#include "Application.h"

#include "SandboxFrameBuilder.h"

#include <algorithm>
#include <chrono>
#include <filesystem>
#include <string>
#include <system_error>
#include <unordered_set>
#include <vector>

#ifndef XCNEWEDITOR_REPO_ROOT
#define XCNEWEDITOR_REPO_ROOT "."
#endif

namespace XCEngine {
namespace NewEditor {

namespace {

using ::XCEngine::UI::UIColor;
using ::XCEngine::UI::UIDrawData;
using ::XCEngine::UI::UIDrawList;
using ::XCEngine::UI::UIPoint;
using ::XCEngine::UI::UIRect;
using ::XCEngine::UI::Runtime::UIScreenFrameInput;

constexpr const wchar_t* kWindowClassName = L"XCNewEditorNativeSandbox";
constexpr const wchar_t* kWindowTitle = L"XCNewEditor Native Sandbox";
constexpr auto kReloadPollInterval = std::chrono::milliseconds(150);

constexpr UIColor kOverlayBgColor(0.10f, 0.10f, 0.10f, 0.95f);
constexpr UIColor kOverlayBorderColor(0.25f, 0.25f, 0.25f, 1.0f);
constexpr UIColor kOverlayTextPrimary(0.93f, 0.93f, 0.93f, 1.0f);
constexpr UIColor kOverlayTextMuted(0.70f, 0.70f, 0.70f, 1.0f);
constexpr UIColor kOverlaySuccess(0.82f, 0.82f, 0.82f, 1.0f);
constexpr UIColor kOverlayFallback(0.56f, 0.56f, 0.56f, 1.0f);

Application* GetApplicationFromWindow(HWND hwnd) {
    return reinterpret_cast<Application*>(GetWindowLongPtrW(hwnd, GWLP_USERDATA));
}

std::string TruncateText(const std::string& text, std::size_t maxLength) {
    if (text.size() <= maxLength) {
        return text;
    }

    if (maxLength <= 3u) {
        return text.substr(0, maxLength);
    }

    return text.substr(0, maxLength - 3u) + "...";
}

} // namespace

Application::Application()
    : m_screenPlayer(m_documentHost) {
}

int Application::Run(HINSTANCE hInstance, int nCmdShow) {
    if (!Initialize(hInstance, nCmdShow)) {
        Shutdown();
        return 1;
    }

    MSG message = {};
    while (message.message != WM_QUIT) {
        if (PeekMessageW(&message, nullptr, 0U, 0U, PM_REMOVE)) {
            TranslateMessage(&message);
            DispatchMessageW(&message);
            continue;
        }

        RenderFrame();
        Sleep(8);
    }

    Shutdown();
    return static_cast<int>(message.wParam);
}

bool Application::Initialize(HINSTANCE hInstance, int nCmdShow) {
    m_hInstance = hInstance;

    WNDCLASSEXW windowClass = {};
    windowClass.cbSize = sizeof(windowClass);
    windowClass.style = CS_HREDRAW | CS_VREDRAW;
    windowClass.lpfnWndProc = &Application::WndProc;
    windowClass.hInstance = hInstance;
    windowClass.hCursor = LoadCursorW(nullptr, IDC_ARROW);
    windowClass.lpszClassName = kWindowClassName;

    m_windowClassAtom = RegisterClassExW(&windowClass);
    if (m_windowClassAtom == 0) {
        return false;
    }

    m_hwnd = CreateWindowExW(
        0,
        kWindowClassName,
        kWindowTitle,
        WS_OVERLAPPEDWINDOW | WS_VISIBLE,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        1440,
        900,
        nullptr,
        nullptr,
        hInstance,
        this);
    if (m_hwnd == nullptr) {
        return false;
    }

    ShowWindow(m_hwnd, nCmdShow);
    UpdateWindow(m_hwnd);

    if (!m_renderer.Initialize(m_hwnd)) {
        return false;
    }

    m_startTime = std::chrono::steady_clock::now();
    m_lastFrameTime = m_startTime;
    m_autoScreenshot.Initialize(ResolveRepoRelativePath("new_editor/captures"));
    LoadStructuredScreen("startup");
    return true;
}

void Application::Shutdown() {
    m_autoScreenshot.Shutdown();
    m_screenPlayer.Unload();
    m_trackedFiles.clear();
    m_screenAsset = {};
    m_useStructuredScreen = false;
    m_runtimeStatus.clear();
    m_runtimeError.clear();
    m_frameIndex = 0;

    m_renderer.Shutdown();

    if (m_hwnd != nullptr && IsWindow(m_hwnd)) {
        DestroyWindow(m_hwnd);
    }
    m_hwnd = nullptr;

    if (m_windowClassAtom != 0 && m_hInstance != nullptr) {
        UnregisterClassW(kWindowClassName, m_hInstance);
        m_windowClassAtom = 0;
    }
}

void Application::RenderFrame() {
    if (m_hwnd == nullptr) {
        return;
    }

