10 files changed, 310 insertions, 67 deletions

diff --git a/src/crepe/manager/CMakeLists.txt b/src/crepe/manager/CMakeLists.txt
index 517b8a2..480c8ee 100644
--- a/src/crepe/manager/CMakeLists.txt
+++ b/src/crepe/manager/CMakeLists.txt
@@ -4,6 +4,7 @@ target_sources(crepe PUBLIC
 	Manager.cpp
 	SaveManager.cpp
 	SceneManager.cpp
+	ResourceManager.cpp
 )
 
 target_sources(crepe PUBLIC FILE_SET HEADERS FILES
@@ -16,5 +17,7 @@ target_sources(crepe PUBLIC FILE_SET HEADERS FILES
 	SaveManager.h
 	SceneManager.h
 	SceneManager.hpp
+	ResourceManager.h
+	ResourceManager.hpp
 )
 
diff --git a/src/crepe/manager/ComponentManager.cpp b/src/crepe/manager/ComponentManager.cpp
index 80cf8b4..df30d27 100644
--- a/src/crepe/manager/ComponentManager.cpp
+++ b/src/crepe/manager/ComponentManager.cpp
@@ -1,4 +1,5 @@
 #include "../api/GameObject.h"
+#include "../api/Metadata.h"
 #include "../types.h"
 #include "../util/Log.h"
 
@@ -61,3 +62,13 @@ GameObject ComponentManager::new_object(const string & name, const string & tag,
 void ComponentManager::set_persistent(game_object_id_t id, bool persistent) {
 	this->persistent[id] = persistent;
 }
+
+set<game_object_id_t> ComponentManager::get_objects_by_name(const string & name) const {
+	return this->get_objects_by_predicate<Metadata>(
+		[name](const Metadata & data) { return data.name == name; });
+}
+
+set<game_object_id_t> ComponentManager::get_objects_by_tag(const string & tag) const {
+	return this->get_objects_by_predicate<Metadata>(
+		[tag](const Metadata & data) { return data.tag == tag; });
+}
diff --git a/src/crepe/manager/ComponentManager.h b/src/crepe/manager/ComponentManager.h
index 44429d9..19a8e81 100644
--- a/src/crepe/manager/ComponentManager.h
+++ b/src/crepe/manager/ComponentManager.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <memory>
+#include <set>
 #include <typeindex>
 #include <unordered_map>
 #include <vector>
@@ -134,8 +135,77 @@ public:
 	 */
 	template <typename T>
 	RefVector<T> get_components_by_type() const;
+	/**
+	 * \brief Get all components of a specific type on a GameObject with name \c name
+	 * 
+	 * \tparam T The type of the component
+	 * \param name Metadata::name for the same game_object_id as the returned components
+	 * \return Components matching criteria
+	 */
+	template <typename T>
+	RefVector<T> get_components_by_name(const std::string & name) const;
+	/**
+	 * \brief Get all components of a specific type on a GameObject with tag \c tag
+	 * 
+	 * \tparam T The type of the component
+	 * \param name Metadata::tag for the same game_object_id as the returned components
+	 * \return Components matching criteria
+	 */
+	template <typename T>
+	RefVector<T> get_components_by_tag(const std::string & tag) const;
+
+private:
+	/**
+	 * \brief Get object IDs by predicate function
+	 *
+	 * This function calls the predicate function \c pred for all components matching type \c T,
+	 * and adds their parent game_object_id to a \c std::set if the predicate returns true.
+	 *
+	 * \tparam T The type of the component to check the predicate against
+	 * \param pred Predicate function
+	 *
+	 * \note The predicate function may be called for multiple components with the same \c
+	 * game_object_id. In this case, the ID is added if *any* call returns \c true.
+	 *
+	 * \returns game_object_id for all components where the predicate returned true
+	 */
+	template <typename T>
+	std::set<game_object_id_t>
+	get_objects_by_predicate(const std::function<bool(const T &)> & pred) const;
+
+	/**
+	 * \brief Get components of type \c T for multiple game object IDs
+	 *
+	 * \tparam T The type of the components to return
+	 * \param ids The object IDs
+	 *
+	 * \return All components matching type \c T and one of the IDs in \c ids
+	 */
+	template <typename T>
+	RefVector<T> get_components_by_ids(const std::set<game_object_id_t> & ids) const;
+
+	/**
+	 * \brief Get object IDs for objects with name \c name
+	 *
+	 * \param name Object name to match
+	 * \returns Object IDs where Metadata::name is equal to \c name
+	 */
+	std::set<game_object_id_t> get_objects_by_name(const std::string & name) const;
+	/**
+	 * \brief Get object IDs for objects with tag \c tag
+	 *
+	 * \param tag Object tag to match
+	 * \returns Object IDs where Metadata::tag is equal to \c tag
+	 */
+	std::set<game_object_id_t> get_objects_by_tag(const std::string & tag) const;
 
