// Copyright 2014 Citra Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.

#include <algorithm>
#include <cstddef>
#include <cstdlib>
#include <memory>
#include <glad/glad.h>
#include "common/assert.h"
#include "common/logging/log.h"
#include "common/telemetry.h"
#include "core/core.h"
#include "core/core_timing.h"
#include "core/frontend/emu_window.h"
#include "core/frontend/scope_acquire_window_context.h"
#include "core/memory.h"
#include "core/perf_stats.h"
#include "core/settings.h"
#include "core/telemetry_session.h"
#include "video_core/morton.h"
#include "video_core/renderer_opengl/gl_rasterizer.h"
#include "video_core/renderer_opengl/renderer_opengl.h"

namespace OpenGL {

static const char vertex_shader[] = R"(
#version 150 core

in vec2 vert_position;
in vec2 vert_tex_coord;
out vec2 frag_tex_coord;

// This is a truncated 3x3 matrix for 2D transformations:
// The upper-left 2x2 submatrix performs scaling/rotation/mirroring.
// The third column performs translation.
// The third row could be used for projection, which we don't need in 2D. It hence is assumed to
// implicitly be [0, 0, 1]
uniform mat3x2 modelview_matrix;

void main() {
    // Multiply input position by the rotscale part of the matrix and then manually translate by
    // the last column. This is equivalent to using a full 3x3 matrix and expanding the vector
    // to `vec3(vert_position.xy, 1.0)`
    gl_Position = vec4(mat2(modelview_matrix) * vert_position + modelview_matrix[2], 0.0, 1.0);
    frag_tex_coord = vert_tex_coord;
}
)";

static const char fragment_shader[] = R"(
#version 150 core

in vec2 frag_tex_coord;
out vec4 color;

uniform sampler2D color_texture;

void main() {
    // Swap RGBA -> ABGR so we don't have to do this on the CPU. This needs to change if we have to
    // support more framebuffer pixel formats.
    color = texture(color_texture, frag_tex_coord);
}
)";

/**
 * Vertex structure that the drawn screen rectangles are composed of.
 */
struct ScreenRectVertex {
    ScreenRectVertex(GLfloat x, GLfloat y, GLfloat u, GLfloat v) {
        position[0] = x;
        position[1] = y;
        tex_coord[0] = u;
        tex_coord[1] = v;
    }

    GLfloat position[2];
    GLfloat tex_coord[2];
};

/**
 * Defines a 1:1 pixel ortographic projection matrix with (0,0) on the top-left
 * corner and (width, height) on the lower-bottom.
 *
 * The projection part of the matrix is trivial, hence these operations are represented
 * by a 3x2 matrix.
 */
static std::array<GLfloat, 3 * 2> MakeOrthographicMatrix(const float width, const float height) {
    std::array<GLfloat, 3 * 2> matrix; // Laid out in column-major order

    // clang-format off
    matrix[0] = 2.f / width; matrix[2] = 0.f;           matrix[4] = -1.f;
    matrix[1] = 0.f;         matrix[3] = -2.f / height; matrix[5] = 1.f;
    // Last matrix row is implicitly assumed to be [0, 0, 1].
    // clang-format on

    return matrix;
}

RendererOpenGL::RendererOpenGL(Core::Frontend::EmuWindow& emu_window, Core::System& system)
    : VideoCore::RendererBase{emu_window}, emu_window{emu_window}, system{system} {}

RendererOpenGL::~RendererOpenGL() = default;

void RendererOpenGL::SwapBuffers(const Tegra::FramebufferConfig* framebuffer) {
    system.GetPerfStats().EndSystemFrame();

    // Maintain the rasterizer's state as a priority
    OpenGLState prev_state = OpenGLState::GetCurState();
    state.AllDirty();
    state.Apply();

    if (framebuffer) {
        // If framebuffer is provided, reload it from memory to a texture
        if (screen_info.texture.width != static_cast<GLsizei>(framebuffer->width) ||
            screen_info.texture.height != static_cast<GLsizei>(framebuffer->height) ||
            screen_info.texture.pixel_format != framebuffer->pixel_format) {
            // Reallocate texture if the framebuffer size has changed.
            // This is expected to not happen very often and hence should not be a
            // performance problem.
            ConfigureFramebufferTexture(screen_info.texture, *framebuffer);
        }

