// render-gl.cpp
#include "render-gl.h"

#include "options.h"
#include "render.h"

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include "core/basic.h"
#include "core/secure-crt.h"
#include "external/stb/stb_image_write.h"

// TODO(tfoley): eventually we should be able to run these
// tests on non-Windows targets to confirm that cross-compilation
// at least *works* on those platforms...
#define WIN32_LEAN_AND_MEAN
#define NOMINMAX
#include <Windows.h>
#undef WIN32_LEAN_AND_MEAN
#undef NOMINMAX

#ifdef _MSC_VER
#include <stddef.h>
#if (_MSC_VER < 1900)
#define snprintf sprintf_s
#endif
#endif

#pragma comment(lib, "opengl32")

#include <GL/GL.h>
#include "external/glext.h"

// We define an "X-macro" for mapping over loadable OpenGL
// extension entry point that we will use, so that we can
// easily write generic code to iterate over them.
#define MAP_GL_EXTENSION_FUNCS(F)                       \
    F(glCreateProgram,      PFNGLCREATEPROGRAMPROC)     \
    F(glCreateShader,       PFNGLCREATESHADERPROC)      \
    F(glShaderSource,       PFNGLSHADERSOURCEPROC)      \
    F(glCompileShader,      PFNGLCOMPILESHADERPROC)     \
    F(glGetShaderiv,        PFNGLGETSHADERIVPROC)       \
    F(glDeleteShader,       PFNGLDELETESHADERPROC)      \
    F(glAttachShader,       PFNGLATTACHSHADERPROC)      \
    F(glLinkProgram,        PFNGLLINKPROGRAMPROC)       \
    F(glGetProgramiv,       PFNGLGETPROGRAMIVPROC)      \
    F(glGetProgramInfoLog,  PFNGLGETPROGRAMINFOLOGPROC) \
    F(glDeleteProgram,      PFNGLDELETEPROGRAMPROC)     \
    F(glGetShaderInfoLog,   PFNGLGETSHADERINFOLOGPROC)  \
    F(glGenBuffers,         PFNGLGENBUFFERSPROC)        \
    F(glBindBuffer,         PFNGLBINDBUFFERPROC)        \
    F(glBufferData,         PFNGLBUFFERDATAPROC)        \
	F(glDeleteBuffers,		PFNGLDELETEBUFFERSPROC)		\
	F(glMapBuffer,          PFNGLMAPBUFFERPROC)         \
    F(glUnmapBuffer,        PFNGLUNMAPBUFFERPROC)       \
    F(glUseProgram,         PFNGLUSEPROGRAMPROC)        \
    F(glBindBufferBase,     PFNGLBINDBUFFERBASEPROC)    \
    F(glVertexAttribPointer,        PFNGLVERTEXATTRIBPOINTERPROC)       \
    F(glEnableVertexAttribArray,    PFNGLENABLEVERTEXATTRIBARRAYPROC)   \
    F(glDisableVertexAttribArray,   PFNGLDISABLEVERTEXATTRIBARRAYPROC)  \
    F(glDebugMessageCallback,       PFNGLDEBUGMESSAGECALLBACKPROC)      \
    F(glDispatchCompute,            PFNGLDISPATCHCOMPUTEPROC) \
    F(glActiveTexture,              PFNGLACTIVETEXTUREPROC) \
    F(glCreateSamplers,             PFNGLCREATESAMPLERSPROC) \
	F(glDeleteSamplers,				PFNGLDELETESAMPLERSPROC) \
    F(glBindSampler,                PFNGLBINDSAMPLERPROC) \
    F(glTexImage3D,                 PFNGLTEXIMAGE3DPROC) \
    F(glSamplerParameteri,          PFNGLSAMPLERPARAMETERIPROC) \
    /* end */

using namespace Slang;

namespace renderer_test {

class GLRenderer : public Renderer, public ShaderCompiler
{
public:
    
