// KISSY (Kissing Interface for Sapphic Smooching over ttY) v1.2

/*
    Copyright (C) 2025  Magdalunaa <magdalunaa@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, either version 3 of the License, or
    (at your option) any later version.

    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 <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <string.h>
#include <pwd.h>
#include <stdbool.h>
#include <ctype.h>

// mreowww meow nya :3

int main (int argc, char **argv) {

    // print help
    if (argc < 2 || strcmp(argv[1], "--help") == 0 || strcmp(argv[1], "-h") == 0) {
        printf("%s\n", "Usage: kissy [target] <message>\n\n"
            "Kissy is a utility that allows you to kiss currently logged in users who allow messages.\n"
            "It works by writing to files in /dev/pts. It needs to run as the group who owns said files (usually tty), using setgid (2755 permissions).");
        return 0;
    }

    // are we running with setgid?
    struct stat stat_self;
    stat("/proc/self/exe", &stat_self);

    if (!(stat_self.st_mode & S_ISGID && !(stat_self.st_mode & S_IWOTH))) {
        printf("%s\n", "setgid is not set, or this file is world writable.");
        return 3;
    }

    // try to find the target's uid
    struct passwd *pw = getpwnam(argv[1]);
    if (pw == NULL) {
        printf("%s\n", "Cannot find target");
        return 1;
    }
    uid_t target = pw->pw_uid;

    // get current username
    struct passwd *pw2 = getpwuid(getuid());
    if (pw == NULL) {
        printf("%s\n", "Cannot find user");
        return 2;
    }
    char* user = pw2->pw_name;

    // if we have a second argument, set a custom kiss message
    char kiss[32] = "*mwah*";
    if (argc >= 3) {
        int len = strlen(argv[2]);
        int written_chars = 0;
        for (int i = 0; i < len; i++) {
            if (written_chars >= 31) {
                kiss[31] = '\0';
                break;
            };
            if (iscntrl(argv[2][i])) continue;
            kiss[i] = argv[2][i];
            written_chars++;
        }
    }
    
    bool kissed = false;
    // iterate over all files in directory
    DIR *dir = opendir("/dev/pts");
    while (1) {
        struct dirent *ent = readdir(dir);
        if (ent == NULL)
            break;
        
        char filepath[strlen("/dev/pts/") + strlen(ent->d_name) + 1];
        strcpy(filepath, "/dev/pts/");
        strcat(filepath, ent->d_name);

        struct stat stats;
        stat (filepath, &stats);

        // find all terminals with the correct user and that are group-writable
        if (stats.st_mode & S_IWGRP && stats.st_uid == target) {
            kissed = true;

            if (stats.st_gid != getegid()) { // are we running as the tty user?
                fprintf(stderr, "%s\n", "Mismatch between file owner group and current effective group. Make sure this program is running with setgid.");
            } else {
                FILE *tty = fopen(filepath, "a"); // write to terminal!
                fprintf(tty, "\a\n%s\n--%s\n", kiss, user);
                fclose(tty);
            }
        }
    }

    // print a message if a suitable terminal couldn't be found
    if (!kissed)
        fprintf(stderr, "%s\n", "Couldn't find any suitable terminals. User is not logged in or has not enabled messages.");    
}