App Check: token update notifications (#764)

* AppCheck: token did change API and tests

* notification implementation and fixes

* Run ./scripts/style.sh

* Update comments

FirebaseAppCheck/Sources/Core/FIRAppCheck.m

@@ -38,6 +38,19 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
+/// A notification with the specified name is sent to the default notification center
+/// (`NotificationCenter.default`) each time a Firebase app check token is refreshed.
+/// The user info dictionary contains `kFIRAppCheckTokenNotificationKey` and
+/// `kFIRAppCheckAppNameNotificationKey` keys.
+const NSNotificationName FIRAppCheckAppCheckTokenDidChangeNotification =
+    @"FIRAppCheckAppCheckTokenDidChangeNotification";
+
+/// `userInfo` key for the `AppCheckToken` in `appCheckTokenRefreshNotification`.
+NSString *const kFIRAppCheckTokenNotificationKey = @"FIRAppCheckTokenNotificationKey";
+
+/// `userInfo` key for the `FirebaseApp.name` in `appCheckTokenRefreshNotification`.
+NSString *const kFIRAppCheckAppNameNotificationKey = @"FIRAppCheckAppNameNotificationKey";
+
 static id<FIRAppCheckProviderFactory> _providerFactory;
 
 static const NSTimeInterval kTokenExpirationThreshold = 5 * 60;  // 5 min.
@@ -50,6 +63,7 @@ @interface FIRAppCheck () <FIRLibrary, FIRAppCheckInterop>
 @property(nonatomic, readonly) NSString *appName;
 @property(nonatomic, readonly) id<FIRAppCheckProvider> appCheckProvider;
 @property(nonatomic, readonly) id<FIRAppCheckStorageProtocol> storage;
+@property(nonatomic, readonly) NSNotificationCenter *notificationCenter;
 
 @property(nonatomic, readonly, nullable) id<FIRAppCheckTokenRefresherProtocol> tokenRefresher;
 
@@ -115,19 +129,22 @@ - (nullable instancetype)initWithApp:(FIRApp *)app {
   return [self initWithAppName:app.name
               appCheckProvider:appCheckProvider
                        storage:storage
-                tokenRefresher:tokenRefresher];
+                tokenRefresher:tokenRefresher
+            notificationCenter:NSNotificationCenter.defaultCenter];
 }
 
 - (instancetype)initWithAppName:(NSString *)appName
                appCheckProvider:(id<FIRAppCheckProvider>)appCheckProvider
                         storage:(id<FIRAppCheckStorageProtocol>)storage
-                 tokenRefresher:(id<FIRAppCheckTokenRefresherProtocol>)tokenRefresher {
+                 tokenRefresher:(id<FIRAppCheckTokenRefresherProtocol>)tokenRefresher
+             notificationCenter:(NSNotificationCenter *)notificationCenter {
   self = [super init];
   if (self) {
     _appName = appName;
     _appCheckProvider = appCheckProvider;
     _storage = storage;
     _tokenRefresher = tokenRefresher;
+    _notificationCenter = notificationCenter;
 
     __auto_type __weak weakSelf = self;
     tokenRefresher.tokenRefreshHandler = ^(FIRAppCheckTokenRefreshCompletion _Nonnull completion) {
@@ -176,6 +193,18 @@ - (void)getTokenForcingRefresh:(BOOL)forcingRefresh
       });
 }
 
+- (nonnull NSString *)tokenDidChangeNotificationName {
+  return FIRAppCheckAppCheckTokenDidChangeNotification;
+}
+
+- (nonnull NSString *)notificationAppNameKey {
+  return kFIRAppCheckAppNameNotificationKey;
+}
+
+- (nonnull NSString *)notificationTokenKey {
+  return kFIRAppCheckTokenNotificationKey;
+}
+
 #pragma mark - FAA token cache
 
 - (FBLPromise<FIRAppCheckToken *> *)retrieveOrRefreshTokenForcingRefresh:(BOOL)forcingRefresh {
@@ -208,12 +237,16 @@ - (void)getTokenForcingRefresh:(BOOL)forcingRefresh
 }
 
