// File:   date.cpp.  C++ source code for date objects.

#include <iostream.h>
#include "date.h"

//
// Function to assign a month, day, and year to the date object.
// There is no value checking--the function assumes that the caller 
// passes a legitimate date.
// Pre:  mo is an integer between 1 and 12.
//       dy is an integer between 1 and 31.
//       yr is an integer between 0 and 9999.
// Post: The date object has been assigned a date with month mo,
//       day dy, and year yr.
//

void date::AssignDate(int mo, int dy, int yr)
{
   month = mo;
   day   = dy;
   year  = yr;
}

//
// Function to display the date in MM/DD/YY format
// Pre:  The date object has a value.
// Post: The date has been displayed in format MM/DD/YY.
//

void date::DisplayShort( void )
{
   cout << month << '/' << day << '/' << (year % 100);
}

//
// Function to print the date to standard output in 
// verbose form, i.e., similar to October 31, 1998.
// Pre:  The date object has a value.
// Post: The date has been displayed in verbose format.
//

void date::DisplayVerbose( void )
{
   switch (month)
   {
      case 1:  cout << "January ";
               break;
      case 2:  cout << "February ";
               break;
      case 3:  cout << "March ";
               break;
      case 4:  cout << "April ";
               break;
      case 5:  cout << "May ";
               break;
      case 6:  cout << "June ";
               break;
      case 7:  cout << "July ";
               break;
      case 8:  cout << "August ";
               break;
      case 9:  cout << "September ";
               break;
      case 10: cout << "October ";
               break;
      case 11: cout << "November ";
               break;
      case 12: cout << "December ";
   }
   cout << day << ", " << year;
}

//
// Function to increment the date to the next day. 
// Pre:  The date object has a value.
// Post: The date has been incremented to the next day.
//

void date::NextDay( void )
{
   int DaysInMonth;   // number of days in date's month
   
   switch (month)
   {
      case 4: 
      case 6: 
      case 9: 
      case 11:  DaysInMonth = 30;
                break;
      case 1: 
      case 3: 
      case 5: 
      case 7: 
      case 8: 
      case 10: 
      case 12:  DaysInMonth = 31;
                break;
      case 2:  if (IsLeapYear() == true)
                   DaysInMonth = 29;
               else
                   DaysInMonth = 28;   
   }
   
   if (day < DaysInMonth)    // not a new month
      day = day + 1;
   else                      // new month
   {
      day = 1;
      if (month < 12)
         month = month + 1;
      else                   // new year
      {
         month = 1;
         year = year + 1;
      }
   }
}

// Function to check if the current year is a leap year
// Pre: the year has a positive value
// Post: return a boolean value, true if leap year, false
//       otherwise.
bool date::IsLeapYear()
{
    if ((year % 4 == 0) && (year % 100 != 0)
        || (year % 400 == 0))
        return true;
    else
        return false;
}