/* -*- 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 "gtest/gtest.h"

#include "AvailableMemoryWatcher.h"
#include "mozilla/gtest/MozAssertions.h"
#include "mozilla/SpinEventLoopUntil.h"
#include "mozilla/Unused.h"
#include "nsIObserver.h"
#include "nsIObserverService.h"
#include "nsITimer.h"
#include "nsMemoryPressure.h"
#include "TelemetryFixture.h"
#include "TelemetryTestHelpers.h"

using namespace mozilla;

namespace {

template <typename ConditionT>
bool WaitUntil(const ConditionT& aCondition, uint32_t aTimeoutMs) {
  bool isTimeout = false;

  // The message queue can be empty and the loop stops
  // waiting for a new event before detecting timeout.
  // Creating a timer to fire a timeout event.
  nsCOMPtr<nsITimer> timer;
  NS_NewTimerWithFuncCallback(
      getter_AddRefs(timer),
      [](nsITimer*, void* isTimeout) {
        *reinterpret_cast<bool*>(isTimeout) = true;
      },
      &isTimeout, aTimeoutMs, nsITimer::TYPE_ONE_SHOT, __func__);

  SpinEventLoopUntil("TestAvailableMemoryWatcherMac"_ns, [&]() -> bool {
    if (isTimeout) {
      return true;
    }
    return aCondition();
  });

  return !isTimeout;
}

class Spinner final : public nsIObserver {
  nsCOMPtr<nsIObserverService> mObserverSvc;
  nsDependentCString mTopicToWatch;
  bool mTopicObserved;

  ~Spinner() = default;

 public:
  NS_DECL_ISUPPORTS

  Spinner(nsIObserverService* aObserverSvc, const char* const aTopic,
          const char16_t* const aSubTopic)
      : mObserverSvc(aObserverSvc),
        mTopicToWatch(aTopic),
        mTopicObserved(false) {}

  NS_IMETHOD Observe(nsISupports* aSubject, const char* aTopic,
                     const char16_t* aData) override {
    if (mTopicToWatch == aTopic) {
      mTopicObserved = true;
      mObserverSvc->RemoveObserver(this, aTopic);

      // Force the loop to move in case that there is no event in the queue.
      nsCOMPtr<nsIRunnable> dummyEvent = new Runnable(__func__);
      NS_DispatchToMainThread(dummyEvent);
    }
    return NS_OK;
  }

  void StartListening() {
    mTopicObserved = false;
    mObserverSvc->AddObserver(this, mTopicToWatch.get(), false);
  }

  bool Wait(uint32_t aTimeoutMs) {
    return WaitUntil([this]() { return this->mTopicObserved; }, aTimeoutMs);
  }
};

NS_IMPL_ISUPPORTS(Spinner, nsIObserver)

class MockTabUnloader final : public nsITabUnloader {
  ~MockTabUnloader() = default;

  uint32_t mCounter;

 public:
  MockTabUnloader() : mCounter(0) {}

  NS_DECL_THREADSAFE_ISUPPORTS

  void ResetCounter() { mCounter = 0; }
  uint32_t GetCounter() const { return mCounter; }

  NS_IMETHOD UnloadTabAsync() override {
    ++mCounter;
    // Issue a memory-pressure to verify OnHighMemory issues
    // a memory-pressure-stop event.
    NS_NotifyOfEventualMemoryPressure(MemoryPressureState::LowMemory);
    return NS_OK;
  }
};

NS_IMPL_ISUPPORTS(MockTabUnloader, nsITabUnloader)

}  // namespace

class AvailableMemoryWatcherFixture : public TelemetryTestFixture {
  nsCOMPtr<nsIObserverService> mObserverSvc;

 protected:
  RefPtr<nsAvailableMemoryWatcherBase> mWatcher;
  RefPtr<Spinner> mHighMemoryObserver;
  RefPtr<Spinner> mLowMemoryObserver;
  RefPtr<MockTabUnloader> mTabUnloader;

  static constexpr uint32_t kStateChangeTimeoutMs = 20000;
  static constexpr uint32_t kNotificationTimeoutMs = 20000;

  void SetUp() override {
    TelemetryTestFixture::SetUp();

    mObserverSvc = do_GetService(NS_OBSERVERSERVICE_CONTRACTID);
    ASSERT_TRUE(mObserverSvc);