 - (FBLPromise<FIRAppCheckToken *> *)refreshToken {
-  return
-      [FBLPromise wrapObjectOrErrorCompletion:^(
-                      FBLPromiseObjectOrErrorCompletion _Nonnull handler) {
-        [self.appCheckProvider getTokenWithCompletion:handler];
-      }].then(^id _Nullable(FIRAppCheckToken *_Nullable token) {
+  return [FBLPromise
+             wrapObjectOrErrorCompletion:^(FBLPromiseObjectOrErrorCompletion _Nonnull handler) {
+               [self.appCheckProvider getTokenWithCompletion:handler];
+             }]
+      .then(^id _Nullable(FIRAppCheckToken *_Nullable token) {
         return [self.storage setToken:token];
+      })
+      .then(^id _Nullable(FIRAppCheckToken *_Nullable token) {
+        [self postTokenUpdateNotificationWithToken:token];
+        return token;
       });
 }
 
@@ -230,6 +263,17 @@ - (void)periodicTokenRefreshWithCompletion:(FIRAppCheckTokenRefreshCompletion)co
       });
 }
 
+#pragma mark - Token update notification
+
+- (void)postTokenUpdateNotificationWithToken:(FIRAppCheckToken *)token {
+  [self.notificationCenter postNotificationName:FIRAppCheckAppCheckTokenDidChangeNotification
+                                         object:nil
+                                       userInfo:@{
+                                         kFIRAppCheckTokenNotificationKey : token.token,
+                                         kFIRAppCheckAppNameNotificationKey : self.appName
+                                       }];
+}
+
 @end
 
 NS_ASSUME_NONNULL_END

FirebaseAppCheck/Sources/Interop/FIRAppCheckInterop.h

@@ -31,6 +31,18 @@ typedef void (^FIRAppCheckTokenHandlerInterop)(id<FIRAppCheckTokenResultInterop>
                     completion:(FIRAppCheckTokenHandlerInterop)handler
     NS_SWIFT_NAME(getToken(forcingRefresh:completion:));
 
+/// A notification with the specified name is sent to the default notification center
+/// (`NotificationCenter.default`) each time a Firebase app check token is refreshed.
+/// The user info dictionary contains `-[self notificationTokenKey]` and
+/// `-[self notificationAppNameKey]` keys.
+- (NSString *)tokenDidChangeNotificationName;
+
+/// `userInfo` key for the FAC token in a notification for `tokenDidChangeNotificationName`.
+- (NSString *)notificationTokenKey;
+/// `userInfo` key for the `FirebaseApp.name` in a notification for
+/// `tokenDidChangeNotificationName`.
+- (NSString *)notificationAppNameKey;
+
 @end
 
 NS_ASSUME_NONNULL_END

FirebaseAppCheck/Tests/Unit/Core/FIRAppCheckTests.m

@@ -40,7 +40,8 @@ @interface FIRAppCheck (Tests) <FIRAppCheckInterop>
 - (instancetype)initWithAppName:(NSString *)appName
                appCheckProvider:(id<FIRAppCheckProvider>)appCheckProvider
                         storage:(id<FIRAppCheckStorageProtocol>)storage
-                 tokenRefresher:(id<FIRAppCheckTokenRefresherProtocol>)tokenRefresher;
+                 tokenRefresher:(id<FIRAppCheckTokenRefresherProtocol>)tokenRefresher
+             notificationCenter:(NSNotificationCenter *)notificationCenter;
 
 - (nullable instancetype)initWithApp:(FIRApp *)app;
 @end
@@ -51,6 +52,7 @@ @interface FIRAppCheckTests : XCTestCase
 @property(nonatomic) OCMockObject<FIRAppCheckStorageProtocol> *mockStorage;
 @property(nonatomic) OCMockObject<FIRAppCheckProvider> *mockAppCheckProvider;
 @property(nonatomic) OCMockObject<FIRAppCheckTokenRefresherProtocol> *mockTokenRefresher;
+@property(nonatomic) NSNotificationCenter *notificationCenter;
 @property(nonatomic) FIRAppCheck<FIRAppCheckInterop> *appCheck;
 
