#include "resource_pack.hpp"

#include <algorithm>
#include <cstring>
#include <filesystem>
#include <iostream>

namespace fs = std::filesystem;

ResourcePack::ResourcePack()
    : isLoaded_(false) {}

ResourcePack::~ResourcePack() {
    clear();
}

// ============================================================================
// EMPAQUETADO (herramienta pack_resources)
// ============================================================================

auto ResourcePack::addDirectory(const std::string& dir_path, const std::string& prefix) -> bool {
    if (!fs::exists(dir_path) || !fs::is_directory(dir_path)) {
        std::cerr << "Error: Directorio no existe: " << dir_path << '\n';
        return false;
    }

    for (const auto& entry : fs::recursive_directory_iterator(dir_path)) {
        if (entry.is_regular_file()) {
            // Construir ruta relativa desde data/ (ej: "data/ball.png" → "ball.png")
            std::string relative_path = fs::relative(entry.path(), dir_path).string();
            std::string full_path = prefix.empty() ? relative_path : prefix + "/" + relative_path;
            full_path = normalizePath(full_path);

            // Leer archivo completo
            std::ifstream file(entry.path(), std::ios::binary);
            if (!file) {
                std::cerr << "Error: No se pudo abrir: " << entry.path() << '\n';
                continue;
            }

            file.seekg(0, std::ios::end);
            size_t file_size = file.tellg();
            file.seekg(0, std::ios::beg);

            std::vector<unsigned char> buffer(file_size);
            file.read(reinterpret_cast<char*>(buffer.data()), file_size);
            file.close();

            // Crear entrada de recurso
            ResourceEntry resource;
            resource.path = full_path;
            resource.offset = 0;  // Se calculará al guardar
            resource.size = static_cast<uint32_t>(file_size);
            resource.checksum = calculateChecksum(buffer.data(), file_size);

            resources_[full_path] = resource;

            std::cout << "  Añadido: " << full_path << " (" << file_size << " bytes)" << '\n';
        }
    }

    return !resources_.empty();
}

auto ResourcePack::savePack(const std::string& pack_file_path) -> bool {
    std::ofstream pack_file(pack_file_path, std::ios::binary);
    if (!pack_file) {
        std::cerr << "Error: No se pudo crear pack: " << pack_file_path << '\n';
        return false;
    }

    // 1. Escribir header
    PackHeader header;
    std::memcpy(header.magic, "VBE3", 4);
    header.version = 1;
    header.fileCount = static_cast<uint32_t>(resources_.size());
    pack_file.write(reinterpret_cast<const char*>(&header), sizeof(PackHeader));

    // 2. Calcular offsets (después del header + índice)
    uint32_t current_offset = sizeof(PackHeader);

    // Calcular tamaño del índice (cada entrada: uint32_t pathLen + path + 3*uint32_t)
    for (const auto& [path, entry] : resources_) {
        current_offset += sizeof(uint32_t);                    // pathLen
        current_offset += static_cast<uint32_t>(path.size());  // path
        current_offset += sizeof(uint32_t) * 3;                // offset, size, checksum
    }

    // 3. Escribir índice
    for (auto& [path, entry] : resources_) {
        entry.offset = current_offset;

        auto path_len = static_cast<uint32_t>(path.size());
        pack_file.write(reinterpret_cast<const char*>(&path_len), sizeof(uint32_t));
        pack_file.write(path.c_str(), path_len);
        pack_file.write(reinterpret_cast<const char*>(&entry.offset), sizeof(uint32_t));
        pack_file.write(reinterpret_cast<const char*>(&entry.size), sizeof(uint32_t));
        pack_file.write(reinterpret_cast<const char*>(&entry.checksum), sizeof(uint32_t));

        current_offset += entry.size;
    }

    // 4. Escribir datos de archivos (sin encriptar en pack, se encripta al cargar)
    for (const auto& [path, entry] : resources_) {
        // Encontrar archivo original en disco
        fs::path original_path = fs::current_path() / "data" / path;
        std::ifstream file(original_path, std::ios::binary);
        if (!file) {
            std::cerr << "Error: No se pudo re-leer: " << original_path << '\n';
            continue;
        }

        std::vector<unsigned char> buffer(entry.size);
        file.read(reinterpret_cast<char*>(buffer.data()), entry.size);
        file.close();

        pack_file.write(reinterpret_cast<const char*>(buffer.data()), entry.size);
    }

    pack_file.close();
    return true;
}

// ============================================================================
// DESEMPAQUETADO (juego)
// ============================================================================

auto ResourcePack::loadPack(const std::string& pack_file_path) -> bool {
    clear();

    packFile_.open(pack_file_path, std::ios::binary);
    if (!packFile_) {
        return false;
    }

