Unified emulator settings for Database

firebase-common/src/androidTest/java/com/google/firebase/FirebaseAppTest.java

@@ -45,6 +45,9 @@
 import com.google.firebase.components.TestComponentOne;
 import com.google.firebase.components.TestComponentTwo;
 import com.google.firebase.components.TestUserAgentDependentComponent;
+import com.google.firebase.emulators.EmulatedServiceSettings;
+import com.google.firebase.emulators.EmulatorSettings;
+import com.google.firebase.emulators.FirebaseEmulator;
 import com.google.firebase.platforminfo.UserAgentPublisher;
 import com.google.firebase.testing.FirebaseAppRule;
 import java.lang.reflect.InvocationTargetException;
@@ -417,6 +420,45 @@ public void testDirectBoot_shouldPreserveDataCollectionAfterUnlock() {
     assertTrue(firebaseApp.isDataCollectionDefaultEnabled());
   }
 
+  @Test
+  public void testEnableEmulators_shouldAllowDoubleSetBeforeAccess() {
+    Context mockContext = createForwardingMockContext();
+    FirebaseApp firebaseApp = FirebaseApp.initializeApp(mockContext);
+
+    // A developer would call FirebaseDatabase.EMULATOR but we can't introduce that
+    // dependency for this test.
+    FirebaseEmulator emulator = FirebaseEmulator.forName("database");
+
+    EmulatedServiceSettings databaseSettings =
+        new EmulatedServiceSettings.Builder("10.0.2.2", 9000).build();
+    EmulatorSettings emulatorSettings =
+        new EmulatorSettings.Builder().addEmulatedService(emulator, databaseSettings).build();
+
+    // Set twice
+    firebaseApp.enableEmulators(emulatorSettings);
+    firebaseApp.enableEmulators(emulatorSettings);
+  }
+
+  @Test
+  public void testEnableEmulators_shouldThrowIfSetAfterAccess() {
+    Context mockContext = createForwardingMockContext();
+    FirebaseApp firebaseApp = FirebaseApp.initializeApp(mockContext);
+
+    FirebaseEmulator emulator = FirebaseEmulator.forName("database");
+
+    EmulatedServiceSettings databaseSettings =
+        new EmulatedServiceSettings.Builder("10.0.2.2", 9000).build();
+    EmulatorSettings emulatorSettings =
+        new EmulatorSettings.Builder().addEmulatedService(emulator, databaseSettings).build();
+    firebaseApp.enableEmulators(emulatorSettings);
+
+    // Access (as if from the Database SDK)
+    firebaseApp.getEmulatorSettings().getServiceSettings(emulator);
+
+    // Try to set again
+    assertThrows(IllegalStateException.class, () -> firebaseApp.enableEmulators(emulatorSettings));
+  }
+
   /** Returns mock context that forwards calls to targetContext and localBroadcastManager. */
   private Context createForwardingMockContext() {
     final UserManager spyUserManager = spy(targetContext.getSystemService(UserManager.class));

firebase-common/src/main/java/com/google/firebase/FirebaseApp.java

@@ -44,6 +44,8 @@
 import com.google.firebase.components.ComponentRegistrar;
 import com.google.firebase.components.ComponentRuntime;
 import com.google.firebase.components.Lazy;
+import com.google.firebase.emulators.EmulatorSettings;
+import com.google.firebase.emulators.FirebaseEmulator;
 import com.google.firebase.events.Publisher;
 import com.google.firebase.heartbeatinfo.DefaultHeartBeatInfo;
 import com.google.firebase.internal.DataCollectionConfigStorage;
@@ -109,6 +111,7 @@ public class FirebaseApp {
   private final String name;
   private final FirebaseOptions options;
   private final ComponentRuntime componentRuntime;
+  private EmulatorSettings emulatorSettings = EmulatorSettings.getDefault();
 
   // Default disabled. We released Firebase publicly without this feature, so making it default
   // enabled is a backwards incompatible change.
@@ -142,6 +145,19 @@ public FirebaseOptions getOptions() {
     return options;
   }
 
