add doxygen comments + clean up

11 files changed, 189 insertions, 75 deletions

diff --git a/src/crepe/Resource.h b/src/crepe/Resource.h
index a0c8859..a2d65df 100644
--- a/src/crepe/Resource.h
+++ b/src/crepe/Resource.h
@@ -6,21 +6,19 @@ class ResourceManager;
 class Asset;
 
 /**
- * Resource is an interface class used to represent a (deserialized) game
- * resource (e.g. textures, sounds).
+ * \brief Resource interface
+ *
+ * Resource is an interface class used to represent a (deserialized) game resource (e.g.
+ * textures, sounds). Resources are always created from \ref Asset "assets" by ResourceManager.
+ *
+ * The game programmer has the ability to use the ResourceManager to keep instances of concrete
+ * resources between scenes, preventing them from being reinstantiated during a scene
+ * transition.
  */
 class Resource {
 public:
 	Resource(const Asset & src);
 	virtual ~Resource() = default;
-
-private:
-	/**
-	 * The resource manager uses \c clone to create new instances of the concrete
-	 * resource class. This may be used to inherit references to classes that
-	 * would otherwise need to be implemented as singletons.
-	 */
-	friend class ResourceManager;
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/AudioSource.h b/src/crepe/api/AudioSource.h
index 63b4bc4..330e8e1 100644
--- a/src/crepe/api/AudioSource.h
+++ b/src/crepe/api/AudioSource.h
@@ -17,16 +17,19 @@ class AudioSource : public Component {
 	friend class AudioSystem;
 
 protected:
+	/**
+	 * \param source Sound sample to load
+	 */
 	AudioSource(game_object_id_t id, const Asset & source);
-	//! Only ComponentManager can create components
+	//! Only ComponentManager creates components
 	friend class ComponentManager;
 
 public:
-	// But std::unique_ptr needs to be able to destoy this component again
+	// std::unique_ptr needs to be able to destoy this component
 	virtual ~AudioSource() = default;
 
 public:
-	//! Start or resume this audio source
+	//! Start this audio source
 	void play(bool looping = false);
 	//! Stop this audio source
 	void stop();
diff --git a/src/crepe/facade/Sound.cpp b/src/crepe/facade/Sound.cpp
index 33a0c47..ad50637 100644
--- a/src/crepe/facade/Sound.cpp
+++ b/src/crepe/facade/Sound.cpp
@@ -2,7 +2,6 @@
 #include "../util/Log.h"
 
 #include "Sound.h"
-#include "SoundContext.h"
 
 using namespace crepe;
 using namespace std;
@@ -12,36 +11,3 @@ Sound::Sound(const Asset & src) : Resource(src) {
 	dbg_trace();
 }
 Sound::~Sound() { dbg_trace(); }
-
-// void Sound::play(SoundContext & ctx) {
-// 	if (ctx.engine.getPause(this->handle)) {
-// 		// resume if paused
-// 		ctx.engine.setPause(this->handle, false);
-// 	} else {
-// 		// or start new sound
-// 		this->handle = ctx.engine.play(this->sample, this->volume);
-// 		ctx.engine.setLooping(this->handle, this->looping);
-// 	}
-// }
-//
-// void Sound::pause(SoundContext & ctx) {
-// 	if (ctx.engine.getPause(this->handle)) return;
-// 	ctx.engine.setPause(this->handle, true);
-// }
-//
-// void Sound::rewind(SoundContext & ctx) {
-// 	if (!ctx.engine.isValidVoiceHandle(this->handle)) return;
-// 	ctx.engine.seek(this->handle, 0);
-// }
-//
-// void Sound::set_volume(SoundContext & ctx, float volume) {
-// 	this->volume = volume;
-// 	if (!ctx.engine.isValidVoiceHandle(this->handle)) return;
-// 	ctx.engine.setVolume(this->handle, this->volume);
-// }
-//
-// void Sound::set_looping(SoundContext & ctx, bool looping) {
-// 	this->looping = looping;
-// 	if (!ctx.engine.isValidVoiceHandle(this->handle)) return;
-// 	ctx.engine.setLooping(this->handle, this->looping);
-// }
diff --git a/src/crepe/facade/Sound.h b/src/crepe/facade/Sound.h
index 35bccdb..a78a2a7 100644
--- a/src/crepe/facade/Sound.h
+++ b/src/crepe/facade/Sound.h
@@ -12,21 +12,24 @@ class SoundContext;
 /**
  * \brief Sound resource facade
  *
- * This class is a wrapper around a \c SoLoud::Wav instance, which holds a
- * single sample. It is part of the sound facade.
+ * This class is a wrapper around a \c SoLoud::Wav instance, which holds a single sample. It is
+ * part of the sound facade.
  */
 class Sound : public Resource {
 public:
 	Sound(const Asset & src);
 	~Sound(); // dbg_trace
 
