/**
 * 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.
 *
 * See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.
 */
package org.sintef.thingml.resource.thingml.ui;

/**
 * A background parsing strategy that starts parsing after a amount of time after
 * the last key stroke. If keys are pressed within the delay interval, the delay
 * is reset. If keys are pressed during background parsing the parse thread is
 * stopped and a new parse task is scheduled.
 */
public class ThingmlBackgroundParsingStrategy {
	
	private static long DELAY = 500;
	
	/**
	 * this timer is used to schedule a parsing task and execute it after a given delay
	 */
	private Object lock = new Object();
	
	/**
	 * the background parsing task (may be null)
	 */
	private ParsingJob job = null;
	
	/**
	 * Schedules a task for background parsing that will be started after a delay.
	 */
	public void parse(org.eclipse.jface.text.DocumentEvent event, final org.sintef.thingml.resource.thingml.IThingmlTextResource resource, final org.sintef.thingml.resource.thingml.ui.ThingmlEditor editor) {
		parse(event.getDocument(), resource, editor, DELAY);
	}
	
	/**
	 * Schedules a task for background parsing that will be started after a delay.
	 */
	public void parse(org.eclipse.jface.text.IDocument document, final org.sintef.thingml.resource.thingml.IThingmlTextResource resource, final org.sintef.thingml.resource.thingml.ui.ThingmlEditor editor, long delay) {
		parse(document.get(), resource, editor, delay);
	}
	
	/**
	 * Schedules a task for background parsing that will be started after a delay.
	 */
	public void parse(final String contents, final org.sintef.thingml.resource.thingml.IThingmlTextResource resource, final org.sintef.thingml.resource.thingml.ui.ThingmlEditor editor, long delay) {
		if (resource == null) {
			return;
		}
		if (contents == null) {
			return;
		}
		
		// this synchronization is needed to avoid the creation of multiple tasks. without
		// the synchronization this could easily happen, when this method is accessed by
		// multiple threads. the creation of multiple tasks would imply that multiple
		// background parsing threads for one editor are created, which is not desired.
		synchronized (lock) {
			if (job == null || job.getState() != org.eclipse.core.runtime.jobs.Job.RUNNING) {
				// schedule new task
				job = new ParsingJob();
				job.resource = resource;
				job.editor = editor;
				job.newContents = contents;
				job.schedule();
			} else {
				job.newContents = contents;
			}
		}
	}
	
	private class ParsingJob extends org.eclipse.core.runtime.jobs.Job {
		private org.sintef.thingml.resource.thingml.ui.ThingmlEditor editor;
		private org.sintef.thingml.resource.thingml.IThingmlTextResource resource;
		
		public ParsingJob() {
			super("parsing document");
		}
		
		private String newContents = null;
		
		protected org.eclipse.core.runtime.IStatus run(org.eclipse.core.runtime.IProgressMonitor monitor) {
			while (newContents != null ) {
				while (newContents != null) {
					try {
						String currentContent = newContents;
						newContents = null;
						String encoding = null;
						if (resource instanceof org.sintef.thingml.resource.thingml.mopp.ThingmlResource) {
							org.sintef.thingml.resource.thingml.mopp.ThingmlResource concreteResource = (org.sintef.thingml.resource.thingml.mopp.ThingmlResource) resource;
							encoding = concreteResource.getEncoding(null);
						}
						byte[] bytes = null;
						if (encoding != null) {
							bytes = currentContent.getBytes(encoding);
						} else {
							bytes = currentContent.getBytes();
						}
						resource.reload(new java.io.ByteArrayInputStream(bytes), null);
						if (newContents != null) {
							Thread.sleep(DELAY);
						}
					} catch (java.lang.Exception e) {
						e.printStackTrace();
					}
				}
				editor.notifyBackgroundParsingFinished();
			}
			return org.eclipse.core.runtime.Status.OK_STATUS;
		}
	};
	
}