//
//  Created by Sam Gateau on 2017/04/13
//  Copyright 2013-2017 High Fidelity, Inc.
//
//  Distributed under the Apache License, Version 2.0.
//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
//
#include "GLBackend.h"
#include "GLShader.h"
#include <gl/GLShaders.h>

using namespace gpu;
using namespace gpu::gl;
using CachedShader = ::gl::CachedShader;


// Shader domain
static const size_t NUM_SHADER_DOMAINS = 3;
static_assert(Shader::Type::NUM_DOMAINS == NUM_SHADER_DOMAINS, "GL shader domains must equal defined GPU shader domains");

// GL Shader type enums
// Must match the order of type specified in gpu::Shader::Type
static const std::array<GLenum, NUM_SHADER_DOMAINS> SHADER_DOMAINS{ {
    GL_VERTEX_SHADER,
    GL_FRAGMENT_SHADER,
    GL_GEOMETRY_SHADER,
} };

// Domain specific defines
// Must match the order of type specified in gpu::Shader::Type
static const std::array<std::string, NUM_SHADER_DOMAINS> DOMAIN_DEFINES{ {
    "#define GPU_VERTEX_SHADER",
    "#define GPU_PIXEL_SHADER",
    "#define GPU_GEOMETRY_SHADER",
} };

// Stereo specific defines
static const std::string stereoVersion{
#ifdef GPU_STEREO_DRAWCALL_INSTANCED
R"SHADER(
#define GPU_TRANSFORM_IS_STEREO
#define GPU_TRANSFORM_STEREO_CAMERA
#define GPU_TRANSFORM_STEREO_CAMERA_INSTANCED
#define GPU_TRANSFORM_STEREO_SPLIT_SCREEN
)SHADER"
#endif
#ifdef GPU_STEREO_DRAWCALL_DOUBLED
#ifdef GPU_STEREO_CAMERA_BUFFER
R"SHADER(
#define GPU_TRANSFORM_IS_STEREO
#define GPU_TRANSFORM_STEREO_CAMERA
#define GPU_TRANSFORM_STEREO_CAMERA_ATTRIBUTED
)SHADER"
#else
R"SHADER(
#define GPU_TRANSFORM_IS_STEREO
)SHADER"
#endif
#endif
};

// TextureTable specific defines
static const std::string textureTableVersion {
    "#extension GL_ARB_bindless_texture : require\n#define GPU_TEXTURE_TABLE_BINDLESS\n"
};

// Versions specific of the shader
static const std::array<std::string, GLShader::NumVersions> VERSION_DEFINES { {
    "",
    stereoVersion
} };

static std::string getShaderTypeString(Shader::Type type) {
    switch (type) {
    case Shader::Type::VERTEX:
        return "vertex";
    case Shader::Type::PIXEL:
        return "pixel";
    case Shader::Type::GEOMETRY:
        return "geometry";
    case Shader::Type::PROGRAM:
        return "program";
    default:
        qFatal("Unexpected shader type %d", type);
        Q_UNREACHABLE();
    }
}

std::string GLBackend::getShaderSource(const Shader& shader, int version) {
    if (shader.isProgram()) {
        std::string result;
        result.append("// VERSION " + std::to_string(version));
        for (const auto& subShader : shader.getShaders()) {
            result.append("//-------- ");
            result.append(getShaderTypeString(subShader->getType()));
            result.append("\n");
            result.append(subShader->getSource().getCode());
        }
        return result;
    } 

    std::string shaderDefines = getBackendShaderHeader() + "\n"
        + (supportsBindless() ? textureTableVersion : "\n")
        + DOMAIN_DEFINES[shader.getType()] + "\n"
        + VERSION_DEFINES[version];

    return shaderDefines + "\n" + shader.getSource().getCode();
}

GLShader* GLBackend::compileBackendShader(const Shader& shader, const Shader::CompilationHandler& handler) {
    // Any GLSLprogram ? normally yes...
    GLenum shaderDomain = SHADER_DOMAINS[shader.getType()];
    GLShader::ShaderObjects shaderObjects;
    Shader::CompilationLogs compilationLogs(GLShader::NumVersions);
    shader.incrementCompilationAttempt();

