/** 
 * @file llshadermgr.cpp
 * @brief Shader manager implementation.
 *
 * $LicenseInfo:firstyear=2005&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2010, Linden Research, Inc.
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License only.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 * 
 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 * $/LicenseInfo$
 */

#include "linden_common.h"
#include "llshadermgr.h"
#include "llrender.h"
#include "llfile.h"

#if LL_DARWIN
#include "OpenGL/OpenGL.h"
#endif

// Lots of STL stuff in here, using namespace std to keep things more readable
using std::vector;
using std::pair;
using std::make_pair;
using std::string;

LLShaderMgr * LLShaderMgr::sInstance = NULL;

LLShaderMgr::LLShaderMgr()
{
}


LLShaderMgr::~LLShaderMgr()
{
}

// static
LLShaderMgr * LLShaderMgr::instance()
{
	if(NULL == sInstance)
	{
		LL_ERRS("Shaders") << "LLShaderMgr should already have been instantiated by the application!" << LL_ENDL;
	}

	return sInstance;
}

BOOL LLShaderMgr::attachShaderFeatures(LLGLSLShader * shader)
{
	llassert_always(shader != NULL);
	LLShaderFeatures *features = & shader->mFeatures;

	if (features->attachNothing)
	{
		return TRUE;
	}
	//////////////////////////////////////
	// Attach Vertex Shader Features First
	//////////////////////////////////////
	
	// NOTE order of shader object attaching is VERY IMPORTANT!!!
	if (features->calculatesAtmospherics)
	{
		if (features->hasWaterFog)
		{
			if (!shader->attachVertexObject("windlight/atmosphericsVarsWaterV.glsl"))
			{
				return FALSE;
			}
		}
        else if (!shader->attachVertexObject("windlight/atmosphericsVarsV.glsl"))
		{
			return FALSE;
		}
	}

	if (features->calculatesLighting || features->calculatesAtmospherics)
	{
		if (!shader->attachVertexObject("windlight/atmosphericsHelpersV.glsl"))
		{
			return FALSE;
		}
	}
		
	if (features->calculatesLighting)
	{
		if (features->isSpecular)
		{
            if (!shader->attachVertexObject("lighting/lightFuncSpecularV.glsl"))
			{
				return FALSE;
			}
		
			if (!features->isAlphaLighting)
			{
                if (!shader->attachVertexObject("lighting/sumLightsSpecularV.glsl"))
				{
					return FALSE;
				}
			}
			
            if (!shader->attachVertexObject("lighting/lightSpecularV.glsl"))
			{
				return FALSE;
			}
		}
		else 
		{
            if (!shader->attachVertexObject("lighting/lightFuncV.glsl"))
			{
				return FALSE;
			}
			
			if (!features->isAlphaLighting)
			{
                if (!shader->attachVertexObject("lighting/sumLightsV.glsl"))
				{
					return FALSE;
				}
			}
			
            if (!shader->attachVertexObject("lighting/lightV.glsl"))
			{
				return FALSE;
			}
		}
	}
	
	// NOTE order of shader object attaching is VERY IMPORTANT!!!
	if (features->calculatesAtmospherics)
    {
        if (!shader->attachVertexObject("environment/srgbF.glsl")) // NOTE -- "F" suffix is superfluous here, there is nothing fragment specific in srgbF
        {
            return FALSE;
        }

        if (!shader->attachVertexObject("windlight/atmosphericsFuncs.glsl")) {
            return FALSE;
        }

        if (!shader->attachVertexObject("windlight/atmosphericsV.glsl"))
		{
			return FALSE;
		}
	}

	if (features->hasSkinning)
	{
        if (!shader->attachVertexObject("avatar/avatarSkinV.glsl"))
		{
			return FALSE;
		}
	}

	if (features->hasObjectSkinning)
	{
        shader->mRiggedVariant = shader;
        if (!shader->attachVertexObject("avatar/objectSkinV.glsl"))
		{
			return FALSE;
		}
	}
	
	///////////////////////////////////////
	// Attach Fragment Shader Features Next
	///////////////////////////////////////

// NOTE order of shader object attaching is VERY IMPORTANT!!!
    if (features->hasSrgb || features->hasAtmospherics || features->calculatesAtmospherics)
    {
        if (!shader->attachFragmentObject("environment/srgbF.glsl"))
        {
            return FALSE;
        }
    }

	if(features->calculatesAtmospherics)
	{
		if (features->hasWaterFog)
		{
			if (!shader->attachFragmentObject("windlight/atmosphericsVarsWaterF.glsl"))
			{
				return FALSE;
			}
		}
        else if (!shader->attachFragmentObject("windlight/atmosphericsVarsF.glsl"))
		{
			return FALSE;
		}
	}

    if (features->calculatesLighting || features->calculatesAtmospherics)
	{
        if (!shader->attachFragmentObject("windlight/atmosphericsHelpersF.glsl"))
		{
			return FALSE;
		}
	}

    // we want this BEFORE shadows and AO because those facilities use pos/norm access
    if (features->isDeferred || features->hasReflectionProbes)
	{
        if (!shader->attachFragmentObject("deferred/deferredUtil.glsl"))
		{
			return FALSE;
		}
	}

	if (features->hasScreenSpaceReflections)
	{
        if (!shader->attachFragmentObject("deferred/screenSpaceReflUtil.glsl"))
        {
            return FALSE;
        }
	}

    if (features->hasShadows)
	{
        if (!shader->attachFragmentObject("deferred/shadowUtil.glsl"))
		{
			return FALSE;
		}
	}

    if (features->hasReflectionProbes)
    {
        if (!shader->attachFragmentObject("deferred/reflectionProbeF.glsl"))
        {
            return FALSE;
        }
    }

    if (features->hasAmbientOcclusion)
	{
        if (!shader->attachFragmentObject("deferred/aoUtil.glsl"))
		{
			return FALSE;
		}
	}

    if (features->hasIndirect)
	{
        if (!shader->attachFragmentObject("deferred/indirect.glsl"))
		{
			return FALSE;
		}
	}

	if (features->hasGamma)
	{
        if (!shader->attachFragmentObject("windlight/gammaF.glsl"))
		{
			return FALSE;
		}
	}

    if (features->encodesNormal)
	{
        if (!shader->attachFragmentObject("environment/encodeNormF.glsl"))
		{
			return FALSE;
		}
	}

	if (features->hasAtmospherics)
    {
        if (!shader->attachFragmentObject("windlight/atmosphericsFuncs.glsl")) {
            return FALSE;
        }

        if (!shader->attachFragmentObject("windlight/atmosphericsF.glsl"))
		{
			return FALSE;
		}
	}
	
	if (features->hasTransport)
	{
        if (!shader->attachFragmentObject("windlight/transportF.glsl"))
		{
			return FALSE;
		}

