1<?php
  2/**
  3 * Post revision functions.
  4 *
  5 * @package WordPress
  6 * @subpackage Post_Revisions
  7 */
  8
  9/**
 10 * Determines which fields of posts are to be saved in revisions.
 11 *
 12 * @since 2.6.0
 13 * @since 4.5.0 A `WP_Post` object can now be passed to the `$post` parameter.
 14 * @since 4.5.0 The optional `$autosave` parameter was deprecated and renamed to `$deprecated`.
 15 * @access private
 16 *
 17 * @param array|WP_Post $post       Optional. A post array or a WP_Post object being processed
 18 *                                  for insertion as a post revision. Default empty array.
 19 * @param bool          $deprecated Not used.
 20 * @return string[] Array of fields that can be versioned.
 21 */
 22function _wp_post_revision_fields( $post = array(), $deprecated = false ) {
 23	static $fields = null;
 24
 25	if ( ! is_array( $post ) ) {
 26		$post = get_post( $post, ARRAY_A );
 27	}
 28
 29	if ( is_null( $fields ) ) {
 30		// Allow these to be versioned.
 31		$fields = array(
 32			'post_title'   => __( 'Title' ),
 33			'post_content' => __( 'Content' ),
 34			'post_excerpt' => __( 'Excerpt' ),
 35		);
 36	}
 37
 38	/**
 39	 * Filters the list of fields saved in post revisions.
 40	 *
 41	 * Included by default: 'post_title', 'post_content' and 'post_excerpt'.
 42	 *
 43	 * Disallowed fields: 'ID', 'post_name', 'post_parent', 'post_date',
 44	 * 'post_date_gmt', 'post_status', 'post_type', 'comment_count',
 45	 * and 'post_author'.
 46	 *
 47	 * @since 2.6.0
 48	 * @since 4.5.0 The `$post` parameter was added.
 49	 *
 50	 * @param string[] $fields List of fields to revision. Contains 'post_title',
 51	 *                         'post_content', and 'post_excerpt' by default.
 52	 * @param array    $post   A post array being processed for insertion as a post revision.
 53	 */
 54	$fields = apply_filters( '_wp_post_revision_fields', $fields, $post );
 55
 56	// WP uses these internally either in versioning or elsewhere - they cannot be versioned.
 57	foreach ( array( 'ID', 'post_name', 'post_parent', 'post_date', 'post_date_gmt', 'post_status', 'post_type', 'comment_count', 'post_author' ) as $protect ) {
 58		unset( $fields[ $protect ] );
 59	}
 60
 61	return $fields;
 62}
 63
 64/**
 65 * Returns a post array ready to be inserted into the posts table as a post revision.
 66 *
 67 * @since 4.5.0
 68 * @access private
 69 *
 70 * @param array|WP_Post $post     Optional. A post array or a WP_Post object to be processed
 71 *                                for insertion as a post revision. Default empty array.
 72 * @param bool          $autosave Optional. Is the revision an autosave? Default false.
 73 * @return array Post array ready to be inserted as a post revision.
 74 */
 75function _wp_post_revision_data( $post = array(), $autosave = false ) {
 76	if ( ! is_array( $post ) ) {
 77		$post = get_post( $post, ARRAY_A );
 78	}
 79
 80	$fields = _wp_post_revision_fields( $post );
 81
 82	$revision_data = array();
 83
 84	foreach ( array_intersect( array_keys( $post ), array_keys( $fields ) ) as $field ) {
 85		$revision_data[ $field ] = $post[ $field ];
 86	}
 87
 88	$revision_data['post_parent']   = $post['ID'];
 89	$revision_data['post_status']   = 'inherit';
 90	$revision_data['post_type']     = 'revision';
 91	$revision_data['post_name']     = $autosave ? "$post[ID]-autosave-v1" : "$post[ID]-revision-v1"; // "1" is the revisioning system version.
 92	$revision_data['post_date']     = isset( $post['post_modified'] ) ? $post['post_modified'] : '';
 93	$revision_data['post_date_gmt'] = isset( $post['post_modified_gmt'] ) ? $post['post_modified_gmt'] : '';
 94
 95	return $revision_data;
 96}
 97
 98/**
 99 * Saves revisions for a post after all changes have been made.
100 *
101 * @since 6.4.0
102 *
103 * @param int     $post_id The post id that was inserted.
104 * @param WP_Post $post    The post object that was inserted.
105 * @param bool    $update  Whether this insert is updating an existing post.
106 */
107function wp_save_post_revision_on_insert( $post_id, $post, $update ) {
108	if ( ! $update ) {
109		return;
110	}
111
112	if ( ! has_action( 'post_updated', 'wp_save_post_revision' ) ) {
113		return;
114	}
115
116	wp_save_post_revision( $post_id );
117}
118
119/**
120 * Creates a revision for the current version of a post.
