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

   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
{

Viewport::Viewport (const String& name)  : Component (name)
{
    // content holder is used to clip the contents so they don't overlap the scrollbars
    addAndMakeVisible (contentHolder);
    contentHolder.setInterceptsMouseClicks (false, true);

    scrollBarThickness = getLookAndFeel().getDefaultScrollbarWidth();

    setInterceptsMouseClicks (false, true);
    setWantsKeyboardFocus (true);
    setScrollOnDragEnabled (Desktop::getInstance().getMainMouseSource().isTouch());

    recreateScrollbars();
}

Viewport::~Viewport()
{
    setScrollOnDragEnabled (false);
    deleteOrRemoveContentComp();
}

//==============================================================================
void Viewport::visibleAreaChanged (const Rectangle<int>&) {}
void Viewport::viewedComponentChanged (Component*) {}

//==============================================================================
void Viewport::deleteOrRemoveContentComp()
{
    if (contentComp != nullptr)
    {
        contentComp->removeComponentListener (this);

        if (deleteContent)
        {
            // This sets the content comp to a null pointer before deleting the old one, in case
            // anything tries to use the old one while it's in mid-deletion..
            std::unique_ptr<Component> oldCompDeleter (contentComp.get());
            contentComp = nullptr;
        }
        else
        {
            contentHolder.removeChildComponent (contentComp);
            contentComp = nullptr;
        }
    }
}

void Viewport::setViewedComponent (Component* const newViewedComponent, const bool deleteComponentWhenNoLongerNeeded)
{
    if (contentComp.get() != newViewedComponent)
    {
        deleteOrRemoveContentComp();
        contentComp = newViewedComponent;
        deleteContent = deleteComponentWhenNoLongerNeeded;

        if (contentComp != nullptr)
        {
            contentHolder.addAndMakeVisible (contentComp);
            setViewPosition (Point<int>());
            contentComp->addComponentListener (this);
        }

        viewedComponentChanged (contentComp);
        updateVisibleArea();
    }
}

void Viewport::recreateScrollbars()
{
    verticalScrollBar.reset();
    horizontalScrollBar.reset();

    verticalScrollBar  .reset (createScrollBarComponent (true));
    horizontalScrollBar.reset (createScrollBarComponent (false));

    addChildComponent (verticalScrollBar.get());
    addChildComponent (horizontalScrollBar.get());

    getVerticalScrollBar().addListener (this);
    getHorizontalScrollBar().addListener (this);

    resized();
}

int Viewport::getMaximumVisibleWidth() const            { return contentHolder.getWidth(); }
int Viewport::getMaximumVisibleHeight() const           { return contentHolder.getHeight(); }

bool Viewport::canScrollVertically() const noexcept     { return contentComp->getY() < 0 || contentComp->getBottom() > getHeight(); }
bool Viewport::canScrollHorizontally() const noexcept   { return contentComp->getX() < 0 || contentComp->getRight()  > getWidth(); }

Point<int> Viewport::viewportPosToCompPos (Point<int> pos) const
{
    jassert (contentComp != nullptr);

    auto contentBounds = contentHolder.getLocalArea (contentComp.get(), contentComp->getLocalBounds());

    Point<int> p (jmax (jmin (0, contentHolder.getWidth()  - contentBounds.getWidth()),  jmin (0, -(pos.x))),
                  jmax (jmin (0, contentHolder.getHeight() - contentBounds.getHeight()), jmin (0, -(pos.y))));

    return p.transformedBy (contentComp->getTransform().inverted());
}

void Viewport::setViewPosition (const int xPixelsOffset, const int yPixelsOffset)
{
    setViewPosition ({ xPixelsOffset, yPixelsOffset });
}

void Viewport::setViewPosition (Point<int> newPosition)
{
    if (contentComp != nullptr)
        contentComp->setTopLeftPosition (viewportPosToCompPos (newPosition));
}

void Viewport::setViewPositionProportionately (const double x, const double y)
{
    if (contentComp != nullptr)
        setViewPosition (jmax (0, roundToInt (x * (contentComp->getWidth()  - getWidth()))),
                         jmax (0, roundToInt (y * (contentComp->getHeight() - getHeight()))));
}

