//  SPDX-License-Identifier: MIT
//
//  EmulationStation Desktop Edition
//  Renderer_GL21.cpp
//
//  OpenGL / OpenGL ES renderer.
//

#include "Settings.h"
#include "Shader_GL21.h"
#include "renderers/Renderer.h"

#if defined(__APPLE__)
#include <chrono>
#endif

namespace Renderer
{
    static SDL_GLContext sdlContext = nullptr;
    static GLuint whiteTexture {0};
    static GLuint postProcTexture1 {0};
    static GLuint postProcTexture2 {0};

    inline GLenum convertBlendFactor(const Blend::Factor blendFactor)
    {
        // clang-format off
        switch (blendFactor) {
            case Blend::ZERO:                { return GL_ZERO;                } break;
            case Blend::ONE:                 { return GL_ONE;                 } break;
            case Blend::SRC_COLOR:           { return GL_SRC_COLOR;           } break;
            case Blend::ONE_MINUS_SRC_COLOR: { return GL_ONE_MINUS_SRC_COLOR; } break;
            case Blend::SRC_ALPHA:           { return GL_SRC_ALPHA;           } break;
            case Blend::ONE_MINUS_SRC_ALPHA: { return GL_ONE_MINUS_SRC_ALPHA; } break;
            case Blend::DST_COLOR:           { return GL_DST_COLOR;           } break;
            case Blend::ONE_MINUS_DST_COLOR: { return GL_ONE_MINUS_DST_COLOR; } break;
            case Blend::DST_ALPHA:           { return GL_DST_ALPHA;           } break;
            case Blend::ONE_MINUS_DST_ALPHA: { return GL_ONE_MINUS_DST_ALPHA; } break;
            default:                         { return GL_ZERO;                }
        }
        // clang-format on
    }

    inline GLenum convertTextureType(const Texture::Type type)
    {
        // clang-format off
        switch (type) {
            case Texture::RGBA:  { return GL_RGBA;            } break;
#if defined(USE_OPENGLES)
            case Texture::BGRA:  { return GL_BGRA_EXT;        } break;
#else
            case Texture::BGRA:  { return GL_BGRA;            } break;
#endif
            case Texture::RED:   { return GL_RED;             } break;
            default:             { return GL_ZERO;            }
        }
        // clang-format on
    }

    void setupWindow()
    {

#if defined(USE_OPENGLES)
        SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_ES);
        SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
        SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
#else
        SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
        SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
        SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3);
#endif

        SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
        SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
        SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);
        SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
        SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
    }

    bool createContext()
    {
        sdlContext = SDL_GL_CreateContext(getSDLWindow());

        if (!sdlContext) {
            LOG(LogError) << "Error creating OpenGL context. " << SDL_GetError();
            return false;
        }

#if defined(_WIN64)
        glewInit();
#endif

        SDL_GL_MakeCurrent(getSDLWindow(), sdlContext);

        std::string vendor =
            glGetString(GL_VENDOR) ? reinterpret_cast<const char*>(glGetString(GL_VENDOR)) : "";
        std::string renderer =
            glGetString(GL_RENDERER) ? reinterpret_cast<const char*>(glGetString(GL_RENDERER)) : "";
        std::string version =
            glGetString(GL_VERSION) ? reinterpret_cast<const char*>(glGetString(GL_VERSION)) : "";
        std::string extensions = glGetString(GL_EXTENSIONS) ?
                                     reinterpret_cast<const char*>(glGetString(GL_EXTENSIONS)) :
                                     "";

        LOG(LogInfo) << "GL vendor: " << vendor;
        LOG(LogInfo) << "GL renderer: " << renderer;
        LOG(LogInfo) << "GL version: " << version;
#if defined(_WIN64)
        LOG(LogInfo) << "EmulationStation renderer: OpenGL 3.3 with GLEW";
#else
#if defined(USE_OPENGLES)
        LOG(LogInfo) << "EmulationStation renderer: OpenGL ES 3.0";
#else
        LOG(LogInfo) << "EmulationStation renderer: OpenGL 3.3";
#endif
#endif

#if !defined(USE_OPENGLES)
        // TODO: Fix the issue that causes the first glClearColor function call to fail.
        GL_CHECK_ERROR(glClearColor(0.0f, 0.0f, 0.0f, 1.0f));
#endif

