Logback: the reliable, generic, fast and flexible logging framework.
Copyright (C) 1999-2015, 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.
/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2015, 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.util;

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 SimpleDateFormat format). 
Author:
Ceki Gülcü/**
 * 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 datePatternLength;
    final CharSequenceToRegexMapper regexMapper = new CharSequenceToRegexMapper();

    public DatePatternToRegexUtil(String datePattern) {
        this.datePattern = datePattern;
        datePatternLength = datePattern.length();
    }

    public String toRegex() {
        List<CharSequenceState> charSequenceList = tokenize();
        StringBuilder sb = new StringBuilder();
        for (CharSequenceState seq : charSequenceList) {
            sb.append(regexMapper.toRegex(seq));
        }
        return sb.toString();
    }

    private List<CharSequenceState> tokenize() {
        List<CharSequenceState> sequenceList = new ArrayList<CharSequenceState>();

        CharSequenceState lastCharSequenceState = null;

        for (int i = 0; i < datePatternLength; i++) {
            char t = datePattern.charAt(i);
            if (lastCharSequenceState == null || lastCharSequenceState.c != t) {
                lastCharSequenceState = new CharSequenceState(t);
                sequenceList.add(lastCharSequenceState);
            } else {
                lastCharSequenceState.incrementOccurrences();
            }
        }
        return sequenceList;
    }
}