#include "winnativeeventfilter.h"

#include <QDebug>
#include <QGuiApplication>
#include <QLibrary>
#include <QOperatingSystemVersion>
#include <QWindow>
#include <d2d1.h>
#include <dwmapi.h>
#include <shellapi.h>
#include <uxtheme.h>
#include <windowsx.h>

#ifndef SM_CXPADDEDBORDER
// Only available since Windows Vista
#define SM_CXPADDEDBORDER 92
#endif

#ifndef WM_NCUAHDRAWCAPTION
// Not documented, only available since Windows Vista
#define WM_NCUAHDRAWCAPTION 0x00AE
#endif

#ifndef WM_NCUAHDRAWFRAME
// Not documented, only available since Windows Vista
#define WM_NCUAHDRAWFRAME 0x00AF
#endif

#ifndef WM_DWMCOMPOSITIONCHANGED
// Only available since Windows 7
#define WM_DWMCOMPOSITIONCHANGED 0x031E
#endif

namespace {

QScopedPointer<WinNativeEventFilter> instance;
QVector<HWND> m_framelessWindows;

} // namespace

WinNativeEventFilter::WinNativeEventFilter() {
    QLibrary shcoreLib(QString::fromUtf8("SHCore"));
    if (QOperatingSystemVersion::current() >=
        QOperatingSystemVersion::Windows8_1) {
        m_GetDpiForMonitor = reinterpret_cast<lpGetDpiForMonitor>(
            shcoreLib.resolve("GetDpiForMonitor"));
    }
    QLibrary user32Lib(QString::fromUtf8("User32"));
    if (QOperatingSystemVersion::current() >=
        QOperatingSystemVersion::Windows7) {
        m_SetWindowCompositionAttribute =
            reinterpret_cast<lpSetWindowCompositionAttribute>(
                user32Lib.resolve("SetWindowCompositionAttribute"));
    }
    // Windows 10, version 1607 (10.0.14393)
    if (QOperatingSystemVersion::current() >=
        QOperatingSystemVersion(QOperatingSystemVersion::Windows, 10, 0,
                                14393)) {
        m_GetDpiForWindow = reinterpret_cast<lpGetDpiForWindow>(
            user32Lib.resolve("GetDpiForWindow"));
        m_GetDpiForSystem = reinterpret_cast<lpGetDpiForSystem>(
            user32Lib.resolve("GetDpiForSystem"));
        m_GetSystemMetricsForDpi = reinterpret_cast<lpGetSystemMetricsForDpi>(
            user32Lib.resolve("GetSystemMetricsForDpi"));
    }
    // Windows 10, version 1803 (10.0.17134)
    if (QOperatingSystemVersion::current() >=
        QOperatingSystemVersion(QOperatingSystemVersion::Windows, 10, 0,
                                17134)) {
        m_GetSystemDpiForProcess = reinterpret_cast<lpGetSystemDpiForProcess>(
            user32Lib.resolve("GetSystemDpiForProcess"));
    }
}

WinNativeEventFilter::~WinNativeEventFilter() = default;

void WinNativeEventFilter::install() {
    if (instance.isNull()) {
        instance.reset(new WinNativeEventFilter);
        qApp->installNativeEventFilter(instance.data());
    }
}

void WinNativeEventFilter::uninstall() {
    if (!instance.isNull()) {
        qApp->removeNativeEventFilter(instance.data());
        instance.reset();
    }
    if (!m_framelessWindows.isEmpty()) {
        for (auto &&window : qAsConst(m_framelessWindows)) {
            refreshWindow(window);
        }
        m_framelessWindows.clear();
    }
}

