package com.mystuff.juststuff;

import java.text.*;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.TreeSet;

public class Palindrome {
	SimpleDateFormat sdf;
	
	public Palindrome() {
		this.sdf = new SimpleDateFormat("MMddyyyy");
		sdf.setLenient(false);
	}

	public TreeSet<Date> countDatePalindromes(Date startDate, Date endDate) {
		TreeSet<Date> palSet = new TreeSet<Date>();
		GregorianCalendar startCal = new GregorianCalendar();
		GregorianCalendar endCal = new GregorianCalendar();


    /*
      end date is chronologically before start date. flip them.
      NOTE: lines 23-30 should be a pre-condition to the countDatePalindromes method,
      so they should be deleted.
    */
		if (startDate.getTime() > endDate.getTime()) {
			startCal.setTime(endDate);
			endCal.setTime(startDate);
		}else {
			startCal.setTime(startDate);
			endCal.setTime(endDate);
		}

		String regularDate = null;
		String palDate = null;
		while ( (startCal.before(endCal)) || (startCal.equals(endCal)) ) {
			regularDate = sdf.format(startCal.getTime());
			palDate = palindromify(startCal.getTime());			
      
      // a date palindrome was found
			if (regularDate.equals(palDate))
				palSet.add(startCal.getTime());
        
			startCal.add(Calendar.DAY_OF_MONTH, 1);
		}	
		return palSet;
	}
	
	private String palindromify(final Date arg) {
		StringBuffer palBuff = new StringBuffer(8);
    palBuff = sdf.format(arg, palBuff, new FieldPosition(0));
		return palBuff.reverse().toString();
	}

}