/*

 * Copyright (C) 2012  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 <limits.h>

#include <errno.h>

#include <sys/stat.h>

#include <sys/types.h>

#include <dirent.h>

#include <assert.h>

#include "razor-internal.h"

char *atomic_action_attic_tmpnam(struct razor_atomic *atomic)

{

	char filename[17];

	sprintf(filename,"%03X",atomic->next_file_tag++);

	return razor_concat(atomic->toplevel, "/", filename, NULL);

}

static struct atomic_action *

atomic_action_list_pop_head(struct atomic_action **list)

{

	struct atomic_action *head;

	head = *list;

	if (head) {

		*list = head->next;

		head->next = NULL;

	}

	return head;

}

struct atomic_action *

atomic_action_list_prepend(struct atomic_action *list,

			   struct atomic_action *action)

{

	assert(action->next == NULL);

	action->next=list;

	return action;

}

static struct atomic_action *

atomic_action_list_concat(struct atomic_action *list1,

			  struct atomic_action *list2)

{

	struct atomic_action *action;

	if (!list1)

		return list2;

	for(action=list1;action->next;action=action->next)

		;

	action->next=list2;

	return list1;

}

void atomic_action_free(struct atomic_action *action)

{

	struct atomic_action *a;

	while(action) {

		a = atomic_action_list_pop_head(&action);

		free(a->args.path);

		switch(a->type) {

		case ACTION_MAKE_DIRS:

			free(a->args.u.make_dirs.root);

			break;

		case ACTION_MOVE:

			free(a->args.u.move.dest);

			break;

#if HAVE_SYMLINK

		case ACTION_CREATE_SYMLINK:

			free(a->args.u.create_symlink.target);

			break;

#endif

		case ACTION_REMOVE:

		case ACTION_CREATE_DIR:

			break;

		}

		free(a);

	}

}

struct atomic_action *atomic_action_new(enum atomic_action_type type)

{

	struct atomic_action *action;

	action = zalloc(sizeof *action);

	action->type = type;

	return action;

}

struct atomic_action *atomic_action_list_reverse(struct atomic_action *list)

{

	struct atomic_action *prev = NULL, *next;

	while(list) {

		next = list->next;

		list->next = prev;

		prev = list;

		list = next;

	}

	return prev;

}

/*

 * All action_ functions take 1 action and return a list of primitive

 * actions they took (such that the first action in the list is the

 * last action they took). Primitive actions are always reversable.

 *

 * On failure, an error should be set on the atomic object (if it is

 * not already set), the action freed and NULL returned.

 *

 * Whether they succeed or fail, they take ownership of the passed

 * action and should thus either free it or return it back to their

 * caller as appropriate.

 *

 * A NULL return means that nothing was done which may, or may not,

 * indicate an error.

 */

static struct atomic_action *

atomic_action_make_dirs(struct razor_atomic *atomic,

			struct atomic_action *action)

{

	char buffer[PATH_MAX], *p;

	const char *slash, *next;

	struct atomic_action *primitives = NULL;

	struct atomic_action *prim;

	if (razor_atomic_in_error_state(atomic)) {

		atomic_action_free(action);

		return NULL;

	}

	strcpy(buffer, action->args.u.make_dirs.root);

	p = buffer + strlen(buffer);

	slash = action->args.path;

	for (; *slash != '\0'; slash = next) {

#ifdef MSWIN_API

		next = strpbrk(slash + 1, "/\\");

#else

		next = strchr(slash + 1, '/');

#endif

		if (next == NULL)

			break;

		memcpy(p, slash, next - slash);

		p += next - slash;

		*p = '\0';

		if (razor_valid_root_name(buffer))

			continue;

		prim = atomic_action_new(ACTION_CREATE_DIR);

		prim->args.path = strdup(buffer);

		prim->args.u.create_dir.mode = S_IRWXU | S_IRWXG | S_IRWXO;

		primitives = atomic_action_list_prepend(primitives, prim);

	}

	primitives = atomic_action_list_reverse(primitives);

	atomic_action_free(action);

	return atomic_action_do(atomic, primitives);

