XHTML.java

/*
 * aitools utilities
 * Copyright (C) 2006 Noel Bush
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.

 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

package org.aitools.util.xml;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.jdom.Text;

/**
 * Utilities specific to (X)HTML handling.
 * 
 * @author <a href="mailto:noel@aitools.org">Noel Bush</a>
 */
public class XHTML {

  private static final Pattern XHTML_BREAK_LINE_REGEX = Pattern
      .compile("[\r\n]*(<(.+?:)?br( .*?)?/>|<(.+?:)?p( .+?)?>|</(.+?:)?p>)[\r\n]*");

  private static final Pattern PRE_REGEX = Pattern.compile("<(?:.+?:)?pre(?: .+?)?>(.+?)</(?:.+?:)?pre>",
      Pattern.DOTALL);

  private static final Pattern LINEFEED_REGEX = Pattern.compile("[\r\n]+");

  private static final String[] EMPTY_STRING_ARRAY = { "" };

  /**
   * Breaks a message into multiple lines at an (X)HTML <br/>, except if it comes at the beginning of the message,
   * or ending (X)HTML </p>.
   * 
   * @param input the string to break
   * @return one line per array item
   */
  public static String[] breakLines(String input) {
    // Null inputs return an empty string array.
    if (input == null) {
      return EMPTY_STRING_ARRAY;
    }
    // Trim all whitespace at beginning and end.
    String _input = input.trim();

    // Empty trimmed inputs return an empty string array.
    if (_input.equals("")) {
      return EMPTY_STRING_ARRAY;
    }

    // Split into lines.
    List<String> rawLines = Arrays.asList(XHTML_BREAK_LINE_REGEX.split(_input));

    // Preserve actual line breaks within <pre/> sections.
    List<String> preservedLines = new ArrayList<String>(rawLines.size());
    Matcher matcher;
    String normalizedLine;
    for (String line : rawLines) {
      matcher = PRE_REGEX.matcher(line);
      if (matcher.matches()) {
        for (String preLine : LINEFEED_REGEX.split(matcher.group(1))) {
          if (preLine.length() > 0) {
            preservedLines.add(preLine);
          }
        }
      }
      else {
        // Remove blank lines.
        normalizedLine = Text.normalizeString(line);
        if (normalizedLine.length() > 0) {
          preservedLines.add(normalizedLine);
        }
      }
    }

    return preservedLines.toArray(EMPTY_STRING_ARRAY);
  }

}