/*

 * Copyright (C) 2012, 2014  J. Ali Harlow <ali@juiblex.co.uk>

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation; either version 2 of the License, or

 * (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License along

 * with this program; if not, write to the Free Software Foundation, Inc.,

 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

 */

#include "config.h"

#if ENABLE_ATOMIC && !HAVE_WINDOWS_KTM

#include <stdlib.h>

#include <stdio.h>

#include <string.h>

#include <unistd.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <dirent.h>

#include <errno.h>

#include <unistd.h>

#include "razor-internal.h"

/*

 * Emulated atomic support

 *

 * This implementation is better than nothing, but is certainly not atomic.

 * It does have a couple of advantages over atomic-none:

 *	- If a file operation fails while a package is being installed we

 *	  have a good chance of being able to rollback the transaction to

 *	  a well-known state.

 *	- We behave similarly to atomic-ktm in that changes are not visible

 *	  on disk to non-atomic operations (eg., scripts) until the atomic

 *	  is committed. This makes the testsuite more likely to pick up

 *	  problems that would otherwise only be found when using razor on

 *	  an MS-Windows system which supports KTM.

 */

#ifndef O_BINARY

#define O_BINARY	0

#endif

static void recursive_remove(const char *directory)

{

	DIR *dp;

	struct dirent *dirp;

	char *buf;

	dp = opendir(directory);

	while((dirp = readdir(dp))) {

		if (strcmp(dirp->d_name, ".") && strcmp(dirp->d_name, "..")) {

			buf = malloc(strlen(directory) + strlen(dirp->d_name)

				     + 2);

			sprintf(buf, "%s/%s", directory, dirp->d_name);

			if (remove(buf) < 0)

				recursive_remove(buf);

			free(buf);

		}

	}

	closedir(dp);

	rmdir(directory);

}

RAZOR_EXPORT struct razor_atomic *razor_atomic_open(const char *description)

{

	struct razor_atomic *atomic;

	atomic = zalloc(sizeof *atomic);

	atomic->description = strdup(description);

	return atomic;

}

RAZOR_EXPORT int razor_atomic_commit(struct razor_atomic *atomic)

{

	struct atomic_action *actions;

	if (razor_atomic_in_error_state(atomic))

		return -1;

	if (atomic->actions) {

		actions = atomic_action_list_reverse(atomic->actions);

		atomic->actions = NULL;

		actions = atomic_action_do(atomic, actions);

		atomic_action_free(actions);

	}

	if (atomic->toplevel) {

		recursive_remove(atomic->toplevel);

		free(atomic->toplevel);

		atomic->toplevel = NULL;

	}

	return razor_atomic_in_error_state(atomic);

}

RAZOR_EXPORT void razor_atomic_destroy(struct razor_atomic *atomic)

{

	if (atomic->actions) {

		atomic_action_free(atomic->actions);

		atomic->actions = NULL;

	}

	if (atomic->toplevel) {

		recursive_remove(atomic->toplevel);

		free(atomic->toplevel);

		atomic->toplevel = NULL;

	}

	if (atomic->error)

		razor_error_free(atomic->error);

	free(atomic->description);

	free(atomic);

}

#ifndef MSWIN_API

static char *absolute_path(const char *path)

{

	int len;

	char *result, *subpath, *p, *s, *t;

	result = realpath(path, NULL);

	if (!result && errno == ENOENT) {

		p = strdup(path);

		s = strrchr(p, '/');

		while (s) {

			if (s == p) {

				result = strdup("/");

				break;

			}

			*s = '\0';

			subpath = realpath(p, NULL);

			if (subpath) {

				*s = '/';

				len = strlen(subpath);

				result = malloc(len + strlen(s) + 1);

				memcpy(result, subpath, len);

				strcpy(result + len, s);

				break;

			} else if (errno != ENOENT)

				break;

			t = strrchr(p, '/');

			*s = '/';

			s = t;

		}

		if (!s)

			result = realpath(".", NULL);

		free(p);

	}

	return result;

}

#endif

/*

 * We need a toplevel directory in which to hold temporary files

 * before they are committed. Since we can generally assume that

 * we have write permissions anywhere on the filesystem in

 * question, the best location is at the relevant mount point.

 * The most common case where this assumption fails is when

 * testing, when the current directory is a good choice.

