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

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

   JUCE is an open source framework subject to commercial or open source
   licensing.

   By downloading, installing, or using the JUCE framework, or combining the
   JUCE framework with any other source code, object code, content or any other
   copyrightable work, you agree to the terms of the JUCE End User Licence
   Agreement, and all incorporated terms including the JUCE Privacy Policy and
   the JUCE Website Terms of Service, as applicable, which will bind you. If you
   do not agree to the terms of these agreements, we will not license the JUCE
   framework to you, and you must discontinue the installation or download
   process and cease use of the JUCE framework.

   JUCE End User Licence Agreement: https://juce.com/legal/juce-8-licence/
   JUCE Privacy Policy: https://juce.com/juce-privacy-policy
   JUCE Website Terms of Service: https://juce.com/juce-website-terms-of-service/

   Or:

   You may also use this code under the terms of the AGPLv3:
   https://www.gnu.org/licenses/agpl-3.0.en.html

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

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

namespace juce
{

bool juce_performDragDropFiles (const StringArray&, const bool copyFiles, bool& shouldStop);
bool juce_performDragDropText (const String&, bool& shouldStop);


//==============================================================================
class DragAndDropContainer::DragImageComponent final : public Component,
                                                       private Timer
{
public:
    DragImageComponent (const ScaledImage& im,
                        const var& desc,
                        Component* const sourceComponent,
                        const MouseInputSource* draggingSource,
                        DragAndDropContainer& ddc,
                        Point<int> offset)
        : sourceDetails (desc, sourceComponent, Point<int>()),
          image (im),
          owner (ddc),
          mouseDragSource (draggingSource->getComponentUnderMouse()),
          imageOffset (transformOffsetCoordinates (sourceComponent, offset)),
          originalInputSourceIndex (draggingSource->getIndex()),
          originalInputSourceType (draggingSource->getType())
    {
        updateSize();

        if (mouseDragSource == nullptr)
            mouseDragSource = sourceComponent;

        mouseDragSource->addMouseListener (this, false);

        startTimer (200);

        setInterceptsMouseClicks (false, false);
        setWantsKeyboardFocus (true);
        setAlwaysOnTop (true);
    }

    ~DragImageComponent() override
    {
        owner.dragImageComponents.remove (owner.dragImageComponents.indexOf (this), false);

        if (mouseDragSource != nullptr)
        {
            mouseDragSource->removeMouseListener (this);

            if (auto* current = getCurrentlyOver())
                if (current->isInterestedInDragSource (sourceDetails))
                    current->itemDragExit (sourceDetails);
        }

        owner.dragOperationEnded (sourceDetails);
    }

    void paint (Graphics& g) override
    {
        if (isOpaque())
            g.fillAll (Colours::white);

        g.setOpacity (1.0f);
        g.drawImage (image.getImage(), getLocalBounds().toFloat());
    }

    void mouseUp (const MouseEvent& e) override
    {
        if (e.originalComponent != this && isOriginalInputSource (e.source))
        {
            if (mouseDragSource != nullptr)
                mouseDragSource->removeMouseListener (this);

            // (note: use a local copy of this in case the callback runs
            // a modal loop and deletes this object before the method completes)
            auto details = sourceDetails;

            auto wasVisible = isVisible();
            setVisible (false);
            const auto [finalTarget, unused, localPosition] = findTarget (e.getScreenPosition());
            ignoreUnused (unused);
            details.localPosition = localPosition;

            if (wasVisible) // fade the component and remove it - it'll be deleted later by the timer callback
                dismissWithAnimation (finalTarget == nullptr);

            if (auto* parent = getParentComponent())
                parent->removeChildComponent (this);

            if (finalTarget != nullptr)
            {
                currentlyOverComp = nullptr;
                finalTarget->itemDropped (details);
            }

