coefs(),
    m_coefs_file(coefs_file),
    m_coefs_mutex()
{
    PDEBUG("MemlessPoly::MemlessPoly(%s) @ %p\n",
            coefs_file.c_str(), this);

    if (m_num_threads == 0) {
        const unsigned int hw_concurrency = std::thread::hardware_concurrency();
        etiLog.level(info) << "Polynomial Predistorter will use " <<
            hw_concurrency << " threads (auto detected)";
    }
    else {
        etiLog.level(info) << "Polynomial Predistorter will use " <<
            m_num_threads << " threads (set in config file)";
    }

    RC_ADD_PARAMETER(ncoefs, "(Read-only) number of coefficients.");
    RC_ADD_PARAMETER(coeffile, "Filename containing coefficients. When written to, the new file gets automatically loaded.");

    load_coefficients(m_coefs_file);

    start_pipeline_thread();
}

void MemlessPoly::load_coefficients(const std::string &coefFile)
{
    std::vector<float> coefs;
    std::ifstream coef_fstream(coefFile.c_str());
    if (!coef_fstream) {
        throw std::runtime_error("MemlessPoly: Could not open file with coefs!");
    }
    int n_coefs;
    coef_fstream >> n_coefs;

    if (n_coefs <= 0) {
        throw std::runtime_error("MemlessPoly: coefs file has invalid format.");
    }
    else if (n_coefs != NUM_COEFS) {
        throw std::runtime_error("MemlessPoly: invalid number of coefs: " +
                std::to_string(n_coefs) + " expected " + std::to_string(NUM_COEFS));
    }

    etiLog.log(debug, "MemlessPoly: Reading %d coefs...", n_coefs);

    coefs.resize(n_coefs);

    for (int n = 0; n < n_coefs; n++) {
        float a;
        coef_fstream >> a;
        coefs[n] = a;

        if (coef_fstream.eof()) {
            etiLog.log(error, "MemlessPoly: file %s should contains %d coefs, "
                    "but EOF reached after %d coefs !",
                    coefFile.c_str(), n_coefs, n);
            throw std::runtime_error("MemlessPoly: coefs file invalid !");
        }
    }

    {
        std::lock_guard<std::mutex> lock(m_coefs_mutex);

        m_coefs = coefs;
    }
}

/* The restrict keyword is C99, g++ and clang++ however support __restrict
 * instead, and this allows the compiler to auto-vectorize the loop.
 */

static void apply_coeff(
        const vector<float> &coefs,
        const complexf *__restrict in, size_t start, size_t stop,
        complexf *__restrict out)
{
    for (size_t i = start; i < stop; i+=2) {

        /* Implement
           a1*x + a3*x*|x|^2 + a5*x*|x|^4 + a5*x*|x|^4 + a5*x*|x|^4 + a7*x*|x|^6
           with less multiplications:
           a0 + x*(a1 + x*(a2 + x*(a3 + x*(a3 + x*(a4 + a5*x)))));
           */

        /* Make sure to adapt NUM_COEFS when you change this */

        // Complex polynomial, all operations are on complex values.
        // Usually this is the representation we use when speaking
        // about the real-valued passband signal that the PA receives.
        float in_1_mag = std::abs(in[i]);
        float in_1_2 = in_1_mag * in_1_mag;
        float in_1_4 = in_1_2 * in_1_2;
        float in_1_6 = in_1_2 * in_1_4;
        float in_1_8 = in_1_4 * in_1_4;
        float in_1_10 = in_1_6 * in_1_4;

        float in_2_mag = std::abs(in[i]);
        float in_2_2 = in_2_mag * in_2_mag;
        float in_2_4 = in_2_2 * in_2_2;
        float in_2_6 = in_2_2 * in_2_4;
        float in_2_8 = in_2_4 * in_2_4;
        float in_2_10 = in_2_6 * in_2_4;

        out[i+0] = in[i+0] *
            (
             coefs[0] +
             coefs[1] * in_1_2 +
             coefs[2] * in_1_4 +
             coefs[3] * in_1_6 +
             coefs[4] * in_1_8 +
             coefs[5] * in_1_10
             );

        out[i+1] = in[i+1] *
            (
             coefs[0] +
             coefs[1] * in_2_2 +
             coefs[2] * in_2_4 +
             coefs[3] * in_2_6 +
             coefs[4] * in_2_8 +
             coefs[5] * in_2_10
             );
    }
}

int MemlessPoly::internal_process(Buffer* const dataIn, Buffer* dataOut)
{
    dataOut->setLength(dataIn->getLength());

    const complexf* in = reinterpret_cast<const complexf*>(dataIn->getData());
    complexf* out = reinterpret_cast<complexf*>(dataOut->getData());
    size_t sizeOut = dataOut->getLength() / sizeof(complexf);

    {
        std::lock_guard<std::mutex> lock(m_coefs_mutex);
        const unsigned int hw_concurrency = std::thread::hardware_concurrency();

        const unsigned int num_threads =
            (m_num_threads > 0) ? m_num_threads : hw_concurrency;

        if (num_threads) {
            const size_t step = sizeOut / num_threads;
            vector<future<void> > flags;

            size_t start = 0;
            for (size_t i = 0; i < num_threads - 1; i++) {
                flags.push_back(async(launch::async, apply_coeff,
                            m_coefs, in, start, start + step, out));

                start += step;
            }

            // Do the last in this thread
            apply_coeff(m_coefs, in, start, sizeOut, out);

            // Wait for completion of the tasks
            for (auto& f : flags) {
                f.get();
            }
        }
        else {
            apply_coeff(m_coefs, in, 0, sizeOut, out);
        }
    }

    return dataOut->getLength();
}

void MemlessPoly::set_parameter(const string& parameter, const string& value)
{
    stringstream ss(value);
    ss.exceptions ( stringstream::failbit | stringstream::badbit );

    if (parameter == "ncoefs") {
        throw ParameterError("Parameter 'ncoefs' is read-only");
    }
    else if (parameter == "coeffile") {
        try {
            load_coefficients(value);
            m_coefs_file = value;
        }
        catch (std::runtime_error &e) {
            throw ParameterError(e.what());
        }
    }
    else {
        stringstream ss;
        ss << "Parameter '" << parameter <<
            "' is not exported by controllable " << get_rc_name();
        throw ParameterError(ss.str());
    }
}

const string MemlessPoly::get_parameter(const string& parameter) const
{
    stringstream ss;
    if (parameter == "ncoefs") {
        ss << m_coefs.size();
    }
    else if (parameter == "coefFile") {
        ss << m_coefs_file;
    }
    else {
        ss << "Parameter '" << parameter <<
            "' is not exported by controllable " << get_rc_name();
        throw ParameterError(ss.str());
    }
    return ss.str();
}