/**************************************************************/
/*  tpax: a topological pax implementation                    */
/*  Copyright (C) 2020--2021  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"

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

static int tpax_archive_append_memory_data(
	int                             fdout,
	void *                          buf,
	ssize_t                         nbytes)
{
	ssize_t ret;
	char  * ch;

	for (ch=buf; nbytes; ch+=ret) {
		ret = write(fdout,ch,nbytes);

		while ((ret < 0) && (errno == EINTR))
			ret = write(fdout,ch,nbytes);

		if (ret < 0)
			return ret;

		nbytes -= ret;
	}

	return 0;
}

static int tpax_archive_append_pad(
	const struct tpax_driver_ctx *  dctx,
	int                             fdout,
	const struct stat *             st)
{
	int     ret;
	off_t   cpos;
	ssize_t nbytes;
	char    buf[512];

	nbytes  = st->st_size;
	nbytes += 0x1ff;
	nbytes |= 0x1ff;
	nbytes ^= 0x1ff;
	nbytes -= st->st_size;

	memset(buf,0,nbytes);

	cpos  = tpax_get_driver_cpos(dctx);
	cpos += st->st_size + nbytes;

	if (!(ret = tpax_archive_append_memory_data(fdout,buf,nbytes)))
		tpax_set_driver_cpos(dctx,cpos);

	return ret;
}

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,
	struct tpax_unit_ctx *          unit,
	int                             depth,
	int                             fd,
	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),
				unit);

	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),
				unit);

	*fkeep        = true;
	cdent         = dentbuf->cdent;

	cdent->fdat   = fd;
	cdent->depth  = depth;
	cdent->nsize  = needed;
	cdent->parent = parent;

	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<cap; )
		*dst++ = 0;

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

	return 0;
}

static int tpax_archive_append_one(
	const struct tpax_driver_ctx *  dctx,
	const struct tpax_unit_ctx *    uctx,
	const struct dirent *           dent,
	int                             fdat,
	const char *                    prefix,
	const struct tpax_dirent *      parent,
	const char *                    pdir)
{
	struct tpax_unit_ctx *          unit;
	struct tpax_ustar_header        uhdr;
	off_t                           hpos;
	off_t                           dpos;
	int                             fdout;
	int                             fdtmp;
	ssize_t                         nread;
	ssize_t                         nbytes;
	void *                          buf;
	size_t                          buflen;
	size_t                          cmplen;
	void *				membuf;
	size_t                          nlen;
	const char *			path;
	const char *                    src;
	char *                          dst;
	char				pbuf[1024];

	/* fake uctx for recursion items */
	unit = 0;

	if (dent && tpax_get_unit_ctx(
			dctx,fdat,dent->d_name,
			&unit) < 0)
		return TPAX_NESTED_ERROR(dctx);

	uctx = dent ? unit : uctx;

	/* prefixed path */
	if (!prefix && !parent && !pdir) {
		path = *uctx->path;

	} else {
		nlen  = strlen(*uctx->path);
		nlen += prefix ? strlen(prefix) + 1 : 0;
		nlen += parent ? strlen(parent->dirent.d_name) + 1 : 0;

		if (nlen >= sizeof(pbuf))
			return TPAX_BUFFER_ERROR(dctx);

		dst = pbuf;

		if (prefix) {
			src = prefix;

			for (; *src; )
				*dst++ = *src++;

			if (dst[-1] != '/')
				*dst++ = '/';
		}

		if (parent) {
			src = parent->dirent.d_name;

			for (; *src; )
				*dst++ = *src++;

			*dst++ = '/';
		}

		if (pdir) {
			src = pdir;

			for (; *src; )
				*dst++ = *src++;

			*dst++ = '/';
		}

		src = *uctx->path;

		for (; *src; )
			*dst++ = *src++;

		*dst = 0;
		path = pbuf;
	}

	/* record errors */
	tpax_driver_set_ectx(
		dctx,0,path);

	/* driver */
	fdout = tpax_driver_fdout(dctx);

	/* header and data offsets: todo pax and cpio */
	hpos = tpax_get_driver_cpos(dctx);
	dpos = hpos + sizeof(uhdr);

	/* header */
	if (tpax_init_ustar_header(
			dctx,path,uctx->st,
			*uctx->link,&uhdr) < 0)
		return tpax_archive_append_ret(
			TPAX_NESTED_ERROR(dctx),
			unit);

	/* buffer  */
	membuf = 0;
	fdtmp  = -1;

	/* associated data? */
	if S_ISREG(uctx->st->st_mode) {
		buf = tpax_get_driver_anon_map_addr(
			dctx,&buflen);

		if (buflen >= (cmplen = uctx->st->st_size))
			membuf = buf;

