/*
 * Copyright (c) 2017 Jonas 'Sortie' Termansen.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 * hostname.c
 * Write or set the system hostname.
 */

#include <err.h>
#include <limits.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

// TODO: The Sortix <limits.h> doesn't expose this at the moment.
#if !defined(HOST_NAME_MAX) && defined(__sortix__)
#include <sortix/limits.h>
#endif

static void compact_arguments(int* argc, char*** argv)
{
	for ( int i = 0; i < *argc; i++ )
	{
		while ( i < *argc && !(*argv)[i] )
		{
			for ( int n = i; n < *argc; n++ )
				(*argv)[n] = (*argv)[n+1];
			(*argc)--;
		}
	}
}

int main(int argc, char* argv[])
{
	bool short_hostname = false;

	const char* argv0 = argv[0];
	for ( int i = 1; i < argc; i++ )
	{
		const char* arg = argv[i];
		if ( arg[0] != '-' || !arg[1] )
			continue;
		argv[i] = NULL;
		if ( !strcmp(arg, "--") )
			break;
		if ( arg[1] != '-' )
		{
			char c;
			while ( (c = *++arg) ) switch ( c )
			{
			case 's': short_hostname = true; break;
			default:
				fprintf(stderr, "%s: unknown option -- '%c'\n", argv0, c);
				exit(1);
			}
		}
		else if ( !strcmp(arg, "--short") )
			short_hostname = true;
		else
		{
			fprintf(stderr, "%s: unknown option: %s\n", argv0, arg);
			exit(1);
		}
	}

	compact_arguments(&argc, &argv);

	if ( 3 <= argc )
		errx(1, "unexpected extra operand");

	if ( argc == 2 )
	{
		if ( short_hostname )
			errx(1, "the -s option is incompatible with setting hostname");
		char* hostname = argv[1];
		if ( sethostname(hostname, strlen(hostname)) < 0 )
			err(1, "sethostname: %s", hostname);
		return 0;
	}

	char hostname[HOST_NAME_MAX + 1];
	if ( gethostname(hostname, sizeof(hostname)) < 0 )
		err(1, "gethostname");
	if ( short_hostname )
		hostname[strcspn(hostname, ".")] = '\0';
	puts(hostname);

	if ( ferror(stdout) || fflush(stdout) == EOF )
		err(1, "stdout");
	return 0;
}