        // Load the framebuffer from memory, draw it to the screen, and swap buffers
        LoadFBToScreenInfo(*framebuffer);

        if (renderer_settings.screenshot_requested)
            CaptureScreenshot();

        DrawScreen(render_window.GetFramebufferLayout());

        rasterizer->TickFrame();

        render_window.SwapBuffers();
    }

    render_window.PollEvents();

    system.FrameLimiter().DoFrameLimiting(system.CoreTiming().GetGlobalTimeUs());
    system.GetPerfStats().BeginSystemFrame();

    // Restore the rasterizer state
    prev_state.AllDirty();
    prev_state.Apply();
}

/**
 * Loads framebuffer from emulated memory into the active OpenGL texture.
 */
void RendererOpenGL::LoadFBToScreenInfo(const Tegra::FramebufferConfig& framebuffer) {
    // Framebuffer orientation handling
    framebuffer_transform_flags = framebuffer.transform_flags;
    framebuffer_crop_rect = framebuffer.crop_rect;

    const VAddr framebuffer_addr{framebuffer.address + framebuffer.offset};
    if (rasterizer->AccelerateDisplay(framebuffer, framebuffer_addr, framebuffer.stride)) {
        return;
    }

    // Reset the screen info's display texture to its own permanent texture
    screen_info.display_texture = screen_info.texture.resource.handle;

    const auto pixel_format{
        VideoCore::Surface::PixelFormatFromGPUPixelFormat(framebuffer.pixel_format)};
    const u32 bytes_per_pixel{VideoCore::Surface::GetBytesPerPixel(pixel_format)};
    const u64 size_in_bytes{framebuffer.stride * framebuffer.height * bytes_per_pixel};
    const auto host_ptr{Memory::GetPointer(framebuffer_addr)};
    rasterizer->FlushRegion(ToCacheAddr(host_ptr), size_in_bytes);

    // TODO(Rodrigo): Read this from HLE
    constexpr u32 block_height_log2 = 4;
    VideoCore::MortonSwizzle(VideoCore::MortonSwizzleMode::MortonToLinear, pixel_format,
                             framebuffer.stride, block_height_log2, framebuffer.height, 0, 1, 1,
                             gl_framebuffer_data.data(), host_ptr);

    glPixelStorei(GL_UNPACK_ROW_LENGTH, static_cast<GLint>(framebuffer.stride));

    // Update existing texture
    // TODO: Test what happens on hardware when you change the framebuffer dimensions so that
    //       they differ from the LCD resolution.
    // TODO: Applications could theoretically crash yuzu here by specifying too large
    //       framebuffer sizes. We should make sure that this cannot happen.
    glTextureSubImage2D(screen_info.texture.resource.handle, 0, 0, 0, framebuffer.width,
                        framebuffer.height, screen_info.texture.gl_format,
                        screen_info.texture.gl_type, gl_framebuffer_data.data());

    glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
}

/**
 * Fills active OpenGL texture with the given RGB color. Since the color is solid, the texture can
 * be 1x1 but will stretch across whatever it's rendered on.
 */
void RendererOpenGL::LoadColorToActiveGLTexture(u8 color_r, u8 color_g, u8 color_b, u8 color_a,
                                                const TextureInfo& texture) {
    const u8 framebuffer_data[4] = {color_a, color_b, color_g, color_r};
    glClearTexImage(texture.resource.handle, 0, GL_RGBA, GL_UNSIGNED_BYTE, framebuffer_data);
}

/**
 * Initializes the OpenGL state and creates persistent objects.
 */
void RendererOpenGL::InitOpenGLObjects() {
    glClearColor(Settings::values.bg_red, Settings::values.bg_green, Settings::values.bg_blue,
                 0.0f);

    // Link shaders and get variable locations
    shader.CreateFromSource(vertex_shader, nullptr, fragment_shader);
    state.draw.shader_program = shader.handle;
    state.AllDirty();
    state.Apply();
    uniform_modelview_matrix = glGetUniformLocation(shader.handle, "modelview_matrix");
    uniform_color_texture = glGetUniformLocation(shader.handle, "color_texture");
    attrib_position = glGetAttribLocation(shader.handle, "vert_position");
    attrib_tex_coord = glGetAttribLocation(shader.handle, "vert_tex_coord");

