/*
 * Copyright (c) 2014, Google Inc. All rights reserved.
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 * modification, are permitted provided that the following conditions are
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 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
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 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
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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
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#include "sky/engine/core/animation/AnimationClock.h"

#include <math.h>
#include "sky/engine/wtf/CurrentTime.h"

namespace {

// FIXME: This is an approximation of time between frames, used when
// ticking the animation clock outside of animation frame callbacks.
// Ideally this would be generated by the compositor.
const double approximateFrameTime = 1 / 60.0;

}

namespace blink {

unsigned AnimationClock::s_currentTask = 0;

void AnimationClock::updateTime(double time)
{
    if (time > m_time)
        m_time = time;
    m_currentTask = s_currentTask;
}

double AnimationClock::currentTime()
{
    if (m_currentTask != s_currentTask) {
        const double currentTime = m_monotonicallyIncreasingTime();
        if (m_time < currentTime) {
            // Advance to the first estimated frame after the current time.
            const double frameShift = fmod(currentTime - m_time, approximateFrameTime);
            const double newTime = currentTime + (approximateFrameTime - frameShift);
            ASSERT(newTime >= currentTime);
            ASSERT(newTime <= currentTime + approximateFrameTime);
            updateTime(newTime);
        } else {
            m_currentTask = s_currentTask;
        }
    }
    return m_time;
}

void AnimationClock::resetTimeForTesting()
{
    m_time = 0;
    m_currentTask = 0;
    s_currentTask = 0;
}

}