/*
 * Copyright (c) 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Jef Poskanzer and Craig Leres of the Lawrence Berkeley Laboratory.
 *
 * 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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 *
 * @(#) Copyright (c) 1989, 1993 The Regents of the University of California.  All rights reserved.
 * @(#)write.c  8.1 (Berkeley) 6/6/93
 * $FreeBSD: src/usr.bin/write/write.c,v 1.12 1999/08/28 01:07:48 peter Exp $
 */

#include <sys/param.h>
#include <sys/stat.h>
#include <sys/file.h>

#include <ctype.h>
#include <err.h>
#include <locale.h>
#include <paths.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <time.h>
#include <unistd.h>
#include "utmpentry.h"

static void     done(int);
static void     do_write(const char *, const char *, uid_t, int *);
static void     usage(void);
static int      term_chk(const char *, int *, time_t *, int);
static void     wr_fputs(unsigned char *s);
static void     search_utmpx(const char *, char *, size_t, const char *, uid_t);
static int      utmpx_chk(const char *, const char *);

int
main(int argc, char **argv)
{
        time_t atime;
        uid_t myuid;
        int msgsok, mymsgok, myttyfd;
        char tty[MAXPATHLEN], *mytty;

        setlocale(LC_CTYPE, "");

        /* check that sender has write enabled */
        if (isatty(fileno(stdin)))
                myttyfd = fileno(stdin);
        else if (isatty(fileno(stdout)))
                myttyfd = fileno(stdout);
        else if (isatty(fileno(stderr)))
                myttyfd = fileno(stderr);
        else
                errx(1, "can't find your tty");
        if (!(mytty = ttyname(myttyfd)))
                errx(1, "can't find your tty's name");
        if (!strncmp(mytty, _PATH_DEV, strlen(_PATH_DEV)))
                mytty += strlen(_PATH_DEV);
        if (term_chk(mytty, &mymsgok, &atime, 1))
                exit(1);
        if (!mymsgok)
                warnx("you have write permission turned off (man mesg)");

        myuid = getuid();

        /* check args */
        switch (argc) {
        case 2:
                search_utmpx(argv[1], tty, sizeof tty, mytty, myuid);
                do_write(tty, mytty, myuid, &mymsgok);
                break;
        case 3:
                if (!strncmp(argv[2], _PATH_DEV, strlen(_PATH_DEV)))
                        argv[2] += strlen(_PATH_DEV);
                if (utmpx_chk(argv[1], argv[2]))
                        errx(1, "%s is not logged in on %s", argv[1], argv[2]);
                if (term_chk(argv[2], &msgsok, &atime, 1))
                        exit(1);
                if (myuid && !msgsok)
                        errx(1, "%s has messages disabled on %s", argv[1], argv[2]);
                do_write(argv[2], mytty, myuid, &mymsgok);
                break;
        default:
                usage();
        }
        done(0);
        return (0);
}

static void
usage(void)
{
        fprintf(stderr, "usage: write user [tty]\n");
        exit(1);
}

/*
 * utmpx_chk - checks that the given user is actually logged in on
 *     the given tty
 */
static int
utmpx_chk(const char *user, const char *tty)
{
        struct utmpentry *ep;

        getutentries(NULL, &ep);

        for (; ep; ep = ep->next) {
                if (strcmp(user, ep->name) == 0 &&
                    strcmp(tty, ep->line) == 0) {
                        return(0);
                }
        }

        return(1);
}

/*
 * search_utmpx - search utmpx for the "best" terminal to write to
 *
 * Ignores terminals with messages disabled, and of the rest, returns
 * the one with the most recent access time.  Returns as value the number
 * of the user's terminals with messages enabled, or -1 if the user is
 * not logged in at all.
 *
 * Special case for writing to yourself - ignore the terminal you're
 * writing from, unless that's the only terminal with messages enabled.
 */
static void
search_utmpx(const char *user, char *tty, size_t ttyl, const char *mytty, uid_t myuid)
{
        struct utmpentry *ep;
        time_t bestatime, atime;
        int nloggedttys, nttys, msgsok, user_is_me;