    // Generate VBO handle for drawing
    vertex_buffer.Create();

    // Generate VAO
    vertex_array.Create();
    state.draw.vertex_array = vertex_array.handle;

    // Attach vertex data to VAO
    glNamedBufferData(vertex_buffer.handle, sizeof(ScreenRectVertex) * 4, nullptr, GL_STREAM_DRAW);
    glVertexArrayAttribFormat(vertex_array.handle, attrib_position, 2, GL_FLOAT, GL_FALSE,
                              offsetof(ScreenRectVertex, position));
    glVertexArrayAttribFormat(vertex_array.handle, attrib_tex_coord, 2, GL_FLOAT, GL_FALSE,
                              offsetof(ScreenRectVertex, tex_coord));
    glVertexArrayAttribBinding(vertex_array.handle, attrib_position, 0);
    glVertexArrayAttribBinding(vertex_array.handle, attrib_tex_coord, 0);
    glEnableVertexArrayAttrib(vertex_array.handle, attrib_position);
    glEnableVertexArrayAttrib(vertex_array.handle, attrib_tex_coord);
    glVertexArrayVertexBuffer(vertex_array.handle, 0, vertex_buffer.handle, 0,
                              sizeof(ScreenRectVertex));

    // Allocate textures for the screen
    screen_info.texture.resource.Create(GL_TEXTURE_2D);

    const GLuint texture = screen_info.texture.resource.handle;
    glTextureStorage2D(texture, 1, GL_RGBA8, 1, 1);

    screen_info.display_texture = screen_info.texture.resource.handle;

    // Clear screen to black
    LoadColorToActiveGLTexture(0, 0, 0, 0, screen_info.texture);
}

void RendererOpenGL::AddTelemetryFields() {
    const char* const gl_version{reinterpret_cast<char const*>(glGetString(GL_VERSION))};
    const char* const gpu_vendor{reinterpret_cast<char const*>(glGetString(GL_VENDOR))};
    const char* const gpu_model{reinterpret_cast<char const*>(glGetString(GL_RENDERER))};

    LOG_INFO(Render_OpenGL, "GL_VERSION: {}", gl_version);
    LOG_INFO(Render_OpenGL, "GL_VENDOR: {}", gpu_vendor);
    LOG_INFO(Render_OpenGL, "GL_RENDERER: {}", gpu_model);

    auto& telemetry_session = system.TelemetrySession();
    telemetry_session.AddField(Telemetry::FieldType::UserSystem, "GPU_Vendor", gpu_vendor);
    telemetry_session.AddField(Telemetry::FieldType::UserSystem, "GPU_Model", gpu_model);
    telemetry_session.AddField(Telemetry::FieldType::UserSystem, "GPU_OpenGL_Version", gl_version);
}

void RendererOpenGL::CreateRasterizer() {
    if (rasterizer) {
        return;
    }
    rasterizer = std::make_unique<RasterizerOpenGL>(system, emu_window, screen_info);
}

void RendererOpenGL::ConfigureFramebufferTexture(TextureInfo& texture,
                                                 const Tegra::FramebufferConfig& framebuffer) {
    texture.width = framebuffer.width;
    texture.height = framebuffer.height;
    texture.pixel_format = framebuffer.pixel_format;

    const auto pixel_format{
        VideoCore::Surface::PixelFormatFromGPUPixelFormat(framebuffer.pixel_format)};
    const u32 bytes_per_pixel{VideoCore::Surface::GetBytesPerPixel(pixel_format)};
    gl_framebuffer_data.resize(texture.width * texture.height * bytes_per_pixel);

