/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2023 Klara, Inc.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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/stat.h>
#include <sys/wait.h>

#include <err.h>
#include <fcntl.h>
#include <paths.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#define PROGNAME        "mktar"

#define SUBDIRNAME      "directory"
#define NORMALFILENAME  "file"
#define SPARSEFILENAME  "sparse_file"
#define HARDLINKNAME    "hard_link"
#define SHORTLINKNAME   "short_link"
#define LONGLINKNAME    "long_link"

static bool opt_g;
static bool opt_v;

static void verbose(const char *fmt, ...)
{
        va_list ap;

        if (!opt_v)
                return;
        fprintf(stderr, "%s: ", PROGNAME);
        va_start(ap, fmt);
        vfprintf(stderr, fmt, ap);
        va_end(ap);
        fprintf(stderr, "\n");
}

static void
mknormalfile(const char *filename, mode_t mode)
{
        char buf[512];
        ssize_t res;
        int fd;

        if ((fd = open(filename, O_RDWR|O_CREAT|O_EXCL, mode)) < 0)
                err(1, "%s", filename);
        for (unsigned int i = 0; i < sizeof(buf); i++)
                buf[i] = 32 + i % 64;
        res = write(fd, buf, sizeof(buf));
        if (res < 0)
                err(1, "%s", filename);
        if (res != sizeof(buf))
                errx(1, "%s: short write", filename);
        close(fd);
}

static void
mksparsefile(const char *filename, mode_t mode)
{
        char buf[511];
        ssize_t res;
        int fd;

        if ((fd = open(filename, O_RDWR|O_CREAT|O_EXCL, mode)) < 0)
                err(1, "%s", filename);
        for (unsigned int i = 33; i <= 126; i++) {
                memset(buf, i, sizeof(buf));
                if (lseek(fd, 1048576LU * (i - 32), SEEK_SET) < 0)
                        err(1, "%s", filename);
                res = write(fd, buf, sizeof(buf));
                if (res < 0)
                        err(1, "%s", filename);
                if (res != sizeof(buf))
                        errx(1, "%s: short write", filename);
        }
        close(fd);
}

static char *
mklonglinktarget(const char *dirname, const char *filename)
{
        char *piece, *target;

        if (asprintf(&piece, "%1$s/../%1$s/../%1$s/../%1$s/../", dirname) < 0)
                err(1, "asprintf()");
        if (asprintf(&target, "%1$s%1$s%1$s%1$s%1$s%1$s%1$s%1$s%2$s", piece, filename) < 0)
                err(1, "asprintf()");
        free(piece);
        return target;
}

static void
mktar(void)
{
        char *linktarget;

        /* create a subdirectory */
        verbose("mkdir %s", SUBDIRNAME);
        if (mkdir(SUBDIRNAME, 0755) != 0)
                err(1, "%s", SUBDIRNAME);

        /* create a normal file */
        verbose("creating %s", NORMALFILENAME);
        mknormalfile(NORMALFILENAME, 0644);

        /* create a sparse file */
        verbose("creating %s", SPARSEFILENAME);
        mksparsefile(SPARSEFILENAME, 0644);
        chflags(SPARSEFILENAME, UF_NODUMP);

        /* create a hard link */
        verbose("link %s %s", SPARSEFILENAME, HARDLINKNAME);
        if (link(SPARSEFILENAME, HARDLINKNAME) != 0)
                err(1, "%s", HARDLINKNAME);

        /* create a symbolic link with a short target */
        verbose("symlink %s %s", SPARSEFILENAME, SHORTLINKNAME);
        if (symlink(SPARSEFILENAME, SHORTLINKNAME) != 0)
                err(1, "%s", SHORTLINKNAME);

        /* create a symbolic link with a long target */
        linktarget = mklonglinktarget(SUBDIRNAME, SPARSEFILENAME);
        verbose("symlink %s %s", linktarget, LONGLINKNAME);
        if (symlink(linktarget, LONGLINKNAME) != 0)
                err(1, "%s", LONGLINKNAME);
        free(linktarget);
}

static void
usage(void)
{

        fprintf(stderr, "usage: %s [-gv] tarfile\n", PROGNAME);
        exit(EXIT_FAILURE);
}

int
main(int argc, char *argv[])
{
        const char *tarfilename;
        char *dirname;
        int opt, wstatus;
        pid_t pid;

        while ((opt = getopt(argc, argv, "gv")) != -1)
                switch (opt) {
                case 'g':
                        opt_g = true;
                        break;
                case 'v':
                        opt_v = true;
                        break;
                default:
                        usage();
                }

        argc -= optind;
        argv += optind;

        if (argc != 1)
                usage();
        tarfilename = *argv;

        if (asprintf(&dirname, "%s%s.XXXXXXXX", _PATH_TMP, PROGNAME) < 0)
                err(1, "asprintf()");
        if (mkdtemp(dirname) == NULL)
                err(1, "%s", dirname);
        verbose("mkdir %s", dirname);

        /* fork a child to create the files */
        if ((pid = fork()) < 0)
                err(1, "fork()");
        if (pid == 0) {
                verbose("cd %s", dirname);
                if (chdir(dirname) != 0)
                        err(1, "%s", dirname);
                verbose("umask 022");
                umask(022);
                mktar();
                verbose("cd -");
                exit(0);
        }
        if (waitpid(pid, &wstatus, 0) < 0)
                err(1, "waitpid()");
        if (!WIFEXITED(wstatus) || WEXITSTATUS(wstatus) != 0)
                errx(1, "child failed");

        /* fork a child to create the tarball */
        if ((pid = fork()) < 0)
                err(1, "fork()");
        if (pid == 0) {
                verbose("creating tarball");
                execlp(opt_g ? "gtar" : "tar",
                    "tar",
                    "-c",
                    "-f", tarfilename,
                    "-C", dirname,
                    "--posix",
                    "--zstd",
#if 0
                    "--options", "zstd:frame-per-file",
#endif
                    "./" SUBDIRNAME "/../" NORMALFILENAME,
                    "./" SPARSEFILENAME,
                    "./" HARDLINKNAME,
                    "./" SHORTLINKNAME,
                    "./" SUBDIRNAME,
                    "./" LONGLINKNAME,
                    NULL);
                err(1, "execlp()");
        }
        if (waitpid(pid, &wstatus, 0) < 0)
                err(1, "waitpid()");
        if (!WIFEXITED(wstatus) || WEXITSTATUS(wstatus) != 0)
                errx(1, "child failed");

        /* fork a child to delete everything */
        if ((pid = fork()) < 0)
                err(1, "fork()");
        if (pid == 0) {
                verbose("cd %s", dirname);
                if (chdir(dirname) != 0)
                        err(1, "%s", dirname);
                verbose("rm %s", LONGLINKNAME);
                (void)unlink(LONGLINKNAME);
                verbose("rm %s", SHORTLINKNAME);
                (void)unlink(SHORTLINKNAME);
                verbose("rm %s", HARDLINKNAME);
                (void)unlink(HARDLINKNAME);
                verbose("rm %s", SPARSEFILENAME);
                (void)unlink(SPARSEFILENAME);
                verbose("rmdir %s", SUBDIRNAME);
                (void)rmdir(SUBDIRNAME);
                verbose("cd -");
                exit(0);
        }
        if (waitpid(pid, &wstatus, 0) < 0)
                err(1, "waitpid()");
        if (!WIFEXITED(wstatus) || WEXITSTATUS(wstatus) != 0)
                errx(1, "child failed");
        verbose("rmdir %s", dirname);
        (void)rmdir(dirname);

        exit(0);
}