		// Test hasFullbright and hasShiny and attach fullbright and 
		// fullbright shiny atmos transport if we split them out.
	}

	// NOTE order of shader object attaching is VERY IMPORTANT!!!
	if (features->hasWaterFog)
	{
        if (!shader->attachFragmentObject("environment/waterFogF.glsl"))
		{
			return FALSE;
		}
	}
	
	if (features->hasLighting)
	{
		if (features->hasWaterFog)
		{
			if (features->disableTextureIndex)
			{
				if (features->hasAlphaMask)
				{
                    if (!shader->attachFragmentObject("lighting/lightWaterAlphaMaskNonIndexedF.glsl"))
					{
						return FALSE;
					}
				}
				else
				{
                    if (!shader->attachFragmentObject("lighting/lightWaterNonIndexedF.glsl"))
					{
						return FALSE;
					}
				}
			}
			else 
			{
				if (features->hasAlphaMask)
				{
                    if (!shader->attachFragmentObject("lighting/lightWaterAlphaMaskF.glsl"))
					{
						return FALSE;
					}
				}
				else
				{
                    if (!shader->attachFragmentObject("lighting/lightWaterF.glsl"))
					{
						return FALSE;
					}
				}
				shader->mFeatures.mIndexedTextureChannels = llmax(LLGLSLShader::sIndexedTextureChannels-1, 1);
			}
		}
		
		else
		{
			if (features->disableTextureIndex)
			{
				if (features->hasAlphaMask)
				{
                    if (!shader->attachFragmentObject("lighting/lightAlphaMaskNonIndexedF.glsl"))
					{
						return FALSE;
					}
				}
				else
				{
                    if (!shader->attachFragmentObject("lighting/lightNonIndexedF.glsl"))
					{
						return FALSE;
					}
				}
			}
			else 
			{
				if (features->hasAlphaMask)
				{
                    if (!shader->attachFragmentObject("lighting/lightAlphaMaskF.glsl"))
					{
						return FALSE;
					}
				}
				else
				{
                    if (!shader->attachFragmentObject("lighting/lightF.glsl"))
					{
						return FALSE;
					}
				}
				shader->mFeatures.mIndexedTextureChannels = llmax(LLGLSLShader::sIndexedTextureChannels-1, 1);
			}
		}
	}
	
	// NOTE order of shader object attaching is VERY IMPORTANT!!!
	else if (features->isFullbright)
	{
	
		if (features->isShiny && features->hasWaterFog)
		{
			if (features->disableTextureIndex)
			{
                if (!shader->attachFragmentObject("lighting/lightFullbrightShinyWaterNonIndexedF.glsl"))
				{
					return FALSE;
				}
			}
			else 
			{
                if (!shader->attachFragmentObject("lighting/lightFullbrightShinyWaterF.glsl"))
				{
					return FALSE;
				}
				shader->mFeatures.mIndexedTextureChannels = llmax(LLGLSLShader::sIndexedTextureChannels-1, 1);
			}
		}
		else if (features->hasWaterFog)
		{
			if (features->disableTextureIndex)
			{
				if (features->hasAlphaMask)
				{
                    if (!shader->attachFragmentObject("lighting/lightFullbrightWaterNonIndexedAlphaMaskF.glsl"))
					{
						return FALSE;
					}
				}
                else if (!shader->attachFragmentObject("lighting/lightFullbrightWaterNonIndexedF.glsl"))
				{
					return FALSE;
				}
			}
			else 
			{
				if (features->hasAlphaMask)
				{
                    if (!shader->attachFragmentObject("lighting/lightFullbrightWaterAlphaMaskF.glsl"))
					{
						return FALSE;
					}
				}
                else if (!shader->attachFragmentObject("lighting/lightFullbrightWaterF.glsl"))
				{
					return FALSE;
				}
				shader->mFeatures.mIndexedTextureChannels = llmax(LLGLSLShader::sIndexedTextureChannels-1, 1);
			}
		}
		
		else if (features->isShiny)
		{
			if (features->disableTextureIndex)
			{
                if (!shader->attachFragmentObject("lighting/lightFullbrightShinyNonIndexedF.glsl"))
				{
					return FALSE;
				}
			}
			else 
			{
                if (!shader->attachFragmentObject("lighting/lightFullbrightShinyF.glsl"))
				{
					return FALSE;
				}
				shader->mFeatures.mIndexedTextureChannels = llmax(LLGLSLShader::sIndexedTextureChannels-1, 1);
			}
		}
		
		else
		{
			if (features->disableTextureIndex)
			{

				if (features->hasAlphaMask)
				{
                    if (!shader->attachFragmentObject("lighting/lightFullbrightNonIndexedAlphaMaskF.glsl"))
					{
						return FALSE;
					}
				}
				else
				{
                    if (!shader->attachFragmentObject("lighting/lightFullbrightNonIndexedF.glsl"))
					{
						return FALSE;
					}
				}
			}
			else 
			{
				if (features->hasAlphaMask)
				{
                    if (!shader->attachFragmentObject("lighting/lightFullbrightAlphaMaskF.glsl"))
					{
						return FALSE;
					}
				}
				else
				{
                    if (!shader->attachFragmentObject("lighting/lightFullbrightF.glsl"))
					{
						return FALSE;
					}
				}
				shader->mFeatures.mIndexedTextureChannels = llmax(LLGLSLShader::sIndexedTextureChannels-1, 1);
			}
		}
	}