bool Viewport::autoScroll (const int mouseX, const int mouseY, const int activeBorderThickness, const int maximumSpeed)
{
    if (contentComp != nullptr)
    {
        int dx = 0, dy = 0;

        if (getHorizontalScrollBar().isVisible() || canScrollHorizontally())
        {
            if (mouseX < activeBorderThickness)
                dx = activeBorderThickness - mouseX;
            else if (mouseX >= contentHolder.getWidth() - activeBorderThickness)
                dx = (contentHolder.getWidth() - activeBorderThickness) - mouseX;

            if (dx < 0)
                dx = jmax (dx, -maximumSpeed, contentHolder.getWidth() - contentComp->getRight());
            else
                dx = jmin (dx, maximumSpeed, -contentComp->getX());
        }

        if (getVerticalScrollBar().isVisible() || canScrollVertically())
        {
            if (mouseY < activeBorderThickness)
                dy = activeBorderThickness - mouseY;
            else if (mouseY >= contentHolder.getHeight() - activeBorderThickness)
                dy = (contentHolder.getHeight() - activeBorderThickness) - mouseY;

            if (dy < 0)
                dy = jmax (dy, -maximumSpeed, contentHolder.getHeight() - contentComp->getBottom());
            else
                dy = jmin (dy, maximumSpeed, -contentComp->getY());
        }

        if (dx != 0 || dy != 0)
        {
            contentComp->setTopLeftPosition (contentComp->getX() + dx,
                                             contentComp->getY() + dy);

            return true;
        }
    }

    return false;
}

void Viewport::componentMovedOrResized (Component&, bool, bool)
{
    updateVisibleArea();
}

//==============================================================================
typedef AnimatedPosition<AnimatedPositionBehaviours::ContinuousWithMomentum> ViewportDragPosition;

struct Viewport::DragToScrollListener   : private MouseListener,
                                          private ViewportDragPosition::Listener
{
    DragToScrollListener (Viewport& v)  : viewport (v)
    {
        viewport.contentHolder.addMouseListener (this, true);
        offsetX.addListener (this);
        offsetY.addListener (this);
        offsetX.behaviour.setMinimumVelocity (60);
        offsetY.behaviour.setMinimumVelocity (60);
    }

    ~DragToScrollListener() override
    {
        viewport.contentHolder.removeMouseListener (this);
        Desktop::getInstance().removeGlobalMouseListener (this);
    }

    void positionChanged (ViewportDragPosition&, double) override
    {
        viewport.setViewPosition (originalViewPos - Point<int> ((int) offsetX.getPosition(),
                                                                (int) offsetY.getPosition()));
    }

    void mouseDown (const MouseEvent&) override
    {
        if (! isGlobalMouseListener)
        {
            offsetX.setPosition (offsetX.getPosition());
            offsetY.setPosition (offsetY.getPosition());

            // switch to a global mouse listener so we still receive mouseUp events
            // if the original event component is deleted
            viewport.contentHolder.removeMouseListener (this);
            Desktop::getInstance().addGlobalMouseListener (this);

            isGlobalMouseListener = true;
        }
    }

    void mouseDrag (const MouseEvent& e) override
    {
        if (Desktop::getInstance().getNumDraggingMouseSources() == 1 && ! doesMouseEventComponentBlockViewportDrag (e.eventComponent))
        {
            auto totalOffset = e.getOffsetFromDragStart().toFloat();

            if (! isDragging && totalOffset.getDistanceFromOrigin() > 8.0f)
            {
                isDragging = true;

                originalViewPos = viewport.getViewPosition();
                offsetX.setPosition (0.0);
                offsetX.beginDrag();
                offsetY.setPosition (0.0);
                offsetY.beginDrag();
            }

            if (isDragging)
            {
                offsetX.drag (totalOffset.x);
                offsetY.drag (totalOffset.y);
            }
        }
    }

    void mouseUp (const MouseEvent&) override
    {
        if (isGlobalMouseListener && Desktop::getInstance().getNumDraggingMouseSources() == 0)
            endDragAndClearGlobalMouseListener();
    }