 @property(nonatomic, copy, nullable) FIRAppCheckTokenRefreshBlock tokenRefreshHandler;
@@ -66,13 +68,15 @@ - (void)setUp {
   self.mockStorage = OCMProtocolMock(@protocol(FIRAppCheckStorageProtocol));
   self.mockAppCheckProvider = OCMProtocolMock(@protocol(FIRAppCheckProvider));
   self.mockTokenRefresher = OCMProtocolMock(@protocol(FIRAppCheckTokenRefresherProtocol));
+  self.notificationCenter = [[NSNotificationCenter alloc] init];
 
   [self stubSetTokenRefreshHandler];
 
   self.appCheck = [[FIRAppCheck alloc] initWithAppName:self.appName
                                       appCheckProvider:self.mockAppCheckProvider
                                                storage:self.mockStorage
-                                        tokenRefresher:self.mockTokenRefresher];
+                                        tokenRefresher:self.mockTokenRefresher
+                                    notificationCenter:self.notificationCenter];
 }
 
 - (void)tearDown {
@@ -164,7 +168,11 @@ - (void)testGetToken_WhenNoCache_Success {
   OCMExpect([self.mockStorage setToken:tokenToReturn])
       .andReturn([FBLPromise resolvedWith:tokenToReturn]);
 
-  // 4. Request token.
+  // 4. Expect token update notification to be sent.
+  XCTestExpectation *notificationExpectation =
+      [self tokenUpdateNotificationWithExpectedToken:tokenToReturn.token];
+
+  // 5. Request token.
   XCTestExpectation *getTokenExpectation = [self expectationWithDescription:@"getToken"];
   [self.appCheck getTokenForcingRefresh:NO
                              completion:^(id<FIRAppCheckTokenResultInterop> tokenResult) {
@@ -175,8 +183,8 @@ - (void)testGetToken_WhenNoCache_Success {
                                XCTAssertNil(tokenResult.error);
                              }];
 
-  // 5. Wait for expectations and validate mocks.
-  [self waitForExpectations:@[ getTokenExpectation ] timeout:0.5];
+  // 6. Wait for expectations and validate mocks.
+  [self waitForExpectations:@[ notificationExpectation, getTokenExpectation ] timeout:0.5];
   OCMVerifyAll(self.mockStorage);
   OCMVerifyAll(self.mockAppCheckProvider);
 }
@@ -191,7 +199,11 @@ - (void)testGetToken_WhenCachedTokenIsValid_Success {
   // 2. Don't expect token requested from app check provider.
   OCMReject([self.mockAppCheckProvider getTokenWithCompletion:[OCMArg any]]);
 
-  // 3. Request token.
+  // 3. Don't expect token update notification to be sent.
+  XCTestExpectation *notificationExpectation = [self tokenUpdateNotificationWithExpectedToken:@""];
+  notificationExpectation.inverted = YES;
+
+  // 4. Request token.
   XCTestExpectation *getTokenExpectation = [self expectationWithDescription:@"getToken"];
   [self.appCheck getTokenForcingRefresh:NO
                              completion:^(id<FIRAppCheckTokenResultInterop> tokenResult) {
@@ -201,8 +213,8 @@ - (void)testGetToken_WhenCachedTokenIsValid_Success {
                                XCTAssertNil(tokenResult.error);
                              }];
 
-  // 4. Wait for expectations and validate mocks.
-  [self waitForExpectations:@[ getTokenExpectation ] timeout:0.5];
+  // 5. Wait for expectations and validate mocks.
+  [self waitForExpectations:@[ notificationExpectation, getTokenExpectation ] timeout:0.5];
   OCMVerifyAll(self.mockStorage);
   OCMVerifyAll(self.mockAppCheckProvider);
 }
@@ -221,7 +233,11 @@ - (void)testGetTokenForcingRefresh_WhenCachedTokenIsValid_Success {
   OCMExpect([self.mockStorage setToken:tokenToReturn])
       .andReturn([FBLPromise resolvedWith:tokenToReturn]);
 