 private:
+	//! By Component \c std::type_index (readability helper type)
+	template <typename T>
+	using by_type = std::unordered_map<std::type_index, T>;
+	//! By \c game_object_id index (readability helper type)
+	template <typename T>
+	using by_id_index = std::vector<T>;
 	/**
 	 * \brief The components
 	 *
@@ -146,8 +216,7 @@ private:
 	 * The first vector is for the ids of the GameObjects and the second vector is for the
 	 * components (because a GameObject might have multiple components).
 	 */
-	std::unordered_map<std::type_index, std::vector<std::vector<std::unique_ptr<Component>>>>
-		components;
+	by_type<by_id_index<std::vector<std::unique_ptr<Component>>>> components;
 
 	//! Persistent flag for each GameObject
 	std::unordered_map<game_object_id_t, bool> persistent;
diff --git a/src/crepe/manager/ComponentManager.hpp b/src/crepe/manager/ComponentManager.hpp
index ffb38ec..9e70865 100644
--- a/src/crepe/manager/ComponentManager.hpp
+++ b/src/crepe/manager/ComponentManager.hpp
@@ -95,32 +95,25 @@ template <typename T>
 RefVector<T> ComponentManager::get_components_by_id(game_object_id_t id) const {
 	using namespace std;
 
-	// Determine the type of T (this is used as the key of the unordered_map<>)
-	type_index type = typeid(T);
-
-	// Create an empty vector<>
-	RefVector<T> component_vector;
-
-	if (this->components.find(type) == this->components.end()) return component_vector;
-
-	// Get the correct vector<>
-	const vector<vector<unique_ptr<Component>>> & component_array = this->components.at(type);
-
-	// Make sure that the id (that we are looking for) is within the boundaries of the vector<>
-	if (id >= component_array.size()) return component_vector;
-
-	// Loop trough the whole vector<>
-	for (const unique_ptr<Component> & component_ptr : component_array[id]) {
-		// Cast the unique_ptr to a raw pointer
-		T * casted_component = static_cast<T *>(component_ptr.get());
-
-		if (casted_component == nullptr) continue;
+	static_assert(is_base_of<Component, T>::value,
+				  "get_components_by_id must recieve a derivative class of Component");
 
-		// Add the dereferenced raw pointer to the vector<>
-		component_vector.push_back(*casted_component);
+	type_index type = typeid(T);
+	if (!this->components.contains(type)) return {};
+
+	const by_id_index<vector<unique_ptr<Component>>> & components_by_id
+		= this->components.at(type);
+	if (id >= components_by_id.size()) return {};
+
+	RefVector<T> out = {};
+	const vector<unique_ptr<Component>> & components = components_by_id.at(id);
+	for (auto & component_ptr : components) {
+		if (component_ptr == nullptr) continue;
+		Component & component = *component_ptr.get();
+		out.push_back(static_cast<T &>(component));
 	}
 
-	return component_vector;
+	return out;
 }
 
 template <typename T>
@@ -158,4 +151,46 @@ RefVector<T> ComponentManager::get_components_by_type() const {
 	return component_vector;
 }
 
