#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <imgui.h>
#include <backends/imgui_impl_glfw.h>
#include <backends/imgui_impl_opengl3.h>
#include <iostream>

#include "gldebug.hpp"

void show_overlay(float* clear_color) {
    static std::string gl_vendor = (const char *) glGetString(GL_VENDOR);
    static std::string gl_renderer = (const char *) glGetString(GL_RENDERER);
    static std::string gl_version = (const char *) glGetString(GL_VERSION);
    static std::string glsl_version = (const char *) glGetString(GL_SHADING_LANGUAGE_VERSION);

    ImGuiWindowFlags window_flags =
        ImGuiWindowFlags_AlwaysAutoResize |
            ImGuiWindowFlags_NoSavedSettings |
            ImGuiWindowFlags_NoFocusOnAppearing |
            ImGuiWindowFlags_NoNav |
            ImGuiWindowFlags_NoBringToFrontOnFocus |
            ImGuiWindowFlags_NoMove;

    ImGuiStyle &style = ImGui::GetStyle();
    const auto PAD = style.DisplaySafeAreaPadding;
    auto window_pos = PAD;

    ImGui::SetNextWindowPos(window_pos, ImGuiCond_Always);
    ImGui::SetNextWindowBgAlpha(0.35f * style.Alpha);
    ImGui::SetNextWindowCollapsed(true, ImGuiCond_Appearing);
    ImGui::Begin("Graphics Information", nullptr, window_flags);
    ImGui::Text("GL Vendor    | %s", gl_vendor.c_str());
    ImGui::Text("GL Renderer  | %s", gl_renderer.c_str());
    ImGui::Text("GL Version   | %s", gl_version.c_str());
    ImGui::Text("GLSL Version | %s", glsl_version.c_str());

    auto v2 = ImGui::GetWindowSize();
    window_pos.y += v2.y + PAD.y;
    ImGui::End();

    ImGui::SetNextWindowPos(window_pos, ImGuiCond_Always);
    ImGui::SetNextWindowBgAlpha(0.35f * style.Alpha);
    ImGui::Begin("Controls", nullptr, window_flags);

    ImGuiIO &io = ImGui::GetIO();
    ImGui::Text("FPS          | %.2f", io.Framerate);

    ImGui::Separator();

    ImGui::ColorEdit3("Background", state.bg, ImGuiColorEditFlags_Float);
    ImGui::SliderFloat("Alpha", &state.fg[3], 0.0f, 1.0f, "%.2f");

    ImGui::End();
}

void set_style() {
    ImGui::StyleColorsDark();

    ImGuiStyle &style = ImGui::GetStyle();
    style.WindowRounding = 4;
    style.FrameRounding = 2;
    style.DisplaySafeAreaPadding.x = 10;
    style.DisplaySafeAreaPadding.y = 10;
}

int run(GLFWwindow *window, ImGuiContext *context) {
    State state;

    float points[]{
        +0.5f, +0.5f, 0.0f, 1.0f,
        +0.5f, -0.5f, 0.0f, 1.0f,
        -0.5f, +0.5f, 0.0f, 1.0f,
        -0.5f, -0.5f, 0.0f, 1.0f,
    };

    unsigned int inds[]{
        0, 1, 2,
        1, 2, 3,
    };

    GLuint vao;
    glCreateVertexArrays(1, &vao);

    GLuint vbo;
    glCreateBuffers(1, &vbo);

    glNamedBufferData(vbo, sizeof(points), (void *) points, GL_STATIC_DRAW);
    glEnableVertexArrayAttrib(vao, 0);
    glVertexArrayVertexBuffer(vao, 0, vbo, 0, sizeof(float) * 4);
    glVertexArrayAttribFormat(vao, 0, 4, GL_FLOAT, GL_FALSE, 0);

    GLuint ibo;
    glCreateBuffers(1, &ibo);
    glGetError();
    glNamedBufferData(ibo, sizeof(inds), (void *) inds, GL_STATIC_DRAW);
    glVertexArrayElementBuffer(vao, ibo);

    const char *vs_src = "#version 440\n"
                         "layout(location=0) in vec4 pos;"
                         "void main() {"
                         "  gl_Position = pos;"
                         "}";
    GLuint vs = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vs, 1, &vs_src, nullptr);
    glCompileShader(vs);

    const char *fs_src = "#version 440\n"
                         "layout(location=0) uniform vec4 ucol;"
                         "layout(location=0) out vec4 col;"
                         "void main() {"
                         "  col = ucol;"
                         "}";
    GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fs, 1, &fs_src, nullptr);
    glCompileShader(fs);

    GLuint pgm = glCreateProgram();
    glAttachShader(pgm, vs);
    glAttachShader(pgm, fs);
    glLinkProgram(pgm);

    while (!glfwWindowShouldClose(window)) {
        glfwPollEvents();

        ImGui_ImplOpenGL3_NewFrame();
        ImGui_ImplGlfw_NewFrame();
        ImGui::NewFrame();
        show_overlay(state);
        ImGui::Render();

        int display_w, display_h;
        glfwGetFramebufferSize(window, &display_w, &display_h);
        glViewport(0, 0, display_w, display_h);
        glClearColor(state.bg[0], state.bg[1], state.bg[2], state.bg[3]);
        glClear(GL_COLOR_BUFFER_BIT);

        glUseProgram(pgm);
        glBindVertexArray(vao);
        glUniform4fv(0, 1, state.fg);
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, nullptr);
        glBindVertexArray(0);
        glUseProgram(0);

        ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
        glfwSwapBuffers(window);
    }

    glDeleteBuffers(1, &vbo);
    glDeleteBuffers(1, &ibo);
    glDeleteVertexArrays(1, &vao);

    return EXIT_SUCCESS;
}

int main() {
    if (!glfwInit()) {
        std::cerr << "GLFW:Failed initialization" << std::endl;
        return EXIT_FAILURE;
    }

    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 6);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    auto *window = glfwCreateWindow(1280, 720, "Cosets Visualization", nullptr, nullptr);
    if (!window) {
        std::cerr << "GLFW:Failed to create window" << std::endl;
        return EXIT_FAILURE;
    }

    glfwMakeContextCurrent(window);
    glfwSwapInterval(1);
    gladLoadGLLoader((GLADloadproc) glfwGetProcAddress);

#ifndef NDEBUG
    glEnable(GL_DEBUG_OUTPUT);
    glDebugMessageCallback(log_gl_debug_callback, nullptr);
    glDebugMessageControl(
        GL_DONT_CARE, GL_DEBUG_TYPE_OTHER,
        GL_DEBUG_SEVERITY_NOTIFICATION,
        0, nullptr, GL_FALSE
    );
#endif

    IMGUI_CHECKVERSION();
    auto *context = ImGui::CreateContext();
    ImGui_ImplGlfw_InitForOpenGL(window, true);
    ImGui_ImplOpenGL3_Init("#version 130");

    set_style();

    int exit_code = EXIT_SUCCESS;

    try {
        exit_code = run(window, context);
    } catch (const std::exception &e) {
        std::cerr << e.what() << std::endl;
        exit_code = EXIT_FAILURE;
    }

    ImGui_ImplOpenGL3_Shutdown();
    ImGui_ImplGlfw_Shutdown();
    ImGui::DestroyContext();

    glfwDestroyWindow(window);
    glfwTerminate();

    return exit_code;
}