    // Renderer    implementation
    virtual SlangResult initialize(void* inWindowHandle) override;
    virtual void setClearColor(const float color[4]) override;
    virtual void clearFrame() override;
    virtual void presentFrame() override;
    virtual SlangResult captureScreenShot(char const* outputPath) override;
    virtual void serializeOutput(BindingState* state, const char* fileName) override;
    virtual Buffer* createBuffer(const BufferDesc& desc) override;
    virtual InputLayout* createInputLayout(const InputElementDesc* inputElements, UInt inputElementCount) override;
    virtual BindingState * createBindingState(const ShaderInputLayout& layout) override;
    virtual ShaderCompiler* getShaderCompiler() override;
    virtual void* map(Buffer* buffer, MapFlavor flavor) override;
    virtual void unmap(Buffer* buffer) override;
    virtual void setInputLayout(InputLayout* inputLayout) override;
    virtual void setPrimitiveTopology(PrimitiveTopology topology) override;
    virtual void setBindingState(BindingState* state);
    virtual void setVertexBuffers(UInt startSlot, UInt slotCount, Buffer*const* buffers, const UInt* strides, const UInt* offsets) override;
    virtual void setShaderProgram(ShaderProgram* inProgram) override;
    virtual void setConstantBuffers(UInt startSlot, UInt slotCount, Buffer*const* buffers, const UInt* offsets) override;
    virtual void draw(UInt vertexCount, UInt startVertex) override;
    virtual void dispatchCompute(int x, int y, int z) override;
    virtual void submitGpuWork() override {}
    virtual void waitForGpu() override {}

    // ShaderCompiler implementation
    virtual ShaderProgram* compileProgram(const ShaderCompileRequest& request) override;

    protected:
    enum
    {
        kMaxVertexStreams = 16,
    };

    struct VertexAttributeFormat
    {
        GLint       componentCount;
        GLenum      componentType;
        GLboolean   normalized;
    };

    struct VertexAttributeDesc
    {
        VertexAttributeFormat   format;
        GLuint                  streamIndex;
        GLsizei                 offset;
    };

    class InputLayoutImpl: public InputLayout
    {
		public:
        VertexAttributeDesc m_attributes[kMaxVertexStreams];
        UInt m_attributeCount = 0;
    };

	class BufferImpl: public Buffer
	{
		public:
		BufferImpl(GLRenderer* renderer, GLuint id):
			m_renderer(renderer),
			m_id(id)
		{}
		~BufferImpl()
		{
			if (m_renderer)
			{
				m_renderer->glDeleteBuffers(1, &m_id);
			}
		}

		GLRenderer* m_renderer;
		GLuint m_id;
	};

    struct BindingEntry
    {
        ShaderInputType type;
        GLuint handle;
        List<int> binding;
        int bindTarget;
        int bufferSize;
        bool isOutput = false;
    };
    class BindingStateImpl: public BindingState
    {
		public:
		BindingStateImpl(GLRenderer* renderer):
			m_renderer(renderer)
		{
		}

		~BindingStateImpl()
		{
			if (m_renderer)
			{
				m_renderer->destroyBindingEntries(m_entries.Buffer(), int(m_entries.Count()));
			}
		}

		GLRenderer* m_renderer;
        List<BindingEntry> m_entries;
    };

	class ShaderProgramImpl : public ShaderProgram
	{
	public:
		ShaderProgramImpl(GLRenderer* renderer, GLuint id):
			m_renderer(renderer),
			m_id(id)
		{
		}
		~ShaderProgramImpl()
		{
			if (m_renderer)
			{
				m_renderer->glDeleteProgram(m_id);
			}
		}
	
		GLuint m_id;
		GLRenderer* m_renderer;
	};

	void destroyBindingEntry(const BindingEntry& entry);
	void destroyBindingEntries(const BindingEntry* entries, int numEntries);

    void bindBufferImpl(int target, UInt startSlot, UInt slotCount, Buffer*const* buffers, const UInt* offsets);
    void flushStateForDraw();
    GLuint loadShader(GLenum stage, char const* source);
    void createInputBuffer(BindingEntry& rs, InputBufferDesc bufDesc, List<unsigned int>& bufferData);
    void debugCallback(GLenum source, GLenum type, GLuint id, GLenum severity, GLsizei length, const GLchar* message);
    void createInputTexture(BindingEntry& rs, InputTextureDesc texDesc, InputSamplerDesc samplerDesc);
    void createInputSampler(BindingEntry& rs, InputSamplerDesc samplerDesc);

    static void APIENTRY staticDebugCallback(GLenum source, GLenum type, GLuint id, GLenum severity, GLsizei length, const GLchar* message, const void* userParam);
    static VertexAttributeFormat getVertexAttributeFormat(Format format);

    HDC     m_hdc;
    HGLRC   m_glContext;
    float   m_clearColor[4] = { 0, 0, 0, 0 };
    