    for (int version = 0; version < GLShader::NumVersions; version++) {
        auto& shaderObject = shaderObjects[version];
        auto shaderSource = getShaderSource(shader, version);
        if (handler) {
            bool retest = true;
            std::string currentSrc = shaderSource;
            // When a Handler is specified, we can try multiple times to build the shader and let the handler change the source if the compilation fails.
            // The retest bool is set to false as soon as the compilation succeed to wexit the while loop.
            // The handler tells us if we should retry or not while returning a modified version of the source.
            while (retest) {
                bool result = ::gl::compileShader(shaderDomain, currentSrc, shaderObject.glshader, compilationLogs[version].message);
                compilationLogs[version].compiled = result;
                if (!result) {
                    std::string newSrc;
                    retest = handler(shader, currentSrc, compilationLogs[version], newSrc);
                    currentSrc = newSrc;
                } else {
                    retest = false;
                }
            }
        } else {
            compilationLogs[version].compiled = ::gl::compileShader(shaderDomain, shaderSource, shaderObject.glshader, compilationLogs[version].message);
        }

        if (!compilationLogs[version].compiled) {
            qCWarning(gpugllogging) << "GLBackend::compileBackendProgram - Shader didn't compile:\n" << compilationLogs[version].message.c_str();
            shader.setCompilationLogs(compilationLogs);
            return nullptr;
        }
    }
    // Compilation feedback
    shader.setCompilationLogs(compilationLogs);

    // So far so good, the shader is created successfully
    GLShader* object = new GLShader(this->shared_from_this());
    object->_shaderObjects = shaderObjects;

    return object;
}

std::atomic<size_t> gpuBinaryShadersLoaded;

GLShader* GLBackend::compileBackendProgram(const Shader& program, const Shader::CompilationHandler& handler) {
    if (!program.isProgram()) {
        return nullptr;
    }

    GLShader::ShaderObjects programObjects;
    program.incrementCompilationAttempt();
    Shader::CompilationLogs compilationLogs(GLShader::NumVersions);

    for (int version = 0; version < GLShader::NumVersions; version++) {
        auto& programObject = programObjects[version];
        auto programSource = getShaderSource(program, version);
        auto hash = ::gl::getShaderHash(programSource);

        CachedShader cachedBinary;
        {
            Lock shaderCacheLock{ _shaderBinaryCache._mutex };
            if (_shaderBinaryCache._binaries.count(hash) != 0) {
                cachedBinary = _shaderBinaryCache._binaries[hash];
            }
        }


        GLuint glprogram = 0;

        // If we have a cached binary program, try to load it instead of compiling the individual shaders
        if (cachedBinary) {
            glprogram = ::gl::compileProgram({}, compilationLogs[version].message, cachedBinary);
            if (0 != glprogram) {
                ++gpuBinaryShadersLoaded;
            }
        }

        // If we have no program, then either no cached binary, or the binary failed to load (perhaps a GPU driver update invalidated the cache)
        if (0 == glprogram) {
            cachedBinary = CachedShader();
            {
                std::unique_lock<std::mutex> shaderCacheLock{ _shaderBinaryCache._mutex };
                _shaderBinaryCache._binaries.erase(hash);
            }
            // Let's go through every shaders and make sure they are ready to go
            std::vector<GLuint> shaderGLObjects;
            shaderGLObjects.reserve(program.getShaders().size());
            for (auto subShader : program.getShaders()) {
                auto object = GLShader::sync((*this), *subShader, handler);
                if (object) {
                    shaderGLObjects.push_back(object->_shaderObjects[version].glshader);
                } else {
                    qCWarning(gpugllogging) << "GLBackend::compileBackendProgram - One of the shaders of the program is not compiled?";
                    compilationLogs[version].compiled = false;
                    compilationLogs[version].message = std::string("Failed to compile, one of the shaders of the program is not compiled ?");
                    program.setCompilationLogs(compilationLogs);
                    return nullptr;
                }
            }

            glprogram = ::gl::compileProgram(shaderGLObjects, compilationLogs[version].message, cachedBinary);
            if (cachedBinary) {
                cachedBinary.source = programSource;
                std::unique_lock<std::mutex> shaderCacheLock{ _shaderBinaryCache._mutex };
                _shaderBinaryCache._binaries[hash] = cachedBinary;
            }
        }

        if (glprogram == 0) {
            qCWarning(gpugllogging) << "GLBackend::compileBackendProgram - Program didn't link:\n" << compilationLogs[version].message.c_str(); 
            program.setCompilationLogs(compilationLogs);
            return nullptr;
        }

        compilationLogs[version].compiled = true;
        programObject.glprogram = glprogram;
        makeProgramBindings(programObject);
    }
    // Compilation feedback
    program.setCompilationLogs(compilationLogs);

