/**************************************************************/

/*  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/mman.h>

#include <sys/stat.h>

#include <tpax/tpax.h>

#include <tpax/tpax_specs.h>

#include "tpax_driver_impl.h"

#include "tpax_getdents_impl.h"

#include "tpax_tmpfile_impl.h"

#include "tpax_errinfo_impl.h"

static char * tpax_append_prefix_item(

	const struct tpax_driver_ctx *  dctx,

	const char *                    prefix)

{

	struct tpax_driver_ctx_impl *   ictx;

	char **                         prefv;

	char **                         psrc;

	char **                         pdst;

	off_t                           elements;

	char *                          pitem;

	ictx = tpax_get_driver_ictx(dctx);

	for (psrc=ictx->prefixv; *psrc; psrc++)

		if (!strcmp(*psrc,prefix))

			return *psrc;

	if (ictx->prefixp == ictx->prefcap) {

		elements  = ictx->prefcap - ictx->prefixv;

		elements += 256;

		if (!(prefv = calloc(elements,sizeof(char *))))

			return 0;

		for (psrc=ictx->prefixv,pdst=prefv; *psrc; psrc++,pdst++)

			*pdst = *psrc;

		if (ictx->prefixv != ictx->prefptr)

			free(ictx->prefixv);

		ictx->prefixv = prefv;

		ictx->prefixp = pdst;

		ictx->prefcap = &prefv[--elements];

	}

	if (!(pitem = strdup(prefix)))

		return 0;

	*ictx->prefixp++ = pitem;

	return pitem;

}

static char * tpax_append_prefix_item_from_path(

	const struct tpax_driver_ctx *  dctx,

	const char *                    path,

	const char *                    mark)

{

	off_t   nbytes;

	char    pathbuf[PATH_MAX];

	if ((nbytes = (mark - path)) >= (PATH_MAX - 1))

		return 0;

	memcpy(pathbuf,path,nbytes);

	pathbuf[nbytes++] = '/';

	pathbuf[nbytes]   = '\0';

	return tpax_append_prefix_item(dctx,pathbuf);

}

static struct tpax_dirent_buffer * tpax_dirent_buf_first_alloc(

	const struct tpax_driver_ctx * dctx)

{

	void * addr;

	struct tpax_driver_ctx_impl * ictx;

	addr = (struct tpax_dirent_buffer *)mmap(

		0,TPAX_DIRENT_BUFLEN,

		PROT_READ|PROT_WRITE,

		MAP_PRIVATE|MAP_ANONYMOUS,

		-1,0);

	if (addr == MAP_FAILED)

		return 0;

	ictx                  = tpax_get_driver_ictx(dctx);

	ictx->dirents         = (struct tpax_dirent_buffer *)addr;

	ictx->dirents->cdent  = ictx->dirents->dbuf;

	ictx->dirents->size   = TPAX_DIRENT_BUFLEN;

	ictx->dirents->next   = 0;

	ictx->dirents->nfree  = TPAX_DIRENT_BUFLEN;

	ictx->dirents->nfree -= offsetof(struct tpax_dirent_buffer,dbuf);

	return ictx->dirents;

}

static struct tpax_dirent_buffer * tpax_dirent_buf_next_alloc(

	struct tpax_dirent_buffer * current)

{

	void * addr;

	addr = (struct tpax_dirent_buffer *)mmap(

		0,TPAX_DIRENT_BUFLEN,

		PROT_READ|PROT_WRITE,

		MAP_PRIVATE|MAP_ANONYMOUS,

		-1,0);

	if (addr == MAP_FAILED)

		return 0;

	current->next         = (struct tpax_dirent_buffer *)addr;

	current->next->cdent  = current->next->dbuf;

	current->next->size   = TPAX_DIRENT_BUFLEN;

	current->next->next   = 0;

	current->next->nfree  = TPAX_DIRENT_BUFLEN;

	current->next->nfree -= offsetof(struct tpax_dirent_buffer,dbuf);

	return current->next;

}

static int tpax_archive_append_ret(

	int                     ret,

	struct tpax_unit_ctx *  unit)

{

	if (unit)

		tpax_free_unit_ctx(unit);

	return ret;

}

static int tpax_archive_append_queue_item(

	const struct tpax_driver_ctx *  dctx,

	const struct dirent *           dirent,

	const struct tpax_dirent *      parent,

	const char *                    prefix,

	int                             depth,

	int                             flags,

	int                             fdat,

	bool *                          fkeep)