QVector<HWND> WinNativeEventFilter::framelessWindows() {
    return m_framelessWindows;
}

void WinNativeEventFilter::setFramelessWindows(QVector<HWND> windows) {
    if (!windows.isEmpty() && (windows != m_framelessWindows)) {
        m_framelessWindows = windows;
        install();
    }
}

void WinNativeEventFilter::addFramelessWindow(HWND window) {
    if (window && !m_framelessWindows.contains(window)) {
        m_framelessWindows.append(window);
        install();
    }
}

void WinNativeEventFilter::removeFramelessWindow(HWND window) {
    if (window && m_framelessWindows.contains(window)) {
        m_framelessWindows.removeAll(window);
    }
}

void WinNativeEventFilter::clearFramelessWindows() {
    if (!m_framelessWindows.isEmpty()) {
        m_framelessWindows.clear();
    }
}

UINT WinNativeEventFilter::windowDpi(HWND handle) const {
    return getDpiForWindow(handle);
}

qreal WinNativeEventFilter::windowDpr(HWND handle) const {
    return getDprForWindow(handle);
}

int WinNativeEventFilter::borderWidth(HWND handle) const {
    return getSystemMetricsForWindow(handle, SM_CXFRAME) +
        getSystemMetricsForWindow(handle, SM_CXPADDEDBORDER);
}

int WinNativeEventFilter::borderHeight(HWND handle) const {
    return getSystemMetricsForWindow(handle, SM_CYFRAME) +
        getSystemMetricsForWindow(handle, SM_CXPADDEDBORDER);
}

int WinNativeEventFilter::titlebarHeight(HWND handle) const {
    return borderHeight(handle) +
        getSystemMetricsForWindow(handle, SM_CYCAPTION);
}

void WinNativeEventFilter::refreshWindow(HWND handle) {
    if (handle) {
        SetWindowPos(handle, nullptr, 0, 0, 0, 0,
                     SWP_FRAMECHANGED | SWP_NOACTIVATE | SWP_NOSIZE |
                         SWP_NOMOVE | SWP_NOZORDER | SWP_NOOWNERZORDER);
    }
}

