/**************************************************************/
/*  tpax: a topological pax implementation                    */
/*  Copyright (C) 2020--2024  SysDeer Technologies, LLC       */
/*  Released under GPLv2 and GPLv3; see COPYING.TPAX.         */
/**************************************************************/

#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <grp.h>
#include <pwd.h>
#include <sys/stat.h>

#include <tpax/tpax.h>
#include <tpax/tpax_specs.h>
#include "tpax_driver_impl.h"

#ifndef ssizeof
#define ssizeof(x) (ssize_t)(sizeof(x))
#endif

#define TPAX_CPIO_PERM_MASK         \
	( S_ISUID | S_ISGID          \
	| S_IRUSR | S_IWUSR | S_IXUSR \
	| S_IRGRP | S_IWGRP | S_IXGRP \
	| S_IROTH | S_IWOTH | S_IXOTH )

static void tpax_octal_write(char * ch, ssize_t len, uint64_t val)
{
	for (; len; ) {
		ch[--len] = val % 8 + '0';
		val /= 8;
	}
}

int tpax_meta_init_cpio_header(
	const char *                    path,
	const struct stat *             st,
	const char *                    linkname,
	int                             cdev,
	int                             cino,
	int                             cnlink,
	struct tpax_cpio_header *       chdr)
{
	size_t		fnsize;
	size_t		lnklen;
	size_t		stsize;
	int64_t		stmtim;
	uint32_t	typeflag;
	uint32_t	permbits;
	uint32_t	modebits;

	/* filename size */
	fnsize = strlen(path) + 1;

	/* size & mtime validation */
	stsize = S_ISREG(st->st_mode) ? st->st_size : 0;
	stmtim = st->st_mtim.tv_sec;

	if (stsize > 077777777777)
		return -1;

	if ((stmtim < 0) || (stmtim > 077777777777))
		return -1;

	/* linkname validation */
	if (S_ISLNK(st->st_mode) && !linkname)
		return -1;

	lnklen = S_ISLNK(st->st_mode)
		? strlen(linkname)
		: 0;

	/* typeflag validation */
	if (S_ISREG(st->st_mode))
		typeflag = TPAX_CPIO_FILEMODE_ISREG;
	else if (S_ISLNK(st->st_mode))
		typeflag = TPAX_CPIO_FILEMODE_ISLNK;
	else if (S_ISDIR(st->st_mode))
		typeflag = TPAX_CPIO_FILEMODE_ISDIR;
	else if (S_ISCHR(st->st_mode))
		typeflag = TPAX_CPIO_FILEMODE_ISCHR;
	else if (S_ISBLK(st->st_mode))
		typeflag = TPAX_CPIO_FILEMODE_ISBLK;
	else if (S_ISFIFO(st->st_mode))
		typeflag = TPAX_CPIO_FILEMODE_ISFIFO;
	else if (S_ISSOCK(st->st_mode))
		typeflag = TPAX_CPIO_FILEMODE_ISSOCK;
	else
		return -1;

	/* permbits, modeflag */
	permbits = st->st_mode & TPAX_CPIO_PERM_MASK;
	modebits = permbits | typeflag;

	/* one shot */
	memset(chdr,0,sizeof(*chdr));

	/* c_magic */
	chdr->c_magic[0] = '0';
	chdr->c_magic[1] = '7';
	chdr->c_magic[2] = '0';
	chdr->c_magic[3] = '7';
	chdr->c_magic[4] = '0';
	chdr->c_magic[5] = '7';

	/* c_dev, c_ino */
	tpax_octal_write(chdr->c_dev,ssizeof(chdr->c_dev),cdev);
	tpax_octal_write(chdr->c_ino,ssizeof(chdr->c_ino),cino);

	/* c_mode */
	tpax_octal_write(chdr->c_mode,ssizeof(chdr->c_mode),modebits);

	/* c_uid, c_gid */
	if ((uint64_t)st->st_uid <= 0777777)
		tpax_octal_write(chdr->c_uid,ssizeof(chdr->c_uid),st->st_uid);
	else
		tpax_octal_write(chdr->c_uid,ssizeof(chdr->c_uid),0);

	if ((uint64_t)st->st_gid <= 0777777)
		tpax_octal_write(chdr->c_gid,ssizeof(chdr->c_gid),st->st_gid);
	else
		tpax_octal_write(chdr->c_gid,ssizeof(chdr->c_gid),0);

	/* c_nlink */
	tpax_octal_write(chdr->c_nlink,ssizeof(chdr->c_nlink),cnlink);

	/* c_rdev */
	tpax_octal_write(chdr->c_rdev,ssizeof(chdr->c_rdev),st->st_rdev);

	/* c_mtime */
	tpax_octal_write(chdr->c_mtime,ssizeof(chdr->c_mtime),stmtim);

	/* c_namesize */
	tpax_octal_write(chdr->c_namesize,ssizeof(chdr->c_namesize),fnsize);

	/* c_filesize */
	tpax_octal_write(chdr->c_filesize,ssizeof(chdr->c_filesize),lnklen ? lnklen : stsize);

	/* all done; c_name to be written along with c_filedata */
	return 0;
}