Add the GIDEMMAlertPresenter protocol with a fake

GoogleSignIn/Sources/GIDEMMAlertPresenter/API/GIDEMMAlertPresenter.h

@@ -0,0 +1,42 @@
+/*
+ * 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_MACCATALYST
+
+#import <Foundation/Foundation.h>
+#import <UIKit/UIKit.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+/// Shows and hides the alert that `GIDEMMErrorHandler` uses to explain an EMM error to the user.
+///
+/// Production code uses `GIDEMMAlertWindowPresenter`; tests use `GIDFakeEMMAlertPresenter`.
+@protocol GIDEMMAlertPresenter <NSObject>
+
+/// Presents `alert` above `keyWindow`. Must be called on the main thread.
+- (void)presentAlert:(UIAlertController *)alert overKeyWindow:(UIWindow *)keyWindow;
+
+/// Tears down whatever `-presentAlert:overKeyWindow:` set up and makes that call's `keyWindow` the
+/// key window again. Must be called on the main thread.
+- (void)dismissAlert;
+
+@end
+
+NS_ASSUME_NONNULL_END
+
+#endif // TARGET_OS_IOS && !TARGET_OS_MACCATALYST

GoogleSignIn/Sources/GIDEMMAlertPresenter/Fake/GIDFakeEMMAlertPresenter.h

@@ -0,0 +1,45 @@
+/*
+ * 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_MACCATALYST
+
+#import <Foundation/Foundation.h>
+#import <UIKit/UIKit.h>
+
+#import "GoogleSignIn/Sources/GIDEMMAlertPresenter/API/GIDEMMAlertPresenter.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+/// An in-memory `GIDEMMAlertPresenter` for tests. Records the alert instead of showing it.
+@interface GIDFakeEMMAlertPresenter : NSObject <GIDEMMAlertPresenter>
+
+/// The alert passed to the most recent `-presentAlert:overKeyWindow:` that has not yet been
+/// dismissed, or nil.
+@property(nonatomic, readonly, nullable) UIAlertController *presentedAlert;
+
+/// The key window passed to the most recent `-presentAlert:overKeyWindow:`, or nil.
+@property(nonatomic, readonly, nullable) UIWindow *presentedOverKeyWindow;
+
+/// The number of times `-dismissAlert` has been called.
+@property(nonatomic, readonly) NSUInteger dismissCount;
+
+@end
+
+NS_ASSUME_NONNULL_END
+
+#endif // TARGET_OS_IOS && !TARGET_OS_MACCATALYST

GoogleSignIn/Sources/GIDEMMAlertPresenter/Fake/GIDFakeEMMAlertPresenter.m

@@ -0,0 +1,41 @@
+/*
+ * 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_MACCATALYST
+
+#import "GoogleSignIn/Sources/GIDEMMAlertPresenter/Fake/GIDFakeEMMAlertPresenter.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+@implementation GIDFakeEMMAlertPresenter
+
+- (void)presentAlert:(UIAlertController *)alert overKeyWindow:(UIWindow *)keyWindow {
+  _presentedAlert = alert;
+  _presentedOverKeyWindow = keyWindow;
+}
+
+- (void)dismissAlert {
+  _presentedAlert = nil;
+  _dismissCount++;
+}
+
+@end
+
+NS_ASSUME_NONNULL_END
+
+#endif // TARGET_OS_IOS && !TARGET_OS_MACCATALYST

GoogleSignIn/Sources/GIDEMMAlertPresenter/Implementation/GIDEMMAlertWindowPresenter.h

@@ -0,0 +1,33 @@
+/*
+ * 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_MACCATALYST
+
+#import <Foundation/Foundation.h>
+
+#import "GoogleSignIn/Sources/GIDEMMAlertPresenter/API/GIDEMMAlertPresenter.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+/// Presents the EMM alert in a transparent `UIWindow` of its own at `UIWindowLevelAlert`.
+@interface GIDEMMAlertWindowPresenter : NSObject <GIDEMMAlertPresenter>
+@end
+
+NS_ASSUME_NONNULL_END
+
+#endif // TARGET_OS_IOS && !TARGET_OS_MACCATALYST

GoogleSignIn/Sources/GIDEMMAlertPresenter/Implementation/GIDEMMAlertWindowPresenter.m

@@ -0,0 +1,66 @@
+/*
+ * 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_MACCATALYST
+
+#import "GoogleSignIn/Sources/GIDEMMAlertPresenter/Implementation/GIDEMMAlertWindowPresenter.h"
+
+#import <UIKit/UIKit.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@implementation GIDEMMAlertWindowPresenter {
+  // The transparent window the alert is presented in while it is showing, or nil.
+  UIWindow *_alertWindow;
+  // The window that was key before the alert was shown; made key again on dismissal.
+  UIWindow *_keyWindow;
+}
+
+- (void)presentAlert:(UIAlertController *)alert overKeyWindow:(UIWindow *)keyWindow {
+  _keyWindow = keyWindow;
+  UIWindow *alertWindow;
+  if (keyWindow.windowScene) {
+    alertWindow = [[UIWindow alloc] initWithWindowScene:keyWindow.windowScene];
+  }
+  if (!alertWindow) {
+    CGRect keyWindowBounds = CGRectIsEmpty(keyWindow.bounds) ?
+        keyWindow.bounds : [UIScreen mainScreen].bounds;
+    alertWindow = [[UIWindow alloc] initWithFrame:keyWindowBounds];
+  }
+  alertWindow.backgroundColor = [UIColor clearColor];
+  alertWindow.rootViewController = [[UIViewController alloc] init];
+  alertWindow.rootViewController.view.backgroundColor = [UIColor clearColor];
+  alertWindow.windowLevel = UIWindowLevelAlert;
+  [alertWindow makeKeyAndVisible];
+  _alertWindow = alertWindow;
+  [alertWindow.rootViewController presentViewController:alert animated:YES completion:nil];
+}
+
+- (void)dismissAlert {
+  _alertWindow.hidden = YES;
+  _alertWindow.rootViewController = nil;
+  _alertWindow = nil;
+  [_keyWindow makeKeyAndVisible];
+  _keyWindow = nil;
+}
+
+@end
+
+NS_ASSUME_NONNULL_END
+
+#endif // TARGET_OS_IOS && !TARGET_OS_MACCATALYST