text: // Copyright (c) Microsoft Corporation. All rights reserved.
  // Licensed under the MIT License.
  
  #import <Foundation/Foundation.h>
  
  @class MSAnalyticsAuthenticationProvider;
  
  /**
   * Completion handler that returns the authentication token and the expiry date.
   */
  typedef void (^MSAnalyticsAuthenticationProviderCompletionBlock)(NSString *token, NSDate *expiryDate);
  
  @protocol MSAnalyticsAuthenticationProviderDelegate <NSObject>
  
  /**
   * Required method that needs to be called from within your authentication flow to provide the authentication token and expiry date.
   *
   * @param authenticationProvider The authentication provider.
   * @param completionHandler The completion handler.
   */
  - (void)authenticationProvider:(MSAnalyticsAuthenticationProvider *)authenticationProvider
      acquireTokenWithCompletionHandler:(MSAnalyticsAuthenticationProviderCompletionBlock)completionHandler;
  
  @end
  