package envoy.data;

import java.io.Serializable;

/**
 * Generates increasing IDs between two numbers.
 *
 * @author Kai S. K. Engelbart
 * @since Envoy Common v0.2-alpha
 */
public final class IDGenerator implements Serializable {

	private final long	end;
	private long		current;

	private static final long serialVersionUID = 0L;

	/**
	 * Creates an instance of {@link IDGenerator}.
	 *
	 * @param begin the first ID
	 * @param size  the amount of IDs to provide
	 * @since Envoy Common v0.2-alpha
	 */
	public IDGenerator(long begin, long size) {
		current	= begin;
		end		= begin + size;
	}

	@Override
	public String toString() {
		return String.format("IDGenerator[current=%d,end=%d]", current, end);
	}

	/**
	 * @return {@code true} if there are unused IDs remaining
	 * @since Envoy Common v0.2-alpha
	 */
	public boolean hasNext() {
		return current < end;
	}

	/**
	 * @return the next ID
	 * @since Envoy Common v0.2-alpha
	 */
	public long next() {
		if (!hasNext())
			throw new IllegalStateException("All IDs have been used");
		return current++;
	}
}