    // 1. Leer header
    PackHeader header;
    packFile_.read(reinterpret_cast<char*>(&header), sizeof(PackHeader));

    if (std::memcmp(header.magic, "VBE3", 4) != 0) {
        std::cerr << "Error: Pack inválido (magic incorrecto)" << '\n';
        packFile_.close();
        return false;
    }

    if (header.version != 1) {
        std::cerr << "Error: Versión de pack no soportada: " << header.version << '\n';
        packFile_.close();
        return false;
    }

    // 2. Leer índice
    for (uint32_t i = 0; i < header.fileCount; i++) {
        ResourceEntry entry;

        uint32_t path_len;
        packFile_.read(reinterpret_cast<char*>(&path_len), sizeof(uint32_t));

        std::vector<char> path_buffer(path_len + 1, '\0');
        packFile_.read(path_buffer.data(), path_len);
        entry.path = std::string(path_buffer.data());

        packFile_.read(reinterpret_cast<char*>(&entry.offset), sizeof(uint32_t));
        packFile_.read(reinterpret_cast<char*>(&entry.size), sizeof(uint32_t));
        packFile_.read(reinterpret_cast<char*>(&entry.checksum), sizeof(uint32_t));

        resources_[entry.path] = entry;
    }

    isLoaded_ = true;
    return true;
}

auto ResourcePack::loadResource(const std::string& resource_path) -> ResourcePack::ResourceData {
    ResourceData result = {.data = nullptr, .size = 0};

    if (!isLoaded_) {
        return result;
    }

    std::string normalized_path = normalizePath(resource_path);
    auto it = resources_.find(normalized_path);
    if (it == resources_.end()) {
        return result;
    }

    const ResourceEntry& entry = it->second;

    // Leer datos desde el pack
    packFile_.seekg(entry.offset);
    result.data = new unsigned char[entry.size];
    result.size = entry.size;
    packFile_.read(reinterpret_cast<char*>(result.data), entry.size);

    // Verificar checksum
    uint32_t checksum = calculateChecksum(result.data, entry.size);
    if (checksum != entry.checksum) {
        std::cerr << "Warning: Checksum incorrecto para: " << resource_path << '\n';
    }

    return result;
}

// ============================================================================
// UTILIDADES
// ============================================================================

auto ResourcePack::getResourceList() const -> std::vector<std::string> {
    std::vector<std::string> list;
    list.reserve(resources_.size());
    for (const auto& [path, entry] : resources_) {
        list.push_back(path);
    }
    return list;
}

auto ResourcePack::getResourceCount() const -> size_t {
    return resources_.size();
}

void ResourcePack::clear() {
    resources_.clear();
    if (packFile_.is_open()) {
        packFile_.close();
    }
    isLoaded_ = false;
}

// ============================================================================
// FUNCIONES AUXILIARES
// ============================================================================

auto ResourcePack::calculateChecksum(const unsigned char* data, size_t size) -> uint32_t {
    uint32_t checksum = 0;
    for (size_t i = 0; i < size; i++) {
        checksum ^= static_cast<uint32_t>(data[i]);
        checksum = (checksum << 1) | (checksum >> 31);  // Rotate left
    }
    return checksum;
}

auto ResourcePack::normalizePath(const std::string& path) -> std::string {
    std::string normalized = path;

    // Reemplazar \ por /
    std::ranges::replace(normalized, '\\', '/');

    // Buscar "data/" en cualquier parte del path y extraer lo que viene después
    size_t data_pos = normalized.find("data/");
    if (data_pos != std::string::npos) {
        normalized = normalized.substr(data_pos + 5);  // +5 para saltar "data/"
    }

    // Eliminar ./ del inicio si quedó
    if (normalized.substr(0, 2) == "./") {
        normalized = normalized.substr(2);
    }

    return normalized;
}