/**
    * Logback: the reliable, generic, fast and flexible logging framework.
    * Copyright (C) 1999-2011, QOS.ch. All rights reserved.
    *
    * This program and the accompanying materials are dual-licensed under
    * either the terms of the Eclipse Public License v1.0 as published by
    * the Eclipse Foundation
    *
    *   or (per the licensee's choosing)
   *
   * under the terms of the GNU Lesser General Public License version 2.1
   * as published by the Free Software Foundation.
   */
  package ch.qos.logback.core.rolling.helper;
  
  import java.text.SimpleDateFormat;
  import java.util.ArrayList;
  import java.util.List;
  
  /**
   * This class is concerned with computing a regex corresponding to a date
   * pattern (in {@link SimpleDateFormat} format).
   * 
   * @author Ceki Gülcü
   * 
   */
  public class DatePatternToRegexUtil {
  
    final String datePattern;
    final int length;
  
    DatePatternToRegexUtil(String datePattern) {
      this.datePattern = datePattern;
      length = datePattern.length();
    }
  
    String toRegex() {
      List<SequenceToRegex4SDF> sequenceList = tokenize();
      StringBuilder sb = new StringBuilder();
      for (SequenceToRegex4SDF seq : sequenceList) {
        sb.append(seq.toRegex());
      }
      return sb.toString();
    }
  
    private List<SequenceToRegex4SDF> tokenize() {
      List<SequenceToRegex4SDF> sequenceList = new ArrayList<SequenceToRegex4SDF>();
      SequenceToRegex4SDF sequence = null;
      for (int i = 0; i < length; i++) {
        char t = datePattern.charAt(i);
        if (sequence == null || sequence.c != t) {
          sequence = addNewSequence(sequenceList, t);
        } else {
          sequence.inc();
        }
      }
      return sequenceList;
    }
  
    SequenceToRegex4SDF addNewSequence(List<SequenceToRegex4SDF> sequenceList,
        char t) {
      SequenceToRegex4SDF token = new SequenceToRegex4SDF(t);
      sequenceList.add(token);
      return token;
    }
  }