-  // 4. Request token.
+  // 4. Expect token update notification to be sent.
+  XCTestExpectation *notificationExpectation =
+      [self tokenUpdateNotificationWithExpectedToken:tokenToReturn.token];
+
+  // 5. Request token.
   XCTestExpectation *getTokenExpectation = [self expectationWithDescription:@"getToken"];
   [self.appCheck getTokenForcingRefresh:YES
                              completion:^(id<FIRAppCheckTokenResultInterop> tokenResult) {
@@ -232,8 +248,8 @@ - (void)testGetTokenForcingRefresh_WhenCachedTokenIsValid_Success {
                                XCTAssertNil(tokenResult.error);
                              }];
 
-  // 5. Wait for expectations and validate mocks.
-  [self waitForExpectations:@[ getTokenExpectation ] timeout:0.5];
+  // 6. Wait for expectations and validate mocks.
+  [self waitForExpectations:@[ notificationExpectation, getTokenExpectation ] timeout:0.5];
   OCMVerifyAll(self.mockStorage);
   OCMVerifyAll(self.mockAppCheckProvider);
 }
@@ -255,7 +271,11 @@ - (void)testGetToken_WhenCachedTokenExpired_Success {
   OCMExpect([self.mockStorage setToken:tokenToReturn])
       .andReturn([FBLPromise resolvedWith:tokenToReturn]);
 
-  // 4. Request token.
+  // 4. Expect token update notification to be sent.
+  XCTestExpectation *notificationExpectation =
+      [self tokenUpdateNotificationWithExpectedToken:tokenToReturn.token];
+
+  // 5. Request token.
   XCTestExpectation *getTokenExpectation = [self expectationWithDescription:@"getToken"];
   [self.appCheck getTokenForcingRefresh:NO
                              completion:^(id<FIRAppCheckTokenResultInterop> tokenResult) {
@@ -265,8 +285,8 @@ - (void)testGetToken_WhenCachedTokenExpired_Success {
                                XCTAssertNil(tokenResult.error);
                              }];
 
-  // 5. Wait for expectations and validate mocks.
-  [self waitForExpectations:@[ getTokenExpectation ] timeout:0.5];
+  // 6. Wait for expectations and validate mocks.
+  [self waitForExpectations:@[ notificationExpectation, getTokenExpectation ] timeout:0.5];
   OCMVerifyAll(self.mockStorage);
   OCMVerifyAll(self.mockAppCheckProvider);
 }
@@ -287,7 +307,11 @@ - (void)testGetToken_AppCheckProviderError {
   // 3. Don't expect token requested from app check provider.
   OCMReject([self.mockAppCheckProvider getTokenWithCompletion:[OCMArg any]]);
 
-  // 4. Request token.
+  // 4. Don't expect token update notification to be sent.
+  XCTestExpectation *notificationExpectation = [self tokenUpdateNotificationWithExpectedToken:@""];
+  notificationExpectation.inverted = YES;
+
+  // 5. Request token.
   XCTestExpectation *getTokenExpectation = [self expectationWithDescription:@"getToken"];
   [self.appCheck
       getTokenForcingRefresh:NO
@@ -302,8 +326,8 @@ - (void)testGetToken_AppCheckProviderError {
                     XCTAssertEqualObjects(result.error, providerError);
                   }];
 
-  // 5. Wait for expectations and validate mocks.
-  [self waitForExpectations:@[ getTokenExpectation ] timeout:0.5];
+  // 6. Wait for expectations and validate mocks.
+  [self waitForExpectations:@[ notificationExpectation, getTokenExpectation ] timeout:0.5];
   OCMVerifyAll(self.mockStorage);
   OCMVerifyAll(self.mockAppCheckProvider);
 }
@@ -325,7 +349,11 @@ - (void)testTokenRefreshTriggeredAndRefreshSuccess {
   OCMExpect([self.mockStorage setToken:tokenToReturn])
       .andReturn([FBLPromise resolvedWith:tokenToReturn]);
 