121 *
122 * Typically used immediately after a post update, as every update is a revision,
123 * and the most recent revision always matches the current post.
124 *
125 * @since 2.6.0
126 *
127 * @param int $post_id The ID of the post to save as a revision.
128 * @return int|WP_Error|void Void or 0 if error, new revision ID, if success.
129 */
130function wp_save_post_revision( $post_id ) {
131	if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) {
132		return;
133	}
134
135	// Prevent saving post revisions if revisions should be saved on wp_after_insert_post.
136	if ( doing_action( 'post_updated' ) && has_action( 'wp_after_insert_post', 'wp_save_post_revision_on_insert' ) ) {
137		return;
138	}
139
140	$post = get_post( $post_id );
141
142	if ( ! $post ) {
143		return;
144	}
145
146	if ( ! post_type_supports( $post->post_type, 'revisions' ) ) {
147		return;
148	}
149
150	if ( 'auto-draft' === $post->post_status ) {
151		return;
152	}
153
154	if ( ! wp_revisions_enabled( $post ) ) {
155		return;
156	}
157
158	/*
159	 * Compare the proposed update with the last stored revision verifying that
160	 * they are different, unless a plugin tells us to always save regardless.
161	 * If no previous revisions, save one.
162	 */
163	$revisions = wp_get_post_revisions( $post_id );
164	if ( $revisions ) {
165		// Grab the latest revision, but not an autosave.
166		foreach ( $revisions as $revision ) {
167			if ( str_contains( $revision->post_name, "{$revision->post_parent}-revision" ) ) {
168				$latest_revision = $revision;
169				break;
170			}
171		}
172
173		/**
174		 * Filters whether the post has changed since the latest revision.
175		 *
176		 * By default a revision is saved only if one of the revisioned fields has changed.
177		 * This filter can override that so a revision is saved even if nothing has changed.
178		 *
179		 * @since 3.6.0
180		 *
181		 * @param bool    $check_for_changes Whether to check for changes before saving a new revision.
182		 *                                   Default true.
183		 * @param WP_Post $latest_revision   The latest revision post object.
184		 * @param WP_Post $post              The post object.
185		 */
186		if ( isset( $latest_revision ) && apply_filters( 'wp_save_post_revision_check_for_changes', true, $latest_revision, $post ) ) {
187			$post_has_changed = false;
188
189			foreach ( array_keys( _wp_post_revision_fields( $post ) ) as $field ) {
190				if ( normalize_whitespace( $post->$field ) !== normalize_whitespace( $latest_revision->$field ) ) {
191					$post_has_changed = true;
192					break;
193				}
194			}
195
196			/**
197			 * Filters whether a post has changed.
198			 *
199			 * By default a revision is saved only if one of the revisioned fields has changed.
200			 * This filter allows for additional checks to determine if there were changes.
201			 *
202			 * @since 4.1.0
203			 *
204			 * @param bool    $post_has_changed Whether the post has changed.
205			 * @param WP_Post $latest_revision  The latest revision post object.
206			 * @param WP_Post $post             The post object.
207			 */
208			$post_has_changed = (bool) apply_filters( 'wp_save_post_revision_post_has_changed', $post_has_changed, $latest_revision, $post );
209
210			// Don't save revision if post unchanged.
211			if ( ! $post_has_changed ) {
212				return;
213			}
214		}
215	}
216
217	$return = _wp_put_post_revision( $post );
218
219	/*
220	 * If a limit for the number of revisions to keep has been set,
221	 * delete the oldest ones.
222	 */
223	$revisions_to_keep = wp_revisions_to_keep( $post );
224
225	if ( $revisions_to_keep < 0 ) {
226		return $return;
227	}
228
229	$revisions = wp_get_post_revisions( $post_id, array( 'order' => 'ASC' ) );
230
231	/**
232	 * Filters the revisions to be considered for deletion.
233	 *
234	 * @since 6.2.0
235	 *
236	 * @param WP_Post[] $revisions Array of revisions, or an empty array if none.
237	 * @param int       $post_id   The ID of the post to save as a revision.
238	 */
239	$revisions = apply_filters(
240		'wp_save_post_revision_revisions_before_deletion',
241		$revisions,
242		$post_id
243	);
244
245	$delete = count( $revisions ) - $revisions_to_keep;
246
247	if ( $delete < 1 ) {
248		return $return;
249	}
250
251	$revisions = array_slice( $revisions, 0, $delete );
252
253	for ( $i = 0; isset( $revisions[ $i ] ); $i++ ) {
254		if ( str_contains( $revisions[ $i ]->post_name, 'autosave' ) ) {
255			continue;
256		}
257
258		wp_delete_post_revision( $revisions[ $i ]->ID );
259	}
260
261	return $return;
262}
263
264/**
265 * Retrieves the autosaved data of the specified post.
