/// @brief Include to use generic textures which can represent any texture target but they don't have target specific built-in caches making accesses slower.
/// @file gli/texture.hpp

#pragma once

#include "image.hpp"
#include "target.hpp"
#include "levels.hpp"
#include <array>

namespace gli
{
	/// Genetic texture class. It can support any target.
	class texture
	{
	public:
		typedef size_t size_type;
		typedef gli::target target_type;
		typedef gli::format format_type;
		typedef gli::swizzles swizzles_type;
		typedef storage_linear storage_type;
		typedef storage_type::data_type data_type;
		typedef storage_type::extent_type extent_type;

		/// Create an empty texture instance
		texture();

		/// Create a texture object and allocate a texture storage for it
		/// @param Target Type/Shape of the texture storage_linear
		/// @param Format Texel format
		/// @param Extent Size of the texture: width, height and depth.
		/// @param Layers Number of one-dimensional or two-dimensional images of identical size and format
		/// @param Faces 6 for cube map textures otherwise 1.
		/// @param Levels Number of images in the texture mipmap chain.
		/// @param Swizzles A mechanism to swizzle the components of a texture before they are applied according to the texture environment.
		texture(
			target_type Target,
			format_type Format,
			extent_type const& Extent,
			size_type Layers,
			size_type Faces,
			size_type Levels,
			swizzles_type const& Swizzles = swizzles_type(SWIZZLE_RED, SWIZZLE_GREEN, SWIZZLE_BLUE, SWIZZLE_ALPHA));

		/// Create a texture object by sharing an existing texture storage_type from another texture instance.
		/// This texture object is effectively a texture view where the layer, the face and the level allows identifying
		/// a specific subset of the texture storage_linear source. 
		/// This texture object is effectively a texture view where the target and format can be reinterpreted
		/// with a different compatible texture target and texture format.
		texture(
			texture const& Texture,
			target_type Target,
			format_type Format,
			size_type BaseLayer, size_type MaxLayer,
			size_type BaseFace, size_type MaxFace,
			size_type BaseLevel, size_type MaxLevel,
			swizzles_type const& Swizzles = swizzles_type(SWIZZLE_RED, SWIZZLE_GREEN, SWIZZLE_BLUE, SWIZZLE_ALPHA));

		/// Create a texture object by sharing an existing texture storage_type from another texture instance.
		/// This texture object is effectively a texture view where the target and format can be reinterpreted
		/// with a different compatible texture target and texture format.
		texture(
			texture const& Texture,
			target_type Target,
			format_type Format,
			swizzles_type const& Swizzles = swizzles_type(SWIZZLE_RED, SWIZZLE_GREEN, SWIZZLE_BLUE, SWIZZLE_ALPHA));

		virtual ~texture(){}

		/// Return whether the texture instance is empty, no storage_type or description have been assigned to the instance.
		bool empty() const;

		/// Return the target of a texture instance.
		target_type target() const{return this->Target;}

		/// Return the texture instance format
		format_type format() const;

		swizzles_type swizzles() const;

		/// Return the base layer of the texture instance, effectively a memory offset in the actual texture storage_type to identify where to start reading the layers. 
		size_type base_layer() const;

		/// Return the max layer of the texture instance, effectively a memory offset to the beginning of the last layer in the actual texture storage_type that the texture instance can access. 
		size_type max_layer() const;

		/// Return max_layer() - base_layer() + 1
		size_type layers() const;

		/// Return the base face of the texture instance, effectively a memory offset in the actual texture storage_type to identify where to start reading the faces. 
		size_type base_face() const;

		/// Return the max face of the texture instance, effectively a memory offset to the beginning of the last face in the actual texture storage_type that the texture instance can access. 
		size_type max_face() const;

		/// Return max_face() - base_face() + 1
		size_type faces() const;

		/// Return the base level of the texture instance, effectively a memory offset in the actual texture storage_type to identify where to start reading the levels. 
		size_type base_level() const;

		/// Return the max level of the texture instance, effectively a memory offset to the beginning of the last level in the actual texture storage_type that the texture instance can access. 
		size_type max_level() const;

		/// Return max_level() - base_level() + 1.
		size_type levels() const;

		/// Return the size of a texture instance: width, height and depth.
		extent_type extent(size_type Level = 0) const;

		/// Return the memory size of a texture instance storage_type in bytes.
		size_type size() const;

		/// Return the number of blocks contained in a texture instance storage_type.
		/// genType size must match the block size conresponding to the texture format.
		template <typename genType>
		size_type size() const;

		/// Return the memory size of a specific level identified by Level.
		size_type size(size_type Level) const;

		/// Return the memory size of a specific level identified by Level.
		/// genType size must match the block size conresponding to the texture format.
		template <typename gen_type>
		size_type size(size_type Level) const;

		/// Return a pointer to the beginning of the texture instance data.
		void* data();

		/// Return a pointer of type genType which size must match the texture format block size
		template <typename gen_type>
		gen_type* data();

		/// Return a pointer to the beginning of the texture instance data.
		void const* data() const;

		/// Return a pointer of type genType which size must match the texture format block size
		template <typename gen_type>
		gen_type const* data() const;

		/// Return a pointer to the beginning of the texture instance data.
		void* data(size_type Layer, size_type Face, size_type Level);

		/// Return a pointer to the beginning of the texture instance data.
		void const* const data(size_type Layer, size_type Face, size_type Level) const;