    // So far so good, the program versions have all been created successfully
    GLShader* object = new GLShader(this->shared_from_this());
    object->_shaderObjects = programObjects;

    return object;
}


GLBackend::ElementResource GLBackend::getFormatFromGLUniform(GLenum gltype) {
    switch (gltype) {
    case GL_FLOAT:
        return ElementResource(Element(SCALAR, gpu::FLOAT, UNIFORM), Resource::BUFFER);
    case GL_FLOAT_VEC2:
        return ElementResource(Element(VEC2, gpu::FLOAT, UNIFORM), Resource::BUFFER);
    case GL_FLOAT_VEC3:
        return ElementResource(Element(VEC3, gpu::FLOAT, UNIFORM), Resource::BUFFER);
    case GL_FLOAT_VEC4:
        return ElementResource(Element(VEC4, gpu::FLOAT, UNIFORM), Resource::BUFFER);

    case GL_INT:
        return ElementResource(Element(SCALAR, gpu::INT32, UNIFORM), Resource::BUFFER);
    case GL_INT_VEC2:
        return ElementResource(Element(VEC2, gpu::INT32, UNIFORM), Resource::BUFFER);
    case GL_INT_VEC3:
        return ElementResource(Element(VEC3, gpu::INT32, UNIFORM), Resource::BUFFER);
    case GL_INT_VEC4:
        return ElementResource(Element(VEC4, gpu::INT32, UNIFORM), Resource::BUFFER);

    case GL_UNSIGNED_INT:
        return ElementResource(Element(SCALAR, gpu::UINT32, UNIFORM), Resource::BUFFER);
    case GL_UNSIGNED_INT_VEC2:
        return ElementResource(Element(VEC2, gpu::UINT32, UNIFORM), Resource::BUFFER);
    case GL_UNSIGNED_INT_VEC3:
        return ElementResource(Element(VEC3, gpu::UINT32, UNIFORM), Resource::BUFFER);
    case GL_UNSIGNED_INT_VEC4:
        return ElementResource(Element(VEC4, gpu::UINT32, UNIFORM), Resource::BUFFER);

    case GL_BOOL:
        return ElementResource(Element(SCALAR, gpu::BOOL, UNIFORM), Resource::BUFFER);
    case GL_BOOL_VEC2:
        return ElementResource(Element(VEC2, gpu::BOOL, UNIFORM), Resource::BUFFER);
    case GL_BOOL_VEC3:
        return ElementResource(Element(VEC3, gpu::BOOL, UNIFORM), Resource::BUFFER);
    case GL_BOOL_VEC4:
        return ElementResource(Element(VEC4, gpu::BOOL, UNIFORM), Resource::BUFFER);

    case GL_FLOAT_MAT2:
        return ElementResource(Element(gpu::MAT2, gpu::FLOAT, UNIFORM), Resource::BUFFER);
    case GL_FLOAT_MAT3:
        return ElementResource(Element(MAT3, gpu::FLOAT, UNIFORM), Resource::BUFFER);
    case GL_FLOAT_MAT4:
        return ElementResource(Element(MAT4, gpu::FLOAT, UNIFORM), Resource::BUFFER);