        GL_CHECK_ERROR(glClearColor(0.0f, 0.0f, 0.0f, 1.0f));
        GL_CHECK_ERROR(glActiveTexture(GL_TEXTURE0));
        GL_CHECK_ERROR(glEnable(GL_BLEND));
        GL_CHECK_ERROR(glPixelStorei(GL_PACK_ALIGNMENT, 1));
        GL_CHECK_ERROR(glPixelStorei(GL_UNPACK_ALIGNMENT, 1));

        // These are used for the shader post processing.
        GL_CHECK_ERROR(glGenFramebuffers(1, &shaderFBO1));
        GL_CHECK_ERROR(glGenFramebuffers(1, &shaderFBO2));

        GL_CHECK_ERROR(glGenBuffers(1, &vertexBuffer1));
        GL_CHECK_ERROR(glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer1));
        GL_CHECK_ERROR(glGenVertexArrays(1, &vertexBuffer2));
        GL_CHECK_ERROR(glBindVertexArray(vertexBuffer2));

        uint8_t data[4] = {255, 255, 255, 255};
        whiteTexture = createTexture(Texture::RGBA, false, false, true, 1, 1, data);

        postProcTexture1 = createTexture(Texture::RGBA, false, false, false,
                                         static_cast<unsigned int>(getScreenWidth()),
                                         static_cast<unsigned int>(getScreenHeight()), nullptr);

        postProcTexture2 = createTexture(Texture::RGBA, false, false, false,
                                         static_cast<unsigned int>(getScreenWidth()),
                                         static_cast<unsigned int>(getScreenHeight()), nullptr);

        // Attach textures to the shader framebuffers.
        GL_CHECK_ERROR(glBindFramebuffer(GL_DRAW_FRAMEBUFFER, shaderFBO1));
        GL_CHECK_ERROR(glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
                                              postProcTexture1, 0));

        GL_CHECK_ERROR(glBindFramebuffer(GL_DRAW_FRAMEBUFFER, shaderFBO2));
        GL_CHECK_ERROR(glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
                                              postProcTexture2, 0));

        GL_CHECK_ERROR(glBindFramebuffer(GL_FRAMEBUFFER, 0));

        return true;
    }

    void destroyContext()
    {
        GL_CHECK_ERROR(glDeleteFramebuffers(1, &shaderFBO1));
        GL_CHECK_ERROR(glDeleteFramebuffers(1, &shaderFBO2));
        destroyTexture(postProcTexture1);
        destroyTexture(postProcTexture2);
        destroyTexture(whiteTexture);
        SDL_GL_DeleteContext(sdlContext);
        sdlContext = nullptr;
    }

    unsigned int createTexture(const Texture::Type type,
                               const bool linearMinify,
                               const bool linearMagnify,
                               const bool repeat,
                               const unsigned int width,
                               const unsigned int height,
                               void* data)
    {
        const GLenum textureType = convertTextureType(type);
        unsigned int texture;

        GL_CHECK_ERROR(glGenTextures(1, &texture));
        GL_CHECK_ERROR(glBindTexture(GL_TEXTURE_2D, texture));

        GL_CHECK_ERROR(glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S,
                                       repeat ? static_cast<GLfloat>(GL_REPEAT) :
                                                static_cast<GLfloat>(GL_CLAMP_TO_EDGE)));
        GL_CHECK_ERROR(glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T,
                                       repeat ? static_cast<GLfloat>(GL_REPEAT) :
                                                static_cast<GLfloat>(GL_CLAMP_TO_EDGE)));
        GL_CHECK_ERROR(glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
                                       linearMinify ? static_cast<GLfloat>(GL_LINEAR) :
                                                      static_cast<GLfloat>(GL_NEAREST)));
        GL_CHECK_ERROR(glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,
                                       linearMagnify ? static_cast<GLfloat>(GL_LINEAR) :
                                                       static_cast<GLfloat>(GL_NEAREST)));

        GL_CHECK_ERROR(glTexImage2D(GL_TEXTURE_2D, 0, textureType, width, height, 0, textureType,
                                    GL_UNSIGNED_BYTE, data));
        return texture;
    }

    void destroyTexture(const unsigned int texture)
    {
        GL_CHECK_ERROR(glDeleteTextures(1, &texture));
    }

    void updateTexture(const unsigned int texture,
                       const Texture::Type type,
                       const unsigned int x,
                       const unsigned int y,
                       const unsigned int width,
                       const unsigned int height,
                       void* data)
    {
        const GLenum textureType = convertTextureType(type);

