feat: add prefabs

destrum/include/destrum/Scene/Scene.h

@@ -27,11 +27,13 @@ struct SceneEnvironment {
     float skyboxRotation{0.0f};
 };
 class SceneSerializer;
+class PrefabSerializer;
 class PhysicsWorld;
 
 class Scene final {
     friend Scene& SceneManager::CreateScene(const std::string& name);
     friend class SceneSerializer;
+    friend class PrefabSerializer;
 
 public:
     // void Add(std::shared_ptr<GameObject> object);

destrum/include/destrum/Serialization/ObjectSerialization.h

@@ -0,0 +1,44 @@
+#ifndef DESTRUM_OBJECTSERIALIZATION_H
+#define DESTRUM_OBJECTSERIALIZATION_H
+
+#include <filesystem>
+#include <optional>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#include <nlohmann/json.hpp>
+
+#include <destrum/ObjectModel/ObjectId.h>
+
+class GameObject;
+class Scene;
+
+namespace ObjectSerialization {
+    using ObjectMap = std::unordered_map<ObjectId, GameObject*>;
+    using ValidationError = std::optional<std::string>;
+
+    constexpr int CurrentObjectVersion = 2;
+
+    [[nodiscard]] std::optional<std::string> FindNonFinite(const nlohmann::json& value, const std::string& path);
+
+    [[nodiscard]] ValidationError ValidateObjects(const nlohmann::json& objects, int version);
+
+    void WarnMissingAssets(const nlohmann::json& objects, const std::filesystem::path& source);
+
+    [[nodiscard]] nlohmann::json SerializeObjects(const std::vector<const GameObject*>& objects);
+
+    [[nodiscard]] std::vector<const GameObject*> CollectHierarchy(const GameObject& root);
+
+    struct BuiltObjects {
+        std::vector<GameObject*> objects;
+        ObjectMap idMap;
+    };
+
+    [[nodiscard]] BuiltObjects BuildObjects(Scene& scene, const nlohmann::json& objects,
+                                            const ObjectMap& externalObjects = {});
+
+    [[nodiscard]] bool WriteFileAtomically(const std::filesystem::path& path, const std::string& contents);
+}
+
+#endif //DESTRUM_OBJECTSERIALIZATION_H

destrum/include/destrum/Serialization/PrefabCache.h

@@ -0,0 +1,37 @@
+#ifndef DESTRUM_PREFABCACHE_H
+#define DESTRUM_PREFABCACHE_H
+
+#include <filesystem>
+#include <memory>
+#include <string>
+#include <string_view>
+#include <unordered_map>
+
+#include <nlohmann/json.hpp>
+
+#include <destrum/Singleton.h>
+
+class PrefabCache final : public Singleton<PrefabCache> {
+    friend class Singleton<PrefabCache>;
+
+public:
+    [[nodiscard]] std::shared_ptr<const nlohmann::json> Get(std::string_view path);
+    void Invalidate(const std::filesystem::path& path);
+    void Clear();
+
+    [[nodiscard]] static std::filesystem::path ResolvePath(std::string_view path);
+
+private:
+    PrefabCache() = default;
+
+    struct Entry {
+        std::shared_ptr<const nlohmann::json> prefab;
+        std::filesystem::file_time_type writeTime;
+    };
+
+    [[nodiscard]] static std::string MakeKey(const std::filesystem::path& path);
+
+    std::unordered_map<std::string, Entry> m_Prefabs;
+};
+
+#endif //DESTRUM_PREFABCACHE_H

destrum/include/destrum/Serialization/PrefabSerializer.h

@@ -0,0 +1,31 @@
+#ifndef DESTRUM_PREFABSERIALIZER_H
+#define DESTRUM_PREFABSERIALIZER_H
+
+#include <filesystem>
+#include <optional>
+#include <string>
+#include <string_view>
+
+#include <nlohmann/json.hpp>
+
+class GameObject;
+class Scene;
+class Transform;
+
+class PrefabSerializer final {
+public:
+    static constexpr int CurrentPrefabVersion = 1;
+
+    [[nodiscard]] static std::optional<nlohmann::json> Capture(const GameObject& root);
+    static bool Save(const GameObject& root, const std::filesystem::path& path);
+
+    [[nodiscard]] static std::optional<nlohmann::json> LoadFile(const std::filesystem::path& path);
+    [[nodiscard]] static std::optional<std::string> Validate(const nlohmann::json& prefab);
+
+    static GameObject* InstantiateFromJson(Scene& scene, const nlohmann::json& prefab, Transform* parent = nullptr);
+    static GameObject* Instantiate(Scene& scene, std::string_view path, Transform* parent = nullptr);
+
+    static GameObject* Duplicate(GameObject& object);
+};
+
+#endif //DESTRUM_PREFABSERIALIZER_H