266 *
267 * Returns a post object with the information that was autosaved for the specified post.
268 * If the optional $user_id is passed, returns the autosave for that user, otherwise
269 * returns the latest autosave.
270 *
271 * @since 2.6.0
272 *
273 * @param int $post_id The post ID.
274 * @param int $user_id Optional. The post author ID. Default 0.
275 * @return WP_Post|false The autosaved data or false on failure or when no autosave exists.
276 */
277function wp_get_post_autosave( $post_id, $user_id = 0 ) {
278	$args = array(
279		'post_type'      => 'revision',
280		'post_status'    => 'inherit',
281		'post_parent'    => $post_id,
282		'name'           => $post_id . '-autosave-v1',
283		'posts_per_page' => 1,
284		'orderby'        => 'date',
285		'order'          => 'DESC',
286		'fields'         => 'ids',
287		'no_found_rows'  => true,
288	);
289
290	if ( 0 !== $user_id ) {
291		$args['author'] = $user_id;
292	}
293
294	$query = new WP_Query( $args );
295
296	if ( ! $query->have_posts() ) {
297		return false;
298	}
299
300	return get_post( $query->posts[0] );
301}
302
303/**
304 * Determines if the specified post is a revision.
305 *
306 * @since 2.6.0
307 *
308 * @param int|WP_Post $post Post ID or post object.
309 * @return int|false ID of revision's parent on success, false if not a revision.
310 */
311function wp_is_post_revision( $post ) {
312	$post = wp_get_post_revision( $post );
313
314	if ( ! $post ) {
315		return false;
316	}
317
318	return (int) $post->post_parent;
319}
320
321/**
322 * Determines if the specified post is an autosave.
323 *
324 * @since 2.6.0
325 *
326 * @param int|WP_Post $post Post ID or post object.
327 * @return int|false ID of autosave's parent on success, false if not a revision.
328 */
329function wp_is_post_autosave( $post ) {
330	$post = wp_get_post_revision( $post );
331
332	if ( ! $post ) {
333		return false;
334	}
335
336	if ( str_contains( $post->post_name, "{$post->post_parent}-autosave" ) ) {
337		return (int) $post->post_parent;
338	}
339
340	return false;
341}
342
343/**
344 * Inserts post data into the posts table as a post revision.
345 *
346 * @since 2.6.0
347 * @access private
348 *
349 * @param int|WP_Post|array|null $post     Post ID, post object OR post array.
350 * @param bool                   $autosave Optional. Whether the revision is an autosave or not.
351 *                                         Default false.
352 * @return int|WP_Error WP_Error or 0 if error, new revision ID if success.
353 */
354function _wp_put_post_revision( $post = null, $autosave = false ) {
355	if ( is_object( $post ) ) {
356		$post = get_object_vars( $post );
357	} elseif ( ! is_array( $post ) ) {
358		$post = get_post( $post, ARRAY_A );
359	}
360
361	if ( ! $post || empty( $post['ID'] ) ) {
362		return new WP_Error( 'invalid_post', __( 'Invalid post ID.' ) );
363	}
364
365	if ( isset( $post['post_type'] ) && 'revision' === $post['post_type'] ) {
366		return new WP_Error( 'post_type', __( 'Cannot create a revision of a revision' ) );
367	}
368
369	$post = _wp_post_revision_data( $post, $autosave );
370	$post = wp_slash( $post ); // Since data is from DB.
371
372	$revision_id = wp_insert_post( $post, true );
373	if ( is_wp_error( $revision_id ) ) {
374		return $revision_id;
375	}
376
377	if ( $revision_id ) {
378		/**
379		 * Fires once a revision has been saved.
380		 *
381		 * @since 2.6.0
382		 * @since 6.4.0 The post_id parameter was added.
383		 *
384		 * @param int $revision_id Post revision ID.
385		 * @param int $post_id     Post ID.
386		 */
387		do_action( '_wp_put_post_revision', $revision_id, $post['post_parent'] );
388	}
389
390	return $revision_id;
391}
392
393
394/**
395 * Save the revisioned meta fields.
396 *
397 * @since 6.4.0
398 *
399 * @param int $revision_id The ID of the revision to save the meta to.
400 * @param int $post_id     The ID of the post the revision is associated with.
