Add SubscriptionId class and tests. Use SubscriptionId in listSubscri…

…ptions(topic)

gcloud-java-pubsub/src/main/java/com/google/cloud/pubsub/PubSub.java

@@ -194,9 +194,9 @@ public static PullOption maxConcurrentCallbacks(int maxConcurrency) {
 
   Future<AsyncPage<Subscription>> listSubscriptionsAsync(ListOption... options);
 
-  Page<Subscription> listSubscriptions(String topic, ListOption... options);
+  Page<SubscriptionId> listSubscriptions(String topic, ListOption... options);
 
-  Future<AsyncPage<Subscription>> listSubscriptionsAsync(String topic, ListOption... options);
+  Future<AsyncPage<SubscriptionId>> listSubscriptionsAsync(String topic, ListOption... options);
 
   Iterator<ReceivedMessage> pull(String subscription, PullOption... options);
 

gcloud-java-pubsub/src/main/java/com/google/cloud/pubsub/PubSubImpl.java

@@ -185,12 +185,12 @@ public Future<AsyncPage<Subscription>> listSubscriptionsAsync(ListOption... opti
   }
 
   @Override
-  public Page<Subscription> listSubscriptions(String topic, ListOption... options) {
+  public Page<SubscriptionId> listSubscriptions(String topic, ListOption... options) {
     return null;
   }
 
   @Override
-  public Future<AsyncPage<Subscription>> listSubscriptionsAsync(String topic,
+  public Future<AsyncPage<SubscriptionId>> listSubscriptionsAsync(String topic,
       ListOption... options) {
     return null;
   }

gcloud-java-pubsub/src/main/java/com/google/cloud/pubsub/SubscriptionId.java

@@ -0,0 +1,89 @@
+/*
+ * Copyright 2016 Google Inc. All Rights Reserved.
+ *
+ * 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.cloud.pubsub;
+
+import static com.google.cloud.pubsub.spi.v1.SubscriberApi.parseProjectFromSubscriptionName;
+import static com.google.cloud.pubsub.spi.v1.SubscriberApi.parseSubscriptionFromSubscriptionName;
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import com.google.common.base.MoreObjects;
+
+import java.io.Serializable;
+import java.util.Objects;
+
+/**
+ * Identity for a Google PubSub subscription. {@code SubscriptionId} objects are returned by the
+ * {@link PubSub#listSubscriptions(String, PubSub.ListOption...)} and
+ * {@link PubSub#listSubscriptionsAsync(String, PubSub.ListOption...)} methods as the same topic
+ * can be used by subscriptions in different projects.
+ */
+public class SubscriptionId implements Serializable {
+
+  private static final long serialVersionUID = 6507142968866856283L;
+
+  private final String project;
+  private final String subscription;
+
+  SubscriptionId(String project, String subscription) {
+    this.project = checkNotNull(project);
+    this.subscription = checkNotNull(subscription);
+  }
+
+  /**
+   * Returns the name of the project where the subscription resides.
+   */
+  public String project() {
+    return project;
+  }
+
+  /**
+   * Returns the name of the subscription.
+   */
+  public String subscription() {
+    return subscription;
+  }
+
+  @Override
+  public String toString() {
+    return MoreObjects.toStringHelper(this)
+        .add("project", project)
+        .add("subscription", subscription).toString();
+  }
+
+  @Override
+  public final int hashCode() {
+    return Objects.hash(project, subscription);
+  }
+
+  @Override
+  public final boolean equals(Object obj) {
+    if (obj == this) {
+      return true;
+    }
+    if (!(obj instanceof SubscriptionId)) {
+      return false;
+    }
+    SubscriptionId other = (SubscriptionId) obj;
+    return Objects.equals(project, other.project)
+        && Objects.equals(subscription, other.subscription);
+  }
+
+  static SubscriptionId fromPb(String pb) {
+    return new SubscriptionId(parseProjectFromSubscriptionName(pb),
+        parseSubscriptionFromSubscriptionName(pb));
+  }
+}

gcloud-java-pubsub/src/main/java/com/google/cloud/pubsub/Topic.java

@@ -133,11 +133,11 @@ public Future<List<String>> publishAsync(Iterable<Message> messages) {
     return pubsub.publishAsync(name(), messages);
   }
 
-  public Page<Subscription> listSubscriptions(ListOption... options) {
+  public Page<SubscriptionId> listSubscriptions(ListOption... options) {
     return pubsub.listSubscriptions(name(), options);
   }
 
-  public Future<AsyncPage<Subscription>> listSubscriptionsAsync(ListOption... options) {
+  public Future<AsyncPage<SubscriptionId>> listSubscriptionsAsync(ListOption... options) {
     return pubsub.listSubscriptionsAsync(name(), options);
   }
 

gcloud-java-pubsub/src/test/java/com/google/cloud/pubsub/SubscriptionIdTest.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2016 Google Inc. All Rights Reserved.
+ *
+ * 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.cloud.pubsub;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class SubscriptionIdTest {
+
+  private static final String PROJECT = "project";
+  private static final String NAME = "subscription";
+  private static final String TOPIC_PB = "projects/project/subscriptions/subscription";
+  private static final SubscriptionId SUBSCRIPTION_ID = new SubscriptionId(PROJECT, NAME);
+
+  @Test
+  public void testConstructor() {
+    assertEquals(PROJECT, SUBSCRIPTION_ID.project());
+    assertEquals(NAME, SUBSCRIPTION_ID.subscription());
+  }
+
+  @Test
+  public void testToAndFromPb() {
+    SubscriptionId subscriptionId = SubscriptionId.fromPb(TOPIC_PB);
+    compareSubscriptionId(SUBSCRIPTION_ID, subscriptionId);
+    assertEquals(PROJECT, subscriptionId.project());
+    assertEquals(NAME, subscriptionId.subscription());
+  }
+
+  private void compareSubscriptionId(SubscriptionId expected, SubscriptionId value) {
+    assertEquals(expected, value);
+    assertEquals(expected.project(), expected.project());
+    assertEquals(expected.subscription(), expected.subscription());
+    assertEquals(expected.hashCode(), expected.hashCode());
+  }
+}