/*
 * Copyright (c) 2020, Fei Wu <f.eiwu@yahoo.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <AK/String.h>
#include <AK/StringBuilder.h>
#include <LibCore/ArgsParser.h>
#include <ctype.h>
#include <dirent.h>
#include <errno.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>

int main(int argc, char** argv)
{
    const char* username = nullptr;
    bool remove_home = false;

    Core::ArgsParser args_parser;
    args_parser.add_option(remove_home, "Remove home directory", "remove", 'r');
    args_parser.add_positional_argument(username, "Login user identity (username)", "login");
    args_parser.parse(argc, argv);

    char temp_filename[] = "/etc/passwd.XXXXXX";
    auto fd = mkstemp(temp_filename);
    if (fd == -1) {
        perror("failed to create temporary file");
        return 1;
    }

    FILE* temp_file = fdopen(fd, "w");
    if (!temp_file) {
        perror("fdopen");
        if (unlink(temp_filename) < 0) {
            perror("unlink");
        }

        return 1;
    }

    bool user_exists = false;
    String home_directory;

    int rc = 0;
    setpwent();
    for (auto* pw = getpwent(); pw; pw = getpwent()) {
        if (strcmp(pw->pw_name, username)) {
            if (putpwent(pw, temp_file) != 0) {
                perror("failed to put an entry in the temporary passwd file");
                rc = 1;
                break;
            }
        } else {
            user_exists = true;
            if (remove_home)
                home_directory = pw->pw_dir;
        }
    }
    endpwent();

    if (fclose(temp_file)) {
        perror("fclose");
        if (!rc)
            rc = 1;
    }

    if (rc == 0 && !user_exists) {
        fprintf(stderr, "specified user doesn't exist\n");
        rc = 6;
    }

    if (rc == 0 && chmod(temp_filename, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)) {
        perror("chmod");
        rc = 1;
    }

    if (rc == 0 && rename(temp_filename, "/etc/passwd") < 0) {
        perror("failed to rename the temporary passwd file");
        rc = 1;
    }

    if (rc) {
        if (unlink(temp_filename) < 0) {
            perror("unlink");
        }
        return rc;
    }

    if (remove_home) {
        if (home_directory == "/") {
            fprintf(stderr, "home directory is /, not deleted!\n");
            return 12;
        }

        if (access(home_directory.characters(), F_OK) != -1) {
            auto child = fork();

            if (child < 0) {
                perror("fork");
                return 12;
            }

            if (!child) {
                int rc = execl("/bin/rm", "rm", "-r", home_directory.characters(), nullptr);
                ASSERT(rc < 0);
                perror("execl");
                exit(127);
            }

            int wstatus;
            if (waitpid(child, &wstatus, 0) < 0) {
                perror("waitpid");
                return 12;
            }
            if (WEXITSTATUS(wstatus)) {
                fprintf(stderr, "failed to remove the home directory\n");
                return 12;
            }
        }
    }

    return 0;
}