package de.fhdw.wtf.context.model.collections;
   
   import java.util.Iterator;
   
   import de.fhdw.wtf.context.core.ObjectFactoryProvider;
   import de.fhdw.wtf.context.core.TransactionManager;
   import de.fhdw.wtf.context.model.Anything;
   import de.fhdw.wtf.persistence.meta.Object;
   import de.fhdw.wtf.persistence.meta.UnidirectionalLink;
  import de.fhdw.wtf.persistence.utils.Tuple;
  
  /**
   * This class provides an Iterator for Persistant* with Links(Unidirectional).
   * 
   * @param <T>
   *            The underlying element type.
   */
  public class PersistenceIteratorWithLink<T extends Anything> implements Iterator<T> {
  	
  	/**
  	 * An iterator over the underlying links.
  	 */
  	private final Iterator<Tuple<UnidirectionalLink, Object>> unidirectionalLinkIterator;
  	
  	/**
  	 * The element read last through the iterator.
  	 */
  	private UnidirectionalLink lastRead;
  	
  	/**
  	 * True if at least one element has been read through the iterator.
  	 */
  	private boolean hasLast;
  	
  	/**
  	 * Creates a PersistenceIteratorWithLink.
  	 * 
  	 * @param unidirectionalLinks
  	 *            A collection of the underlying links.
  	 */
  	public PersistenceIteratorWithLink(final java.util.Collection<Tuple<UnidirectionalLink, Object>> unidirectionalLinks) {
  		this.unidirectionalLinkIterator = unidirectionalLinks.iterator();
  	}
  	
  	@Override
  	public boolean hasNext() {
  		return this.unidirectionalLinkIterator.hasNext();
  	}
  	
  	@Override
  	public T next() {
  		this.lastRead = this.unidirectionalLinkIterator.next().getFirst();
  		this.hasLast = true;
  		return this.provideNewInstanceForType(this.lastRead.getTarget());
  		
  	}
  	
  	@Override
  	public void remove() {
  		if (this.hasLast) {
  			TransactionManager.getContext().unset(this.lastRead);
  		}
  		this.unidirectionalLinkIterator.remove();
  	}
  	
  	/**
  	 * Instantiates the Java object for the underlying database object.
  	 * 
  	 * @param object
  	 *            The database object.
  	 * @return The corresponding Java object.
  	 */
  	@SuppressWarnings("unchecked")
  	private T provideNewInstanceForType(final Object object) {
  		return (T) ObjectFactoryProvider.instance().createObject(object);
  	}
  	
  }