
package de.ivu.elect.presentation.stimmeingabe;

/*
 * The Alphanum Algorithm is an improved sorting algorithm for strings containing numbers. Instead of sorting numbers in
 * ASCII order like a standard sort, this algorithm sorts numbers in numeric order.
 *
 * The Alphanum Algorithm is discussed at http://www.DaveKoelle.com
 *
 *
 * 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 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
 */

import java.util.Comparator;

import org.apache.commons.lang3.StringUtils;

/**
 * This is an updated version with enhancements made by Daniel Migowski, Andre Bogus, and David Koelle
 *
 * To convert to use Templates (Java 1.5+): - Change "implements Comparator" to "implements Comparator<String>" - Change "compare(Object o1, Object o2)" to "compare(String s1, String s2)" - Remove the
 * type checking and casting in compare().
 *
 * To use this class: Use the static "sort" method from the java.util.Collections class: Collections.sort(your list, new AlphanumComparator());
 */
public class AlphanumComparator implements Comparator<String> {

  private boolean isDigit(char ch) {
    return ch >= 48 && ch <= 57;
  }

  /** Length of string is passed in for improved efficiency (only need to calculate it once) **/
  private String getChunk(String s, int slength, int smarker) {
    StringBuilder chunk = new StringBuilder();
    int marker = smarker;
    char c = s.charAt(marker);
    chunk.append(c);
    marker++;
    if (isDigit(c)) {
      while (marker < slength) {
        c = s.charAt(marker);
        if (!isDigit(c)) {
          break;
        }
        chunk.append(c);
        marker++;
      }
    } else {
      while (marker < slength) {
        c = s.charAt(marker);
        if (isDigit(c)) {
          break;
        }
        chunk.append(c);
        marker++;
      }
    }
    return chunk.toString();
  }

  @Override
  public int compare(String s1, String s2) {

    if (s1 == null || StringUtils.isBlank(s1)) {
      if (s2 == null || StringUtils.isBlank(s2)) {
        return 0;
      }
      return 1;
    }
    if (s2 == null || StringUtils.isBlank(s2)) {
      return -1;
    }

    int thisMarker = 0;
    int thatMarker = 0;
    int s1Length = s1.length();
    int s2Length = s2.length();

    while (thisMarker < s1Length && thatMarker < s2Length) {
      String thisChunk = getChunk(s1, s1Length, thisMarker);
      thisMarker += thisChunk.length();

      String thatChunk = getChunk(s2, s2Length, thatMarker);
      thatMarker += thatChunk.length();

      // If both chunks contain numeric characters, sort them numerically
      int result = 0;
      if (isDigit(thisChunk.charAt(0)) && isDigit(thatChunk.charAt(0))) {
        // Simple chunk comparison by length.
        int thisChunkLength = thisChunk.length();
        result = thisChunkLength - thatChunk.length();
        // If equal, the first different number counts
        if (result == 0) {
          for (int i = 0; i < thisChunkLength; i++) {
            result = thisChunk.charAt(i) - thatChunk.charAt(i);
            if (result != 0) {
              return result;
            }
          }
        }
      } else {
        result = thisChunk.compareTo(thatChunk);
      }

      if (result != 0) {
        return result;
      }
    }

    return s1Length - s2Length;
  }
}
