/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim: set ts=8 sts=2 et sw=2 tw=80: */

/* 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/. */

#include "InputEventStatistics.h"

#include "nsRefreshDriver.h"

namespace mozilla {

/*static*/ InputEventStatistics&

InputEventStatistics::Get()

{

  static UniquePtr<InputEventStatistics> sInstance;

  if (!sInstance) {

    sInstance = MakeUnique<InputEventStatistics>(ConstructorCookie());

    ClearOnShutdown(&sInstance);

  }

  return *sInstance;

}

TimeDuration

InputEventStatistics::TimeDurationCircularBuffer::GetMean()

{

  return mTotal / (int64_t)mSize;

}

InputEventStatistics::InputEventStatistics(ConstructorCookie&&)

  : mEnable(false)

{

  MOZ_ASSERT(Preferences::IsServiceAvailable());

  uint32_t inputDuration =

    Preferences::GetUint("input_event_queue.default_duration_per_event",

                         sDefaultInputDuration);

  TimeDuration defaultDuration = TimeDuration::FromMilliseconds(inputDuration);

  uint32_t count =

    Preferences::GetUint("input_event_queue.count_for_prediction",

                         sInputCountForPrediction);

  mLastInputDurations =

    MakeUnique<TimeDurationCircularBuffer>(count, defaultDuration);

  uint32_t maxDuration =

    Preferences::GetUint("input_event_queue.duration.max",

                         sMaxReservedTimeForHandlingInput);

  uint32_t minDuration =

    Preferences::GetUint("input_event_queue.duration.min",

                         sMinReservedTimeForHandlingInput);

  mMaxInputDuration = TimeDuration::FromMilliseconds(maxDuration);

  mMinInputDuration = TimeDuration::FromMilliseconds(minDuration);

}

TimeStamp

InputEventStatistics::GetInputHandlingStartTime(uint32_t aInputCount)

{

  MOZ_ASSERT(mEnable);

  Maybe<TimeStamp> nextTickHint = nsRefreshDriver::GetNextTickHint();

  if (nextTickHint.isNothing()) {

    // Return a past time to process input events immediately.

    return TimeStamp::Now() - TimeDuration::FromMilliseconds(1);

  }

  TimeDuration inputCost = mLastInputDurations->GetMean() * aInputCount;

  inputCost = inputCost > mMaxInputDuration

              ? mMaxInputDuration

              : inputCost < mMinInputDuration

              ? mMinInputDuration

              : inputCost;

  return nextTickHint.value() - inputCost;

}

} // namespace mozilla