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Statistical sampling library for use in virtualdataset libraries, based on apache commons math 4
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/**
 * 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.DateFormatSymbols;

/**
 * This class supports mapping character sequences to
 * regular expressions as appropriate for SimpleDateFormatter.
 *
 * @author Ceki
 */
class CharSequenceToRegexMapper {

    DateFormatSymbols symbols = DateFormatSymbols.getInstance();

    String toRegex(CharSequenceState css) {
        final int occurrences = css.occurrences;
        final char c = css.c;
        switch (css.c) {
        case 'G':
        case 'z':
            return ".*";
        case 'M':
            if (occurrences <= 2)
                return number(occurrences);
            else if (occurrences == 3)
                return getRegexForShortMonths();
            else
                return getRegexForLongMonths();
        case 'y':
        case 'w':
        case 'W':
        case 'D':
        case 'd':
        case 'F':
        case 'H':
        case 'k':
        case 'K':
        case 'h':
        case 'm':
        case 's':
        case 'S':
            return number(occurrences);
        case 'E':
            if (occurrences >= 4) {
                return getRegexForLongDaysOfTheWeek();
            } else {
                return getRegexForShortDaysOfTheWeek();
            }
        case 'a':
            return getRegexForAmPms();
        case 'Z':
            return "(\\+|-)\\d{4}";
        case '.':
            return "\\.";
        case '\\':
            throw new IllegalStateException("Forward slashes are not allowed");
        case '\'':
            if (occurrences == 1) {
                return "";
            }
            throw new IllegalStateException("Too many single quotes");
        default:
            if (occurrences == 1) {
                return "" + c;
            } else {
                return c + "{" + occurrences + "}";
            }
        }
    }

    private String number(int occurrences) {
        return "\\d{" + occurrences + "}";
    }

    private String getRegexForAmPms() {
        return symbolArrayToRegex(symbols.getAmPmStrings());
    }

    private String getRegexForLongDaysOfTheWeek() {
        return symbolArrayToRegex(symbols.getWeekdays());
    }

    private String getRegexForShortDaysOfTheWeek() {
        return symbolArrayToRegex(symbols.getShortWeekdays());
    }

    private String getRegexForLongMonths() {
        return symbolArrayToRegex(symbols.getMonths());
    }

    String getRegexForShortMonths() {
        return symbolArrayToRegex(symbols.getShortMonths());
    }

    private String symbolArrayToRegex(String[] symbolArray) {
        int[] minMax = findMinMaxLengthsInSymbols(symbolArray);
        return ".{" + minMax[0] + "," + minMax[1] + "}";
    }

    static int[] findMinMaxLengthsInSymbols(String[] symbols) {
        int min = Integer.MAX_VALUE;
        int max = 0;
        for (String symbol : symbols) {
            int len = symbol.length();
            // some SENTINEL values can be empty strings, the month at index 12 or the weekday at index 0
            if (len == 0)
                continue;
            min = Math.min(min, len);
            max = Math.max(max, len);
        }
        return new int[] { min, max };
    }
}