	RefPtr<ShaderProgramImpl> m_boundShaderProgram;
    RefPtr<InputLayoutImpl> m_boundInputLayout;

    GLenum m_boundPrimitiveTopology = GL_TRIANGLES;
    GLuint  m_boundVertexStreamBuffers[kMaxVertexStreams];
    UInt    m_boundVertexStreamStrides[kMaxVertexStreams];
    UInt    m_boundVertexStreamOffsets[kMaxVertexStreams];

    // Declare a function pointer for each OpenGL
    // extension function we need to load
#define DECLARE_GL_EXTENSION_FUNC(NAME, TYPE) TYPE NAME;
    MAP_GL_EXTENSION_FUNCS(DECLARE_GL_EXTENSION_FUNC)
#undef DECLARE_GL_EXTENSION_FUNC
};

Renderer* createGLRenderer()
{
    return new GLRenderer();
}

void GLRenderer::debugCallback(GLenum source, GLenum type, GLuint id, GLenum severity, GLsizei length, const GLchar* message)
{
    ::OutputDebugStringA("GL: ");
    ::OutputDebugStringA(message);
    ::OutputDebugStringA("\n");

    switch (type)
    {
        case GL_DEBUG_TYPE_ERROR:
            break;
        default:
            break;
    }
}

/* static */void APIENTRY GLRenderer::staticDebugCallback(GLenum source, GLenum type, GLuint id, GLenum severity, GLsizei length, const GLchar* message, const void* userParam)
{
    ((GLRenderer*)userParam)->debugCallback(source, type, id, severity, length, message);
}

/* static */GLRenderer::VertexAttributeFormat GLRenderer::getVertexAttributeFormat(Format format)
{
    switch (format)
    {
        default: assert(!"unexpected"); return VertexAttributeFormat();

#define CASE(NAME, COUNT, TYPE, NORMALIZED) \
        case Format::NAME: do { VertexAttributeFormat result = {COUNT, TYPE, NORMALIZED}; return result; } while (0)

        CASE(RGB_Float32, 3, GL_FLOAT, GL_FALSE);
        CASE(RG_Float32, 2, GL_FLOAT, GL_FALSE);
#undef CASE
    }
}

void GLRenderer::bindBufferImpl(int target, UInt startSlot, UInt slotCount, Buffer*const* buffers, const UInt* offsets)
{
    for (UInt ii = 0; ii < slotCount; ++ii)
    {
        UInt slot = startSlot + ii;

        BufferImpl* buffer = static_cast<BufferImpl*>(buffers[ii]);
        GLuint bufferID = buffer ? buffer->m_id : 0;
		
        assert(!offsets || !offsets[ii]);

        glBindBufferBase(target, (GLuint)slot, bufferID);
    }
}

void GLRenderer::flushStateForDraw()
{
    auto layout = m_boundInputLayout.Ptr();
    auto attrCount = layout->m_attributeCount;
    for (UInt ii = 0; ii < attrCount; ++ii)
    {
        auto& attr = layout->m_attributes[ii];

        auto streamIndex = attr.streamIndex;

        glBindBuffer(GL_ARRAY_BUFFER, m_boundVertexStreamBuffers[streamIndex]);

        glVertexAttribPointer(
            (GLuint)ii,
            attr.format.componentCount,
            attr.format.componentType,
            attr.format.normalized,
            (GLsizei)m_boundVertexStreamStrides[streamIndex],
            (GLvoid*)(attr.offset + m_boundVertexStreamOffsets[streamIndex]));

        glEnableVertexAttribArray((GLuint)ii);
    }
    for (UInt ii = attrCount; ii < kMaxVertexStreams; ++ii)
    {
        glDisableVertexAttribArray((GLuint)ii);
    }
}

GLuint GLRenderer::loadShader(GLenum stage, const char* source)
{
    // GLSL is monumentally stupid. It officially requires the `#version` directive
    // to be the first thing in the file, which wouldn't be so bad but the API
    // doesn't provide a way to pass a `#define` into your shader other than by
    // prepending it to the whole thing.
    //
    // We are going to solve this problem by doing some surgery on the source
    // that was passed in.

    const char* sourceBegin = source;
    const char* sourceEnd = source + strlen(source);

