/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_layers_AndroidVelocityTracker_h
#define mozilla_layers_AndroidVelocityTracker_h

#include <utility>

#include "Axis.h"
#include "mozilla/Maybe.h"
#include "nsTArray.h"

namespace mozilla {
namespace layers {

class AndroidVelocityTracker : public VelocityTracker {
 public:
  explicit AndroidVelocityTracker();
  void StartTracking(ParentLayerCoord aPos, TimeStamp aTimestamp) override;
  Maybe<float> AddPosition(ParentLayerCoord aPos,
                           TimeStamp aTimestamp) override;
  Maybe<float> ComputeVelocity(TimeStamp aTimestamp) override;
  void Clear() override;

 private:
  // A queue of (timestamp, position) pairs; these are the historical
  // positions at the given timestamps.
  nsTArray<std::pair<TimeStamp, ParentLayerCoord>> mHistory;
  // The last time an event was added to the tracker, or the null moment if no
  // events have been added.
  TimeStamp mLastEventTime;
};

}  // namespace layers
}  // namespace mozilla

#endif