envoy/src/main/java/envoy/event/GroupResizeEvent.java

package envoy.event;

import envoy.data.Contact;
import envoy.data.Group;
import envoy.data.User;

/**
 * This event is used to communicate changes in the group size between client
 * and server.<br>
 * Possible actions are adding or removing certain {@link User}s to or from a
 * certain {@link Group}
 * <br>
 * Project: <strong>envoy-common</strong><br>
 * File: <strong>GroupResizeEvent.java</strong><br>
 * Created: <strong>25 Mar 2020</strong><br>
 *
 * @author Leon Hofmeister
 * @since Envoy Common v0.1-beta
 */
public class GroupResizeEvent extends Event<Long> {

	private final long		groupID;
	private final Operation	operation;

	private static final long serialVersionUID = 0L;

	/**
	 * This enum defines all possibilities for handling
	 * {@link GroupResizeEvent}s.<br>
	 * These can be: {@link Operation#ADD} or {@link Operation#REMOVE}.<br>
	 * <br>
	 * Project: <strong>envoy-common</strong><br>
	 * File: <strong>GroupResizeEvent.java</strong><br>
	 * Created: <strong>25 Mar 2020</strong><br>
	 *
	 * @author Leon Hofmeister
	 * @since Envoy Common v0.1-beta
	 */
	public enum Operation {
		/**
		 * Select this element, if the given {@link User} should be added to the given
		 * {@link Group}
		 */
		ADD,
		/**
		 * Select this element, if the given {@link User} should be removed from the
		 * given {@link Group}
		 */
		REMOVE
	}

	/**
	 * Initializes a {@link GroupResizeEvent} through a Contact where the name has
	 * already been set.
	 *
	 * @param user      the {@link User} who wants to join or leave a group
	 * @param group     the {@link Group} he wants to join or leave
	 * @param operation whether the user should be removed from this group. If
	 *                  false, this user will be added.
	 * @since Envoy Common v0.2-alpha
	 */
	public GroupResizeEvent(User user, Group group, Operation operation) {
		super(user.getID());
		if (group.getMemberIDs().contains(user.getID())) {
			if (operation.equals(Operation.ADD)) throw new IllegalStateException(
					"Cannot add " + user + " to group " + group.getID() + " because he is already a member of this group");
		} else if (operation.equals(Operation.REMOVE))
			throw new IllegalStateException("Cannot remove " + user + " from group " + group.getID() + " because he is no part of this group");
		groupID				= group.getID();
		this.operation	= operation;
	}

	/**
	 * @return the ID of the {@link Contact} this event is related to
	 * @since Envoy Common v0.2-alpha
	 */
	public long getGroupID() { return groupID; }

	/**
	 * @return the operationType
	 * @since Envoy Common v0.1-beta
	 */
	public Operation getOperation() { return operation; }

	/**
	 * {@inheritDoc}
	 */
	@Override
	public String toString() { return String.format("GroupResizeEvent[userid=%d,groupid=%d,operation=%s]", get(), groupID, operation); }
}