package org.warp.commonutils.type;

import it.unimi.dsi.fastutil.objects.ObjectSet;
import java.util.Optional;
import java.util.Set;

/**
 * One to many relationship (not overlapping)
 *
 * o ------- o
 *      +--- o
 * o ---+--- o
 *      +--- o
 * o ------- o
 * o ------- o
 * o ---+--- o
 *      +--- o
 *
 * @param <T> Source type
 * @param <U> Destination type
 */
public interface Association<T, U> {

	/**
	 * Link source to dest
	 * @param src Source
	 * @param dest Destination
	 * @return true if linked, false if it was already linked with that destination
	 */
	boolean link(T src, U dest);

	/**
	 * Unlink only if src is linked with dest
	 * @param src Source
	 * @param dest Destination
	 * @return true if unlinked, false if not present
	 */
	boolean unlink(T src, U dest);

	/**
	 * Unlink
	 * @param src Source
	 * @return previous linked destinations
	 */
	Set<U> unlink(T src);

	/**
	 * Unlink
	 * @param dest Destination
	 * @return previous linked source
	 */
	Optional<T> unlinkFromSource(U dest);

	/**
	 * Check if link exists
	 * @param src Source
	 * @return true if source it's linked with at least 1 destination
	 */
	default boolean hasAnyLink(T src) {
		return !getLinks(src).isEmpty();
	}

	/**
	 * Check if link exists
	 * @param dest Destination
	 * @return true if destination is linked with a source
	 */
	default boolean hasLinkSource(U dest) {
		return getLinkSource(dest).isPresent();
	}

	/**
	 * Check if link exists
	 * @param src Source
	 * @param dest Destination
	 * @return true if source and destination are linked together
	 */
	boolean hasLink(T src, U dest);

	/**
	 * Get a link destination
	 * @param src Source
	 * @return Existing linked destinations
	 */
	Set<U> getLinks(T src);

	/**
	 * Get a link source
	 * @param dest Source
	 * @return Source if the link exists
	 */
	Optional<T> getLinkSource(U dest);

	/**
	 * Delete all links
	 */
	void clear();

	/**
	 * Get the count of existing links
	 * @return size
	 */
	int size();

	/**
	 * Get all the sources
	 * @return Set of sources
	 */
	ObjectSet<T> getSources();

	/**
	 * Get all the destinations
	 * @return Set of destinations
	 */
	ObjectSet<U> getDestinations();

	static <T, U> Association<T, U> synchronize(Association<T, U> association) {
		return new SynchronizedAssociation(association);
	}

	static <T, U> Association<T, U> synchronize(Association<T, U> association, Object lock) {
		return new SynchronizedAssociation(association, lock);
	}
}