	// NOTE order of shader object attaching is VERY IMPORTANT!!!
	else if (features->isShiny)
	{
	
		if (features->hasWaterFog)
		{
			if (features->disableTextureIndex)
			{
                if (!shader->attachFragmentObject("lighting/lightShinyWaterNonIndexedF.glsl"))
				{
					return FALSE;
				}
			}
			else 
			{
                if (!shader->attachFragmentObject("lighting/lightShinyWaterF.glsl"))
				{
					return FALSE;
				}
				shader->mFeatures.mIndexedTextureChannels = llmax(LLGLSLShader::sIndexedTextureChannels-1, 1);
			}
		}
		
		else 
		{
			if (features->disableTextureIndex)
			{
                if (!shader->attachFragmentObject("lighting/lightShinyNonIndexedF.glsl"))
				{
					return FALSE;
				}
			}
			else 
			{
                if (!shader->attachFragmentObject("lighting/lightShinyF.glsl"))
				{
					return FALSE;
				}
				shader->mFeatures.mIndexedTextureChannels = llmax(LLGLSLShader::sIndexedTextureChannels-1, 1);
			}
		}
	}

	if (features->mIndexedTextureChannels <= 1)
	{
		if (!shader->attachVertexObject("objects/nonindexedTextureV.glsl"))
		{
			return FALSE;
		}
	}
	else
	{
        if (!shader->attachVertexObject("objects/indexedTextureV.glsl"))
		{
			return FALSE;
		}
	}

	return TRUE;
}

//============================================================================
// Load Shader

static std::string get_shader_log(GLuint ret)
{
	std::string res;
	
	//get log length 
	GLint length;
    glGetShaderiv(ret, GL_INFO_LOG_LENGTH, &length);
	if (length > 0)
	{
		//the log could be any size, so allocate appropriately
		GLchar* log = new GLchar[length];
        glGetShaderInfoLog(ret, length, &length, log);
		res = std::string((char *)log);
		delete[] log;
	}
	return res;
}

static std::string get_program_log(GLuint ret)
{
    LL_PROFILE_ZONE_SCOPED_CATEGORY_SHADER;
    std::string res;

    //get log length 
    GLint length;
    glGetProgramiv(ret, GL_INFO_LOG_LENGTH, &length);
    if (length > 0)
    {
        //the log could be any size, so allocate appropriately
        GLchar* log = new GLchar[length];
        glGetProgramInfoLog(ret, length, &length, log);
        res = std::string((char*)log);
        delete[] log;
    }
    return res;
}

// get the info log for the given object, be it a shader or program object
// NOTE: ret MUST be a shader OR a program object
static std::string get_object_log(GLuint ret)
{
    if (glIsProgram(ret))
    {
        return get_program_log(ret);
    }
    else
    {
        llassert(glIsShader(ret));
        return get_shader_log(ret);
    }
}

//dump shader source for debugging
void LLShaderMgr::dumpShaderSource(U32 shader_code_count, GLchar** shader_code_text)
{
	char num_str[16]; // U32 = max 10 digits

	LL_SHADER_LOADING_WARNS() << "\n";

	for (U32 i = 0; i < shader_code_count; i++)
	{
		snprintf(num_str, sizeof(num_str), "%4d: ", i+1);
		std::string line_number(num_str);
		LL_CONT << line_number << shader_code_text[i];
	}
    LL_CONT << LL_ENDL;
}

void LLShaderMgr::dumpObjectLog(GLuint ret, BOOL warns, const std::string& filename)
{
    std::string log;
    log = get_object_log(ret);
    std::string fname = filename;
    if (filename.empty())
    {
        fname = "unknown shader file";
    }

	if (log.length() > 0)
	{
        LL_SHADER_LOADING_WARNS() << "Shader loading from " << fname << LL_ENDL;
        LL_SHADER_LOADING_WARNS() << "\n" << log << LL_ENDL;
	}
 }

GLuint LLShaderMgr::loadShaderFile(const std::string& filename, S32 & shader_level, GLenum type, std::unordered_map<std::string, std::string>* defines, S32 texture_index_channels)
{

// endsure work-around for missing GLSL funcs gets propogated to feature shader files (e.g. srgbF.glsl)
#if LL_DARWIN
    if (defines)
    {
        (*defines)["OLD_SELECT"] = "1";
    }
#endif

	GLenum error = GL_NO_ERROR;

	error = glGetError();
	if (error != GL_NO_ERROR)
	{
		LL_SHADER_LOADING_WARNS() << "GL ERROR entering loadShaderFile(): " << error << " for file: " << filename << LL_ENDL;
	}
	
	if (filename.empty()) 
	{
		return 0;
	}


	//read in from file
	LLFILE* file = NULL;

	S32 try_gpu_class = shader_level;
	S32 gpu_class;

    std::string open_file_name;
	//find the most relevant file
	for (gpu_class = try_gpu_class; gpu_class > 0; gpu_class--)
	{	//search from the current gpu class down to class 1 to find the most relevant shader
		std::stringstream fname;
		fname << getShaderDirPrefix();
		fname << gpu_class << "/" << filename;
		
        open_file_name = fname.str();

        /*
        Would be awesome, if we didn't have shaders that re-use files
        with different environments to say, add skinning, etc
        can't depend on cached version to have evaluate ifdefs identically...
        if we can define a deterministic hash for the shader based on
        all the inputs, maybe we can save some time here.
        if (mShaderObjects.count(filename) > 0)
        {
            return mShaderObjects[filename];
        }

        */

 		LL_DEBUGS("ShaderLoading") << "Looking in " << open_file_name << LL_ENDL;
		file = LLFile::fopen(open_file_name, "r");		/* Flawfinder: ignore */
		if (file)
		{
			LL_DEBUGS("ShaderLoading") << "Loading file: " << open_file_name << " (Want class " << gpu_class << ")" << LL_ENDL;            
			break; // done
		}
	}
	
	if (file == NULL)
	{
		LL_WARNS("ShaderLoading") << "GLSL Shader file not found: " << open_file_name << LL_ENDL;
		return 0;
	}