#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
bool WinNativeEventFilter::nativeEventFilter(const QByteArray &eventType,
                                             void *message, qintptr *result)
#else
bool WinNativeEventFilter::nativeEventFilter(const QByteArray &eventType,
                                             void *message, long *result)
#endif
{
    Q_UNUSED(eventType)
    const auto msg = static_cast<LPMSG>(message);
    if (!msg->hwnd) {
        // Why sometimes the window handle is null? Is it designed to be?
        // Anyway, we should skip it in this case.
        return false;
    }
    if (m_framelessWindows.isEmpty()) {
        bool isTopLevel = false;
        // QWidgets with Qt::WA_NativeWindow enabled will make them become top
        // level windows even if they are not. Try if
        // Qt::WA_DontCreateNativeAncestors helps.
        const auto topLevelWindows = QGuiApplication::topLevelWindows();
        for (auto &&window : qAsConst(topLevelWindows)) {
            if (window->handle() &&
                (msg->hwnd == reinterpret_cast<HWND>(window->winId()))) {
                isTopLevel = true;
                break;
            }
        }
        if (!isTopLevel) {
            return false;
        }
    } else if (!m_framelessWindows.contains(msg->hwnd)) {
        return false;
    }
    if (!m_windowData.contains(msg->hwnd)) {
        // We have to record every window's state.
        m_windowData.insert(msg->hwnd, qMakePair(FALSE, FALSE));
        init(msg->hwnd);
    }
    switch (msg->message) {
    case WM_NCCREATE: {
        // Work-around a long-existing Windows bug.
        const auto userData =
            reinterpret_cast<LPCREATESTRUCTW>(msg->lParam)->lpCreateParams;
        SetWindowLongPtrW(msg->hwnd, GWLP_USERDATA,
                          reinterpret_cast<LONG_PTR>(userData));
        break;
    }
    case WM_NCCALCSIZE: {
        if (static_cast<BOOL>(msg->wParam)) {
            if (IsMaximized(msg->hwnd)) {
                const HMONITOR monitor =
                    MonitorFromWindow(msg->hwnd, MONITOR_DEFAULTTONEAREST);
                if (monitor) {
                    MONITORINFO monitorInfo;
                    SecureZeroMemory(&monitorInfo, sizeof(monitorInfo));
                    monitorInfo.cbSize = sizeof(monitorInfo);
                    GetMonitorInfoW(monitor, &monitorInfo);
                    auto &params =
                        *reinterpret_cast<LPNCCALCSIZE_PARAMS>(msg->lParam);
                    params.rgrc[0] = monitorInfo.rcWork;
                    // If the client rectangle is the same as the monitor's
                    // rectangle, the shell assumes that the window has gone
                    // fullscreen, so it removes the topmost attribute from any
                    // auto-hide appbars, making them inaccessible. To avoid
                    // this, reduce the size of the client area by one pixel on
                    // a certain edge. The edge is chosen based on which side of
                    // the monitor is likely to contain an auto-hide appbar, so
                    // the missing client area is covered by it.
                    if (EqualRect(&params.rgrc[0], &monitorInfo.rcMonitor)) {
                        APPBARDATA abd;
                        SecureZeroMemory(&abd, sizeof(abd));
                        abd.cbSize = sizeof(abd);
                        const UINT taskbarState =
                            SHAppBarMessage(ABM_GETSTATE, &abd);
                        if (taskbarState & ABS_AUTOHIDE) {
                            int edge = -1;
                            abd.hWnd = FindWindowW(L"Shell_TrayWnd", nullptr);
                            if (abd.hWnd) {
                                const HMONITOR taskbarMonitor =
                                    MonitorFromWindow(abd.hWnd,
                                                      MONITOR_DEFAULTTONEAREST);
                                if (taskbarMonitor &&
                                    (taskbarMonitor == monitor)) {
                                    SHAppBarMessage(ABM_GETTASKBARPOS, &abd);
                                    edge = abd.uEdge;
                                }
                            }
                            if (edge == ABE_BOTTOM) {
                                params.rgrc[0].bottom--;
                            } else if (edge == ABE_LEFT) {
                                params.rgrc[0].left++;
                            } else if (edge == ABE_TOP) {
                                params.rgrc[0].top++;
                            } else if (edge == ABE_RIGHT) {
                                params.rgrc[0].right--;
                            }
                        }
                    }
                }
            }
            // This line removes the window frame (including the titlebar).
            // But the frame shadow is lost at the same time. We'll bring it
            // back later.
            *result = WVR_REDRAW;
        } else {
            *result = 0;
        }
        return true;
    }
    case WM_DWMCOMPOSITIONCHANGED: {
        // Bring the frame shadow back through DWM.
        // Don't paint the shadow manually using QPainter or QGraphicsEffect.
        handleDwmCompositionChanged(msg->hwnd);
        *result = 0;
        return true;
    }
    case WM_NCUAHDRAWCAPTION:
    case WM_NCUAHDRAWFRAME: {
        // These undocumented messages are sent to draw themed window
        // borders. Block them to prevent drawing borders over the client
        // area.
        *result = 0;
        return true;
    }
    case WM_NCPAINT: {
        if (m_windowData.value(msg->hwnd).first) {
            break;
        } else {
            // Only block WM_NCPAINT when composition is disabled. If it's
            // blocked when composition is enabled, the window shadow won't
            // be drawn.
            *result = 0;
            return true;
        }
    }
    case WM_NCACTIVATE: {
        // DefWindowProc won't repaint the window border if lParam (normally
        // a HRGN) is -1.
        *result = DefWindowProcW(msg->hwnd, msg->message, msg->wParam, -1);
        return true;
    }
    case WM_NCHITTEST: {
        const auto getHTResult = [this](HWND _hWnd, LPARAM _lParam) -> LRESULT {
            RECT clientRect = {0, 0, 0, 0};
            GetClientRect(_hWnd, &clientRect);
            const LONG ww = clientRect.right;
            const LONG wh = clientRect.bottom;
            POINT mouse = {LONG(GET_X_LPARAM(_lParam)),
                           LONG(GET_Y_LPARAM(_lParam))};
            ScreenToClient(_hWnd, &mouse);
            // These values are DPI-aware.
            const LONG bw = borderWidth(_hWnd);
            const LONG bh = borderHeight(_hWnd);
            const LONG tbh = titlebarHeight(_hWnd);
            if (IsMaximized(_hWnd)) {
                if (mouse.y < tbh) {
                    return HTCAPTION;
                }
                return HTCLIENT;
            }
            if (mouse.y < bh) {
                if (mouse.x < bw) {
                    return HTTOPLEFT;
                }
                if (mouse.x > (ww - bw)) {
                    return HTTOPRIGHT;
                }
                return HTTOP;
            }
            if (mouse.y > (wh - bh)) {
                if (mouse.x < bw) {
                    return HTBOTTOMLEFT;
                }
                if (mouse.x > (ww - bw)) {
                    return HTBOTTOMRIGHT;
                }
                return HTBOTTOM;
            }
            if (mouse.x < bw) {
                return HTLEFT;
            }
            if (mouse.x > (ww - bw)) {
                return HTRIGHT;
            }
            if (mouse.y < tbh) {
                return HTCAPTION;
            }
            return HTCLIENT;
        };
        *result = getHTResult(msg->hwnd, msg->lParam);
        return true;
    }
    case WM_GETMINMAXINFO: {
        // Don't cover the taskbar when maximized.
        const HMONITOR monitor =
            MonitorFromWindow(msg->hwnd, MONITOR_DEFAULTTONEAREST);
        if (monitor) {
            MONITORINFO monitorInfo;
            SecureZeroMemory(&monitorInfo, sizeof(monitorInfo));
            monitorInfo.cbSize = sizeof(monitorInfo);
            GetMonitorInfoW(monitor, &monitorInfo);
            const RECT rcWorkArea = monitorInfo.rcWork;
            const RECT rcMonitorArea = monitorInfo.rcMonitor;
            auto &mmi = *reinterpret_cast<LPMINMAXINFO>(msg->lParam);
            mmi.ptMaxPosition.x = qAbs(rcWorkArea.left - rcMonitorArea.left);
            mmi.ptMaxPosition.y = qAbs(rcWorkArea.top - rcMonitorArea.top);
            mmi.ptMaxSize.x = qAbs(rcWorkArea.right - rcWorkArea.left);
            mmi.ptMaxSize.y = qAbs(rcWorkArea.bottom - rcWorkArea.top);
            mmi.ptMaxTrackSize.x = mmi.ptMaxSize.x;
            mmi.ptMaxTrackSize.y = mmi.ptMaxSize.y;
            *result = 0;
            return true;
        }
        break;
    }
    case WM_SETICON:
    case WM_SETTEXT: {
        // Disable painting while these messages are handled to prevent them
        // from drawing a window caption over the client area, but only when
        // composition and theming are disabled. These messages don't paint
        // when composition is enabled and blocking WM_NCUAHDRAWCAPTION should
        // be enough to prevent painting when theming is enabled.
        if (!m_windowData.value(msg->hwnd).first &&
            !m_windowData.value(msg->hwnd).second) {
            const LONG_PTR oldStyle = GetWindowLongPtrW(msg->hwnd, GWL_STYLE);
            // Prevent Windows from drawing the default title bar by temporarily
            // toggling the WS_VISIBLE style.
            SetWindowLongPtrW(msg->hwnd, GWL_STYLE, oldStyle & ~WS_VISIBLE);
            const LRESULT ret = DefWindowProcW(msg->hwnd, msg->message,
                                               msg->wParam, msg->lParam);
            SetWindowLongPtrW(msg->hwnd, GWL_STYLE, oldStyle);
            *result = ret;
            return true;
        }
        break;
    }
    case WM_THEMECHANGED: {
        handleThemeChanged(msg->hwnd);
        break;
    }
    case WM_WINDOWPOSCHANGED: {
        InvalidateRect(msg->hwnd, nullptr, TRUE);
        break;
    }
    default:
        break;
    }
    return false;
}

