/* KISSY (KISSY Interface for Sapphic Smooching over ttY) v1.0 by Magdalunaa

This file needs to:
- be owned by the tty group (or whatever group owns the terminal devices in your system)
- have setgid set
- be group executable
- not be world writeable

You can probably just use 2755 permissions. those work

*/

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

// mreowww meow nya :3

int main (int argc, char **argv) {
    // 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 writeable.");
        return 3;
    }

    // check we have at least one argument
    if (argc < 2) {
        printf("%s\n", "Not enough arguments!\nUsage: kissy [target] <message>");
        return 0;
    }

    // try to find the target's uid
    struct passwd *pw = getpwnam(argv[1]);
    if (pw == NULL) {
        printf("%s\n", "Cannot find target");
        return 1;
    }
    int 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;
    if (argc >= 3)
        kiss = argv[2];
    else
        kiss = "*mwah*";

    short kissed = 0;
    // 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 = 1;

            if (stats.st_gid != getegid()) { // are we running as the tty user?
                printf("%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, "\n%s\n--%s\n", kiss, user);
                fclose(tty);
            }
        }
    }

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