/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2020 - Raw Material Software Limited

   JUCE is an open source library subject to commercial or open-source
   licensing.

   By using JUCE, you agree to the terms of both the JUCE 6 End-User License
   Agreement and JUCE Privacy Policy (both effective as of the 16th June 2020).

   End User License Agreement: www.juce.com/juce-6-licence
   Privacy Policy: www.juce.com/juce-privacy-policy

   Or: You may also use this code under the terms of the GPL v3 (see
   www.gnu.org/licenses).

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

bool juce_handleXEmbedEvent (ComponentPeer*, void*);
Window juce_getCurrentFocusWindow (ComponentPeer*);

//==============================================================================
::Window juce_createKeyProxyWindow (ComponentPeer*);
void juce_deleteKeyProxyWindow (::Window);

//==============================================================================
enum
{
    maxXEmbedVersionToSupport = 0
};

enum
{
    XEMBED_MAPPED  = (1<<0)
};

enum
{
    XEMBED_EMBEDDED_NOTIFY        = 0,
    XEMBED_WINDOW_ACTIVATE        = 1,
    XEMBED_WINDOW_DEACTIVATE      = 2,
    XEMBED_REQUEST_FOCUS          = 3,
    XEMBED_FOCUS_IN               = 4,
    XEMBED_FOCUS_OUT              = 5,
    XEMBED_FOCUS_NEXT             = 6,
    XEMBED_FOCUS_PREV             = 7,
    XEMBED_MODALITY_ON            = 10,
    XEMBED_MODALITY_OFF           = 11,
    XEMBED_REGISTER_ACCELERATOR   = 12,
    XEMBED_UNREGISTER_ACCELERATOR = 13,
    XEMBED_ACTIVATE_ACCELERATOR   = 14
};

enum
{
    XEMBED_FOCUS_CURRENT = 0,
    XEMBED_FOCUS_FIRST   = 1,
    XEMBED_FOCUS_LAST    = 2
};

//==============================================================================
class XEmbedComponent::Pimpl  : private ComponentListener
{
public:
    //==============================================================================
    struct SharedKeyWindow : public ReferenceCountedObject
    {
        SharedKeyWindow (ComponentPeer* peerToUse)
            : keyPeer (peerToUse),
              keyProxy (juce_createKeyProxyWindow (keyPeer))
        {}

        ~SharedKeyWindow()
        {
            juce_deleteKeyProxyWindow (keyProxy);

            auto& keyWindows = getKeyWindows();
            keyWindows.remove (keyPeer);
        }

        using Ptr = ReferenceCountedObjectPtr<SharedKeyWindow>;

        //==============================================================================
        Window getHandle()    { return keyProxy; }

        static Window getCurrentFocusWindow (ComponentPeer* peerToLookFor)
        {
            auto& keyWindows = getKeyWindows();

            if (peerToLookFor != nullptr)
                if (auto* foundKeyWindow = keyWindows[peerToLookFor])
                    return foundKeyWindow->keyProxy;

            return {};
        }

        static SharedKeyWindow::Ptr getKeyWindowForPeer (ComponentPeer* peerToLookFor)
        {
            jassert (peerToLookFor != nullptr);

            auto& keyWindows = getKeyWindows();
            auto foundKeyWindow = keyWindows[peerToLookFor];

            if (foundKeyWindow == nullptr)
            {
                foundKeyWindow = new SharedKeyWindow (peerToLookFor);
                keyWindows.set (peerToLookFor, foundKeyWindow);
            }

            return foundKeyWindow;
        }

    private:
        //==============================================================================
        ComponentPeer* keyPeer;
        Window keyProxy;

        static HashMap<ComponentPeer*, SharedKeyWindow*>& getKeyWindows()
        {
            // store a weak reference to the shared key windows
            static HashMap<ComponentPeer*, SharedKeyWindow*> keyWindows;
            return keyWindows;
        }
    };

public:
    //==============================================================================
    Pimpl (XEmbedComponent& parent, Window x11Window,
           bool wantsKeyboardFocus, bool isClientInitiated, bool shouldAllowResize)
        : owner (parent),
          infoAtom (XWindowSystem::getInstance()->getAtoms().XembedInfo),
          messageTypeAtom (XWindowSystem::getInstance()->getAtoms().XembedMsgType),
          clientInitiated (isClientInitiated),
          wantsFocus (wantsKeyboardFocus),
          allowResize (shouldAllowResize)
    {
        getWidgets().add (this);

        createHostWindow();

        if (clientInitiated)
            setClient (x11Window, true);

        owner.setWantsKeyboardFocus (wantsFocus);
        owner.addComponentListener (this);
    }

