feat(core): add util method for fetching active scenes by selector

FirebaseCore/Extension/FirebaseCoreInternal.h

@@ -24,5 +24,6 @@
 #import "FIRHeartbeatLogger.h"
 #import "FIRLibrary.h"
 #import "FIRLogger.h"
+#import "UIApplication+FIRSceneDelegateFinder.h"
 
 #endif  // FIREBASECORE_FIREBASECOREINTERNAL_H

FirebaseCore/Extension/UIApplication+FIRSceneDelegateFinder.h

@@ -0,0 +1,62 @@
+// Copyright 2026 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 <TargetConditionals.h>
+#if TARGET_OS_IOS || TARGET_OS_TV || TARGET_OS_VISION
+
+#import <UIKit/UIKit.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface UIApplication (FIRSceneDelegateFinder)
+
+/**
+ Iterates through the connectedScenes of the specified application instance to find a
+ foreground scene whose delegate responds to the specified selector. Prioritizes
+ `UISceneActivationStateForegroundActive` scenes over `UISceneActivationStateForegroundInactive`
+ scenes.
+
+ Note that a scene in the `ForegroundInactive` state is visible and loaded
+ in the foreground, but is temporarily not receiving touch events for whatever
+ reason (eg; because a system dialog, permission prompt, or notification center
+ overlay is covering it). It's totally valid to send events through these scenes,
+ so we fall back to checking if these scenes exist if we don't find a better
+ alternative (ie; a scene that's in the foregound _and_ active).
+
+ ### Usage Example
+ ```objc
+ SEL selector = @selector(scene:continueUserActivity:);
+ UIScene *targetScene = [UIApplication
+    fir_findForegroundSceneWithDelegateRespondingToSelector:selector
+                                            onApplication:self.mainApplication];
+
+ if (targetScene) {
+  [targetScene.delegate scene:targetScene continueUserActivity:userActivity];
+ }                               
+ ```
+
+ @param selector The selector to find a scene delegate for (e.g.
+ `@selector(scene:continueUserActivity:)`).
+ @param application UIApplication instance to search for scenes from.
+ @return The matching UIScene instance, or nil if no matching scene delegate is found.
+ */
++ (nullable UIScene *)
+    fir_findForegroundSceneWithDelegateRespondingToSelector:(SEL)selector
+                                              onApplication:(nullable UIApplication *)application;
+
+@end
+
+NS_ASSUME_NONNULL_END
+
+#endif  // TARGET_OS_IOS || TARGET_OS_TV || TARGET_OS_VISION

FirebaseCore/Sources/UIApplication+FIRSceneDelegateFinder.m

@@ -0,0 +1,54 @@
+// Copyright 2026 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 <TargetConditionals.h>
+#if TARGET_OS_IOS || TARGET_OS_TV || TARGET_OS_VISION
+
+#import "FirebaseCore/Extension/UIApplication+FIRSceneDelegateFinder.h"
+
+@implementation UIApplication (FIRSceneDelegateFinder)
+
++ (nullable UIScene *)fir_findForegroundSceneWithDelegateRespondingToSelector:(SEL)selector {
+  return [self fir_findForegroundSceneWithDelegateRespondingToSelector:selector onApplication:nil];
+}
+
++ (nullable UIScene *)
+    fir_findForegroundSceneWithDelegateRespondingToSelector:(SEL)selector
+                                              onApplication:(UIApplication *)application {
+  UIApplication *app = application;
+
+  if (!app) {
+    return nil;
+  }
+
+  UIScene *targetScene = nil;
+
+  for (UIScene *scene in app.connectedScenes) {
+    id<UISceneDelegate> sceneDelegate = scene.delegate;
+    if ([sceneDelegate respondsToSelector:selector]) {
+      if (scene.activationState == UISceneActivationStateForegroundActive) {
+        targetScene = scene;
+        break;
+      } else if (scene.activationState == UISceneActivationStateForegroundInactive) {
+        targetScene = scene;
+      }
+    }
+  }
+
+  return targetScene;
+}
+
+@end
+
+#endif  // TARGET_OS_IOS || TARGET_OS_TV || TARGET_OS_VISION

