MetaCore/Source/MetaCoreScene/Private/MetaCoreScenePackage.cpp

#include "MetaCoreScene/MetaCoreScenePackage.h"

#include "MetaCoreFoundation/MetaCoreGeneratedReflection.h"
#include "MetaCoreFoundation/MetaCoreHash.h"
#include "MetaCoreFoundation/MetaCorePackage.h"
#include "MetaCoreFoundation/MetaCoreProject.h"

#include <fstream>
#include <sstream>

namespace MetaCore {

namespace {

[[nodiscard]] MetaCorePackageDocument MetaCoreBuildTypedScenePackage(
    const MetaCoreAssetGuid& assetGuid,
    const std::string& objectName,
    std::vector<std::byte> payload
) {
    MetaCorePackageDocument document;
    document.Header.PackageType = MetaCorePackageType::Scene;
    document.Header.PackageGuid = assetGuid;
    document.Header.SourceHash = MetaCoreHashBytes(std::span<const std::byte>(payload.data(), payload.size()));
    document.NameTable = {objectName, "MetaCoreSceneDocument"};
    document.Exports.push_back(MetaCoreExportEntry{
        assetGuid,
        objectName,
        MetaCoreMakeTypeId("MetaCoreSceneDocument"),
        0,
        static_cast<std::uint64_t>(payload.size())
    });
    document.PayloadSections.push_back(std::move(payload));
    return document;
}

template <typename T>
[[nodiscard]] std::optional<T> MetaCoreReadTypedPayload(
    const MetaCorePackageDocument& document,
    const MetaCoreTypeRegistry& registry,
    std::string_view expectedTypeName
) {
    if (document.Exports.empty() || document.PayloadSections.empty()) {
        return std::nullopt;
    }

    const MetaCoreExportEntry& exportEntry = document.Exports.front();
    if (exportEntry.TypeId != MetaCoreMakeTypeId(expectedTypeName) ||
        exportEntry.PayloadIndex >= document.PayloadSections.size()) {
        return std::nullopt;
    }

    T payload{};
    if (!MetaCoreDeserializeFromBytes(document.PayloadSections[exportEntry.PayloadIndex], payload, registry)) {
        return std::nullopt;
    }
    return payload;
}

[[nodiscard]] std::optional<std::string> MetaCoreFindJsonStringValue(std::string_view json, std::string_view key) {
    const std::string needle = "\"" + std::string(key) + "\"";
    std::size_t keyPosition = json.find(needle);
    if (keyPosition == std::string_view::npos) {
        return std::nullopt;
    }

    std::size_t colonPosition = json.find(':', keyPosition + needle.size());
    if (colonPosition == std::string_view::npos) {
        return std::nullopt;
    }

    std::size_t firstQuote = json.find('"', colonPosition + 1);
    if (firstQuote == std::string_view::npos) {
        return std::nullopt;
    }

    std::size_t secondQuote = firstQuote + 1;
    while (secondQuote < json.size()) {
        secondQuote = json.find('"', secondQuote);
        if (secondQuote == std::string_view::npos) {
            return std::nullopt;
        }
        if (secondQuote == firstQuote + 1 || json[secondQuote - 1] != '\\') {
            break;
        }
        ++secondQuote;
    }

    return std::string(json.substr(firstQuote + 1, secondQuote - firstQuote - 1));
}

}  // namespace

MetaCoreTypeRegistry MetaCoreBuildScenePackageTypeRegistry() {
    MetaCoreTypeRegistry registry;
    MetaCoreRegisterFoundationGeneratedTypes(registry);
    MetaCoreRegisterSceneGeneratedTypes(registry);
    return registry;
}

bool MetaCoreWriteScenePackage(
    const std::filesystem::path& path,
    const MetaCoreSceneDocument& document
) {
    const MetaCoreTypeRegistry registry = MetaCoreBuildScenePackageTypeRegistry();
    const auto payload = MetaCoreSerializeToBytes(document, registry);
    if (!payload.has_value()) {
        return false;
    }

    const std::string objectName = path.stem().string().empty() ? "Scene" : path.stem().string();
    MetaCorePackageDocument package = MetaCoreBuildTypedScenePackage(
        MetaCoreAssetGuid::Generate(),
        objectName,
        *payload
    );
    return MetaCoreWritePackageFile(path, std::move(package), registry);
}

std::optional<MetaCoreSceneDocument> MetaCoreReadScenePackage(const std::filesystem::path& path) {
    const MetaCoreTypeRegistry registry = MetaCoreBuildScenePackageTypeRegistry();
    const auto package = MetaCoreReadPackageFile(path, registry);
    if (!package.has_value() || package->Header.PackageType != MetaCorePackageType::Scene) {
        return std::nullopt;
    }
    return MetaCoreReadTypedPayload<MetaCoreSceneDocument>(*package, registry, "MetaCoreSceneDocument");
}

std::optional<std::filesystem::path> MetaCoreResolveStartupScenePackagePath(const std::filesystem::path& projectFilePath) {
    const auto projectDocument = MetaCoreReadProjectFile(projectFilePath);
    if (!projectDocument.has_value() || projectDocument->StartupScenePath.empty()) {
        return std::nullopt;
    }

    const std::filesystem::path relativeStartupScenePath = projectDocument->StartupScenePath.lexically_normal();
    const std::filesystem::path projectRoot = projectFilePath.parent_path();

    std::vector<std::filesystem::path> candidates;
    if (relativeStartupScenePath.extension() == ".json") {
        candidates.push_back((projectRoot / relativeStartupScenePath).replace_extension(""));
    }
    candidates.push_back(projectRoot / relativeStartupScenePath);

    for (const std::filesystem::path& candidate : candidates) {
        std::error_code errorCode;
        if (std::filesystem::exists(candidate, errorCode)) {
            return std::filesystem::weakly_canonical(candidate, errorCode);
        }
    }

    return (projectRoot / relativeStartupScenePath).lexically_normal();
}

std::optional<MetaCoreSceneDocument> MetaCoreLoadStartupSceneDocument(const std::filesystem::path& projectFilePath) {
    const auto startupScenePath = MetaCoreResolveStartupScenePackagePath(projectFilePath);
    if (!startupScenePath.has_value()) {
        return std::nullopt;
    }
    return MetaCoreReadScenePackage(*startupScenePath);
}

}  // namespace MetaCore