package ADT;

 import algorithms.util.StdOut;

 /******************************************************************************

  *  Compilation:  javac Date.java

  *  Execution:    java Date

  *  Dependencies: StdOut.java

  *

  *  An immutable data type for dates.

  *

  ******************************************************************************/

 /**

  *  The <tt>Date</tt> class is an immutable data type to encapsulate a

  *  date (day, month, and year).

  *  <p>

  *  For additional documentation,

  *  see <a href="http://algs4.cs.princeton.edu/12oop">Section 1.2</a> of

  *  <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.

  *

  *  @author Robert Sedgewick

  *  @author Kevin Wayne

  */

 public class Date implements Comparable<Date> {

     private static final int[] DAYS = { 0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

     private final int month;   // month (between 1 and 12)

     private final int day;     // day   (between 1 and DAYS[month]

     private final int year;    // year

    /**

      * Initializes a new date from the month, day, and year.

      * @param month the month (between 1 and 12)

      * @param day the day (between 1 and 28-31, depending on the month)

      * @param year the year

      * @throws IllegalArgumentException if this date is invalid

      */

     public Date(int month, int day, int year) {

         if (!isValid(month, day, year)) throw new IllegalArgumentException("Invalid date");

         this.month = month;

         this.day   = day;

         this.year  = year;

     }

     /**

      * Initializes new date specified as a string in form MM/DD/YYYY.

      * @param date the string representation of this date

      * @throws IllegalArgumentException if this date is invalid

      */

     public Date(String date) {

         String[] fields = date.split("/");

         if (fields.length != 3) {

             throw new IllegalArgumentException("Invalid date");

         }

         month = Integer.parseInt(fields[0]);

         day   = Integer.parseInt(fields[1]);

         year  = Integer.parseInt(fields[2]);

         if (!isValid(month, day, year)) throw new IllegalArgumentException("Invalid date");

     }

     /**

      * Return the month.

      * @return the month (an integer between 1 and 12)

      */

     public int month() {

         return month;

     }

     /**

      * Returns the day.

      * @return the day (an integer between 1 and 31)

      */

     public int day() {

         return day;

     }

     /**

      * Returns the year.

      * @return the year

      */

     public int year() {

         return year;

     }

     // is the given date valid?

     private static boolean isValid(int m, int d, int y) {

         if (m < 1 || m > 12)      return false;

         if (d < 1 || d > DAYS[m]) return false;

         if (m == 2 && d == 29 && !isLeapYear(y)) return false;

         return true;

     }

     // is y a leap year?

     private static boolean isLeapYear(int y) {

         if (y % 400 == 0) return true;

         if (y % 100 == 0) return false;

         return y % 4 == 0;

     }

     /**

      * Returns the next date in the calendar.

      *

      * @return a date that represents the next day after this day

      */

     public Date next() {

         if (isValid(month, day + 1, year))    return new Date(month, day + 1, year);

         else if (isValid(month + 1, 1, year)) return new Date(month + 1, 1, year);

         else                                  return new Date(1, 1, year + 1);

     }

     /**

      * Compares two dates chronologically.

      *

      * @param  that the other date

      * @return <tt>true</tt> if this date is after that date; <tt>false</tt> otherwise

      */

     public boolean isAfter(Date that) {

         return compareTo(that) > 0;

     }

     /**

      * Compares two dates chronologically.

      *

      * @param  that the other date

      * @return <tt>true</tt> if this date is before that date; <tt>false</tt> otherwise

      */

     public boolean isBefore(Date that) {

         return compareTo(that) < 0;

     }

     /**

      * Compares two dates chronologically.

      *

      * @return the value <tt>0</tt> if the argument date is equal to this date;

      *         a negative integer if this date is chronologically less than

      *         the argument date; and a positive ineger if this date is chronologically

      *         after the argument date

      */

     @Override

     public int compareTo(Date that) {

         if (this.year  < that.year)  return -1;

         if (this.year  > that.year)  return +1;

         if (this.month < that.month) return -1;

         if (this.month > that.month) return +1;

         if (this.day   < that.day)   return -1;

         if (this.day   > that.day)   return +1;

         return 0;

     }

     /**

      * Returns a string representation of this date.

      *

      * @return the string representation in the format MM/DD/YYYY

      */

     @Override

     public String toString() {

         return month + "/" + day + "/" + year;

     }

     /**

      * Compares this date to the specified date.

      *

      * @param  other the other date

      * @return <tt>true</tt> if this date equals <tt>other</tt>; <tt>false</tt> otherwise

      */

     @Override

     public boolean equals(Object other) {

         if (other == this) return true;

         if (other == null) return false;

         if (other.getClass() != this.getClass()) return false;

         Date that = (Date) other;

         return (this.month == that.month) && (this.day == that.day) && (this.year == that.year);

     }

     /**

      * Returns an integer hash code for this date.

      *

      * @return a hash code for this date

      */

     @Override

     public int hashCode() {

         int hash = 17;

         hash = 31*hash + month;

         hash = 31*hash + day;

         hash = 31*hash + year;

         return hash;

     }

     /**

      * Unit tests the <tt>Date</tt> data type.

      */

     public static void main(String[] args) {

         Date today = new Date(2, 25, 2004);

         StdOut.println(today);

         for (int i = 0; i < 10; i++) {

             today = today.next();

             StdOut.println(today);

         }

         StdOut.println(today.isAfter(today.next()));

         StdOut.println(today.isAfter(today));

         StdOut.println(today.next().isAfter(today));

         Date birthday = new Date(10, 16, 1971);

         StdOut.println(birthday);

         for (int i = 0; i < 10; i++) {

             birthday = birthday.next();

             StdOut.println(birthday);

         }

     }

 }