BansheeEngine/BansheeCore/Include/BsSamplerState.h

#pragma once

#include "BsCorePrerequisites.h"
#include "BsColor.h"
#include "BsIReflectable.h"
#include "BsCoreObject.h"

namespace BansheeEngine 
{
	/** @addtogroup RenderAPI
	 *  @{
	 */

	/**
	 * Structure used for initializing a SamplerState.
	 *
	 * @see		SamplerState
	 */
	struct BS_CORE_EXPORT SAMPLER_STATE_DESC
	{
		SAMPLER_STATE_DESC()
			: minFilter(FO_LINEAR), magFilter(FO_LINEAR), mipFilter(FO_POINT), 
			maxAniso(0), mipmapBias(0), comparisonFunc(CMPF_ALWAYS_FAIL), mipMin(-FLT_MAX), 
			mipMax(FLT_MAX), borderColor(Color::White)
		{ }

		bool operator==(const SAMPLER_STATE_DESC& rhs) const;

		UVWAddressingMode addressMode;
		FilterOptions minFilter;
		FilterOptions magFilter;
		FilterOptions mipFilter;
		UINT32 maxAniso;
		float mipmapBias;
		float mipMin;
		float mipMax;
		Color borderColor;
		CompareFunction comparisonFunc;
	};

	/** Properties of SamplerState. Shared between sim and core thread versions of SamplerState. */
	class BS_CORE_EXPORT SamplerProperties
	{
	public:
		SamplerProperties(const SAMPLER_STATE_DESC& desc);

		/**
		 * Returns texture addressing mode for each possible texture coordinate. Addressing modes determine how are texture
		 * coordinates outside of [0, 1] range handled.
		 */
		const UVWAddressingMode& getTextureAddressingMode() const { return mData.addressMode; }

		/** Gets the filtering used when sampling from a texture. */
        FilterOptions getTextureFiltering(FilterType ftpye) const;

		/**
		 * Gets the anisotropy level. Higher anisotropy means better filtering for textures displayed on an angled slope 
		 * relative to the viewer.
		 */
		unsigned int getTextureAnisotropy() const { return mData.maxAniso; }

		/** Gets a function that compares sampled data with existing sampled data. */
		CompareFunction getComparisonFunction() const { return mData.comparisonFunc; }

		/**
		 * Mipmap bias allows you to adjust the mipmap selection calculation. Negative values  force a larger mipmap to be
		 * used, and positive values smaller. Units are in values of mip levels, so -1 means use a mipmap one level higher 
		 * than default.
		 */
		float getTextureMipmapBias() const { return mData.mipmapBias; }

		/** Returns the minimum mip map level. */
		float getMinimumMip() const { return mData.mipMin; }

		/** Returns the maximum mip map level. */
		float getMaximumMip() const { return mData.mipMax; }

		/**
		 * Gets the border color that will be used when border texture addressing is used and texture address is outside of
		 * the valid range.
		 */
		const Color& getBorderColor() const;

		/**	Returns the hash value generated from the sampler state properties. */
		UINT64 getHash() const { return mHash; }

		/**	Returns the descriptor originally used for creating the sampler state. */
		SAMPLER_STATE_DESC getDesc() const { return mData; }

	protected:
		friend class SamplerState;
		friend class SamplerStateCore;
		friend class SamplerStateRTTI;

		SAMPLER_STATE_DESC mData;
		UINT64 mHash;
	};

	/** @cond INTERNAL */

	/**
	 * Core thread version of SamplerState.
	 *
	 * @note	Core thread.
	 */
	class BS_CORE_EXPORT SamplerStateCore : public CoreObjectCore
	{
	public:
		virtual ~SamplerStateCore();

		/**	Returns information about the sampler state. */
		const SamplerProperties& getProperties() const;

		/**	Returns the default sampler state. */
		static const SPtr<SamplerStateCore>& getDefault();

	protected:
		friend class RenderStateCoreManager;

		SamplerStateCore(const SAMPLER_STATE_DESC& desc);

		/** @copydoc CoreObjectCore::initialize */
		void initialize() override;

		/**	Creates any API-specific state objects. */
		virtual void createInternal() { }

		SamplerProperties mProperties;
	};

	/** @endcond */

	/**
	 * Class representing the state of a texture sampler.
	 *	
	 * @note	
	 * Sampler units are used for retrieving and filtering data from textures set in a GPU program. Sampler states are 
	 * immutable.
	 * @note
	 * Sim thread.
	 */
	class BS_CORE_EXPORT SamplerState : public IReflectable, public CoreObject
    {
    public:
		virtual ~SamplerState();

		/**	Returns information about the sampler state. */
		const SamplerProperties& getProperties() const;

		/**	Retrieves a core implementation of the sampler state usable only from the core thread. */
		SPtr<SamplerStateCore> getCore() const;

		/**	Creates a new sampler state using the provided descriptor structure. */
		static SamplerStatePtr create(const SAMPLER_STATE_DESC& desc);

		/**	Returns the default sampler state. */
		static const SamplerStatePtr& getDefault();

		/**	Generates a hash value from a sampler state descriptor. */
		static UINT64 generateHash(const SAMPLER_STATE_DESC& desc);

	protected:
		SamplerState(const SAMPLER_STATE_DESC& desc);

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

		SamplerProperties mProperties;

		friend class RenderStateManager;

		/************************************************************************/
		/* 								RTTI		                     		*/
		/************************************************************************/

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

	/** @} */
}

/** @cond STDLIB */
/** @addtogroup RenderAPI
 *  @{
 */

/**	Hash value generator for SAMPLER_STATE_DESC. */
template<>
struct std::hash<BansheeEngine::SAMPLER_STATE_DESC>
{
	size_t operator()(const BansheeEngine::SAMPLER_STATE_DESC& value) const
	{
		return (size_t)BansheeEngine::SamplerState::generateHash(value);
	}
};

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