    // Look for a version directive in the user-provided source.
    const char* versionBegin = strstr(source, "#version");
    const char* versionEnd = nullptr;
    if (versionBegin)
    {
        // If we found a directive, then scan for the end-of-line
        // after it, and use that to specify the slice.
        versionEnd = strchr(versionBegin, '\n');
        if (!versionEnd)
        {
            versionEnd = sourceEnd;
        }
        else
        {
            versionEnd = versionEnd + 1;
        }
    }
    else
    {
        // If we didn't find a directive, then treat it as being
        // a zero-byte slice at the start of the string
        versionBegin = sourceBegin;
        versionEnd = sourceBegin;
    }

    enum { kMaxSourceStringCount = 16 };
    const GLchar* sourceStrings[kMaxSourceStringCount];
    GLint sourceStringLengths[kMaxSourceStringCount];

    int sourceStringCount = 0;

    const char* stagePrelude = "\n";
    switch (stage)
    {
#define CASE(NAME) case GL_##NAME##_SHADER: stagePrelude = "#define __GLSL_" #NAME "__ 1\n"; break

        CASE(VERTEX);
        CASE(TESS_CONTROL);
        CASE(TESS_EVALUATION);
        CASE(GEOMETRY);
        CASE(FRAGMENT);
        CASE(COMPUTE);

#undef CASE
    }

    const char* prelude =
        "#define __GLSL__ 1\n"
        ;

#define ADD_SOURCE_STRING_SPAN(BEGIN, END)                              \
        sourceStrings[sourceStringCount] = BEGIN;                       \
        sourceStringLengths[sourceStringCount++] = GLint(END - BEGIN)   \
        /* end */

#define ADD_SOURCE_STRING(BEGIN)                                        \
        sourceStrings[sourceStringCount] = BEGIN;                       \
        sourceStringLengths[sourceStringCount++] = GLint(strlen(BEGIN)) \
        /* end */

    ADD_SOURCE_STRING_SPAN(versionBegin, versionEnd);
    ADD_SOURCE_STRING(stagePrelude);
    ADD_SOURCE_STRING(prelude);
    ADD_SOURCE_STRING_SPAN(sourceBegin, versionBegin);
    ADD_SOURCE_STRING_SPAN(versionEnd, sourceEnd);

    auto shaderID = glCreateShader(stage);
    glShaderSource(
        shaderID,
        sourceStringCount,
        &sourceStrings[0],
        &sourceStringLengths[0]);
    glCompileShader(shaderID);

    GLint success = GL_FALSE;
    glGetShaderiv(shaderID, GL_COMPILE_STATUS, &success);
    if (!success)
    {
        int maxSize = 0;
        glGetShaderiv(shaderID, GL_INFO_LOG_LENGTH, &maxSize);

        auto infoBuffer = (char*)malloc(maxSize);

        int infoSize = 0;
        glGetShaderInfoLog(shaderID, maxSize, &infoSize, infoBuffer);
        if (infoSize > 0)
        {
            fprintf(stderr, "%s", infoBuffer);
            ::OutputDebugStringA(infoBuffer);
        }

        glDeleteShader(shaderID);
        return 0;
    }

    return shaderID;
}

void GLRenderer::destroyBindingEntry(const BindingEntry& entry)
{
	switch (entry.type)
	{
		case ShaderInputType::Buffer:
		{
			glDeleteBuffers(1, &entry.handle);
			break;
		}
		case ShaderInputType::Texture:
		case ShaderInputType::CombinedTextureSampler:
		{
			glDeleteTextures(1, &entry.handle);
			break;
		}
		case ShaderInputType::Sampler:
		{
			glDeleteSamplers(1, &entry.handle);
			break;
		}
		default: break;
	}
}

void GLRenderer::destroyBindingEntries(const BindingEntry* entries, int numEntries)
{
	for (int i = 0; i < numEntries; ++i)
	{
		destroyBindingEntry(entries[i]);
	}
}

void GLRenderer::createInputBuffer(BindingEntry& rs, InputBufferDesc bufDesc, List<unsigned int>& bufferData)
{
    rs.bindTarget = (bufDesc.type == InputBufferType::StorageBuffer ? GL_SHADER_STORAGE_BUFFER : GL_UNIFORM_BUFFER);
    glGenBuffers(1, &rs.handle);
    glBindBuffer(rs.bindTarget, rs.handle);
    glBufferData(rs.bindTarget, bufferData.Count() * sizeof(unsigned int), bufferData.Buffer(), GL_STATIC_READ);
    glBindBuffer(rs.bindTarget, 0);
}

