/**
* 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.scheduler;
import com.google.gwt.core.client.Scheduler.ScheduledCommand;
import org.waveprotocol.wave.model.util.CollectionUtils;
import org.waveprotocol.wave.model.util.IdentitySet;
/**
* Convenience scheduleFinally wrapper.
*
* Behaves according to the following semantics:
* <li> Tasks scheduled will be run at once.
* <li> Tasks scheduled during task execution will be grouped into the current
* run.
* <li> Tasks scheduled more than once, that have not yet executed, will only
* be executed once.
* <li> The order in which tasks will actually execute is not defined.
*
* Custome behaviour may be defined at the start and end of a group run by
* overriding {@code being} and {@code end}
*
* @author danilatos@google.com (Daniel Danilatos)
*/
public class FinalTaskRunnerImpl implements FinalTaskRunner {
private final IdentitySet<Scheduler.Task> tasks = CollectionUtils.createIdentitySet();
private boolean isExecuting = false;
private final ScheduledCommand command = new ScheduledCommand() {
@Override
public void execute() {
begin();
isExecuting = true;
try {
while (!tasks.isEmpty()) {
Scheduler.Task task = tasks.someElement();
tasks.remove(task);
task.execute();
}
} finally {
isExecuting = false;
end();
}
}
};
/**
* Override to provide functionality at the start of a task group
*/
protected void begin() {
}
/**
* Override to provide functionality at the end of a task group
*/
protected void end() {
}
@Override
public void scheduleFinally(Scheduler.Task task) {
if (tasks.isEmpty() && !isExecuting) {
com.google.gwt.core.client.Scheduler.get().scheduleFinally(command);
}
tasks.add(task);
}
}