#include <destrum/App.h>

#include <algorithm>
#include <cmath>
#include <exception>
#include <thread>

#include <imgui.h>
#include <spdlog/spdlog.h>
#include <tracy/Tracy.hpp>
#include <common/TracySystem.hpp>

#include <destrum/Audio/AudioSystem.h>
#include <destrum/FS/AssetFS.h>
#include <destrum/Graphics/Resources/FontCache.h>
#include <destrum/Scene/ResourceCollector.h>
#include <destrum/Scene/Scene.h>
#include <destrum/Scene/SceneManager.h>
#include <destrum/Threading/JobSystem.h>
#include <destrum/Util/DeltaTime.h>

namespace {
    struct TracyFrameScope {
        ~TracyFrameScope() { FrameMark; }
    };

    constexpr float MaxFrameDelta = 0.25f;
    constexpr int MaxFixedSteps = 5;

    [[nodiscard]] bool IsMouseEvent(const SDL_Event& event)
    {
        return event.type == SDL_MOUSEBUTTONDOWN || event.type == SDL_MOUSEBUTTONUP ||
               event.type == SDL_MOUSEMOTION || event.type == SDL_MOUSEWHEEL;
    }

    [[nodiscard]] bool IsKeyboardEvent(const SDL_Event& event)
    {
        return event.type == SDL_KEYDOWN || event.type == SDL_KEYUP || event.type == SDL_TEXTINPUT;
    }
}

App::App() = default;

App::~App()
{
    if (!cleanedUp) {
        try {
            cleanup();
        } catch (...) {
        }
    }
}

void App::init(const AppParams& params)
{
    ZoneScopedN("App::init");
    cleanedUp = false;
    customInitStarted = false;
    try {
        m_params = params;
        tracy::SetThreadName("Main Thread");
        TracySetProgramName(params.appName.c_str());
        AssetFS::GetInstance().Init(params.exeDir);
        JobSystem::GetInstance().Init();

        window.Create({
            .title = params.windowTitle,
            .size = params.windowSize,
            .mode = params.windowMode,
            .maximized = params.startMaximized,
        });

        gfxDevice.init(window.GetHandle(), params.appName, false);
        imguiPass.init(window.GetHandle(), gfxDevice);
        resources.init(gfxDevice);
        renderer.init(gfxDevice, resources, params.renderSize);

        InputManager::GetInstance().Init();
        AudioSystem::GetInstance().Init();
        Time::GetInstance().Update();

        customInitStarted = true;
        customInit();
    } catch (...) {
        try {
            cleanup();
        } catch (...) {
        }
        throw;
    }
}

void App::attachLayer(std::unique_ptr<AppLayer> newLayer)
{
    if (layer) {
        layer->onDetach();
    }
    layer = std::move(newLayer);
    if (layer) {
        layer->onAttach();
    }
}

bool App::isPlaying() const
{
    return SceneManager::GetInstance().IsPlaying();
}

bool App::isPaused() const
{
    return SceneManager::GetInstance().IsPaused();
}

float App::getRenderAspectRatio() const
{
    const VkExtent3D extent = renderer.getDrawImage().extent;
    return extent.height > 0 ? static_cast<float>(extent.width) / static_cast<float>(extent.height) : 1.0f;
}

Camera& App::getViewCamera()
{
    if (layer) {
        if (Camera* camera = layer->viewCamera()) {
            return *camera;
        }
    }
    if (Camera* camera = gameCamera()) {
        return *camera;
    }
    return fallbackCamera;
}

void App::resizeRenderTarget(const glm::ivec2& size)
{
    renderer.resize(gfxDevice, size);
}

void App::collectUnusedResources()
{
    CollectUnusedResources(SceneManager::GetInstance(), resources, gfxDevice);
    AudioSystem::GetInstance().ReleaseUnusedClips();
}

void App::run()
{
    ZoneScopedN("App::run");

    Time::GetInstance().Update();
    simulation.fixedDeltaTime = static_cast<float>(Time::GetInstance().FixedDeltaTime());
    isRunning = true;

    while (isRunning) {
        TracyFrameScope tracyFrame;
        ZoneScopedN("App::Frame");

