import java.util.regex.Pattern;
import java.util.regex.Matcher;

public class Interval {

    int startHour;
    int startMin;
    int endHour;
    int endMin;


    /** 
	Given a matcher, return the next occurence, converted to an int value
	@param m A matcher of a regular expression on a string, where
  	         it is assumed that the string matched will be a valid integer.
	@param str The original string (used for error messages)
    */

    public static int getNextInt(Matcher m, String str) {
	if (m.find()) {
	    return Integer.parseInt(m.group());
	} else {
	    throw new IllegalArgumentException(str + "is not in the expected format");
	}
     }

    /** 
	@param str A string representing an interval such as "1:20pm - 2:30pm"
    */


    public Interval(String str) {

	Matcher oneOrTwoDigitsMatcher  = Pattern.compile("\\d{1,2}").matcher(str);
	Matcher amOrPmMatcher  = Pattern.compile("[ap]m").matcher(str);

	// get the start hour---that's the first occurence of 1 or 2 digits

	this.startHour = getNextInt(oneOrTwoDigitsMatcher,str);
	this.startMin = getNextInt(oneOrTwoDigitsMatcher,str);
	this.endHour = getNextInt(oneOrTwoDigitsMatcher,str);
        this.endMin = getNextInt(oneOrTwoDigitsMatcher,str);

	if (amOrPmMatcher.find()) {
	    if (amOrPmMatcher.group().equals("pm") && startHour != 12) {
		startHour += 12;
	    }
	} else {
	    throw new IllegalArgumentException(str + "is not in the expected format");
	}


	if (amOrPmMatcher.find()) {
	    if (amOrPmMatcher.group().equals("pm") && endHour != 12) {
		endHour += 12;
	    }
	} else {
	    throw new IllegalArgumentException(str + "is not in the expected format");
	}

    }


    public int getStartHour() { return this.startHour;}
    public int getStartMin() { return this.startMin;}
    public int getEndHour() { return this.endHour;}
    public int getEndMin() { return this.endMin;}
    
}