5 files changed, 140 insertions, 0 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/Mediator.h b/src/crepe/manager/Mediator.h
index 71bd1c9..e9c10b1 100644
--- a/src/crepe/manager/Mediator.h
+++ b/src/crepe/manager/Mediator.h
@@ -10,6 +10,7 @@ namespace crepe {
 
 class ComponentManager;
 class SceneManager;
+class ResourceManager;
 
 /**
  * Struct to pass references to classes that would otherwise need to be singletons down to
@@ -28,6 +29,7 @@ struct Mediator {
 	OptionalRef<SceneManager> scene_manager;
 	OptionalRef<SaveManager> save_manager = SaveManager::get_instance();
 	OptionalRef<EventManager> event_manager = EventManager::get_instance();
+	OptionalRef<ResourceManager> resource_manager;
 };
 
 } // namespace crepe
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