#include "game/map/tilemap.hpp"

#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <iostream>
#include <stdexcept>
#include <vector>

#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 {

    // 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) {
    auto bytes = Resource::Helper::loadFile(yaml_path);
    if (bytes.empty()) {
        throw std::runtime_error("Tilemap: no s'ha pogut obrir " + yaml_path);
    }
    const auto* begin = reinterpret_cast<const char*>(bytes.data());
    const auto* end = begin + bytes.size();
    auto yaml = fkyaml::node::deserialize(begin, end);

    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 llegir `data` 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;

    // `data` és una seqüència de seqüències d'enters: cada fila és una
    // llista d'índexs lineals al tileset (esq→dre, dalt→baix). Un valor
    // negatiu (per convenció -1) deixa la cel·la buida (alpha=0).
    const auto& data = yaml["data"];
    if (!data.is_sequence() || data.empty()) {
        throw std::runtime_error("Tilemap: `data` buit o amb format incorrecte a " + yaml_path);
    }
    const int ROWS = static_cast<int>(data.size());
    const int COLS = static_cast<int>(data[0].size());
    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 = data[row];
        const int LINE_COLS = static_cast<int>(line.size());
        for (int col = 0; col < COLS && col < LINE_COLS; ++col) {
            const int INDEX = line[col].get_value<int>();
            if (INDEX < 0) { continue; }
            const int SRC_COL = INDEX % TILESET_COLS;
            const int SRC_ROW = INDEX / TILESET_COLS;
            blitTile(*TILESET, TILE_SIZE, SRC_COL, SRC_ROW, pixels_, width_px_, col * TILE_SIZE, row * TILE_SIZE);
        }
    }

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