package proj3;

public class Date implements Comparable {

   private static final int[] MAX_DAY_OF_MONTH = { 31, 28, 31, 30, 31, 30, 31,
         31, 30, 31, 30, 31 };
   private static final int[] MAX_DAY_OF_MONTH_LEAP = { 31, 29, 31, 30, 31,
         30, 31, 30, 31, 31, 30, 31 };
   private static final String[] MONTH_NAMES = { "Jan", "Feb", "Mar", "Apr",
         "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" };

   private int year;
   private int month;
   private int dayOfMonth;
   private boolean valid;

   public Date(int year, int month, int dayOfMonth) {
      this.year = year;
      this.month = month;
      this.dayOfMonth = dayOfMonth;
      int daysInMonth = getDaysInMonth(month, year);
      if ((dayOfMonth <=0) || (daysInMonth == 0))
         valid = false;
      else
         valid = dayOfMonth <= daysInMonth;
   }

   public int getYear() {
      return year;
   }

   public int getMonth() {
      return month;
   }

   public int getDayOfMonth() {
      return dayOfMonth;
   }

   public boolean isValid() {
      return valid;
   }

   private static boolean isLeapYear(int year) {
      if (year % 100 == 0)
         return year % 400 == 0;
      return year % 4 == 0;
   }

   private static int getDaysInMonth(int month, int year) {
      if (year < 1600)
         return 0;
      if ((month <= 0) || (month > 12))
         return 0;
      int[] daysInMonth = MAX_DAY_OF_MONTH;
      if (isLeapYear(year))
         daysInMonth = MAX_DAY_OF_MONTH_LEAP;
      return daysInMonth[month - 1];
   }

   public int compareTo(Object other) {
      Date otherDate = (Date) other;
      if (year != otherDate.year)
         return year - otherDate.year;
      if (month != otherDate.month)
         return month - otherDate.month;
      return dayOfMonth - otherDate.dayOfMonth;
   }
   
   public String toString() {
      String monthName;
      String invalidString = "";
      if ((month < 0) || (month > 12))
         monthName = "xxx";
      else
         monthName = MONTH_NAMES[month -1];
      if (!valid)
         invalidString = ", invalid";
      return monthName + " " + dayOfMonth + ", " + year + invalidString;
   }

}