/*******************************************************************************
 * Copyright (c) 2011-2016 Igor Fedorenko
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *      Igor Fedorenko - initial API and implementation
 *******************************************************************************/
package org.eclipse.jdt.internal.launching.sourcelookup.advanced;

import java.util.ArrayList;
import java.util.List;

import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.MultiStatus;
import org.eclipse.core.runtime.Status;
import org.eclipse.core.runtime.SubMonitor;
import org.eclipse.core.runtime.jobs.Job;
import org.eclipse.jdt.internal.launching.LaunchingPlugin;

/**
 * Simple background request processing queue implemented using {@link Job} API. Requests are executed in the order they arrive. Request execution
 * delayed by {@value #EXECUTION_DELAY} milliseconds and all requests submitted during this period will be processed together.
 */
public class BackgroundProcessingJob extends Job {
	private static final long EXECUTION_DELAY = 1000L;

	private final ArrayList<IRunnableWithProgress> queue = new ArrayList<>();

	public BackgroundProcessingJob() {
		super(Messages.BackgroundProcessingJob_name);
	}

	@Override
	protected IStatus run(IProgressMonitor monitor) {
		ArrayList<IRunnableWithProgress> tasks;
		synchronized (this.queue) {
			tasks = new ArrayList<>(this.queue);
			this.queue.clear();
		}

		SubMonitor progress = SubMonitor.convert(monitor, tasks.size());

		List<IStatus> errors = new ArrayList<>();

		for (IRunnableWithProgress task : tasks) {
			try {
				task.run(progress.split(1));
			}
			catch (CoreException e) {
				errors.add(e.getStatus());
			}
		}

		if (errors.isEmpty()) {
			return Status.OK_STATUS;
		}

		if (errors.size() == 1) {
			return errors.get(0);
		}

		return new MultiStatus(LaunchingPlugin.ID_PLUGIN, IStatus.ERROR, errors.toArray(new IStatus[errors.size()]), Messages.BackgroundProcessingJob_failed, null);
	}

	public void schedule(IRunnableWithProgress task) {
		synchronized (queue) {
			queue.add(task);
			schedule(EXECUTION_DELAY);
		}
	}
}