    void endDragAndClearGlobalMouseListener()
    {
        offsetX.endDrag();
        offsetY.endDrag();
        isDragging = false;

        viewport.contentHolder.addMouseListener (this, true);
        Desktop::getInstance().removeGlobalMouseListener (this);

        isGlobalMouseListener = false;
    }

    bool doesMouseEventComponentBlockViewportDrag (const Component* eventComp)
    {
        for (auto c = eventComp; c != nullptr && c != &viewport; c = c->getParentComponent())
            if (c->getViewportIgnoreDragFlag())
                return true;

        return false;
    }

    Viewport& viewport;
    ViewportDragPosition offsetX, offsetY;
    Point<int> originalViewPos;
    bool isDragging = false;
    bool isGlobalMouseListener = false;

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (DragToScrollListener)
};

void Viewport::setScrollOnDragEnabled (bool shouldScrollOnDrag)
{
    if (isScrollOnDragEnabled() != shouldScrollOnDrag)
    {
        if (shouldScrollOnDrag)
            dragToScrollListener.reset (new DragToScrollListener (*this));
        else
            dragToScrollListener.reset();
    }
}

bool Viewport::isScrollOnDragEnabled() const noexcept
{
    return dragToScrollListener != nullptr;
}

bool Viewport::isCurrentlyScrollingOnDrag() const noexcept
{
    return dragToScrollListener != nullptr && dragToScrollListener->isDragging;
}

//==============================================================================
void Viewport::lookAndFeelChanged()
{
    if (! customScrollBarThickness)
    {
        scrollBarThickness = getLookAndFeel().getDefaultScrollbarWidth();
        resized();
    }
}

void Viewport::resized()
{
    updateVisibleArea();
}

//==============================================================================
void Viewport::updateVisibleArea()
{
    auto scrollbarWidth = getScrollBarThickness();
    const bool canShowAnyBars = getWidth() > scrollbarWidth && getHeight() > scrollbarWidth;
    const bool canShowHBar = showHScrollbar && canShowAnyBars;
    const bool canShowVBar = showVScrollbar && canShowAnyBars;

    bool hBarVisible = false, vBarVisible = false;
    Rectangle<int> contentArea;

    for (int i = 3; --i >= 0;)
    {
        hBarVisible = canShowHBar && ! getHorizontalScrollBar().autoHides();
        vBarVisible = canShowVBar && ! getVerticalScrollBar().autoHides();
        contentArea = getLocalBounds();

        if (contentComp != nullptr && ! contentArea.contains (contentComp->getBounds()))
        {
            hBarVisible = canShowHBar && (hBarVisible || contentComp->getX() < 0 || contentComp->getRight() > contentArea.getWidth());
            vBarVisible = canShowVBar && (vBarVisible || contentComp->getY() < 0 || contentComp->getBottom() > contentArea.getHeight());

            if (vBarVisible)
                contentArea.setWidth (getWidth() - scrollbarWidth);

            if (hBarVisible)
                contentArea.setHeight (getHeight() - scrollbarWidth);

            if (! contentArea.contains (contentComp->getBounds()))
            {
                hBarVisible = canShowHBar && (hBarVisible || contentComp->getRight() > contentArea.getWidth());
                vBarVisible = canShowVBar && (vBarVisible || contentComp->getBottom() > contentArea.getHeight());
            }
        }

        if (vBarVisible)  contentArea.setWidth  (getWidth()  - scrollbarWidth);
        if (hBarVisible)  contentArea.setHeight (getHeight() - scrollbarWidth);

        if (! vScrollbarRight  && vBarVisible)
            contentArea.setX (scrollbarWidth);

        if (! hScrollbarBottom && hBarVisible)
            contentArea.setY (scrollbarWidth);

        if (contentComp == nullptr)
        {
            contentHolder.setBounds (contentArea);
            break;
        }

        auto oldContentBounds = contentComp->getBounds();
        contentHolder.setBounds (contentArea);

