package de.fhdw.wtf.context.model;
   
   import java.util.Collection;
   import java.util.Vector;
   
   import de.fhdw.wtf.context.core.ObjectFactoryProvider;
   import de.fhdw.wtf.context.core.TransactionManager;
   import de.fhdw.wtf.persistence.meta.UnidirectionalLink;
   import de.fhdw.wtf.persistence.meta.UserObject;
  import de.fhdw.wtf.persistence.utils.Tuple;
  
  public abstract class SymmetricRelationAccess {
  	
  	protected <T extends AnyType> T inverseGet(final AnyType anyType, final String association) {
  		final Collection<T> result = this.inverseGetCollection(anyType, association);
  		if (result.isEmpty()) {
  			return null;
  		} else {
  			return result.iterator().next();
  		}
  	}
  	
  	protected <T extends AnyType> Collection<T> inverseGetCollection(final AnyType anyType, final String association) {
  		final Vector<T> resultVector = new Vector<>();
  		final Collection<Tuple<UnidirectionalLink, UserObject>> databaseResults =
  				TransactionManager.getContext().inverseGet(association, anyType.getObject());
  		for (final Tuple<UnidirectionalLink, UserObject> databaseResult : databaseResults) {
  			final UserObject object = databaseResult.getSecond();
  			@SuppressWarnings("unchecked")
  			final T result = (T) ObjectFactoryProvider.instance().createObject(object);
  			resultVector.add(result);
  		}
  		return resultVector;
  	}
  }