Firestore: Adding Collection Group queries

google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/CollectionReference.java

@@ -59,7 +59,7 @@ public class CollectionReference extends Query {
    */
   @Nonnull
   public String getId() {
-    return path.getId();
+    return options.getCollectionId();
   }
 
   /**
@@ -69,7 +69,7 @@ public String getId() {
    */
   @Nullable
   public DocumentReference getParent() {
-    ResourcePath parent = path.getParent();
+    ResourcePath parent = options.getParentPath();
     return parent.isDocument() ? new DocumentReference(firestore, parent) : null;
   }
 
@@ -81,7 +81,7 @@ public DocumentReference getParent() {
    */
   @Nonnull
   public String getPath() {
-    return path.getPath();
+    return getResourcePath().getPath();
   }
 
   /**
@@ -104,10 +104,10 @@ public DocumentReference document() {
    */
   @Nonnull
   public DocumentReference document(@Nonnull String childPath) {
-    ResourcePath documentPath = path.append(childPath);
+    ResourcePath documentPath = getResourcePath().append(childPath);
     Preconditions.checkArgument(
         documentPath.isDocument(),
-        String.format("Path should point to a Document Reference: %s", path));
+        String.format("Path should point to a Document Reference: %s", getPath()));
     return new DocumentReference(firestore, documentPath);
   }
 
@@ -124,8 +124,8 @@ public DocumentReference document(@Nonnull String childPath) {
   @Nonnull
   public Iterable<DocumentReference> listDocuments() {
     ListDocumentsRequest.Builder request = ListDocumentsRequest.newBuilder();
-    request.setParent(path.getParent().toString());
-    request.setCollectionId(this.getId());
+    request.setParent(options.getParentPath().toString());
+    request.setCollectionId(options.getCollectionId());
     request.setMask(DocumentMask.getDefaultInstance());
     request.setShowMissing(true);
 
@@ -206,4 +206,9 @@ public ApiFuture<DocumentReference> add(Object pojo) {
     }
     return add((Map<String, Object>) converted);
   }
+
+  /** Returns a resource path pointing to this collection. */
+  ResourcePath getResourcePath() {
+    return options.getParentPath().append(options.getCollectionId());
+  }
 }

google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/Firestore.java

@@ -62,6 +62,16 @@ public interface Firestore extends Service<FirestoreOptions>, AutoCloseable {
   @Nonnull
   Iterable<CollectionReference> getCollections();
 
+  /**
+   * Creates and returns a new @link{Query} that includes all documents in the database that are
+   * contained in a collection or subcollection with the given @code{collectionId}.
+   *
+   * @param collectionId Identifies the collections to query over. Every collection or subcollection
+   *     with this ID as the last segment of its path will be included. Cannot contain a slash.
+   * @return The created Query.
+   */
+  Query collectionGroup(@Nonnull String collectionId);
+
   /**
    * Executes the given updateFunction and then attempts to commit the changes applied within the
    * transaction. If any document read within the transaction has changed, the updateFunction will

google-cloud-clients/google-cloud-firestore/src/main/java/com/google/cloud/firestore/FirestoreImpl.java

@@ -106,7 +106,10 @@ public WriteBatch batch() {
   @Nonnull
   @Override
   public CollectionReference collection(@Nonnull String collectionPath) {
-    return new CollectionReference(this, databasePath.append(collectionPath));
+    ResourcePath path = databasePath.append(collectionPath);
+    Preconditions.checkArgument(
+        path.isCollection(), "Invalid path specified. Path should point to a collection");
+    return new CollectionReference(this, path);
   }
 
   @Nonnull
@@ -244,6 +247,16 @@ public void onCompleted() {
     return futureList;
   }
 
+  @Nonnull
+  @Override
+  public Query collectionGroup(@Nonnull final String collectionId) {
+    Preconditions.checkArgument(
+        !collectionId.contains("/"),
+        String.format(
+            "Invalid collectionId '%s'. Collection IDs must not contain '/'.", collectionId));
+    return new Query(this, collectionId);
+  }
+
   @Nonnull
   @Override
   public <T> ApiFuture<T> runTransaction(@Nonnull final Transaction.Function<T> updateFunction) {
@@ -401,6 +414,11 @@ String getDatabaseName() {
     return databasePath.getDatabaseName().toString();
   }
 
+  /** Returns a path to the Firestore project associated with this client. */
+  ResourcePath getResourcePath() {
+    return databasePath;
+  }
+
   /** Returns the underlying RPC client. */
   FirestoreRpc getClient() {
     return firestoreClient;