    case GL_SAMPLER_2D:
        return ElementResource(Element(SCALAR, gpu::FLOAT, SAMPLER), Resource::TEXTURE_2D);
    case GL_SAMPLER_3D:
        return ElementResource(Element(SCALAR, gpu::FLOAT, SAMPLER), Resource::TEXTURE_3D);
    case GL_SAMPLER_CUBE:
        return ElementResource(Element(SCALAR, gpu::FLOAT, SAMPLER), Resource::TEXTURE_CUBE);
    case GL_SAMPLER_2D_MULTISAMPLE:
        return ElementResource(Element(SCALAR, gpu::FLOAT, SAMPLER_MULTISAMPLE), Resource::TEXTURE_2D);
    case GL_SAMPLER_2D_ARRAY:
        return ElementResource(Element(SCALAR, gpu::FLOAT, SAMPLER), Resource::TEXTURE_2D_ARRAY);
    case GL_SAMPLER_2D_MULTISAMPLE_ARRAY:
        return ElementResource(Element(SCALAR, gpu::FLOAT, SAMPLER_MULTISAMPLE), Resource::TEXTURE_2D_ARRAY);
    case GL_SAMPLER_2D_SHADOW:
        return ElementResource(Element(SCALAR, gpu::FLOAT, SAMPLER_SHADOW), Resource::TEXTURE_2D);
    case GL_SAMPLER_CUBE_SHADOW:
        return ElementResource(Element(SCALAR, gpu::FLOAT, SAMPLER_SHADOW), Resource::TEXTURE_CUBE);
    case GL_SAMPLER_2D_ARRAY_SHADOW:
        return ElementResource(Element(SCALAR, gpu::FLOAT, SAMPLER_SHADOW), Resource::TEXTURE_2D_ARRAY);
    case GL_SAMPLER_BUFFER:
        return ElementResource(Element(SCALAR, gpu::FLOAT, RESOURCE_BUFFER), Resource::BUFFER);
    case GL_INT_SAMPLER_2D:
        return ElementResource(Element(SCALAR, gpu::INT32, SAMPLER), Resource::TEXTURE_2D);
    case GL_INT_SAMPLER_2D_MULTISAMPLE:
        return ElementResource(Element(SCALAR, gpu::INT32, SAMPLER_MULTISAMPLE), Resource::TEXTURE_2D);
    case GL_INT_SAMPLER_3D:
        return ElementResource(Element(SCALAR, gpu::INT32, SAMPLER), Resource::TEXTURE_3D);
    case GL_INT_SAMPLER_CUBE:
        return ElementResource(Element(SCALAR, gpu::INT32, SAMPLER), Resource::TEXTURE_CUBE);
    case GL_INT_SAMPLER_2D_ARRAY:
        return ElementResource(Element(SCALAR, gpu::INT32, SAMPLER), Resource::TEXTURE_2D_ARRAY);
    case GL_INT_SAMPLER_2D_MULTISAMPLE_ARRAY:
        return ElementResource(Element(SCALAR, gpu::INT32, SAMPLER_MULTISAMPLE), Resource::TEXTURE_2D_ARRAY);
    case GL_UNSIGNED_INT_SAMPLER_2D:
        return ElementResource(Element(SCALAR, gpu::UINT32, SAMPLER), Resource::TEXTURE_2D);
    case GL_UNSIGNED_INT_SAMPLER_2D_MULTISAMPLE:
        return ElementResource(Element(SCALAR, gpu::UINT32, SAMPLER_MULTISAMPLE), Resource::TEXTURE_2D);
    case GL_UNSIGNED_INT_SAMPLER_3D:
        return ElementResource(Element(SCALAR, gpu::UINT32, SAMPLER), Resource::TEXTURE_3D);
    case GL_UNSIGNED_INT_SAMPLER_CUBE:
        return ElementResource(Element(SCALAR, gpu::UINT32, SAMPLER), Resource::TEXTURE_CUBE);
    case GL_UNSIGNED_INT_SAMPLER_2D_ARRAY:
        return ElementResource(Element(SCALAR, gpu::UINT32, SAMPLER), Resource::TEXTURE_2D_ARRAY);
    case GL_UNSIGNED_INT_SAMPLER_2D_MULTISAMPLE_ARRAY:
        return ElementResource(Element(SCALAR, gpu::UINT32, SAMPLER_MULTISAMPLE), Resource::TEXTURE_2D_ARRAY);

#if !defined(USE_GLES)
    case GL_SAMPLER_1D:
        return ElementResource(Element(SCALAR, gpu::FLOAT, SAMPLER), Resource::TEXTURE_1D);
    case GL_SAMPLER_1D_ARRAY:
        return ElementResource(Element(SCALAR, gpu::FLOAT, SAMPLER), Resource::TEXTURE_1D_ARRAY);
    case GL_INT_SAMPLER_1D:
        return ElementResource(Element(SCALAR, gpu::INT32, SAMPLER), Resource::TEXTURE_1D);
    case GL_INT_SAMPLER_1D_ARRAY:
        return ElementResource(Element(SCALAR, gpu::INT32, SAMPLER), Resource::TEXTURE_1D_ARRAY);
    case GL_UNSIGNED_INT_SAMPLER_1D:
        return ElementResource(Element(SCALAR, gpu::UINT32, SAMPLER), Resource::TEXTURE_1D);
    case GL_UNSIGNED_INT_SAMPLER_1D_ARRAY:
        return ElementResource(Element(SCALAR, gpu::UINT32, SAMPLER), Resource::TEXTURE_1D_ARRAY);
#endif