	//we can't have any lines longer than 1024 characters 
	//or any shaders longer than 4096 lines... deal - DaveP
    GLchar buff[1024];
    GLchar *extra_code_text[1024];
    GLchar *shader_code_text[4096 + LL_ARRAY_SIZE(extra_code_text)] = { NULL };
    GLuint extra_code_count = 0, shader_code_count = 0;
    BOOST_STATIC_ASSERT(LL_ARRAY_SIZE(extra_code_text) < LL_ARRAY_SIZE(shader_code_text));
    
    
	S32 major_version = gGLManager.mGLSLVersionMajor;
	S32 minor_version = gGLManager.mGLSLVersionMinor;
	
	if (major_version == 1 && minor_version < 30)
	{
		if (minor_version < 10)
		{
			//should NEVER get here -- if major version is 1 and minor version is less than 10, 
			// viewer should never attempt to use shaders, continuing will result in undefined behavior
			LL_ERRS() << "Unsupported GLSL Version." << LL_ENDL;
		}

		if (minor_version <= 19)
		{
			shader_code_text[shader_code_count++] = strdup("#version 110\n");
			extra_code_text[extra_code_count++] = strdup("#define ATTRIBUTE attribute\n");
			extra_code_text[extra_code_count++] = strdup("#define VARYING varying\n");
			extra_code_text[extra_code_count++] = strdup("#define VARYING_FLAT varying\n");
		}
		else if (minor_version <= 29)
		{
			//set version to 1.20
			shader_code_text[shader_code_count++] = strdup("#version 120\n");
       		extra_code_text[extra_code_count++] = strdup("#define FXAA_GLSL_120 1\n");
			extra_code_text[extra_code_count++] = strdup("#define FXAA_FAST_PIXEL_OFFSET 0\n");
			extra_code_text[extra_code_count++] = strdup("#define ATTRIBUTE attribute\n");
			extra_code_text[extra_code_count++] = strdup("#define VARYING varying\n");
			extra_code_text[extra_code_count++] = strdup("#define VARYING_FLAT varying\n");
		}
	}
	else
	{  
        if (major_version >= 4)
        {
            //set version to 400 or 420
            if (minor_version >= 20)
            {
                shader_code_text[shader_code_count++] = strdup("#version 420\n");
            }
            else
            {
                shader_code_text[shader_code_count++] = strdup("#version 400\n");
            }
        }
        else if (major_version == 3)
        {
            if (minor_version < 10)
		    {
			    shader_code_text[shader_code_count++] = strdup("#version 300\n");
		    }
		    else if (minor_version <= 19)
		    {
			    shader_code_text[shader_code_count++] = strdup("#version 310\n");
		    }
		    else if (minor_version <= 29)
		    {
			    shader_code_text[shader_code_count++] = strdup("#version 320\n");
		    }
            else
            {
                shader_code_text[shader_code_count++] = strdup("#version 330\n");
            }
        }
		else
		{
			//set version to 1.30
			shader_code_text[shader_code_count++] = strdup("#version 130\n");
			//some implementations of GLSL 1.30 require integer precision be explicitly declared
			extra_code_text[extra_code_count++] = strdup("precision mediump int;\n");
			extra_code_text[extra_code_count++] = strdup("precision highp float;\n");
		}

		extra_code_text[extra_code_count++] = strdup("#define DEFINE_GL_FRAGCOLOR 1\n");
		extra_code_text[extra_code_count++] = strdup("#define FXAA_GLSL_130 1\n");

		extra_code_text[extra_code_count++] = strdup("#define ATTRIBUTE in\n");

		if (type == GL_VERTEX_SHADER)
		{ //"varying" state is "out" in a vertex program, "in" in a fragment program 
			// ("varying" is deprecated after version 1.20)
			extra_code_text[extra_code_count++] = strdup("#define VARYING out\n");
			extra_code_text[extra_code_count++] = strdup("#define VARYING_FLAT flat out\n");
		}
		else
		{
			extra_code_text[extra_code_count++] = strdup("#define VARYING in\n");
			extra_code_text[extra_code_count++] = strdup("#define VARYING_FLAT flat in\n");
		}

		//backwards compatibility with legacy texture lookup syntax
		extra_code_text[extra_code_count++] = strdup("#define texture2D texture\n");
		extra_code_text[extra_code_count++] = strdup("#define textureCube texture\n");
		extra_code_text[extra_code_count++] = strdup("#define texture2DLod textureLod\n");
		extra_code_text[extra_code_count++] = strdup("#define shadow2D(a,b) vec2(texture(a,b))\n");
		
		if (major_version > 1 || minor_version >= 40)
		{ //GLSL 1.40 replaces texture2DRect et al with texture
			extra_code_text[extra_code_count++] = strdup("#define texture2DRect texture\n");
			extra_code_text[extra_code_count++] = strdup("#define shadow2DRect(a,b) vec2(texture(a,b))\n");
		}
	}

    // Use alpha float to store bit flags
    // See: C++: addDeferredAttachment(), shader: frag_data[2]
    extra_code_text[extra_code_count++] = strdup("#define GBUFFER_FLAG_SKIP_ATMOS   0.0 \n"); // atmo kill
    extra_code_text[extra_code_count++] = strdup("#define GBUFFER_FLAG_HAS_ATMOS    0.34\n"); // bit 0
    extra_code_text[extra_code_count++] = strdup("#define GBUFFER_FLAG_HAS_PBR      0.67\n"); // bit 1
    extra_code_text[extra_code_count++] = strdup("#define GET_GBUFFER_FLAG(flag)    (abs(norm.w-flag)< 0.1)\n");

	if (defines)
	{
		for (std::unordered_map<std::string,std::string>::iterator iter = defines->begin(); iter != defines->end(); ++iter)
		{
			std::string define = "#define " + iter->first + " " + iter->second + "\n";
			extra_code_text[extra_code_count++] = (GLchar *) strdup(define.c_str());
		}
	}

	if( gGLManager.mIsAMD )
	{
		extra_code_text[extra_code_count++] = strdup( "#define IS_AMD_CARD 1\n" );
	}
	
	if (texture_index_channels > 0 && type == GL_FRAGMENT_SHADER)
	{
		//use specified number of texture channels for indexed texture rendering