        GL_CHECK_ERROR(glBindTexture(GL_TEXTURE_2D, texture));
        GL_CHECK_ERROR(glTexSubImage2D(GL_TEXTURE_2D, 0, x, y, width, height, textureType,
                                       GL_UNSIGNED_BYTE, data));

        GL_CHECK_ERROR(glBindTexture(GL_TEXTURE_2D, whiteTexture));
    }

    void bindTexture(const unsigned int texture)
    {
        if (texture == 0)
            GL_CHECK_ERROR(glBindTexture(GL_TEXTURE_2D, whiteTexture));
        else
            GL_CHECK_ERROR(glBindTexture(GL_TEXTURE_2D, texture));
    }

    void drawTriangleStrips(const Vertex* vertices,
                            const unsigned int numVertices,
                            const Blend::Factor srcBlendFactor,
                            const Blend::Factor dstBlendFactor)
    {
        const float width {vertices[3].position[0]};
        const float height {vertices[3].position[1]};

        GL_CHECK_ERROR(
            glBlendFunc(convertBlendFactor(srcBlendFactor), convertBlendFactor(dstBlendFactor)));

        if (vertices->shaders == 0 || vertices->shaders & SHADER_CORE) {
            Shader* shader {getShaderProgram(SHADER_CORE)};
            if (shader) {
                shader->activateShaders();
                shader->setModelViewProjectionMatrix(mTrans);
                shader->setAttribPointers();
                GL_CHECK_ERROR(glBufferData(GL_ARRAY_BUFFER, sizeof(Vertex) * numVertices, vertices,
                                            GL_DYNAMIC_DRAW));
                shader->setOpacity(vertices->opacity);
                shader->setSaturation(vertices->saturation);
                shader->setDimming(vertices->dimming);
                shader->setBGRAToRGBA(vertices->convertBGRAToRGBA);
                shader->setFont(vertices->font);
                shader->setPostProcessing(vertices->postProcessing);
                GL_CHECK_ERROR(glDrawArrays(GL_TRIANGLE_STRIP, 0, numVertices));
                shader->deactivateShaders();
            }
        }
        else if (vertices->shaders & SHADER_BLUR_HORIZONTAL) {
            Shader* shader {getShaderProgram(SHADER_BLUR_HORIZONTAL)};
            if (shader) {
                shader->activateShaders();
                shader->setModelViewProjectionMatrix(mTrans);
                shader->setAttribPointers();
                GL_CHECK_ERROR(glBufferData(GL_ARRAY_BUFFER, sizeof(Vertex) * numVertices, vertices,
                                            GL_DYNAMIC_DRAW));
                shader->setTextureSize({width, height});
                GL_CHECK_ERROR(glDrawArrays(GL_TRIANGLE_STRIP, 0, numVertices));
                shader->deactivateShaders();
            }
            return;
        }
        else if (vertices->shaders & SHADER_BLUR_VERTICAL) {
            Shader* shader {getShaderProgram(SHADER_BLUR_VERTICAL)};
            if (shader) {
                shader->activateShaders();
                shader->setModelViewProjectionMatrix(mTrans);
                shader->setAttribPointers();
                GL_CHECK_ERROR(glBufferData(GL_ARRAY_BUFFER, sizeof(Vertex) * numVertices, vertices,
                                            GL_DYNAMIC_DRAW));
                shader->setTextureSize({width, height});
                GL_CHECK_ERROR(glDrawArrays(GL_TRIANGLE_STRIP, 0, numVertices));
                shader->deactivateShaders();
            }
            return;
        }
        else if (vertices->shaders & SHADER_SCANLINES) {
            Shader* shader {getShaderProgram(SHADER_SCANLINES)};
            float shaderWidth {width * 1.2f};
            // Scale the scanlines relative to screen resolution.
            float screenHeightModifier {getScreenHeightModifier()};
            float relativeHeight {height / getScreenHeight()};
            float shaderHeight {0.0f};
            if (relativeHeight == 1.0f) {
                // Full screen.
                float modifier {1.30f - (0.1f * screenHeightModifier)};
                shaderHeight = height * modifier;
            }
            else {
                // Portion of screen, e.g. gamelist view.
                // Average the relative width and height to avoid applying exaggerated
                // scanlines to videos with non-standard aspect ratios.
                float relativeWidth {width / getScreenWidth()};
                float relativeAdjustment {(relativeWidth + relativeHeight) / 2.0f};
                float modifier {1.41f + relativeAdjustment / 7.0f - (0.14f * screenHeightModifier)};
                shaderHeight = height * modifier;
            }
            if (shader) {
                shader->activateShaders();
                shader->setModelViewProjectionMatrix(mTrans);
                shader->setAttribPointers();
                GL_CHECK_ERROR(glBufferData(GL_ARRAY_BUFFER, sizeof(Vertex) * numVertices, vertices,
                                            GL_DYNAMIC_DRAW));
                shader->setOpacity(vertices->opacity);
                shader->setTextureSize({shaderWidth, shaderHeight});
                GL_CHECK_ERROR(glDrawArrays(GL_TRIANGLE_STRIP, 0, numVertices));
                shader->deactivateShaders();
            }
        }
    }