{

	struct tpax_dirent_buffer *     dentbuf;

	struct tpax_dirent *            cdent;

	const char *                    src;

	char *                          dst;

	char *                          cap;

	size_t                          needed;

	if (!(dentbuf = tpax_get_driver_dirents(dctx)))

		if (!(dentbuf = tpax_dirent_buf_first_alloc(dctx)))

			return tpax_archive_append_ret(

				TPAX_SYSTEM_ERROR(dctx),

				0);

	needed  = dirent->d_reclen;

	needed += offsetof(struct tpax_dirent,dirent);

	needed += 0x7;

	needed |= 0x7;

	needed ^= 0x7;

	for (; dentbuf->next && (dentbuf->nfree < needed); )

		dentbuf = dentbuf->next;

	if (dentbuf->nfree < needed)

		if (!(dentbuf = tpax_dirent_buf_next_alloc(dentbuf)))

			return tpax_archive_append_ret(

				TPAX_SYSTEM_ERROR(dctx),

				0);

	*fkeep        = true;

	cdent         = dentbuf->cdent;

	cdent->fdat   = fdat;

	cdent->depth  = depth;

	cdent->flags  = flags;

	cdent->nsize  = needed;

	cdent->parent = parent;

	cdent->prefix = prefix;

	memset(&cdent->dirent,0,offsetof(struct dirent,d_name));

	cdent->dirent.d_ino    = dirent->d_ino;

	cdent->dirent.d_type   = dirent->d_type;

	cdent->dirent.d_reclen = dirent->d_reclen;

	src  = dirent->d_name;

	dst  = cdent->dirent.d_name;

	cap  = dst - offsetof(struct dirent,d_name);

	cap -= offsetof(struct tpax_dirent,dirent);

	cap += needed;

	for (; *src; )

		*dst++ = *src++;

	for (; dst

		*dst++ = 0;

	dentbuf->cdent  = (struct tpax_dirent *)cap;

	dentbuf->nfree -= needed;

	tpax_set_driver_dirmark(dctx,cdent);

	return 0;

}

static int tpax_archive_append_dir_entries(

	const struct tpax_driver_ctx *  dctx,

	struct tpax_dirent *            dent)

{

	int                             fd;

	int                             fdat;

	int                             depth;

	bool                            fkeep;

	long                            nbytes;

	struct dirent *                 dirent;

	struct dirent *                 dirents;

	struct tpax_unit_ctx *          uctx;

	struct stat                     st;

	uintptr_t                       addr;

	/* init */

	fdat  = dent->fdat;

	depth = dent->depth;

	/* uctx on the fly */

	if (tpax_get_unit_ctx(

			dctx,fdat,

			dent->dirent.d_name,

			&uctx) < 0)

		return TPAX_NESTED_ERROR(dctx);

	/* verify that recursion item is still a directory */

	if (!S_ISDIR(uctx->st->st_mode))

		return tpax_archive_append_ret(

			TPAX_CUSTOM_ERROR(dctx,TPAX_ERR_FLOW_ERROR),

			uctx);

	/* obtain buffer for file-system directory entries */

	dirents = tpax_get_driver_getdents_buffer(dctx);

	dirent  = dirents;

	fkeep   = false;

	nbytes  = 0;

	depth++;

	/* open directory and obtain first directory entries */

	if ((fd = openat(fdat,dent->dirent.d_name,O_RDONLY|O_DIRECTORY|O_CLOEXEC,0)) < 0)

		return tpax_archive_append_ret(

			TPAX_SYSTEM_ERROR(dctx),

			uctx);

	nbytes = tpax_getdents(fd,dirents,TPAX_DIRENT_BUFLEN);

	while ((nbytes == -EINTR) || ((nbytes < 0) && (errno == EINTR)))

		nbytes = tpax_getdents(fd,dirents,TPAX_DIRENT_BUFLEN);

	if (nbytes < 0)

		return tpax_archive_append_ret(

			TPAX_SYSTEM_ERROR(dctx),

			uctx);

	/* iterate */

	for (; nbytes>0; ) {

		if (!strcmp(dirent->d_name,".")) {

			(void)0;

		} else if (!strcmp(dirent->d_name,"..")) {

			(void)0;

		} else {

			if (dirent->d_type == DT_UNKNOWN) {

				if (fstatat(fd,dirent->d_name,&st,AT_SYMLINK_NOFOLLOW))

					return tpax_archive_append_ret(

						TPAX_SYSTEM_ERROR(dctx),

						uctx);

				if (S_ISDIR(st.st_mode)) {

					dirent->d_type = DT_DIR;

				}

			}

			if (tpax_archive_append_queue_item(

					dctx,dirent,

					dent,0,depth,

					TPAX_ITEM_IMPLICIT,

					fd,&fkeep) < 0)

				return tpax_archive_append_ret(

					TPAX_NESTED_ERROR(dctx),

					uctx);

		}

		addr    = (uintptr_t)dirent;

		addr   += dirent->d_reclen;

		nbytes -= dirent->d_reclen;

		dirent  = (struct dirent *)addr;

		if (nbytes == 0) {

			nbytes = tpax_getdents(fd,dirents,TPAX_DIRENT_BUFLEN);

			while ((nbytes == -EINTR) || ((nbytes < 0) && (errno == EINTR)))

				nbytes = tpax_getdents(fd,dirents,TPAX_DIRENT_BUFLEN);

			if (nbytes < 0)

				tpax_archive_append_ret(

					TPAX_SYSTEM_ERROR(dctx),

					uctx);

			dirent = dirents;

