#pragma once

#include "BsCorePrerequisites.h"
#include "BsResource.h"
#include "BsStringID.h"
#include "BsResourceMetaData.h"

namespace BansheeEngine
{
	/** @addtogroup Material
	 *  @{
	 */

	/**
	 * Describes a single data (int, Vector2, etc.) shader parameter.
	 *
	 * @see	Shader::addParameter().
	 */
	struct SHADER_DATA_PARAM_DESC
	{
		String name;
		String gpuVariableName;
		GpuParamDataType type;
		StringID rendererSemantic;
		UINT32 arraySize;
		UINT32 elementSize;
		UINT32 defaultValueIdx;
	};

	/**
	 * Describes a single object (texture, sampler state, etc.) shader parameter.
	 *
	 * @see	Shader::addParameter().
	 */
	struct SHADER_OBJECT_PARAM_DESC
	{
		String name;
		Vector<String> gpuVariableNames;
		StringID rendererSemantic;
		GpuParamObjectType type;
		UINT32 defaultValueIdx;
	};

	/** Describes a shader parameter block. */
	struct SHADER_PARAM_BLOCK_DESC
	{
		String name;
		bool shared;
		StringID rendererSemantic;
		GpuParamBlockUsage usage;
	};

	/** @} */

	/** @addtogroup Implementation
	 *  @{
	 */

	/** Structure used for initializing a shader. */
	template<bool Core>
	struct BS_CORE_EXPORT TSHADER_DESC
	{
		template<bool Core> struct TTextureType {};
		template<> struct TTextureType < false > { typedef HTexture Type; };
		template<> struct TTextureType < true > { typedef SPtr<TextureCore> Type; };

		template<bool Core> struct TSamplerStateType {};
		template<> struct TSamplerStateType < false > { typedef SamplerStatePtr Type; };
		template<> struct TSamplerStateType < true > { typedef SPtr<SamplerStateCore> Type; };

		typedef typename TTextureType<Core>::Type TextureType;
		typedef typename TSamplerStateType<Core>::Type SamplerStateType;

		TSHADER_DESC();

		/**
		 * Registers a new data (int, Vector2, etc.) parameter you that you may then use via Material by providing the 
		 * parameter name. All parameters internally map to variables defined in GPU programs.
		 *
		 * @param[in]	name		   		The name of the parameter. Name must be unique between all data and object parameters.
		 * @param[in]	gpuVariableName		Name of the GPU variable in the GpuProgram that the parameter corresponds with.
		 * @param[in]	type		   		The type of the parameter, must be the same as the type in GpuProgram.
		 * @param[in]	rendererSemantic	(optional) Semantic that allows you to specify the use of this parameter in the 
		 *									renderer. The actual value of the semantic depends on the current Renderer and
		 *									its supported list of semantics. Elements with renderer semantics should not be
		 *									updated by the user, and will be updated by the renderer. These semantics will 
		 *									also be used to determine if a shader is compatible with a specific renderer 
		 *									or not. Value of 0 signifies the parameter is not used by the renderer.
		 * @param[in]	arraySize	   		(optional) If the parameter is an array, the number of elements in the array. 
		 *									Size of 1 means its not an array.
		 * @param[in]	elementSize	   		(optional) Size of an individual element in the array, in bytes. You only need 
		 *									to set this if you are setting variable length parameters, like structs.
		 * @param[in]	defaultValue		(optional) Pointer to the buffer containing the default value for this parameter
		 *									(initial value that will be set when a material is initialized with this shader). 
		 *									The provided buffer must be of the correct size (depending on the element type 
		 *									and array size).
		 *
		 * @note	If multiple parameters are given with the same name but different types behavior is undefined.
		 */
		void addParameter(const String& name, const String& gpuVariableName, GpuParamDataType type, StringID rendererSemantic = StringID::NONE,
			UINT32 arraySize = 1, UINT32 elementSize = 0, UINT8* defaultValue = nullptr);

