#include "MetaCoreFoundation/MetaCorePackage.h"

#include <fstream>

namespace MetaCore {

namespace {

[[nodiscard]] std::optional<std::vector<std::byte>> MetaCoreReadAllBytes(const std::filesystem::path& path) {
    std::ifstream input(path, std::ios::binary);
    if (!input.is_open()) {
        return std::nullopt;
    }

    input.seekg(0, std::ios::end);
    const auto size = static_cast<std::size_t>(input.tellg());
    input.seekg(0, std::ios::beg);

    std::vector<std::byte> bytes(size);
    if (size > 0 && !input.read(reinterpret_cast<char*>(bytes.data()), static_cast<std::streamsize>(size))) {
        return std::nullopt;
    }
    return bytes;
}

template <typename T>
[[nodiscard]] std::optional<std::vector<std::byte>> MetaCoreSerializeSection(
    const T& value,
    const MetaCoreTypeRegistry& registry
) {
    return MetaCoreSerializeToBytes(value, registry);
}

template <typename T>
[[nodiscard]] bool MetaCoreDeserializeSection(
    const MetaCorePackageSection& section,
    std::span<const std::byte> buffer,
    T& value,
    const MetaCoreTypeRegistry& registry
) {
    if (section.Offset + section.Size > buffer.size()) {
        return false;
    }

    return MetaCoreDeserializeFromBytes(
        buffer.subspan(static_cast<std::size_t>(section.Offset), static_cast<std::size_t>(section.Size)),
        value,
        registry
    );
}

}  // namespace

bool MetaCoreWritePackageFile(
    const std::filesystem::path& path,
    MetaCorePackageDocument document,
    const MetaCoreTypeRegistry& registry
) {
    const auto serializedNames = MetaCoreSerializeSection(document.NameTable, registry);
    const auto serializedImports = MetaCoreSerializeSection(document.Imports, registry);
    const auto serializedExports = MetaCoreSerializeSection(document.Exports, registry);
    const auto serializedDependencies = MetaCoreSerializeSection(document.Dependencies, registry);
    const auto serializedCustomVersions = MetaCoreSerializeSection(document.CustomVersions, registry);
    const auto serializedPayloads = MetaCoreSerializeSection(document.PayloadSections, registry);
    if (!serializedNames.has_value() ||
        !serializedImports.has_value() ||
        !serializedExports.has_value() ||
        !serializedDependencies.has_value() ||
        !serializedCustomVersions.has_value() ||
        !serializedPayloads.has_value()) {
        return false;
    }

    const auto provisionalHeaderBytes = MetaCoreSerializeToBytes(document.Header, registry);
    if (!provisionalHeaderBytes.has_value()) {
        return false;
    }

    std::uint64_t cursor = static_cast<std::uint64_t>(provisionalHeaderBytes->size());
    document.Header.NameTable = MetaCorePackageSection{cursor, static_cast<std::uint64_t>(serializedNames->size())};
    cursor += document.Header.NameTable.Size;
    document.Header.ImportTable = MetaCorePackageSection{cursor, static_cast<std::uint64_t>(serializedImports->size())};
    cursor += document.Header.ImportTable.Size;
    document.Header.ExportTable = MetaCorePackageSection{cursor, static_cast<std::uint64_t>(serializedExports->size())};
    cursor += document.Header.ExportTable.Size;
    document.Header.DependencyTable = MetaCorePackageSection{cursor, static_cast<std::uint64_t>(serializedDependencies->size())};
    cursor += document.Header.DependencyTable.Size;
    document.Header.CustomVersionTable = MetaCorePackageSection{cursor, static_cast<std::uint64_t>(serializedCustomVersions->size())};
    cursor += document.Header.CustomVersionTable.Size;
    document.Header.PayloadSections = MetaCorePackageSection{cursor, static_cast<std::uint64_t>(serializedPayloads->size())};
    cursor += document.Header.PayloadSections.Size;
    document.Header.FileSize = cursor;

    const auto finalHeaderBytes = MetaCoreSerializeToBytes(document.Header, registry);
    if (!finalHeaderBytes.has_value()) {
        return false;
    }

    std::filesystem::create_directories(path.parent_path());
    std::ofstream output(path, std::ios::binary | std::ios::trunc);
    if (!output.is_open()) {
        return false;
    }

    output.write(reinterpret_cast<const char*>(finalHeaderBytes->data()), static_cast<std::streamsize>(finalHeaderBytes->size()));
    output.write(reinterpret_cast<const char*>(serializedNames->data()), static_cast<std::streamsize>(serializedNames->size()));
    output.write(reinterpret_cast<const char*>(serializedImports->data()), static_cast<std::streamsize>(serializedImports->size()));
    output.write(reinterpret_cast<const char*>(serializedExports->data()), static_cast<std::streamsize>(serializedExports->size()));
    output.write(reinterpret_cast<const char*>(serializedDependencies->data()), static_cast<std::streamsize>(serializedDependencies->size()));
    output.write(reinterpret_cast<const char*>(serializedCustomVersions->data()), static_cast<std::streamsize>(serializedCustomVersions->size()));
    output.write(reinterpret_cast<const char*>(serializedPayloads->data()), static_cast<std::streamsize>(serializedPayloads->size()));
    return output.good();
}

std::optional<MetaCorePackageDocument> MetaCoreReadPackageFile(
    const std::filesystem::path& path,
    const MetaCoreTypeRegistry& registry
) {
    const auto bytes = MetaCoreReadAllBytes(path);
    if (!bytes.has_value()) {
        return std::nullopt;
    }

    MetaCorePackageDocument document;
    MetaCoreArchiveReader headerReader(std::span<const std::byte>(bytes->data(), bytes->size()));
    if (!MetaCoreDeserializeValue(headerReader, document.Header, registry)) {
        return std::nullopt;
    }

    if (document.Header.Magic != GMetaCorePackageMagic ||
        document.Header.FormatVersion != GMetaCorePackageFormatVersion ||
        document.Header.Endianness != MetaCorePackageEndianness::Little ||
        document.Header.FileSize != bytes->size()) {
        return std::nullopt;
    }

    const std::span<const std::byte> byteSpan(bytes->data(), bytes->size());
    if (!MetaCoreDeserializeSection(document.Header.NameTable, byteSpan, document.NameTable, registry) ||
        !MetaCoreDeserializeSection(document.Header.ImportTable, byteSpan, document.Imports, registry) ||
        !MetaCoreDeserializeSection(document.Header.ExportTable, byteSpan, document.Exports, registry) ||
        !MetaCoreDeserializeSection(document.Header.DependencyTable, byteSpan, document.Dependencies, registry) ||
        !MetaCoreDeserializeSection(document.Header.CustomVersionTable, byteSpan, document.CustomVersions, registry) ||
        !MetaCoreDeserializeSection(document.Header.PayloadSections, byteSpan, document.PayloadSections, registry)) {
        return std::nullopt;
    }

    return document;
}

}  // namespace MetaCore