/**
* Copyright 2009 Google Inc.
*
* 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 org.waveprotocol.wave.client.scheduler;
import com.google.gwt.user.client.ui.Widget;
import org.waveprotocol.wave.client.scheduler.Scheduler.Priority;
import org.waveprotocol.wave.client.scheduler.Scheduler.Schedulable;
/**
* Something that can control the behaviour of the scheduler, and display
* controls in the UI.
*
* The only control mechanism is the ability to enable or disable priority
* levels, exposed by {@link #isRunnable(Priority)}.
*
* A controller is also notified when jobs are added and removed
*
*/
public interface Controller {
/**
* Tells this controller a job was added.
*
* @param priority priority level
* @param job the job
*/
void jobAdded(Priority priority, Schedulable job);
/**
* Tells this controller a job was removed.
*
* @param priority priority level
* @param job the job
*/
void jobRemoved(Priority priority, Schedulable job);
/**
* Queries whether a priority level should be run or not.
*
* @param priority priority level
* @return true if tasks in {@code priority} should be run; false if they
* should not be run.
*/
boolean isRunnable(Priority priority);
/**
* Queries whether an individual job is to be suppressed when run at a specific priority.
* This is independent of {@link #isRunnable(Priority)}
*
* @param priority
* @param job
* @return true if the job is to be suppressed
*/
boolean isSuppressed(Priority priority, Schedulable job);
/**
* Gets the view of this controller, if it has one.
*
* @return the controller's view, or {@code null} if there is no view.
*/
Widget asWidget();
/**
* Controller implementation that does nothing. GWT optimizations should make
* the cost of this implementation zero.
*/
public static final Controller NOOP = new Controller() {
@Override
public Widget asWidget() {
return null;
}
@Override
public void jobAdded(Priority priority, Schedulable job) {
// Do nothing
}
@Override
public void jobRemoved(Priority priority, Schedulable job) {
// Do nothing
}
@Override
public boolean isRunnable(Priority priority) {
return true;
}
@Override
public boolean isSuppressed(Priority priority, Schedulable job) {
return false;
}
};
}