		/**
		 * Registers a new object (texture, sampler state, etc.) parameter you that you may then use via Material by 
		 * providing the parameter name. All parameters internally map to variables defined in GPU programs. Multiple GPU 
		 * variables may be mapped to a single parameter in which case the first variable actually found in the program will
		 * be used while others will be ignored.
		 *
		 * @param[in]	name				The name of the parameter. Name must be unique between all data and object parameters.
		 * @param[in]	gpuVariableName		Name of the GPU variable in the GpuProgram that the parameter corresponds with.
		 * @param[in]	type		   		The type of the parameter, must be the same as the type in GpuProgram.
		 * @param[in]	rendererSemantic	(optional) Semantic that allows you to specify the use of this parameter in the 
		 *									renderer. The actual value of the semantic depends on the current Renderer and 
		 *									its supported list of semantics. Elements with renderer semantics should not be 
		 *									updated by the user, and will be updated by the renderer. These semantics will 
		 *									also be used to determine if a shader is compatible with a specific renderer or 
		 *									not. Value of 0 signifies the parameter is not used by the renderer.
		 *
		 * @note	
		 * If multiple parameters are given with the same name but different types behavior is undefined. You are allowed 
		 * to call this method multiple times in order to map multiple GPU variable names to a single parameter, but the 
		 * default value (if any) will only be recognized on the first call. Mapping multiple GPU variables to a single 
		 * parameter is useful when you are defining a shader that supports techniques across different render systems 
		 * where GPU variable names for the same parameters might differ.
		 */
		void addParameter(const String& name, const String& gpuVariableName, GpuParamObjectType type, StringID rendererSemantic = StringID::NONE);

		/**
		 * @see	SHADER_DESC::addParameter(const String&, const String&, GpuParamObjectType, StringID)
		 *
		 * @note	
		 * Specialized version of addParameter that accepts a default sampler value that will be used for initializing the 
		 * object parameter upon Material creation. Default sampler value is only valid if the object type is one of the 
		 * sampler types.
		 */
		void addParameter(const String& name, const String& gpuVariableName, GpuParamObjectType type, 
			const SamplerStateType& defaultValue, StringID rendererSemantic = StringID::NONE);

		/**
		 * @see	SHADER_DESC::addParameter(const String&, const String&, GpuParamObjectType, StringID)
		 *
		 * @note	
		 * Specialized version of addParameter that accepts a default texture value that will be used for initializing the 
		 * object parameter upon Material creation. Default texture value is only valid if the object type is one of the 
		 * texture types.
		 */
		void addParameter(const String& name, const String& gpuVariableName, GpuParamObjectType type, 
			const TextureType& defaultValue, StringID rendererSemantic = StringID::NONE);

		/**
		 * Changes parameters of a parameter block with the specified name.
		 *
		 * @param[in]	name				Name of the parameter block. This should correspond with the name specified in 
		 *									the GPU program code.
		 * @param[in]	shared				If parameter block is marked as shared it will not be automatically created by 
		 *									the Material. You will need to create it elsewhere and then assign it manually.
		 * @param[in]	usage				Specified how often do we plan on modifying the buffer, which determines how is 
		 *									the buffer internally stored for best performance.
		 * @param[in]	rendererSemantic	(optional) Semantic that allows you to specify the use of this parameter block 
		 *									in the renderer. The actual value of the semantic depends on the current 
		 *									Renderer and its supported list of semantics. Elements with a renderer semantic
		 *									will not have their parameter block automatically created (similar to "shared" 
		 *									argument), but instead a Renderer will create an assign it instead. Be aware 
		 *									that renderers have strict policies on what and how are parameters stored in the 
		 *									buffer and you will need to respect them. If you don't respect them your shader 
		 *									will be deemed incompatible and won't be used. Value of 0 signifies the parameter
		 *									block is not used by the renderer.
		 */
		void setParamBlockAttribs(const String& name, bool shared, GpuParamBlockUsage usage, StringID rendererSemantic = StringID::NONE);