+  /**
+   * Returns the specified {@link EmulatorSettings} or a default.
+   *
+   * <p>TODO(samstern): Un-hide this once Firestore, Database, and Functions are implemented
+   *
+   * @hide
+   */
+  @NonNull
+  public EmulatorSettings getEmulatorSettings() {
+    checkNotDeleted();
+    return emulatorSettings;
+  }
+
   @Override
   public boolean equals(Object o) {
     if (!(o instanceof FirebaseApp)) {
@@ -305,6 +321,26 @@ public static FirebaseApp initializeApp(
     return firebaseApp;
   }
 
+  /**
+   * Specify which services should access local emulators for this FirebaseApp instance.
+   *
+   * <p>For example, if the {@link EmulatorSettings} contain {@link
+   * com.google.firebase.emulators.EmulatedServiceSettings} for {@link FirebaseEmulator#FIRESTORE},
+   * then calls to Cloud Firestore will communicate with the emulator rather than production.
+   *
+   * <p>TODO(samstern): Un-hide this once Firestore, Database, and Functions are implemented
+   *
+   * @param emulatorSettings the emulator settings for all services.
+   * @hide
+   */
+  public void enableEmulators(@NonNull EmulatorSettings emulatorSettings) {
+    checkNotDeleted();
+    Preconditions.checkState(
+        !this.emulatorSettings.isAccessed(),
+        "Cannot enable emulators after Firebase SDKs have already been used.");
+    this.emulatorSettings = emulatorSettings;
+  }
+
   /**
    * Deletes the {@link FirebaseApp} and all its data. All calls to this {@link FirebaseApp}
    * instance will throw once it has been called.

firebase-common/src/main/java/com/google/firebase/emulators/EmulatedServiceSettings.java

@@ -0,0 +1,59 @@
+// Copyright 2020 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.
+
+package com.google.firebase.emulators;
+
+import androidx.annotation.NonNull;
+
+/**
+ * Settings to connect a single Firebase service to a local emulator.
+ *
+ * <p>TODO(samstern): Un-hide this once Firestore, Database, and Functions are implemented
+ *
+ * @see EmulatorSettings
+ * @hide
+ */
+public class EmulatedServiceSettings {
+
+  public static final class Builder {
+
+    private final String host;
+    private final int port;
+
+    /**
+     * Create a new EmulatedServiceSettings builder.
+     *
+     * @param host the host where the local emulator is running. If you want to access 'localhost'
+     *     from an Android Emulator use '10.0.2.2' instead.
+     * @param port the port where the local emulator is running.
+     */
+    public Builder(@NonNull String host, int port) {
+      this.host = host;
+      this.port = port;
+    }
+
+    @NonNull
+    public EmulatedServiceSettings build() {
+      return new EmulatedServiceSettings(this.host, this.port);
+    }
+  }
+
+  public final String host;
+  public final int port;
+
+  private EmulatedServiceSettings(@NonNull String host, int port) {
+    this.host = host;
+    this.port = port;
+  }
+}

firebase-common/src/main/java/com/google/firebase/emulators/EmulatorSettings.java

