/**
* Digital Voice Modem - Host Software
* GPLv2 Open Source. Use is subject to license terms.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* @package DVM / Host Software
*
*/
//
// Based on code from the MMDVMHost project. (https://github.com/g4klx/MMDVMHost)
// Licensed under the GPLv2 License (https://opensource.org/licenses/GPL-2.0)
//
/*
*   Copyright (C) 2016 by Jonathan Naylor G4KLX
*
*   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 2 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, write to the Free Software
*   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include "lookups/RSSIInterpolator.h"
#include "Log.h"

using namespace lookups;

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cctype>

// ---------------------------------------------------------------------------
//  Public Class Members
// ---------------------------------------------------------------------------

/// <summary>
/// Initializes a new instance of the RSSIInterpolator class.
/// </summary>
RSSIInterpolator::RSSIInterpolator() :
    m_map()
{
    /* stub */
}

/// <summary>
/// Finalizes a instance of the RSSIInterpolator class.
/// </summary>
RSSIInterpolator::~RSSIInterpolator()
{
    m_map.clear();
}

/// <summary>
/// Loads the table from the passed RSSI mapping file.
/// </summary>
/// <param name="filename">Full-path to the RSSI mapping file.</param>
/// <returns>True, if RSSI mapping was loaded, otherwise false.</returns>
bool RSSIInterpolator::load(const std::string& filename)
{
    FILE* fp = ::fopen(filename.c_str(), "rt");
    if (fp == nullptr) {
        LogError(LOG_HOST, "Cannot open the RSSI data file - %s", filename.c_str());
        return false;
    }

    char buffer[100U];
    while (::fgets(buffer, 100, fp) != nullptr) {
        if (buffer[0U] == '#')
            continue;

        char* p1 = ::strtok(buffer, " \t\r\n");
        char* p2 = ::strtok(NULL, " \t\r\n");

        if (p1 != NULL && p2 != NULL) {
            uint16_t raw = uint16_t(::atoi(p1));
            int     rssi = ::atoi(p2);
            m_map.insert(std::pair<uint16_t, int>(raw, rssi));
        }
    }

    ::fclose(fp);

    LogInfoEx(LOG_HOST, "Loaded %u RSSI data mapping points from %s", m_map.size(), filename.c_str());

    return true;
}

/// <summary>
/// Interoplates the given raw RSSI value with the lookup map.
/// </summary>
/// <param name="val">Raw RSSI value from modem DSP.</param>
/// <returns>Interpolated RSSI value.</returns>
int RSSIInterpolator::interpolate(uint16_t val) const
{
    if (m_map.empty())
        return 0;

    std::map<uint16_t, int>::const_iterator it = m_map.lower_bound(val);

    if (it == m_map.end())
        return m_map.rbegin()->second;

    if (it == m_map.begin())
        return it->second;

    uint16_t x2 = it->first;
    int      y2 = it->second;

    --it;
    uint16_t x1 = it->first;
    int      y1 = it->second;

    float p = float(val - x1) / float(x2 - x1);

    return int((1.0F - p) * float(y1) + p * float(y2));
}