FirebaseCore/Tests/Unit/UIApplication+FIRSceneDelegateFinderTests.m

@@ -0,0 +1,109 @@
+// Copyright 2026 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 <TargetConditionals.h>
+#if TARGET_OS_IOS || TARGET_OS_TV || TARGET_OS_VISION
+
+#import "FirebaseCore/Tests/Unit/FIRTestCase.h"
+
+#import "FirebaseCore/Extension/UIApplication+FIRSceneDelegateFinder.h"
+
+@interface MockSceneDelegate : NSObject <UISceneDelegate>
+- (void)scene:(UIScene *)scene continueUserActivity:(NSUserActivity *)userActivity;
+@end
+
+@implementation MockSceneDelegate
+- (void)scene:(UIScene *)scene continueUserActivity:(NSUserActivity *)userActivity {
+}
+@end
+
+@interface UIApplication_FIRSceneDelegateFinderTests : FIRTestCase
+@property(nonatomic, strong) id mockApplication;
+@end
+
+@implementation UIApplication_FIRSceneDelegateFinderTests
+
+- (void)setUp {
+  [super setUp];
+  self.mockApplication = OCMClassMock([UIApplication class]);
+}
+
+- (void)tearDown {
+  [self.mockApplication stopMocking];
+  [super tearDown];
+}
+
+- (void)testNoMatchingScene {
+  id mockScene = OCMClassMock([UIScene class]);
+  OCMStub([mockScene activationState]).andReturn(UISceneActivationStateForegroundActive);
+  // Delegate does NOT respond to target selector
+  id mockDelegate = OCMProtocolMock(@protocol(UIApplicationDelegate));
+  OCMStub([mockScene delegate]).andReturn(mockDelegate);
+
+  NSSet *connectedScenes = [NSSet setWithObject:mockScene];
+  OCMStub([self.mockApplication connectedScenes]).andReturn(connectedScenes);
+
+  UIScene *result = [UIApplication
+      fir_findForegroundSceneWithDelegateRespondingToSelector:@selector(scene:continueUserActivity:)
+                                                onApplication:self.mockApplication];
+  XCTAssertNil(result);
+}
+
+- (void)testForegroundInactiveFallback {
+  // Scene A is background
+  id mockSceneA = OCMClassMock([UIScene class]);
+  OCMStub([mockSceneA activationState]).andReturn(UISceneActivationStateBackground);
+  id mockDelegateA = OCMClassMock([MockSceneDelegate class]);
+  OCMStub([mockSceneA delegate]).andReturn(mockDelegateA);
+
+  // Scene B is foreground inactive (implements selector)
+  id mockSceneB = OCMClassMock([UIScene class]);
+  OCMStub([mockSceneB activationState]).andReturn(UISceneActivationStateForegroundInactive);
+  id mockDelegateB = OCMClassMock([MockSceneDelegate class]);
+  OCMStub([mockSceneB delegate]).andReturn(mockDelegateB);
+
+  NSSet *connectedScenes = [NSSet setWithObjects:mockSceneA, mockSceneB, nil];
+  OCMStub([self.mockApplication connectedScenes]).andReturn(connectedScenes);
+
+  UIScene *result = [UIApplication
+      fir_findForegroundSceneWithDelegateRespondingToSelector:@selector(scene:continueUserActivity:)
+                                                onApplication:self.mockApplication];
+  XCTAssertEqual(result, mockSceneB);
+}
+
+- (void)testForegroundActivePriority {
+  // Scene A is foreground inactive
+  id mockSceneA = OCMClassMock([UIScene class]);
+  OCMStub([mockSceneA activationState]).andReturn(UISceneActivationStateForegroundInactive);
+  id mockDelegateA = OCMClassMock([MockSceneDelegate class]);
+  OCMStub([mockSceneA delegate]).andReturn(mockDelegateA);
+
+  // Scene B is foreground active
+  id mockSceneB = OCMClassMock([UIScene class]);
+  OCMStub([mockSceneB activationState]).andReturn(UISceneActivationStateForegroundActive);
+  id mockDelegateB = OCMClassMock([MockSceneDelegate class]);
+  OCMStub([mockSceneB delegate]).andReturn(mockDelegateB);
+
+  NSSet *connectedScenes = [NSSet setWithObjects:mockSceneA, mockSceneB, nil];
+  OCMStub([self.mockApplication connectedScenes]).andReturn(connectedScenes);
+
+  UIScene *result = [UIApplication
+      fir_findForegroundSceneWithDelegateRespondingToSelector:@selector(scene:continueUserActivity:)
+                                                onApplication:self.mockApplication];
+  XCTAssertEqual(result, mockSceneB);
+}
+
+@end
+
+#endif  // TARGET_OS_IOS || TARGET_OS_TV || TARGET_OS_VISION