		/**
		 * Sorting type to use when performing sort in the render queue. Default value is sort front to back which causes
		 * least overdraw and is preferable. Transparent objects need to be sorted back to front. You may also specify no 
		 * sorting and the elements will be rendered in the order they were added to the render queue.
		 */
		QueueSortType queueSortType;

		/**
		 * Priority that allows you to control in what order are your shaders rendered. See QueuePriority for a list of 
		 * initial values. Shaders with higher priority will be rendered before shaders with lower priority, and 
		 * additionally render queue will only sort elements within the same priority group.
		 *
		 * @note	
		 * This is useful when you want all your opaque objects to be rendered before you start drawing your transparent 
		 * ones. Or to render your overlays after everything else. Values provided in QueuePriority are just for general 
		 * guidance and feel free to increase them or decrease them for finer tuning. (e.g. QueuePriority::Opaque + 1).
		 */
		INT32 queuePriority;

		/**
		 * Enables or disables separable passes. When separable passes are disabled all shader passes will be executed in a
		 * sequence one after another. If it is disabled the renderer is free to mix and match passes from different 
		 * objects to achieve best performance. (They will still be executed in sequence, but some other object may be 
		 * rendered in-between passes)
		 *
		 * @note	Shaders with transparency generally can't be separable, while opaque can.
		 */
		bool separablePasses;

		/** Flags that let the renderer know how should it interpret the shader. */
		UINT32 flags;

		Map<String, SHADER_DATA_PARAM_DESC> dataParams;
		Map<String, SHADER_OBJECT_PARAM_DESC> textureParams;
		Map<String, SHADER_OBJECT_PARAM_DESC> bufferParams;
		Map<String, SHADER_OBJECT_PARAM_DESC> samplerParams;
		Map<String, SHADER_PARAM_BLOCK_DESC> paramBlocks;

		Vector<UINT8> dataDefaultValues;
		Vector<SamplerStateType> samplerDefaultValues;
		Vector<TextureType> textureDefaultValues;

	private:
		/**
		 * @copydoc	addParameter(const String&, const String&, GpuParamObjectType, StringID)
		 *
		 * @note	Common method shared by different addParameter overloads.
		 */
		void addParameterInternal(const String& name, const String& gpuVariableName, GpuParamObjectType type, StringID rendererSemantic, UINT32 defaultValueIdx);
	};

	/**
	 * Shader represents a collection of techniques. They are used in Materials, which can be considered as instances of a 
	 * Shader. Multiple materials may share the same shader but provide different parameters to it.
	 *
	 * Shader will always choose the first supported technique based on the current render system, render manager and other
	 * properties. So make sure to add most important techniques first so you make sure they are used if they are supported.
	 *
	 * @note	Templated version of Shader used for implementing both sim and core thread variants.
	 */
	template<bool Core>
	class BS_CORE_EXPORT TShader
	{
	public:
		template<bool Core> struct TTechniqueType {};
		template<> struct TTechniqueType < false > { typedef Technique Type; };
		template<> struct TTechniqueType < true > { typedef TechniqueCore Type; };

		typedef typename TTechniqueType<Core>::Type TechniqueType;
		typedef typename TSHADER_DESC<Core>::TextureType TextureType;
		typedef typename TSHADER_DESC<Core>::SamplerStateType SamplerStateType;

		TShader() { }
		TShader(const String& name, const TSHADER_DESC<Core>& desc, const Vector<SPtr<TechniqueType>>& techniques, UINT32 id);
		virtual ~TShader();
	
		/** Returns the total number of techniques in this shader. */
		UINT32 getNumTechniques() const { return (UINT32)mTechniques.size(); }

		/**
		 * Gets the best supported technique based on current render and other systems. Returns null if not a single 
		 * technique is supported.
		 */
		SPtr<TechniqueType> getBestTechnique() const;

		/**
		 * Returns currently active queue sort type.
		 *
		 * @see		SHADER_DESC::queueSortType
		 */
		QueueSortType getQueueSortType() const { return mDesc.queueSortType; }