    ~Pimpl() override
    {
        owner.removeComponentListener (this);
        setClient (0, true);

        if (host != 0)
        {
            auto dpy = getDisplay();

            X11Symbols::getInstance()->xDestroyWindow (dpy, host);
            X11Symbols::getInstance()->xSync (dpy, false);

            auto mask = NoEventMask | KeyPressMask | KeyReleaseMask
                      | EnterWindowMask | LeaveWindowMask | PointerMotionMask
                      | KeymapStateMask | ExposureMask | StructureNotifyMask
                      | FocusChangeMask;

            XEvent event;
            while (X11Symbols::getInstance()->xCheckWindowEvent (dpy, host, mask, &event) == True)
            {}

            host = 0;
        }

        getWidgets().removeAllInstancesOf (this);
    }

    //==============================================================================
    void setClient (Window xembedClient, bool shouldReparent)
    {
        removeClient();

        if (xembedClient != 0)
        {
            auto dpy = getDisplay();

            client = xembedClient;

            // if the client has initiated the component then keep the clients size
            // otherwise the client should use the host's window' size
            if (clientInitiated)
            {
                configureNotify();
            }
            else
            {
                auto newBounds = getX11BoundsFromJuce();
                X11Symbols::getInstance()->xResizeWindow (dpy, client, static_cast<unsigned int> (newBounds.getWidth()),
                                                          static_cast<unsigned int> (newBounds.getHeight()));
            }

            auto eventMask = StructureNotifyMask | PropertyChangeMask | FocusChangeMask;

            XWindowAttributes clientAttr;
            X11Symbols::getInstance()->xGetWindowAttributes (dpy, client, &clientAttr);

            if ((eventMask & clientAttr.your_event_mask) != eventMask)
                X11Symbols::getInstance()->xSelectInput (dpy, client, clientAttr.your_event_mask | eventMask);

            getXEmbedMappedFlag();

            if (shouldReparent)
                X11Symbols::getInstance()->xReparentWindow (dpy, client, host, 0, 0);

            if (supportsXembed)
                sendXEmbedEvent (CurrentTime, XEMBED_EMBEDDED_NOTIFY, 0, (long) host, xembedVersion);

            updateMapping();
        }
    }

    void focusGained (FocusChangeType changeType)
    {
        if (client != 0 && supportsXembed && wantsFocus)
        {
            updateKeyFocus();
            sendXEmbedEvent (CurrentTime, XEMBED_FOCUS_IN,
                             (changeType == focusChangedByTabKey ? XEMBED_FOCUS_FIRST : XEMBED_FOCUS_CURRENT));
        }
    }

    void focusLost (FocusChangeType)
    {
        if (client != 0 && supportsXembed && wantsFocus)
        {
            sendXEmbedEvent (CurrentTime, XEMBED_FOCUS_OUT);
            updateKeyFocus();
        }
    }

    void broughtToFront()
    {
        if (client != 0 && supportsXembed)
            sendXEmbedEvent (CurrentTime, XEMBED_WINDOW_ACTIVATE);
    }

    unsigned long getHostWindowID()
    {
        // You are using the client initiated version of the protocol. You cannot
        // retrieve the window id of the host. Please read the documentation for
        // the XEmebedComponent class.
        jassert (! clientInitiated);

        return host;
    }

private:
    //==============================================================================
    XEmbedComponent& owner;
    Window client = 0, host = 0;
    Atom infoAtom, messageTypeAtom;

    bool clientInitiated;
    bool wantsFocus        = false;
    bool allowResize       = false;
    bool supportsXembed    = false;
    bool hasBeenMapped     = false;
    int xembedVersion      = maxXEmbedVersionToSupport;

    ComponentPeer* lastPeer = nullptr;
    SharedKeyWindow::Ptr keyWindow;

