/* SPDX-License-Identifier: GPL-3.0-only */
/* SPDX-FileCopyrightText: 2026 afiw <afiw@linuxposting.xyz> */

/*
 * can - query filesystem permissions
 * Copyright (C) 2026 afiw <afiw@linuxposting.xyz>
 *
 * This program 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, exclusively version 3 of the License.
 *
 * This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#include <err.h>
#include <grp.h>
#include <pwd.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/stat.h>
#include "action.h"
#include "user.h"

bool can_user(struct passwd* pw, enum action action, char const* path) {
  gid_t groups_a[1];            /* just to be sure, passing stack memory or nullptr might invoke UB */
  gid_t* groups = groups_a;
  int ngroups = 0;
  struct stat st;
  if (stat(path, &st) == -1) {
    err(EXIT_FAILURE, "%s", path); }
  if (st.st_mode & other_bit_of_action(action)) {
    return true; }
  if (pw->pw_uid == st.st_uid) {
    if (st.st_mode & user_bit_of_action(action)) {
      return true; } }
  (void)getgrouplist(pw->pw_name, pw->pw_gid, groups, &ngroups); /* just to get the value of ngroups */
  groups = malloc(ngroups * sizeof(*groups));
  (void)getgrouplist(pw->pw_name, pw->pw_gid, groups, &ngroups); /* getgrouplist doesn't fail */  
  for (int i = 0; i < ngroups; ++i) {
    if (groups[i] == st.st_gid) {
      if (st.st_mode & group_bit_of_action(action)) {
        return true; } } }
  return false; }