401 */
402function wp_save_revisioned_meta_fields( $revision_id, $post_id ) {
403	$post_type = get_post_type( $post_id );
404	if ( ! $post_type ) {
405		return;
406	}
407
408	foreach ( wp_post_revision_meta_keys( $post_type ) as $meta_key ) {
409		if ( metadata_exists( 'post', $post_id, $meta_key ) ) {
410			_wp_copy_post_meta( $post_id, $revision_id, $meta_key );
411		}
412	}
413}
414
415/**
416 * Gets a post revision.
417 *
418 * @since 2.6.0
419 *
420 * @param int|WP_Post $post   Post ID or post object.
421 * @param string      $output Optional. The required return type. One of OBJECT, ARRAY_A, or ARRAY_N, which
422 *                            correspond to a WP_Post object, an associative array, or a numeric array,
423 *                            respectively. Default OBJECT.
424 * @param string      $filter Optional sanitization filter. See sanitize_post(). Default 'raw'.
425 * @return WP_Post|array|null WP_Post (or array) on success, or null on failure.
426 */
427function wp_get_post_revision( &$post, $output = OBJECT, $filter = 'raw' ) {
428	$revision = get_post( $post, OBJECT, $filter );
429
430	if ( ! $revision ) {
431		return $revision;
432	}
433
434	if ( 'revision' !== $revision->post_type ) {
435		return null;
436	}
437
438	if ( OBJECT === $output ) {
439		return $revision;
440	} elseif ( ARRAY_A === $output ) {
441		$_revision = get_object_vars( $revision );
442		return $_revision;
443	} elseif ( ARRAY_N === $output ) {
444		$_revision = array_values( get_object_vars( $revision ) );
445		return $_revision;
446	}
447
448	return $revision;
449}
450
451/**
452 * Restores a post to the specified revision.
453 *
454 * Can restore a past revision using all fields of the post revision, or only selected fields.
455 *
456 * @since 2.6.0
457 *
458 * @param int|WP_Post $revision Revision ID or revision object.
459 * @param array       $fields   Optional. What fields to restore from. Defaults to all.
460 * @return int|false|null Null if error, false if no fields to restore, (int) post ID if success.
461 */
462function wp_restore_post_revision( $revision, $fields = null ) {
463	$revision = wp_get_post_revision( $revision, ARRAY_A );
464
465	if ( ! $revision ) {
466		return $revision;
467	}
468
469	if ( ! is_array( $fields ) ) {
470		$fields = array_keys( _wp_post_revision_fields( $revision ) );
471	}
472
473	$update = array();
474	foreach ( array_intersect( array_keys( $revision ), $fields ) as $field ) {
475		$update[ $field ] = $revision[ $field ];
476	}
477
478	if ( ! $update ) {
479		return false;
480	}
481
482	$update['ID'] = $revision['post_parent'];
483
484	$update = wp_slash( $update ); // Since data is from DB.
485
486	$post_id = wp_update_post( $update );
487
488	if ( ! $post_id || is_wp_error( $post_id ) ) {
489		return $post_id;
490	}
491
492	// Update last edit user.
493	update_post_meta( $post_id, '_edit_last', get_current_user_id() );
494
495	/**
496	 * Fires after a post revision has been restored.
497	 *
498	 * @since 2.6.0
499	 *
500	 * @param int $post_id     Post ID.
501	 * @param int $revision_id Post revision ID.
502	 */
503	do_action( 'wp_restore_post_revision', $post_id, $revision['ID'] );
504
505	return $post_id;
506}
507
508/**
509 * Restore the revisioned meta values for a post.
510 *
511 * @since 6.4.0
512 *
513 * @param int $post_id     The ID of the post to restore the meta to.
514 * @param int $revision_id The ID of the revision to restore the meta from.
515 */
516function wp_restore_post_revision_meta( $post_id, $revision_id ) {
517	$post_type = get_post_type( $post_id );
518	if ( ! $post_type ) {
519		return;
520	}
521
522	// Restore revisioned meta fields.
523	foreach ( wp_post_revision_meta_keys( $post_type ) as $meta_key ) {
524
525		// Clear any existing meta.
526		delete_post_meta( $post_id, $meta_key );
527
528		_wp_copy_post_meta( $revision_id, $post_id, $meta_key );
529	}
530}
531
532/**
533 * Copy post meta for the given key from one post to another.
534 *
535 * @since 6.4.0
536 *
537 * @param int    $source_post_id Post ID to copy meta value(s) from.
538 * @param int    $target_post_id Post ID to copy meta value(s) to.
539 * @param string $meta_key       Meta key to copy.
540 */
541function _wp_copy_post_meta( $source_post_id, $target_post_id, $meta_key ) {
542
543	foreach ( get_post_meta( $source_post_id, $meta_key ) as $meta_value ) {
544		/**
545		 * We use add_metadata() function vs add_post_meta() here
546		 * to allow for a revision post target OR regular post.