void WinNativeEventFilter::init(HWND handle) {
    // Make sure our window is a normal application window, we'll remove the
    // window frame later in Win32 events, don't use WS_POPUP to do this.
    SetWindowLongPtrW(handle, GWL_STYLE,
                      WS_OVERLAPPEDWINDOW | WS_CLIPCHILDREN | WS_CLIPSIBLINGS);
    SetWindowLongPtrW(handle, GWL_EXSTYLE, WS_EX_APPWINDOW | WS_EX_LAYERED);
    // Make the window a layered window so the legacy GDI API can be used to
    // draw to it without messing up the area on top of the DWM frame. Note:
    // This is not necessary if other drawing APIs are used, eg. GDI+, OpenGL,
    // Direct2D, Direct3D, DirectComposition, etc.
    SetLayeredWindowAttributes(handle, RGB(255, 0, 255), 0, LWA_COLORKEY);
    // Make sure our window has the frame shadow.
    handleDwmCompositionChanged(handle);
    handleThemeChanged(handle);
    // For debug purposes.
    qDebug().noquote() << "Window handle:" << handle;
    qDebug().noquote() << "Window DPI:" << windowDpi(handle)
                       << "Window DPR:" << windowDpr(handle);
    qDebug().noquote() << "Window border width:" << borderWidth(handle)
                       << "Window border height:" << borderHeight(handle)
                       << "Window titlebar height:" << titlebarHeight(handle);
}