		/* snapshot */
		if (membuf) {
			if (tpax_file_create_memory_snapshot(
					dctx,fdat,*uctx->path,
					uctx->st,membuf) < 0)
				return tpax_archive_append_ret(
					TPAX_NESTED_ERROR(dctx),
					unit);
		} else {
			if ((fdtmp = tpax_file_create_tmpfs_snapshot(
					dctx,fdat,*uctx->path,
					uctx->st)) < 0)
				return tpax_archive_append_ret(
					TPAX_NESTED_ERROR(dctx),
					unit);

			if (lseek(fdtmp,0,SEEK_SET) < 0)
				return tpax_archive_append_ret(
					TPAX_SYSTEM_ERROR(dctx),
					unit);
		}
	}

	/* append header */
	if (tpax_archive_append_memory_data(fdout,&uhdr,ssizeof(uhdr)) < 0) {
		if (fdtmp >= 0)
			close(fdtmp);

		return tpax_archive_append_ret(
			TPAX_SYSTEM_ERROR(dctx),
			unit);
	}

	tpax_set_driver_cpos(dctx,dpos);

	/* all done? */
	if (!(S_ISREG(uctx->st->st_mode))) {
		tpax_archive_append_ret(0,unit);
		return 0;
	}

	/* append data from snapshot */
	if (fdtmp >= 0) {
		buf = tpax_get_driver_anon_map_addr(
			dctx,&buflen);

		for (nread=0; nread<uctx->st->st_size; ) {
			nbytes = read(fdtmp,buf,buflen);

			while ((nbytes < 0) && (errno == EINTR))
				nbytes = read(fdtmp,buf,buflen);

			if (nbytes < 0) {
				close(fdtmp);
				return tpax_archive_append_ret(
					TPAX_SYSTEM_ERROR(dctx),
					unit);

			} else if (nbytes == 0) {
				close(fdtmp);
				return tpax_archive_append_ret(
					TPAX_CUSTOM_ERROR(dctx,TPAX_ERR_FLOW_ERROR),
					unit);

			} else {
				nread += nbytes;
			}

			if (tpax_archive_append_memory_data(fdout,buf,nbytes) < 0) {
				close(fdtmp);
				return tpax_archive_append_ret(
					TPAX_SYSTEM_ERROR(dctx),
					unit);
			}
		}

		close(fdtmp);
	} else {
		if (tpax_archive_append_memory_data(
				fdout,membuf,
				uctx->st->st_size) < 0)
			return tpax_archive_append_ret(
				TPAX_SYSTEM_ERROR(dctx),
				unit);
	}

	return tpax_archive_append_ret(
		tpax_archive_append_pad(dctx,fdout,uctx->st),
		unit);
}

static int tpax_archive_append_dir(
	const struct tpax_driver_ctx *  dctx,
	const struct tpax_unit_ctx *    uctx,
	struct tpax_dirent *            dent,
	int                             fdat,
	int                             depth,
	const char *                    prefix,
	const struct tpax_dirent *      parent)
{
	int                             fd;
	bool                            fkeep;
	long                            nbytes;
	struct dirent *                 dirent;
	struct dirent *                 dirents;
	struct tpax_unit_ctx *          unit;
	struct stat                     st;
	uintptr_t                       addr;

	/* fake uctx for recursion items */
	unit = 0;

	if (dent && tpax_get_unit_ctx(
			dctx,dent->fdat,dent->dirent.d_name,
			&unit) < 0)
		return TPAX_NESTED_ERROR(dctx);

	uctx = dent ? unit : uctx;

	/* verify that recursion item is still a directory */
	if (unit && !S_ISDIR(unit->st->st_mode))
		return tpax_archive_append_ret(
			TPAX_CUSTOM_ERROR(dctx,TPAX_ERR_FLOW_ERROR),
			unit);

	/* append directory entry to archive */
	if (tpax_archive_append_one(
			dctx,uctx,0,
			tpax_driver_fdcwd(dctx),
			prefix,0,0) < 0)
		return tpax_archive_append_ret(
			TPAX_NESTED_ERROR(dctx),
			unit);

	/* 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,*uctx->path,O_RDONLY|O_DIRECTORY|O_CLOEXEC,0)) < 0)
		return tpax_archive_append_ret(
			TPAX_SYSTEM_ERROR(dctx),
			unit);

	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),
			unit);

	/* 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),
						unit);

				if (S_ISDIR(st.st_mode)) {
					dirent->d_type = DT_DIR;
				}
			}

			if (dirent->d_type == DT_DIR) {
				if (tpax_archive_append_queue_item(
						dctx,dirent,
						parent,unit,depth,
						fd,&fkeep) < 0)
					return tpax_archive_append_ret(
						TPAX_NESTED_ERROR(dctx),
						unit);
			} else {
				if (tpax_archive_append_one(
						dctx,0,dirent,fd,prefix,
						0,*uctx->path) < 0)
					return tpax_archive_append_ret(
						TPAX_NESTED_ERROR(dctx),
						unit);
			}
		}

