#include "game/map/tilemap.hpp"

#include <algorithm>
#include <cstddef>
#include <fstream>
#include <iostream>
#include <sstream>
#include <stdexcept>
#include <unordered_map>
#include <utility>

#include "core/rendering/screen.hpp"
#include "core/rendering/surface.hpp"
#include "core/resources/resource_cache.hpp"
#include "core/resources/resource_helper.hpp"
#include "external/fkyaml_node.hpp"

namespace {

    // Cada símbol del grid es mapeja a (col, fila) dins del tileset.
    using TileCoord = std::pair<int, int>;
    using Legend = std::unordered_map<char, TileCoord>;

    auto splitLines(const std::string& text) -> std::vector<std::string> {
        std::vector<std::string> lines;
        std::istringstream iss(text);
        std::string line;
        while (std::getline(iss, line)) {
            if (!line.empty()) { lines.push_back(line); }
        }
        return lines;
    }

    // La llegenda usa índexs lineals del tileset (esq→dre, dalt→baix).
    // Els convertim a (col, fila) amb el nombre de tiles per fila del tileset.
    auto parseLegend(const fkyaml::node& node, int tileset_cols) -> Legend {
        Legend legend;
        for (auto it = node.begin(); it != node.end(); ++it) {
            const auto KEY_STR = it.key().get_value<std::string>();
            if (KEY_STR.empty()) { continue; }
            const auto INDEX = it.value().get_value<int>();
            const int COL = INDEX % tileset_cols;
            const int ROW = INDEX / tileset_cols;
            legend[KEY_STR.front()] = {COL, ROW};
        }
        return legend;
    }

    // Copia un tile (col, fila) del tileset al buffer ARGB a la posició de
    // destí (dest_x, dest_y). Els píxels amb l'índex de transparència del
    // tileset es deixen com estan al buffer (alpha=0 per defecte).
    void blitTile(const Surface& tileset, int tile_size, int src_col, int src_row, std::vector<std::uint32_t>& dest, int dest_w, int dest_x, int dest_y) {
        const int SRC_X0 = src_col * tile_size;
        const int SRC_Y0 = src_row * tile_size;
        const auto TRANSPARENT = tileset.getTransparentColor();
        for (int y = 0; y < tile_size; ++y) {
            for (int x = 0; x < tile_size; ++x) {
                const auto IDX = tileset.getPixel(SRC_X0 + x, SRC_Y0 + y);
                if (IDX == TRANSPARENT) { continue; }
                const auto ARGB = tileset.getPaletteColor(IDX);
                const auto DST_OFFSET =
                    (static_cast<std::size_t>(dest_y + y) * static_cast<std::size_t>(dest_w)) + static_cast<std::size_t>(dest_x + x);
                dest[DST_OFFSET] = ARGB;
            }
        }
    }

}  // namespace

Tilemap::Tilemap(const std::string& yaml_path) {
    const auto FULL = Resource::Helper::resolve(yaml_path);
    std::ifstream file(FULL);
    if (!file.is_open()) {
        throw std::runtime_error("Tilemap: no s'ha pogut obrir " + FULL);
    }

    auto yaml = fkyaml::node::deserialize(file);

    const auto TILESET_PATH = yaml["tileset"].get_value<std::string>();
    const auto TILE_SIZE = yaml["tile_size"].get_value<int>();
    if (yaml.contains("origin")) {
        origin_x_ = yaml["origin"][0].get_value<int>();
        origin_y_ = yaml["origin"][1].get_value<int>();
    }

    // Carreguem el tileset al cache (idempotent) i el pillem per accedir
    // als seus píxels i paleta. La paleta del tileset ve del GIF mateix.
    // Ens cal abans de la llegenda per saber quants tiles per fila té.
    const auto& cache_name = TILESET_PATH;
    Resource::Cache::get().loadSurface(cache_name, TILESET_PATH);
    const auto TILESET = Resource::Cache::get().getSurface(cache_name);
    const int TILESET_COLS = TILESET->getWidth() / TILE_SIZE;

    const auto LEGEND = parseLegend(yaml["legend"], TILESET_COLS);
    const auto LINES = splitLines(yaml["data"].get_value<std::string>());

    const int ROWS = static_cast<int>(LINES.size());
    const int COLS = ROWS > 0 ? static_cast<int>(LINES.front().size()) : 0;
    width_px_ = COLS * TILE_SIZE;
    height_px_ = ROWS * TILE_SIZE;
    pixels_.assign(
        static_cast<std::size_t>(width_px_) * static_cast<std::size_t>(height_px_),
        0U);

    for (int row = 0; row < ROWS; ++row) {
        const auto& line = LINES[row];
        for (int col = 0; col < COLS && col < static_cast<int>(line.size()); ++col) {
            const char SYMBOL = line[col];
            const auto IT = LEGEND.find(SYMBOL);
            if (IT == LEGEND.end()) { continue; }
            blitTile(*TILESET, TILE_SIZE, IT->second.first, IT->second.second, pixels_, width_px_, col * TILE_SIZE, row * TILE_SIZE);
        }
    }

    std::cout << "Tilemap: " << COLS << "x" << ROWS << " tiles ("
              << width_px_ << "x" << height_px_ << " px) des de " << FULL << '\n';
}

void Tilemap::render() const {
    auto& screen = Screen::get();
    auto* canvas = screen.getCanvasArgb();
    const int CANVAS_W = screen.getCanvasWidth();
    const int CANVAS_H = screen.getCanvasHeight();

    // Clipping de files: només pintem les que cauen dins del canvas.
    const int Y_START = std::max(0, -origin_y_);
    const int Y_END = std::min(height_px_, CANVAS_H - origin_y_);
    const int X_START = std::max(0, -origin_x_);
    const int X_END = std::min(width_px_, CANVAS_W - origin_x_);

    // Màscara del canal alfa (els píxels transparents del tilemap queden
    // amb alpha=0 i cal mantenir el canvas sota visible).
    constexpr std::uint32_t ALPHA_MASK = 0xFF000000U;
    for (int y = Y_START; y < Y_END; ++y) {
        const auto* src_row = &pixels_[static_cast<std::size_t>(y) * static_cast<std::size_t>(width_px_)];
        auto* dst_row =
            &canvas[(static_cast<std::size_t>(origin_y_ + y) * static_cast<std::size_t>(CANVAS_W)) + static_cast<std::size_t>(origin_x_)];
        for (int x = X_START; x < X_END; ++x) {
            const auto PIXEL = src_row[x];
            if ((PIXEL & ALPHA_MASK) != 0U) { dst_row[x] = PIXEL; }
        }
    }
}