package eu.simstadt.nf4j.async;

import java.util.EventObject;
import java.util.Optional;

import eu.simstadt.nf4j.Job;
import eu.simstadt.nf4j.JobStatus;

/**
 * Every time when the status of a job progresses, one of this events will be created and sent
 * to all of the job status listeners registered at the job. Job status listeners implement
 * the jobStatusChanged() method which takes this JobStatusEvent as its argument. This event will
 * contain the job status as the event source and listener can read the source and decide how to
 * deal with the new status of its observed job.
 * 
 * Note, the job status, job and additional event messages will be referenced in extra object members of this event,
 * because the status of referenced job may change during the notification of the listeners. Therefore, obtaining
 * the job status directly from the job is not reliable, if the listener wants to know the actual source of this
 * event.   
 * 
 * @author Marcel Bruse
 */
public class JobStatusEvent extends EventObject {

	private static final long serialVersionUID = -1800246486543538087L;
	
	/** The job for which this event will be sent to the job status listeners. */
	private Job job;
	
	/** There might be an additional (error) message provided with the new job status. */
	private Optional<String> message;

	/**
	 * Constructor with job status as event source. The source can be read by the job status listeners.
	 * 
	 * @param source The new job status, which triggers this event.
	 */
	public JobStatusEvent(JobStatus source, Job job) {
		this(source, job, null);
	}
	
	/**
	 * Constructor with job status as event source and an additional (error) message. The source can be read
	 * by the job status listeners.
	 * 
	 * @param source The new job status, which triggers this event.
	 * @param message an additional (error) message for this event and job status.
	 */
	public JobStatusEvent(JobStatus source, Job job, Optional<String> message) {
		super(source);
		this.job = job;
		this.message = message;
	}
	
	/**
	 * @return Returns the job for which this event will be sent to the job status listeners.
	 */
	public Job getJob() {
		return job;
	}
	
	/**
	 * @return Returns an additional (error) message, if present.
	 */
	public Optional<String> getMessage() {
		return message;
	}

}