    void setMatrix(const glm::mat4& matrix)
    {
        mTrans = matrix;
        mTrans[3] = glm::round(mTrans[3]);
        mTrans = getProjectionMatrix() * mTrans;
    }

    void setScissor(const Rect& scissor)
    {
        if ((scissor.x == 0) && (scissor.y == 0) && (scissor.w == 0) && (scissor.h == 0)) {
            GL_CHECK_ERROR(glDisable(GL_SCISSOR_TEST));
        }
        else {
            // glScissor starts at the bottom left of the window.
            GL_CHECK_ERROR(glScissor(scissor.x,
                                     static_cast<GLint>(getWindowHeight()) - scissor.y - scissor.h,
                                     scissor.w, scissor.h));
            GL_CHECK_ERROR(glEnable(GL_SCISSOR_TEST));
        }
    }

    void setSwapInterval()
    {
        if (Settings::getInstance()->getBool("VSync")) {
            // Adaptive VSync seems to be nonfunctional or having issues on some hardware
            // and drivers, so only attempt to apply regular VSync.
            if (SDL_GL_SetSwapInterval(1) == 0) {
                LOG(LogInfo) << "Enabling VSync...";
            }
            else {
                LOG(LogWarning) << "Could not enable VSync: " << SDL_GetError();
            }
        }
        else {
            SDL_GL_SetSwapInterval(0);
            LOG(LogInfo) << "Disabling VSync...";
        }
    }

    void swapBuffers()
    {
#if defined(__APPLE__)
        // On macOS when running in the background, the OpenGL driver apparently does not swap
        // the frames which leads to a very fast swap time. This makes ES-DE use a lot of CPU
        // resources which slows down the games significantly on slower machines. By introducing
        // a delay if the swap time is very low we reduce CPU usage while still keeping the
        // application functioning normally.
        const auto beforeSwap = std::chrono::system_clock::now();
        SDL_GL_SwapWindow(getSDLWindow());

        if (std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::system_clock::now() -
                                                                  beforeSwap)
                .count() < 3.0)
            SDL_Delay(10);
#else
        SDL_GL_SwapWindow(getSDLWindow());
#endif
        GL_CHECK_ERROR(glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT));
    }

    void shaderPostprocessing(unsigned int shaders,
                              const Renderer::postProcessingParams& parameters,
                              unsigned char* textureRGBA)
    {
        Vertex vertices[4];
        std::vector<unsigned int> shaderList;
        float widthf {getScreenWidth()};
        float heightf {getScreenHeight()};
        GLuint width {static_cast<GLuint>(widthf)};
        GLuint height {static_cast<GLuint>(heightf)};

        // Set vertex positions and texture coordinates to full screen as all
        // post-processing is applied to the complete screen area.
        // clang-format off
        vertices[0] = {{0.0f,   0.0f   }, {0.0f, 1.0f}, 0xFFFFFFFF};
        vertices[1] = {{0.0f,   heightf}, {0.0f, 0.0f}, 0xFFFFFFFF};
        vertices[2] = {{widthf, 0.0f   }, {1.0f, 1.0f}, 0xFFFFFFFF};
        vertices[3] = {{widthf, heightf}, {1.0f, 0.0f}, 0xFFFFFFFF};
        // clang-format on

        vertices->opacity = parameters.opacity;
        vertices->saturation = parameters.saturation;
        vertices->dimming = parameters.dimming;
        vertices->postProcessing = true;

        if (shaders & Renderer::SHADER_CORE)
            shaderList.push_back(Renderer::SHADER_CORE);
        if (shaders & Renderer::SHADER_BLUR_HORIZONTAL)
            shaderList.push_back(Renderer::SHADER_BLUR_HORIZONTAL);
        if (shaders & Renderer::SHADER_BLUR_VERTICAL)
            shaderList.push_back(Renderer::SHADER_BLUR_VERTICAL);
        if (shaders & Renderer::SHADER_SCANLINES)
            shaderList.push_back(Renderer::SHADER_SCANLINES);

        setMatrix(getIdentity());
        bindTexture(postProcTexture1);