		/* prepend shader code that looks like this:

		uniform sampler2D tex0;
		uniform sampler2D tex1;
		uniform sampler2D tex2;
		.
		.
		.
		uniform sampler2D texN;
		
		VARYING_FLAT ivec4 vary_texture_index;

		vec4 ret = vec4(1,0,1,1);

		vec4 diffuseLookup(vec2 texcoord)
		{
			switch (vary_texture_index.r))
			{
				case 0: ret = texture2D(tex0, texcoord); break;
				case 1: ret = texture2D(tex1, texcoord); break;
				case 2: ret = texture2D(tex2, texcoord); break;
				.
				.
				.
				case N: return texture2D(texN, texcoord); break;
			}

			return ret;
		}
		*/

		extra_code_text[extra_code_count++] = strdup("#define HAS_DIFFUSE_LOOKUP\n");

		//uniform declartion
		for (S32 i = 0; i < texture_index_channels; ++i)
		{
			std::string decl = llformat("uniform sampler2D tex%d;\n", i);
			extra_code_text[extra_code_count++] = strdup(decl.c_str());
		}

		if (texture_index_channels > 1)
		{
			extra_code_text[extra_code_count++] = strdup("VARYING_FLAT int vary_texture_index;\n");
		}

		extra_code_text[extra_code_count++] = strdup("vec4 diffuseLookup(vec2 texcoord)\n");
		extra_code_text[extra_code_count++] = strdup("{\n");
		
		
		if (texture_index_channels == 1)
		{ //don't use flow control, that's silly
			extra_code_text[extra_code_count++] = strdup("return texture2D(tex0, texcoord);\n");
			extra_code_text[extra_code_count++] = strdup("}\n");
		}
		else if (major_version > 1 || minor_version >= 30)
		{  //switches are supported in GLSL 1.30 and later
			if (gGLManager.mIsNVIDIA)
			{ //switches are unreliable on some NVIDIA drivers
				for (U32 i = 0; i < texture_index_channels; ++i)
				{
					std::string if_string = llformat("\t%sif (vary_texture_index == %d) { return texture2D(tex%d, texcoord); }\n", i > 0 ? "else " : "", i, i); 
					extra_code_text[extra_code_count++] = strdup(if_string.c_str());
				}
				extra_code_text[extra_code_count++] = strdup("\treturn vec4(1,0,1,1);\n");
				extra_code_text[extra_code_count++] = strdup("}\n");
			}
			else
			{
				extra_code_text[extra_code_count++] = strdup("\tvec4 ret = vec4(1,0,1,1);\n");
				extra_code_text[extra_code_count++] = strdup("\tswitch (vary_texture_index)\n");
				extra_code_text[extra_code_count++] = strdup("\t{\n");
		
				//switch body
				for (S32 i = 0; i < texture_index_channels; ++i)
				{
					std::string case_str = llformat("\t\tcase %d: return texture2D(tex%d, texcoord);\n", i, i);
					extra_code_text[extra_code_count++] = strdup(case_str.c_str());
				}

				extra_code_text[extra_code_count++] = strdup("\t}\n");
				extra_code_text[extra_code_count++] = strdup("\treturn ret;\n");
				extra_code_text[extra_code_count++] = strdup("}\n");
			}
		}
		else
		{ //should never get here.  Indexed texture rendering requires GLSL 1.30 or later 
			// (for passing integers between vertex and fragment shaders)
			LL_ERRS() << "Indexed texture rendering requires GLSL 1.30 or later." << LL_ENDL;
		}
	}
    
	//copy file into memory
	enum {
		  flag_write_to_out_of_extra_block_area = 0x01
		, flag_extra_block_marker_was_found = 0x02
	};
	
	unsigned char flags = flag_write_to_out_of_extra_block_area;
	
	GLuint out_of_extra_block_counter = 0, start_shader_code = shader_code_count, file_lines_count = 0;
	
	while(NULL != fgets((char *)buff, 1024, file)
		  && shader_code_count < (LL_ARRAY_SIZE(shader_code_text) - LL_ARRAY_SIZE(extra_code_text)))
	{
		file_lines_count++;

		bool extra_block_area_found = NULL != strstr((const char*)buff, "[EXTRA_CODE_HERE]");
		
		if(extra_block_area_found && !(flag_extra_block_marker_was_found & flags))
		{
			if(!(flag_write_to_out_of_extra_block_area & flags))
			{
				//shift
				for(GLuint to = start_shader_code, from = extra_code_count + start_shader_code;
					from < shader_code_count; ++to, ++from)
				{
					shader_code_text[to] = shader_code_text[from];
				}
				
				shader_code_count -= extra_code_count;
			}
		  
			//copy extra code
			for(GLuint n = 0; n < extra_code_count
				&& shader_code_count < (LL_ARRAY_SIZE(shader_code_text) - LL_ARRAY_SIZE(extra_code_text)); ++n)
			{
				shader_code_text[shader_code_count++] = extra_code_text[n];
			}
			
			extra_code_count = 0;
			
			flags &= ~flag_write_to_out_of_extra_block_area;
			flags |= flag_extra_block_marker_was_found;
		}
        else
        {
            shader_code_text[shader_code_count] = (GLchar *)strdup((char *)buff);
		
            if(flag_write_to_out_of_extra_block_area & flags)
            {
                shader_code_text[extra_code_count + start_shader_code + out_of_extra_block_counter]
                    = shader_code_text[shader_code_count];
                out_of_extra_block_counter++;
			
                if(out_of_extra_block_counter == extra_code_count)
                {
                    shader_code_count += extra_code_count;
                    flags &= ~flag_write_to_out_of_extra_block_area;
                }
            }
		
