/* An instance of this class represents a time of day (e.g. 6:34AM)
** precise to the minute.
**
** Date: January 2025
** Authors: R. McCloskey and CMPS 144 students
*/

public class TimeOfDay { 

   // symbolic constants
   // ------------------

   public static final int HOURS_PER_DAY = 24;
   public static final int MINUTES_PER_HOUR = 60;

   // instance variables
   // ------------------

   private int hour;   // # of complete hours to have elapsed since midnight
   private int minute; // # of complte minutes to have elapsed since the
                       // beginning of current hour.
                       
   // class invariant:
   //   0 <= hour < HOURS_PER_DAY  and  0 <= minute < MINUTES_PER_HOUR
   

   // constructors
   // ------------

   /* Initializes this TimeOfDay object to represent the time of day
   ** described by the two parameters, which represent, respectively, the
   ** # of hours since midnight and the # minutes since beginning of 
   ** current hour.
   */
   public TimeOfDay(int h, int m) { 
      this.hour = h;  this.minute = m;
   }

   /* Initializes this TimeOfDay object to represent midnight.
   */
   public TimeOfDay() { 
      this(0,0);  // invoke the constructor above and pass to it a pair of 0's
   }


   // observers
   // ---------
   
   /* Reports whether or not the time of day represented by this TimeOfDay 
   ** object falls in the AM (as opposed to the PM).  The assumption is that 
   ** the first half of the day is in the AM and that the PM begins at the
   ** day's midpoint.
   */
   public boolean isAM() { 
      return this.hour < HOURS_PER_DAY / 2;
      // overly-verbose alternative:
      //if (hour < HOURS_PER_DAY / 2) { return true; }
      //else { return false; }
   }
   
   /* Returns a description of the time of day represented by this
   ** TimeOfDay object, using 24-hour notation.
   ** Examples: "5:34", "17:06"
   */
   public String toString() {
      // Call twoDigitImageOf() to produce a string describing the number of 
      // minutes since the beginning of the current hour, including a leading
      // zero if necessary.
      String minuteStr = twoDigitImageOf(this.minute);

      return this.hour + (':' + minuteStr);
   }
   //RWM: Using an instance of the class java.text.DecimalFormat (from 
   //     Java's "standard library"), rather than the twoDigitImageOf()
   //     method, would probably be considered a better approach.

   
   /* Returns a value indicating the relationship (either "earlier than",
   ** "equal to", or "later than") between the times of day represented 
   ** by this TimeOfDay object and the given one (t).
   ** "Earlier than" is indicated by a negative return value;
   ** "equal to" is indicated by a return value of zero;
   ** "later than" is indicated by a positive return value.
   */
   public int compareTo(TimeOfDay t) {
      return 57;   // STUB
   }
   
   /* Reports whether or not this TimeOfDay object represents a time of day
   ** that is earlier in the day than the time of day represented by the
   ** given TimeOfDay object (t).
   */
   public boolean isEarlierThan(TimeOfDay t) {
      if (this.hour < t.hour) { return true; }
      else if (this.hour > t.hour) { return false; }
      else {  
         // The 'hour' values of the two objects are the same,
         // so the result is determined by their 'minute' values.
         return this.minute < t.minute;
      }
   }
   
   // mutators
   // --------
   
   /* Makes this TimeOfDay object identical to the given one.
   */
   public void setTo(TimeOfDay t) { 
      this.hour = t.hour;  this.minute = t.minute;
   }
   
   /* Changes the state of this TimeOfDay object so that the time of day that
   ** it represents has advanced by the given numbers of hours and minutes.
   */
   public void advanceBy(int h, int m) { 
      // Translate h hours and m minutes into a number of minutes;
      int minutesForward = (MINUTES_PER_HOUR * h) + m;

      // Advance by that many minutes, one at a time.
      for (int i=0; i != minutesForward; i++) {
         this.advanceByOneMinute();
      }
   }
   
   /* Changes the state of this TimeOfDay object so that the time of day that
   ** it represents has decreased (i.e., gone backwards in time) by the given
   ** numbers of hours and minutes.
   */
   public void decreaseBy(int h, int m) { 
      // STUB
   }
   
   
   // utility methods
   // ---------------

   /* Returns the "String image" of the given integer, with a leading zero
   ** included if it is less than 10.  For example, 45 maps to "45" and 
   ** 3 maps to "03".
   ** pre: k >= 0
   */
   private String twoDigitImageOf(int k) {
      String prefix; 
      // Make prefix equal to either "0" or "" (the empty string) according 
      // to whether or not, respectively, k is less than 10. 
      if (k < 10) { prefix = "0"; }
      else { prefix = ""; }

      return prefix + k;
   }
   //RWM: Using Java's "ternary operator", the if-else statement above
   //     could have been written as
   //         prefix = k < 10 ? "0" : "";
   //
   

   /* Changes the state of this TimeOfDay object so that the time of day that
   ** it represents has advanced by one minute.
   */
   protected void advanceByOneMinute() { 
      minute = minute + 1;
      if (minute == MINUTES_PER_HOUR) {
         minute = 0;      // roll over to zero and advance the hour
         hour = hour + 1;
         if (hour == HOURS_PER_DAY) {
            hour = 0;     // roll over to zero
         }
      }
   }

   /* Changes the state of this TimeOfDay object so that the time of day that
   ** it represents has decreased (i.e., gone backwards) by one minute.
   */
   protected void decreaseByOneMinute() { 
      // STUB
   }

}