        // If the content has changed its size, that might affect our scrollbars, so go round again and re-calculate..
        if (oldContentBounds == contentComp->getBounds())
            break;
    }

    Rectangle<int> contentBounds;

    if (auto cc = contentComp.get())
        contentBounds = contentHolder.getLocalArea (cc, cc->getLocalBounds());

    auto visibleOrigin = -contentBounds.getPosition();

    auto& hbar = getHorizontalScrollBar();
    auto& vbar = getVerticalScrollBar();

    hbar.setBounds (contentArea.getX(), hScrollbarBottom ? contentArea.getHeight() : 0, contentArea.getWidth(), scrollbarWidth);
    hbar.setRangeLimits (0.0, contentBounds.getWidth());
    hbar.setCurrentRange (visibleOrigin.x, contentArea.getWidth());
    hbar.setSingleStepSize (singleStepX);

    if (canShowHBar && ! hBarVisible)
        visibleOrigin.setX (0);

    vbar.setBounds (vScrollbarRight ? contentArea.getWidth() : 0, contentArea.getY(), scrollbarWidth, contentArea.getHeight());
    vbar.setRangeLimits (0.0, contentBounds.getHeight());
    vbar.setCurrentRange (visibleOrigin.y, contentArea.getHeight());
    vbar.setSingleStepSize (singleStepY);

    if (canShowVBar && ! vBarVisible)
        visibleOrigin.setY (0);

    // Force the visibility *after* setting the ranges to avoid flicker caused by edge conditions in the numbers.
    hbar.setVisible (hBarVisible);
    vbar.setVisible (vBarVisible);

    if (contentComp != nullptr)
    {
        auto newContentCompPos = viewportPosToCompPos (visibleOrigin);

        if (contentComp->getBounds().getPosition() != newContentCompPos)
        {
            contentComp->setTopLeftPosition (newContentCompPos);  // (this will re-entrantly call updateVisibleArea again)
            return;
        }
    }

    const Rectangle<int> visibleArea (visibleOrigin.x, visibleOrigin.y,
                                      jmin (contentBounds.getWidth()  - visibleOrigin.x, contentArea.getWidth()),
                                      jmin (contentBounds.getHeight() - visibleOrigin.y, contentArea.getHeight()));

    if (lastVisibleArea != visibleArea)
    {
        lastVisibleArea = visibleArea;
        visibleAreaChanged (visibleArea);
    }

    hbar.handleUpdateNowIfNeeded();
    vbar.handleUpdateNowIfNeeded();
}

//==============================================================================
void Viewport::setSingleStepSizes (const int stepX, const int stepY)
{
    if (singleStepX != stepX || singleStepY != stepY)
    {
        singleStepX = stepX;
        singleStepY = stepY;
        updateVisibleArea();
    }
}

void Viewport::setScrollBarsShown (const bool showVerticalScrollbarIfNeeded,
                                   const bool showHorizontalScrollbarIfNeeded,
                                   const bool allowVerticalScrollingWithoutScrollbar,
                                   const bool allowHorizontalScrollingWithoutScrollbar)
{
    allowScrollingWithoutScrollbarV = allowVerticalScrollingWithoutScrollbar;
    allowScrollingWithoutScrollbarH = allowHorizontalScrollingWithoutScrollbar;

    if (showVScrollbar != showVerticalScrollbarIfNeeded
         || showHScrollbar != showHorizontalScrollbarIfNeeded)
    {
        showVScrollbar = showVerticalScrollbarIfNeeded;
        showHScrollbar = showHorizontalScrollbarIfNeeded;
        updateVisibleArea();
    }
}

void Viewport::setScrollBarThickness (const int thickness)
{
    int newThickness;

