/*
 * Copyright (C) 2013 Google Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * 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.
 *     * Neither the name of Google Inc. nor the names of its
 * 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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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 */

#ifndef AnimationClock_h
#define AnimationClock_h

#include "core/CoreExport.h"
#include "platform/wtf/Allocator.h"
#include "platform/wtf/CurrentTime.h"
#include "platform/wtf/Noncopyable.h"

#include <limits>

namespace blink {

// Maintains a stationary clock time during script execution.  Tries to track
// the glass time (the moment photons leave the screen) of the current animation
// frame.
class CORE_EXPORT AnimationClock {
  DISALLOW_NEW();
  WTF_MAKE_NONCOPYABLE(AnimationClock);

 public:
  explicit AnimationClock(WTF::TimeFunction monotonically_increasing_time =
                              WTF::MonotonicallyIncreasingTime)
      : monotonically_increasing_time_(monotonically_increasing_time),
        time_(0),
        task_for_which_time_was_calculated_(
            std::numeric_limits<unsigned>::max()) {}

  void UpdateTime(double time);
  double CurrentTime();
  void ResetTimeForTesting(double time = 0);
  void DisableSyntheticTimeForTesting() {
    monotonically_increasing_time_ = nullptr;
  }

  // notifyTaskStart should be called right before the main message loop starts
  // to run the next task from the message queue.
  static void NotifyTaskStart() { ++currently_running_task_; }

 private:
  WTF::TimeFunction monotonically_increasing_time_;
  double time_;
  unsigned task_for_which_time_was_calculated_;
  static unsigned currently_running_task_;
};

}  // namespace blink

#endif  // AnimationClock_h
