/*
 * print out the number of seconds since the epoch, the current time,
 * and a pbreakdown of both the current local and UTC times
 *
 * Matt Bishop
 * -- May 22 2024	original program
 */
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <errno.h>

/*
 * translate number of the day of the week into a 3-char string
 * handle unknown and unexpected problems
 */
char *dow(int n)
{
	/* get the day corresponding to n, which is to be 0-6 */
	switch(n){
	case 0:		return("Sun");
	case 1:		return("Mon");
	case 2:		return("Tue");
	case 3:		return("Wed");
	case 4:		return("Thu");
	case 5:		return("Fri");
	case 6:		return("Sat");
	default:	return("???");	/* some other value, unknown day */
	}

	/* Can't happen */
	fprintf(stderr, "dow: went past switch with all returns\n");
	exit(1);
}

/*
 * translate number of the month into a 3-char string
 * handle unknown and unexpected problems
 */
char *moy(int n)
{
	/* get the month corresponding to n, which is to be 0-11 */
	switch(n){
	case 0:		return("Jan");
	case 1:		return("Feb");
	case 2:		return("Mar");
	case 3:		return("Apr");
	case 4:		return("May");
	case 5:		return("Jun");
	case 6:		return("Jul");
	case 7:		return("Aug");
	case 8:		return("Sep");
	case 9:		return("Oct");
	case 10:	return("Nov");
	case 11:	return("Dec");
	default:	return("???");	/* some other value. unknown month */
	}

	/* Can't happen */
	fprintf(stderr, "dow: went past switch with all returns\n");
	exit(1);
}

/*
 * print all the details about the time
 */
void prtime(struct tm *parts)
{
#ifdef TIME_ZOME
	printf("\tTime zone: %s (%d seconds offset from UTC time 0\n",
			parts->tm_zone, parts->tm_gmtoff);
#endif
	printf("\tIs it daylight savings time? %s\n",
				parts->tm_isdst ? "yes" : "no");
	printf("\tDay of the year: %d\n", parts->tm_yday);
	printf("\tDay of the week: %d (%s)\n",
				parts->tm_wday, dow(parts->tm_wday));
	printf("\tYear (-1900): %d (%d)\n", parts->tm_year,
				parts->tm_year + 1900);
	printf("\tMonth: %d (%s)\n", parts->tm_mon, moy(parts->tm_mon));
	printf("\tDay of the month: %d\n", parts->tm_mday);
	printf("\tHour: %d\n", parts->tm_hour);
	printf("\tMinute: %d\n", parts->tm_min);
	printf("\tSecond: %d\n", parts->tm_sec);
}

/*
 * we're off! The main routine
 */
int main(void)
{
	time_t tick;		/* seconds since the epoch */
	char *tock;		/* points to (ctime) date and time */
	struct tm *parts;	/* broken down time */

	/*
	 * get the internal representation of time
	 */
	if ((tick = time(NULL)) == -1){
		perror("time");
		return(1);
	}
	printf("time in seconds is %ld\n", (long) tick);

	/*
	 * print it as an intelligible character string
	 */
	if ((tock = ctime(&tick)) == NULL){
		perror("ctime");
		return(1);
	}

	/* now let's break it down */
	if ((parts = localtime(&tick)) == NULL){
		perror("localtime");
		return(1);
	}
	printf("Here are the details of the local time:\n");
	prtime(parts);

	/* and here it is in UTC */
	if ((parts = gmtime(&tick)) == NULL){
		perror("gmtime");
		return(1);
	}
	printf("Here are the details of the UTC time:\n");
	prtime(parts);

	/* th-th-that's all, folks! -- Porky Pig */
	return(0);
}