Chapter 11 - Chat App/ChatAppFinished/Pods/FirebaseAuth/Firebase/Auth/Source/AuthProvider/GameCenter/FIRGameCenterAuthProvider.m
/*
 * Copyright 2018 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 "FIRGameCenterAuthProvider.h"

#import <GameKit/GameKit.h>

#import "FIRAuthErrorUtils.h"
#import "FIRAuthExceptionUtils.h"
#import "FIRGameCenterAuthCredential.h"

NS_ASSUME_NONNULL_BEGIN

@implementation FIRGameCenterAuthProvider

- (instancetype)init {
  [FIRAuthExceptionUtils raiseMethodNotImplementedExceptionWithReason:
      @"This class is not meant to be initialized."];
  return nil;
}

+ (void)getCredentialWithCompletion:(FIRGameCenterCredentialCallback)completion {
  /**
   Linking GameKit.framework without using it on macOS results in App Store rejection.
   Thus we don't link GameKit.framework to our SDK directly. `optionalLocalPlayer` is used for
   checking whether the APP that consuming our SDK has linked GameKit.framework. If not, a
   `GameKitNotLinkedError` will be raised.
   **/
  GKLocalPlayer * _Nullable optionalLocalPlayer = [[NSClassFromString(@"GKLocalPlayer") alloc] init];

  if (!optionalLocalPlayer) {
    if (completion) {
      completion(nil, [FIRAuthErrorUtils gameKitNotLinkedError]);
    }
    return;
  }

  __weak GKLocalPlayer *localPlayer = [[optionalLocalPlayer class] localPlayer];
  if (!localPlayer.isAuthenticated) {
    if (completion) {
      completion(nil, [FIRAuthErrorUtils localPlayerNotAuthenticatedError]);
    }
    return;
  }

  [localPlayer generateIdentityVerificationSignatureWithCompletionHandler:
   ^(NSURL *publicKeyURL, NSData *signature, NSData *salt, uint64_t timestamp, NSError *error) {
     if (error) {
       if (completion) {
         completion(nil, error);
       }
     } else {
       if (completion) {
         /**
          @c `localPlayer.alias` is actually the displayname needed, instead of
          `localPlayer.displayname`. For more information, check
          https://developer.apple.com/documentation/gamekit/gkplayer
          **/
         NSString *displayName = localPlayer.alias;
         FIRGameCenterAuthCredential *credential =
             [[FIRGameCenterAuthCredential alloc] initWithPlayerID:localPlayer.playerID
                                                      publicKeyURL:publicKeyURL
                                                         signature:signature
                                                              salt:salt
                                                         timestamp:timestamp
                                                       displayName:displayName];
         completion(credential, nil);
       }
     }
   }];
}

@end

NS_ASSUME_NONNULL_END