    default:
        return ElementResource(Element(), Resource::BUFFER);
    }

    // Non-covered types
    //{GL_FLOAT_MAT2x3    mat2x3},
    //{GL_FLOAT_MAT2x4    mat2x4},
    //{GL_FLOAT_MAT3x2    mat3x2},
    //{GL_FLOAT_MAT3x4    mat3x4},
    //{GL_FLOAT_MAT4x2    mat4x2},
    //{GL_FLOAT_MAT4x3    mat4x3},
    //{GL_DOUBLE_MAT2    dmat2},
    //{GL_DOUBLE_MAT3    dmat3},
    //{GL_DOUBLE_MAT4    dmat4},
    //{GL_DOUBLE_MAT2x3    dmat2x3},
    //{GL_DOUBLE_MAT2x4    dmat2x4},
    //{GL_DOUBLE_MAT3x2    dmat3x2},
    //{GL_DOUBLE_MAT3x4    dmat3x4},
    //{GL_DOUBLE_MAT4x2    dmat4x2},
    //{GL_DOUBLE_MAT4x3    dmat4x3},
    //{GL_SAMPLER_1D_SHADOW    sampler1DShadow},
    //{GL_SAMPLER_1D_ARRAY_SHADOW    sampler1DArrayShadow},
    //{GL_SAMPLER_2D_RECT    sampler2DRect},
    //{GL_SAMPLER_2D_RECT_SHADOW    sampler2DRectShadow},
    //{GL_INT_SAMPLER_BUFFER    isamplerBuffer},
    //{GL_INT_SAMPLER_2D_RECT    isampler2DRect},
    //{GL_UNSIGNED_INT_SAMPLER_BUFFER    usamplerBuffer},
    //{GL_UNSIGNED_INT_SAMPLER_2D_RECT    usampler2DRect},
    //{GL_IMAGE_1D    image1D},
    //{GL_IMAGE_2D    image2D},
    //{GL_IMAGE_3D    image3D},
    //{GL_IMAGE_2D_RECT    image2DRect},
    //{GL_IMAGE_CUBE    imageCube},
    //{GL_IMAGE_BUFFER    imageBuffer},
    //{GL_IMAGE_1D_ARRAY    image1DArray},
    //{GL_IMAGE_2D_ARRAY    image2DArray},
    //{GL_IMAGE_2D_MULTISAMPLE    image2DMS},
    //{GL_IMAGE_2D_MULTISAMPLE_ARRAY    image2DMSArray},
    //{GL_INT_IMAGE_1D    iimage1D},
    //{GL_INT_IMAGE_2D    iimage2D},
    //{GL_INT_IMAGE_3D    iimage3D},
    //{GL_INT_IMAGE_2D_RECT    iimage2DRect},
    //{GL_INT_IMAGE_CUBE    iimageCube},
    //{GL_INT_IMAGE_BUFFER    iimageBuffer},
    //{GL_INT_IMAGE_1D_ARRAY    iimage1DArray},
    //{GL_INT_IMAGE_2D_ARRAY    iimage2DArray},
    //{GL_INT_IMAGE_2D_MULTISAMPLE    iimage2DMS},
    //{GL_INT_IMAGE_2D_MULTISAMPLE_ARRAY    iimage2DMSArray},
    //{GL_UNSIGNED_INT_IMAGE_1D    uimage1D},
    //{GL_UNSIGNED_INT_IMAGE_2D    uimage2D},
    //{GL_UNSIGNED_INT_IMAGE_3D    uimage3D},
    //{GL_UNSIGNED_INT_IMAGE_2D_RECT    uimage2DRect},
    //{GL_UNSIGNED_INT_IMAGE_CUBE    uimageCube},
    //{GL_UNSIGNED_INT_IMAGE_BUFFER    uimageBuffer},
    //{GL_UNSIGNED_INT_IMAGE_1D_ARRAY    uimage1DArray},
    //{GL_UNSIGNED_INT_IMAGE_2D_ARRAY    uimage2DArray},
    //{GL_UNSIGNED_INT_IMAGE_2D_MULTISAMPLE    uimage2DMS},
    //{GL_UNSIGNED_INT_IMAGE_2D_MULTISAMPLE_ARRAY    uimage2DMSArray},
    //{GL_UNSIGNED_INT_ATOMIC_COUNTER    atomic_uint}


