/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1980, 1988, 1993
 *      The Regents of the University of California.  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.
 * 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.
 */

#include <sys/types.h>

#include <capsicum_helpers.h>
#include <ctype.h>
#include <err.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <paths.h>
#include <string.h>
#include <unistd.h>

static int match(const char *, const char *);
static void usage(void) __dead2;

int
main(int argc, char **argv)
{
        FILE *mbox;
        struct passwd *pwd;
        int ch, count, newline;
        const char *file;
        char *sender, *p;
#if MAXPATHLEN > BUFSIZ
        char buf[MAXPATHLEN];
#else
        char buf[BUFSIZ];
#endif

        file = sender = NULL;
        count = -1;
        while ((ch = getopt(argc, argv, "cf:s:")) != -1)
                switch (ch) {
                case 'c':
                        count = 0;
                        break;
                case 'f':
                        file = optarg;
                        break;
                case 's':
                        sender = optarg;
                        for (p = sender; *p; ++p)
                                *p = tolower(*p);
                        break;
                case '?':
                default:
                        usage();
                }
        argc -= optind;
        argv += optind;

        if (file == NULL) {
                if (argc) {
                        (void)snprintf(buf, sizeof(buf), "%s/%s", _PATH_MAILDIR, *argv);
                        file  = buf;
                } else {
                        if (!(file = getenv("MAIL"))) {
                                if (!(pwd = getpwuid(getuid())))
                                        errx(1, "no password file entry for you");
                                file = pwd->pw_name;
                                (void)snprintf(buf, sizeof(buf),
                                    "%s/%s", _PATH_MAILDIR, file);
                                file = buf;
                        }
                }
        }

        /* read from stdin */
        if (strcmp(file, "-") == 0) {
                mbox = stdin;
        }
        else if ((mbox = fopen(file, "r")) == NULL) {
                errx(EXIT_FAILURE, "can't read %s", file);
        }
        if (caph_limit_stdio() < 0 || caph_enter() < 0) {
                err(EXIT_FAILURE, "capsicum");
        }
        for (newline = 1; fgets(buf, sizeof(buf), mbox);) {
                if (*buf == '\n') {
                        newline = 1;
                        continue;
                }
                if (newline && !strncmp(buf, "From ", 5) &&
                    (!sender || match(buf + 5, sender))) {
                        if (count != -1)
                                count++;
                        else
                                printf("%s", buf);
                }
                newline = 0;
        }
        if (count != -1)
                printf("There %s %d message%s in your incoming mailbox.\n",
                    count == 1 ? "is" : "are", count, count == 1 ? "" : "s");
        fclose(mbox);
        exit(EXIT_SUCCESS);
}

static void
usage(void)
{
        fprintf(stderr, "usage: from [-c] [-f file] [-s sender] [user]\n");
        exit(EXIT_FAILURE);
}

static int
match(const char *line, const char *sender)
{
        char ch, pch, first;
        const char *p, *t;

        for (first = *sender++;;) {
                if (isspace(ch = *line))
                        return (0);
                ++line;
                ch = tolower(ch);
                if (ch != first)
                        continue;
                for (p = sender, t = line;;) {
                        if (!(pch = *p++))
                                return (1);
                        ch = tolower(*t);
                        t++;
                        if (ch != pch)
                                break;
                }
        }
        /* NOTREACHED */
}