text: /*
   * Copyright 2017 Google
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  #import "FIRStorageTask.h"
  
  NS_ASSUME_NONNULL_BEGIN
  
  @class FIRStorageReference;
  @class FIRStorageTaskSnapshot;
  
  /**
   * Extends FIRStorageTask to provide observable semantics such as adding and removing observers.
   * Observers produce a FIRStorageHandle, which is used to keep track of and remove specific
   * observers at a later date.
   * This class is currently not thread safe and can only be called on the main thread.
   */
  NS_SWIFT_NAME(StorageObservableTask)
  @interface FIRStorageObservableTask : FIRStorageTask
  
  /**
   * Observes changes in the upload status: Resume, Pause, Progress, Success, and Failure.
   * @param status The FIRStorageTaskStatus change to observe.
   * @param handler A callback that fires every time the status event occurs,
   * returns a FIRStorageTaskSnapshot containing the state of the task.
   * @return A task handle that can be used to remove the observer at a later date.
   */
  - (FIRStorageHandle)observeStatus:(FIRStorageTaskStatus)status
                            handler:(void (^)(FIRStorageTaskSnapshot *snapshot))handler;
  
  /**
   * Removes the single observer with the provided handle.
   * @param handle The handle of the task to remove.
   */
  - (void)removeObserverWithHandle:(FIRStorageHandle)handle;
  
  /**
   * Removes all observers for a single status.
   * @param status A FIRStorageTaskStatus to remove listeners for.
   */
  - (void)removeAllObserversForStatus:(FIRStorageTaskStatus)status;
  
  /**
   * Removes all observers.
   */
  - (void)removeAllObservers;
  
  @end
  
  NS_ASSUME_NONNULL_END
  