547		 */
548		add_metadata( 'post', $target_post_id, $meta_key, wp_slash( $meta_value ) );
549	}
550}
551
552/**
553 * Determine which post meta fields should be revisioned.
554 *
555 * @since 6.4.0
556 *
557 * @param string $post_type The post type being revisioned.
558 * @return array An array of meta keys to be revisioned.
559 */
560function wp_post_revision_meta_keys( $post_type ) {
561	$registered_meta = array_merge(
562		get_registered_meta_keys( 'post' ),
563		get_registered_meta_keys( 'post', $post_type )
564	);
565
566	$wp_revisioned_meta_keys = array();
567
568	foreach ( $registered_meta as $name => $args ) {
569		if ( $args['revisions_enabled'] ) {
570			$wp_revisioned_meta_keys[ $name ] = true;
571		}
572	}
573
574	$wp_revisioned_meta_keys = array_keys( $wp_revisioned_meta_keys );
575
576	/**
577	 * Filter the list of post meta keys to be revisioned.
578	 *
579	 * @since 6.4.0
580	 *
581	 * @param array  $keys      An array of meta fields to be revisioned.
582	 * @param string $post_type The post type being revisioned.
583	 */
584	return apply_filters( 'wp_post_revision_meta_keys', $wp_revisioned_meta_keys, $post_type );
585}
586
587/**
588 * Check whether revisioned post meta fields have changed.
589 *
590 * @since 6.4.0
591 *
592 * @param bool    $post_has_changed Whether the post has changed.
593 * @param WP_Post $last_revision    The last revision post object.
594 * @param WP_Post $post             The post object.
595 * @return bool Whether the post has changed.
596 */
597function wp_check_revisioned_meta_fields_have_changed( $post_has_changed, WP_Post $last_revision, WP_Post $post ) {
598	foreach ( wp_post_revision_meta_keys( $post->post_type ) as $meta_key ) {
599		if ( get_post_meta( $post->ID, $meta_key ) !== get_post_meta( $last_revision->ID, $meta_key ) ) {
600			$post_has_changed = true;
601			break;
602		}
603	}
604	return $post_has_changed;
605}
606
607/**
608 * Deletes a revision.
609 *
610 * Deletes the row from the posts table corresponding to the specified revision.
611 *
612 * @since 2.6.0
613 *
614 * @param int|WP_Post $revision Revision ID or revision object.
615 * @return WP_Post|false|null Null or false if error, deleted post object if success.
616 */
617function wp_delete_post_revision( $revision ) {
618	$revision = wp_get_post_revision( $revision );
619
620	if ( ! $revision ) {
621		return $revision;
622	}
623
624	$delete = wp_delete_post( $revision->ID );
625
626	if ( $delete ) {
627		/**
628		 * Fires once a post revision has been deleted.
629		 *
630		 * @since 2.6.0
631		 *
632		 * @param int     $revision_id Post revision ID.
633		 * @param WP_Post $revision    Post revision object.
634		 */
635		do_action( 'wp_delete_post_revision', $revision->ID, $revision );
636	}
637
638	return $delete;
639}
640
641/**
642 * Returns all revisions of specified post.
643 *
644 * @since 2.6.0
645 *
646 * @see get_children()
647 *
648 * @param int|WP_Post $post Optional. Post ID or WP_Post object. Default is global `$post`.
649 * @param array|null  $args Optional. Arguments for retrieving post revisions. Default null.
650 * @return WP_Post[]|int[] Array of revision objects or IDs, or an empty array if none.
651 */
652function wp_get_post_revisions( $post = 0, $args = null ) {
653	$post = get_post( $post );
654
655	if ( ! $post || empty( $post->ID ) ) {
656		return array();
657	}
658
659	$defaults = array(
660		'order'         => 'DESC',
661		'orderby'       => 'date ID',
662		'check_enabled' => true,
663	);
664	$args     = wp_parse_args( $args, $defaults );
665
666	if ( $args['check_enabled'] && ! wp_revisions_enabled( $post ) ) {
667		return array();
668	}
669
670	$args = array_merge(
671		$args,
672		array(
673			'post_parent' => $post->ID,
674			'post_type'   => 'revision',
675			'post_status' => 'inherit',
676		)
677	);
678
679	$revisions = get_children( $args );
680
681	if ( ! $revisions ) {
682		return array();
683	}
684
685	return $revisions;
686}
687
688/**
689 * Returns the latest revision ID and count of revisions for a post.
690 *
691 * @since 6.1.0
692 *
693 * @param int|WP_Post $post Optional. Post ID or WP_Post object. Default is global $post.
694 * @return array|WP_Error {
695 *     Returns associative array with latest revision ID and total count,
696 *     or a WP_Error if the post does not exist or revisions are not enabled.
