Merge "Add a class for grouping together related callbacks"

gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/PublishCommentScreen.java

@@ -18,6 +18,7 @@ import com.google.gerrit.client.Gerrit;
 import com.google.gerrit.client.patches.AbstractPatchContentTable;
 import com.google.gerrit.client.patches.CommentEditorContainer;
 import com.google.gerrit.client.patches.CommentEditorPanel;
+import com.google.gerrit.client.rpc.CallbackGroup;
 import com.google.gerrit.client.rpc.GerritCallback;
 import com.google.gerrit.client.rpc.RestApi;
 import com.google.gerrit.client.rpc.ScreenLoadCallback;
@@ -145,7 +146,9 @@ public class PublishCommentScreen extends AccountScreen implements
   @Override
   protected void onLoad() {
     super.onLoad();
-    Util.DETAIL_SVC.patchSetPublishDetail(patchSetId,
+
+    CallbackGroup cbs = new CallbackGroup();
+    Util.DETAIL_SVC.patchSetPublishDetail(patchSetId, cbs.addGwtjsonrpc(
         new ScreenLoadCallback<PatchSetPublishDetail>(this) {
           @Override
           protected void preDisplay(final PatchSetPublishDetail result) {
@@ -157,7 +160,7 @@ public class PublishCommentScreen extends AccountScreen implements
           protected void postDisplay() {
             message.setFocus(true);
           }
-        });
+        }));
   }
 
   @Override

gerrit-gwtui/src/main/java/com/google/gerrit/client/rpc/CallbackGroup.java

@@ -0,0 +1,121 @@
+// Copyright (C) 2013 The Android Open Source Project
+//
+// 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.gerrit.client.rpc;
+
+import com.google.gwt.user.client.rpc.AsyncCallback;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Class for grouping together callbacks and calling them in order.
+ * <p>
+ * Callbacks are added to the group with {@link #add(AsyncCallback)}, which
+ * returns a wrapped callback suitable for passing to an asynchronous RPC call.
+ * The enclosing group buffers returned results and ensures that
+ * {@code onSuccess} is called exactly once for each callback in the group, in
+ * the same order that callbacks were added. This allows callers to, for
+ * example, use a {@link ScreenLoadCallback} as the last callback in the list
+ * and only display the screen once all callbacks have succeeded.
+ * <p>
+ * In the event of a failure, the <em>first</em> caught exception is sent to
+ * <em>all</em> callbacks' {@code onFailure} methods, in order; subsequent
+ * successes or failures are all ignored. Note that this means
+ * {@code onFailure} may be called with an exception unrelated to the callback
+ * processing it.
+ */
+public class CallbackGroup {
+  private final List<Object> callbacks;
+  private final Map<Object, Object> results;
+  private boolean failed;
+
+  public CallbackGroup() {
+    callbacks = new ArrayList<Object>();
+    results = new HashMap<Object, Object>();
+  }
+
+  public <T> AsyncCallback<T> add(final AsyncCallback<T> cb) {
+    callbacks.add(cb);
+    return new AsyncCallback<T>() {
+      @Override
+      public void onSuccess(T result) {
+        results.put(cb, result);
+        CallbackGroup.this.onSuccess();
+      }
+
+      @Override
+      public void onFailure(Throwable caught) {
+        CallbackGroup.this.onFailure(caught);
+      }
+    };
+  }
+
+  public <T> com.google.gwtjsonrpc.common.AsyncCallback<T> addGwtjsonrpc(
+      final com.google.gwtjsonrpc.common.AsyncCallback<T> cb) {
+    callbacks.add(cb);
+    return new com.google.gwtjsonrpc.common.AsyncCallback<T>() {
+      @Override
+      public void onSuccess(T result) {
+        results.put(cb, result);
+        CallbackGroup.this.onSuccess();
+      }
+
+      @Override
+      public void onFailure(Throwable caught) {
+        CallbackGroup.this.onFailure(caught);
+      }
+    };
+  }
+
+  private void onSuccess() {
+    if (results.size() < callbacks.size()) {
+      return;
+    }
+    for (Object o : callbacks) {
+      Object result = results.get(o);
+      if (o instanceof AsyncCallback) {
+        @SuppressWarnings("unchecked")
+        AsyncCallback<Object> cb = (AsyncCallback<Object>) o;
+        cb.onSuccess(result);
+      } else {
+        @SuppressWarnings("unchecked")
+        com.google.gwtjsonrpc.common.AsyncCallback<Object> cb =
+            (com.google.gwtjsonrpc.common.AsyncCallback<Object>) o;
+        cb.onSuccess(result);
+      }
+    }
+  }
+
+  private void onFailure(Throwable caught) {
+    if (failed) {
+      return;
+    }
+    failed = true;
+    for (Object o : callbacks) {
+      if (o instanceof AsyncCallback) {
+        @SuppressWarnings("unchecked")
+        AsyncCallback<Object> cb = (AsyncCallback<Object>) o;
+        cb.onFailure(caught);
+      } else {
+        @SuppressWarnings("unchecked")
+        com.google.gwtjsonrpc.common.AsyncCallback<Object> cb =
+            (com.google.gwtjsonrpc.common.AsyncCallback<Object>) o;
+        cb.onFailure(caught);
+      }
+    }
+  }
+}