pollo/source/core/resources/resource_pack.cpp

// resource_pack.cpp
// Resource pack implementation for Los Pollos Hermanos

#include "resource_pack.hpp"

#include <algorithm>
#include <filesystem>
#include <fstream>
#include <iostream>

namespace Resource {

// Calculate CRC32 checksum for data verification
auto Pack::calculateChecksum(const std::vector<uint8_t>& data) -> uint32_t {
    uint32_t checksum = 0x12345678;
    for (unsigned char byte : data) {
        checksum = ((checksum << 5) + checksum) + byte;
    }
    return checksum;
}

// XOR encryption (symmetric - same function for encrypt/decrypt)
void Pack::encryptData(std::vector<uint8_t>& data, const std::string& key) {
    if (key.empty()) {
        return;
    }
    for (size_t i = 0; i < data.size(); ++i) {
        data[i] ^= key[i % key.length()];
    }
}

void Pack::decryptData(std::vector<uint8_t>& data, const std::string& key) {
    // XOR is symmetric
    encryptData(data, key);
}

// Read entire file into memory
auto Pack::readFile(const std::string& filepath) -> std::vector<uint8_t> {
    std::ifstream file(filepath, std::ios::binary | std::ios::ate);
    if (!file) {
        std::cerr << "ResourcePack: Failed to open file: " << filepath << '\n';
        return {};
    }

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

    std::vector<uint8_t> data(file_size);
    if (!file.read(reinterpret_cast<char*>(data.data()), file_size)) {
        std::cerr << "ResourcePack: Failed to read file: " << filepath << '\n';
        return {};
    }

    return data;
}

// Add a single file to the pack
auto Pack::addFile(const std::string& filepath, const std::string& pack_name)
    -> bool {
    auto file_data = readFile(filepath);
    if (file_data.empty()) {
        return false;
    }

    ResourceEntry entry{
        .filename = pack_name,
        .offset = data_.size(),
        .size = file_data.size(),
        .checksum = calculateChecksum(file_data)};

    // Append file data to the data block
    data_.insert(data_.end(), file_data.begin(), file_data.end());

    resources_[pack_name] = entry;

    std::cout << "Added: " << pack_name << " (" << file_data.size() << " bytes)\n";
    return true;
}

// Add all files from a directory recursively
auto Pack::addDirectory(const std::string& dir_path,
    const std::string& base_path) -> bool {
    namespace fs = std::filesystem;

    if (!fs::exists(dir_path) || !fs::is_directory(dir_path)) {
        std::cerr << "ResourcePack: Directory not found: " << dir_path << '\n';
        return false;
    }

    std::string current_base = base_path.empty() ? "" : base_path + "/";

    for (const auto& entry : fs::recursive_directory_iterator(dir_path)) {
        if (!entry.is_regular_file()) {
            continue;
        }

        std::string full_path = entry.path().string();
        std::string relative_path = entry.path().lexically_relative(dir_path).string();

        // Convert backslashes to forward slashes (Windows compatibility)
        std::ranges::replace(relative_path, '\\', '/');

        // Skip development files
        if (relative_path.find(".world") != std::string::npos ||
            relative_path.find(".tsx") != std::string::npos) {
            std::cout << "Skipping development file: " << relative_path << '\n';
            continue;
        }

        std::string pack_name = current_base + relative_path;
        addFile(full_path, pack_name);
    }

    return true;
}

// Save the pack to a file
auto Pack::savePack(const std::string& pack_file) -> bool {
    std::ofstream file(pack_file, std::ios::binary);
    if (!file) {
        std::cerr << "ResourcePack: Failed to create pack file: " << pack_file << '\n';
        return false;
    }

    // Write header
    file.write(MAGIC_HEADER.data(), MAGIC_HEADER.size());
    file.write(reinterpret_cast<const char*>(&VERSION), sizeof(VERSION));

    // Write resource count
    auto resource_count = static_cast<uint32_t>(resources_.size());
    file.write(reinterpret_cast<const char*>(&resource_count), sizeof(resource_count));

    // Write resource entries
    for (const auto& [name, entry] : resources_) {
        // Write filename length and name
        auto name_len = static_cast<uint32_t>(entry.filename.length());
        file.write(reinterpret_cast<const char*>(&name_len), sizeof(name_len));
        file.write(entry.filename.c_str(), name_len);

        // Write offset, size, checksum
        file.write(reinterpret_cast<const char*>(&entry.offset), sizeof(entry.offset));
        file.write(reinterpret_cast<const char*>(&entry.size), sizeof(entry.size));
        file.write(reinterpret_cast<const char*>(&entry.checksum), sizeof(entry.checksum));
    }

    // Encrypt data
    std::vector<uint8_t> encrypted_data = data_;
    encryptData(encrypted_data, DEFAULT_ENCRYPT_KEY);