-  // 4. Trigger refresh and expect the result.
+  // 4. Expect token update notification to be sent.
+  XCTestExpectation *notificationExpectation =
+      [self tokenUpdateNotificationWithExpectedToken:tokenToReturn.token];
+
+  // 5. Trigger refresh and expect the result.
   if (self.tokenRefreshHandler == nil) {
     XCTFail(@"`tokenRefreshHandler` must be not `nil`.");
     return;
@@ -338,7 +366,7 @@ - (void)testTokenRefreshTriggeredAndRefreshSuccess {
     XCTAssertTrue(success);
   });
 
-  [self waitForExpectations:@[ completionExpectation ] timeout:0.5];
+  [self waitForExpectations:@[ notificationExpectation, completionExpectation ] timeout:0.5];
   OCMVerifyAll(self.mockStorage);
   OCMVerifyAll(self.mockAppCheckProvider);
 }
@@ -355,7 +383,11 @@ - (void)testTokenRefreshTriggeredAndRefreshError {
   // 3. Don't expect token requested from app check provider.
   OCMReject([self.mockAppCheckProvider getTokenWithCompletion:[OCMArg any]]);
 
-  // 4. Trigger refresh and expect the result.
+  // 4. Don't expect token update notification to be sent.
+  XCTestExpectation *notificationExpectation = [self tokenUpdateNotificationWithExpectedToken:@""];
+  notificationExpectation.inverted = YES;
+
+  // 5. Trigger refresh and expect the result.
   if (self.tokenRefreshHandler == nil) {
     XCTFail(@"`tokenRefreshHandler` must be not `nil`.");
     return;
@@ -368,11 +400,21 @@ - (void)testTokenRefreshTriggeredAndRefreshError {
     XCTAssertFalse(success);
   });
 
-  [self waitForExpectations:@[ completionExpectation ] timeout:0.5];
+  [self waitForExpectations:@[ notificationExpectation, completionExpectation ] timeout:0.5];
   OCMVerifyAll(self.mockStorage);
   OCMVerifyAll(self.mockAppCheckProvider);
 }
 
+#pragma mark - Token update notifications
+
+- (void)testTokenUpdateNotificationKeys {
+  XCTAssertEqualObjects([self.appCheck tokenDidChangeNotificationName],
+                        @"FIRAppCheckAppCheckTokenDidChangeNotification");
+  XCTAssertEqualObjects([self.appCheck notificationAppNameKey],
+                        @"FIRAppCheckAppNameNotificationKey");
+  XCTAssertEqualObjects([self.appCheck notificationTokenKey], @"FIRAppCheckTokenNotificationKey");
+}
+
 #pragma mark - Helpers
 
 - (void)stubSetTokenRefreshHandler {
@@ -383,4 +425,22 @@ - (void)stubSetTokenRefreshHandler {
   OCMExpect([self.mockTokenRefresher setTokenRefreshHandler:arg]);
 }
 
+- (XCTestExpectation *)tokenUpdateNotificationWithExpectedToken:(NSString *)expectedToken {
+  XCTestExpectation *expectation =
+      [self expectationForNotification:[self.appCheck tokenDidChangeNotificationName]
+                                object:nil
+                    notificationCenter:self.notificationCenter
+                               handler:^BOOL(NSNotification *_Nonnull notification) {
+                                 XCTAssertEqualObjects(
+                                     notification.userInfo[[self.appCheck notificationAppNameKey]],
+                                     self.appName);
+                                 XCTAssertEqualObjects(
+                                     notification.userInfo[[self.appCheck notificationTokenKey]],
+                                     expectedToken);
+                                 return YES;
+                               }];
+
+  return expectation;
+}
+
 @end

SharedTestUtilities/AppCheckFake/FIRAppCheckFake.m

@@ -35,4 +35,16 @@ - (void)getTokenForcingRefresh:(BOOL)forcingRefresh
   });
 }
 
+- (nonnull NSString *)notificationAppNameKey {
+  return @"FakeAppCheckTokenDidChangeNotification";
+}
+
+- (nonnull NSString *)notificationTokenKey {
+  return @"FakeTokenNotificationKey";
+}
+
+- (nonnull NSString *)tokenDidChangeNotificationName {
+  return @"FakeAppCheckTokenDidChangeNotification";
+}
+
 @end