#include "MetaCoreFoundation/MetaCoreAssetRegistry.h"

#include <nlohmann/json.hpp>
#include <fstream>
#include <algorithm>

namespace MetaCore {

MetaCoreAssetRegistry& MetaCoreAssetRegistry::Get() {
    static MetaCoreAssetRegistry instance;
    return instance;
}

void MetaCoreAssetRegistry::ScanDirectory(const std::filesystem::path& rootPath) {
    if (!std::filesystem::exists(rootPath) || !std::filesystem::is_directory(rootPath)) {
        return;
    }

    // 遍历指定目录下的所有文件，寻找 .mcmeta 文件
    for (const auto& entry : std::filesystem::recursive_directory_iterator(rootPath)) {
        if (!entry.is_regular_file() || entry.path().extension() != ".mcmeta") {
            continue;
        }

        std::ifstream file(entry.path());
        if (!file.is_open()) {
            continue;
        }

        try {
            nlohmann::json json;
            file >> json;

            if (json.contains("guid") && json["guid"].is_string() &&
                json.contains("source_path") && json["source_path"].is_string()) {
                
                const std::string guidStr = json["guid"].get<std::string>();
                const std::string sourcePathStr = json["source_path"].get<std::string>();

                auto parsedGuid = MetaCoreAssetGuid::Parse(guidStr);
                if (parsedGuid.has_value()) {
                    // 规格化路径，确保斜杠在跨平台的一致性
                    std::filesystem::path portablePath(sourcePathStr);
                    RegisterAsset(*parsedGuid, portablePath);

                    // 顺便注册该主模型派生的所有子资产（如 mesh, material 等）
                    if (json.contains("sub_assets") && json["sub_assets"].is_array()) {
                        for (const auto& subAssetJson : json["sub_assets"]) {
                            if (subAssetJson.contains("guid") && subAssetJson["guid"].is_string()) {
                                const std::string subGuidStr = subAssetJson["guid"].get<std::string>();
                                auto parsedSubGuid = MetaCoreAssetGuid::Parse(subGuidStr);
                                if (parsedSubGuid.has_value()) {
                                    RegisterSubAsset(*parsedSubGuid, portablePath);
                                }
                            }
                        }
                    }
                }
            }
        } catch (...) {
            // 尝试作为二进制 mcmeta 包后备解析 (对标旧资源兼容)
            try {
                std::ifstream binFile(entry.path(), std::ios::binary);
                if (binFile.is_open()) {
                    char headerBytes[32];
                    if (binFile.read(headerBytes, 32)) {
                        std::uint32_t magic = 0;
                        std::uint32_t formatVersion = 0;
                        std::memcpy(&magic, headerBytes, 4);
                        std::memcpy(&formatVersion, headerBytes + 4, 4);

                        if (magic == 0x4D434F52U && formatVersion == 1U) {
                            MetaCoreAssetGuid packageGuid{};
                            std::memcpy(packageGuid.Bytes.data(), headerBytes + 16, 16);
                            if (packageGuid.IsValid()) {
                                std::filesystem::path mcmetaPath = entry.path();
                                std::filesystem::path sourceRelativePath = mcmetaPath.parent_path() / mcmetaPath.stem();
                                std::filesystem::path relativeToProject = sourceRelativePath.lexically_relative(rootPath.parent_path());
                                RegisterAsset(packageGuid, relativeToProject);
                            }
                        }
                    }
                }
            } catch (...) {
                // 彻底忽略损坏的文件
            }
        }
    }
}

bool MetaCoreAssetRegistry::RegisterAsset(const MetaCoreAssetGuid& guid, const std::filesystem::path& relativePath) {
    if (!guid.IsValid()) {
        return false;
    }

    UnregisterAsset(guid);
    const std::string keyPath = NormalizePathKey(relativePath);
    GuidToPath_[guid] = relativePath;
    PathToGuid_[keyPath] = guid;
    PrimaryAssetGuids_.insert(guid);
    return true;
}

bool MetaCoreAssetRegistry::RegisterSubAsset(const MetaCoreAssetGuid& guid, const std::filesystem::path& relativePath) {
    if (!guid.IsValid()) {
        return false;
    }
    UnregisterAsset(guid);
    GuidToPath_[guid] = relativePath;
    return true;
}

void MetaCoreAssetRegistry::UnregisterAsset(const MetaCoreAssetGuid& guid) {
    const auto iterator = GuidToPath_.find(guid);
    if (iterator == GuidToPath_.end()) {
        return;
    }

    const std::string keyPath = NormalizePathKey(iterator->second);
    if (const auto pathIterator = PathToGuid_.find(keyPath);
        pathIterator != PathToGuid_.end() && pathIterator->second == guid) {
        PathToGuid_.erase(pathIterator);
    }
    GuidToPath_.erase(iterator);
    PrimaryAssetGuids_.erase(guid);
}

bool MetaCoreAssetRegistry::MoveAsset(const MetaCoreAssetGuid& guid, const std::filesystem::path& newRelativePath) {
    if (!guid.IsValid() || !GuidToPath_.contains(guid)) {
        return false;
    }
    const bool isPrimaryAsset = PrimaryAssetGuids_.contains(guid);
    return isPrimaryAsset ? RegisterAsset(guid, newRelativePath) : RegisterSubAsset(guid, newRelativePath);
}

void MetaCoreAssetRegistry::Clear() {
    GuidToPath_.clear();
    PathToGuid_.clear();
    PrimaryAssetGuids_.clear();
}

std::filesystem::path MetaCoreAssetRegistry::ResolveGuidToPath(const MetaCoreAssetGuid& guid) const {
    const auto it = GuidToPath_.find(guid);
    if (it != GuidToPath_.end()) {
        return it->second;
    }
    return {};
}

MetaCoreAssetGuid MetaCoreAssetRegistry::ResolvePathToGuid(const std::filesystem::path& relativePath) const {
    const std::string keyPath = NormalizePathKey(relativePath);
    const auto it = PathToGuid_.find(keyPath);
    if (it != PathToGuid_.end()) {
        return it->second;
    }
    return {};
}

std::string MetaCoreAssetRegistry::NormalizePathKey(const std::filesystem::path& path) {
    std::string keyPath = path.lexically_normal().generic_string();
#if defined(_WIN32)
    std::transform(keyPath.begin(), keyPath.end(), keyPath.begin(), [](unsigned char value) {
        return value >= 'A' && value <= 'Z' ? static_cast<char>(value - 'A' + 'a') : static_cast<char>(value);
    });
#endif
    return keyPath;
}

bool MetaCoreAssetRegistry::HasAsset(const MetaCoreAssetGuid& guid) const {
    return GuidToPath_.count(guid) > 0;
}

}  // namespace MetaCore