+template <typename T>
+std::set<game_object_id_t>
+ComponentManager::get_objects_by_predicate(const std::function<bool(const T &)> & pred) const {
+	using namespace std;
+
+	set<game_object_id_t> objects = {};
+	RefVector<T> components = this->get_components_by_type<T>();
+
+	for (const T & component : components) {
+		game_object_id_t id = dynamic_cast<const Component &>(component).game_object_id;
+		if (objects.contains(id)) continue;
+		if (!pred(component)) continue;
+		objects.insert(id);
+	}
+
+	return objects;
+}
+
+template <typename T>
+RefVector<T>
+ComponentManager::get_components_by_ids(const std::set<game_object_id_t> & ids) const {
+	using namespace std;
+
+	RefVector<T> out = {};
+	for (game_object_id_t id : ids) {
+		RefVector<T> components = get_components_by_id<T>(id);
+		out.insert(out.end(), components.begin(), components.end());
+	}
+
+	return out;
+}
+
+template <typename T>
+RefVector<T> ComponentManager::get_components_by_name(const std::string & name) const {
+	return this->get_components_by_ids<T>(this->get_objects_by_name(name));
+}
+
+template <typename T>
+RefVector<T> ComponentManager::get_components_by_tag(const std::string & tag) const {
+	return this->get_components_by_ids<T>(this->get_objects_by_tag(tag));
+}
+
 } // namespace crepe
diff --git a/src/crepe/manager/Mediator.h b/src/crepe/manager/Mediator.h
index 8094d80..35ac181 100644
--- a/src/crepe/manager/Mediator.h
+++ b/src/crepe/manager/Mediator.h
@@ -5,13 +5,14 @@
 // TODO: remove these singletons:
 #include "../facade/SDLContext.h"
 #include "EventManager.h"
-#include "SaveManager.h"
 #include "api/LoopTimer.h"
 
 namespace crepe {
 
 class ComponentManager;
 class SceneManager;
+class SaveManager;
+class ResourceManager;
 