    RECT clientRect = {};
    GetClientRect(m_hwnd, &clientRect);
    const float width = static_cast<float>((std::max)(clientRect.right - clientRect.left, 1L));
    const float height = static_cast<float>((std::max)(clientRect.bottom - clientRect.top, 1L));

    const auto now = std::chrono::steady_clock::now();
    const double timeSeconds = std::chrono::duration<double>(now - m_startTime).count();
    double deltaTimeSeconds = std::chrono::duration<double>(now - m_lastFrameTime).count();
    if (deltaTimeSeconds <= 0.0) {
        deltaTimeSeconds = 1.0 / 60.0;
    }
    m_lastFrameTime = now;

    RefreshStructuredScreen();

    UIDrawData drawData = {};
    if (m_useStructuredScreen && m_screenPlayer.IsLoaded()) {
        UIScreenFrameInput input = {};
        input.viewportRect = UIRect(0.0f, 0.0f, width, height);
        input.deltaTimeSeconds = deltaTimeSeconds;
        input.frameIndex = ++m_frameIndex;
        input.focused = GetForegroundWindow() == m_hwnd;

        const auto& frame = m_screenPlayer.Update(input);
        for (const auto& drawList : frame.drawData.GetDrawLists()) {
            drawData.AddDrawList(drawList);
        }

        m_runtimeStatus = "Authored XCUI";
        m_runtimeError = frame.errorMessage;
    }

    if (drawData.Empty()) {
        SandboxFrameOptions options = {};
        options.width = width;
        options.height = height;
        options.timeSeconds = timeSeconds;
        drawData = BuildSandboxFrame(options);
        m_runtimeStatus = "Fallback Sandbox";
        if (m_runtimeError.empty() && !m_screenPlayer.IsLoaded()) {
            m_runtimeError = m_screenPlayer.GetLastError();
        }
    }

    AppendRuntimeOverlay(drawData, width, height);

    const bool framePresented = m_renderer.Render(drawData);
    m_autoScreenshot.CaptureIfRequested(
        m_renderer,
        drawData,
        static_cast<unsigned int>(width),
        static_cast<unsigned int>(height),
        framePresented);
}

void Application::OnResize(UINT width, UINT height) {
    if (width == 0 || height == 0) {
        return;
    }

    m_renderer.Resize(width, height);
}

bool Application::LoadStructuredScreen(const char* triggerReason) {
    m_screenAsset = {};
    m_screenAsset.screenId = "new_editor.editor_shell";
    m_screenAsset.documentPath = ResolveRepoRelativePath("new_editor/ui/views/editor_shell.xcui").string();
    m_screenAsset.themePath = ResolveRepoRelativePath("new_editor/ui/themes/editor_shell.xctheme").string();

    const bool loaded = m_screenPlayer.Load(m_screenAsset);
    m_useStructuredScreen = loaded;
    m_runtimeStatus = loaded ? "Authored XCUI" : "Fallback Sandbox";
    m_runtimeError = loaded ? std::string() : m_screenPlayer.GetLastError();
    RebuildTrackedFileStates();

    std::string screenshotReason = triggerReason != nullptr ? triggerReason : "update";
    screenshotReason += loaded ? "_authored" : "_fallback";
    m_autoScreenshot.RequestCapture(std::move(screenshotReason));
    return loaded;
}

void Application::RefreshStructuredScreen() {
    const auto now = std::chrono::steady_clock::now();
    if (m_lastReloadPollTime.time_since_epoch().count() != 0 &&
        now - m_lastReloadPollTime < kReloadPollInterval) {
        return;
    }

    m_lastReloadPollTime = now;
    if (DetectTrackedFileChange()) {
        LoadStructuredScreen("reload");
    }
}

void Application::RebuildTrackedFileStates() {
    namespace fs = std::filesystem;

    m_trackedFiles.clear();
    std::unordered_set<std::string> seenPaths = {};
    std::error_code errorCode = {};

    auto appendTrackedPath = [&](const std::string& rawPath) {
        if (rawPath.empty()) {
            return;
        }

        const fs::path normalizedPath = fs::path(rawPath).lexically_normal();
        const std::string key = normalizedPath.string();
        if (!seenPaths.insert(key).second) {
            return;
        }