            // careful - this object could now be deleted..
        }
    }

    void mouseDrag (const MouseEvent& e) override
    {
        if (e.originalComponent != this && isOriginalInputSource (e.source))
            updateLocation (true, e.getScreenPosition());
    }

    void updateLocation (const bool canDoExternalDrag, Point<int> screenPos)
    {
        auto details = sourceDetails;

        setNewScreenPos (screenPos);

        const auto [newTarget, newTargetComp, localPosition] = findTarget (screenPos);
        details.localPosition = localPosition;

        setVisible (newTarget == nullptr || newTarget->shouldDrawDragImageWhenOver());

        maintainKeyboardFocusWhenPossible();

        if (newTargetComp != currentlyOverComp)
        {
            if (auto* lastTarget = getCurrentlyOver())
                if (details.sourceComponent != nullptr && lastTarget->isInterestedInDragSource (details))
                    lastTarget->itemDragExit (details);

            currentlyOverComp = newTargetComp;

            if (newTarget != nullptr
                  && newTarget->isInterestedInDragSource (details))
                newTarget->itemDragEnter (details);
        }

        sendDragMove (details);

        if (canDoExternalDrag)
        {
            auto now = Time::getCurrentTime();

            if (getCurrentlyOver() != nullptr)
                lastTimeOverTarget = now;
            else if (now > lastTimeOverTarget + RelativeTime::milliseconds (700))
                checkForExternalDrag (details, screenPos);
        }

        forceMouseCursorUpdate();
    }

    void updateImage (const ScaledImage& newImage)
    {
        image = newImage;
        updateSize();
        repaint();
    }

    void timerCallback() override
    {
        forceMouseCursorUpdate();

        if (sourceDetails.sourceComponent == nullptr)
        {
            deleteSelf();
        }
        else
        {
            for (auto& s : Desktop::getInstance().getMouseSources())
            {
                if (isOriginalInputSource (s) && ! s.isDragging())
                {
                    if (mouseDragSource != nullptr)
                        mouseDragSource->removeMouseListener (this);

                    deleteSelf();
                    break;
                }
            }
        }
    }

    bool keyPressed (const KeyPress& key) override
    {
        if (key == KeyPress::escapeKey)
        {
            const auto wasVisible = isVisible();
            setVisible (false);

            if (wasVisible)
                dismissWithAnimation (true);

            deleteSelf();
            return true;
        }

        return false;
    }

    bool canModalEventBeSentToComponent (const Component* targetComponent) override
    {
        return targetComponent == mouseDragSource;
    }

    // (overridden to avoid beeps when dragging)
    void inputAttemptWhenModal() override {}

    DragAndDropTarget::SourceDetails sourceDetails;

private:
    ScaledImage image;
    DragAndDropContainer& owner;
    WeakReference<Component> mouseDragSource, currentlyOverComp;
    const Point<int> imageOffset;
    bool hasCheckedForExternalDrag = false;
    Time lastTimeOverTarget;
    int originalInputSourceIndex;
    MouseInputSource::InputSourceType originalInputSourceType;
    bool canHaveKeyboardFocus = false;

    void maintainKeyboardFocusWhenPossible()
    {
        const auto newCanHaveKeyboardFocus = isVisible();

        if (std::exchange (canHaveKeyboardFocus, newCanHaveKeyboardFocus) != newCanHaveKeyboardFocus)
            if (canHaveKeyboardFocus)
                grabKeyboardFocus();
    }

    void updateSize()
    {
        const auto bounds = image.getScaledBounds().toNearestInt();
        setSize (bounds.getWidth(), bounds.getHeight());
    }

    void forceMouseCursorUpdate()
    {
        Desktop::getInstance().getMainMouseSource().forceMouseCursorUpdate();
    }

    DragAndDropTarget* getCurrentlyOver() const noexcept
    {
        return dynamic_cast<DragAndDropTarget*> (currentlyOverComp.get());
    }

    static Component* findDesktopComponentBelow (Point<int> screenPos)
    {
        auto& desktop = Desktop::getInstance();

        for (auto i = desktop.getNumComponents(); --i >= 0;)
        {
            auto* desktopComponent = desktop.getComponent (i);
            auto dPoint = desktopComponent->getLocalPoint (nullptr, screenPos);

            if (auto* c = desktopComponent->getComponentAt (dPoint))
            {
                auto cPoint = c->getLocalPoint (desktopComponent, dPoint);

                if (c->hitTest (cPoint.getX(), cPoint.getY()))
                    return c;
            }
        }

        return nullptr;
    }

    Point<int> transformOffsetCoordinates (const Component* const sourceComponent, Point<int> offsetInSource) const
    {
        return getLocalPoint (sourceComponent, offsetInSource) - getLocalPoint (sourceComponent, Point<int>());
    }

    std::tuple<DragAndDropTarget*, Component*, Point<int>> findTarget (Point<int> screenPos) const
    {
        auto* hit = getParentComponent();

        if (hit == nullptr)
            hit = findDesktopComponentBelow (screenPos);
        else
            hit = hit->getComponentAt (hit->getLocalPoint (nullptr, screenPos));