void GLRenderer::createInputTexture(BindingEntry& rs, InputTextureDesc texDesc, InputSamplerDesc samplerDesc)
{
    TextureData texData;
    generateTextureData(texData, texDesc);
    glGenTextures(1, &rs.handle);
    switch (texDesc.dimension)
    {
        case 1:
            if (texDesc.arrayLength > 0)
            {
                rs.bindTarget = GL_TEXTURE_1D_ARRAY;
                glBindTexture(rs.bindTarget, rs.handle);
                int slice = 0;
                for (int i = 0; i < texData.arraySize; i++)
				{
                    for (int j = 0; j < texData.mipLevels; j++)
                    {
                        glTexImage2D(rs.bindTarget, j, GL_RGBA8, texData.textureSize, i, 0, GL_RGBA, GL_UNSIGNED_BYTE, texData.dataBuffer[slice].Buffer());
                        slice++;
                    }
				}
            }
            else
            {
                rs.bindTarget = GL_TEXTURE_1D;
                glBindTexture(rs.bindTarget, rs.handle);
                for (int i = 0; i < texData.mipLevels; i++)
                    glTexImage1D(rs.bindTarget, i, GL_RGBA8, texData.textureSize, 0, GL_RGBA, GL_UNSIGNED_BYTE, texData.dataBuffer[i].Buffer());
            }
            break;
        case 2:
            if (texDesc.arrayLength > 0)
            {
                if (texDesc.isCube)
                    rs.bindTarget = GL_TEXTURE_CUBE_MAP_ARRAY;
                else
                    rs.bindTarget = GL_TEXTURE_2D_ARRAY;
                glBindTexture(rs.bindTarget, rs.handle);
                for (auto i = 0u; i < texData.dataBuffer.Count(); i++)
                    glTexImage3D(rs.bindTarget, i % texData.mipLevels, GL_RGBA8, texData.textureSize, texData.textureSize, i, 0, GL_RGBA, GL_UNSIGNED_BYTE, texData.dataBuffer[i].Buffer());
            }
            else
            {
                if (texDesc.isCube)
                {
                    rs.bindTarget = GL_TEXTURE_CUBE_MAP;
                    glBindTexture(rs.bindTarget, rs.handle);
                    for (int j = 0; j < 6; j++)
                    {
                        for (int i = 0; i < texData.mipLevels; i++)
                            glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + j, i, GL_RGBA8, texData.textureSize, texData.textureSize, 0, GL_RGBA, GL_UNSIGNED_BYTE, texData.dataBuffer[i + j*texData.mipLevels].Buffer());
                    }
                }
                else
                {
                    rs.bindTarget = GL_TEXTURE_2D;
                    glBindTexture(rs.bindTarget, rs.handle);
                    for (int i = 0; i < texData.mipLevels; i++)
                        glTexImage2D(rs.bindTarget, i, GL_RGBA8, texData.textureSize, texData.textureSize, 0, GL_RGBA, GL_UNSIGNED_BYTE, texData.dataBuffer[i].Buffer());
                }
            }
            break;
        case 3:
            rs.bindTarget = GL_TEXTURE_3D;
            glBindTexture(rs.bindTarget, rs.handle);
            for (int i = 0; i < texData.mipLevels; i++)
                glTexImage3D(rs.bindTarget, i, GL_RGBA8, texData.textureSize, texData.textureSize, texData.textureSize, 0, GL_RGBA, GL_UNSIGNED_BYTE, texData.dataBuffer[i].Buffer());
            break;
    }
    glTexParameteri(rs.bindTarget, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(rs.bindTarget, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(rs.bindTarget, GL_TEXTURE_WRAP_R, GL_REPEAT);

    if (samplerDesc.isCompareSampler)
    {
        glTexParameteri(rs.bindTarget, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
        glTexParameteri(rs.bindTarget, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glTexParameterf(rs.bindTarget, GL_TEXTURE_MAX_ANISOTROPY_EXT, 8.0f);
    }
    else
    {
        glTexParameteri(rs.bindTarget, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(rs.bindTarget, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glTexParameteri(rs.bindTarget, GL_TEXTURE_COMPARE_MODE, GL_COMPARE_REF_TO_TEXTURE);
        glTexParameteri(rs.bindTarget, GL_TEXTURE_COMPARE_FUNC, GL_LEQUAL);
    }
}

