/*
 * Copyright (c) 2010, Google Inc. All rights reserved.
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 * modification, are permitted provided that the following conditions are
 * met:
 * 
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "config.h"
#include "ScrollAnimator.h"

#include "FloatPoint.h"
#include "PlatformWheelEvent.h"
#include "ScrollableArea.h"
#include <algorithm>
#include <wtf/PassOwnPtr.h>

using namespace std;

namespace WebCore {

#if !ENABLE(SMOOTH_SCROLLING)
PassOwnPtr<ScrollAnimator> ScrollAnimator::create(ScrollableArea* scrollableArea)
{
    return adoptPtr(new ScrollAnimator(scrollableArea));
}
#endif

ScrollAnimator::ScrollAnimator(ScrollableArea* scrollableArea)
    : m_scrollableArea(scrollableArea)
    , m_currentPosX(0)
    , m_currentPosY(0)
{
}

ScrollAnimator::~ScrollAnimator()
{
}

bool ScrollAnimator::scroll(ScrollbarOrientation orientation, ScrollGranularity, float step, float multiplier)
{
    float* currentPos = (orientation == HorizontalScrollbar) ? &m_currentPosX : &m_currentPosY;
    float newPos = std::max(std::min(*currentPos + (step * multiplier), static_cast<float>(m_scrollableArea->scrollSize(orientation))), 0.0f);
    if (*currentPos == newPos)
        return false;
    *currentPos = newPos;

    notityPositionChanged();

    return true;
}

void ScrollAnimator::scrollToOffsetWithoutAnimation(const FloatPoint& offset)
{
    if (m_currentPosX != offset.x() || m_currentPosY != offset.y()) {
        m_currentPosX = offset.x();
        m_currentPosY = offset.y();
        notityPositionChanged();
    }
}

void ScrollAnimator::handleWheelEvent(PlatformWheelEvent& e)
{
    Scrollbar* horizontalScrollbar = m_scrollableArea->horizontalScrollbar();
    Scrollbar* verticalScrollbar = m_scrollableArea->verticalScrollbar();

    // Accept the event if we have a scrollbar in that direction and can still
    // scroll any further.
    float deltaX = horizontalScrollbar ? e.deltaX() : 0;
    float deltaY = verticalScrollbar ? e.deltaY() : 0;

    IntSize maxForwardScrollDelta = m_scrollableArea->maximumScrollPosition() - m_scrollableArea->scrollPosition();
    IntSize maxBackwardScrollDelta = m_scrollableArea->scrollPosition() - m_scrollableArea->minimumScrollPosition();
    if ((deltaX < 0 && maxForwardScrollDelta.width() > 0)
        || (deltaX > 0 && maxBackwardScrollDelta.width() > 0)
        || (deltaY < 0 && maxForwardScrollDelta.height() > 0)
        || (deltaY > 0 && maxBackwardScrollDelta.height() > 0)) {
        e.accept();
        if (e.granularity() == ScrollByPageWheelEvent) {
            ASSERT(!e.deltaX());
            bool negative = deltaY < 0;
            deltaY = max(max(static_cast<float>(m_scrollableArea->visibleHeight()) * Scrollbar::minFractionToStepWhenPaging(), static_cast<float>(m_scrollableArea->visibleHeight() - Scrollbar::maxOverlapBetweenPages())), 1.0f);
            if (negative)
                deltaY = -deltaY;
        }

        if (deltaY)
            scroll(VerticalScrollbar, ScrollByPixel, verticalScrollbar->pixelStep(), -deltaY);
        if (deltaX)
            scroll(HorizontalScrollbar, ScrollByPixel, horizontalScrollbar->pixelStep(), -deltaX);
    }
}

#if ENABLE(GESTURE_EVENTS)
void ScrollAnimator::handleGestureEvent(const PlatformGestureEvent&)
{
}
#endif

FloatPoint ScrollAnimator::currentPosition() const
{
    return FloatPoint(m_currentPosX, m_currentPosY);
}

void ScrollAnimator::notityPositionChanged()
{
    m_scrollableArea->setScrollOffsetFromAnimation(IntPoint(m_currentPosX, m_currentPosY));
}

} // namespace WebCore