        // (note: use a local copy of this in case the callback runs
        // a modal loop and deletes this object before the method completes)
        auto details = sourceDetails;

        while (hit != nullptr)
        {
            if (auto* ddt = dynamic_cast<DragAndDropTarget*> (hit))
                if (ddt->isInterestedInDragSource (details))
                    return std::tuple (ddt, hit, hit->getLocalPoint (nullptr, screenPos));

            hit = hit->getParentComponent();
        }

        return {};
    }

    void setNewScreenPos (Point<int> screenPos)
    {
        setTopLeftPosition (std::invoke ([&]
        {
            if (auto* p = getParentComponent())
                return p->getLocalPoint (nullptr, screenPos - imageOffset);

           #if JUCE_WINDOWS
            // On Windows, the mouse position is continuous in physical pixels across screen boundaries.
            // i.e. if two screens are set to different scale factors, when the mouse moves horizontally
            // between those screens, the mouse's physical y coordinate will be preserved, and if
            // the mouse moves vertically between screens its physical x coordinate will be preserved.

            // To avoid the dragged image detaching from the mouse, compute the new top left position
            // in physical coords and then convert back to logical.
            // If we were to stay in logical coordinates the whole time, the image may detach from the
            // mouse because the mouse does not move continuously in logical coordinate space.

            const auto& displays = Desktop::getInstance().getDisplays();
            const auto physicalPos = displays.logicalToPhysical (screenPos);

            float scale = 1.0f;

            if (auto* p = getPeer())
                scale = (float) p->getPlatformScaleFactor();

            return displays.physicalToLogical (physicalPos - (imageOffset * scale));
           #else
            return screenPos - imageOffset;
           #endif
        }));
    }

    void sendDragMove (DragAndDropTarget::SourceDetails& details) const
    {
        if (auto* target = getCurrentlyOver())
            if (target->isInterestedInDragSource (details))
                target->itemDragMove (details);
    }

    void checkForExternalDrag (DragAndDropTarget::SourceDetails& details, Point<int> screenPos)
    {
        if (! hasCheckedForExternalDrag)
        {
            if (Desktop::getInstance().findComponentAt (screenPos) == nullptr)
            {
                hasCheckedForExternalDrag = true;

                if (ComponentPeer::getCurrentModifiersRealtime().isAnyMouseButtonDown())
                {
                    StringArray files;
                    auto canMoveFiles = false;

                    if (owner.shouldDropFilesWhenDraggedExternally (details, files, canMoveFiles) && ! files.isEmpty())
                    {
                        MessageManager::callAsync ([=] { DragAndDropContainer::performExternalDragDropOfFiles (files, canMoveFiles); });
                        deleteSelf();
                        return;
                    }

                    String text;

                    if (owner.shouldDropTextWhenDraggedExternally (details, text) && text.isNotEmpty())
                    {
                        MessageManager::callAsync ([=] { DragAndDropContainer::performExternalDragDropOfText (text); });
                        deleteSelf();
                        return;
                    }
                }
            }
        }
    }

    void deleteSelf()
    {
        delete this;
    }

    void dismissWithAnimation (const bool shouldSnapBack)
    {
        setVisible (true);
        auto& animator = Desktop::getInstance().getAnimator();

        if (shouldSnapBack && sourceDetails.sourceComponent != nullptr)
        {
            auto target = sourceDetails.sourceComponent->localPointToGlobal (sourceDetails.sourceComponent->getLocalBounds().getCentre());
            auto ourCentre = localPointToGlobal (getLocalBounds().getCentre());

            animator.animateComponent (this,
                                       getBounds() + (target - ourCentre),
                                       0.0f, 120,
                                       true, 1.0, 1.0);
        }
        else
        {
            animator.fadeOut (this, 120);
        }
    }

    bool isOriginalInputSource (const MouseInputSource& sourceToCheck)
    {
        return (sourceToCheck.getType() == originalInputSourceType
                && sourceToCheck.getIndex() == originalInputSourceIndex);
    }

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (DragImageComponent)
};


//==============================================================================
DragAndDropContainer::DragAndDropContainer() = default;