		/// Return a pointer of type genType which size must match the texture format block size
		template <typename gen_type>
		gen_type* data(size_type Layer, size_type Face, size_type Level);

		/// Return a pointer of type genType which size must match the texture format block size
		template <typename gen_type>
		gen_type const* const data(size_type Layer, size_type Face, size_type Level) const;

		/// Clear the entire texture storage_linear with zeros
		void clear();

		/// Clear the entire texture storage_linear with Texel which type must match the texture storage_linear format block size
		/// If the type of gen_type doesn't match the type of the texture format, no conversion is performed and the data will be reinterpreted as if is was of the texture format. 
		template <typename gen_type>
		void clear(gen_type const& Texel);

		/// Clear a specific image of a texture.
		template <typename gen_type>
		void clear(size_type Layer, size_type Face, size_type Level, gen_type const& BlockData);

		/// Clear a subset of a specific image of a texture.
		template <typename gen_type>
		void clear(size_type Layer, size_type Face, size_type Level, extent_type const& TexelOffset, extent_type const& TexelExtent, gen_type const& BlockData);

		/// Copy a specific image of a texture 
		void copy(
			texture const& TextureSrc,
			size_t LayerSrc, size_t FaceSrc, size_t LevelSrc,
			size_t LayerDst, size_t FaceDst, size_t LevelDst);

		/// Copy a subset of a specific image of a texture 
		void copy(
			texture const& TextureSrc,
			size_t LayerSrc, size_t FaceSrc, size_t LevelSrc, extent_type const& OffsetSrc,
			size_t LayerDst, size_t FaceDst, size_t LevelDst, extent_type const& OffsetDst,
			extent_type const& Extent);

		/// Reorder the component in texture memory.
		template <typename gen_type>
		void swizzle(gli::swizzles const& Swizzles);

		/// Fetch a texel from a texture. The texture format must be uncompressed.
		template <typename gen_type>
		gen_type load(extent_type const & TexelCoord, size_type Layer, size_type Face, size_type Level) const;

		/// Write a texel to a texture. The texture format must be uncompressed.
		template <typename gen_type>
		void store(extent_type const& TexelCoord, size_type Layer, size_type Face, size_type Level, gen_type const& Texel);

	protected:
		std::shared_ptr<storage_type> Storage;
		target_type Target;
		format_type Format;
		size_type BaseLayer;
		size_type MaxLayer;
		size_type BaseFace;
		size_type MaxFace;
		size_type BaseLevel;
		size_type MaxLevel;
		swizzles_type Swizzles;

		// Pre compute at texture instance creation some information for faster access to texels
		struct cache
		{
		public:
			enum ctor
			{
				DEFAULT
			};

			explicit cache(ctor)
			{}

			cache
			(
				storage_type& Storage,
				format_type Format,
				size_type BaseLayer, size_type Layers,
				size_type BaseFace, size_type MaxFace,
				size_type BaseLevel, size_type MaxLevel
			)
				: Faces(MaxFace - BaseFace + 1)
				, Levels(MaxLevel - BaseLevel + 1)
			{
				GLI_ASSERT(static_cast<size_t>(gli::levels(Storage.extent(0))) < this->ImageMemorySize.size());

				this->BaseAddresses.resize(Layers * this->Faces * this->Levels);

				for(size_type Layer = 0; Layer < Layers; ++Layer)
				for(size_type Face = 0; Face < this->Faces; ++Face)
				for(size_type Level = 0; Level < this->Levels; ++Level)
				{
					size_type const Index = index_cache(Layer, Face, Level);
					this->BaseAddresses[Index] = Storage.data() + Storage.base_offset(
						BaseLayer + Layer, BaseFace + Face, BaseLevel + Level);
				}

				for(size_type Level = 0; Level < this->Levels; ++Level)
				{
					extent_type const& SrcExtent = Storage.extent(BaseLevel + Level);
					extent_type const& DstExtent = SrcExtent * block_extent(Format) / Storage.block_extent();

					this->ImageExtent[Level] = glm::max(DstExtent, extent_type(1));
					this->ImageMemorySize[Level] = Storage.level_size(BaseLevel + Level);
				}
				
				this->GlobalMemorySize = Storage.layer_size(BaseFace, MaxFace, BaseLevel, MaxLevel) * Layers;
			}

			// Base addresses of each images of a texture.
			data_type* get_base_address(size_type Layer, size_type Face, size_type Level) const
			{
				return this->BaseAddresses[index_cache(Layer, Face, Level)];
			}

			// In texels
			extent_type get_extent(size_type Level) const
			{
				return this->ImageExtent[Level];
			};

			// In bytes
			size_type get_memory_size(size_type Level) const
			{
				return this->ImageMemorySize[Level];
			};

			// In bytes
			size_type get_memory_size() const
			{
				return this->GlobalMemorySize;
			};

		private:
			size_type index_cache(size_type Layer, size_type Face, size_type Level) const
			{
				return ((Layer * this->Faces) + Face) * this->Levels + Level;
			}

			size_type Faces;
			size_type Levels;
			std::vector<data_type*> BaseAddresses;
			std::array<extent_type, 16> ImageExtent;
			std::array<size_type, 16> ImageMemorySize;
			size_type GlobalMemorySize;
		} Cache;
	};
}//namespace gli

#include "./core/texture.inl"