 /**
  * Struct to pass references to classes that would otherwise need to be singletons down to
@@ -28,8 +29,9 @@ class SceneManager;
 struct Mediator {
 	OptionalRef<ComponentManager> component_manager;
 	OptionalRef<SceneManager> scene_manager;
-	OptionalRef<SaveManager> save_manager = SaveManager::get_instance();
+	OptionalRef<SaveManager> save_manager;
 	OptionalRef<EventManager> event_manager = EventManager::get_instance();
+	OptionalRef<ResourceManager> resource_manager;
 	OptionalRef<SDLContext> sdl_context = SDLContext::get_instance();
 	OptionalRef<LoopTimer> timer = LoopTimer::get_instance();
 };
diff --git a/src/crepe/manager/ResourceManager.cpp b/src/crepe/manager/ResourceManager.cpp
new file mode 100644
index 0000000..7c01808
--- /dev/null
+++ b/src/crepe/manager/ResourceManager.cpp
@@ -0,0 +1,30 @@
+#include "util/Log.h"
+
+#include "ResourceManager.h"
+
+using namespace crepe;
+using namespace std;
+
+ResourceManager::ResourceManager(Mediator & mediator) : Manager(mediator) {
+	mediator.resource_manager = *this;
+	dbg_trace();
+}
+ResourceManager::~ResourceManager() { dbg_trace(); }
+
+void ResourceManager::clear() {
+	std::erase_if(this->resources, [](const pair<const Asset, CacheEntry> & pair) {
+		const CacheEntry & entry = pair.second;
+		return entry.persistent == false;
+	});
+}
+
+void ResourceManager::clear_all() { this->resources.clear(); }
+
+void ResourceManager::set_persistent(const Asset & asset, bool persistent) {
+	this->get_entry(asset).persistent = persistent;
+}
+
+ResourceManager::CacheEntry & ResourceManager::get_entry(const Asset & asset) {
+	if (!this->resources.contains(asset)) this->resources[asset] = {};
+	return this->resources.at(asset);
+}
diff --git a/src/crepe/manager/ResourceManager.h b/src/crepe/manager/ResourceManager.h
new file mode 100644
index 0000000..84b275d
--- /dev/null
+++ b/src/crepe/manager/ResourceManager.h
@@ -0,0 +1,78 @@
+#pragma once
+
+#include <memory>
+#include <unordered_map>
+
+#include "../Resource.h"
+#include "../api/Asset.h"
+
+#include "Manager.h"
+
+namespace crepe {
+
+/**
+ * \brief Owner of concrete Resource instances
+ * 
+ * ResourceManager caches concrete Resource instances per Asset. Concrete resources are
+ * destroyed at the end of scenes by default, unless the game programmer marks them as
+ * persistent.
+ */
+class ResourceManager : public Manager {
+public:
+	ResourceManager(Mediator & mediator);
+	virtual ~ResourceManager(); // dbg_trace
+
+private:
+	//! Cache entry
+	struct CacheEntry {
+		//! Concrete resource instance
+		std::unique_ptr<Resource> resource = nullptr;
+		//! Prevent ResourceManager::clear from removing this entry
+		bool persistent = false;
+	};
+	//! Internal cache
+	std::unordered_map<const Asset, CacheEntry> resources;
+	/**
+	 * \brief Ensure a cache entry exists for this asset and return a mutable reference to it
+	 *
+	 * \param asset Asset the concrete resource is instantiated from
+	 *
+	 * \returns Mutable reference to cache entry
+	 */
+	CacheEntry & get_entry(const Asset & asset);
+
+public:
+	/**
+	 * \brief Mark a resource as persistent (i.e. used across multiple scenes)
+	 *
+	 * \param asset Asset the concrete resource is instantiated from
+	 * \param persistent Whether this resource is persistent (true=keep, false=destroy)
+	 */
+	void set_persistent(const Asset & asset, bool persistent);
+
+	/**
+	 * \brief Retrieve reference to concrete Resource by Asset
+	 *
+	 * \param asset Asset the concrete resource is instantiated from
+	 * \tparam Resource Concrete derivative of Resource
+	 *
+	 * This class instantiates the concrete resource if it is not yet stored in the internal
+	 * cache, or returns a reference to the cached resource if it already exists.
+	 *
+	 * \returns Reference to concrete resource
+	 *
+	 * \throws std::runtime_error if the \c Resource parameter does not match with the actual
+	 * type of the resource stored in the cache for this Asset
+	 */
+	template <typename Resource>
+	Resource & get(const Asset & asset);
+
+	//! Clear non-persistent resources from cache
+	void clear();
+	//! Clear all resources from cache regardless of persistence
+	void clear_all();
+};
+
+} // namespace crepe
+
+#include "ResourceManager.hpp"
diff --git a/src/crepe/manager/ResourceManager.hpp b/src/crepe/manager/ResourceManager.hpp
new file mode 100644
index 0000000..5167d71
--- /dev/null
+++ b/src/crepe/manager/ResourceManager.hpp
@@ -0,0 +1,27 @@
+#pragma once
+
+#include <format>
+
+#include "ResourceManager.h"
+
+namespace crepe {
+
+template <typename T>
+T & ResourceManager::get(const Asset & asset) {
+	using namespace std;
+	static_assert(is_base_of<Resource, T>::value,
+				  "cache must recieve a derivative class of Resource");
+
+	CacheEntry & entry = this->get_entry(asset);
+	if (entry.resource == nullptr) entry.resource = make_unique<T>(asset);
+
+	T * concrete_resource = dynamic_cast<T *>(entry.resource.get());
+	if (concrete_resource == nullptr)
+		throw runtime_error(format("ResourceManager: mismatch between requested type and "
+								   "actual type of resource ({})",
+								   asset.get_path()));
+
+	return *concrete_resource;
+}
+
+} // namespace crepe
diff --git a/src/crepe/manager/SaveManager.cpp b/src/crepe/manager/SaveManager.cpp
index d4ed1c1..39b92d4 100644
--- a/src/crepe/manager/SaveManager.cpp
+++ b/src/crepe/manager/SaveManager.cpp
@@ -1,13 +1,27 @@
 #include "../ValueBroker.h"
 #include "../api/Config.h"
 #include "../facade/DB.h"
-#include "../util/Log.h"
 