        Time::GetInstance().Update();
        const float dt = std::min(static_cast<float>(Time::GetInstance().DeltaTime()), MaxFrameDelta);
        if (dt > 0.0f) {
            avgFPS = std::lerp(avgFPS, 1.0f / dt, 0.1f);
            TracyPlot("FPS", avgFPS);
        }
        simulation.accumulator += dt;

        processEvents();
        if (!isRunning) {
            break;
        }

        if (window.IsMinimized()) {
            // The surface is 0x0 while minimized, there is nothing to render or present to
            simulation.accumulator = 0.0f;
            std::this_thread::sleep_for(std::chrono::milliseconds(16));
            continue;
        }

        JobSystem::GetInstance().DrainMainThreadQueue();
        if (layer) {
            layer->onBeginFrame();
        }

        imguiPass.beginFrame();
        if (layer) {
            layer->onImGuiBegin(dt);
        }

        {
            ZoneScopedN("Update");
            customUpdate(dt);
            SceneManager::GetInstance().Update(dt);
            SceneManager::GetInstance().LateUpdate(dt);
        }

        if (layer) {
            ZoneScopedN("Layer ImGui");
            layer->onImGui(dt);
        }
        imguiPass.endFrame();

        if (layer) {
            layer->onEndFrame();
        }

        runFixedSteps();

        AudioSystem::GetInstance().Update(dt, isPlaying() && (isPaused() || simulation.paused), &getViewCamera());

        bool skipFrame = false;
        handleSwapchainResize(skipFrame);
        if (skipFrame) {
            continue;
        }

        renderFrame();

        if (frameLimit) {
            if (const auto sleepTime = Time::GetInstance().SleepDuration(); sleepTime.count() > 0) {
                std::this_thread::sleep_for(sleepTime);
            }
        }
    }
}

void App::processEvents()
{
    ZoneScopedN("SDL Events");
    auto& input = InputManager::GetInstance();
    input.BeginFrame();

    SDL_Event event;
    while (SDL_PollEvent(&event)) {
        imguiPass.handleEvent(event);

        if (event.type == SDL_QUIT) {
            isRunning = false;
            return;
        }

        window.ProcessEvent(event);
        if (window.ConsumeResized()) {
            resizePending = true;
            lastResizeTime = std::chrono::steady_clock::now();
        }
        if (window.ConsumeCloseRequested()) {
            isRunning = false;
            return;
        }

        // ImGui wants every event while one of its windows is hovered or focused, a layer can claim
        // them back for the game (the editor viewport is an ImGui window)
        const AppLayer::InputFocus focus = layer ? layer->gameInputFocus() : AppLayer::InputFocus{};
        const bool mouseCaptured = input.IsMouseCaptured();
        const bool capturedByImgui =
            (IsMouseEvent(event) && !mouseCaptured && !focus.mouse && imguiPass.wantsMouse()) ||
            (IsKeyboardEvent(event) && !focus.keyboard && imguiPass.wantsKeyboard());

        if (!capturedByImgui && input.ProcessEvent(event)) {
            isRunning = false;
        }
    }
}

void App::runFixedSteps()
{
    ZoneScopedN("FixedUpdate");
    const float step = simulation.fixedDeltaTime * simulation.timeScale;
    int steps = 0;

    const auto fixedUpdate = [&] {
        customFixedUpdate(step);
        SceneManager::GetInstance().FixedUpdate(step);
    };

    if (simulation.paused) {
        simulation.accumulator = 0.0f;
        if (simulation.stepOnce) {
            fixedUpdate();
            steps = 1;
            simulation.stepOnce = false;
        }
    } else {
        while (simulation.accumulator >= simulation.fixedDeltaTime && steps < MaxFixedSteps) {
            fixedUpdate();
            simulation.accumulator -= simulation.fixedDeltaTime;
            ++steps;
        }
        if (steps == MaxFixedSteps) {
            simulation.accumulator = 0.0f;
        }
    }

    simulation.stepsLastFrame = steps;
    Time::GetInstance().SetFixedAlpha(std::clamp(simulation.accumulator / simulation.fixedDeltaTime, 0.0f, 1.0f));
}

