/**
   * Gives back the leaf nodes related to a given node
   *
   * @param position this node is the starting point to find leaves
   * @param leaves collection of all leaves
   */
  public Map<INode, IAttribute> collectLeaves(INode position, Map<INode, IAttribute> leaves) {

    // Create leaves set if not exists
    if (leaves == null) {
      leaves = new HashMap<INode, IAttribute>();
    }

    // If position is leaf
    if (position.isLeaf()) {
      System.out.println(position.getAttributesString());
      leaves.put(position, position.getAttributeValue(position));
      return leaves;
    }

    // If position is no leaf
    Iterator<INode> children = position.getChildren();

    while (children.hasNext()) {

      INode child = children.next();
      Map<INode, IAttribute> tempLeaves = (collectLeaves(child, leaves));
      for (INode tempLeaf : tempLeaves.keySet()) {
        if (!leaves.keySet().contains(tempLeaf)) {
          leaves.put(tempLeaf, tempLeaf.getAttributeValue(tempLeaf));
        }
      }
    }

    return leaves;
  }
  /**
   * Collect ratings of all content given by the input node
   *
   * @param position this is the starting point for collecting
   * @param inputNodeID this node defines the content that needs to be collected
   */
  public Map<Integer, IAttribute> collectRatings(
      INode position, INode testNode, Map<Integer, IAttribute> contentRatings) {

    // Create Map for content of test user with empty values if not existing
    if (contentRatings == null) {

      contentRatings = new HashMap<Integer, IAttribute>(); // DatasetID, AttributeData
      Set<INode> testContentKeys = testNode.getAttributeKeys();
      for (INode testContentKey : testContentKeys) {
        contentRatings.put((int) testContentKey.getDatasetId(), null);
      }
    }

    // Look for content nodes on the list and add it to collected ratings map
    Set<INode> posContentKeys = position.getAttributeKeys();
    Map<Integer, IAttribute> posContentMap = new HashMap<Integer, IAttribute>();
    for (INode posContentKey : posContentKeys) {

      // Find Dataset ID of Content Node -> FIXME: very inefficient
      int contentDatasetID = 0;
      for (Iterator<Entry<Integer, INode>> iter = leavesMapC.entrySet().iterator();
          iter.hasNext(); ) {
        Map.Entry<Integer, INode> e = (Map.Entry<Integer, INode>) iter.next();
        if (posContentKey.getId() == e.getValue().getId()) {
          contentDatasetID = e.getKey();
        }
      }

      posContentMap.put(contentDatasetID, position.getAttributeValue(posContentKey));
    }

    for (Entry<Integer, IAttribute> contentRating : contentRatings.entrySet()) {

      int datasetID = contentRating.getKey();
      IAttribute rating = contentRating.getValue();

      // Check if value still needs to be found
      if (rating == null) {

        try {
          IAttribute contentAttributes = posContentMap.get(datasetID);
          contentRatings.put(datasetID, posContentMap.get(datasetID));
        } catch (Exception e) {
          System.out.println(e);
        }
      }
    }

    // Check if all movies were found
    if (contentRatings.containsValue(null) != true) {
      return contentRatings;
    } else {

      // Go one level up if possible
      if (position.getParent() != null) {
        contentRatings = collectRatings(position.getParent(), testNode, contentRatings);
        if (contentRatings != null) {
          return contentRatings;
        }
      } else {
        return contentRatings;
      }
    }

    return null;
  }