DragAndDropContainer::~DragAndDropContainer() = default;

void DragAndDropContainer::startDragging (const var& sourceDescription,
                                          Component* sourceComponent,
                                          const ScaledImage& dragImage,
                                          const bool allowDraggingToExternalWindows,
                                          const Point<int>* imageOffsetFromMouse,
                                          const MouseInputSource* inputSourceCausingDrag)
{
    if (isAlreadyDragging (sourceComponent))
        return;

    auto* draggingSource = getMouseInputSourceForDrag (sourceComponent, inputSourceCausingDrag);

    if (draggingSource == nullptr || ! draggingSource->isDragging())
    {
        jassertfalse;   // You must call startDragging() from within a mouseDown or mouseDrag callback!
        return;
    }

    const auto lastMouseDown = draggingSource->getLastMouseDownPosition().roundToInt();

    struct ImageAndOffset
    {
        ScaledImage image;
        Point<double> offset;
    };

    const auto imageToUse = [&]() -> ImageAndOffset
    {
        if (! dragImage.getImage().isNull())
            return { dragImage, imageOffsetFromMouse != nullptr ? dragImage.getScaledBounds().getConstrainedPoint (-imageOffsetFromMouse->toDouble())
                                                                : dragImage.getScaledBounds().getCentre() };

        const auto scaleFactor = 2.0;
        auto image = sourceComponent->createComponentSnapshot (sourceComponent->getLocalBounds(), true, (float) scaleFactor)
                                    .convertedToFormat (Image::ARGB);
        image.multiplyAllAlphas (0.6f);

        const auto relPos = sourceComponent->getLocalPoint (nullptr, lastMouseDown).toDouble();
        const auto clipped = (image.getBounds().toDouble() / scaleFactor).getConstrainedPoint (relPos);

        Image fade (Image::SingleChannel, image.getWidth(), image.getHeight(), true);
        {
            Graphics fadeContext (fade);

            ColourGradient gradient;
            gradient.isRadial = true;
            gradient.point1 = clipped.toFloat() * scaleFactor;
            gradient.point2 = gradient.point1 + Point<float> (0.0f, scaleFactor * 400.0f);
            gradient.addColour (0.0, Colours::white);
            gradient.addColour (0.375, Colours::white);
            gradient.addColour (1.0, Colours::transparentWhite);

            fadeContext.setGradientFill (gradient);
            fadeContext.fillAll();
        }

        Image composite (Image::ARGB, image.getWidth(), image.getHeight(), true);
        {
            Graphics compositeContext (composite);

            compositeContext.reduceClipRegion (fade, {});
            compositeContext.drawImageAt (image, 0, 0);
        }

        return { ScaledImage (composite, scaleFactor), clipped };
    }();

    auto* dragImageComponent = dragImageComponents.add (new DragImageComponent (imageToUse.image, sourceDescription, sourceComponent,
                                                                                draggingSource, *this, imageToUse.offset.roundToInt()));

    if (allowDraggingToExternalWindows)
    {
        if (! Desktop::canUseSemiTransparentWindows())
            dragImageComponent->setOpaque (true);

        dragImageComponent->addToDesktop (ComponentPeer::windowIgnoresMouseClicks
                                          | ComponentPeer::windowIsTemporary);
    }
    else
    {
        if (auto* thisComp = dynamic_cast<Component*> (this))
        {
            thisComp->addChildComponent (dragImageComponent);
        }
        else
        {
            jassertfalse;   // Your DragAndDropContainer needs to be a Component!
            return;
        }
    }

    dragImageComponent->sourceDetails.localPosition = sourceComponent->getLocalPoint (nullptr, lastMouseDown);
    dragImageComponent->updateLocation (false, lastMouseDown);