void WinNativeEventFilter::handleDwmCompositionChanged(HWND handle) {
    BOOL enabled = FALSE;
    DwmIsCompositionEnabled(&enabled);
    const BOOL theme = m_windowData.value(handle).second;
    m_windowData[handle] = qMakePair(enabled, theme);
    // We should not draw the frame shadow if DWM composition is disabled, in
    // other words, a window should not have frame shadow when Windows Aero is
    // not enabled.
    // Note that, start from Win8, the DWM composition is always enabled and
    // can't be disabled.
    if (enabled) {
        // The frame shadow is drawn on the non-client area and thus we have to
        // make sure the non-client area rendering is enabled first.
        const DWMNCRENDERINGPOLICY ncrp = DWMNCRP_ENABLED;
        DwmSetWindowAttribute(handle, DWMWA_NCRENDERING_POLICY, &ncrp,
                              sizeof(ncrp));
        // Negative margins have special meaning to
        // DwmExtendFrameIntoClientArea. Negative margins create the "sheet of
        // glass" effect, where the client area is rendered as a solid surface
        // with no window border.
        const MARGINS margins = {-1, -1, -1, -1};
        DwmExtendFrameIntoClientArea(handle, &margins);
    }
    // handleBlurForWindow(handle, enabled);
    refreshWindow(handle);
}

void WinNativeEventFilter::handleThemeChanged(HWND handle) {
    const BOOL dwm = m_windowData.value(handle).first;
    m_windowData[handle] = qMakePair(dwm, IsThemeActive());
}