            ++shader_code_count;
		}
	} //while
	
	if(!(flag_extra_block_marker_was_found & flags))
	{
		for(GLuint n = start_shader_code; n < extra_code_count + start_shader_code; ++n)
		{
			shader_code_text[n] = extra_code_text[n - start_shader_code];
		}
		
		if (file_lines_count < extra_code_count)
		{
			shader_code_count += extra_code_count;
		}

		extra_code_count = 0;
	}

	fclose(file);

	//create shader object
    GLuint ret = glCreateShader(type);

	error = glGetError();
	if (error != GL_NO_ERROR)
	{
		LL_WARNS("ShaderLoading") << "GL ERROR in glCreateShader: " << error << " for file: " << open_file_name << LL_ENDL;
	}

	//load source
	glShaderSource(ret, shader_code_count, (const GLchar**) shader_code_text, NULL);

	error = glGetError();
	if (error != GL_NO_ERROR)
	{
		LL_WARNS("ShaderLoading") << "GL ERROR in glShaderSource: " << error << " for file: " << open_file_name << LL_ENDL;
	}

	//compile source
	glCompileShader(ret);

	error = glGetError();
	if (error != GL_NO_ERROR)
	{
		LL_WARNS("ShaderLoading") << "GL ERROR in glCompileShader: " << error << " for file: " << open_file_name << LL_ENDL;
	}

	if (error == GL_NO_ERROR)
	{
		//check for errors
		GLint success = GL_TRUE;
        glGetShaderiv(ret, GL_COMPILE_STATUS, &success);

		error = glGetError();
		if (error != GL_NO_ERROR || success == GL_FALSE)
		{
			//an error occured, print log
			LL_WARNS("ShaderLoading") << "GLSL Compilation Error:" << LL_ENDL;
			dumpObjectLog(ret, TRUE, open_file_name);
			dumpShaderSource(shader_code_count, shader_code_text);
			ret = 0;
		}
	}
	else
	{
		ret = 0;
	}
	stop_glerror();

	//free memory
	for (GLuint i = 0; i < shader_code_count; i++)
	{
		free(shader_code_text[i]);
	}

	//successfully loaded, save results
	if (ret)
	{
		// Add shader file to map
        if (type == GL_VERTEX_SHADER) {
            mVertexShaderObjects[filename] = ret;
        }
        else if (type == GL_FRAGMENT_SHADER) {
            mFragmentShaderObjects[filename] = ret;
        }
		shader_level = try_gpu_class;
	}
	else
	{
		if (shader_level > 1)
		{
			shader_level--;
			return loadShaderFile(filename, shader_level, type, defines, texture_index_channels);
		}
		LL_WARNS("ShaderLoading") << "Failed to load " << filename << LL_ENDL;	
	}
	return ret;
}

BOOL LLShaderMgr::linkProgramObject(GLuint obj, BOOL suppress_errors)
{
	//check for errors
    {
        LL_PROFILE_ZONE_NAMED_CATEGORY_SHADER("glLinkProgram");
        glLinkProgram(obj);
    }

    GLint success = GL_TRUE;

    {
        LL_PROFILE_ZONE_NAMED_CATEGORY_SHADER("glsl check link status");
        glGetProgramiv(obj, GL_LINK_STATUS, &success);
        if (!suppress_errors && success == GL_FALSE)
        {
            //an error occured, print log
            LL_SHADER_LOADING_WARNS() << "GLSL Linker Error:" << LL_ENDL;
            dumpObjectLog(obj, TRUE, "linker");
            return success;
        }
    }

	std::string log = get_program_log(obj);
	LLStringUtil::toLower(log);
	if (log.find("software") != std::string::npos)
	{
		LL_SHADER_LOADING_WARNS() << "GLSL Linker: Running in Software:" << LL_ENDL;
		success = GL_FALSE;
		suppress_errors = FALSE;
	}
	return success;
}

BOOL LLShaderMgr::validateProgramObject(GLuint obj)
{
	//check program validity against current GL
	glValidateProgram(obj);
	GLint success = GL_TRUE;
    glGetProgramiv(obj, GL_LINK_STATUS, &success);
	if (success == GL_FALSE)
	{
		LL_SHADER_LOADING_WARNS() << "GLSL program not valid: " << LL_ENDL;
		dumpObjectLog(obj);
	}
	else
	{
		dumpObjectLog(obj, FALSE);
	}

	return success;
}

//virtual
void LLShaderMgr::initAttribsAndUniforms()
{
	//MUST match order of enum in LLVertexBuffer.h
	mReservedAttribs.push_back("position");
	mReservedAttribs.push_back("normal");
	mReservedAttribs.push_back("texcoord0");
	mReservedAttribs.push_back("texcoord1");
	mReservedAttribs.push_back("texcoord2");
	mReservedAttribs.push_back("texcoord3");
	mReservedAttribs.push_back("diffuse_color");
	mReservedAttribs.push_back("emissive");
	mReservedAttribs.push_back("tangent");
	mReservedAttribs.push_back("weight");
	mReservedAttribs.push_back("weight4");
	mReservedAttribs.push_back("clothing");
	mReservedAttribs.push_back("texture_index");
	
	//matrix state
	mReservedUniforms.push_back("modelview_matrix");
	mReservedUniforms.push_back("projection_matrix");
	mReservedUniforms.push_back("inv_proj");
	mReservedUniforms.push_back("modelview_projection_matrix");
    mReservedUniforms.push_back("inv_modelview");
    mReservedUniforms.push_back("identity_matrix");
	mReservedUniforms.push_back("normal_matrix");
	mReservedUniforms.push_back("texture_matrix0");
	mReservedUniforms.push_back("texture_matrix1");
	mReservedUniforms.push_back("texture_matrix2");
	mReservedUniforms.push_back("texture_matrix3");
	mReservedUniforms.push_back("object_plane_s");
	mReservedUniforms.push_back("object_plane_t");
    mReservedUniforms.push_back("texture_basecolor_matrix"); // GLTF
    mReservedUniforms.push_back("texture_normal_matrix"); // GLTF
    mReservedUniforms.push_back("texture_metallic_roughness_matrix"); // GLTF
    mReservedUniforms.push_back("texture_emissive_matrix"); // GLTF
    llassert(mReservedUniforms.size() == LLShaderMgr::TEXTURE_EMISSIVE_MATRIX+1);