void GLRenderer::createInputSampler(BindingEntry& rs, InputSamplerDesc samplerDesc)
{
    glCreateSamplers(1, &rs.handle);
    glSamplerParameteri(rs.handle, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glSamplerParameteri(rs.handle, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glSamplerParameteri(rs.handle, GL_TEXTURE_WRAP_R, GL_REPEAT);

    if (samplerDesc.isCompareSampler)
    {
        glSamplerParameteri(rs.handle, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
        glSamplerParameteri(rs.handle, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glSamplerParameteri(rs.handle, GL_TEXTURE_MAX_ANISOTROPY_EXT, 8);
    }
    else
    {
        glSamplerParameteri(rs.handle, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glSamplerParameteri(rs.handle, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glSamplerParameteri(rs.handle, GL_TEXTURE_COMPARE_MODE, GL_COMPARE_REF_TO_TEXTURE);
        glSamplerParameteri(rs.handle, GL_TEXTURE_COMPARE_FUNC, GL_LEQUAL);
    }
}


// !!!!!!!!!!!!!!!!!!!!!!!!!!!! Renderer interface !!!!!!!!!!!!!!!!!!!!!!!!!!

SlangResult GLRenderer::initialize(void* inWindowHandle)
{
    auto windowHandle = (HWND)inWindowHandle;

    m_hdc = ::GetDC(windowHandle);

    PIXELFORMATDESCRIPTOR pixelFormatDesc = { sizeof(PIXELFORMATDESCRIPTOR) };
    pixelFormatDesc.nVersion = 1;
    pixelFormatDesc.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;
    pixelFormatDesc.iPixelType = PFD_TYPE_RGBA;
    pixelFormatDesc.cColorBits = 32;
    pixelFormatDesc.cDepthBits = 24;
    pixelFormatDesc.cStencilBits = 8;
    pixelFormatDesc.iLayerType = PFD_MAIN_PLANE;

    int pixelFormatIndex = ChoosePixelFormat(m_hdc, &pixelFormatDesc);
    SetPixelFormat(m_hdc, pixelFormatIndex, &pixelFormatDesc);

    m_glContext = wglCreateContext(m_hdc);
    wglMakeCurrent(m_hdc, m_glContext);

    auto renderer = glGetString(GL_RENDERER);
    auto extensions = glGetString(GL_EXTENSIONS);

    // Load each of our extension functions by name

#define LOAD_GL_EXTENSION_FUNC(NAME, TYPE) NAME = (TYPE) wglGetProcAddress(#NAME);
    MAP_GL_EXTENSION_FUNCS(LOAD_GL_EXTENSION_FUNC)
#undef LOAD_GL_EXTENSION_FUNC

    glDisable(GL_DEPTH_TEST);
    glDisable(GL_CULL_FACE);

    glViewport(0, 0, gWindowWidth, gWindowHeight);

    if (glDebugMessageCallback)
    {
        glEnable(GL_DEBUG_OUTPUT);
        glDebugMessageCallback(staticDebugCallback, this);
    }

    return SLANG_OK;
}

void GLRenderer::setClearColor(const float color[4])
{
    glClearColor(color[0], color[1], color[2], color[3]);
}

void GLRenderer::clearFrame()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
}

void GLRenderer::presentFrame()
{
    glFlush();
    ::SwapBuffers(m_hdc);
}

SlangResult GLRenderer::captureScreenShot(const char* outputPath)
{
    int width = gWindowWidth;
    int height = gWindowHeight;

    int components = 4;
    int rowStride = width*components;

    GLubyte* buffer = (GLubyte*)::malloc(components * width * height);

    glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, buffer);

    // OpenGL's "upside down" convention bites us here, so we need
    // to flip the data in the buffer by swapping rows
    int halfHeight = height / 2;
    for (int hh = 0; hh < halfHeight; ++hh)
    {
        // Get a pointer to the row data, and a pointer
        // to the row on the "other end" of the image
        GLubyte* rowA = buffer + rowStride*hh;
        GLubyte* rowB = buffer + rowStride*(height - (hh + 1));

        for (int ii = 0; ii < rowStride; ++ii)
        {
            auto a = rowA[ii];
            auto b = rowB[ii];

            rowA[ii] = b;
            rowB[ii] = a;
        }
    }

    //
    int stbResult = stbi_write_png(outputPath, width, height, components, buffer, rowStride);

