text: // Copyright 2016 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #ifndef IOS_CHROME_BROWSER_UI_NETWORK_ACTIVITY_INDICATOR_MANAGER_H_
  #define IOS_CHROME_BROWSER_UI_NETWORK_ACTIVITY_INDICATOR_MANAGER_H_
  
  #import <Foundation/Foundation.h>
  
  // This class controls access to the network activity indicator across the
  // app. It provides a simple interface for clients to indicate they are
  // starting a network task and they would like the indicator shown, and to
  // indicate they have finished a network task.
  //
  // Clients are required to pass an NSString* to each method to identify
  // themselves. Separating clients into groups prevents a client from "stopping"
  // requests from other clients on accident, and makes those bugs easier to
  // track down. Specifically, the manager will immediately fail if the number
  // of tasks stopped for a group ever exceeds the number of tasks started for
  // that group. Clients are responsible for namespacing their group strings
  // properly. All methods must be called on the UI thread.
  @interface NetworkActivityIndicatorManager : NSObject
  
  // Returns the singleton NetworkActivityIndicatorManager.
  + (NetworkActivityIndicatorManager*)sharedInstance;
  
  // Begins a single network task. The network activity indicator is guaranteed
  // to be shown after this finishes (if it isn't already). |group| must be
  // non-nil.
  - (void)startNetworkTaskForGroup:(NSString*)group;
  
  // Stops a single network task. The network activity indicator may or may not
  // stop being shown once this finishes, depending on whether there are other
  // unstopped tasks or not. |group| must be non-nil, and have at least one
  // unstopped task.
  - (void)stopNetworkTaskForGroup:(NSString*)group;
  
  // A convenience method for starting multiple network tasks at once. |group|
  // must be non-nil. |numTasks| must be greater than 0.
  - (void)startNetworkTasks:(NSUInteger)numTasks forGroup:(NSString*)group;
  
  // A convenience method for stopping multiple network tasks at once. |group|
  // must be non-nil. |numTasks| must be greater than 0, and |numTasks| must be
  // less than or equal to the number of unstopped tasks in |group|.
  - (void)stopNetworkTasks:(NSUInteger)numTasks forGroup:(NSString*)group;
  
  // A convenience method for stopping all network tasks for a group. |group|
  // must be non-nil. Can be called on any group at any time, regardless of
  // whether the group has any unstopped network tasks or not. Returns the number
  // of tasks stopped by this call.
  - (NSUInteger)clearNetworkTasksForGroup:(NSString*)group;
  
  // Returns the number of unstopped network tasks for |group|. |group| must be
  // non-nil. Can be called on any group at any time, regardless of whether the
  // group has any unstopped network tasks or not.
  - (NSUInteger)numNetworkTasksForGroup:(NSString*)group;
  
  // Returns the total number of unstopped network tasks, across all groups. This
  // method was added for testing only. Clients should never depend on this, and
  // should instead only be concerned with the number of unstopped network tasks
  // for the groups they control, which can be queried using
  // |-numNetworkTasksForGroup:|.
  - (NSUInteger)numTotalNetworkTasks;
  
  @end
  
  #endif  // IOS_CHROME_BROWSER_UI_NETWORK_ACTIVITY_INDICATOR_MANAGER_H_
  