		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),
					unit);

			dirent = dirents;
		}
	}

	/* all done */
	return tpax_archive_append_ret(
		fkeep ? 0 : close(fd),
		unit);
}

static int tpax_archive_append_impl(
	const struct tpax_driver_ctx *  dctx,
	const struct tpax_unit_ctx *    uctx,
	int                             depth,
	const char *                    prefix,
	struct tpax_dirent *            parent)
{
	if (S_ISDIR(uctx->st->st_mode))
		if (dctx->cctx->drvflags & TPAX_DRIVER_DIR_MEMBER_RECURSE)
			return tpax_archive_append_dir(
				dctx,uctx,0,
				tpax_driver_fdcwd(dctx),
				depth,prefix,parent);

	return tpax_archive_append_one(
			dctx,uctx,0,
			tpax_driver_fdcwd(dctx),
			prefix,0,0);
}

int tpax_archive_append(
	const struct tpax_driver_ctx *  dctx,
	const struct tpax_unit_ctx *    uctx,
	const char *                    prefix)
{
	struct tpax_dirent_buffer *     dentbuf;
	struct tpax_dirent *            cdent;
	struct tpax_dirent *            cnext;
	const struct tpax_dirent *      parent;
	uintptr_t                       addr;
	const char *                    rdir;
	const char *                    src;
	char *                          dst;
	char *                          cap;
	char *                          mark;
	int                             idx;
	const char *                    dirv[256];
	char                            pbuf[2048];

	/* normalized prefix */
	if (prefix && (prefix[0] == '.') && (!prefix[1]))
		prefix = 0;

	if (prefix && (prefix[0] == '.') && (prefix[1] == '/'))
		for (++prefix; *prefix=='/'; prefix++)
			(void)0;

	/* append explicit item */
	tpax_archive_append_impl(dctx,uctx,0,prefix,0);

	/* iterate through queued items */
	dentbuf = tpax_get_driver_dirents(dctx);
	cdent   = dentbuf ? dentbuf->dbuf : 0;

	if (cdent) {
		dst = pbuf;
		cap = &pbuf[sizeof(pbuf)];

		if (prefix && prefix[0]) {
			for (; *src && dst<cap; )
				*dst++ = *src++;

			if (dst == cap)
				return TPAX_BUFFER_ERROR(dctx);

			if (dst[-1] != '/')
				*dst++ = '/';
		}

		src = *uctx->path;

		for (; *src && dst<cap; )
			*dst++ = *src++;

		if (dst == cap)
			return TPAX_BUFFER_ERROR(dctx);

		if (dst[-1] != '/')
			*dst++ = '/';

		*dst = 0;
		mark = dst;
		rdir = pbuf;

		(void)mark;
	}

	for (; cdent; ) {
		switch (cdent->dirent.d_type) {
			case DT_DIR:
				if (tpax_archive_append_dir(
						dctx,0,cdent,cdent->fdat,
						cdent->depth,rdir,cdent) < 0)
					return TPAX_NESTED_ERROR(dctx);

				break;

			default:
				if (tpax_archive_append_one(
						dctx,0,&cdent->dirent,
						cdent->fdat,rdir,cdent,0) < 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;
		}

		if (cnext && (cnext->parent != cdent->parent)) {
			if (cnext->depth > 256)
				return TPAX_BUFFER_ERROR(dctx);

			for (parent=cnext->parent; parent; parent=parent->parent)
				dirv[parent->depth - 1] = parent->dirent.d_name;

			for (idx=0,dst=mark; idx<cnext->parent->depth; idx++) {
				src    = dirv[idx];

				for (; *src; )
					*dst++ = *src++;

				*dst++ = '/';
			}

			*--dst = 0;
		}

		cdent = cnext;
	}

	return 0;
}

int tpax_archive_seal(const struct tpax_driver_ctx * dctx)
{
	int     fdout;
	off_t   cpos;
	ssize_t nbytes;
	ssize_t nwritten;
	ssize_t blksize;
	char    buf[512];

	blksize = tpax_get_archive_block_size(dctx);
	cpos    = tpax_get_driver_cpos(dctx);

	if (cpos % 512)
		return TPAX_CUSTOM_ERROR(dctx,TPAX_ERR_FLOW_ERROR);

	fdout = tpax_driver_fdout(dctx);
	memset(buf,0,sizeof(buf));

	switch (cpos % blksize) {
		case 0:
			nbytes = cpos + blksize;
			break;

		default:
			nbytes  = cpos / blksize;
			nbytes *= blksize;
			nbytes += blksize;

			if (nbytes-cpos == 512)
				nbytes += blksize;
	}

	for (nwritten=cpos; nwritten<nbytes; nwritten+=512) {
		if (tpax_archive_append_memory_data(fdout,buf,512) < 0)
			return TPAX_SYSTEM_ERROR(dctx);

		tpax_set_driver_cpos(dctx,nwritten);
	}

	return 0;
}