};

int GLBackend::makeUniformSlots(const ShaderObject& shaderProgram, const Shader::BindingSet& slotBindings,
    Shader::SlotSet& uniforms, Shader::SlotSet& textures, Shader::SlotSet& samplers) {
    auto& glprogram = shaderProgram.glprogram;

    for (const auto& uniform : shaderProgram.uniforms) {
        const auto& type = uniform.type;
        const auto& location = uniform.location;
        const auto& size = uniform.size;
        const auto& name = uniform.name;
        const GLint INVALID_UNIFORM_LOCATION = -1;

        // Try to make sense of the gltype
        auto elementResource = getFormatFromGLUniform(type);

        // The uniform as a standard var type
        if (location != INVALID_UNIFORM_LOCATION) {
            auto sname = uniform.name;
            // Let's make sure the name doesn't contains an array element
            auto foundBracket = sname.find_first_of('[');
            if (foundBracket != std::string::npos) {
                //  std::string arrayname = sname.substr(0, foundBracket);

                if (sname[foundBracket + 1] == '0') {
                    sname = sname.substr(0, foundBracket);
                } else {
                    // skip this uniform since it's not the first element of an array
                    continue;
                }
            }

            if (elementResource._resource == Resource::BUFFER) {
                uniforms.insert(Shader::Slot(sname, location, elementResource._element, elementResource._resource));
            } else {
                // For texture/Sampler, the location is the actual binding value
                GLint binding = -1;
                glGetUniformiv(glprogram, location, &binding);

                auto requestedBinding = slotBindings.find(std::string(sname));
                if (requestedBinding != slotBindings.end()) {
                    if (binding != (*requestedBinding)._location) {
                        binding = (*requestedBinding)._location;
                        for (auto i = 0; i < size; i++) {
                            // If we are working with an array of textures, reserve for each elemet
                            glProgramUniform1i(glprogram, location+i, binding+i);
                        }
                    }
                }

                textures.insert(Shader::Slot(name, binding, elementResource._element, elementResource._resource));
                samplers.insert(Shader::Slot(name, binding, elementResource._element, elementResource._resource));
            }
        }
    }

    return static_cast<uint32_t>(shaderProgram.uniforms.size());
}

int GLBackend::makeUniformBlockSlots(const ShaderObject& shaderProgram, const Shader::BindingSet& slotBindings, Shader::SlotSet& buffers) {
    const auto& glprogram = shaderProgram.glprogram;
    GLint buffersCount = 0;

    glGetProgramiv(glprogram, GL_ACTIVE_UNIFORM_BLOCKS, &buffersCount);

    // fast exit
    if (buffersCount == 0) {
        return 0;
    }

    GLint maxNumUniformBufferSlots = 0;
    glGetIntegerv(GL_MAX_UNIFORM_BUFFER_BINDINGS, &maxNumUniformBufferSlots);
    std::vector<GLint> uniformBufferSlotMap(maxNumUniformBufferSlots, -1);

    struct UniformBlockInfo {
        using Vector = std::vector<UniformBlockInfo>;
        const GLuint index{ 0 };
        const std::string name;
        GLint binding{ -1 };
        GLint size{ 0 };

        static std::string getName(GLuint glprogram, GLuint i) {
            static const GLint NAME_LENGTH = 256;
            GLint length = 0;
            GLchar nameBuffer[NAME_LENGTH];
            glGetActiveUniformBlockiv(glprogram, i, GL_UNIFORM_BLOCK_NAME_LENGTH, &length);
            glGetActiveUniformBlockName(glprogram, i, NAME_LENGTH, &length, nameBuffer);
            return std::string(nameBuffer);
        }

        UniformBlockInfo(GLuint glprogram, GLuint i) : index(i), name(getName(glprogram, i)) {
            glGetActiveUniformBlockiv(glprogram, index, GL_UNIFORM_BLOCK_BINDING, &binding);
            glGetActiveUniformBlockiv(glprogram, index, GL_UNIFORM_BLOCK_DATA_SIZE, &size);
        }
    };

