//-------------------------------------------------------------------
//	season.cpp
//
//	This program prints the calendar for the first three months
//	of the year 1999.  Its purpose is to show what mathematical
//	calculations are needed when writing your calendar program.
//
//	    compile-and-link using:  $ g++ season.cpp -o season
//
//	programmer: ALLAN CRUSE
//	written on: 05 MAR 2006
//-------------------------------------------------------------------

#include <stdio.h>	// for printf(), perror() 

struct month_struct 	{
			char	month_name[ 4 ];
			int	days_in_month;
			int	first_weekday;
			int	day_name[ 42 ];
			};

struct month_struct month[ 12 ] = { {"JAN",31}, {"FEB",28}, 
	{"MAR",31}, {"APR",30}, {"MAY",31}, {"JUN",30}, {"JUL",31}, 
	{"AUG",31}, {"SEP",30}, {"OCT",31}, {"NOV",30}, {"DEC",31} };

int main( int argc, char **argv )
{
	int	year = 1999;		// specifies what year-number
	int	start_day = 5;		// year 1999 starts on Friday

	// adjustment of February-days for leap-years
	int	century = year / 100, leapyear;
	if ( (century % 4) == 0 ) leapyear = 1;
	else if ( (year % 4) == 0 ) leapyear = 1;
	else leapyear = 0;
	month[ 1 ].days_in_month += leapyear;

	// compute the starting weekday for each month		
	for (int mm = 0; mm < 12; mm++)
		{
		month[ mm ].first_weekday = start_day;
		start_day += month[ mm ].days_in_month;
		start_day %= 7;
		}

	// compute the nonzero day-numbers for each month
	for (int mm = 0; mm < 12; mm++)
		{
		int	start_day = month[ mm ].first_weekday;
		for (int dd = 0; dd < month[ mm ].days_in_month; dd++)
			{
			int	jj = start_day + dd;
			month[ mm ].day_name[ jj ] = 1 + dd;			
			}
		}

	// show a calendar for the winter season of that year
	printf( "\n\n      WINTER %d     \n\n", year );
	for (int mm = 0; mm < 3; mm++)
		{
		printf( "\n----------------------" );
		printf( "\n         %s           ", month[mm].month_name );
		printf( "\n----------------------" );
		for (int i = 0; i < 42; i++)
			{
			if ( ( i % 7 ) == 0 ) printf( "\n" );
			if ( month[ mm ].day_name[ i ] == 0 ) printf( "   " );
			else	printf( " %2d", month[ mm ].day_name[ i ] );
			} 
		printf( "\n\n" );
		}
}