}

static struct atomic_action *

atomic_action_remove(struct razor_atomic *atomic, struct atomic_action *action)

{

#ifdef MSWIN_API

	wchar_t *path;

	_WDIR *dir;

#else

	DIR *dir;

#endif

	struct atomic_action *prim;

	if (razor_atomic_in_error_state(atomic)) {

		atomic_action_free(action);

		return NULL;

	}

	/*

	 * Non-empty directories should NOT be removed

	 */

#ifdef MSWIN_API

	path = razor_utf8_to_utf16(action->args.path, -1);

	dir = _wopendir(path);

	if (dir && _wreaddir(dir)) {

		atomic_action_free(action);

		action = NULL;

	}

	_wclosedir(dir);

#else

	dir = opendir(action->args.path);

	if (dir && readdir(dir)) {

		atomic_action_free(action);

		action = NULL;

	}

	closedir(dir);

#endif

	if (action) {

		prim = atomic_action_new(ACTION_MOVE);

		prim->args.path = strdup(action->args.path);

		prim->args.u.move.dest = atomic_action_attic_tmpnam(atomic);

		atomic_action_free(action);

	} else

		prim = NULL;

	return prim ? atomic_action_do(atomic, prim) : NULL;

}

static struct atomic_action *

atomic_action_create_dir(struct razor_atomic *atomic,

			 struct atomic_action *action)

{

	mode_t mode;

	struct stat buf;

	if (razor_atomic_in_error_state(atomic)) {

		atomic_action_free(action);

		return NULL;

	}

	mode = action->args.u.create_dir.mode & (S_IRWXU | S_IRWXG | S_IRWXO);

	if (!mkdir(action->args.path, mode))

		return action;

	if (errno != EEXIST || stat(action->args.path, &buf)) {

		if (!atomic->error)

			atomic->error = razor_error_new_posix(action->args.path);

		atomic_action_free(action);

		return NULL;

	}

	if (!S_ISDIR(buf.st_mode) && !atomic->error)

		atomic->error = razor_error_new_str(RAZOR_POSIX_ERROR, EEXIST,

						    action->args.path,

						    "Not a directory");

	atomic_action_free(action);

	return NULL;

}

static struct atomic_action *atomic_action_rmdir(struct razor_atomic *atomic,

						 struct atomic_action *action)

{

	if (razor_atomic_in_error_state(atomic)) {

		atomic_action_free(action);

		return NULL;

	}

	if (rmdir(action->args.path) < 0) {

		if (!atomic->error)

			atomic->error = razor_error_new_posix(action->args.path);

		atomic_action_free(action);

		return NULL;

	} else

		return action;

}

#if HAVE_SYMLINK

static struct atomic_action *

atomic_action_create_symlink(struct razor_atomic *atomic,

			     struct atomic_action *action)

{

	int r;

	if (razor_atomic_in_error_state(atomic)) {

		atomic_action_free(action);

		return NULL;

	}

	r = symlink(action->args.u.create_symlink.target, action->args.path);

	if (r < 0) {

		if (!atomic->error)

			atomic->error = razor_error_new_posix(action->args.path);

		atomic_action_free(action);

		return NULL;

	}

	return action;

}

static struct atomic_action *

atomic_action_remove_symlink(struct razor_atomic *atomic,

			     struct atomic_action *action)

{

	if (razor_atomic_in_error_state(atomic)) {

		atomic_action_free(action);

		return NULL;

	}

	if (unlink(action->args.path) < 0) {

		if (!atomic->error)

			atomic->error = razor_error_new_posix(action->args.path);

		atomic_action_free(action);

		return NULL;

	}

	return action;

}

#endif

static int

move_file(struct razor_atomic *atomic, const char *path, const char *dest)

{

#ifdef MSWIN_API

	wchar_t *oldbuf, *newbuf;

	const DWORD flags = MOVEFILE_COPY_ALLOWED | MOVEFILE_REPLACE_EXISTING;

	newbuf = razor_utf8_to_utf16(dest, -1);

	oldbuf = razor_utf8_to_utf16(path, -1);

	/*

	 * Passing MOVEFILE_REPLACE_EXISTING to MoveFileEx() will

	 * cover every case we care about _except_ replacing an empty

	 * directory with a file. Calling RemoveDirectory() will deal

	 * with this case while having no effect in all other cases.