    // Write encrypted data size and data
    uint64_t data_size = encrypted_data.size();
    file.write(reinterpret_cast<const char*>(&data_size), sizeof(data_size));
    file.write(reinterpret_cast<const char*>(encrypted_data.data()), data_size);

    std::cout << "\nPack saved successfully: " << pack_file << '\n';
    std::cout << "Resources: " << resource_count << '\n';
    std::cout << "Total size: " << data_size << " bytes\n";

    return true;
}

// Load a pack from a file
auto Pack::loadPack(const std::string& pack_file) -> bool {
    std::ifstream file(pack_file, std::ios::binary);
    if (!file) {
        std::cerr << "ResourcePack: Failed to open pack file: " << pack_file << '\n';
        return false;
    }

    // Read and verify header
    std::array<char, 4> header{};
    file.read(header.data(), header.size());
    if (header != MAGIC_HEADER) {
        std::cerr << "ResourcePack: Invalid pack header\n";
        return false;
    }

    // Read and verify version
    uint32_t version = 0;
    file.read(reinterpret_cast<char*>(&version), sizeof(version));
    if (version != VERSION) {
        std::cerr << "ResourcePack: Unsupported pack version: " << version << '\n';
        return false;
    }

    // Read resource count
    uint32_t resource_count = 0;
    file.read(reinterpret_cast<char*>(&resource_count), sizeof(resource_count));

    // Read resource entries
    resources_.clear();
    for (uint32_t i = 0; i < resource_count; ++i) {
        // Read filename
        uint32_t name_len = 0;
        file.read(reinterpret_cast<char*>(&name_len), sizeof(name_len));

        std::string filename(name_len, '\0');
        file.read(filename.data(), name_len);

        // Read entry data
        ResourceEntry entry{};
        entry.filename = filename;
        file.read(reinterpret_cast<char*>(&entry.offset), sizeof(entry.offset));
        file.read(reinterpret_cast<char*>(&entry.size), sizeof(entry.size));
        file.read(reinterpret_cast<char*>(&entry.checksum), sizeof(entry.checksum));

        resources_[filename] = entry;
    }

    // Read encrypted data
    uint64_t data_size = 0;
    file.read(reinterpret_cast<char*>(&data_size), sizeof(data_size));

    data_.resize(data_size);
    file.read(reinterpret_cast<char*>(data_.data()), data_size);

    // Decrypt data
    decryptData(data_, DEFAULT_ENCRYPT_KEY);

    loaded_ = true;

    std::cout << "ResourcePack loaded: " << pack_file << '\n';
    std::cout << "Resources: " << resource_count << '\n';
    std::cout << "Data size: " << data_size << " bytes\n";

    return true;
}

// Get a resource by name
auto Pack::getResource(const std::string& filename) -> std::vector<uint8_t> {
    auto it = resources_.find(filename);
    if (it == resources_.end()) {
        return {};
    }

    const ResourceEntry& entry = it->second;

    // Extract data slice
    if (entry.offset + entry.size > data_.size()) {
        std::cerr << "ResourcePack: Invalid offset/size for: " << filename << '\n';
        return {};
    }

    std::vector<uint8_t> result(data_.begin() + entry.offset,
        data_.begin() + entry.offset + entry.size);

    // Verify checksum
    uint32_t checksum = calculateChecksum(result);
    if (checksum != entry.checksum) {
        std::cerr << "ResourcePack: Checksum mismatch for: " << filename << '\n';
        std::cerr << "  Expected: 0x" << std::hex << entry.checksum << '\n';
        std::cerr << "  Got: 0x" << std::hex << checksum << std::dec << '\n';
    }

    return result;
}

// Check if a resource exists
auto Pack::hasResource(const std::string& filename) const -> bool {
    return resources_.find(filename) != resources_.end();
}

// Get list of all resources
auto Pack::getResourceList() const -> std::vector<std::string> {
    std::vector<std::string> list;
    list.reserve(resources_.size());
    for (const auto& [name, entry] : resources_) {
        list.push_back(name);
    }
    std::ranges::sort(list);
    return list;
}

// Calculate overall pack checksum for validation
auto Pack::calculatePackChecksum() const -> uint32_t {
    if (!loaded_ || data_.empty()) {
        return 0;
    }

    // Combine checksums of all resources for a global checksum
    uint32_t global_checksum = 0x87654321;

    // Sort resources by name for deterministic checksum
    std::vector<std::string> sorted_names;
    sorted_names.reserve(resources_.size());
    for (const auto& [name, entry] : resources_) {
        sorted_names.push_back(name);
    }
    std::ranges::sort(sorted_names);

    // Combine individual checksums
    for (const auto& name : sorted_names) {
        const auto& entry = resources_.at(name);
        global_checksum = ((global_checksum << 5) + global_checksum) + entry.checksum;
        global_checksum = ((global_checksum << 5) + global_checksum) + entry.size;
    }

    return global_checksum;
}

}  // namespace Resource