// relogin.c, version 0.1.0
// OMKOV coreutils relogin
// Copyright (C) 2022, Jakob Wakeling
// MIT Licence

#include "util/error.h"
#include "util/optget.h"

#include <grp.h>
#include <pwd.h>
#include <sys/types.h>
#include <unistd.h>

#include <errno.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdnoreturn.h>
#include <string.h>

#define VERSION "0.1.0"

static struct lop lops[] = {
	{ "help",    ARG_NUL, 256 },
	{ "version", ARG_NUL, 257 },
	{ NULL, 0, 0 }
};

static inline int relogin(const char *user, char *av[]);

static void hlp(void);
static void ver(void);

int main(int ac, char *av[]) { A0 = av[0];
	struct opt opt = OPTGET_INIT; opt.str = ""; opt.lops = lops;
	for (int o; (o = optget(&opt, av, 1)) != -1;) switch (o) {
	case 256: { hlp(); return 0; }
	case 257: { ver(); return 0; }
	default: { return 1; }
	}
	
	if (opt.ind + 0 >= ac) { error(1, "missing user operand"); }
	if (opt.ind + 1 >= ac) { error(1, "missing command operand"); }
	
	if (relogin(av[1], &av[2])) { error(1, "%s: %s\n", av[1], serr()); }
	
	return 0;
}

static inline int relogin(const char *user, char *av[]) {
	struct passwd *pw;
	if ((pw = getpwnam(user)) == NULL) { error(1, "%s", serr()); }
	
	if (initgroups(pw->pw_name, pw->pw_gid) == -1) { error(1, "%s", serr()); }
	if (setgid(pw->pw_gid) == -1) { error(1, "%s", serr()); }
	if (setuid(pw->pw_uid) == -1) { error(1, "%s", serr()); }
	
	setenv("HOME", pw->pw_dir, 1); setenv("LOGNAME", pw->pw_name, 1);
	setenv("USER", pw->pw_name, 1); unsetenv("MAIL");
	
	unsetenv("DOAS_USER"); unsetenv("SUDO_UID"); unsetenv("SUDO_GID");
	unsetenv("SUDO_USER"); unsetenv("SUDO_COMMAND");
	
	if (execvp(av[0], &av[0]) == -1) { error(1, "%s", serr()); }
	
	return 0;
}

static void hlp(void) {
	puts("relogin - invoke a command as a specified user\n");
	puts("usage: relogin user command [argument...]\n");
	puts("options:");
	puts("  --help     Display help information");
	puts("  --version  Display version information");
}

static void ver() {
	puts("OMKOV coreutils relogin, version " VERSION);
	puts("Copyright (C) 2022, Jakob Wakeling");
	puts("MIT Licence (https://opensource.org/licenses/MIT)");
}