    UniformBlockInfo::Vector uniformBlocks;
    uniformBlocks.reserve(buffersCount);
    for (int i = 0; i < buffersCount; i++) {
        uniformBlocks.push_back(UniformBlockInfo(glprogram, i));
    }

    for (auto& info : uniformBlocks) {
        auto requestedBinding = slotBindings.find(info.name);
        if (requestedBinding != slotBindings.end()) {
            info.binding = (*requestedBinding)._location;
            glUniformBlockBinding(glprogram, info.index, info.binding);
            uniformBufferSlotMap[info.binding] = info.index;
        }
    }

    for (auto& info : uniformBlocks) {
        if (slotBindings.count(info.name)) {
            continue;
        }

        // If the binding is 0, or the binding maps to an already used binding
        if (info.binding == 0 || !isUnusedSlot(uniformBufferSlotMap[info.binding])) {
            // If no binding was assigned then just do it finding a free slot
            auto slotIt = std::find_if(uniformBufferSlotMap.begin(), uniformBufferSlotMap.end(), GLBackend::isUnusedSlot);
            if (slotIt != uniformBufferSlotMap.end()) {
                info.binding = slotIt - uniformBufferSlotMap.begin();
                glUniformBlockBinding(glprogram, info.index, info.binding);
            } else {
                // This should neve happen, an active ubo cannot find an available slot among the max available?!
                info.binding = -1;
            }
        }

        uniformBufferSlotMap[info.binding] = info.index;
    }

    for (auto& info : uniformBlocks) {
        static const Element element(SCALAR, gpu::UINT32, gpu::UNIFORM_BUFFER);
        buffers.insert(Shader::Slot(info.name, info.binding, element, Resource::BUFFER, info.size));
    }
    return buffersCount;
}

int GLBackend::makeInputSlots(const ShaderObject& shaderProgram, const Shader::BindingSet& slotBindings, Shader::SlotSet& inputs) {
    const auto& glprogram = shaderProgram.glprogram;
    GLint inputsCount = 0;

    glGetProgramiv(glprogram, GL_ACTIVE_ATTRIBUTES, &inputsCount);

    for (int i = 0; i < inputsCount; i++) {
        const GLint NAME_LENGTH = 256;
        GLchar name[NAME_LENGTH];
        GLint length = 0;
        GLint size = 0;
        GLenum type = 0;
        glGetActiveAttrib(glprogram, i, NAME_LENGTH, &length, &size, &type, name);

        GLint binding = glGetAttribLocation(glprogram, name);

        auto elementResource = getFormatFromGLUniform(type);
        inputs.insert(Shader::Slot(name, binding, elementResource._element, -1));
    }

    return inputsCount;
}

int GLBackend::makeOutputSlots(const ShaderObject& shaderProgram, const Shader::BindingSet& slotBindings, Shader::SlotSet& outputs) {
    /*   GLint outputsCount = 0;

    glGetProgramiv(glprogram, GL_ACTIVE_, &outputsCount);

    for (int i = 0; i < inputsCount; i++) {
    const GLint NAME_LENGTH = 256;
    GLchar name[NAME_LENGTH];
    GLint length = 0;
    GLint size = 0;
    GLenum type = 0;
    glGetActiveAttrib(glprogram, i, NAME_LENGTH, &length, &size, &type, name);

    auto element = getFormatFromGLUniform(type);
    outputs.insert(Shader::Slot(name, i, element));
    }
    */
    return 0; //inputsCount;
}

void GLBackend::makeProgramBindings(ShaderObject& shaderObject) {
    if (!shaderObject.glprogram) {
        return;
    }
}


void GLBackend::initShaderBinaryCache() {
    GLint numBinFormats = 0;
    glGetIntegerv(GL_NUM_PROGRAM_BINARY_FORMATS, &numBinFormats);
    if (numBinFormats > 0) {
        _shaderBinaryCache._formats.resize(numBinFormats);
        glGetIntegerv(GL_PROGRAM_BINARY_FORMATS, _shaderBinaryCache._formats.data());
    }
    ::gl::loadShaderCache(_shaderBinaryCache._binaries);
}

void GLBackend::killShaderBinaryCache() {
    ::gl::saveShaderCache(_shaderBinaryCache._binaries);
}