	 */

	(void)RemoveDirectoryW(newbuf);

	if (!MoveFileExW(oldbuf, newbuf, flags)) {

		if (!atomic->error)

			atomic->error = razor_error_new_mswin(newbuf,

							      GetLastError());

		return -1;

	}

	free(newbuf);

	free(oldbuf);

#else

	if (rename(path, dest)) {

		if (!atomic->error)

			atomic->error = razor_error_new_posix(dest);

		return -1;

	}

#endif

	return 0;

}

static struct atomic_action *

atomic_action_move(struct razor_atomic *atomic, struct atomic_action *action)

{

	if (razor_atomic_in_error_state(atomic)) {

		atomic_action_free(action);

		return NULL;

	}

	if (move_file(atomic, action->args.path, action->args.u.move.dest)) {

		atomic_action_free(action);

		return NULL;

	}

	return action;

}

static struct atomic_action *

atomic_action_unmove(struct razor_atomic *atomic, struct atomic_action *action)

{

	if (razor_atomic_in_error_state(atomic)) {

		atomic_action_free(action);

		return NULL;

	}

	if (move_file(atomic, action->args.u.move.dest, action->args.path)) {

		atomic_action_free(action);

		return NULL;

	}

	return action;

}

static struct atomic_action *atomic_action_apply(struct razor_atomic *atomic,

						 struct atomic_action *action)

{

	switch(action->type) {

	case ACTION_MAKE_DIRS:

		action = atomic_action_make_dirs(atomic, action);

		break;

	case ACTION_REMOVE:

		action = atomic_action_remove(atomic, action);

		break;

	case ACTION_CREATE_DIR:

		action = atomic_action_create_dir(atomic, action);

		break;

	case ACTION_MOVE:

		action = atomic_action_move(atomic, action);

		break;

#if HAVE_SYMLINK

	case ACTION_CREATE_SYMLINK:

		action = atomic_action_create_symlink(atomic, action);

		break;

#endif

	}

	return action;

}

static struct atomic_action *atomic_action_reverse(struct razor_atomic *atomic,

						   struct atomic_action *action)

{

	switch(action->type) {

	case ACTION_MAKE_DIRS:

	case ACTION_REMOVE:

		/* Complex actions: should never happen */

		break;

	case ACTION_CREATE_DIR:

		action = atomic_action_rmdir(atomic, action);

		break;

	case ACTION_MOVE:

		action = atomic_action_unmove(atomic, action);

		break;

#if HAVE_SYMLINK

	case ACTION_CREATE_SYMLINK:

		action = atomic_action_remove_symlink(atomic, action);

		break;

#endif

	}

	return action;

}

/*

 * Note that undo has no error checking.

 */

void atomic_action_undo(struct razor_atomic *atomic,

			struct atomic_action *actions)

{

	struct atomic_action *a;

	atomic->in_undo = 1;

	while (actions) {

		a = atomic_action_list_pop_head(&actions);

		a = atomic_action_reverse(atomic, a);

		atomic_action_free(a);

	}

	atomic->in_undo = 0;

}

struct atomic_action *atomic_action_do(struct razor_atomic *atomic,

				       struct atomic_action *actions)

{

	struct atomic_action *done = NULL, *a;

	if (razor_atomic_in_error_state(atomic)) {

		atomic_action_free(actions);

		return NULL;

	}

	while (actions) {

		a = atomic_action_list_pop_head(&actions);

		a = atomic_action_apply(atomic, a);

		if (a)

			done = atomic_action_list_concat(a, done);

		if (razor_atomic_in_error_state(atomic)) {

			atomic_action_undo(atomic, done);

			done = NULL;

			atomic_action_free(a);

		}

	}

	return done;

}

#endif	/* ENABLE_ATOMIC && !HAVE_WINDOWS_KTM */