/* -*- 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 "MemoryPressureObserver.h"

namespace mozilla {

namespace layers {

MemoryPressureObserver::MemoryPressureObserver(MemoryPressureListener* aListener)

: mListener(aListener)

{}

MemoryPressureObserver::~MemoryPressureObserver()

{

  // If this assertion is hit we probably forgot to unregister the observer.

  MOZ_ASSERT(!mListener);

}

already_AddRefed<MemoryPressureObserver>

MemoryPressureObserver::Create(MemoryPressureListener* aListener)

{

  nsCOMPtr<nsIObserverService> service = services::GetObserverService();

  if (!service) {

    return nullptr;

  }

  RefPtr<MemoryPressureObserver> observer = new MemoryPressureObserver(aListener);

  bool useWeakRef = false;

  service->AddObserver(observer, "memory-pressure", useWeakRef);

  return observer.forget();

}

void

MemoryPressureObserver::Unregister()

{

  if (!mListener) {

    return;

  }

  nsCOMPtr<nsIObserverService> service = services::GetObserverService();

  if (service) {

    service->RemoveObserver(this, "memory-pressure");

  }

  mListener = nullptr;

}

NS_IMETHODIMP

MemoryPressureObserver::Observe(nsISupports* aSubject,

                                const char* aTopic,

                                const char16_t* aData)

{

  if (mListener && strcmp(aTopic, "memory-pressure") == 0) {

    MemoryPressureReason reason = MemoryPressureReason::LOW_MEMORY;

    auto reason_string = nsDependentString(aData);

    if (StringBeginsWith(reason_string, NS_LITERAL_STRING("low-memory-ongoing"))) {

        reason = MemoryPressureReason::LOW_MEMORY_ONGOING;

    } else if (StringBeginsWith(reason_string, NS_LITERAL_STRING("heap-minimize"))) {

        reason = MemoryPressureReason::HEAP_MINIMIZE;

    }

    mListener->OnMemoryPressure(reason);

  }

  return NS_OK;

}

NS_IMPL_ISUPPORTS(MemoryPressureObserver, nsIObserver)

} // namespace layers

} // namespace mozilla