    GLint internal_format;
    switch (framebuffer.pixel_format) {
    case Tegra::FramebufferConfig::PixelFormat::ABGR8:
        internal_format = GL_RGBA8;
        texture.gl_format = GL_RGBA;
        texture.gl_type = GL_UNSIGNED_INT_8_8_8_8_REV;
        break;
    case Tegra::FramebufferConfig::PixelFormat::RGB565:
        internal_format = GL_RGB565;
        texture.gl_format = GL_RGB;
        texture.gl_type = GL_UNSIGNED_SHORT_5_6_5;
        break;
    default:
        internal_format = GL_RGBA8;
        texture.gl_format = GL_RGBA;
        texture.gl_type = GL_UNSIGNED_INT_8_8_8_8_REV;
        UNIMPLEMENTED_MSG("Unknown framebuffer pixel format: {}",
                          static_cast<u32>(framebuffer.pixel_format));
    }

    texture.resource.Release();
    texture.resource.Create(GL_TEXTURE_2D);
    glTextureStorage2D(texture.resource.handle, 1, internal_format, texture.width, texture.height);
}

void RendererOpenGL::DrawScreenTriangles(const ScreenInfo& screen_info, float x, float y, float w,
                                         float h) {
    const auto& texcoords = screen_info.display_texcoords;
    auto left = texcoords.left;
    auto right = texcoords.right;
    if (framebuffer_transform_flags != Tegra::FramebufferConfig::TransformFlags::Unset) {
        if (framebuffer_transform_flags == Tegra::FramebufferConfig::TransformFlags::FlipV) {
            // Flip the framebuffer vertically
            left = texcoords.right;
            right = texcoords.left;
        } else {
            // Other transformations are unsupported
            LOG_CRITICAL(Render_OpenGL, "Unsupported framebuffer_transform_flags={}",
                         static_cast<u32>(framebuffer_transform_flags));
            UNIMPLEMENTED();
        }
    }

    ASSERT_MSG(framebuffer_crop_rect.top == 0, "Unimplemented");
    ASSERT_MSG(framebuffer_crop_rect.left == 0, "Unimplemented");

    // Scale the output by the crop width/height. This is commonly used with 1280x720 rendering
    // (e.g. handheld mode) on a 1920x1080 framebuffer.
    f32 scale_u = 1.f, scale_v = 1.f;
    if (framebuffer_crop_rect.GetWidth() > 0) {
        scale_u = static_cast<f32>(framebuffer_crop_rect.GetWidth()) / screen_info.texture.width;
    }
    if (framebuffer_crop_rect.GetHeight() > 0) {
        scale_v = static_cast<f32>(framebuffer_crop_rect.GetHeight()) / screen_info.texture.height;
    }

    std::array<ScreenRectVertex, 4> vertices = {{
        ScreenRectVertex(x, y, texcoords.top * scale_u, left * scale_v),
        ScreenRectVertex(x + w, y, texcoords.bottom * scale_u, left * scale_v),
        ScreenRectVertex(x, y + h, texcoords.top * scale_u, right * scale_v),
        ScreenRectVertex(x + w, y + h, texcoords.bottom * scale_u, right * scale_v),
    }};

    state.textures[0] = screen_info.display_texture;
    state.framebuffer_srgb.enabled = screen_info.display_srgb;
    state.AllDirty();
    state.Apply();
    glNamedBufferSubData(vertex_buffer.handle, 0, sizeof(vertices), vertices.data());
    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
    // Restore default state
    state.framebuffer_srgb.enabled = false;
    state.textures[0] = 0;
    state.AllDirty();
    state.Apply();
}

/**
 * Draws the emulated screens to the emulator window.
 */
void RendererOpenGL::DrawScreen(const Layout::FramebufferLayout& layout) {
    if (renderer_settings.set_background_color) {
        // Update background color before drawing
        glClearColor(Settings::values.bg_red, Settings::values.bg_green, Settings::values.bg_blue,
                     0.0f);
    }

    const auto& screen = layout.screen;

    glViewport(0, 0, layout.width, layout.height);
    glClear(GL_COLOR_BUFFER_BIT);

    // Set projection matrix
    std::array<GLfloat, 3 * 2> ortho_matrix =
        MakeOrthographicMatrix((float)layout.width, (float)layout.height);
    glUniformMatrix3x2fv(uniform_modelview_matrix, 1, GL_FALSE, ortho_matrix.data());

    // Bind texture in Texture Unit 0
    glActiveTexture(GL_TEXTURE0);
    glUniform1i(uniform_color_texture, 0);