void App::handleSwapchainResize(bool& skipFrame)
{
    if (!gfxDevice.needsSwapchainRecreate() && !resizePending) {
        return;
    }

    skipFrame = true;
    if (resizePending && std::chrono::steady_clock::now() - lastResizeTime < std::chrono::milliseconds(100)) {
        return;
    }

    const glm::ivec2 size = window.GetDrawableSize();
    if (size.x == 0 || size.y == 0 || !gfxDevice.recreateSwapchain(size.x, size.y)) {
        return;
    }

    spdlog::info("Recreated swapchain at {}x{}", size.x, size.y);
    imguiPass.onSwapchainRecreated();
    if (!layer || !layer->hostsViewport()) {
        resizeRenderTarget(size);
    }
    onWindowResize(size.x, size.y);
    resizePending = false;
}

void App::renderFrame()
{
    ZoneScopedN("Render");
    const VkCommandBuffer cmd = gfxDevice.beginFrame();
    if (cmd == VK_NULL_HANDLE) {
        return;
    }

    renderer.beginDrawing(gfxDevice);
    customRender(renderer);
    if (layer) {
        layer->onRender(renderer);
    }

    Camera& camera = getViewCamera();
    if (const float aspectRatio = getRenderAspectRatio(); camera.GetAspectRatio() != aspectRatio) {
        camera.setAspectRatio(aspectRatio);
    }

    auto& sceneManager = SceneManager::GetInstance();
    const SceneEnvironment environment = sceneManager.GetActiveScenes().empty()
        ? SceneEnvironment{}
        : sceneManager.GetCurrentScene().GetEnvironment();
    const GameRenderer::SceneData sceneData{
        .camera = camera,
        .ambientColor = environment.ambientColor,
        .ambientIntensity = environment.ambientIntensity,
        .fogColor = environment.fogColor,
        .fogDensity = environment.fogDensity,
        .skyboxRotation = environment.skyboxRotation,
        .exposure = environment.exposure,
        .tonemapper = environment.tonemapper,
    };

    sceneManager.Render(RenderContext{
        .renderer = renderer,
        .camera = camera,
        .sceneData = sceneData,
    });
    renderer.endDrawing();
    renderer.draw(cmd, gfxDevice, camera, sceneData);

    gfxDevice.endFrame(cmd, renderer.getDrawImage(), {
        .clearColor = {{0.0f, 0.0f, 0.0f, 1.0f}},
        .imguiPass = &imguiPass,
        .copyDrawImageToSwapchain = !layer || !layer->hostsViewport(),
    });
}

void App::cleanup()
{
    if (cleanedUp || cleaningUp) {
        return;
    }

    cleaningUp = true;
    spdlog::info("Cleaning up");

    std::exception_ptr firstException;
    const auto attempt = [&firstException](auto&& operation) {
        try {
            operation();
        } catch (...) {
            if (!firstException) {
                firstException = std::current_exception();
            }
        }
    };

    // The one place we wait for the GPU on shutdown: the cleanup calls below destroy
    // pipelines and other objects directly, which is only valid once nothing is in flight.
    attempt([this] { gfxDevice.waitIdle(); });
    attempt([] { JobSystem::GetInstance().Shutdown(); });

    attempt([this] {
        if (layer) {
            layer->onDetach();
            layer.reset();
        }
    });
    if (customInitStarted) {
        attempt([this] { customCleanup(); });
    }
    attempt([] { SceneManager::GetInstance().Destroy(); });
    attempt([] { AudioSystem::GetInstance().Shutdown(); });
    attempt([] { FontCache::GetInstance().Clear(); });
    attempt([this] { renderer.cleanup(gfxDevice); });
    attempt([this] { imguiPass.cleanup(); });
    attempt([this] { resources.cleanup(gfxDevice); });
    attempt([this] { gfxDevice.cleanup(); });

    window.Destroy();

    AssetFS::GetInstance().Reset();
    customInitStarted = false;
    cleanedUp = true;
    cleaningUp = false;

    if (firstException) {
        std::rethrow_exception(firstException);
    }
}