Interval.java

package marubinotto.util.time;

import marubinotto.util.Assert;

/**
 * A definite length of time marked off by two instants.
 */
public class Interval extends Duration {

	private DateTime start;
	private DateTime end;

	public Interval() {
		super();
		this.start = DateTime.getCurrentTime();
		this.end = this.start;
	}

	public Interval(DateTime start, DateTime end) {
		super(end.getTime() - start.getTime());
		this.start = start;
		this.end = end;
	}

	public DateTime getStartInstant() {
		return this.start;
	}

	public DateTime getEndInstant() {
		return this.end;
	}

	protected void setStartInstant(DateTime start) {
		this.start = start;
		updateDuration();
	}

	protected void setEndInstant(DateTime end) {
		this.end = end;
		updateDuration();
	}

	private void updateDuration() {
		if (this.start != null && this.end != null) {
			long milliseconds = this.end.getTime() - this.start.getTime();
			setMilliseconds(Math.abs(milliseconds));
		}
	}

	public boolean containsInstant(DateTime instant) {
		Assert.Arg.notNull(instant, "instant");
		return instant.getTime() >= this.start.getTime()
			&& instant.getTime() <= this.end.getTime();
	}

	public boolean overlapsInterval(Interval interval) {
		Assert.Arg.notNull(interval, "interval");
		return interval.containsInstant(getStartInstant())
			|| interval.containsInstant(getEndInstant())
			|| containsInstant(interval.getStartInstant());
	}

	public Interval getOverlap(Interval interval) {
		if (!overlapsInterval(interval)) {
			return null;
		}

		DateTime start = null;
		if (getStartInstant().after(interval.getStartInstant())) {
			start = getStartInstant();
		}
		else {
			start = interval.getStartInstant();
		}

		DateTime end = null;
		if (getEndInstant().before(interval.getEndInstant())) {
			end = getEndInstant();
		}
		else {
			end = interval.getEndInstant();
		}

		return new Interval(start, end);
	}
}