697 *
698 *     @type int $latest_id The latest revision post ID or 0 if no revisions exist.
699 *     @type int $count     The total count of revisions for the given post.
700 * }
701 */
702function wp_get_latest_revision_id_and_total_count( $post = 0 ) {
703	$post = get_post( $post );
704
705	if ( ! $post ) {
706		return new WP_Error( 'invalid_post', __( 'Invalid post.' ) );
707	}
708
709	if ( ! wp_revisions_enabled( $post ) ) {
710		return new WP_Error( 'revisions_not_enabled', __( 'Revisions not enabled.' ) );
711	}
712
713	$args = array(
714		'post_parent'         => $post->ID,
715		'fields'              => 'ids',
716		'post_type'           => 'revision',
717		'post_status'         => 'inherit',
718		'order'               => 'DESC',
719		'orderby'             => 'date ID',
720		'posts_per_page'      => 1,
721		'ignore_sticky_posts' => true,
722	);
723
724	$revision_query = new WP_Query();
725	$revisions      = $revision_query->query( $args );
726
727	if ( ! $revisions ) {
728		return array(
729			'latest_id' => 0,
730			'count'     => 0,
731		);
732	}
733
734	return array(
735		'latest_id' => $revisions[0],
736		'count'     => $revision_query->found_posts,
737	);
738}
739
740/**
741 * Returns the url for viewing and potentially restoring revisions of a given post.
742 *
743 * @since 5.9.0
744 *
745 * @param int|WP_Post $post Optional. Post ID or WP_Post object. Default is global `$post`.
746 * @return string|null The URL for editing revisions on the given post, otherwise null.
747 */
748function wp_get_post_revisions_url( $post = 0 ) {
749	$post = get_post( $post );
750
751	if ( ! $post instanceof WP_Post ) {
752		return null;
753	}
754
755	// If the post is a revision, return early.
756	if ( 'revision' === $post->post_type ) {
757		return get_edit_post_link( $post );
758	}
759
760	if ( ! wp_revisions_enabled( $post ) ) {
761		return null;
762	}
763
764	$revisions = wp_get_latest_revision_id_and_total_count( $post->ID );
765
766	if ( is_wp_error( $revisions ) || 0 === $revisions['count'] ) {
767		return null;
768	}
769
770	return get_edit_post_link( $revisions['latest_id'] );
771}
772
773/**
774 * Determines whether revisions are enabled for a given post.
775 *
776 * @since 3.6.0
777 *
778 * @param WP_Post $post The post object.
779 * @return bool True if number of revisions to keep isn't zero, false otherwise.
780 */
781function wp_revisions_enabled( $post ) {
782	return wp_revisions_to_keep( $post ) !== 0;
783}
784
785/**
786 * Determines how many revisions to retain for a given post.
787 *
788 * By default, an infinite number of revisions are kept.
789 *
790 * The constant WP_POST_REVISIONS can be set in wp-config to specify the limit
791 * of revisions to keep.
792 *
793 * @since 3.6.0
794 *
795 * @param WP_Post $post The post object.
796 * @return int The number of revisions to keep.
797 */
798function wp_revisions_to_keep( $post ) {
799	$num = WP_POST_REVISIONS;
800
801	if ( true === $num ) {
802		$num = -1;
803	} else {
804		$num = (int) $num;
805	}
806
807	if ( ! post_type_supports( $post->post_type, 'revisions' ) ) {
808		$num = 0;
809	}
810
811	/**
812	 * Filters the number of revisions to save for the given post.
813	 *
814	 * Overrides the value of WP_POST_REVISIONS.
815	 *
816	 * @since 3.6.0
817	 *
818	 * @param int     $num  Number of revisions to store.
819	 * @param WP_Post $post Post object.
820	 */
821	$num = apply_filters( 'wp_revisions_to_keep', $num, $post );
822
823	/**
824	 * Filters the number of revisions to save for the given post by its post type.
825	 *
826	 * Overrides both the value of WP_POST_REVISIONS and the {@see 'wp_revisions_to_keep'} filter.
827	 *
828	 * The dynamic portion of the hook name, `$post->post_type`, refers to
829	 * the post type slug.
830	 *
831	 * Possible hook names include:
832	 *
833	 *  - `wp_post_revisions_to_keep`
834	 *  - `wp_page_revisions_to_keep`
835	 *
836	 * @since 5.8.0
837	 *
838	 * @param int     $num  Number of revisions to store.
839	 * @param WP_Post $post Post object.
840	 */
841	$num = apply_filters( "wp_{$post->post_type}_revisions_to_keep", $num, $post );
842
843	return (int) $num;
844}
845
846/**
847 * Sets up the post object for preview based on the post autosave.
