#include <backends/imgui_impl_sdl2.h>
#include <backends/imgui_impl_sdlrenderer2.h>
#include <iostream>
#include "MainWindow.hpp"
#include "exceptions.hpp"
#include "../format.hpp"
#include "../Resources/fonts.hpp"
#include "../Resources/textures.hpp"
#include "../math.hpp"

namespace ougge::GUI {

f32 MainWindow::getDPI(){
    int w=0, h=0;
    SDL_GetRendererOutputSize(sdl_renderer, &w, &h);
    int sim_w=0, sim_h=0;
    SDL_GetWindowSize(sdl_window, &sim_w, &sim_h);
    f32 wdpi=(f32)w / sim_w;
    f32 hdpi=(f32)h / sim_h;
    f32 dpi=SDL_sqrtf(wdpi*wdpi + hdpi*hdpi);
    return dpi;
}

void MainWindow::open(const char* window_title, UpdateFunc_t _update){
    update = _update;

    SDL_TRY(SDL_Init(SDL_INIT_EVERYTHING));
    SDL_version v;
    SDL_GetVersion(&v);
    std::cout<<format("SDL version: %u.%u.%u\n", v.major, v.minor, v.patch);
    
    // From 2.0.18: Enable native IME.
#ifdef SDL_HINT_IME_SHOW_UI
    SDL_SetHint(SDL_HINT_IME_SHOW_UI, "1");
#endif
    
    SDL_WindowFlags window_flags = (SDL_WindowFlags)(
        SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI
    );
    sdl_window = SDL_CreateWindow(window_title,
        SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
        1280, 720, window_flags);
    if(sdl_window == nullptr)
        throw SDLException();
    
    SDL_RendererFlags renderer_flags = (SDL_RendererFlags)(
        SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC
    );
    sdl_renderer = SDL_CreateRenderer(sdl_window, -1, renderer_flags);
    if(sdl_renderer == nullptr)
        throw SDLException();
    
    SDL_RendererInfo info;
    SDL_GetRendererInfo(sdl_renderer, &info);
    std::cout<<"Current SDL_Renderer driver: "<<info.name<<std::endl;

    // Setup Dear ImGui context
    IMGUI_CHECKVERSION();
    ImGui::CreateContext();
    ImGuiIO& io = ImGui::GetIO();
    io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard; // Enable Keyboard Controls   
    io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;  // Enable Gamepad Controls
    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;     // Enable Docking
    io.ConfigDockingTransparentPayload = true;
    io.ConfigInputTextCursorBlink = false;
    // io.ConfigViewportsNoTaskBarIcon = true;
    io.ConfigWindowsMoveFromTitleBarOnly = true;

    // Setup Platform/Renderer backends
    if(!ImGui_ImplSDL2_InitForSDLRenderer(sdl_window, sdl_renderer))
        throw SDLException();
    if(!ImGui_ImplSDLRenderer2_Init(sdl_renderer))
        throw SDLException();

    // Setup Dear ImGui style
    ImGui::StyleColorsDark();
    f32 dpi = getDPI();
    io.FontDefault = Resources::ImFont_LoadFromResource(default_font, default_font_size, dpi);
}

// Wait, poll and handle events (inputs, window resize, etc.)
void MainWindow::poll_events(bool waitForEvent){
    SDL_Event event;
    if(waitForEvent){
        // waits for first event in cpu-efficient way
        SDL_TRY(SDL_WaitEvent(&event) != 1); 
    }
    // dont wait for event
    else if(!SDL_PollEvent(&event))
        return;
    
    do {
        ImGui_ImplSDL2_ProcessEvent(&event);
        switch(event.type){
            case SDL_QUIT: {
                close();
                break;
            }
            case SDL_WINDOWEVENT: {
                if(event.window.event == SDL_WINDOWEVENT_CLOSE && event.window.windowID == SDL_GetWindowID(sdl_window)){
                    close();
                }
                break;
            }
        }
    } while (SDL_PollEvent(&event)); // if there are more events, handles them
}

void ImGui_drawErrorWindow(bool* draw_error_window, std::string& msg){
    ImGui::Begin("ERROR", draw_error_window);
        ImGui::Text("%s", msg.c_str());
    ImGui::End();
}

void MainWindow::draw_ui(){
    static std::string error_message;
    static bool draw_error_window = false;
    try {
        // Draw UI
        if(draw_error_window)
            ImGui_drawErrorWindow(&draw_error_window, error_message);
        else {
            draw_bg_window();
            draw_debug_window();
        }
    }
    catch(const std::exception& e){
        error_message = "Catched exception: " + std::string(e.what());
        draw_error_window = true;
        std::cerr<<error_message<<std::endl;
    }
    catch(const char* cstr){
        error_message = "Catched error message (const char*): " + std::string(cstr);
        draw_error_window = true;
        std::cerr<<error_message<<std::endl;
    }
    catch(const std::string& str){
        error_message = "Catched error message (std::string): " + str;
        draw_error_window = true;
        std::cerr<<error_message<<std::endl;
    }
    catch(...){
        error_message = "Catched unknown error";
        draw_error_window = true;
        std::cerr<<error_message<<std::endl;
    }
}

void MainWindow::draw_frame(){
    // Start the Dear ImGui frame
    ImGui_ImplSDLRenderer2_NewFrame();
    ImGui_ImplSDL2_NewFrame();
    ImGui::NewFrame();

    draw_ui();

    // Rendering
    ImGui::Render();
    ImGuiIO& io = ImGui::GetIO();
    SDL_RenderSetScale(sdl_renderer, io.DisplayFramebufferScale.x, io.DisplayFramebufferScale.y);
    SDL_SetRenderDrawColor(sdl_renderer, (Uint8)(clear_color.x * 255), (Uint8)(clear_color.y * 255), (Uint8)(clear_color.z * 255), (Uint8)(clear_color.w * 255));
    SDL_RenderClear(sdl_renderer);