+	//! Voice handle wrapper
 	struct Handle {
+		//! Voice handle (soloud), used by SoundContext
 		SoLoud::handle handle;
 	};
 
 private:
+	//! Deserialized resource (soloud)
 	SoLoud::Wav sample;
-
+	//! SoundContext uses \c sample
 	friend class SoundContext;
 };
 
diff --git a/src/crepe/facade/SoundContext.cpp b/src/crepe/facade/SoundContext.cpp
index 470b3cc..8bd7e74 100644
--- a/src/crepe/facade/SoundContext.cpp
+++ b/src/crepe/facade/SoundContext.cpp
@@ -17,17 +17,16 @@ SoundContext::~SoundContext() {
 
 Sound::Handle SoundContext::play(Sound & resource) {
 	return {
-		.handle = this->engine.play(resource.sample, this->default_volume),
+		.handle = this->engine.play(resource.sample, 1.0f),
 	};
 }
 
 void SoundContext::stop(Sound::Handle & handle) { this->engine.stop(handle.handle); }
 
-void SoundContext::set_volume(Sound & resource, Sound::Handle & handle, float volume) {
+void SoundContext::set_volume(Sound::Handle & handle, float volume) {
 	this->engine.setVolume(handle.handle, volume);
-	this->default_volume = volume;
 }
 
-void SoundContext::set_loop(Sound & resource, Sound::Handle & handle, bool loop) {
+void SoundContext::set_loop(Sound::Handle & handle, bool loop) {
 	this->engine.setLooping(handle.handle, loop);
 }
diff --git a/src/crepe/facade/SoundContext.h b/src/crepe/facade/SoundContext.h
index c651cd5..3bc8be5 100644
--- a/src/crepe/facade/SoundContext.h
+++ b/src/crepe/facade/SoundContext.h
@@ -11,8 +11,8 @@ namespace crepe {
 /**
  * \brief Sound engine facade
  *
- * This class is a wrapper around a \c SoLoud::Soloud instance, which provides
- * the methods for playing \c Sound instances. It is part of the sound facade.
+ * This class is a wrapper around a \c SoLoud::Soloud instance, which provides the methods for
+ * playing \c Sound instances. It is part of the sound facade.
  */
 class SoundContext {
 public:
@@ -24,15 +24,51 @@ public:
 	SoundContext & operator=(const SoundContext &) = delete;
 	SoundContext & operator=(SoundContext &&) = delete;
 
