#pragma once

#include "BsGLPrerequisites.h"
#include "BsVertexDeclaration.h"
#include "BsDebug.h"
#include "BsException.h"
#include "BsGpuParamDesc.h"

namespace BansheeEngine
{
	/**
	 * @brief	Holds a GLSL program input attribute used in vertex programs.
	 */
	struct GLSLAttribute
	{
		/**
		 * @brief	Constructs a new attribute from a name and a semantic that represents
		 *			in which way is the attribute used.
		 */
		GLSLAttribute(const String& name, VertexElementSemantic semantic)
		:mName(name), mSemantic(semantic)
		{ }

		/**
		 * @brief	Return true if attribute name matches the specified name
		 *			and returns optional semantic index if it exists. Start of the
		 *			two compared strings must match, and the remaining non-matching
		 *			bit will be assumed to be the semantic index. Returns -1 if no
		 *			match is made.
		 */
		INT32 matchesName(const String& name);

		/**
		 * @brief	Returns the semantic of this attribute.
		 */
		VertexElementSemantic getSemantic() const { return mSemantic; }

	private:
		String mName;
		VertexElementSemantic mSemantic;
	};

	/**
	 * @brief	Helper class that is able to parse a GLSL GPU program and retrieve
	 *			used uniforms and input attributes.
	 */
	class GLSLParamParser
	{
	public:
		/**
		 * @brief	Parses a compiled OpenGL program and outputs a parameter description
		 *			that contains information about used uniforms.
		 *
		 * @param	glProgram		OpenGL handle to the GPU program.
		 * @param	returnParamDesc	Output structure containing the parsed data.
		 */
		void buildUniformDescriptions(GLuint glProgram, GpuParamDesc& returnParamDesc);

		/**
		 * @brief	Parses a compiled OpenGL program and outputs vertex element list that
		 *			describes input attributes to the program. Only valid for vertex programs.
		 *
		 * @param	glProgram	OpenGL handle to the GPU program.
		 */
		List<VertexElement> buildVertexDeclaration(GLuint glProgram);

	private:
		/**
		 * @brief	Populates information for uniform with the specified index into the
		 *			provided structure.
		 *
		 * @param	desc			Output structure containing the parsed data.
		 * @param	paramName		Name of the uniform.
		 * @param	programHandle	Internal OpenGL handle to the GPU program.
		 * @param	uniformIndex	Unique uniform index to retrieve data from. Obtained from OpenGL parsing methods.
		 */
		void determineParamInfo(GpuParamDataDesc& desc, const String& paramName, GLuint programHandle, GLuint uniformIndex);

		/**
		* Attempts to find out a vertex element semantic based on input parameter name.
		* GLSL has no concept of semantics, so we require all shaders to use specific names for attributes
		* so that we know what they are used for.
		*
		* Valid names and semantics:
		*  bs_position - VES_POSITION
		*  bs_normal - VES_NORMAL
		*  bs_tangent - VES_TANGENT
		*  bs_bitangent - VES_BITANGENT
		*  bs_texcoord - VES_TEXCOORD
		*  bs_color - VES_COLOR
		*  bs_blendweights - VES_BLEND_WEIGHTS
		*  bs_blendindices - VES_BLEND_INDICES
		*
		* You may append a number to the end of the name to specify semantic index.
		*
		* @return	True if it succeeds, false if it fails.
		*/
		bool attribNameToElementSemantic(const String& name, VertexElementSemantic& semantic, UINT16& index);

		/**
		 * @brief	Converts an OpenGL type to vertex element type.
		 */
		VertexElementType glTypeToAttributeType(GLenum glType);
	};
}