 */

static int

razor_atomic_set_toplevel_from_path(struct razor_atomic *atomic,

				    const char *path)

{

#ifndef MSWIN_API

	dev_t filesystem;

	struct stat buf;

#endif

	if (razor_atomic_in_error_state(atomic))

		return -1;

	if (atomic->toplevel)

		return 0;

#ifdef MSWIN_API

	if (path[0]=='\\' && path[1]=='\\' && path[2] && path[2]!='\\'

	    && strchr(path+3,'\\')) {

		/* We have a UNC path: \\servername\sharename... */

		const char *sharename, *root;

		int disklen;

		sharename = strchr(path+3,'\\')+1;

		root = strchr(sharename,'\\');

		if (root)

		    disklen = root - path;

		else

		    disklen = strlen(path);

		atomic->toplevel =

		  malloc(disklen + strlen("\\atomic-XXXXXX") + 1);

		memcpy(atomic->toplevel, path, disklen);

		strcpy(atomic->toplevel + disklen, "\\atomic-XXXXXX");

	} else if ((*path>='A' && *path<='Z' || *path>='a' && *path<='z') &&

		    path[1]==':') {

		atomic->toplevel = strdup("X:\\atomic-XXXXXX");

		*atomic->toplevel = *path;

	} else {

		DWORD n;

		wchar_t *buf;

		char *dir;

		n = GetCurrentDirectoryW(0, NULL);

		buf = malloc(n * sizeof(wchar_t));

		if (GetCurrentDirectoryW(n, buf)) {

			dir = razor_utf16_to_utf8(buf, n - 1);

			razor_atomic_set_toplevel_from_path(atomic, dir);

			free(dir);

			free(buf);

			return;

		} else

			atomic->toplevel = strdup("C:\\atomic-XXXXXX");

		free(buf);

	}

#else

	{

		/*

		 * Find the mount point (assuming we can write to the

		 * whole filesystem). Otherwise stop at the first

		 * unwritable directory and take one step back.

		 */

		char *s, *abspath, saved;

		int len, can_step_back = 0;

		abspath = absolute_path(path);

		if (!abspath) {

			atomic->error = razor_error_new_posix(path);

			return -1;

		}

		if (stat(abspath, &buf) < 0) {

			if (errno == ENOENT)

				filesystem = 0;

			else {

				atomic->error = razor_error_new_posix(abspath);

				free(abspath);

				return -1;

			}

		} else

			filesystem = buf.st_dev;

		len = strlen(abspath);

		while(len > 1 && (s = strrchr(abspath, '/'))) {

			if (s == abspath) {

				saved = s[1];

				s[1] = '\0';

				len = s + 1 - abspath;

			} else {

				s[0] = '\0';

				len = s - abspath;

			}

			if (stat(abspath, &buf) < 0) {

				if (errno == ENOENT)

					continue;

				else {

				    atomic->error = razor_error_new_posix(abspath);

				    free(abspath);

				    return -1;

				}

			} else if (!filesystem)

				filesystem = buf.st_dev;

			if (buf.st_dev != filesystem || access(abspath, W_OK)) {

				if (can_step_back) {

					if (s == abspath)

						s[1] = saved;

					else

						s[0] = '/';

				}

				len = strlen(abspath);

				break;

			} else

				can_step_back = 1;

		}

		if (len == 1)

			len = 0;	/* Avoid an unslightly double slash. */

		atomic->toplevel = malloc(len + strlen("/.atomic-XXXXXX") + 1);

		memcpy(atomic->toplevel, abspath, len);

		strcpy(atomic->toplevel + len, "/.atomic-XXXXXX");

		free(abspath);

	}

#endif

	if (!mkdtemp(atomic->toplevel)) {

		int err = errno;

#ifdef EACCES

		if (err == EACCES) {

			char *s = strdup("atomic-XXXXXX");

#ifndef MSWIN_API

			if (stat(".", &buf) < 0) {

				atomic->error = razor_error_new_posix(".");

				free(s);

				free(atomic->toplevel);

				atomic->toplevel = NULL;

				return -1;

			}

			if (buf.st_dev != filesystem)

				/*

				 * Don't use a different filesystem. It will

				 * only fail later on (in rename) and cause

				 * an unhelpful error message (EXDEV).