    //==============================================================================
    void componentParentHierarchyChanged (Component&) override   { peerChanged (owner.getPeer()); }
    void componentMovedOrResized (Component&, bool, bool) override
    {
        if (host != 0 && lastPeer != nullptr)
        {
            auto dpy = getDisplay();
            auto newBounds = getX11BoundsFromJuce();
            XWindowAttributes attr;

            if (X11Symbols::getInstance()->xGetWindowAttributes (dpy, host, &attr))
            {
                Rectangle<int> currentBounds (attr.x, attr.y, attr.width, attr.height);
                if (currentBounds != newBounds)
                {
                    X11Symbols::getInstance()->xMoveResizeWindow (dpy, host, newBounds.getX(), newBounds.getY(),
                                                                  static_cast<unsigned int> (newBounds.getWidth()),
                                                                  static_cast<unsigned int> (newBounds.getHeight()));
                }
            }

            if (client != 0 && X11Symbols::getInstance()->xGetWindowAttributes (dpy, client, &attr))
            {
                Rectangle<int> currentBounds (attr.x, attr.y, attr.width, attr.height);

                if ((currentBounds.getWidth() != newBounds.getWidth()
                     || currentBounds.getHeight() != newBounds.getHeight()))
                {
                    X11Symbols::getInstance()->xMoveResizeWindow (dpy, client, 0, 0,
                                                                  static_cast<unsigned int> (newBounds.getWidth()),
                                                                  static_cast<unsigned int> (newBounds.getHeight()));
                }
            }
        }
    }

    //==============================================================================
    void createHostWindow()
    {
        auto dpy = getDisplay();
        int defaultScreen = X11Symbols::getInstance()->xDefaultScreen (dpy);
        Window root = X11Symbols::getInstance()->xRootWindow (dpy, defaultScreen);

        XSetWindowAttributes swa;
        swa.border_pixel = 0;
        swa.background_pixmap = None;
        swa.override_redirect = True;
        swa.event_mask = SubstructureNotifyMask | StructureNotifyMask | FocusChangeMask;

        host = X11Symbols::getInstance()->xCreateWindow (dpy, root, 0, 0, 1, 1, 0, CopyFromParent,
                                                         InputOutput, CopyFromParent,
                                                         CWEventMask | CWBorderPixel | CWBackPixmap | CWOverrideRedirect,
                                                         &swa);
    }

    void removeClient()
    {
        if (client != 0)
        {
            auto dpy = getDisplay();
            X11Symbols::getInstance()->xSelectInput (dpy, client, 0);

            keyWindow = nullptr;

            int defaultScreen = X11Symbols::getInstance()->xDefaultScreen (dpy);
            Window root = X11Symbols::getInstance()->xRootWindow (dpy, defaultScreen);

            if (hasBeenMapped)
            {
                X11Symbols::getInstance()->xUnmapWindow (dpy, client);
                hasBeenMapped = false;
            }

            X11Symbols::getInstance()->xReparentWindow (dpy, client, root, 0, 0);
            client = 0;

            X11Symbols::getInstance()->xSync (dpy, False);
        }
    }

    void updateMapping()
    {
        if (client != 0)
        {
            const bool shouldBeMapped = getXEmbedMappedFlag();

            if (shouldBeMapped != hasBeenMapped)
            {
                hasBeenMapped = shouldBeMapped;

                if (shouldBeMapped)
                    X11Symbols::getInstance()->xMapWindow (getDisplay(), client);
                else
                    X11Symbols::getInstance()->xUnmapWindow (getDisplay(), client);
            }
        }
    }

    Window getParentX11Window()
    {
        if (auto* peer = owner.getPeer())
            return reinterpret_cast<Window> (peer->getNativeHandle());

        return {};
    }

    Display* getDisplay()   { return XWindowSystem::getInstance()->getDisplay(); }

    //==============================================================================
    bool getXEmbedMappedFlag()
    {
        XWindowSystemUtilities::GetXProperty embedInfo (client, infoAtom, 0, 2, false, infoAtom);

        if (embedInfo.success && embedInfo.actualFormat == 32
             && embedInfo.numItems >= 2 && embedInfo.data != nullptr)
        {
            long version;
            memcpy (&version, embedInfo.data, sizeof (long));

            supportsXembed = true;
            xembedVersion = jmin ((int) maxXEmbedVersionToSupport, (int) version);

            long flags;
            memcpy (&flags, embedInfo.data + sizeof (long), sizeof (long));

            return ((flags & XEMBED_MAPPED) != 0);
        }
        else
        {
            supportsXembed = false;
            xembedVersion = maxXEmbedVersionToSupport;
        }

        return true;
    }

    //==============================================================================
    void propertyChanged (const Atom& a)
    {
        if (a == infoAtom)
            updateMapping();
    }

    void configureNotify()
    {
        XWindowAttributes attr;
        auto dpy = getDisplay();

        if (X11Symbols::getInstance()->xGetWindowAttributes (dpy, client, &attr))
        {
            XWindowAttributes hostAttr;

            if (X11Symbols::getInstance()->xGetWindowAttributes (dpy, host, &hostAttr))
                if (attr.width != hostAttr.width || attr.height != hostAttr.height)
                    X11Symbols::getInstance()->xResizeWindow (dpy, host, (unsigned int) attr.width, (unsigned int) attr.height);

