#include <stdio.h>			/* Standard I/O routines     */
#include <stdlib.h>			/* Standard Library routines */
#include <unistd.h>			/* Standard UNIX routines    */
#include <time.h>			/* Time processing routines  */

/*
 * Miscellaneous #defines to satisfy lint
 */

#define printf		( void )printf
#define scanf		( void )scanf
#define fprintf		( void )fprintf
#define fflush		( void )fflush

/*
 * Useful constants for time processing routines
 */

#define TIME_ERR	( time_t )-1
#define NOW		( time_t * )0

/*
 * Hmmm ...
 */

#define YEAR( tmp )	 	( (tmp)->tm_year + 1900 )
#define MONTH( tmp )	 	( (tmp)->tm_mon )
#define WEEK_DAY( tmp )		( (tmp)->tm_wday )
#define MONTH_DAY( tmp )	( (tmp)->tm_mday )
#define DAY_NAME_STR( tmp )	( WeekDays[ WEEK_DAY(tmp) ] )
#define MONTH_NAME_STR( tmp )	( Month[ MONTH(tmp) ].MonthName )
#define DAYS_IN_MONTH( tmp )	( Month[ MONTH(tmp) ].MonthDays )

/*
 * These are ... The Days of the Week
 */

const char *WeekDays[ ] =
{
    "Sunday",
    "Monday",
    "Tuesday",
    "Wednesday",
    "Thursday",
    "Friday",
    "Saturday"
};

/*
 * An array of structures that contains the
 * name of and number of days in each month
 */

struct
{
    unsigned int MonthDays;
    const char *MonthName;
}
Month[ ] =
{
    { 31, "January" },
    { 28, "February" },
    { 31, "March" },
    { 30, "April" },
    { 31, "May" },
    { 30, "June" },
    { 31, "July" },
    { 31, "August" },
    { 30, "September" },
    { 31, "October" },
    { 30, "November" },
    { 31, "December" }
};

/*
 * Main -
 *    Gets relevant calendar information (either user-specified
 *    or from current time and date) and prints it in human
 *    readable form.
 *
 * Parameters -
 *    None
 *
 * Return value -
 *    Returns final program status
 *
 * Error conditions detected -
 *    Several program specific failure modes (individually documented)
 */

int
main( void )
{
    time_t Date;
    struct tm *tmDate;

#ifdef DEBUG
    /*
     * Set up a structure for user-entered info
     */

    static struct tm tmInfo;

    printf( "Enter the date in numerical form [M D Y]: " );
    fflush( stdout );

    /*
     * scanf(3s) is cheesy, but will work for our purposes
     */

    scanf( "%d", &tmInfo.tm_mon );		/* read month */
    scanf( "%d", &tmInfo.tm_mday );		/* read day   */
    scanf( "%d", &tmInfo.tm_year );		/* read year  */

    /*
     * User enters month as 1-12, but mktime(3c) expects 0-11
     */

    tmInfo.tm_mon--;

    /*
     * mktime(3c) expects year offset from 1900
     */

    tmInfo.tm_year -= 1900;

    /*
     * Convert user-entered info to UNIX internal time
     */

    Date = mktime( &tmInfo );

#else
    /*
     * Convert current time to UNIX internal time
     */

    Date = time( NOW );

#endif

    /*
     * Check to see that conversion succeeded - if not,
     * then we print failure status and exit the program
     */

    if( Date == TIME_ERR )
    {
	fprintf( stderr, "No information is available for that date\n" );
	return EXIT_FAILURE;
    }

    /*
     * Extract UNIX internal time so that we can display it
     */

    tmDate = localtime( &Date );

    printf( "Today is %s, %3.3s %d, %d\n", DAY_NAME_STR( tmDate ),
	    MONTH_NAME_STR( tmDate ), MONTH_DAY( tmDate ), YEAR( tmDate ) );

#ifdef DEBUG
    printf( "There are %d days this month\n", DAYS_IN_MONTH( tmDate ) );
#endif

    /*
     * Always return a value from main()
     */

    return EXIT_SUCCESS;
}