        TrackedFileState state = {};
        state.path = normalizedPath;
        state.exists = fs::exists(normalizedPath, errorCode);
        errorCode.clear();
        if (state.exists) {
            state.writeTime = fs::last_write_time(normalizedPath, errorCode);
            errorCode.clear();
        }
        m_trackedFiles.push_back(std::move(state));
    };

    appendTrackedPath(m_screenAsset.documentPath);
    appendTrackedPath(m_screenAsset.themePath);

    if (const auto* document = m_screenPlayer.GetDocument(); document != nullptr) {
        for (const std::string& dependency : document->dependencies) {
            appendTrackedPath(dependency);
        }
    }
}

bool Application::DetectTrackedFileChange() const {
    namespace fs = std::filesystem;

    std::error_code errorCode = {};
    for (const TrackedFileState& trackedFile : m_trackedFiles) {
        const bool existsNow = fs::exists(trackedFile.path, errorCode);
        errorCode.clear();
        if (existsNow != trackedFile.exists) {
            return true;
        }

        if (!existsNow) {
            continue;
        }

        const auto writeTimeNow = fs::last_write_time(trackedFile.path, errorCode);
        errorCode.clear();
        if (writeTimeNow != trackedFile.writeTime) {
            return true;
        }
    }

    return false;
}

void Application::AppendRuntimeOverlay(UIDrawData& drawData, float width, float height) const {
    const bool authoredMode = m_useStructuredScreen && m_screenPlayer.IsLoaded();
    const float panelWidth = authoredMode ? 256.0f : 360.0f;
    std::vector<std::string> detailLines = {};
    detailLines.push_back(
        authoredMode
            ? "Hot reload watches authored UI resources."
            : "Using native fallback while authored UI is invalid.");

    if (m_autoScreenshot.HasPendingCapture()) {
        detailLines.push_back("Shot pending...");
    } else if (!m_autoScreenshot.GetLastCaptureSummary().empty()) {
        detailLines.push_back(TruncateText(m_autoScreenshot.GetLastCaptureSummary(), 78u));
    }

    if (!m_runtimeError.empty()) {
        detailLines.push_back(TruncateText(m_runtimeError, 78u));
    } else if (!m_autoScreenshot.GetLastCaptureError().empty()) {
        detailLines.push_back(TruncateText(m_autoScreenshot.GetLastCaptureError(), 78u));
    }

    const float panelHeight = 38.0f + static_cast<float>(detailLines.size()) * 18.0f;
    const UIRect panelRect(width - panelWidth - 16.0f, height - panelHeight - 42.0f, panelWidth, panelHeight);

    UIDrawList& overlay = drawData.EmplaceDrawList("NewEditor Runtime Overlay");
    overlay.AddFilledRect(panelRect, kOverlayBgColor, 10.0f);
    overlay.AddRectOutline(panelRect, kOverlayBorderColor, 1.0f, 10.0f);
    overlay.AddFilledRect(
        UIRect(panelRect.x + 12.0f, panelRect.y + 14.0f, 8.0f, 8.0f),
        authoredMode ? kOverlaySuccess : kOverlayFallback,
        4.0f);
    overlay.AddText(
        UIPoint(panelRect.x + 28.0f, panelRect.y + 10.0f),
        m_runtimeStatus.empty() ? "Runtime State" : m_runtimeStatus,
        kOverlayTextPrimary,
        14.0f);

    float detailY = panelRect.y + 30.0f;
    for (std::size_t index = 0; index < detailLines.size(); ++index) {
        const bool lastLine = index + 1u == detailLines.size();
        overlay.AddText(
            UIPoint(panelRect.x + 28.0f, detailY),
            detailLines[index],
            lastLine && (!m_runtimeError.empty() || !m_autoScreenshot.GetLastCaptureError().empty())
                ? kOverlayFallback
                : kOverlayTextMuted,
            12.0f);
        detailY += 18.0f;
    }
}

std::filesystem::path Application::ResolveRepoRelativePath(const char* relativePath) {
    return (std::filesystem::path(XCNEWEDITOR_REPO_ROOT) / relativePath).lexically_normal();
}

LRESULT CALLBACK Application::WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) {
    if (message == WM_NCCREATE) {
        const auto* createStruct = reinterpret_cast<CREATESTRUCTW*>(lParam);
        auto* application = reinterpret_cast<Application*>(createStruct->lpCreateParams);
        SetWindowLongPtrW(hwnd, GWLP_USERDATA, reinterpret_cast<LONG_PTR>(application));
        return TRUE;
    }

    Application* application = GetApplicationFromWindow(hwnd);
    switch (message) {
    case WM_SIZE:
        if (application != nullptr && wParam != SIZE_MINIMIZED) {
            application->OnResize(static_cast<UINT>(LOWORD(lParam)), static_cast<UINT>(HIWORD(lParam)));
        }
        return 0;
    case WM_PAINT:
        if (application != nullptr) {
            PAINTSTRUCT paintStruct = {};
            BeginPaint(hwnd, &paintStruct);
            application->RenderFrame();
            EndPaint(hwnd, &paintStruct);
            return 0;
        }
        break;
    case WM_ERASEBKGND:
        return 1;
    case WM_DESTROY:
        if (application != nullptr) {
            application->m_hwnd = nullptr;
        }
        PostQuitMessage(0);
        return 0;
    default:
        break;
    }

    return DefWindowProcW(hwnd, message, wParam, lParam);
}

int RunNewEditor(HINSTANCE hInstance, int nCmdShow) {
    Application application = {};
    return application.Run(hInstance, nCmdShow);
}

} // namespace NewEditor
} // namespace XCEngine