SHADE_Y3/SHADE_Engine/src/Events/SHEventManager.h

/******************************************************************************
 * \file    SHEventManager.h
 * \author  Loh Xiao Qi
 * \brief   Class declaration for event manager.
 * 
 * \copyright Copyright (c) 2021 Digipen Institute of Technology. Reproduction
 * or disclosure of this file or its contents without the prior written consent
 * of Digipen Institute of Technology is prohibited.
******************************************************************************/
#ifndef SH_EVENT_MANAGER_H
#define SH_EVENT_MANAGER_H

#include "SHEvent.h"
#include "SHEventReceiver.h"
#include <unordered_map>
#include <functional>

namespace SHADE
{
	using ResponseFunction = std::function<void(SHEvent)>;
	using ReceiverPtr = std::shared_ptr<SHEventReceiver>;
	using ResponseVec = std::vector<ReceiverPtr>;
	using StaticResponseVec = std::vector<ResponseFunction>;

	using EventManagerListener = std::function<void(SHEvent)>;

	class SHEventManager
	{
	public:
		/****************************************************************************
		 * \brief		Ctor and Dtor. Dtor will delete instance of self stored at
		 *					data member instance.
		****************************************************************************/
		SHEventManager();

		/****************************************************************************
		 * \brief   Returns singleton instance of event manager in heap memory. If
		 *					instance does not exist, one is created immediately.
		****************************************************************************/
		static SHEventManager& GetEventManagerInstance();

		/****************************************************************************
		 * \brief   Returns function pointer to entry point for events.
		****************************************************************************/
		static EventManagerListener GetListenerFunction();

		/****************************************************************************
		 * \brief   Exit function to terminate the manager properly and deallocate
		 *					memory.
		****************************************************************************/
		static void Exit();

		/****************************************************************************
		 * \param   ListenerConstPtr - Const pointer to listener that sent event.
		 * \param   EventType - Templated type for every type of event

		 * \brief		Receives event from the listeners.
		****************************************************************************/
		static void CatchEvent(SHEvent);

		/****************************************************************************
		 * \param   ResponseFunction - function pointer from receiver to be passed
		 *					into event manager to be called when events are broadcasted.
		 * \param   SHPackageType - package type that corresponding subscriber is
		 *					subscribing to.
		
		 * \brief   Links a function pointer from a subscriber to a particular
		 *					package type
		****************************************************************************/
		void SubscribeTo(SHEventIdentifier, ReceiverPtr);

		template<typename T>
		T* BroadcastData(T data, SHEventIdentifier eventType);
	private:
		// Singleton instance
		static SHEventManager* instance;

		// Registry for broadcasters and subscribers
		std::unordered_map<SHEventIdentifier,	ResponseVec> packageReceiverRegistry;
		std::unordered_map<SHEventHandle, SHEventDataPtr> dataEventMap;

		SHEventHandle handleCounter;

		/****************************************************************************
		 * \param   ListenerConstPtr - Const pointer to listener that sent event.
		 * \param   EventType - Event data

		 * \brief		Broadcast event to all receivers that are subscribed to this
		 *					listener.
		****************************************************************************/
		void Broadcast(SHEvent const&);

		/****************************************************************************
		 * \param   ReceiverPtr - Pointer to receiver
		 * \param   ListenerConstPtr - Const pointer to listener that receiver is
		 *					subscribing to.

		 * \brief   Registers receiver as a subscriber to listener in the registry.
		****************************************************************************/
		void RegisterReceiverToType(SHEventIdentifier, ReceiverPtr);

	};
}

#endif // !SH_EVENTS_MANAGER_H