		/**
		 * Returns currently active queue priority.
		 *
		 * @see		SHADER_DESC::queuePriority
		 */
		INT32 getQueuePriority() const { return mDesc.queuePriority; }

		/**
		 * Returns if separable passes are allowed.
		 *
		 * @see		SHADER_DESC::separablePasses
		 */
		bool getAllowSeparablePasses() const { return mDesc.separablePasses; }

		/**
		 * Returns flags that control how the renderer interprets the shader. Actual interpretation of the flags depends on 
		 * the active renderer.
		 */
		UINT32 getFlags() const { return mDesc.flags; }

		/** Returns type of the parameter with the specified name. Throws exception if the parameter doesn't exist. */
		GpuParamType getParamType(const String& name) const;

		/**
		 * Returns description for a data parameter with the specified name. Throws exception if the parameter doesn't exist.
		 */
		const SHADER_DATA_PARAM_DESC& getDataParamDesc(const String& name) const;

		/**
		 * Returns description for a texture parameter with the specified name. Throws exception if the parameter doesn't 
		 * exist.
		 */
		const SHADER_OBJECT_PARAM_DESC& getTextureParamDesc(const String& name) const;

		/**
		 * Returns description for a sampler parameter with the specified name. Throws exception if the parameter doesn't 
		 * exist.
		 */
		const SHADER_OBJECT_PARAM_DESC& getSamplerParamDesc(const String& name) const;

		/**
		 * Returns description for a buffer parameter with the specified name. Throws exception if the parameter doesn't 
		 * exist.
		 */
		const SHADER_OBJECT_PARAM_DESC& getBufferParamDesc(const String& name) const;

		/** Checks if the parameter with the specified name exists, and is a data parameter. */
		bool hasDataParam(const String& name) const;

		/**	Checks if the parameter with the specified name exists, and is a texture parameter. */
		bool hasTextureParam(const String& name) const;

		/** Checks if the parameter with the specified name exists, and is a sampler parameter. */
		bool hasSamplerParam(const String& name) const;

		/** Checks if the parameter with the specified name exists, and is a buffer parameter. */
		bool hasBufferParam(const String& name) const;

		/**	Returns a map of all data parameters in the shader. */
		const Map<String, SHADER_DATA_PARAM_DESC>& getDataParams() const { return mDesc.dataParams; }

		/**	Returns a map of all texture parameters in the shader. */
		const Map<String, SHADER_OBJECT_PARAM_DESC>& getTextureParams() const { return mDesc.textureParams; }

		/**	Returns a map of all buffer parameters in the shader. */
		const Map<String, SHADER_OBJECT_PARAM_DESC>& getBufferParams() const { return mDesc.bufferParams; }

		/** Returns a map of all sampler parameters in the shader. */
		const Map<String, SHADER_OBJECT_PARAM_DESC>& getSamplerParams() const { return mDesc.samplerParams; }

		/** Returns a map of all parameter blocks. */
		const Map<String, SHADER_PARAM_BLOCK_DESC>& getParamBlocks() const { return mDesc.paramBlocks; }

		/**
		 * Returns a default texture for a parameter that has the specified default value index (retrieved from the 
		 * parameters descriptor).
		 */
		TextureType getDefaultTexture(UINT32 index) const;

		/**
		 * Returns a default sampler state for a parameter that has the specified default value index (retrieved from the 
		 * parameters descriptor).
		 */
		SamplerStateType getDefaultSampler(UINT32 index) const;

		/**
		 * Returns a pointer to the internal buffer containing the default value for a data parameter that has the
		 * specified default value index (retrieved from the parameters descriptor).
		 */
		UINT8* getDefaultValue(UINT32 index) const;

		/** Returns the unique shader ID. */
		UINT32 getId() const { return mId; }

	protected:
		String mName;
		TSHADER_DESC<Core> mDesc;
		Vector<SPtr<TechniqueType>> mTechniques;
		UINT32 mId;
	};