            // as the client window is not on any screen yet, we need to guess
            // on which screen it might appear to get a scaling factor :-(
            auto& displays = Desktop::getInstance().getDisplays();
            auto* peer = owner.getPeer();
            const double scale = (peer != nullptr ? peer->getPlatformScaleFactor()
                                                  : displays.getMainDisplay().scale);

            Point<int> topLeftInPeer
                = (peer != nullptr ? peer->getComponent().getLocalPoint (&owner, Point<int> (0, 0))
                   : owner.getBounds().getTopLeft());

            Rectangle<int> newBounds (topLeftInPeer.getX(), topLeftInPeer.getY(),
                                      static_cast<int> (static_cast<double> (attr.width)  / scale),
                                      static_cast<int> (static_cast<double> (attr.height) / scale));


            if (peer != nullptr)
                newBounds = owner.getLocalArea (&peer->getComponent(), newBounds);

            jassert (newBounds.getX() == 0 && newBounds.getY() == 0);

            if (newBounds != owner.getLocalBounds())
                owner.setSize (newBounds.getWidth(), newBounds.getHeight());
        }
    }

    void peerChanged (ComponentPeer* newPeer)
    {
        if (newPeer != lastPeer)
        {
            if (lastPeer != nullptr)
                keyWindow = nullptr;

            auto dpy = getDisplay();
            Window rootWindow = X11Symbols::getInstance()->xRootWindow (dpy, DefaultScreen (dpy));
            Rectangle<int> newBounds = getX11BoundsFromJuce();

            if (newPeer == nullptr)
                X11Symbols::getInstance()->xUnmapWindow (dpy, host);

            Window newParent = (newPeer != nullptr ? getParentX11Window() : rootWindow);
            X11Symbols::getInstance()->xReparentWindow (dpy, host, newParent, newBounds.getX(), newBounds.getY());

            lastPeer = newPeer;

            if (newPeer != nullptr)
            {
                if (wantsFocus)
                {
                    keyWindow = SharedKeyWindow::getKeyWindowForPeer (newPeer);
                    updateKeyFocus();
                }

                componentMovedOrResized (owner, true, true);
                X11Symbols::getInstance()->xMapWindow (dpy, host);

                broughtToFront();
            }
        }
    }

    void updateKeyFocus()
    {
        if (lastPeer != nullptr && lastPeer->isFocused())
            X11Symbols::getInstance()->xSetInputFocus (getDisplay(), getCurrentFocusWindow (lastPeer), RevertToParent, CurrentTime);
    }

    //==============================================================================
    void handleXembedCmd (const ::Time& /*xTime*/, long opcode, long /*detail*/, long /*data1*/, long /*data2*/)
    {
        switch (opcode)
        {
            case XEMBED_REQUEST_FOCUS:
                if (wantsFocus)
                    owner.grabKeyboardFocus();
                break;

            case XEMBED_FOCUS_NEXT:
                if (wantsFocus)
                    owner.moveKeyboardFocusToSibling (true);
                break;

            case XEMBED_FOCUS_PREV:
                if (wantsFocus)
                    owner.moveKeyboardFocusToSibling (false);
                break;

            default:
                break;
        }
    }

    bool handleX11Event (const XEvent& e)
    {
        if (e.xany.window == client && client != 0)
        {
            switch (e.type)
            {
                case PropertyNotify:
                    propertyChanged (e.xproperty.atom);
                    return true;

                case ConfigureNotify:
                    if (allowResize)
                        configureNotify();
                    else
                        MessageManager::callAsync ([this] {componentMovedOrResized (owner, true, true);});

                    return true;

                default:
                    break;
            }
        }
        else if (e.xany.window == host && host != 0)
        {
            switch (e.type)
            {
                case ReparentNotify:
                    if (e.xreparent.parent == host && e.xreparent.window != client)
                    {
                        setClient (e.xreparent.window, false);
                        return true;
                    }
                    break;

                case CreateNotify:
                    if (e.xcreatewindow.parent != e.xcreatewindow.window && e.xcreatewindow.parent == host && e.xcreatewindow.window != client)
                    {
                        setClient (e.xcreatewindow.window, false);
                        return true;
                    }
                    break;

                case GravityNotify:
                    componentMovedOrResized (owner, true, true);
                    return true;

                case ClientMessage:
                    if (e.xclient.message_type == messageTypeAtom && e.xclient.format == 32)
                    {
                        handleXembedCmd ((::Time) e.xclient.data.l[0], e.xclient.data.l[1],
                                         e.xclient.data.l[2], e.xclient.data.l[3],
                                         e.xclient.data.l[4]);

