/*
 * Copyright (c) 2018 Gilles Chehade <gilles@poolp.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/types.h>

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysexits.h>
#include <time.h>
#include <unistd.h>

static void     mboxfile_engine(const char *sender, const char *filename);

int
main(int argc, char *argv[])
{
        int     ch;
        char   *sender = "<unknown>";

        if (! geteuid())
                errx(1, "mail.mboxfile: may not be executed as root");

        while ((ch = getopt(argc, argv, "f:")) != -1) {
                switch (ch) {
                case 'f':
                        sender = optarg;
                        break;
                default:
                        break;
                }
        }
        argc -= optind;
        argv += optind;

        if (argc > 1)
                errx(1, "mail.mboxfile: only one mboxfile is allowed");

        mboxfile_engine(sender, argv[0]);

        return (0);
}

static void
mboxfile_engine(const char *sender, const char *filename)
{
        int     fd;
        FILE    *fp;
        char    *line = NULL;
        size_t  linesize = 0;
        time_t  now;

        time(&now);

        fd = open(filename, O_CREAT | O_APPEND | O_WRONLY | O_EXLOCK, 0600);
        if (fd == -1)
                err(EX_TEMPFAIL, NULL);

        if ((fp = fdopen(fd, "w")) == NULL)
                err(EX_TEMPFAIL, NULL);

        fprintf(fp, "From %s %s", sender, ctime(&now));
        while (getline(&line, &linesize, stdin) != -1) {
                line[strcspn(line, "\n")] = '\0';
                if (strncmp(line, "From ", 5) == 0)
                        fprintf(fp, ">%s\n", line);
                else
                        fprintf(fp, "%s\n", line);
        }
        fprintf(fp, "\n");
        free(line);
        if (ferror(stdin))
                err(EX_TEMPFAIL, NULL);

        if (fflush(fp) == EOF ||
            ferror(fp) ||
            (fsync(fd) == -1 && errno != EINVAL) ||
            fclose(fp) == EOF)
                err(EX_TEMPFAIL, NULL);
}