        getutentries(NULL, &ep);

        nloggedttys = nttys = 0;
        bestatime = 0;
        user_is_me = 0;
        for (; ep; ep = ep->next)
                if (strcmp(user, ep->name) == 0) {
                        ++nloggedttys;
                        if (term_chk(ep->line, &msgsok, &atime, 0))
                                continue;       /* bad term? skip */
                        if (myuid && !msgsok)
                                continue;       /* skip ttys with msgs off */
                        if (strcmp(ep->line, mytty) == 0) {
                                user_is_me = 1;
                                continue;       /* don't write to yourself */
                        }
                        ++nttys;
                        if (atime > bestatime) {
                                bestatime = atime;
                                strlcpy(tty, ep->line, ttyl);
                        }
                }

        if (nloggedttys == 0)
                errx(1, "%s is not logged in", user);
        if (nttys == 0) {
                if (user_is_me) {               /* ok, so write to yourself! */
                        strlcpy(tty, mytty, ttyl);
                        return;
                }
                errx(1, "%s has messages disabled", user);
        } else if (nttys > 1) {
                warnx("%s is logged in more than once; writing to %s", user, tty);
        }
}

/*
 * term_chk - check that a terminal exists, and get the message bit
 *     and the access time
 */
static int
term_chk(const char *tty, int *msgsokP, time_t *atimeP, int showerror)
{
        struct stat s;
        char path[MAXPATHLEN];

        snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
        if (stat(path, &s) < 0) {
                if (showerror)
                        warn("%s", path);
                return(1);
        }
        *msgsokP = (s.st_mode & S_IWGRP) != 0;  /* group write bit */
        *atimeP = s.st_atime;
        return(0);
}

/*
 * do_write - actually make the connection
 */
static void
do_write(const char *tty, const char *mytty, uid_t myuid, int *mymsgok)
{
        const char *login;
        char *nows;
        struct passwd *pwd;
        time_t now;
        char path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512];

        /* Determine our login name before we reopen() stdout */
        if ((login = getlogin()) == NULL) {
                if ((pwd = getpwuid(myuid)))
                        login = pwd->pw_name;
                else
                        login = "???";
        }

        snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
        if ((freopen(path, "w", stdout)) == NULL)
                err(1, "%s", path);

        signal(SIGINT, done);
        signal(SIGHUP, done);

        /* print greeting */
        if (gethostname(host, sizeof(host)) < 0)
                strlcpy(host, "???", sizeof host);
        now = time(NULL);
        nows = ctime(&now);
        nows[16] = '\0';
        printf("\r\n\007\007\007Message from %s@%s on %s at %s (%s %s replies)...\r\n",
            login, host, mytty, nows + 11, login, *mymsgok == 0 ? "does not accept" : "accepts");

        while (fgets(line, sizeof(line), stdin) != NULL)
                wr_fputs(line);
}

/*
 * done - cleanup and exit
 */
static void
done(__unused int n)
{
        printf("EOF\r\n");
        exit(0);
}

/*
 * wr_fputs - like fputs(), but makes control characters visible and
 *     turns \n into \r\n
 */
static void
wr_fputs(unsigned char *s)
{

#define PUTC(c) if (putchar(c) == EOF) err(1, NULL);

        for (; *s != '\0'; ++s) {
                if (*s == '\n') {
                        PUTC('\r');
                } else if (((*s & 0x80) && *s < 0xA0) ||
                           /* disable upper controls */
                           (!isprint(*s) && !isspace(*s) &&
                            *s != '\a' && *s != '\b')
                          ) {
                        if (*s & 0x80) {
                                *s &= ~0x80;
                                PUTC('M');
                                PUTC('-');
                        }
                        if (iscntrl(*s)) {
                                *s ^= 0x40;
                                PUTC('^');
                        }
                }
                PUTC(*s);
        }
        return;
#undef PUTC
}