Allow UiActions to perform redirects without JavaScript

This is a simple approach to enable a GET based UiAction to send a
redirect to the browser to either replace Gerrit or open a new window
without writing JavaScript.

Change-Id: I38ca4bbad1ccf4a9ff376d17243b9d445abed537

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/webui/UiResult.java

@@ -0,0 +1,59 @@
+// Copyright (C) 2014 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.extensions.webui;
+
+import java.net.URI;
+
+/** Default result for {@link UiAction}s with no JavaScript. */
+public class UiResult {
+  /** Display an alert message to the user. */
+  public static UiResult alert(String message) {
+    UiResult r = new UiResult();
+    r.alert = message;
+    return r;
+  }
+
+  /** Launch URL in a new window. */
+  public static UiResult openUrl(URI uri) {
+    return openUrl(uri.toString());
+  }
+
+  /** Launch URL in a new window. */
+  public static UiResult openUrl(String url) {
+    UiResult r = new UiResult();
+    r.url = url;
+    r.openWindow = true;
+    return r;
+  }
+
+  /** Redirect the browser to a new URL. */
+  public static UiResult redirectUrl(String url) {
+    UiResult r = new UiResult();
+    r.url = url;
+    return r;
+  }
+
+  /** Alert the user with a message. */
+  protected String alert;
+
+  /** If present redirect browser to this URL. */
+  protected String url;
+
+  /** When true open {@link #url} in a new tab/window. */
+  protected Boolean openWindow;
+
+  private UiResult() {
+  }
+}

gerrit-gwtui/src/main/java/com/google/gerrit/client/api/DefaultActions.java

@@ -24,6 +24,7 @@ import com.google.gerrit.common.PageLinks;
 import com.google.gerrit.reviewdb.client.Project;
 import com.google.gwt.core.client.JavaScriptObject;
 import com.google.gwt.user.client.Window;
+import com.google.gwt.user.client.Window.Location;
 import com.google.gwt.user.client.rpc.AsyncCallback;
 
 class DefaultActions {
@@ -38,14 +39,27 @@ class DefaultActions {
   private static AsyncCallback<JavaScriptObject> callback(final String target) {
     return new GerritCallback<JavaScriptObject>() {
       @Override
-      public void onSuccess(JavaScriptObject msg) {
-        if (NativeString.is(msg)) {
-          NativeString str = (NativeString) msg;
-          if (!str.asString().isEmpty()) {
-            Window.alert(str.asString());
-          }
+      public void onSuccess(JavaScriptObject in) {
+        UiResult result = asUiResult(in);
+        if (result.alert() != null) {
+          Window.alert(result.alert());
         }
-        Gerrit.display(target);
+
+        if (result.redirectUrl() != null && result.openWindow()) {
+          Window.open(result.redirectUrl(), "_blank", null);
+        } else if (result.redirectUrl() != null) {
+          Location.assign(result.redirectUrl());
+        } else {
+          Gerrit.display(target);
+        }
+      }
+
+      private UiResult asUiResult(JavaScriptObject in) {
+        if (NativeString.is(in)) {
+          String str = ((NativeString) in).asString();
+          return str.isEmpty() ? UiResult.none() : UiResult.alert(str);
+        }
+        return in.cast();
       }
     };
   }
@@ -65,4 +79,16 @@ class DefaultActions {
 
   private DefaultActions() {
   }
+
+  private static class UiResult extends JavaScriptObject {
+    static native UiResult alert(String m) /*-{ return {'alert':m} }-*/;
+    static native UiResult none() /*-{ return {} }-*/;
+
+    final native String alert() /*-{ return this.alert }-*/;
+    final native String redirectUrl() /*-{ return this.url }-*/;
+    final native boolean openWindow() /*-{ return this.open_window || false }-*/;
+
+    protected UiResult() {
+    }
+  }
 }