    mHighMemoryObserver =
        new Spinner(mObserverSvc, "memory-pressure-stop", nullptr);
    mLowMemoryObserver = new Spinner(mObserverSvc, "memory-pressure", nullptr);

    mTabUnloader = new MockTabUnloader;

    mWatcher = nsAvailableMemoryWatcherBase::GetSingleton();
    mWatcher->RegisterTabUnloader(mTabUnloader);
  }
};

class MemoryWatcherTelemetryEvent {
  static nsLiteralString sEventCategory;
  static nsLiteralString sEventMethod;
  static nsLiteralString sEventObject;
  uint32_t mLastCountOfEvents;

 public:
  explicit MemoryWatcherTelemetryEvent(JSContext* aCx) : mLastCountOfEvents(0) {
    JS::RootedValue snapshot(aCx);
    TelemetryTestHelpers::GetEventSnapshot(aCx, &snapshot);
    nsTArray<nsString> eventValues = TelemetryTestHelpers::EventValuesToArray(
        aCx, snapshot, sEventCategory, sEventMethod, sEventObject);
    mLastCountOfEvents = eventValues.Length();
  }

  void ValidateLastEvent(JSContext* aCx) {
    JS::RootedValue snapshot(aCx);
    TelemetryTestHelpers::GetEventSnapshot(aCx, &snapshot);
    nsTArray<nsString> eventValues = TelemetryTestHelpers::EventValuesToArray(
        aCx, snapshot, sEventCategory, sEventMethod, sEventObject);

    // A new event was generated.
    EXPECT_EQ(eventValues.Length(), mLastCountOfEvents + 1);
    if (eventValues.IsEmpty()) {
      return;
    }

    // Update mLastCountOfEvents for a subsequent call to ValidateLastEvent
    ++mLastCountOfEvents;

    nsTArray<nsString> tokens;
    for (const nsAString& token : eventValues.LastElement().Split(',')) {
      tokens.AppendElement(token);
    }
    EXPECT_EQ(tokens.Length(), 3U);

    // The third token should be a valid floating number.
    nsresult rv;
    tokens[2].ToDouble(&rv);
    EXPECT_NS_SUCCEEDED(rv);
  }
};

nsLiteralString MemoryWatcherTelemetryEvent::sEventCategory =
    u"memory_watcher"_ns;
nsLiteralString MemoryWatcherTelemetryEvent::sEventMethod =
    u"on_high_memory"_ns;
nsLiteralString MemoryWatcherTelemetryEvent::sEventObject = u"stats"_ns;

/*
 * Test the browser memory pressure reponse by artificially putting the system
 * into the "critical" level and ensuring 1) a tab unload attempt occurs and
 * 2) the Gecko memory-pressure notitificiation start and stop events occur.
 */
TEST_F(AvailableMemoryWatcherFixture, MemoryPressureResponse) {
  // Set the memory pressure state to normal in case we are already
  // running in a low memory pressure state.
  mWatcher->OnMemoryPressureChanged(MacMemoryPressureLevel::Value::eNormal);

  // Reset state
  mTabUnloader->ResetCounter();
  AutoJSContextWithGlobal cx(mCleanGlobal);
  MemoryWatcherTelemetryEvent telemetryEvent(cx.GetJSContext());

  // Simulate a low memory OS callback and make sure we observe
  // a memory-pressure event and a tab unload.
  mLowMemoryObserver->StartListening();
  mWatcher->OnMemoryPressureChanged(MacMemoryPressureLevel::Value::eWarning);
  mWatcher->OnMemoryPressureChanged(MacMemoryPressureLevel::Value::eCritical);
  EXPECT_TRUE(WaitUntil([this]() { return mTabUnloader->GetCounter() >= 1; },
                        kStateChangeTimeoutMs));
  EXPECT_TRUE(mLowMemoryObserver->Wait(kStateChangeTimeoutMs));

  // Simulate the normal memory pressure OS callback and make
  // sure we observe a memory-pressure-stop event.
  mHighMemoryObserver->StartListening();
  mWatcher->OnMemoryPressureChanged(MacMemoryPressureLevel::Value::eWarning);
  mWatcher->OnMemoryPressureChanged(MacMemoryPressureLevel::Value::eNormal);
  EXPECT_TRUE(mHighMemoryObserver->Wait(kStateChangeTimeoutMs));

  telemetryEvent.ValidateLastEvent(cx.GetJSContext());
}