/**
 * RegexDates.java
 *
 * Class to demonstrate how to use regular expressions from the 
 * Java 1.4 regex facility.
 *
 * This is just to get you started; changes will be needed to
 * do the full job.
 *
 * @author Marti Hearst 11/12/02
 * @version 1.0
 */



import java.io.*;
import java.util.regex.*;

public class RegexDates {


    private Pattern compiledRegex;
    private int monthIndex;
    private int dateIndex;
    private int yearIndex;

    /*
       The constructor code creates a regular expression compiler.
       It defines the regex patterns and where to find the various pieces,
       for use by matcher.group().

       This only covers a subset of all the date formats to be processed.
       More patterns will need to be added.

    */

    RegexDates() {

	String month = "(jan|feb|mar|april|may|jun|jul|aug|sep|oct|nov|dec)";
	String year =  "(?:19|20|')([0-9]{2})";
	String date =  "([1-3]?[0-9]),?";

	monthIndex = 1;
	dateIndex = 2;
	yearIndex = 3;

	String textPattern = month + " " + date + " " + year;
        compiledRegex = Pattern.compile(textPattern, Pattern.CASE_INSENSITIVE);
    }

    public Matcher getMatcher(String str) {
	return compiledRegex.matcher(str);
    }

    public String getMonth(Matcher m) {
	    return (m.group(monthIndex));
    }

    public String getDate(Matcher m) {
	return (m.group(dateIndex));
    }

    public String getYear(Matcher m) {
	return (m.group(yearIndex));
    }


    /* showMatches()

       This shows how to use the regex routines both to match a date and to extract out 
       and use the components of that date.

    */


    public void showMatches(String str) {

	Matcher matcher = getMatcher(str);
	try {

	    if (matcher.find()) {
		System.out.println("\nFound a valid date: " + matcher.group(0));
		System.out.println("\nMonth:\t " + getMonth(matcher) +
				   " Date:\t " + getDate(matcher) +
				   " Year:\t " + getYear(matcher));
	    } else {
		System.out.println("\nNo valid date: " + str);
	    }

	}
	catch(IllegalStateException e){
	    System.out.println("\nNo Match or Malformed Regular Expression:\n" +
			       e.getMessage());
	}
    }


    // This just demonstrates how to get started.
    // Your code will need to process input from a file.  See
    // http://javaalmanac.com/egs/java.util.regex/LineFilter2.html

    public static void main (String args[]) {

	String date1 = "jan 22, 2001";
	String date2 = "It is the case that May 1, '93 was an auspicious date.";
	String date3 = "feb 27, 201";
	RegexDates r = new RegexDates();
	r.showMatches(date1);
	r.showMatches(date2);
	r.showMatches(date3);

    }

}