/*
 * Copyright (C) 2021, 2022  P. J. McDermott
 *
 * This file is part of @
 *
 * @ is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * @ is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with @.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <errno.h>
#include <inttypes.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include "config.h"
#include "datetime.h"

#if defined(HAVE_GETOPT_LONG) && HAVE_GETOPT_LONG
#include <getopt.h>
#endif

extern const char *PACKAGE_VERSION_GIT;

#if defined(HAVE_GETOPT_LONG) && HAVE_GETOPT_LONG
static const struct option LONGOPTS_[] = {
	{
		.name    = "list-formats",
		.has_arg = 0,
		.flag    = NULL,
		.val     = 'F',
	},
	{
		.name    = "help",
		.has_arg = 0,
		.flag    = NULL,
		.val     = 'h',
	},
	{
		.name    = "version",
		.has_arg = 0,
		.flag    = NULL,
		.val     = 'V',
	},
};
#endif

static struct tm EPOCH_ = {
	.tm_sec   = 0,
	.tm_min   = 0,
	.tm_hour  = 0,
	.tm_mday  = 1,
	.tm_mon   = 0,
	.tm_year  = 70,
	.tm_wday  = 4,
	.tm_yday  = 0,
	.tm_isdst = -1,
};

static void
_print_usage(FILE *stream, const char *program_name)
{
	fprintf(stream, "Usage: %s [date]time\n", program_name);
}

static void
_print_help(const char *program_name)
{
	_print_usage(stdout, program_name);
	puts("Options:");
#if defined(HAVE_GETOPT_LONG) && HAVE_GETOPT_LONG
	puts("\t-F, --list-formats  List all supported date and time formats");
	puts("\t-h, --help          Show this help information");
	puts("\t-V, --version       Show version information");
#else
	puts("\t-F  List all supported date and time formats");
	puts("\t-h  Show this help information");
	puts("\t-V  Show version information");
#endif
}

static void
_list_formats(void)
{
	time_t     tim;
	struct tm *tm;
	char      *out;
	size_t     buf_sz;
	char      *buf;
	size_t     i;

	tim = time(NULL);
	tm  = localtime(&tim);

	puts("Time formats:");
	i = 0;
	while (datetime_strftime_time(tm, &out, &buf_sz, &buf, &i) > 0) {
		if (out[0] == '\0') {
			continue;
		}
		printf("  * %s\n", out);
	}

	puts("Date formats:");
	i = 0;
	while (datetime_strftime_date(tm, &out, &buf_sz, &buf, &i) > 0) {
		if (out[0] == '\0') {
			continue;
		}
		printf("  * %s\n", out);
	}

	puts("Additional formats:");
	i = 0;
	while (datetime_strftime_misc(tm, &out, &buf_sz, &buf, &i) > 0) {
		if (out[0] == '\0') {
			continue;
		}
		printf("  * %s\n", out);
	}
}

static void
_print_version(void)
{
	printf("@ (atsign) %s%s\n", PACKAGE_VERSION, PACKAGE_VERSION_GIT);
	puts("Copyright (C) 2021  P. J. McDermott");
	puts("License GPLv3+: GNU GPL version 3 or later "
			"<http://gnu.org/licenses/gpl.html>.");
	puts("This is free software: you are free to change and redistribute "
			"it.");
	puts("There is NO WARRANTY, to the extent permitted by law.\n");
	printf("Please report bugs to <%s>.\n", PACKAGE_BUGREPORT);
}

static char *
_concat_args(int argc, char * const argv[])
{
	int   buf_l;
	int   i;
	char *buf;
	int   buf_i;
	int   j;

	buf_l = 0;
	for (i = 0; i < argc; ++i) {
		buf_l += strlen(argv[i]) + 1;
	}

	buf = calloc(buf_l, sizeof(*buf));
	if (buf == NULL) {
		fprintf(stderr, "Failed to allocate buffer: %s\n",
				strerror(errno));
		return NULL;
	}

	buf_i = 0;
	for (i = 0; i < argc; ++i) {
		for (j = 0; argv[i][j] != '\0'; ++j) {
			buf[buf_i++] = argv[i][j];
		}
		buf[buf_i++] = ' ';
	}
	buf[--buf_i] = '\0';

	return buf;
}

int
main(int argc, char * const argv[])
{
	bool    dbg;
	int     opt;
	char   *buf;
	time_t  arg;
	time_t  now;
	double  dif;

	dbg = false;
	optind = 1;
	opterr = 0;
#if defined(HAVE_GETOPT_LONG) && HAVE_GETOPT_LONG
	while ((opt = getopt_long(argc, argv, "FhVd", LONGOPTS_, NULL)) > 0) {
#else
	while ((opt = getopt(argc, argv, "FhVd")) > 0) {
#endif
		switch (opt) {
			case 'F':
				_list_formats();
				return EXIT_SUCCESS;
			case 'h':
				_print_help(argv[0]);
				return EXIT_SUCCESS;
			case 'V':
				_print_version();
				return EXIT_SUCCESS;
			case 'd':
				dbg = true;
				break;
			default:
				_print_usage(stderr, argv[0]);
#if defined(HAVE_GETOPT_LONG) && HAVE_GETOPT_LONG
				fprintf(stderr, "Try '%s --help' for more "
						"information.\n", argv[0]);
#else
				fprintf(stderr, "Try '%s -h' for more "
						"information.\n", argv[0]);
#endif
				return EXIT_FAILURE;
		}
	}
	argc -= optind;
	argv += optind;

	buf = _concat_args(argc, argv);
	if (buf == NULL) {
		return EXIT_FAILURE;
	}

	if (datetime_parse(buf, &arg) < 0) {
		free(buf);
		return EXIT_FAILURE;
	}
	free(buf);

	if (dbg == true) {
		now = timegm(&EPOCH_);
		dif = difftime(arg, now);
		printf("%" PRId64 "\n", (int64_t) dif);
		return EXIT_SUCCESS;
	}

	time(&now);
	dif = difftime(arg, now);
	if (dif >= 1000 * 24 * 60 * 60) {
		fputs("Date too far in the future\n", stderr);
		return EXIT_FAILURE;
	}

	setvbuf(stdout, NULL, _IONBF, 0);
	while (dif > 0) {
		printf("\r%03d:%02d:%02d:%02d",
				(int) dif / 60 / 60 / 24,
				(int) dif / 60 / 60 % 24,
				(int) dif / 60 % 60,
				(int) dif % 60);
		sleep(1);
		time(&now);
		dif = difftime(arg, now);
	}
	printf("\r000:00:00:00\n");

	return EXIT_SUCCESS;
}