    DrawScreenTriangles(screen_info, (float)screen.left, (float)screen.top,
                        (float)screen.GetWidth(), (float)screen.GetHeight());

    m_current_frame++;
}

/// Updates the framerate
void RendererOpenGL::UpdateFramerate() {}

void RendererOpenGL::CaptureScreenshot() {
    // Draw the current frame to the screenshot framebuffer
    screenshot_framebuffer.Create();
    GLuint old_read_fb = state.draw.read_framebuffer;
    GLuint old_draw_fb = state.draw.draw_framebuffer;
    state.draw.read_framebuffer = state.draw.draw_framebuffer = screenshot_framebuffer.handle;
    state.AllDirty();
    state.Apply();

    Layout::FramebufferLayout layout{renderer_settings.screenshot_framebuffer_layout};

    GLuint renderbuffer;
    glGenRenderbuffers(1, &renderbuffer);
    glBindRenderbuffer(GL_RENDERBUFFER, renderbuffer);
    glRenderbufferStorage(GL_RENDERBUFFER, screen_info.display_srgb ? GL_SRGB8 : GL_RGB8,
                          layout.width, layout.height);
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, renderbuffer);

    DrawScreen(layout);

    glReadPixels(0, 0, layout.width, layout.height, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV,
                 renderer_settings.screenshot_bits);

    screenshot_framebuffer.Release();
    state.draw.read_framebuffer = old_read_fb;
    state.draw.draw_framebuffer = old_draw_fb;
    state.AllDirty();
    state.Apply();
    glDeleteRenderbuffers(1, &renderbuffer);

    renderer_settings.screenshot_complete_callback();
    renderer_settings.screenshot_requested = false;
}

static const char* GetSource(GLenum source) {
#define RET(s)                                                                                     \
    case GL_DEBUG_SOURCE_##s:                                                                      \
        return #s
    switch (source) {
        RET(API);
        RET(WINDOW_SYSTEM);
        RET(SHADER_COMPILER);
        RET(THIRD_PARTY);
        RET(APPLICATION);
        RET(OTHER);
    default:
        UNREACHABLE();
        return "Unknown source";
    }
#undef RET
}

static const char* GetType(GLenum type) {
#define RET(t)                                                                                     \
    case GL_DEBUG_TYPE_##t:                                                                        \
        return #t
    switch (type) {
        RET(ERROR);
        RET(DEPRECATED_BEHAVIOR);
        RET(UNDEFINED_BEHAVIOR);
        RET(PORTABILITY);
        RET(PERFORMANCE);
        RET(OTHER);
        RET(MARKER);
    default:
        UNREACHABLE();
        return "Unknown type";
    }
#undef RET
}

static void APIENTRY DebugHandler(GLenum source, GLenum type, GLuint id, GLenum severity,
                                  GLsizei length, const GLchar* message, const void* user_param) {
    const char format[] = "{} {} {}: {}";
    const char* const str_source = GetSource(source);
    const char* const str_type = GetType(type);

    switch (severity) {
    case GL_DEBUG_SEVERITY_HIGH:
        LOG_CRITICAL(Render_OpenGL, format, str_source, str_type, id, message);
        break;
    case GL_DEBUG_SEVERITY_MEDIUM:
        LOG_WARNING(Render_OpenGL, format, str_source, str_type, id, message);
        break;
    case GL_DEBUG_SEVERITY_NOTIFICATION:
    case GL_DEBUG_SEVERITY_LOW:
        LOG_DEBUG(Render_OpenGL, format, str_source, str_type, id, message);
        break;
    }
}

bool RendererOpenGL::Init() {
    Core::Frontend::ScopeAcquireWindowContext acquire_context{render_window};

    if (GLAD_GL_KHR_debug) {
        glEnable(GL_DEBUG_OUTPUT);
        glDebugMessageCallback(DebugHandler, nullptr);
    }

    AddTelemetryFields();

    if (!GLAD_GL_VERSION_4_3) {
        return false;
    }

    InitOpenGLObjects();
    CreateRasterizer();

    return true;
}

/// Shutdown the renderer
void RendererOpenGL::ShutDown() {}

} // namespace OpenGL