 #include "SaveManager.h"
 
 using namespace std;
 using namespace crepe;
 
+SaveManager::SaveManager(Mediator & mediator) : Manager(mediator) {
+	mediator.save_manager = *this;
+}
+
+DB & SaveManager::get_db() {
+	if (this->db == nullptr) {
+		Config & cfg = Config::get_instance();
+		this->db = {
+			new DB(cfg.savemgr.location),
+			[](void * db){ delete static_cast<DB *>(db); }
+		};
+	}
+	return *static_cast<DB *>(this->db.get());
+}
+
 template <>
 string SaveManager::serialize(const string & value) const noexcept {
 	return value;
@@ -90,22 +104,6 @@ int32_t SaveManager::deserialize(const string & value) const noexcept {
 	return deserialize<int64_t>(value);
 }
 
-SaveManager::SaveManager() { dbg_trace(); }
-
-SaveManager & SaveManager::get_instance() {
-	dbg_trace();
-	static SaveManager instance;
-	return instance;
-}
-
-DB & SaveManager::get_db() {
-	Config & cfg = Config::get_instance();
-	// TODO: make this path relative to XDG_DATA_HOME on Linux and whatever the
-	// default equivalent is on Windows using some third party library
-	static DB db(cfg.savemgr.location);
-	return db;
-}
-
 bool SaveManager::has(const string & key) {
 	DB & db = this->get_db();
 	return db.has(key);
@@ -155,7 +153,8 @@ ValueBroker<T> SaveManager::get(const string & key) {
 	return {
 		[this, key](const T & target) { this->set<T>(key, target); },
 		[this, key, value]() mutable -> const T & {
-			value = this->deserialize<T>(this->get_db().get(key));
+			DB & db = this->get_db();
+			value = this->deserialize<T>(db.get(key));
 			return value;
 		},
 	};
diff --git a/src/crepe/manager/SaveManager.h b/src/crepe/manager/SaveManager.h
index 3d8c852..27e625c 100644
--- a/src/crepe/manager/SaveManager.h
+++ b/src/crepe/manager/SaveManager.h
@@ -1,9 +1,12 @@
 #pragma once
 
 #include <memory>
+#include <functional>
 
 #include "../ValueBroker.h"
 
+#include "Manager.h"
+
 namespace crepe {
 
 class DB;
@@ -18,7 +21,7 @@ class DB;
  *
  * The underlying database is a key-value store.
  */
-class SaveManager {
+class SaveManager : public Manager {
 public:
 	/**
 	 * \brief Get a read/write reference to a value and initialize it if it does not yet exist
@@ -63,8 +66,8 @@ public:
 	 */
 	bool has(const std::string & key);
 
-private:
-	SaveManager();
+public:
+	SaveManager(Mediator & mediator);
 	virtual ~SaveManager() = default;
 
 private:
@@ -89,26 +92,12 @@ private:
 	template <typename T>
 	T deserialize(const std::string & value) const noexcept;
 
-public:
-	// singleton
-	static SaveManager & get_instance();
-	SaveManager(const SaveManager &) = delete;
-	SaveManager(SaveManager &&) = delete;
-	SaveManager & operator=(const SaveManager &) = delete;
-	SaveManager & operator=(SaveManager &&) = delete;
-
+protected:
+	//! Create or return DB
+	virtual DB & get_db();
 private:
-	/**
-	 * \brief Create an instance of DB and return its reference
-	 *
-	 * \returns DB instance
-	 *
-	 * This function exists because DB is a facade class, which can't directly be used in the API
-	 * without workarounds
-	 *
-	 * TODO: better solution
-	 */
-	static DB & get_db();
+	//! Database
+	std::unique_ptr<void, std::function<void(void*)>> db = nullptr;
 };
 
 } // namespace crepe