848 *
849 * @since 2.7.0
850 * @access private
851 *
852 * @param WP_Post $post
853 * @return WP_Post|false
854 */
855function _set_preview( $post ) {
856	if ( ! is_object( $post ) ) {
857		return $post;
858	}
859
860	$preview = wp_get_post_autosave( $post->ID );
861
862	if ( is_object( $preview ) ) {
863		$preview = sanitize_post( $preview );
864
865		$post->post_content = $preview->post_content;
866		$post->post_title   = $preview->post_title;
867		$post->post_excerpt = $preview->post_excerpt;
868	}
869
870	add_filter( 'get_the_terms', '_wp_preview_terms_filter', 10, 3 );
871	add_filter( 'get_post_metadata', '_wp_preview_post_thumbnail_filter', 10, 3 );
872	add_filter( 'get_post_metadata', '_wp_preview_meta_filter', 10, 4 );
873
874	return $post;
875}
876
877/**
878 * Filters the latest content for preview from the post autosave.
879 *
880 * @since 2.7.0
881 * @access private
882 */
883function _show_post_preview() {
884	if ( isset( $_GET['preview_id'] ) && isset( $_GET['preview_nonce'] ) ) {
885		$id = (int) $_GET['preview_id'];
886
887		if ( false === wp_verify_nonce( $_GET['preview_nonce'], 'post_preview_' . $id ) ) {
888			wp_die( __( 'Sorry, you are not allowed to preview drafts.' ), 403 );
889		}
890
891		add_filter( 'the_preview', '_set_preview' );
892	}
893}
894
895/**
896 * Filters terms lookup to set the post format.
897 *
898 * @since 3.6.0
899 * @access private
900 *
901 * @param array  $terms
902 * @param int    $post_id
903 * @param string $taxonomy
904 * @return array
905 */
906function _wp_preview_terms_filter( $terms, $post_id, $taxonomy ) {
907	$post = get_post();
908
909	if ( ! $post ) {
910		return $terms;
911	}
912
913	if ( empty( $_REQUEST['post_format'] ) || $post->ID !== $post_id
914		|| 'post_format' !== $taxonomy || 'revision' === $post->post_type
915	) {
916		return $terms;
917	}
918
919	if ( 'standard' === $_REQUEST['post_format'] ) {
920		$terms = array();
921	} else {
922		$term = get_term_by( 'slug', 'post-format-' . sanitize_key( $_REQUEST['post_format'] ), 'post_format' );
923
924		if ( $term ) {
925			$terms = array( $term ); // Can only have one post format.
926		}
927	}
928
929	return $terms;
930}
931
932/**
933 * Filters post thumbnail lookup to set the post thumbnail.
934 *
935 * @since 4.6.0
936 * @access private
937 *
938 * @param null|array|string $value    The value to return - a single metadata value, or an array of values.
939 * @param int               $post_id  Post ID.
940 * @param string            $meta_key Meta key.
941 * @return null|array The default return value or the post thumbnail meta array.
942 */
943function _wp_preview_post_thumbnail_filter( $value, $post_id, $meta_key ) {
944	$post = get_post();
945
946	if ( ! $post ) {
947		return $value;
948	}
949
950	if ( empty( $_REQUEST['_thumbnail_id'] ) || empty( $_REQUEST['preview_id'] )
951		|| $post->ID !== $post_id || $post_id !== (int) $_REQUEST['preview_id']
952		|| '_thumbnail_id' !== $meta_key || 'revision' === $post->post_type
953	) {
954		return $value;
955	}
956
957	$thumbnail_id = (int) $_REQUEST['_thumbnail_id'];
958
959	if ( $thumbnail_id <= 0 ) {
960		return '';
961	}
962
963	return (string) $thumbnail_id;
964}
965
966/**
967 * Gets the post revision version.
968 *
969 * @since 3.6.0
970 * @access private
971 *
972 * @param WP_Post $revision
973 * @return int|false
974 */
975function _wp_get_post_revision_version( $revision ) {
976	if ( is_object( $revision ) ) {
977		$revision = get_object_vars( $revision );
978	} elseif ( ! is_array( $revision ) ) {
979		return false;
980	}
981
982	if ( preg_match( '/^\d+-(?:autosave|revision)-v(\d+)$/', $revision['post_name'], $matches ) ) {
983		return (int) $matches[1];
984	}
985
986	return 0;
987}
988
989/**
990 * Upgrades the revisions author, adds the current post as a revision and sets the revisions version to 1.
991 *
992 * @since 3.6.0
993 * @access private
994 *
995 * @global wpdb $wpdb WordPress database abstraction object.