        GL_CHECK_ERROR(glBindFramebuffer(GL_DRAW_FRAMEBUFFER, shaderFBO1));

        // Blit the screen contents to postProcTexture.
        GL_CHECK_ERROR(glBlitFramebuffer(0, 0, width, height, 0, 0, width, height,
                                         GL_COLOR_BUFFER_BIT, GL_NEAREST));

        GL_CHECK_ERROR(glBindFramebuffer(GL_DRAW_FRAMEBUFFER, shaderFBO2));

        bool firstFBO {true};
        int drawCalls {0};

        for (size_t i = 0; i < shaderList.size(); ++i) {
            vertices->shaders = shaderList[i];
            int shaderPasses = 1;
            // For the blur shaders there is an optional variable to set the number of passes
            // to execute, which proportionally affects the blur amount.
            if (shaderList[i] == Renderer::SHADER_BLUR_HORIZONTAL ||
                shaderList[i] == Renderer::SHADER_BLUR_VERTICAL) {
                shaderPasses = parameters.blurPasses;
            }

            for (int p = 0; p < shaderPasses; ++p) {
                if (textureRGBA == nullptr && i == shaderList.size() - 1 && p == shaderPasses - 1) {
                    // If the screen is rotated and we're at an even number of drawcalls, then
                    // set the projection to a non-rotated state before making the last drawcall
                    // as the image would otherwise get rendered upside down.
                    if (getScreenRotated() && drawCalls % 2 == 0) {
                        mTrans = getIdentity();
                        mTrans[3] = glm::round(mTrans[3]);
                        mTrans = getProjectionMatrixNormal() * mTrans;
                    }
                    // If it's the last shader pass, then render directly to the default framebuffer
                    // to avoid having to make an expensive glBlitFramebuffer() call.
                    GL_CHECK_ERROR(glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0));
                    drawTriangleStrips(vertices, 4, Blend::SRC_ALPHA, Blend::ONE_MINUS_SRC_ALPHA);
                    break;
                }
                // Apply/render the shaders.
                drawTriangleStrips(vertices, 4, Blend::SRC_ALPHA, Blend::ONE_MINUS_SRC_ALPHA);
                ++drawCalls;
                if (firstFBO) {
                    bindTexture(postProcTexture2);
                    GL_CHECK_ERROR(glBindFramebuffer(GL_READ_FRAMEBUFFER, shaderFBO2));
                    GL_CHECK_ERROR(glBindFramebuffer(GL_DRAW_FRAMEBUFFER, shaderFBO1));
                    GL_CHECK_ERROR(glClear(GL_COLOR_BUFFER_BIT));
                    firstFBO = false;
                }
                else {
                    bindTexture(postProcTexture1);
                    GL_CHECK_ERROR(glBindFramebuffer(GL_READ_FRAMEBUFFER, shaderFBO1));
                    GL_CHECK_ERROR(glBindFramebuffer(GL_DRAW_FRAMEBUFFER, shaderFBO2));
                    GL_CHECK_ERROR(glClear(GL_COLOR_BUFFER_BIT));
                    firstFBO = true;
                }
            }
        }

        // If textureRGBA has an address, it means that the output should go to this
        // texture rather than to the screen. The glReadPixels() function is slow, but
        // since this will typically only run every now and then to create a cached
        // screen texture, it doesn't really matter.
        if (textureRGBA) {
            if (firstFBO)
                GL_CHECK_ERROR(glBindFramebuffer(GL_READ_FRAMEBUFFER, shaderFBO1));
            else
                GL_CHECK_ERROR(glBindFramebuffer(GL_READ_FRAMEBUFFER, shaderFBO2));

            GL_CHECK_ERROR(
                glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, textureRGBA));
            GL_CHECK_ERROR(glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0));
        }

        if (getScreenRotated())
            setMatrix(getIdentity());

        GL_CHECK_ERROR(glBindFramebuffer(GL_READ_FRAMEBUFFER, 0));
    }

} // namespace Renderer