                        return true;
                    }
                    break;

                default:
                    break;
            }
        }

        return false;
    }

    void sendXEmbedEvent (const ::Time& xTime, long opcode,
                          long opcodeMinor = 0, long data1 = 0, long data2 = 0)
    {
        XClientMessageEvent msg;
        auto dpy = getDisplay();

        ::memset (&msg, 0, sizeof (XClientMessageEvent));
        msg.window = client;
        msg.type = ClientMessage;
        msg.message_type = messageTypeAtom;
        msg.format = 32;
        msg.data.l[0] = (long) xTime;
        msg.data.l[1] = opcode;
        msg.data.l[2] = opcodeMinor;
        msg.data.l[3] = data1;
        msg.data.l[4] = data2;

        X11Symbols::getInstance()->xSendEvent (dpy, client, False, NoEventMask, (XEvent*) &msg);
        X11Symbols::getInstance()->xSync (dpy, False);
    }

    Rectangle<int> getX11BoundsFromJuce()
    {
        if (auto* peer = owner.getPeer())
        {
            auto r = peer->getComponent().getLocalArea (&owner, owner.getLocalBounds());
            return r * peer->getPlatformScaleFactor();
        }

        return owner.getLocalBounds();
    }

    //==============================================================================
    friend bool juce::juce_handleXEmbedEvent (ComponentPeer*, void*);
    friend unsigned long juce::juce_getCurrentFocusWindow (ComponentPeer*);

    static Array<Pimpl*>& getWidgets()
    {
        static Array<Pimpl*> i;
        return i;
    }

    static bool dispatchX11Event (ComponentPeer* p, const XEvent* eventArg)
    {
        if (eventArg != nullptr)
        {
            auto& e = *eventArg;

            if (auto w = e.xany.window)
                for (auto* widget : getWidgets())
                    if (w == widget->host || w == widget->client)
                        return widget->handleX11Event (e);
        }
        else
        {
            for (auto* widget : getWidgets())
                if (widget->owner.getPeer() == p)
                    widget->peerChanged (nullptr);
        }

        return false;
    }

    static Window getCurrentFocusWindow (ComponentPeer* p)
    {
        if (p != nullptr)
        {
            for (auto* widget : getWidgets())
                if (widget->owner.getPeer() == p && widget->owner.hasKeyboardFocus (false))
                    return widget->client;
        }

        return SharedKeyWindow::getCurrentFocusWindow (p);
    }
};

//==============================================================================
XEmbedComponent::XEmbedComponent (bool wantsKeyboardFocus, bool allowForeignWidgetToResizeComponent)
    : pimpl (new Pimpl (*this, 0, wantsKeyboardFocus, false, allowForeignWidgetToResizeComponent))
{
    setOpaque (true);
}

XEmbedComponent::XEmbedComponent (unsigned long wID, bool wantsKeyboardFocus, bool allowForeignWidgetToResizeComponent)
    : pimpl (new Pimpl (*this, wID, wantsKeyboardFocus, true, allowForeignWidgetToResizeComponent))
{
    setOpaque (true);
}

XEmbedComponent::~XEmbedComponent() {}

void XEmbedComponent::paint (Graphics& g)
{
    g.fillAll (Colours::lightgrey);
}

void XEmbedComponent::focusGained (FocusChangeType changeType)     { pimpl->focusGained (changeType); }
void XEmbedComponent::focusLost   (FocusChangeType changeType)     { pimpl->focusLost   (changeType); }
void XEmbedComponent::broughtToFront()                             { pimpl->broughtToFront(); }
unsigned long XEmbedComponent::getHostWindowID()                   { return pimpl->getHostWindowID(); }
void XEmbedComponent::removeClient()                               { pimpl->setClient (0, true); }

//==============================================================================
bool juce_handleXEmbedEvent (ComponentPeer* p, void* e)
{
    return XEmbedComponent::Pimpl::dispatchX11Event (p, reinterpret_cast<const XEvent*> (e));
}

unsigned long juce_getCurrentFocusWindow (ComponentPeer* peer)
{
    return (unsigned long) XEmbedComponent::Pimpl::getCurrentFocusWindow (peer);
}

} // namespace juce