    ::free(buffer);

    if (!stbResult)
    {
        assert(!"unexpected");
        return SLANG_FAIL;
    }

    return SLANG_OK;
}

ShaderCompiler* GLRenderer::getShaderCompiler()
{
    return this;
}

Buffer* GLRenderer::createBuffer(const BufferDesc& desc)
{
    // TODO: should derive target from desc...
    GLenum target = GL_UNIFORM_BUFFER;

    // TODO: should derive from desc...
    GLenum usage = GL_DYNAMIC_DRAW;

    GLuint bufferID = 0;
    glGenBuffers(1, &bufferID);
    glBindBuffer(target, bufferID);

    glBufferData(target, desc.size, desc.initData, usage);

	return new BufferImpl(this, bufferID);
}

InputLayout* GLRenderer::createInputLayout(const InputElementDesc* inputElements, UInt inputElementCount)
{
    InputLayoutImpl* inputLayout = new InputLayoutImpl;

    inputLayout->m_attributeCount = inputElementCount;
    for (UInt ii = 0; ii < inputElementCount; ++ii)
    {
        auto& inputAttr = inputElements[ii];
        auto& glAttr = inputLayout->m_attributes[ii];

        glAttr.streamIndex = 0;
        glAttr.format = getVertexAttributeFormat(inputAttr.format);
        glAttr.offset = (GLsizei)inputAttr.offset;
    }

    return (InputLayout*)inputLayout;
}

void* GLRenderer::map(Buffer* bufferIn, MapFlavor flavor)
{
	BufferImpl* buffer = static_cast<BufferImpl*>(bufferIn);

    GLenum target = GL_UNIFORM_BUFFER;

    GLuint access = 0;
    switch (flavor)
    {
        case MapFlavor::WriteDiscard:
        case MapFlavor::HostWrite:
            access = GL_WRITE_ONLY;
            break;
        case MapFlavor::HostRead:
            access = GL_READ_ONLY;
            break;
    }

    auto bufferID = buffer ? buffer->m_id : 0;
    glBindBuffer(target, bufferID);

    return glMapBuffer(target, access);
}

void GLRenderer::unmap(Buffer* bufferIn)
{
	BufferImpl* buffer = static_cast<BufferImpl*>(bufferIn);
    GLenum target = GL_UNIFORM_BUFFER;
    auto bufferID = buffer ? buffer->m_id : 0;
    glUnmapBuffer(target);
}

void GLRenderer::setInputLayout(InputLayout* inputLayout)
{
    m_boundInputLayout = static_cast<InputLayoutImpl*>(inputLayout);
}

void GLRenderer::setPrimitiveTopology(PrimitiveTopology topology)
{
    GLenum glTopology = 0;
    switch (topology)
    {
#define CASE(NAME, VALUE) case PrimitiveTopology::NAME: glTopology = VALUE; break

        CASE(TriangleList, GL_TRIANGLES);

#undef CASE
    }
    m_boundPrimitiveTopology = glTopology;
}

void GLRenderer::setVertexBuffers(UInt startSlot, UInt slotCount, Buffer*const* buffers, const UInt* strides, const UInt* offsets)
{
    for (UInt ii = 0; ii < slotCount; ++ii)
    {
        UInt slot = startSlot + ii;

        BufferImpl* buffer = static_cast<BufferImpl*>(buffers[ii]);
        GLuint bufferID = buffer ? buffer->m_id : 0;
		
        m_boundVertexStreamBuffers[slot] = bufferID;
        m_boundVertexStreamStrides[slot] = strides[ii];
        m_boundVertexStreamOffsets[slot] = offsets[ii];
    }
}

void GLRenderer::setShaderProgram(ShaderProgram* programIn)
{
	ShaderProgramImpl* program = static_cast<ShaderProgramImpl*>(programIn);
	m_boundShaderProgram = program;
    GLuint programID = program ? program->m_id : 0;
	glUseProgram(programID);
}

void GLRenderer::setConstantBuffers(UInt startSlot, UInt slotCount, Buffer*const* buffers, const UInt* offsets) 
{
    bindBufferImpl(GL_UNIFORM_BUFFER, startSlot, slotCount, buffers, offsets);
}

void GLRenderer::draw(UInt vertexCount, UInt startVertex = 0) 
{
    flushStateForDraw();

    glDrawArrays(m_boundPrimitiveTopology, (GLint)startVertex, (GLsizei)vertexCount);
}

void GLRenderer::dispatchCompute(int x, int y, int z)
{
    glDispatchCompute(x, y, z);
}

