#pragma once

#include "BsCorePrerequisites.h"
#include "BsGameObject.h"
#include "BsEvent.h"
#include "BsStringID.h"
#include "BsRendererMeshData.h"

namespace BansheeEngine
{
	/**
	 * Available parameter block semantics that allow the renderer to identify
	 * the use of a GPU program parameter block specified in a shader.
	 */
	static StringID RBS_Static = "Static";
	static StringID RBS_PerCamera = "PerCamera";
	static StringID RBS_PerFrame = "PerFrame";
	static StringID RBS_PerObject = "PerObject";

	/**
	 * Available parameter semantics that allow the renderer to identify
	 * the use of a GPU parameter specified in a shader.
	 */
	static StringID RPS_WorldViewProjTfrm = "WVP";
	static StringID RPS_ViewProjTfrm = "VP";
	static StringID RPS_ProjTfrm = "P";
	static StringID RPS_ViewTfrm = "V";
	static StringID RPS_WorldTfrm = "W";
	static StringID RPS_InvWorldTfrm = "IW";
	static StringID RPS_WorldNoScaleTfrm = "WNoScale";
	static StringID RPS_InvWorldNoScaleTfrm = "IWNoScale";
	static StringID RPS_WorldDeterminantSign = "WorldDeterminantSign";
	static StringID RPS_Diffuse = "Diffuse";
	static StringID RPS_ViewDir = "ViewDir";

	/**
	 * @brief	Set of options that can be used for controlling the renderer.
	 */	
	struct BS_CORE_EXPORT CoreRendererOptions
	{
		virtual ~CoreRendererOptions() { }
	};

	/**
	 * @brief	Primarily rendering class that allows you to specify how to render objects that exist
	 *			in the scene graph. You need to provide your own implementation of your class.
	 *
	 * @note	Normally you would iterate over all cameras, find visible objects for each camera and render
	 *			those objects in some way.
	 */
	class BS_CORE_EXPORT CoreRenderer
	{
	public:
		CoreRenderer();
		virtual ~CoreRenderer() { }

		/**
		 * @brief	Initializes the renderer. Must be called before using the renderer.
		 *
		 * @note	Internal method.
		 */
		virtual void initialize() { }

		/**
		 * @brief	Cleans up the renderer. Must be called before the renderer is deleted.
		 *
		 * @note	Internal method.
		 */
		virtual void destroy() { }

		/**
		 * @brief	Name of the renderer. Used by materials to find 
		 * 			an appropriate technique for this renderer.
		 */
		virtual const StringID& getName() const = 0;

		/**
		 * @brief	Called in order to render all currently active cameras.
		 */
		virtual void renderAll() = 0;

		/**
		 * @brief	Called whenever a new camera is created.
		 *
		 * @note	Core thread.
		 *			Internal method.
		 */
		virtual void _notifyCameraAdded(const CameraCore* camera) { }

		/**
		 * @brief	Called whenever a camera is destroyed.
		 *
		 * @note	Core thread.
		 *			Internal method.
		 */
		virtual void _notifyCameraRemoved(const CameraCore* camera) { }

		/**
		 * @brief	Creates a new empty renderer mesh data.
		 *
		 * @note	Sim thread.
		 *			Internal method.
		 *			
		 * @see		RendererMeshData
		 */
		virtual RendererMeshDataPtr _createMeshData(UINT32 numVertices, UINT32 numIndices, VertexLayout layout, IndexType indexType = IT_32BIT);

		/**
		 * @brief	Creates a new renderer mesh data using an existing generic mesh data buffer.
		 *
		 * @note	Sim thread.
		 *			Internal method.
		 *			
		 * @see		RendererMeshData
		 */
		virtual RendererMeshDataPtr _createMeshData(const MeshDataPtr& meshData);

		/**
		 * @brief	Registers a new callback that will be executed when the the specify camera is being rendered.
		 *
		 * @param	camera			Camera for which to trigger the callback.
		 * @param	index			Index that determines the order of rendering when there are multiple registered callbacks.
		 *							This must be unique. Lower indices get rendered sooner. Indices below 0 get rendered before the
		 *							main viewport elements, while indices equal or greater to zero after. 
		 * @param	callback		Callback to trigger when the specified camera is being rendered.
		 * @param	isOverlay		If true the render callback guarantees that it will only render overlay data. Overlay data doesn't
		 * 							require a depth buffer, a multisampled render target and is usually cheaper to render (although
		 * 							this depends on the exact renderer). 
		 * 							
		 *							Overlay callbacks are always rendered after all other callbacks, even if their index is negative.
		 *
		 * @note	Core thread.
		 *			Internal method.
		 */
		void _registerRenderCallback(const CameraCore* camera, INT32 index, const std::function<void()>& callback, bool isOverlay = false);

		/**
		 * @brief	Removes a previously registered callback registered with "_registerRenderCallback".
		 */
		void _unregisterRenderCallback(const CameraCore* camera, INT32 index);

		/**
		 * @brief	Sets options used for controlling the rendering.
		 */
		virtual void setOptions(const SPtr<CoreRendererOptions>& options) { }

		/**
		 * @brief	Returns current set of options used for controlling the rendering.
		 */
		virtual SPtr<CoreRendererOptions> getOptions() const { return SPtr<CoreRendererOptions>(); }

	protected:
		/**
		 * @brief	Contains information about a render callback.
		 */
		struct RenderCallbackData
		{
			bool overlay;
			std::function<void()> callback;
		};

		UnorderedMap<const CameraCore*, Map<INT32, RenderCallbackData>> mRenderCallbacks;
	};
}