/*
 * unixtime.c
 */

#include <libgen.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysexits.h>
#include <time.h>

/* symbols */
#define TRUE 1
#define FALSE 0
#define VERSION "0.2"

/* prototypes */
int  print_version(void);
int  print_help(void);

/* definition of extern objects */
char       *progname;
const char *version  = VERSION;

/*
 * main
 */
int main(int argc, char** argv) {
	int			i;
	int			j;
	char		c;
	char		*p;
	size_t      l;
	time_t		t = 0;
	struct tm	*tm;

	/* Store program name without path
	 * (will be used in e.g. error messages) */
	if( (progname = strdup(basename(argv[0]))) == NULL ) {
		fprintf(stderr, "%s: ", basename(argv[0]));
		perror(NULL);
		exit(EX_OSERR);
	}

	/* Parse command line options */
	for( i = 1 ; i < argc ; i++ ) {
		if(!strncmp("--", argv[i], 2)) {
		/* Current argument is a GNU long option */
			if(!strcmp(       "--help", argv[i])) {
				print_help();
				exit(EX_OK);
			} else if(!strcmp("--version", argv[i])) {
				print_version();
				exit(EX_OK);
			} else {
				fprintf(stderr, "%s: invalid option: %s\n", progname, argv[i]);
				fprintf(stderr, "Try '%s -h' for help.\n", progname);
				exit(EX_USAGE);
			}
		} else if(!strncmp("-", argv[i], 1)) {
		/* Current argument is one or more short options */
			p = argv[i];
			for( j = 1 ; (c = p[j]) != '\0' ; j++) {
				switch(c) {
				case 'h':
					print_help();
					exit(EX_OK);
					break;
				case 'V':
					print_version();
					exit(EX_OK);
					break;
				default:
					fprintf(stderr, "%s: invalid option: %c\n", progname, c);
					fprintf(stderr, "Try '%s -h' for help.\n", progname);
					exit(EX_USAGE);
				}
			}
		} else {
			/* This is the first argument, that is not an option. 
			 * It will be taken as timestamp. */
			t = atol(argv[i]);
			l = strlen(argv[i]);
			if((p = malloc(l + 1)) != NULL) {
				snprintf(p, l + 1, "%ld", t);
				if(strcmp(argv[i], p)) {
					fprintf(stderr, "%s: not integer: %s\n", progname, 
						argv[i]);
					exit(EX_DATAERR);
				}
				free(p);
			} else {
				fprintf(stderr, "%s: Warning: cannot allocate memory"
					" to do integer test on input.\n", progname);
			}
			break;
		}
	} 		

	p = ctime((& t));
	if(p == NULL) {
		fprintf(stderr, "%s: unrecognized date '%ld'.\n", progname, t);
		exit(EX_DATAERR);
	}
	fputs(p, stdout);
	exit(EX_OK);
}

int print_version( void ) {
	printf("%s Version %s\n",progname, version);
	return TRUE;
}

int print_help( void ) {
	time_t	t = 0;
	char	*p;
	char	*p2;

	printf("\n");
	printf("%s converts a unix timestamp into a human readable date.\n", 
		progname);
	printf("\n");
	printf("Usage: unixtime [<timestamp>]\n"
           "                [-h, --help] [-V, --version]\n");
	printf("\n");
	printf("Where <timestamp> is the number of seconds since the Epoch\n");
	if((p = strdup(ctime(& t))) != NULL) {
		/* ctime() return the date as string with an appended new line.
		 * Since we do not want the new line to be printed, we terminate
		 * the string at the position of the new line. */
		if((p2 = strstr(p, "\n")) != NULL)
			strcpy(p2, "\0");
		printf("(i.e. %s).\n", p);
		free(p);
	}
	printf("\n");

	return TRUE;
}