Times.java

package uk.bl.wa.extract;

/*
 * #%L
 * warc-indexer
 * $Id:$
 * $HeadURL:$
 * %%
 * Copyright (C) 2013 - 2014 The UK Web Archive
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as
 * published by the Free Software Foundation, either version 2 of the
 * License, or (at your option) any later version.
 * 
 * This program 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 General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public
 * License along with this program.  If not, see
 * <http://www.gnu.org/licenses/gpl-2.0.html>.
 * #L%
 */

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Times {
	/**
	 * Extract date
	 * 
	 * http://stackoverflow.com/questions/6100353/extract-dates-from-web-page
	 * 
	 * @return Date object
	 * @throws ParseException 
	 */
	public static Date extractDate(String text) throws ParseException {
	    Date date = null;
	    boolean dateFound = false;

	    String year = null;
	    String month = null;
	    String monthName = null;
	    String day = null;
	    String hour = null;
	    String minute = null;
	    String second = null;
	    @SuppressWarnings("unused")
		String ampm = null;

	    String regexDelimiter = "[-:\\/.,]";
	    String regexDay = "((?:[0-2]?\\d{1})|(?:[3][01]{1}))";
	    String regexMonth = "(?:([0]?[1-9]|[1][012])|(Jan(?:uary)?|Feb(?:ruary)?|Mar(?:ch)?|Apr(?:il)?|May|Jun(?:e)?|Jul(?:y)?|Aug(?:ust)?|Sep(?:tember)?|Sept|Oct(?:ober)?|Nov(?:ember)?|Dec(?:ember)?))";
	    String regexYear = "((?:[1]{1}\\d{1}\\d{1}\\d{1})|(?:[2]{1}\\d{3}))";
	    String regexHourMinuteSecond = "(?:(?:\\s)((?:[0-1][0-9])|(?:[2][0-3])|(?:[0-9])):([0-5][0-9])(?::([0-5][0-9]))?(?:\\s?(am|AM|pm|PM))?)?";
	    String regexEndswith = "(?![\\d])";

	    // DD/MM/YYYY
	    String regexDateEuropean =
	        regexDay + regexDelimiter + regexMonth + regexDelimiter + regexYear + regexHourMinuteSecond + regexEndswith;

	    // MM/DD/YYYY
	    String regexDateAmerican =
	        regexMonth + regexDelimiter + regexDay + regexDelimiter + regexYear + regexHourMinuteSecond + regexEndswith;

	    // YYYY/MM/DD
	    String regexDateTechnical =
	        regexYear + regexDelimiter + regexMonth + regexDelimiter + regexDay + regexHourMinuteSecond + regexEndswith;

	    // see if there are any matches
	    Matcher m = checkDatePattern(regexDateEuropean, text);
	    if (m.find()) {
	        day = m.group(1);
	        month = m.group(2);
	        monthName = m.group(3);
	        year = m.group(4);
	        hour = m.group(5);
	        minute = m.group(6);
	        second = m.group(7);
	        ampm = m.group(8);
	        dateFound = true;
	    }

	    if(!dateFound) {
	        m = checkDatePattern(regexDateAmerican, text);
	        if (m.find()) {
	            month = m.group(1);
	            monthName = m.group(2);
	            day = m.group(3);
	            year = m.group(4);
	            hour = m.group(5);
	            minute = m.group(6);
	            second = m.group(7);
	            ampm = m.group(8);
	            dateFound = true;
	        }
	    }

	    if(!dateFound) {
	        m = checkDatePattern(regexDateTechnical, text);
	        if (m.find()) {
	            year = m.group(1);
	            month = m.group(2);
	            monthName = m.group(3);
	            day = m.group(3);
	            hour = m.group(5);
	            minute = m.group(6);
	            second = m.group(7);
	            ampm = m.group(8);
	            dateFound = true;
	        }
	    }

	    // construct date object if date was found
	    if(dateFound) {
	        String dateFormatPattern = "";
	        String dayPattern = "";
	        String dateString = "";

	        if(day != null) {
	            dayPattern = "d" + (day.length() == 2 ? "d" : "");
	        }

	        if(day != null && month != null && year != null) {
	            dateFormatPattern = "yyyy MM " + dayPattern;
	            dateString = year + " " + month + " " + day;
	        } else if(monthName != null) {
	            if(monthName.length() == 3) dateFormatPattern = "yyyy MMM " + dayPattern;
	            else dateFormatPattern = "yyyy MMMM " + dayPattern;
	            dateString = year + " " + monthName + " " + day;
	        }

	        if(hour != null && minute != null) {
	            //TODO ampm
	            dateFormatPattern += " hh:mm";
	            dateString += " " + hour + ":" + minute;
	            if(second != null) {
	                dateFormatPattern += ":ss";
	                dateString += ":" + second;
	            }
	        }

	        if(!dateFormatPattern.equals("") && !dateString.equals("")) {
	            //TODO support different locales?
	            SimpleDateFormat dateFormat = new SimpleDateFormat(dateFormatPattern.trim(), Locale.US);
	            date = dateFormat.parse(dateString.trim());
	        }
	    }

	    return date;
	}

	private static Matcher checkDatePattern(String regex, String text) {
	    Pattern p = Pattern.compile(regex, Pattern.CASE_INSENSITIVE | Pattern.DOTALL);
	    return p.matcher(text);
	}
}