+	/**
+	 * \brief Play a sample
+	 *
+	 * Plays a Sound from the beginning of the sample and returns a handle to control it later.
+	 *
+	 * \param resource Sound instance to play
+	 *
+	 * \returns Handle to control this voice
+	 */
 	virtual Sound::Handle play(Sound & resource);
-	virtual void stop(Sound::Handle &);
-	virtual void set_volume(Sound &, Sound::Handle &, float);
-	virtual void set_loop(Sound &, Sound::Handle &, bool);
+	/**
+	 * \brief Stop a voice immediately if it is still playing
+	 *
+	 * \note This function does nothing if the handle is invalid or if the sound is already
+	 * stopped / finished playing.
+	 *
+	 * \param handle Voice handle returned by SoundContext::play
+	 */
+	virtual void stop(Sound::Handle & handle);
+	/**
+	 * \brief Change the volume of a voice
+	 *
+	 * \note This function does nothing if the handle is invalid or if the sound is already
+	 * stopped / finished playing.
+	 *
+	 * \param handle Voice handle returned by SoundContext::play
+	 * \param volume New gain value (0=silent, 1=default)
+	 */
+	virtual void set_volume(Sound::Handle & handle, float volume);
+	/**
+	 * \brief Set the looping behavior of a voice
+	 *
+	 * \note This function does nothing if the handle is invalid or if the sound is already
+	 * stopped / finished playing.
+	 *
+	 * \param handle Voice handle returned by SoundContext::play
+	 * \param loop Looping behavior (false=oneshot, true=loop)
+	 */
+	virtual void set_loop(Sound::Handle & handle, bool loop);
 
 private:
+	//! Abstracted class
 	SoLoud::Soloud engine;
-	float default_volume = 1.0f;
 
+	//! Config reference
 	Config & config = Config::get_instance();
 };
 
diff --git a/src/crepe/manager/ResourceManager.h b/src/crepe/manager/ResourceManager.h
index e7e6abc..84b275d 100644
--- a/src/crepe/manager/ResourceManager.h
+++ b/src/crepe/manager/ResourceManager.h
@@ -11,13 +11,11 @@
 namespace crepe {
 
 /**
- * \brief The ResourceManager is responsible for storing and managing assets over
- * multiple scenes.
+ * \brief Owner of concrete Resource instances
  * 
- * The ResourceManager ensures that assets are loaded once and can be accessed
- * across different scenes. It caches assets to avoid reloading them every time
- * a scene is loaded. Assets are retained in memory until the ResourceManager is
- * destroyed, at which point the cached assets are cleared.
+ * 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:
@@ -25,21 +23,53 @@ public:
 	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;
 	};
-	//! A cache that holds all the assets, accessible by their file path, over multiple scenes.
+	//! 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();
 };
 
diff --git a/src/crepe/system/AudioSystem.cpp b/src/crepe/system/AudioSystem.cpp
index 0696b34..26913c0 100644
--- a/src/crepe/system/AudioSystem.cpp
+++ b/src/crepe/system/AudioSystem.cpp
@@ -52,10 +52,10 @@ void AudioSystem::diff_update(AudioSource & component, ComponentPrivate & data,
 		component.oneshot_stop = false;
 	}
 	if (component.volume != data.last_volume) {
-		context.set_volume(resource, data.handle, component.volume);
+		context.set_volume(data.handle, component.volume);
 	}
 	if (component.loop != data.last_loop) {
-		context.set_loop(resource, data.handle, component.loop);
+		context.set_loop(data.handle, component.loop);
 	}
 }
 
diff --git a/src/crepe/system/AudioSystem.h b/src/crepe/system/AudioSystem.h
index c941470..4d21883 100644
--- a/src/crepe/system/AudioSystem.h
+++ b/src/crepe/system/AudioSystem.h
@@ -14,9 +14,7 @@ public:
 	void update() override;
 
 private:
-	/**
-	 * \brief Private data stored by AudioSystem on AudioSource component
-	 */
+	//! Private data stored by AudioSystem on AudioSource component
 	struct ComponentPrivate {
 		//! This sample's voice handle
 		Sound::Handle handle;
@@ -31,14 +29,39 @@ private:
 		//! \}
 	};
 
+	/**
+	 * \brief Update `last_*` members of \c data
+	 *
+	 * Copies all component properties stored for comparison between AudioSystem::update() calls
+	 *
+	 * \param component Source properties
+	 * \param data Destination properties
+	 */
 	void update_last(const AudioSource & component, ComponentPrivate & data);
 