996 *
997 * @param WP_Post $post      Post object.
998 * @param array   $revisions Current revisions of the post.
999 * @return bool true if the revisions were upgraded, false if problems.
1000 */
1001function _wp_upgrade_revisions_of_post( $post, $revisions ) {
1002	global $wpdb;
1003
1004	// Add post option exclusively.
1005	$lock   = "revision-upgrade-{$post->ID}";
1006	$now    = time();
1007	$result = $wpdb->query( $wpdb->prepare( "INSERT IGNORE INTO `$wpdb->options` (`option_name`, `option_value`, `autoload`) VALUES (%s, %s, 'off') /* LOCK */", $lock, $now ) );
1008
1009	if ( ! $result ) {
1010		// If we couldn't get a lock, see how old the previous lock is.
1011		$locked = get_option( $lock );
1012
1013		if ( ! $locked ) {
1014			/*
1015			 * Can't write to the lock, and can't read the lock.
1016			 * Something broken has happened.
1017			 */
1018			return false;
1019		}
1020
1021		if ( $locked > $now - HOUR_IN_SECONDS ) {
1022			// Lock is not too old: some other process may be upgrading this post. Bail.
1023			return false;
1024		}
1025
1026		// Lock is too old - update it (below) and continue.
1027	}
1028
1029	// If we could get a lock, re-"add" the option to fire all the correct filters.
1030	update_option( $lock, $now );
1031
1032	reset( $revisions );
1033	$add_last = true;
1034
1035	do {
1036		$this_revision = current( $revisions );
1037		$prev_revision = next( $revisions );
1038
1039		$this_revision_version = _wp_get_post_revision_version( $this_revision );
1040
1041		// Something terrible happened.
1042		if ( false === $this_revision_version ) {
1043			continue;
1044		}
1045
1046		/*
1047		 * 1 is the latest revision version, so we're already up to date.
1048		 * No need to add a copy of the post as latest revision.
1049		 */
1050		if ( 0 < $this_revision_version ) {
1051			$add_last = false;
1052			continue;
1053		}
1054
1055		// Always update the revision version.
1056		$update = array(
1057			'post_name' => preg_replace( '/^(\d+-(?:autosave|revision))[\d-]*$/', '$1-v1', $this_revision->post_name ),
1058		);
1059
1060		/*
1061		 * If this revision is the oldest revision of the post, i.e. no $prev_revision,
1062		 * the correct post_author is probably $post->post_author, but that's only a good guess.
1063		 * Update the revision version only and Leave the author as-is.
1064		 */
1065		if ( $prev_revision ) {
1066			$prev_revision_version = _wp_get_post_revision_version( $prev_revision );
1067
1068			// If the previous revision is already up to date, it no longer has the information we need :(
1069			if ( $prev_revision_version < 1 ) {
1070				$update['post_author'] = $prev_revision->post_author;
1071			}
1072		}
1073
1074		// Upgrade this revision.
1075		$result = $wpdb->update( $wpdb->posts, $update, array( 'ID' => $this_revision->ID ) );
1076
1077		if ( $result ) {
1078			wp_cache_delete( $this_revision->ID, 'posts' );
1079		}
1080	} while ( $prev_revision );
1081
1082	delete_option( $lock );
1083
1084	// Add a copy of the post as latest revision.
1085	if ( $add_last ) {
1086		wp_save_post_revision( $post->ID );
1087	}
1088
1089	return true;
1090}
1091
1092/**
1093 * Filters preview post meta retrieval to get values from the autosave.
1094 *
1095 * Filters revisioned meta keys only.
1096 *
1097 * @since 6.4.0
1098 *
1099 * @param mixed  $value     Meta value to filter.
1100 * @param int    $object_id Object ID.
1101 * @param string $meta_key  Meta key to filter a value for.
1102 * @param bool   $single    Whether to return a single value.
1103 * @return mixed Original meta value if the meta key isn't revisioned, the object doesn't exist,
1104 *               the post type is a revision or the post ID doesn't match the object ID.
1105 *               Otherwise, the revisioned meta value is returned for the preview.
1106 */
1107function _wp_preview_meta_filter( $value, $object_id, $meta_key, $single ) {
1108	$post = get_post();
1109
1110	if ( empty( $post )
1111		|| $post->ID !== $object_id
1112		|| ! in_array( $meta_key, wp_post_revision_meta_keys( $post->post_type ), true )
1113		|| 'revision' === $post->post_type
1114	) {
1115		return $value;
1116	}
1117
1118	$preview = wp_get_post_autosave( $post->ID );
1119
1120	if ( false === $preview ) {
1121		return $value;
1122	}
1123
1124	return get_post_meta( $preview->ID, $meta_key, $single );
1125}
1126