package de.fhdw.wtf.persistence.meta;
   
   /**
    * A class to represent a connection between two objects in the database. The UnidirectionalLink itself is an instance
    * of an association.
    * 
    */
   public abstract class Link extends InstanceItem {
   	
  	/**
  	 * The identity of the link in the database. This Id is unique.
  	 */
  	private final long id;
  	
  	/**
  	 * The owning User Object of the link.
  	 */
  	private final UserObject owner;
  	
  	/**
  	 * The targeted Object.
  	 */
  	private final Object target;
  	
  	/**
  	 * Provides the Type of this UnidirectionalLink.
  	 * 
  	 * @return Provides the association for which this link is an instance.
  	 */
  	public abstract Association getInstanceOf();
  	
  	/**
  	 * Getter for the Owner of this UnidirectionalLink.
  	 * 
  	 * @return Provides the User Object, which is the owner of this link.
  	 */
  	public UserObject getOwner() {
  		return this.owner;
  	}
  	
  	/**
  	 * Getter for the target of this UnidirectionalLink.
  	 * 
  	 * @return Provides an Object, which is the target of this link.
  	 */
  	public Object getTarget() {
  		return this.target;
  	}
  	
  	/**
  	 * Constructor for a new UnidirectionalLink, it should only be called by the Object Facade or Junit Test to
  	 * guarantee a valid consistency with the database.
  	 * 
  	 * @param id
  	 *            The Id of the UnidirectionalLink, determined by the database.
  	 * @param owner
  	 *            The owner of the this UnidirectionalLink. A User Object.
  	 * @param target
  	 *            The target of this link. An Object.
  	 */
  	public Link(final long id, final UserObject owner, final Object target) {
  		super();
  		this.id = id;
  		this.owner = owner;
  		this.target = target;
  	}
  	
  	@Override
  	public long getId() {
  		return this.id;
  	}
  	
  	@Override
  	public boolean equals(final java.lang.Object obj) {
  		if (!(obj instanceof Link)) {
  			return false;
  		}
  		
  		final Link link = (Link) obj;
  		return this.getOwner().equals(link.getOwner()) && this.getTarget().equals(link.getTarget());
  	}
  	
  	@Override
  	public int hashCode() {
  		return this.owner.hashCode() ^ this.target.hashCode();
  	}
  	
  	@Override
  	public String toString() {
  		return "UnidirectionalLink<" + this.getId() + ">";
  	}
  	
  	@Override
  	public boolean isTheSameAs(final java.lang.Object other) {
  		if (!(other instanceof Link)) {
  			return false;
  		}
  		
  		return this.getId() == ((Link) other).getId();
 	}
 	
 }