   #if JUCE_WINDOWS
    // Under heavy load, the layered window's paint callback can often be lost by the OS,
    // so forcing a repaint at least once makes sure that the window becomes visible..
    if (auto* peer = dragImageComponent->getPeer())
        peer->performAnyPendingRepaintsNow();
   #endif

    dragOperationStarted (dragImageComponent->sourceDetails);
}

bool DragAndDropContainer::isDragAndDropActive() const
{
    return dragImageComponents.size() > 0;
}

int DragAndDropContainer::getNumCurrentDrags() const
{
    return dragImageComponents.size();
}

var DragAndDropContainer::getCurrentDragDescription() const
{
    // If you are performing drag and drop in a multi-touch environment then
    // you should use the getDragDescriptionForIndex() method instead!
    jassert (dragImageComponents.size() < 2);

    return dragImageComponents.size() != 0 ? dragImageComponents[0]->sourceDetails.description
                                           : var();
}

var DragAndDropContainer::getDragDescriptionForIndex (int index) const
{
    if (! isPositiveAndBelow (index, dragImageComponents.size()))
        return {};

    return dragImageComponents.getUnchecked (index)->sourceDetails.description;
}

void DragAndDropContainer::setCurrentDragImage (const ScaledImage& newImage)
{
    // If you are performing drag and drop in a multi-touch environment then
    // you should use the setDragImageForIndex() method instead!
    jassert (dragImageComponents.size() < 2);

    dragImageComponents[0]->updateImage (newImage);
}

void DragAndDropContainer::setDragImageForIndex (int index, const ScaledImage& newImage)
{
    if (isPositiveAndBelow (index, dragImageComponents.size()))
        dragImageComponents.getUnchecked (index)->updateImage (newImage);
}

DragAndDropContainer* DragAndDropContainer::findParentDragContainerFor (Component* c)
{
    return c != nullptr ? c->findParentComponentOfClass<DragAndDropContainer>() : nullptr;
}

bool DragAndDropContainer::shouldDropFilesWhenDraggedExternally (const DragAndDropTarget::SourceDetails&, StringArray&, bool&)
{
    return false;
}

bool DragAndDropContainer::shouldDropTextWhenDraggedExternally (const DragAndDropTarget::SourceDetails&, String&)
{
    return false;
}

void DragAndDropContainer::dragOperationStarted (const DragAndDropTarget::SourceDetails&)  {}
void DragAndDropContainer::dragOperationEnded (const DragAndDropTarget::SourceDetails&)    {}

const MouseInputSource* DragAndDropContainer::getMouseInputSourceForDrag (Component* sourceComponent,
                                                                          const MouseInputSource* inputSourceCausingDrag)
{
    if (inputSourceCausingDrag == nullptr)
    {
        auto minDistance = std::numeric_limits<float>::max();
        auto& desktop = Desktop::getInstance();

        auto centrePoint = sourceComponent ? sourceComponent->getScreenBounds().getCentre().toFloat() : Point<float>();
        auto numDragging = desktop.getNumDraggingMouseSources();

        for (auto i = 0; i < numDragging; ++i)
        {
            if (auto* ms = desktop.getDraggingMouseSource (i))
            {
                auto distance =  ms->getScreenPosition().getDistanceSquaredFrom (centrePoint);

                if (distance < minDistance)
                {
                    minDistance = distance;
                    inputSourceCausingDrag = ms;
                }
            }
        }
    }

    // You must call startDragging() from within a mouseDown or mouseDrag callback!
    jassert (inputSourceCausingDrag != nullptr && inputSourceCausingDrag->isDragging());

    return inputSourceCausingDrag;
}

bool DragAndDropContainer::isAlreadyDragging (Component* component) const noexcept
{
    for (auto* dragImageComp : dragImageComponents)
    {
        if (dragImageComp->sourceDetails.sourceComponent == component)
            return true;
    }

    return false;
}

//==============================================================================
DragAndDropTarget::SourceDetails::SourceDetails (const var& desc, Component* comp, Point<int> pos) noexcept
    : description (desc),
      sourceComponent (comp),
      localPosition (pos)
{
}

void DragAndDropTarget::itemDragEnter (const SourceDetails&)  {}
void DragAndDropTarget::itemDragMove  (const SourceDetails&)  {}
void DragAndDropTarget::itemDragExit  (const SourceDetails&)  {}
bool DragAndDropTarget::shouldDrawDragImageWhenOver()         { return true; }

//==============================================================================
void FileDragAndDropTarget::fileDragEnter (const StringArray&, int, int)  {}
void FileDragAndDropTarget::fileDragMove  (const StringArray&, int, int)  {}
void FileDragAndDropTarget::fileDragExit  (const StringArray&)            {}

void TextDragAndDropTarget::textDragEnter (const String&, int, int)  {}
void TextDragAndDropTarget::textDragMove  (const String&, int, int)  {}
void TextDragAndDropTarget::textDragExit  (const String&)            {}

} // namespace juce