	mReservedUniforms.push_back("viewport");

	mReservedUniforms.push_back("light_position");
	mReservedUniforms.push_back("light_direction");
	mReservedUniforms.push_back("light_attenuation");
    mReservedUniforms.push_back("light_deferred_attenuation");
	mReservedUniforms.push_back("light_diffuse");
	mReservedUniforms.push_back("light_ambient");
	mReservedUniforms.push_back("light_count");
	mReservedUniforms.push_back("light");
	mReservedUniforms.push_back("light_col");
	mReservedUniforms.push_back("far_z");

	llassert(mReservedUniforms.size() == LLShaderMgr::MULTI_LIGHT_FAR_Z+1);

    //NOTE: MUST match order in eGLSLReservedUniforms
	mReservedUniforms.push_back("proj_mat");
	mReservedUniforms.push_back("proj_near");
	mReservedUniforms.push_back("proj_p");
	mReservedUniforms.push_back("proj_n");
	mReservedUniforms.push_back("proj_origin");
	mReservedUniforms.push_back("proj_range");
	mReservedUniforms.push_back("proj_ambiance");
	mReservedUniforms.push_back("proj_shadow_idx");
	mReservedUniforms.push_back("shadow_fade");
	mReservedUniforms.push_back("proj_focus");
	mReservedUniforms.push_back("proj_lod");
	mReservedUniforms.push_back("proj_ambient_lod");

	llassert(mReservedUniforms.size() == LLShaderMgr::PROJECTOR_AMBIENT_LOD+1);

	mReservedUniforms.push_back("color");
    mReservedUniforms.push_back("emissiveColor");
    mReservedUniforms.push_back("metallicFactor");
    mReservedUniforms.push_back("roughnessFactor");

	mReservedUniforms.push_back("diffuseMap");
    mReservedUniforms.push_back("altDiffuseMap");
	mReservedUniforms.push_back("specularMap");
    mReservedUniforms.push_back("emissiveMap");
	mReservedUniforms.push_back("bumpMap");
    mReservedUniforms.push_back("bumpMap2");
	mReservedUniforms.push_back("environmentMap");
    mReservedUniforms.push_back("reflectionProbes");
    mReservedUniforms.push_back("irradianceProbes");
	mReservedUniforms.push_back("cloud_noise_texture");
    mReservedUniforms.push_back("cloud_noise_texture_next");
	mReservedUniforms.push_back("fullbright");
	mReservedUniforms.push_back("lightnorm");
	mReservedUniforms.push_back("sunlight_color");
	mReservedUniforms.push_back("ambient_color");
	mReservedUniforms.push_back("blue_horizon");
    mReservedUniforms.push_back("blue_horizon_linear");
	mReservedUniforms.push_back("blue_density");
    mReservedUniforms.push_back("blue_density_linear");
	mReservedUniforms.push_back("haze_horizon");
	mReservedUniforms.push_back("haze_density");
    mReservedUniforms.push_back("haze_density_linear");
	mReservedUniforms.push_back("cloud_shadow");
	mReservedUniforms.push_back("density_multiplier");
	mReservedUniforms.push_back("distance_multiplier");
	mReservedUniforms.push_back("max_y");
	mReservedUniforms.push_back("glow");
	mReservedUniforms.push_back("cloud_color");
	mReservedUniforms.push_back("cloud_pos_density1");
	mReservedUniforms.push_back("cloud_pos_density2");
	mReservedUniforms.push_back("cloud_scale");
	mReservedUniforms.push_back("gamma");
	mReservedUniforms.push_back("scene_light_strength");

	llassert(mReservedUniforms.size() == LLShaderMgr::SCENE_LIGHT_STRENGTH+1);

	mReservedUniforms.push_back("center");
	mReservedUniforms.push_back("size");
	mReservedUniforms.push_back("falloff");

	mReservedUniforms.push_back("box_center");
	mReservedUniforms.push_back("box_size");


	mReservedUniforms.push_back("minLuminance");
	mReservedUniforms.push_back("maxExtractAlpha");
	mReservedUniforms.push_back("lumWeights");
	mReservedUniforms.push_back("warmthWeights");
	mReservedUniforms.push_back("warmthAmount");
	mReservedUniforms.push_back("glowStrength");
	mReservedUniforms.push_back("glowDelta");

	llassert(mReservedUniforms.size() == LLShaderMgr::GLOW_DELTA+1);


	mReservedUniforms.push_back("minimum_alpha");
	mReservedUniforms.push_back("emissive_brightness");

    // Deferred
	mReservedUniforms.push_back("shadow_matrix");
	mReservedUniforms.push_back("env_mat");
	mReservedUniforms.push_back("shadow_clip");
	mReservedUniforms.push_back("sun_wash");
	mReservedUniforms.push_back("shadow_noise");
	mReservedUniforms.push_back("blur_size");
	mReservedUniforms.push_back("ssao_radius");
	mReservedUniforms.push_back("ssao_max_radius");
	mReservedUniforms.push_back("ssao_factor");
	mReservedUniforms.push_back("ssao_factor_inv");
	mReservedUniforms.push_back("ssao_effect_mat");
	mReservedUniforms.push_back("screen_res");
	mReservedUniforms.push_back("near_clip");
	mReservedUniforms.push_back("shadow_offset");
	mReservedUniforms.push_back("shadow_bias");
	mReservedUniforms.push_back("spot_shadow_bias");
	mReservedUniforms.push_back("spot_shadow_offset");
	mReservedUniforms.push_back("sun_dir");
    mReservedUniforms.push_back("moon_dir");
	mReservedUniforms.push_back("shadow_res");
	mReservedUniforms.push_back("proj_shadow_res");
	mReservedUniforms.push_back("depth_cutoff");
	mReservedUniforms.push_back("norm_cutoff");
	mReservedUniforms.push_back("shadow_target_width");
	