+	/**
+	 * \brief Compare update component
+	 *
+	 * Compares properties of \c component and \c data, and calls SoundContext functions where
+	 * applicable.
+	 *
+	 * \param component AudioSource component to update
+	 * \param data AudioSource's private data
+	 * \param resource Sound instance for AudioSource's Asset
+	 */
 	void diff_update(AudioSource & component, ComponentPrivate & data, Sound & resource);
 
 protected:
+	/**
+	 * \brief Get SoundContext
+	 *
+	 * SoundContext is retrieved through this function instead of being a direct member of
+	 * AudioSystem to aid with testability.
+	 */
 	virtual SoundContext & get_context();
 
 private:
+	//! Actually stores SoundContext if the base AudioSystem::get_context implementation is used
 	Private context;
 };
 
diff --git a/src/crepe/util/Private.h b/src/crepe/util/Private.h
index 62a2e1a..d725a5e 100644
--- a/src/crepe/util/Private.h
+++ b/src/crepe/util/Private.h
@@ -5,26 +5,82 @@
 
 namespace crepe {
 
+/**
+ * \brief Utility for storing type hidden from user
+ *
+ * This class can be used to store types which cannot be used in the API directly due to header
+ * distribution limitations. This class is similar to `std::any`, but provides a method for
+ * retrieving a mutable reference to the stored object.
+ */
 class Private {
 public:
 	Private() = default;
 	~Private();
+	/**
+	 * \name Copy
+	 *
+	 * \note These functions do not do anything, resulting in `*this` being an empty (default)
+	 * instance.
+	 *
+	 * \{
+	 */
 	Private(const Private &);
-	Private(Private &&);
 	Private & operator=(const Private &);
+	//! \}
+	/**
+	 * \name Move
+	 *
+	 * These functions actually move the stored type if present.
+	 *
+	 * \{
+	 */
+	Private(Private &&);
 	Private & operator=(Private &&);
+	//! \}
 
+	/**
+	 * \brief Get the stored object
+	 *
+	 * \tparam T Type of stored object
+	 *
+	 * \returns Mutable reference to stored object
+	 *
+	 * \throws std::out_of_range if this instance does not contain any object
+	 * \throws std::logic_error if the stored type and requested type differ
+	 */
 	template <typename T>
-	T & get();
+	T & get() const;
 
+	/**
+	 * \brief Create and store an arbitrary object
+	 *
+	 * \tparam T Type of object
+	 * \tparam Args Perfect forwarding arguments
+	 * \param args Perfect forwarding arguments
+	 *
+	 * All arguments to this function are forwarded using `std::forward` to the constructor of T.
+	 *
+	 * \returns Mutable reference to stored object
+	 *
+	 * \note If this instance already contained an object, this function implicitly destroys the
+	 * previous object.
+	 */
 	template <typename T, typename... Args>
 	T & set(Args &&... args);
 
+	/**
+	 * \brief Check if this instance contains an object
+	 *
+	 * \returns `true` if this instance is empty, `false` if it contains an object
+	 */
 	bool empty() const noexcept;
 
 private:
+	//! Wrapper for destructor call of stored object type
 	std::function<void(void *)> destructor;
+	//! Stored object's type
 	std::type_index type = typeid(void);
+	//! Stored object
 	void * instance = nullptr;
 };
 
diff --git a/src/crepe/util/Private.hpp b/src/crepe/util/Private.hpp
index 3a87a9f..b2174c0 100644
--- a/src/crepe/util/Private.hpp
+++ b/src/crepe/util/Private.hpp
@@ -18,7 +18,7 @@ T & Private::set(Args &&... args) {
 }
 
 template <typename T>
-T & Private::get() {
+T & Private::get() const {
 	using namespace std;
 	if (this->empty()) throw out_of_range("Private: get() called on empty object");
 	type_index requested_type = typeid(T);