	/** @} */

	/** @addtogroup Material
	 *  @{
	 */

	/** @cond INTERNAL */

	typedef TSHADER_DESC<true> SHADER_DESC_CORE;
	
	/** @copydoc ShaderBase */
	class BS_CORE_EXPORT ShaderCore : public CoreObjectCore, public TShader<true>
	{
	public:
		/** @copydoc Shader::create */
		static SPtr<ShaderCore> create(const String& name, const SHADER_DESC_CORE& desc, const Vector<SPtr<TechniqueCore>>& techniques);

	protected:
		friend class Shader;

		ShaderCore(const String& name, const SHADER_DESC_CORE& desc, const Vector<SPtr<TechniqueCore>>& techniques, UINT32 id);

		static std::atomic<UINT32> mNextShaderId;
	};

	/** @endcond */

	typedef TSHADER_DESC<false> SHADER_DESC;

	/** @copydoc ShaderBase */
	class BS_CORE_EXPORT Shader : public Resource, public TShader<false>
	{
	public:
		/** Retrieves an implementation of a shader usable only from the core thread. */
		SPtr<ShaderCore> getCore() const;

		/**
		 * Sets a list include file paths that are referenced by this shader.
		 *
		 * @note	
		 * This is not used directly by the shader as includes are expected to be processed during GPU program and state 
		 * creation, but it may be referenced by higher layers for various purposes.
		 */
		void setIncludeFiles(const Vector<String>& includes);

		/**	Checks is the provided object type a sampler. */
		static bool isSampler(GpuParamObjectType type);

		/**	Checks is the provided object type a texture. */
		static bool isTexture(GpuParamObjectType type);

		/** Checks is the provided object type a buffer. */
		static bool isBuffer(GpuParamObjectType type);

		/**
		 * Returns the size in bytes for a specific data type.
		 *
		 * @note	Returns 0 for variable size types like structures.
		 */
		static UINT32 getDataParamSize(GpuParamDataType type);

		/**	Creates a new shader resource using the provided descriptor and techniques. */
		static HShader create(const String& name, const SHADER_DESC& desc, const Vector<SPtr<Technique>>& techniques);

		/**	Returns a shader object but doesn't initialize it. */
		static ShaderPtr createEmpty();

		/** @cond INTERNAL */

		/**
		 * Creates a new shader object using the provided descriptor and techniques.
		 *
		 * @note	Internal method.
		 */
		static ShaderPtr _createPtr(const String& name, const SHADER_DESC& desc, const Vector<SPtr<Technique>>& techniques);

		/** @endcond */

	private:
		Shader(const String& name, const SHADER_DESC& desc, const Vector<SPtr<Technique>>& techniques, UINT32 id);

		/** @copydoc CoreObject::getCoreDependencies */
		void getCoreDependencies(Vector<CoreObject*>& dependencies) override;

		/** @copydoc CoreObject::createCore */
		SPtr<CoreObjectCore> createCore() const override;

		/** Converts a sim thread version of the shader descriptor to a core thread version. */
		SHADER_DESC_CORE convertDesc(const SHADER_DESC& desc) const;

	private:
		/************************************************************************/
		/* 								RTTI		                     		*/
		/************************************************************************/
		Shader() { }

	public:
		friend class ShaderRTTI;
		static RTTITypeBase* getRTTIStatic();
		virtual RTTITypeBase* getRTTI() const override;
	};

	/** @cond INTERNAL */

	/** Shader specific resource meta-data containing information about referenced include files. */
	class BS_CORE_EXPORT ShaderMetaData : public ResourceMetaData
	{
	public:
		Vector<String> includes;

		/************************************************************************/
		/* 								SERIALIZATION                      		*/
		/************************************************************************/
	public:
		friend class ShaderMetaDataRTTI;
		static RTTITypeBase* getRTTIStatic();
		virtual RTTITypeBase* getRTTI() const override;
	};

	/** @endcond */
	/** @} */
}