		}

	}

	/* all done */

	return tpax_archive_append_ret(

		fkeep ? 0 : close(fd),

		uctx);

}

static const char * tpax_path_prefix_mark(const char * path)

{

	const char *    src;

	char *          mark;

	char            pathbuf[PATH_MAX];

	src  = path;

	mark = pathbuf;

	for (; *src; )

		*mark++ = *src++;

	for (--mark; (*mark == '/'); mark--)

		(void)0;

	*++mark = '\0';

	for (; (mark > pathbuf) && (mark[-1] != '/'); )

		mark--;

	return (mark <= pathbuf) ? 0 : &path[--mark-pathbuf];

}

static int tpax_dirent_init_from_uctx(

	const struct stat * st,

	const char *        basename,

	struct dirent *     dirent)

{

	/* st_mode to d_type translation */

	if (S_ISREG(st->st_mode))

		dirent->d_type = DT_REG;

	else if (S_ISLNK(st->st_mode))

		dirent->d_type = DT_LNK;

	else if (S_ISDIR(st->st_mode))

		dirent->d_type = DT_DIR;

	else if (S_ISCHR(st->st_mode))

		dirent->d_type = DT_CHR;

	else if (S_ISBLK(st->st_mode))

		dirent->d_type = DT_CHR;

	else if (S_ISFIFO(st->st_mode))

		dirent->d_type = DT_CHR;

	else

		return -1;

	/* d_off, d_ino */

	dirent->d_off    = 0;

	dirent->d_ino    = st->st_ino;

	/* d_reclen */

	dirent->d_reclen  = offsetof(struct dirent,d_name);

	dirent->d_reclen += strlen(basename);

	dirent->d_reclen += 0x1;

	dirent->d_reclen |= 0x1;

	dirent->d_reclen ^= 0x1;

	/* d_name */

	strcpy(dirent->d_name,basename);

	return 0;

}

int tpax_archive_append_item(

	const struct tpax_driver_ctx *  dctx,

	const struct tpax_unit_ctx *    uctx)

{

	int                             fdat;

	uintptr_t                       addr;

	const char *                    name;

	const char *                    mark;

	const char *                    prefix;

	bool                            fkeep;

	struct tpax_dirent_buffer *     dentbuf;

	struct tpax_dirent *            cdent;

	struct tpax_dirent *            cnext;

	struct dirent *                 dirent;

	char                            entbuf[PATH_MAX + sizeof(struct dirent)];

	/* init */

	fdat   = tpax_driver_fdcwd(dctx);

	dirent = (struct dirent *)entbuf;

	prefix = 0;

	/* split path to prefix + basename */

	if ((mark = tpax_path_prefix_mark(*uctx->path)))

		if (!(prefix = tpax_append_prefix_item_from_path(

				dctx,*uctx->path,mark)))

			return tpax_archive_append_ret(

				TPAX_BUFFER_ERROR(dctx),

				0);

	name = mark ? ++mark : *uctx->path;

	if (prefix)

		if ((fdat = openat(fdat,prefix,O_RDONLY|O_DIRECTORY|O_CLOEXEC,0)) < 0)

			return tpax_archive_append_ret(

				TPAX_SYSTEM_ERROR(dctx),

				0);

	/* explicit item directory entry */

	if (tpax_dirent_init_from_uctx(uctx->st,name,dirent) < 0)

			return tpax_archive_append_ret(

				TPAX_CUSTOM_ERROR(

					dctx,

					TPAX_ERR_FLOW_ERROR),

				0);

	/* add to queue */

	if (tpax_archive_append_queue_item(

			dctx,dirent,0,prefix,0,

			TPAX_ITEM_EXPLICIT,

			fdat,&fkeep) < 0)

		return tpax_archive_append_ret(

			TPAX_NESTED_ERROR(dctx),

			0);

	/* queue directory child items */

	dentbuf = tpax_get_driver_dirents(dctx);

	cdent   = tpax_get_driver_dirmark(dctx);

	for (; cdent; ) {

		if (cdent->dirent.d_type == DT_DIR)

			if (tpax_archive_append_dir_entries(dctx,cdent) < 0)

				return TPAX_NESTED_ERROR(dctx);

		addr  = (uintptr_t)cdent;

		addr += cdent->nsize;

		cnext = (struct tpax_dirent *)addr;

		if (cnext == dentbuf->cdent) {

			dentbuf = dentbuf->next;

			cnext   = dentbuf ? dentbuf->dbuf : 0;

		}

		cdent = cnext;

	}

	return 0;

}