    // Example sprite
    //Resources::Texture tutel(Resources::getResource("tutel.png"), sdl_renderer);
    static Resources::CacheStorage<Resources::Texture> textures;
    Resources::Texture& tutel = textures.getOrCreate("tutel.png", sdl_renderer);
    Resources::SDL_RenderCopyExF_Params rp;
    rp.target_section = SDL_FRectConstruct(100, 100, 400, 400);
    static int si = 1;
    rp.rotation_angle = M_PI_4 * (si++ / fps_max);
    tutel.render(rp);


    ImGui_ImplSDLRenderer2_RenderDrawData(ImGui::GetDrawData(), sdl_renderer);
    // Swap buffers
    SDL_RenderPresent(sdl_renderer);
}

void MainWindow::startUpdateLoop(){
    if(loop_running)
        throw UsefulException("loop is running already");

    nsec_t prev_update_time_ns = getMonotonicTimeNsec();
    loop_running=true;
    // main loop
    while(loop_running){
        poll_events(false);
        
        nsec_t update_time_ns = getMonotonicTimeNsec();
        if(update_time_ns < prev_update_time_ns)
            throw UsefulException("monotonic clock returned unexpected value");
        f64 delta_time_s = (f64)(update_time_ns - prev_update_time_ns) / 1e9;
        prev_update_time_ns = update_time_ns;

        update(delta_time_s);
        draw_frame();

        nsec_t after_update_time_ns = getMonotonicTimeNsec();
        nsec_t frame_delay_ns = (nsec_t)1e9 / fps_max - (after_update_time_ns - update_time_ns);
        if(frame_delay_ns > 0){
            SDL_Delay(frame_delay_ns / 1e6);
        }
    }

    destroy();
}

void MainWindow::destroy(){
    ImGui_ImplSDLRenderer2_Shutdown();
    ImGui_ImplSDL2_Shutdown();
    ImGui::DestroyContext();
    SDL_DestroyRenderer(sdl_renderer);
    SDL_DestroyWindow(sdl_window);
    SDL_Quit();
}

void MainWindow::close(){
    loop_running = false;
}

void MainWindow::draw_bg_window(){
    const ImGuiDockNodeFlags dockspace_flags =
            ImGuiDockNodeFlags_PassthruCentralNode;
    const ImGuiWindowFlags window_flags =
        ImGuiWindowFlags_MenuBar |
        ImGuiWindowFlags_NoDocking |
        ImGuiWindowFlags_NoScrollbar |
        ImGuiWindowFlags_NoScrollWithMouse |
        ImGuiWindowFlags_NoBringToFrontOnFocus |
        ImGuiWindowFlags_NoFocusOnAppearing |
        ImGuiWindowFlags_NoMove |
        ImGuiWindowFlags_NoResize |
        ImGuiWindowFlags_NoCollapse |
        ImGuiWindowFlags_NoTitleBar |
        ImGuiWindowFlags_NoBackground;
    // not dockable window that always bound to viewport
    ImGuiViewport* viewport = ImGui::GetWindowViewport();
    ImGui::SetNextWindowPos(viewport->Pos, ImGuiCond_Always);
    ImGui::SetNextWindowSize(viewport->Size, ImGuiCond_Always);
    ImGui::PushStyleVar(ImGuiStyleVar_WindowRounding, 0.0f);
    ImGui::PushStyleVar(ImGuiStyleVar_WindowBorderSize, 0.0f);
	ImGui::PushStyleVar(ImGuiStyleVar_WindowPadding, ImVec2(0.0f, 0.0f));
    ImGui::Begin("bg_window", nullptr, window_flags);
    ImGui::PopStyleVar(3);

    // DockSpace
    ImGuiID dockspace_id = ImGui::GetID("bg_dockspace");
    ImGui::DockSpace(dockspace_id, ImVec2(0.0f, 0.0f), dockspace_flags);
    
    // MenuBar
    if(ImGui::BeginMainMenuBar()){
        if(ImGui::BeginMenu("test")){
            if(ImGui::MenuItem("throw exception")){
                ImGui::EndMenu();
                ImGui::EndMainMenuBar();
                ImGui::End();
                throw UsefulException("example exception");
            }
            if(ImGui::MenuItem("throw const char*")){
                ImGui::EndMenu();
                ImGui::EndMainMenuBar();
                ImGui::End();
                throw "cptr";
            }
            if(ImGui::MenuItem("throw std::string")){
                ImGui::EndMenu();
                ImGui::EndMainMenuBar();
                ImGui::End();
                throw std::string("str");
            }
            if(ImGui::MenuItem("throw unknown")){
                ImGui::EndMenu();
                ImGui::EndMainMenuBar();
                ImGui::End();
                throw 111;
            }
            ImGui::EndMenu();
        }
        ImGui::EndMainMenuBar();
    }

    ImGui::End();
}

void MainWindow::draw_debug_window(){
    ImGuiIO& io = ImGui::GetIO();
    ImGui::Begin("Debug Options");
        ImGui::ColorEdit3("clear_color", (float*)&clear_color);
        ImGui::InputInt("fps_max", &fps_max);
        ImGui::Text("Application average %.3f ms/frame (%.2f FPS)", 1000.0f / io.Framerate, io.Framerate);
        ImGui::Checkbox("Demo Window", &show_demo_window);
        ImGui::Checkbox("Metrics/Debug Window", &show_metrics_window);
    ImGui::End();

    if (show_demo_window)
        ImGui::ShowDemoWindow(&show_demo_window);

    if (show_metrics_window)
        ImGui::ShowMetricsWindow(&show_metrics_window);
}

}