firebase-ios-sdk/FirebaseStorage/Sources/StorageTask.swift

// Copyright 2022 Google LLC
//
// 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 Foundation

import FirebaseStorageInternal

/**
 * A superclass to all Storage tasks, including `StorageUploadTask`
 * and `StorageDownloadTask`, to provide state transitions, event raising, and common storage
 * for metadata and errors.
 * Callbacks are always fired on the developer-specified callback queue.
 * If no queue is specified, it defaults to the main queue.
 * This class is not thread safe, so only call methods on the main thread.
 */
@objc(FIRStorageTask) open class StorageTask: NSObject {
  /**
   * An immutable view of the task and associated metadata, progress, error, etc.
   */
  @objc public var snapshot: StorageTaskSnapshot {
    return StorageTaskSnapshot(task: self)
  }

  // MARK: - Internal APIs

  internal let impl: FIRIMPLStorageTask

  internal init(impl: FIRIMPLStorageTask) {
    self.impl = impl
  }
}

/**
 * Defines task operations such as pause, resume, cancel, and enqueue for all tasks.
 * All tasks are required to implement enqueue, which begins the task, and may optionally
 * implement pause, resume, and cancel, which operate on the task to pause, resume, and cancel
 * operations.
 */
@objc(FIRStorageTaskManagement) public protocol StorageTaskManagement: NSObjectProtocol {
  /**
   * Prepares a task and begins execution.
   */
  @objc func enqueue() -> Void

  /**
   * Pauses a task currently in progress.
   */
  @objc optional func pause() -> Void

  /**
   * Cancels a task.
   */
  @objc optional func cancel() -> Void

  /**
   * Resumes a paused task.
   */
  @objc optional func resume() -> Void
}