@@ -0,0 +1,104 @@
+// Copyright 2020 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.
+
+package com.google.firebase.emulators;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import com.google.firebase.components.Preconditions;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * Settings that control which Firebase services should access a local emulator, rather than
+ * production.
+ *
+ * <p>TODO(samstern): Un-hide this once Firestore, Database, and Functions are implemented
+ *
+ * @see com.google.firebase.FirebaseApp#enableEmulators(EmulatorSettings)
+ * @hide
+ */
+public class EmulatorSettings {
+
+  /** Empty emulator settings to be used as an internal default */
+  public static EmulatorSettings getDefault() {
+    return new EmulatorSettings.Builder().build();
+  }
+
+  public static final class Builder {
+
+    private final Map<FirebaseEmulator, EmulatedServiceSettings> settingsMap = new HashMap<>();
+
+    /** Constructs an empty builder. */
+    public Builder() {}
+
+    /**
+     * Specify the emulator settings for a single service.
+     *
+     * @param emulator the emulated service.
+     * @param settings the emulator settings.
+     * @return the builder, for chaining.
+     */
+    @NonNull
+    public Builder addEmulatedService(
+        @NonNull FirebaseEmulator emulator, @NonNull EmulatedServiceSettings settings) {
+      Preconditions.checkState(
+          !settingsMap.containsKey(emulator),
+          "Cannot call addEmulatedService twice for " + emulator.toString());
+      this.settingsMap.put(emulator, settings);
+      return this;
+    }
+
+    @NonNull
+    public EmulatorSettings build() {
+      return new EmulatorSettings(new HashMap<>(settingsMap));
+    }
+  }
+
+  private final AtomicBoolean accessed = new AtomicBoolean(false);
+  private final Map<FirebaseEmulator, EmulatedServiceSettings> settingsMap;
+
+  private EmulatorSettings(@NonNull Map<FirebaseEmulator, EmulatedServiceSettings> settingsMap) {
+    this.settingsMap = Collections.unmodifiableMap(settingsMap);
+  }
+
+  /**
+   * Determine if any Firebase SDK has already accessed the emulator settings. When true, attempting
+   * to change the settings should throw an error.
+   *
+   * @hide
+   */
+  public boolean isAccessed() {
+    return accessed.get();
+  }
+
+  /**
+   * Fetch the emulation settings for a single Firebase service. Once this method has been called
+   * {@link #isAccessed()} will return true.
+   *
+   * @hide
+   */
+  @Nullable
+  public EmulatedServiceSettings getServiceSettings(@NonNull FirebaseEmulator emulator) {
+    accessed.set(true);
+
+    if (settingsMap.containsKey(emulator)) {
+      return settingsMap.get(emulator);
+    }
+
+    return null;
+  }
+}

firebase-common/src/main/java/com/google/firebase/emulators/FirebaseEmulator.java

@@ -0,0 +1,46 @@
+// Copyright 2020 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.
+
+package com.google.firebase.emulators;
+
+import androidx.annotation.NonNull;
+
+/**
+ * Identifier Firebase services that can be emulated using the Firebase Emulator Suite.
+ *
+ * <p>TODO(samstern): Un-hide this once Firestore, Database, and Functions are implemented
+ *
+ * @see com.google.firebase.FirebaseApp#enableEmulators(EmulatorSettings)
+ * @see EmulatorSettings
+ * @see EmulatedServiceSettings
+ * @hide
+ */
+public class FirebaseEmulator {
+
+  public final String name;
+
+  /**
+   * Only to be called by SDKs which support emulators in order to make constants.
+   *
+   * @hide
+   */
+  @NonNull
+  public static FirebaseEmulator forName(String name) {
+    return new FirebaseEmulator(name);
+  }
+
+  private FirebaseEmulator(String name) {
+    this.name = name;
+  }
+}

firebase-database/src/androidTest/java/com/google/firebase/database/FirebaseDatabaseTest.java

@@ -30,6 +30,8 @@
 import com.google.firebase.database.core.persistence.MockPersistenceStorageEngine;
 import com.google.firebase.database.core.persistence.PersistenceManager;
 import com.google.firebase.database.future.WriteFuture;
+import com.google.firebase.emulators.EmulatedServiceSettings;
+import com.google.firebase.emulators.EmulatorSettings;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
@@ -64,6 +66,27 @@ public void getInstanceForApp() {
     assertEquals(IntegrationTestValues.getAltNamespace(), db.getReference().toString());
   }
 
+  @Test
+  public void getInstanceForAppWithEmulator() {
+    FirebaseApp app =
+        appForDatabaseUrl(IntegrationTestValues.getAltNamespace(), "getInstanceForAppWithEmulator");
+
+    EmulatedServiceSettings serviceSettings =
+        new EmulatedServiceSettings.Builder("10.0.2.2", 9000).build();
+    EmulatorSettings emulatorSettings =
+        new EmulatorSettings.Builder()
+            .addEmulatedService(FirebaseDatabase.EMULATOR, serviceSettings)
+            .build();
+    app.enableEmulators(emulatorSettings);
+
+    FirebaseDatabase db = FirebaseDatabase.getInstance(app);
+    DatabaseReference rootRef = db.getReference();
+    assertEquals(rootRef.toString(), "http://10.0.2.2:9000");
+
+    DatabaseReference urlReference = db.getReferenceFromUrl("https://otherns.firebaseio.com");
+    assertEquals(urlReference.toString(), "http://10.0.2.2:9000");
+  }
+
   @Test
   public void getInstanceForAppWithUrl() {
     FirebaseApp app =