/* 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_places_Shutdown_h_

#define mozilla_places_Shutdown_h_

#include "nsIAsyncShutdown.h"

#include "Database.h"

#include "nsProxyRelease.h"

namespace mozilla {

namespace places {

class Database;

/**

 * This is most of the code responsible for Places shutdown.

 *

 * PHASE 1 (Legacy clients shutdown)

 * The shutdown procedure begins when the Database singleton receives

 * profile-change-teardown (note that tests will instead notify nsNavHistory,

 * that forwards the notification to the Database instance).

 * Database::Observe first of all checks if initialization was completed

 * properly, to avoid race conditions, then it notifies "places-shutdown" to

 * legacy clients. Legacy clients are supposed to start and complete any

 * shutdown critical work in the same tick, since we won't wait for them.

 * PHASE 2 (Modern clients shutdown)

 * Modern clients should instead register as a blocker by passing a promise to

 * nsINavHistoryService::shutdownClient (for example see Sanitizer.jsm), so they

 * block Places shutdown until the promise is resolved.

 * When profile-change-teardown is observed by async shutdown, it calls

 * ClientsShutdownBlocker::BlockShutdown. This class is registered as a teardown

 * phase blocker in Database::Init (see Database::mClientsShutdown).

 * ClientsShutdownBlocker::BlockShudown waits for all the clients registered

 * through nsINavHistoryService::shutdownClient. When all the clients are done,

 * its `Done` method is invoked, and it stops blocking the shutdown phase, so

 * that it can continue.

 *

 * PHASE 3 (Connection shutdown)

 * ConnectionBlocker is registered as a profile-before-change blocker in

 * Database::Init (see Database::mConnectionShutdown).

 * When profile-before-change is observer by async shutdown, it calls

 * ConnectionShutdownBlocker::BlockShutdown.

 * Then the control is passed to Database::Shutdown, that executes some sanity

 * checks, clears cached statements and proceeds with asyncClose.

 * Once the connection is definitely closed, Database will call back

 * ConnectionBlocker::Complete. At this point a final

 * places-connection-closed notification is sent, for testing purposes.

 */

/**

 * A base AsyncShutdown blocker in charge of shutting down Places.

 */

class PlacesShutdownBlocker : public nsIAsyncShutdownBlocker

                            , public nsIAsyncShutdownCompletionCallback

{

public:

  NS_DECL_THREADSAFE_ISUPPORTS

  NS_DECL_NSIASYNCSHUTDOWNBLOCKER

  NS_DECL_NSIASYNCSHUTDOWNCOMPLETIONCALLBACK

  explicit PlacesShutdownBlocker(const nsString& aName);

  already_AddRefed<nsIAsyncShutdownClient> GetClient();

  /**

   * `true` if we have not started shutdown, i.e.  if

   * `BlockShutdown()` hasn't been called yet, false otherwise.

   */

  static bool IsStarted() {

    return sIsStarted;

  }

  // The current state, used internally and for forensics/debugging purposes.

  // Not all the states make sense for all the derived classes.

  enum States {

    NOT_STARTED,

    // Execution of `BlockShutdown` in progress.

    RECEIVED_BLOCK_SHUTDOWN,

    // Values specific to ClientsShutdownBlocker

    // a. Set while we are waiting for clients to do their job and unblock us.

    CALLED_WAIT_CLIENTS,

    // b. Set when all the clients are done.

    RECEIVED_DONE,

    // Values specific to ConnectionShutdownBlocker

    // a. Set after we notified observers that Places is closing the connection.

    NOTIFIED_OBSERVERS_PLACES_WILL_CLOSE_CONNECTION,

    // b. Set after we pass control to Database::Shutdown, and wait for it to

    // close the connection and call our `Complete` method when done.

    CALLED_STORAGESHUTDOWN,

    // c. Set when Database has closed the connection and passed control to

    // us through `Complete`.

    RECEIVED_STORAGESHUTDOWN_COMPLETE,

    // d. We have notified observers that Places has closed the connection.

    NOTIFIED_OBSERVERS_PLACES_CONNECTION_CLOSED,

  };

  States State() {

    return mState;

  }

protected:

  // The blocker name, also used as barrier name.

  nsString mName;

  // The current state, see States.

  States mState;

  // The barrier optionally used to wait for clients.

  nsMainThreadPtrHandle<nsIAsyncShutdownBarrier> mBarrier;

  // The parent object who registered this as a blocker.

  nsMainThreadPtrHandle<nsIAsyncShutdownClient> mParentClient;

  // As tests may resurrect a dead `Database`, we use a counter to

  // give the instances of `PlacesShutdownBlocker` unique names.

  uint16_t mCounter;

  static uint16_t sCounter;

  static Atomic<bool> sIsStarted;

  virtual ~PlacesShutdownBlocker() {}

};

/**

 * Blocker also used to wait for clients, through an owned barrier.

 */

class ClientsShutdownBlocker final : public PlacesShutdownBlocker

{

public:

  NS_INLINE_DECL_REFCOUNTING_INHERITED(ClientsShutdownBlocker,

               PlacesShutdownBlocker)

  explicit ClientsShutdownBlocker();

  NS_IMETHOD Done() override;

private:

  ~ClientsShutdownBlocker() {}

};

/**

 * Blocker used to wait when closing the database connection.

 */

class ConnectionShutdownBlocker final : public PlacesShutdownBlocker

                                      , public mozIStorageCompletionCallback

{

public:

  NS_DECL_ISUPPORTS_INHERITED

  NS_DECL_MOZISTORAGECOMPLETIONCALLBACK

  explicit ConnectionShutdownBlocker(mozilla::places::Database* aDatabase);

  NS_IMETHOD Done() override;

private:

  ~ConnectionShutdownBlocker() {}

  // The owning database.

  // The cycle is broken in method Complete(), once the connection

  // has been closed by mozStorage.

  RefPtr<mozilla::places::Database> mDatabase;

};

} // namespace places

} // namespace mozilla

#endif // mozilla_places_Shutdown_h_