Connect4 — 09: כניסה עם חשבון Google

     }
 }
 
 dependencies {
+    implementation("androidx.credentials:credentials:1.3.0")
+    implementation("androidx.credentials:credentials-play-services-auth:1.3.0")
+    implementation("com.google.android.libraries.identity.googleid:googleid:1.1.1")
     implementation(platform("com.google.firebase:firebase-bom:34.19.0"))
     implementation("com.google.firebase:firebase-auth")
     implementation("com.google.ai.edge.litert:litert:2.1.0")
     implementation("androidx.lifecycle:lifecycle-viewmodel:2.10.0")

 package com.example.connect4.multiplayer;
 import com.google.firebase.auth.FirebaseAuth;
 import com.google.firebase.auth.FirebaseUser;
+import com.google.firebase.auth.GoogleAuthProvider;
 
 /** Owns Firebase authentication and closes its listeners explicitly. */
 public final class MultiplayerRepository {
     private final FirebaseAuth auth;

         void onSuccess(T result);
         void onError(RepositoryError error);
     }
     public interface AuthListener { void onAuthChanged(String uid); }
+
+    /** Exchanges a Google ID token obtained by the Android credential UI for Firebase Auth. */
+    public void signInWithGoogle(String idToken, ResultCallback<String> callback) {
+        if (idToken == null || idToken.trim().isEmpty()) {
+            callback.onError(error(RepositoryError.Code.INVALID_ARGUMENT,
+                    "Google sign-in returned no ID token", null));
+            return;
+        }
+        auth.signInWithCredential(GoogleAuthProvider.getCredential(idToken.trim(), null))
+                .addOnSuccessListener(result -> callback.onSuccess(result.getUser().getUid()))
+                .addOnFailureListener(exception -> callback.onError(firebaseError(exception, null)));
+    }
 }

     public boolean authPending;
     public String onlineMessage = "";
     public String onlineUid;
     public long onlineGeneration;
+    public long googleRequestGeneration;
     public Runnable refreshOnline;
     public String selectedModelId = ModelCatalog.DEFAULT_MODEL_ID;
 
     public GameEngine engine = new GameEngine();

         android:layout_width="match_parent" android:layout_height="wrap_content" android:visibility="gone">
         <TextView android:id="@+id/onlineStatus" android:layout_width="match_parent" android:layout_height="wrap_content" />
         <LinearLayout android:id="@+id/authPanel" android:orientation="vertical"
             android:layout_width="match_parent" android:layout_height="wrap_content">
+            <Button android:id="@+id/googleSignIn" android:layout_width="match_parent"
+                android:layout_height="wrap_content" android:text="Continue with Google" />
             <EditText android:id="@+id/email" android:layout_width="match_parent" android:layout_height="wrap_content"
                 android:hint="Email" android:inputType="textEmailAddress" android:autofillHints="emailAddress" />
             <EditText android:id="@+id/password" android:layout_width="match_parent" android:layout_height="wrap_content"
                 android:hint="Password" android:inputType="textPassword" android:autofillHints="password" android:saveEnabled="false" />

     private final ActivityMainBinding ui;
     private final GameSession session;
     private final Host host;
     private boolean active;
+    private final GoogleSignIn googleSignIn;
+    private boolean pickingGoogle;
     private MultiplayerRepository.Subscription auth = MultiplayerRepository.Subscription.EMPTY;
     private final Runnable refreshCallback = this::refreshScreen;
 
     OnlineController(android.app.Activity activity, ActivityMainBinding ui, GameSession session, Host host) {
         this.ui=ui; this.session=session; this.host=host;
+        googleSignIn=new GoogleSignIn(activity);
+        ui.googleSignIn.setOnClickListener(v -> authenticateGoogle());
         ui.signIn.setOnClickListener(v -> authenticate(false));
         ui.signUp.setOnClickListener(v -> authenticate(true));
         ui.signOut.setOnClickListener(v -> {
             session.onlineGeneration++;
             if (session.repository != null) session.repository.signOut();
+            googleSignIn.clearSession();
             refreshScreen();
         });
     }

     }
     private void refreshScreen() { if (active) host.changed(); }
     private void refreshLatestScreen() { if (session.refreshOnline!=null) session.refreshOnline.run(); }
     private void showError(RepositoryError error) { session.onlineMessage=error.getMessage(); }
-    void destroy() { }
+    void destroy() {
+        if (pickingGoogle) {
+            session.googleRequestGeneration++;
+            session.authPending = false;
+            pickingGoogle = false;
+        }
+        googleSignIn.cancel();
+    }
 
     /** Shows the session's identity and enables only available actions. */
     void render() {
         boolean signedIn=session.repository!=null && session.repository.currentUid()!=null;
         ui.authPanel.setVisibility(signedIn ? View.GONE : View.VISIBLE);
         ui.signOut.setVisibility(signedIn ? View.VISIBLE : View.GONE);
         ui.signIn.setEnabled(session.repository!=null && !session.authPending);
         ui.signUp.setEnabled(session.repository!=null && !session.authPending);
+        ui.googleSignIn.setEnabled(session.repository!=null && !session.authPending);
         ui.onlineStatus.setText(signedIn ? "Signed in: " + session.repository.currentUid() : session.onlineMessage);
     }
 
     private void authenticate(boolean create) {

         if (create) session.repository.createAccount(email, password, callback);
         else session.repository.signIn(email, password, callback);
         host.changed();
     }
+
+    private void authenticateGoogle() {
+        if (session.repository == null || session.authPending) return;
+        session.authPending = true;
+        pickingGoogle = true;
+        long request = ++session.googleRequestGeneration;
+        long generation = session.onlineGeneration;
+        googleSignIn.signIn(new GoogleSignIn.Callback() {
+            @Override public void token(String token) {
+                if (request != session.googleRequestGeneration) return;
+                pickingGoogle = false;
+                if (generation != session.onlineGeneration || session.mode != GameSession.MODE_ONLINE) {
+                    session.authPending = false;
+                    refreshLatestScreen();
+                    return;
+                }
+                session.repository.signInWithGoogle(token, new MultiplayerRepository.ResultCallback<String>() {
+                    @Override public void onSuccess(String uid) {
+                        session.authPending = false;
+                        session.onlineMessage = "Signed in with Google";
+                        refreshLatestScreen();
+                    }
+                    @Override public void onError(RepositoryError error) {
+                        session.authPending = false;
+                        showError(error);
+                        refreshLatestScreen();
+                    }
+                });
+            }
+            @Override public void error(String message) {
+                if (request != session.googleRequestGeneration) return;
+                pickingGoogle = false;
+                session.authPending = false;
+                session.onlineMessage = message;
+                refreshLatestScreen();
+            }
+        });
+        host.changed();
+    }
 }