BindingState* GLRenderer::createBindingState(const ShaderInputLayout& layout)
{
    BindingStateImpl* state = new BindingStateImpl(this);
    for (auto & entry : layout.entries)
    {
        BindingEntry rsEntry;
        rsEntry.isOutput = entry.isOutput;
        rsEntry.binding = entry.glslBinding;
        rsEntry.type = entry.type;
        switch (entry.type)
        {
            case ShaderInputType::Buffer:
                createInputBuffer(rsEntry, entry.bufferDesc, entry.bufferData);
                break;
            case ShaderInputType::Texture:
                createInputTexture(rsEntry, entry.textureDesc, InputSamplerDesc());
                break;
            case ShaderInputType::CombinedTextureSampler:
                createInputTexture(rsEntry, entry.textureDesc, entry.samplerDesc);
                break;
            case ShaderInputType::Sampler:
                createInputSampler(rsEntry, entry.samplerDesc);
                break;
        }
        state->m_entries.Add(rsEntry);
    }
    return state;
}

void GLRenderer::setBindingState(BindingState* stateIn)
{
    BindingStateImpl* state = static_cast<BindingStateImpl*>(stateIn);
    for (auto & entry : state->m_entries)
    {
        switch (entry.type)
        {
            case ShaderInputType::Buffer:
                glBindBufferBase(entry.bindTarget, entry.binding[0], entry.handle);
                break;
            case ShaderInputType::Sampler:
                for (auto b : entry.binding)
                    glBindSampler(b, entry.handle);
                break;
            case ShaderInputType::Texture:
            case ShaderInputType::CombinedTextureSampler:
                glActiveTexture(GL_TEXTURE0 + entry.binding[0]);
                glBindTexture(entry.bindTarget, entry.handle);
                break;
        }
    }
}

void GLRenderer::serializeOutput(BindingState* stateIn, const char* fileName)
{
    BindingStateImpl * state = (BindingStateImpl*)stateIn;
    FILE * f;
    fopen_s(&f, fileName, "wt");
    for (auto & entry : state->m_entries)
    {
        if (entry.isOutput)
        {
            glBindBuffer(entry.bindTarget, entry.handle);
            auto ptr = (unsigned int *)glMapBuffer(entry.bindTarget, GL_READ_ONLY);
            for (auto i = 0u; i < entry.bufferSize / sizeof(unsigned int); i++)
                fprintf(f, "%X\n", ptr[i]);
            glUnmapBuffer(entry.bindTarget);
        }
    }
    fclose(f);
}


// ShaderCompiler interface

ShaderProgram* GLRenderer::compileProgram(const ShaderCompileRequest& request) 
{
    auto programID = glCreateProgram();
    if (request.computeShader.name)
    {
        auto computeShaderID = loadShader(GL_COMPUTE_SHADER, request.computeShader.source.dataBegin);
        glAttachShader(programID, computeShaderID);
        glLinkProgram(programID);
        glDeleteShader(computeShaderID);
    }
    else
    {
        auto vertexShaderID = loadShader(GL_VERTEX_SHADER, request.vertexShader.source.dataBegin);
        auto fragmentShaderID = loadShader(GL_FRAGMENT_SHADER, request.fragmentShader.source.dataBegin);

        glAttachShader(programID, vertexShaderID);
        glAttachShader(programID, fragmentShaderID);


        glLinkProgram(programID);

        glDeleteShader(vertexShaderID);
        glDeleteShader(fragmentShaderID);
    }
    GLint success = GL_FALSE;
    glGetProgramiv(programID, GL_LINK_STATUS, &success);
    if (!success)
    {
        int maxSize = 0;
        glGetProgramiv(programID, GL_INFO_LOG_LENGTH, &maxSize);

        auto infoBuffer = (char*)::malloc(maxSize);

        int infoSize = 0;
        glGetProgramInfoLog(programID, maxSize, &infoSize, infoBuffer);
        if (infoSize > 0)
        {
            fprintf(stderr, "%s", infoBuffer);
            OutputDebugStringA(infoBuffer);
        }

        ::free(infoBuffer);

        glDeleteProgram(programID);
        return nullptr;
    }

    return new ShaderProgramImpl(this, programID);
}


} // renderer_test