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

   This file is part of the JUCE 6 technical preview.
   Copyright (c) 2017 - ROLI Ltd.

   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
{

class ComponentAnimator::AnimationTask
{
public:
    AnimationTask (Component* c) noexcept  : component (c) {}

    ~AnimationTask()
    {
        proxy.deleteAndZero();
    }

    void reset (const Rectangle<int>& finalBounds,
                float finalAlpha,
                int millisecondsToSpendMoving,
                bool useProxyComponent,
                double startSpd, double endSpd)
    {
        msElapsed = 0;
        msTotal = jmax (1, millisecondsToSpendMoving);
        lastProgress = 0;
        destination = finalBounds;
        destAlpha = finalAlpha;

        isMoving = (finalBounds != component->getBounds());
        isChangingAlpha = (finalAlpha != component->getAlpha());

        left    = component->getX();
        top     = component->getY();
        right   = component->getRight();
        bottom  = component->getBottom();
        alpha   = component->getAlpha();

        const double invTotalDistance = 4.0 / (startSpd + endSpd + 2.0);
        startSpeed = jmax (0.0, startSpd * invTotalDistance);
        midSpeed = invTotalDistance;
        endSpeed = jmax (0.0, endSpd * invTotalDistance);

        proxy.deleteAndZero();

        if (useProxyComponent)
            proxy = new ProxyComponent (*component);

        component->setVisible (! useProxyComponent);
    }

    bool useTimeslice (const int elapsed)
    {
        if (auto* c = proxy != nullptr ? proxy.getComponent()
                                       : component.get())
        {
            msElapsed += elapsed;
            double newProgress = msElapsed / (double) msTotal;

            if (newProgress >= 0 && newProgress < 1.0)
            {
                const WeakReference<AnimationTask> weakRef (this);
                newProgress = timeToDistance (newProgress);
                const double delta = (newProgress - lastProgress) / (1.0 - lastProgress);
                jassert (newProgress >= lastProgress);
                lastProgress = newProgress;

                if (delta < 1.0)
                {
                    bool stillBusy = false;

                    if (isMoving)
                    {
                        left   += (destination.getX()      - left)   * delta;
                        top    += (destination.getY()      - top)    * delta;
                        right  += (destination.getRight()  - right)  * delta;
                        bottom += (destination.getBottom() - bottom) * delta;

                        const Rectangle<int> newBounds (roundToInt (left),
                                                        roundToInt (top),
                                                        roundToInt (right - left),
                                                        roundToInt (bottom - top));

                        if (newBounds != destination)
                        {
                            c->setBounds (newBounds);
                            stillBusy = true;
                        }
                    }

                    // Check whether the animation was cancelled/deleted during
                    // a callback during the setBounds method
                    if (weakRef.wasObjectDeleted())
                        return false;

                    if (isChangingAlpha)
                    {
                        alpha += (destAlpha - alpha) * delta;
                        c->setAlpha ((float) alpha);
                        stillBusy = true;
                    }

                    if (stillBusy)
                        return true;
                }
            }
        }

        moveToFinalDestination();
        return false;
    }

    void moveToFinalDestination()
    {
        if (component != nullptr)
        {
            const WeakReference<AnimationTask> weakRef (this);
            component->setAlpha ((float) destAlpha);
            component->setBounds (destination);

            if (! weakRef.wasObjectDeleted())
                if (proxy != nullptr)
                    component->setVisible (destAlpha > 0);
        }
    }

    //==============================================================================
    struct ProxyComponent  : public Component
    {
        ProxyComponent (Component& c)
        {
            setWantsKeyboardFocus (false);
            setBounds (c.getBounds());
            setTransform (c.getTransform());
            setAlpha (c.getAlpha());
            setInterceptsMouseClicks (false, false);

            if (auto* parent = c.getParentComponent())
                parent->addAndMakeVisible (this);
            else if (c.isOnDesktop() && c.getPeer() != nullptr)
                addToDesktop (c.getPeer()->getStyleFlags() | ComponentPeer::windowIgnoresKeyPresses);
            else
                jassertfalse; // seem to be trying to animate a component that's not visible..

            auto scale = (float) Desktop::getInstance().getDisplays().findDisplayForRect (getScreenBounds()).scale
                           * Component::getApproximateScaleFactorForComponent (&c);

            image = c.createComponentSnapshot (c.getLocalBounds(), false, scale);

            setVisible (true);
            toBehind (&c);
        }

        void paint (Graphics& g) override
        {
            g.setOpacity (1.0f);
            g.drawImageTransformed (image, AffineTransform::scale (getWidth()  / (float) jmax (1, image.getWidth()),
                                                                   getHeight() / (float) jmax (1, image.getHeight())), false);
        }

    private:
        Image image;

        JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (ProxyComponent)
    };

    WeakReference<Component> component;
    Component::SafePointer<Component> proxy;

    Rectangle<int> destination;
    double destAlpha;

    int msElapsed, msTotal;
    double startSpeed, midSpeed, endSpeed, lastProgress;
    double left, top, right, bottom, alpha;
    bool isMoving, isChangingAlpha;

private:
    double timeToDistance (const double time) const noexcept
    {
        return (time < 0.5) ? time * (startSpeed + time * (midSpeed - startSpeed))
                            : 0.5 * (startSpeed + 0.5 * (midSpeed - startSpeed))
                                + (time - 0.5) * (midSpeed + (time - 0.5) * (endSpeed - midSpeed));
    }

    JUCE_DECLARE_WEAK_REFERENCEABLE (AnimationTask)
    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (AnimationTask)
};

//==============================================================================
ComponentAnimator::ComponentAnimator()  : lastTime (0) {}
ComponentAnimator::~ComponentAnimator() {}

//==============================================================================
ComponentAnimator::AnimationTask* ComponentAnimator::findTaskFor (Component* const component) const noexcept
{
    for (int i = tasks.size(); --i >= 0;)
        if (component == tasks.getUnchecked(i)->component.get())
            return tasks.getUnchecked(i);

    return nullptr;
}

void ComponentAnimator::animateComponent (Component* const component,
                                          const Rectangle<int>& finalBounds,
                                          const float finalAlpha,
                                          const int millisecondsToSpendMoving,
                                          const bool useProxyComponent,
                                          const double startSpeed,
                                          const double endSpeed)
{
    // the speeds must be 0 or greater!
    jassert (startSpeed >= 0 && endSpeed >= 0);

    if (component != nullptr)
    {
        auto* at = findTaskFor (component);

        if (at == nullptr)
        {
            at = new AnimationTask (component);
            tasks.add (at);
            sendChangeMessage();
        }

        at->reset (finalBounds, finalAlpha, millisecondsToSpendMoving,
                   useProxyComponent, startSpeed, endSpeed);

        if (! isTimerRunning())
        {
            lastTime = Time::getMillisecondCounter();
            startTimerHz (50);
        }
    }
}

void ComponentAnimator::fadeOut (Component* component, int millisecondsToTake)
{
    if (component != nullptr)
    {
        if (component->isShowing() && millisecondsToTake > 0)
            animateComponent (component, component->getBounds(), 0.0f, millisecondsToTake, true, 1.0, 1.0);

        component->setVisible (false);
    }
}

void ComponentAnimator::fadeIn (Component* component, int millisecondsToTake)
{
    if (component != nullptr && ! (component->isVisible() && component->getAlpha() == 1.0f))
    {
        component->setAlpha (0.0f);
        component->setVisible (true);
        animateComponent (component, component->getBounds(), 1.0f, millisecondsToTake, false, 1.0, 1.0);
    }
}

void ComponentAnimator::cancelAllAnimations (const bool moveComponentsToTheirFinalPositions)
{
    if (tasks.size() > 0)
    {
        if (moveComponentsToTheirFinalPositions)
            for (int i = tasks.size(); --i >= 0;)
                tasks.getUnchecked(i)->moveToFinalDestination();

        tasks.clear();
        sendChangeMessage();
    }
}

void ComponentAnimator::cancelAnimation (Component* const component,
                                         const bool moveComponentToItsFinalPosition)
{
    if (auto* at = findTaskFor (component))
    {
        if (moveComponentToItsFinalPosition)
            at->moveToFinalDestination();

        tasks.removeObject (at);
        sendChangeMessage();
    }
}

Rectangle<int> ComponentAnimator::getComponentDestination (Component* const component)
{
    jassert (component != nullptr);

    if (auto* at = findTaskFor (component))
        return at->destination;

    return component->getBounds();
}

bool ComponentAnimator::isAnimating (Component* component) const noexcept
{
    return findTaskFor (component) != nullptr;
}

bool ComponentAnimator::isAnimating() const noexcept
{
    return tasks.size() != 0;
}

void ComponentAnimator::timerCallback()
{
    auto timeNow = Time::getMillisecondCounter();

    if (lastTime == 0)
        lastTime = timeNow;

    auto elapsed = (int) (timeNow - lastTime);

    for (auto* task : Array<AnimationTask*> (tasks.begin(), tasks.size()))
    {
        if (tasks.contains (task) && ! task->useTimeslice (elapsed))
        {
            tasks.removeObject (task);
            sendChangeMessage();
        }
    }

    lastTime = timeNow;

    if (tasks.size() == 0)
        stopTimer();
}

} // namespace juce