/*
 * Copyright (C) 2025 Belousov Oleg
 *
 * This file is part of PortaPack.
 *
 * 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, 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; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

#include "gradient.hpp"

#include "convert.hpp"
#include "file_reader.hpp"
namespace fs = std::filesystem;

const std::filesystem::path default_gradient_file = u"waterfall.txt";

Gradient::Gradient() {
    step(0, 0, 0, 0);
}

void Gradient::set_default() {
    step(0, 0, 0, 0);
    step(86, 0, 0, 255);
    step(171, 0, 255, 0);
    step(255, 255, 0, 0);
}

bool Gradient::load_file(const std::filesystem::path& file_path) {
    File gradient_file;
    auto error = gradient_file.open(file_path.string());

    if (error)
        return false;

    // make sure the table starts at 0
    step(0, 0, 0, 0);

    auto reader = FileLineReader(gradient_file);
    for (const auto& line : reader) {
        if (line.length() == 0 || line[0] == '#')
            continue;  // Empty or comment line.

        auto cols = split_string(line, ',');

        if (cols.size() == 4) {
            int16_t index, r, g, b;

            if (!parse_int(cols[0], index) || index < 0 || index > 255)
                continue;

            if (!parse_int(cols[1], r) || r < 0 || r > 255)
                continue;

            if (!parse_int(cols[2], g) || g < 0 || g > 255)
                continue;

            if (!parse_int(cols[3], b) || b < 0 || b > 255)
                continue;

            step(index, r, g, b);
        }
    }

    // extend the gradient from the current index to the end of the table
    step(255, prev_r, prev_g, prev_b);

    return true;
}

void Gradient::step(int16_t index, int16_t r, int16_t g, int16_t b) {
    // prevent division by 0 if index == prev_index
    int16_t range = index - prev_index;
    if (range == 0) range = 1;

    for (int16_t i = prev_index; i <= index; i++) {
        int16_t t = i - prev_index;

        int16_t new_r = prev_r + (t * (r - prev_r) + range / 2) / range;
        int16_t new_g = prev_g + (t * (g - prev_g) + range / 2) / range;
        int16_t new_b = prev_b + (t * (b - prev_b) + range / 2) / range;

        if (i <= 255) lut[i] = ui::Color(new_r, new_g, new_b);
    }

    prev_index = index;
    prev_r = r;
    prev_g = g;
    prev_b = b;
}