RecursiveNodeIterator.java

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/*
 * Project: Server for annotations sharing
 * Subproject: Position of fragment of text in XML document
 * Author: Peter Bartoš
 * Edited by: Ing. Jaroslav Dytrych idytrych@fit.vutbr.cz
 * File: RecursiveNodeIterator.java
 * Description: Recursive node iterator
 */

/**
 * @file RecursiveNodeIterator.java
 *
 * @brief Recursive node iterator
 */

package cz.vutbr.fit.knot.annotations.fragmentUpdater.nodeIterators;

import cz.vutbr.fit.knot.annotations.fragmentUpdater.XPathHelper;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import org.w3c.dom.Document;
import org.w3c.dom.Node;

/**
 * Recursive node iterator
 *
 * @brief Recursive node iterator
 * @author Peter Bartoš
 */
public class RecursiveNodeIterator extends NodeIterator {

  protected Node nextNode;
  protected boolean firstNode;
  protected long timestamp;

  /**
   * Overriden init() method
   *
   * @param document document whose nodes will be iterated through
   * @param expr XPath expression according to which iterating will be provided
   */
  @Override
  public void init(Document document, XPathExpression expr) throws XPathExpressionException {

    timestamp = System.currentTimeMillis();

    this.document = document;
    this.nodeList = XPathHelper.evaluateXPath(document, expr);
    this.currentNodeIndex = 0;
    firstNode = true;

    if (nodeList.getLength() == 0) {
      nextNode = null;
    } else {
      // First node which will be parsed
      nextNode = nodeList.item(currentNodeIndex);
      while (nextNode.hasChildNodes()) {
        nextNode = nextNode.getFirstChild();
      }
    }
  }  // init()

  /**
   *
   * Method for getting iterator's next node, recursive strategy is used.
   *
   * @return iterator's next node
   */
  @Override
  public Node nextNode() {

    Node resultNode, newNextNode;

    // There is no more node
    if (nextNode == null) {
      return null;
    }

    // First node is special, can be in the middle
    // After first node returned, begin from the 1st sibling in the level
    if (firstNode) {
      firstNode = false;
      resultNode = nextNode;
      nextNode = nextNode.getParentNode().getFirstChild();
      return resultNode;
    }

    // If it is a terminal node
    if (!nextNode.hasChildNodes()) {
      resultNode = nextNode;
      newNextNode = nextNode.getNextSibling();

      // If there is no sibling
      if (newNextNode == null) {
        // Parent of this node is now depleted
        setVisited(nextNode.getParentNode());

        // Default Next node is parent node
        nextNode = nextNode.getParentNode();

        // If there is a possibility, start from first node on parent level
        if (nextNode.getParentNode() != null) {
          nextNode = nextNode.getParentNode().getFirstChild();
        }
      } else {
        nextNode = newNextNode;
      }

      if (resultNode.getNodeName().equals("#text") && !isWhitespaced(resultNode.getTextContent())) {
        return resultNode;
      }

      return nextNode();

    } else {  // Some parent node

      if (isVisited(nextNode)) {

        newNextNode = nextNode.getNextSibling();

        if (newNextNode == null) {
          setVisited(nextNode.getParentNode());  // This parent node depleted
          nextNode = nextNode.getParentNode();
        } else {
          nextNode = newNextNode;
        }

        return nextNode();

      } else {  // node not visited
        nextNode = nextNode.getFirstChild();

        // Inception: Go deeper to the terminal node
        while (nextNode.hasChildNodes()) {
          nextNode = nextNode.getFirstChild();
        }

        return nextNode();
      }
    }  // Some parent node
  }  // nextNode()

  /**
   * Sets node's "visited" flag
   *
   * @param node node which flag is to be set
   */
  private void setVisited(Node node) {
    if (node == null) {
      return;
    }

    node.setUserData("visited", timestamp, null);
  }

  /**
   * Getter of node's "visited" flag
   *
   * @param node node which flag is to be returned
   * @return true if "visited" flag is set, false if isn't
   */
  private boolean isVisited(Node node) {
    if (node == null) {
      return true;
    }

    Long visited = (Long) node.getUserData("visited");
    if (visited == null) {
      return false;
    }

    return (visited == timestamp);
  }

  /**
   * Finds out if string is consists of whitespaces
   *
   * @param string string to be examined
   * @return true if is whitespace, false if not
   */
  protected boolean isWhitespaced(String string) {
    return string.matches("\\s+");
  }

  /**
   * Overriden toString() method
   *
   * @return string representation of class
   */
  @Override
  public String toString() {
    return "Recursive";
  }
}  // class RecursiveNodeIterator