//********************************** Banshee Engine (www.banshee3d.com) **************************************************//
//**************** Copyright (c) 2016 Marko Pintera (marko.pintera@gmail.com). All rights reserved. **********************//
#pragma once

#include "BsD3D11Prerequisites.h"
#include "RenderAPI/BsVertexDeclaration.h"

namespace bs { namespace ct
{
	/** @addtogroup D3D11
	 *  @{
	 */

	/**	Handles creation and caching of DirectX 11 input layout objects. */
	class D3D11InputLayoutManager
	{
	public:
		/**	Key uniquely identifying vertex declaration and vertex shader combination. */
		struct VertexDeclarationKey
		{
			UINT64 vertxDeclId;
			UINT32 vertexProgramId;
		};

		/**	Creates a hash from vertex declaration key. */
		class HashFunc 
		{
		public:
			::std::size_t operator()(const VertexDeclarationKey &key) const;
		};

		/**	Compares two vertex declaration keys. */
		class EqualFunc
		{
		public:
			bool operator()(const VertexDeclarationKey &a, const VertexDeclarationKey &b) const;
		};

		/**	Contains data about a single instance of DX11 input layout object. */
		struct InputLayoutEntry
		{
			InputLayoutEntry() {}

			ID3D11InputLayout* inputLayout;
			UINT32 lastUsedIdx;
		};

	public:
		D3D11InputLayoutManager();
		~D3D11InputLayoutManager();

		/**
		 * Finds an existing or creates a new D3D11 input layout. Input layout maps a vertex declaration
		 * from a vertex buffer to vertex program input declaration
		 *
		 * @param[in]	vertexShaderDecl	Vertex declaration describing vertex program input parameters.
		 * @param[in]	vertexBufferDecl	Vertex declaration describing structure of a vertex buffer to be bound as input
		 *									to the GPU program.
		 * @param[in]	vertexProgram		Instance of the vertex program we are creating input layout for.
		 *
		 * @note	Error will be thrown if the vertex buffer doesn't provide all the necessary data that the shader expects.
		 */
		ID3D11InputLayout* retrieveInputLayout(const SPtr<VertexDeclaration>& vertexShaderDecl,
			const SPtr<VertexDeclaration>& vertexBufferDecl, D3D11GpuProgram& vertexProgram);

	private:
		/**	Creates a new input layout using the specified parameters and stores it in the input layout map. */
		void addNewInputLayout(const SPtr<VertexDeclaration>& vertexShaderDecl, const SPtr<VertexDeclaration>& vertexBufferDecl,
			D3D11GpuProgram& vertexProgram);

		/**	Destroys least used input layout. */
		void removeLeastUsed();

	private:
		static const int DECLARATION_BUFFER_SIZE = 1024;
		static const int NUM_ELEMENTS_TO_PRUNE = 64;

		UnorderedMap<VertexDeclarationKey, InputLayoutEntry*, HashFunc, EqualFunc> mInputLayoutMap;

		bool mWarningShown;
		UINT32 mLastUsedCounter;
	};

	/** @} */
}}