#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <time.h>
#include <exec/types.h>
#include <libraries/dosextens.h>

static int  tz_hour_diff =      0;
static int  tz_minutes_diff =   0;

static char *monthNames[12] = {
    "Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Nov","Dec"
    };

int
ConvertUTC(const char *s, int hourDiff, int minuteDiff, char *dosDate)
{
#define	EPOCH		40587					/* UNIX starts JD 2440587, */
#define	TIME		"%05ld %03d %02d%02d%02d UTC"
    int         result = 0;
    time_t      now;
    long	    julian;
    int		    day_of_year;
    int		    hour;
    int		    min;
    int		    sec;
    struct tm   *lt;

	if(sscanf(s,TIME, &julian, &day_of_year, &hour, &min, &sec) != 5)
	{
        fprintf(stderr,"Garbled time code: %s\n", s);
		result = 1;
	}
	else {
		now = (((julian - EPOCH) * 24 + hour) * 60 + min) * 60 + sec;
        now += ((minuteDiff * 60) + (hourDiff * 3600));
        lt = localtime(&now);
        sprintf(dosDate,"%d-%s-%d %02d:%02d:%02d",
                lt->tm_mday,
                monthNames[lt->tm_mon],
                lt->tm_year,
                lt->tm_hour,
                lt->tm_min,
                lt->tm_sec);
        fprintf(stderr,"GMT time: %s\n", dosDate);
    }
    return result;
}

main(argc, argv)
    int argc;
    char **argv;
{
#define UTC_LENGTH      20      /* length of UTC string */
    int     argn = 0;
    int     gotit = 0;
    int     leng;
    int     returnValue = 0;
    char    lastString[81];
    char    timeString[81];

    while (++argn < argc) {
        if (strcmp(argv[argn], "-h") == 0) {
            tz_hour_diff = atoi(argv[++argn]);
            if (tz_hour_diff < -12 || tz_hour_diff > 12) {
                fprintf(stderr,"%s: bad delta hours value!\n", argv[0]);
                return 1;
            }
        }
        else if (strcmp(argv[argn], "-m") == 0) {
            tz_minutes_diff = atoi(argv[++argn]);
            if (tz_minutes_diff < -59 || tz_minutes_diff > 59) {
                fprintf(stderr,"%s: bad delta minutes value!\n", argv[0]);
                return 1;
            }
        }
        else if (*argv[argn] == '-') {
usage:
            fprintf(stderr,
                    "Usage: %s [-h <hours>] [-m <minutes>] [ <filename> ]\n", argv[0]);
            fprintf(stderr,
                    "<hours> (+-12) and <minutes> (+-59) are your time delta from GMT.\n");
            fprintf(stderr,
                    "If <filename> is not given, standard input is assumed.\n");
        }
        else {
            if ( (argc - argn) > 1) goto usage;
            if (! freopen(argv[argn], "r", stdin) ) {
                fprintf(stderr,"%s: %s would not open for input!\n",
                        argv[0], argv[argn]);
                return 1;
            }
            break;
        }
    }
    /* Scan standard input (normally a pipe or file), looking for valid universal
     * time code strings. Save the last one for conversion. 
     */
    while (gets(timeString)) {
        leng = strlen(timeString);
        if (leng >= UTC_LENGTH) {
            if (strcmp(timeString+leng-3, "UTC") == 0) {
                gotit = 1;
                strcpy(lastString, timeString);
                break;
            }
        }
    }
    if (gotit) {
        if ((returnValue = 
             ConvertUTC(lastString, tz_hour_diff, tz_minutes_diff, timeString)) == 0) {
            fprintf(stderr, "%s\n", timeString);
            fexecl("Date","Date",timeString,NULL);
            returnValue = wait();
        }
    }
    else {
        fprintf(stderr,"No UTC strings found in input file!\n");
        returnValue =  1;
    }
    return returnValue;
}