	llassert(mReservedUniforms.size() == LLShaderMgr::DEFERRED_SHADOW_TARGET_WIDTH+1);

	mReservedUniforms.push_back("tc_scale");
	mReservedUniforms.push_back("rcp_screen_res");
	mReservedUniforms.push_back("rcp_frame_opt");
	mReservedUniforms.push_back("rcp_frame_opt2");
	
	mReservedUniforms.push_back("focal_distance");
	mReservedUniforms.push_back("blur_constant");
	mReservedUniforms.push_back("tan_pixel_angle");
	mReservedUniforms.push_back("magnification");
	mReservedUniforms.push_back("max_cof");
	mReservedUniforms.push_back("res_scale");
	mReservedUniforms.push_back("dof_width");
	mReservedUniforms.push_back("dof_height");

	mReservedUniforms.push_back("depthMap");
	mReservedUniforms.push_back("shadowMap0");
	mReservedUniforms.push_back("shadowMap1");
	mReservedUniforms.push_back("shadowMap2");
	mReservedUniforms.push_back("shadowMap3");
	mReservedUniforms.push_back("shadowMap4");
	mReservedUniforms.push_back("shadowMap5");

	llassert(mReservedUniforms.size() == LLShaderMgr::DEFERRED_SHADOW5+1);

	mReservedUniforms.push_back("normalMap");
	mReservedUniforms.push_back("positionMap");
	mReservedUniforms.push_back("diffuseRect");
	mReservedUniforms.push_back("specularRect");
    mReservedUniforms.push_back("emissiveRect");
    mReservedUniforms.push_back("brdfLut");
	mReservedUniforms.push_back("noiseMap");
	mReservedUniforms.push_back("lightFunc");
	mReservedUniforms.push_back("lightMap");
	mReservedUniforms.push_back("bloomMap");
	mReservedUniforms.push_back("projectionMap");
	mReservedUniforms.push_back("norm_mat");
	mReservedUniforms.push_back("texture_gamma");
	
	mReservedUniforms.push_back("specular_color");
	mReservedUniforms.push_back("env_intensity");

	mReservedUniforms.push_back("matrixPalette");
	mReservedUniforms.push_back("translationPalette");
	
	mReservedUniforms.push_back("screenTex");
	mReservedUniforms.push_back("screenDepth");
	mReservedUniforms.push_back("refTex");
	mReservedUniforms.push_back("eyeVec");
	mReservedUniforms.push_back("time");
	mReservedUniforms.push_back("waveDir1");
	mReservedUniforms.push_back("waveDir2");
	mReservedUniforms.push_back("lightDir");
	mReservedUniforms.push_back("specular");
	mReservedUniforms.push_back("lightExp");
	mReservedUniforms.push_back("waterFogColor");
    mReservedUniforms.push_back("waterFogColorLinear");
	mReservedUniforms.push_back("waterFogDensity");
	mReservedUniforms.push_back("waterFogKS");
	mReservedUniforms.push_back("refScale");
	mReservedUniforms.push_back("waterHeight");
	mReservedUniforms.push_back("waterPlane");
	mReservedUniforms.push_back("normScale");
	mReservedUniforms.push_back("fresnelScale");
	mReservedUniforms.push_back("fresnelOffset");
	mReservedUniforms.push_back("blurMultiplier");
	mReservedUniforms.push_back("sunAngle");
	mReservedUniforms.push_back("scaledAngle");
	mReservedUniforms.push_back("sunAngle2");
	
	mReservedUniforms.push_back("camPosLocal");

	mReservedUniforms.push_back("gWindDir");
	mReservedUniforms.push_back("gSinWaveParams");
	mReservedUniforms.push_back("gGravity");

	mReservedUniforms.push_back("detail_0");
	mReservedUniforms.push_back("detail_1");
	mReservedUniforms.push_back("detail_2");
	mReservedUniforms.push_back("detail_3");
	mReservedUniforms.push_back("alpha_ramp");

	mReservedUniforms.push_back("origin");
	mReservedUniforms.push_back("display_gamma");

    mReservedUniforms.push_back("inscatter");
    mReservedUniforms.push_back("sun_size");
    mReservedUniforms.push_back("fog_color");

    mReservedUniforms.push_back("transmittance_texture");
    mReservedUniforms.push_back("scattering_texture");
    mReservedUniforms.push_back("single_mie_scattering_texture");
    mReservedUniforms.push_back("irradiance_texture");
    mReservedUniforms.push_back("blend_factor");
    mReservedUniforms.push_back("no_atmo");
    mReservedUniforms.push_back("moisture_level");
    mReservedUniforms.push_back("droplet_radius");
    mReservedUniforms.push_back("ice_level");
    mReservedUniforms.push_back("rainbow_map");
    mReservedUniforms.push_back("halo_map");
    mReservedUniforms.push_back("moon_brightness");
    mReservedUniforms.push_back("cloud_variance");
    mReservedUniforms.push_back("reflection_probe_ambiance");

    mReservedUniforms.push_back("sh_input_r");
    mReservedUniforms.push_back("sh_input_g");
    mReservedUniforms.push_back("sh_input_b");

    mReservedUniforms.push_back("sun_moon_glow_factor");
    mReservedUniforms.push_back("water_edge");
    mReservedUniforms.push_back("sun_up_factor");
    mReservedUniforms.push_back("moonlight_color");
    mReservedUniforms.push_back("moonlight_linear");
    mReservedUniforms.push_back("sunlight_linear");
    mReservedUniforms.push_back("ambient_linear");

	llassert(mReservedUniforms.size() == END_RESERVED_UNIFORMS);

	std::set<std::string> dupe_check;

	for (U32 i = 0; i < mReservedUniforms.size(); ++i)
	{
		if (dupe_check.find(mReservedUniforms[i]) != dupe_check.end())
		{
			LL_ERRS() << "Duplicate reserved uniform name found: " << mReservedUniforms[i] << LL_ENDL;
		}
		dupe_check.insert(mReservedUniforms[i]);
	}
}