void WinNativeEventFilter::handleBlurForWindow(HWND handle,
                                               BOOL compositionEnabled) {
    if (!handle) {
        return;
    }
    if (m_SetWindowCompositionAttribute) {
        ACCENT_POLICY accent;
        accent.AccentFlags = 0;
        accent.GradientColor = 0;
        accent.AnimationId = 0;
        WINDOWCOMPOSITIONATTRIBDATA data;
        data.dwAttribute = WCA_ACCENT_POLICY;
        data.pvAttribute = &accent;
        data.cbAttribute = sizeof(accent);
        if (compositionEnabled) {
            // Windows 10, version 1709 (10.0.16299)
            if (QOperatingSystemVersion::current() >=
                QOperatingSystemVersion(QOperatingSystemVersion::Windows, 10, 0,
                                        16299)) {
                // Acrylic
                accent.AccentState = ACCENT_ENABLE_ACRYLICBLURBEHIND;
            } else if (QOperatingSystemVersion::current() >=
                       QOperatingSystemVersion::Windows10) {
                // Blur
                accent.AccentState = ACCENT_ENABLE_BLURBEHIND;
            } else if (QOperatingSystemVersion::current() >=
                       QOperatingSystemVersion::Windows8) {
                // Transparent gradient color
                accent.AccentState = ACCENT_ENABLE_TRANSPARENTGRADIENT;
            }
        } else {
            accent.AccentState = ACCENT_DISABLED;
        }
        m_SetWindowCompositionAttribute(handle, &data);
    } else if (QOperatingSystemVersion::current() >=
               QOperatingSystemVersion::Windows7) {
        // Windows Aero
        DWM_BLURBEHIND dwmbb;
        dwmbb.dwFlags = DWM_BB_ENABLE;
        dwmbb.fEnable = compositionEnabled;
        dwmbb.hRgnBlur = nullptr;
        dwmbb.fTransitionOnMaximized = FALSE;
        DwmEnableBlurBehindWindow(handle, &dwmbb);
    }
}

UINT WinNativeEventFilter::getDpiForWindow(HWND handle) const {
    const auto getScreenDpi = [](UINT defaultValue) -> UINT {
        // Available since Windows 7.
        ID2D1Factory *m_pDirect2dFactory = nullptr;
        if (SUCCEEDED(D2D1CreateFactory(D2D1_FACTORY_TYPE_SINGLE_THREADED,
                                        &m_pDirect2dFactory)) &&
            m_pDirect2dFactory) {
            m_pDirect2dFactory->ReloadSystemMetrics();
            FLOAT dpiX = defaultValue, dpiY = defaultValue;
            m_pDirect2dFactory->GetDesktopDpi(&dpiX, &dpiY);
            // The values of *dpiX and *dpiY are identical.
            return dpiX;
        }
        // Available since Windows 2000.
        const HDC hdc = GetDC(nullptr);
        if (hdc) {
            const int dpiX = GetDeviceCaps(hdc, LOGPIXELSX);
            const int dpiY = GetDeviceCaps(hdc, LOGPIXELSY);
            ReleaseDC(nullptr, hdc);
            // The values of dpiX and dpiY are identical actually, just to
            // silence a compiler warning.
            return dpiX == dpiY ? dpiX : dpiY;
        }
        return defaultValue;
    };
    if (!handle) {
        if (m_GetSystemDpiForProcess) {
            return m_GetSystemDpiForProcess(GetCurrentProcess());
        } else if (m_GetDpiForSystem) {
            return m_GetDpiForSystem();
        } else {
            return getScreenDpi(m_defaultDPI);
        }
    }
    if (m_GetDpiForWindow) {
        return m_GetDpiForWindow(handle);
    }
    if (m_GetDpiForMonitor) {
        UINT dpiX = m_defaultDPI, dpiY = m_defaultDPI;
        m_GetDpiForMonitor(MonitorFromWindow(handle, MONITOR_DEFAULTTONEAREST),
                           MDT_EFFECTIVE_DPI, &dpiX, &dpiY);
        // The values of *dpiX and *dpiY are identical.
        return dpiX;
    }
    return getScreenDpi(m_defaultDPI);
}

qreal WinNativeEventFilter::getDprForWindow(HWND handle) const {
    return handle ? (qreal(getDpiForWindow(handle)) / qreal(m_defaultDPI))
                  : m_defaultDPR;
}

int WinNativeEventFilter::getSystemMetricsForWindow(HWND handle,
                                                    int index) const {
    if (m_GetSystemMetricsForDpi) {
        return m_GetSystemMetricsForDpi(index, getDpiForWindow(handle));
    } else {
        return GetSystemMetrics(index) * getDprForWindow(handle);
    }
}