				 */

				free(s);

			else

#endif

			if (mkdtemp(s)) {

				free(atomic->toplevel);

				atomic->toplevel = s;

				return 0;

			} else

				free(s);

		}

#endif

		atomic->error = razor_error_new_str(RAZOR_POSIX_ERROR, err,

						    atomic->toplevel,

						    strerror(err));

		free(atomic->toplevel);

		atomic->toplevel = NULL;

	}

	return !atomic->toplevel;

}

RAZOR_EXPORT int

razor_atomic_make_dirs(struct razor_atomic *atomic, const char *root,

		       const char *path)

{

	struct atomic_action *a;

	razor_atomic_set_toplevel_from_path(atomic, *root ? root : path);

	if (razor_atomic_in_error_state(atomic))

		return -1;

	a = atomic_action_new(ACTION_MAKE_DIRS);

	a->args.path = strdup(path);

	a->args.u.make_dirs.root = strdup(root);

	atomic->actions = atomic_action_list_prepend(atomic->actions, a);

	return 0;

}

RAZOR_EXPORT int

razor_atomic_remove(struct razor_atomic *atomic, const char *path)

{

	struct atomic_action *a;

	razor_atomic_set_toplevel_from_path(atomic, path);

	if (razor_atomic_in_error_state(atomic))

		return -1;

	a = atomic_action_new(ACTION_REMOVE);

	a->args.path = strdup(path);

	atomic->actions = atomic_action_list_prepend(atomic->actions, a);

	return 0;

}

RAZOR_EXPORT int

razor_atomic_rename_file(struct razor_atomic *atomic, const char *oldpath,

			 const char *newpath)

{

	struct atomic_action *a;

	razor_atomic_set_toplevel_from_path(atomic, newpath);

	if (razor_atomic_in_error_state(atomic))

		return -1;

	a = atomic_action_new(ACTION_MOVE);

	a->args.path = strdup(oldpath);

	a->args.u.move.dest = strdup(newpath);

	atomic->actions = atomic_action_list_prepend(atomic->actions, a);

	return 0;

}

RAZOR_EXPORT int

razor_atomic_create_dir(struct razor_atomic *atomic, const char *dirname,

			mode_t mode)

{

	struct atomic_action *a;

	razor_atomic_set_toplevel_from_path(atomic, dirname);

	if (razor_atomic_in_error_state(atomic))

		return -1;

	a = atomic_action_new(ACTION_CREATE_DIR);

	a->args.path = strdup(dirname);

	a->args.u.create_dir.mode = mode;

	atomic->actions = atomic_action_list_prepend(atomic->actions, a);

	return 0;

}

RAZOR_EXPORT int

razor_atomic_create_symlink(struct razor_atomic *atomic, const char *target,

			    const char *path)

{

#if HAVE_SYMLINK

	struct atomic_action *a;

	razor_atomic_set_toplevel_from_path(atomic, path);

#endif

	if (razor_atomic_in_error_state(atomic))

		return -1;

#if HAVE_SYMLINK

	a = atomic_action_new(ACTION_CREATE_SYMLINK);

	a->args.path = strdup(path);

	a->args.u.create_symlink.target = strdup(target);

	atomic->actions = atomic_action_list_prepend(atomic->actions, a);

	return 0;

#else

	atomic->error = razor_error_new_str(RAZOR_POSIX_ERROR, ENOSYS, NULL,

					    "Symbolic links not supported "

					    "on this platform");

	return -1;

#endif

}

RAZOR_EXPORT int

razor_atomic_create_file(struct razor_atomic *atomic, const char *filename,

                         mode_t mode)

{

	int fd;

	struct atomic_action *a;

	char *tmpnam;

	razor_atomic_set_toplevel_from_path(atomic, filename);

	if (razor_atomic_in_error_state(atomic))

		return -1;

	tmpnam = atomic_action_attic_tmpnam(atomic);

	fd = open(tmpnam, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY,

		  mode & (S_IRWXU | S_IRWXG | S_IRWXO));

	if (fd == -1)

		atomic->error = razor_error_new_posix(filename);

	else {

		a = atomic_action_new(ACTION_MOVE);

		a->args.path = tmpnam;

		a->args.u.move.dest = strdup(filename);

		atomic->actions = atomic_action_list_prepend(atomic->actions,

							     a);

	}

	return fd;

}

#endif	/* ENABLE_ATOMIC && !HAVE_WINDOWS_KTM */