/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.waveprotocol.wave.client.doodad.experimental.htmltemplate;
import com.google.gwt.core.client.JavaScriptObject;
import com.google.gwt.dom.client.Document;
import com.google.gwt.dom.client.ScriptElement;
/**
* Performs requests via JSONP, and works with services that disallow '.' in
* the JSONP callback name (GWT's JsonpRequestBuilder requires that the
* callback name allow '.' characters).
*
* Each request is handled by a unique window function.
*
* @param <R> response type
*/
final class JsonpRouter<R extends JavaScriptObject> {
private final static String JSONP_HANDLER_PREFIX = "__jsonp";
private final static String JSONP_CALLBACK_PARAM = "callback";
private static int jsonpCounter;
static <R extends JavaScriptObject> JsonpRouter<R> create() {
return new JsonpRouter<R>();
}
/**
* Registers a function on the root window object.
*
* @param id function name
* @param callback 1-arg function
*/
private static native void registerCallback(String id, Callback<JavaScriptObject> callback) /*-{
$wnd[id] = $entry(function(obj) {
callback.@org.waveprotocol.wave.client.doodad.experimental.htmltemplate.Callback::onSuccess(Ljava/lang/Object;)
(obj);
});
}-*/;
/**
* Deletes a function previously registered with
* {@link #registerCallback(String, Callback)}.
*
* @param id function name
*/
private static native void deregisterCallback(String id) /*-{
delete $wnd["id"];
}-*/;
/**
* Fires a request to a JSONP-supporting URL.
*/
public void request(String url, final Callback<? super R> request) {
final String id = JSONP_HANDLER_PREFIX + jsonpCounter++;
final ScriptElement requestMaker = Document.get().createScriptElement();
registerCallback(id, new Callback<JavaScriptObject>() {
@Override
public void onSuccess(JavaScriptObject cajoled) {
requestMaker.removeFromParent();
deregisterCallback(id);
request.onSuccess(cajoled.<R>cast());
}
@Override
public void onError(String message) {
// Ignore
}
});
requestMaker.setSrc(url + "&" + JSONP_CALLBACK_PARAM + "=" + id);
Document.get().getBody().appendChild(requestMaker);
}
}