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

   This file is part of the JUCE 6 technical preview.
   Copyright (c) 2020 - Raw Material Software Limited

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

   For this technical preview, this file is not subject to commercial licensing.

   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
{

struct NSViewResizeWatcher
{
    NSViewResizeWatcher() : callback (nil) {}

    virtual ~NSViewResizeWatcher()
    {
        // must call detachViewWatcher() first
        jassert (callback == nil);
    }

    void attachViewWatcher (NSView* view)
    {
        static ViewFrameChangeCallbackClass cls;
        callback = [cls.createInstance() init];
        ViewFrameChangeCallbackClass::setTarget (callback, this);

        [[NSNotificationCenter defaultCenter]  addObserver: callback
                                                  selector: @selector (frameChanged:)
                                                      name: NSViewFrameDidChangeNotification
                                                    object: view];
    }

    void detachViewWatcher()
    {
        if (callback != nil)
        {
            [[NSNotificationCenter defaultCenter] removeObserver: callback];
            [callback release];
            callback = nil;
        }
    }

    virtual void viewResized() = 0;

private:
    id callback;

    //==============================================================================
    struct ViewFrameChangeCallbackClass   : public ObjCClass<NSObject>
    {
        ViewFrameChangeCallbackClass()  : ObjCClass<NSObject> ("JUCE_NSViewCallback_")
        {
            addIvar<NSViewResizeWatcher*> ("target");
            addMethod (@selector (frameChanged:),  frameChanged, "v@:@");
            registerClass();
        }

        static void setTarget (id self, NSViewResizeWatcher* c)
        {
            object_setInstanceVariable (self, "target", c);
        }

    private:
        static void frameChanged (id self, SEL, NSNotification*)
        {
            if (auto* target = getIvar<NSViewResizeWatcher*> (self, "target"))
                target->viewResized();
        }

        JUCE_DECLARE_NON_COPYABLE (ViewFrameChangeCallbackClass)
    };

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (NSViewResizeWatcher)
};

//==============================================================================
class NSViewAttachment  : public ReferenceCountedObject,
                          public ComponentMovementWatcher,
                          private NSViewResizeWatcher
{
public:
    NSViewAttachment (NSView* v, Component& comp)
        : ComponentMovementWatcher (&comp),
          view (v), owner (comp),
          currentPeer (nullptr)
    {
        [view retain];
        [view setPostsFrameChangedNotifications: YES];
        updateAlpha();

        if (owner.isShowing())
            componentPeerChanged();

        attachViewWatcher (view);
    }

    ~NSViewAttachment() override
    {
        detachViewWatcher();
        removeFromParent();
        [view release];
    }

    void componentMovedOrResized (Component& comp, bool wasMoved, bool wasResized) override
    {
        ComponentMovementWatcher::componentMovedOrResized (comp, wasMoved, wasResized);

        // The ComponentMovementWatcher version of this method avoids calling
        // us when the top-level comp is resized, but for an NSView we need to know this
        // because with inverted coordinates, we need to update the position even if the
        // top-left pos hasn't changed
        if (comp.isOnDesktop() && wasResized)
            componentMovedOrResized (wasMoved, wasResized);
    }

    void componentMovedOrResized (bool /*wasMoved*/, bool /*wasResized*/) override
    {
        if (auto* peer = owner.getTopLevelComponent()->getPeer())
        {
            auto r = makeNSRect (peer->getAreaCoveredBy (owner));
            r.origin.y = [[view superview] frame].size.height - (r.origin.y + r.size.height);
            [view setFrame: r];
        }
    }

    void componentPeerChanged() override
    {
        auto* peer = owner.getPeer();

        if (currentPeer != peer)
        {
            currentPeer = peer;

            if (peer != nullptr)
            {
                auto peerView = (NSView*) peer->getNativeHandle();
                [peerView addSubview: view];
                componentMovedOrResized (false, false);
            }
            else
            {
                removeFromParent();
            }
        }

        [view setHidden: ! owner.isShowing()];
    }

    void componentVisibilityChanged() override
    {
        componentPeerChanged();
    }

    void viewResized() override
    {
        owner.childBoundsChanged (nullptr);
    }

    void updateAlpha()
    {
        [view setAlphaValue: (CGFloat) owner.getAlpha()];
    }

    NSView* const view;

    using Ptr = ReferenceCountedObjectPtr<NSViewAttachment>;

private:
    Component& owner;
    ComponentPeer* currentPeer;

    void removeFromParent()
    {
        if ([view superview] != nil)
            [view removeFromSuperview]; // Must be careful not to call this unless it's required - e.g. some Apple AU views
                                        // override the call and use it as a sign that they're being deleted, which breaks everything..
    }

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (NSViewAttachment)
};

//==============================================================================
NSViewComponent::NSViewComponent() {}
NSViewComponent::~NSViewComponent() {}

void NSViewComponent::setView (void* view)
{
    if (view != getView())
    {
        auto old = attachment;

        attachment = nullptr;

        if (view != nullptr)
            attachment = attachViewToComponent (*this, view);

        old = nullptr;
    }
}

void* NSViewComponent::getView() const
{
    return attachment != nullptr ? static_cast<NSViewAttachment*> (attachment.get())->view
                                 : nullptr;
}

void NSViewComponent::resizeToFitView()
{
    if (attachment != nullptr)
    {
        auto r = [static_cast<NSViewAttachment*> (attachment.get())->view frame];
        setBounds (Rectangle<int> ((int) r.size.width, (int) r.size.height));
    }
}

void NSViewComponent::paint (Graphics&) {}

void NSViewComponent::alphaChanged()
{
    if (attachment != nullptr)
        (static_cast<NSViewAttachment*> (attachment.get()))->updateAlpha();
}

ReferenceCountedObject* NSViewComponent::attachViewToComponent (Component& comp, void* view)
{
    return new NSViewAttachment ((NSView*) view, comp);
}

} // namespace juce