/*
 * This file is part of the DiffX library.
 *
 * For licensing information please see the file license.txt included in the release.
 * A copy of this licence can also be found at
 *   http://www.opensource.org/licenses/artistic-license-2.0.php
 */
package com.topologi.diffx.sequence;

import java.util.Stack;

import com.topologi.diffx.event.CloseElementEvent;
import com.topologi.diffx.event.DiffXEvent;
import com.topologi.diffx.event.OpenElementEvent;

/**
 * A utility class for event sequences.
 * 
 * @author Christophe Lauret
 * @version 3 April 2005
 * 
 * @since 0.6
 */
public final class EventSequenceUtils {

  /**
   * Prevent creation of instances.
   */
  private EventSequenceUtils() {
  }

  /**
   * Indicates whether the sequence corresponds to well-formed XML.
   * 
   * @param sequence The sequence.
   * 
   * @return <code>true</code> if the sequence is "well-formed";
   *         <code>false</code> otherwise.
   */
  public static boolean isWellFormed(EventSequence sequence) {
    // TODO: if the sequence is null ??
    if (sequence == null) return false;
    Stack<DiffXEvent> open = new Stack<DiffXEvent>();
    DiffXEvent e = null;
    for (int i = 0; i < sequence.size(); i++) {
      e = sequence.getEvent(i);
      if (e instanceof OpenElementEvent) {
        open.push(e);
      } else if (e instanceof CloseElementEvent) {
        if (open.empty()) return false;
        OpenElementEvent o = (OpenElementEvent)open.peek();
        String lastOpenElementName = o.getName();
        String closeElementName = ((CloseElementEvent)e).getName();
        if (!closeElementName.equals(lastOpenElementName)) return false;
      }
    }
    return open.empty();
  }

  /**
   * Returns the maximum depth of the sequence.
   * 
   * <p>This method assumes that the sequence is well-formed, and counts
   * the maximum number of open element events.
   * 
   * @param sequence The sequence
   * 
   * @return The maximum depth.
   */
  public static int getMaxDepth(EventSequence sequence) {
    int max = 0;
    int depth = 0;
    for (int i = 0; i < sequence.size(); i++) {
      if (sequence.getEvent(i) instanceof OpenElementEvent) {
        depth++;
      } else if (sequence.getEvent(i) instanceof CloseElementEvent) {
        depth--;
      }
      if (depth > max) {
        max = depth;
      }
    }
    return max;
  }

  /**
   * Returns the maximum number of token inside an element tag.
   * 
   * <p>This method assumes that the sequence is well-formed.
   * 
   * @param sequence The sequence.
   * 
   * @return The maximum number of tokens.
   */
  public static int getMaxElementContent(EventSequence sequence) {
    int max = 0;
    int tmp = 0;
    for (int i = 0; i < sequence.size(); i++) {
      DiffXEvent e = sequence.getEvent(i);
      if (e instanceof OpenElementEvent) {
        tmp = 0;
      } else if (e instanceof CloseElementEvent) {
        if (tmp > max) {
          max = tmp;
        }
      } else {
        tmp++;
      }
    }
    return max;
  }

}