    // To stay compatible with the previous code: use the
    // default thickness if thickness parameter is zero
    // or negative
    if (thickness <= 0)
    {
        customScrollBarThickness = false;
        newThickness = getLookAndFeel().getDefaultScrollbarWidth();
    }
    else
    {
        customScrollBarThickness = true;
        newThickness = thickness;
    }

    if (scrollBarThickness != newThickness)
    {
        scrollBarThickness = newThickness;
        updateVisibleArea();
    }
}

int Viewport::getScrollBarThickness() const
{
    return scrollBarThickness;
}

void Viewport::scrollBarMoved (ScrollBar* scrollBarThatHasMoved, double newRangeStart)
{
    auto newRangeStartInt = roundToInt (newRangeStart);

    if (scrollBarThatHasMoved == horizontalScrollBar.get())
    {
        setViewPosition (newRangeStartInt, getViewPositionY());
    }
    else if (scrollBarThatHasMoved == verticalScrollBar.get())
    {
        setViewPosition (getViewPositionX(), newRangeStartInt);
    }
}

void Viewport::mouseWheelMove (const MouseEvent& e, const MouseWheelDetails& wheel)
{
    if (! useMouseWheelMoveIfNeeded (e, wheel))
        Component::mouseWheelMove (e, wheel);
}

static int rescaleMouseWheelDistance (float distance, int singleStepSize) noexcept
{
    if (distance == 0.0f)
        return 0;

    distance *= 14.0f * singleStepSize;

    return roundToInt (distance < 0 ? jmin (distance, -1.0f)
                                    : jmax (distance,  1.0f));
}

bool Viewport::useMouseWheelMoveIfNeeded (const MouseEvent& e, const MouseWheelDetails& wheel)
{
    if (! (e.mods.isAltDown() || e.mods.isCtrlDown() || e.mods.isCommandDown()))
    {
        const bool canScrollVert = (allowScrollingWithoutScrollbarV || getVerticalScrollBar().isVisible());
        const bool canScrollHorz = (allowScrollingWithoutScrollbarH || getHorizontalScrollBar().isVisible());

        if (canScrollHorz || canScrollVert)
        {
            auto deltaX = rescaleMouseWheelDistance (wheel.deltaX, singleStepX);
            auto deltaY = rescaleMouseWheelDistance (wheel.deltaY, singleStepY);

            auto pos = getViewPosition();

            if (deltaX != 0 && deltaY != 0 && canScrollHorz && canScrollVert)
            {
                pos.x -= deltaX;
                pos.y -= deltaY;
            }
            else if (canScrollHorz && (deltaX != 0 || e.mods.isShiftDown() || ! canScrollVert))
            {
                pos.x -= deltaX != 0 ? deltaX : deltaY;
            }
            else if (canScrollVert && deltaY != 0)
            {
                pos.y -= deltaY;
            }

            if (pos != getViewPosition())
            {
                setViewPosition (pos);
                return true;
            }
        }
    }

    return false;
}

static bool isUpDownKeyPress (const KeyPress& key)
{
    return key == KeyPress::upKey
        || key == KeyPress::downKey
        || key == KeyPress::pageUpKey
        || key == KeyPress::pageDownKey
        || key == KeyPress::homeKey
        || key == KeyPress::endKey;
}

static bool isLeftRightKeyPress (const KeyPress& key)
{
    return key == KeyPress::leftKey
        || key == KeyPress::rightKey;
}

bool Viewport::keyPressed (const KeyPress& key)
{
    const bool isUpDownKey = isUpDownKeyPress (key);

    if (getVerticalScrollBar().isVisible() && isUpDownKey)
        return getVerticalScrollBar().keyPressed (key);

    const bool isLeftRightKey = isLeftRightKeyPress (key);

    if (getHorizontalScrollBar().isVisible() && (isUpDownKey || isLeftRightKey))
        return getHorizontalScrollBar().keyPressed (key);

    return false;
}

bool Viewport::respondsToKey (const KeyPress& key)
{
    return isUpDownKeyPress (key) || isLeftRightKeyPress (key);
}

ScrollBar* Viewport::createScrollBarComponent (bool isVertical)
{
    return new ScrollBar (isVertical);
}

void Viewport::setScrollBarPosition (bool verticalScrollbarOnRight,
                                     bool horizontalScrollbarAtBottom)
{
    vScrollbarRight  = verticalScrollbarOnRight;
    hScrollbarBottom = horizontalScrollbarAtBottom;

    resized();
}

} // namespace juce