aboutsummaryrefslogtreecommitdiff
path: root/engine/lib/metadata.php
blob: d2f8d4cd45e77e81cd1864c9e3bc303da79bdcf8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
<?php
/**
 * Elgg metadata
 * Functions to manage entity metadata.
 *
 * @package Elgg.Core
 * @subpackage DataModel.Metadata
 */

/**
 * Convert a database row to a new ElggMetadata
 *
 * @param stdClass $row An object from the database
 *
 * @return stdClass|ElggMetadata
 * @access private
 */
function row_to_elggmetadata($row) {
	if (!($row instanceof stdClass)) {
		return $row;
	}

	return new ElggMetadata($row);
}

/**
 * Get a specific metadata object by its id.
 * If you want multiple metadata objects, use
 * {@link elgg_get_metadata()}.
 *
 * @param int $id The id of the metadata object being retrieved.
 *
 * @return ElggMetadata|false  FALSE if not found
 */
function elgg_get_metadata_from_id($id) {
	return elgg_get_metastring_based_object_from_id($id, 'metadata');
}

/**
 * Deletes metadata using its ID.
 *
 * @param int $id The metadata ID to delete.
 * @return bool
 */
function elgg_delete_metadata_by_id($id) {
	$metadata = elgg_get_metadata_from_id($id);
	if (!$metadata) {
		return false;
	}
	return $metadata->delete();
}

/**
 * Create a new metadata object, or update an existing one.
 *
 * Metadata can be an array by setting allow_multiple to TRUE, but it is an
 * indexed array with no control over the indexing.
 *
 * @param int    $entity_guid    The entity to attach the metadata to
 * @param string $name           Name of the metadata
 * @param string $value          Value of the metadata
 * @param string $value_type     'text', 'integer', or '' for automatic detection
 * @param int    $owner_guid     GUID of entity that owns the metadata
 * @param int    $access_id      Default is ACCESS_PRIVATE
 * @param bool   $allow_multiple Allow multiple values for one key. Default is FALSE
 *
 * @return int|false id of metadata or FALSE if failure
 */
function create_metadata($entity_guid, $name, $value, $value_type = '', $owner_guid = 0,
	$access_id = ACCESS_PRIVATE, $allow_multiple = false) {

	global $CONFIG;

	$entity_guid = (int)$entity_guid;
	// name and value are encoded in add_metastring()
	//$name = sanitise_string(trim($name));
	//$value = sanitise_string(trim($value));
	$value_type = detect_extender_valuetype($value, sanitise_string(trim($value_type)));
	$time = time();
	$owner_guid = (int)$owner_guid;
	$allow_multiple = (boolean)$allow_multiple;

	if (!isset($value)) {
		return FALSE;
	}

	if ($owner_guid == 0) {
		$owner_guid = elgg_get_logged_in_user_guid();
	}

	$access_id = (int)$access_id;

	$query = "SELECT * from {$CONFIG->dbprefix}metadata"
		. " WHERE entity_guid = $entity_guid and name_id=" . add_metastring($name) . " limit 1";

	$existing = get_data_row($query);
	if ($existing && !$allow_multiple) {
		$id = (int)$existing->id;
		$result = update_metadata($id, $name, $value, $value_type, $owner_guid, $access_id);

		if (!$result) {
			return false;
		}
	} else {
		// Support boolean types
		if (is_bool($value)) {
			$value = (int) $value;
		}

		// Add the metastrings
		$value_id = add_metastring($value);
		if (!$value_id) {
			return false;
		}

		$name_id = add_metastring($name);
		if (!$name_id) {
			return false;
		}

		// If ok then add it
		$query = "INSERT into {$CONFIG->dbprefix}metadata"
			. " (entity_guid, name_id, value_id, value_type, owner_guid, time_created, access_id)"
			. " VALUES ($entity_guid, '$name_id','$value_id','$value_type', $owner_guid, $time, $access_id)";

		$id = insert_data($query);

		if ($id !== false) {
			$obj = elgg_get_metadata_from_id($id);
			if (elgg_trigger_event('create', 'metadata', $obj)) {

				elgg_get_metadata_cache()->save($entity_guid, $name, $value, $allow_multiple);

				return $id;
			} else {
				elgg_delete_metadata_by_id($id);
			}
		}
	}

	return $id;
}

/**
 * Update a specific piece of metadata.
 *
 * @param int    $id         ID of the metadata to update
 * @param string $name       Metadata name
 * @param string $value      Metadata value
 * @param string $value_type Value type
 * @param int    $owner_guid Owner guid
 * @param int    $access_id  Access ID
 *
 * @return bool
 */
function update_metadata($id, $name, $value, $value_type, $owner_guid, $access_id) {
	global $CONFIG;

	$id = (int)$id;

	if (!$md = elgg_get_metadata_from_id($id)) {
		return false;
	}
	if (!$md->canEdit()) {
		return false;
	}

	// If memcached then we invalidate the cache for this entry
	static $metabyname_memcache;
	if ((!$metabyname_memcache) && (is_memcache_available())) {
		$metabyname_memcache = new ElggMemcache('metabyname_memcache');
	}

	if ($metabyname_memcache) {
		// @todo fix memcache (name_id is not a property of ElggMetadata)
		$metabyname_memcache->delete("{$md->entity_guid}:{$md->name_id}");
	}

	$value_type = detect_extender_valuetype($value, sanitise_string(trim($value_type)));

	$owner_guid = (int)$owner_guid;
	if ($owner_guid == 0) {
		$owner_guid = elgg_get_logged_in_user_guid();
	}

	$access_id = (int)$access_id;

	// Support boolean types (as integers)
	if (is_bool($value)) {
		$value = (int) $value;
	}

	// Add the metastring
	$value_id = add_metastring($value);
	if (!$value_id) {
		return false;
	}

	$name_id = add_metastring($name);
	if (!$name_id) {
		return false;
	}

	// If ok then add it
	$query = "UPDATE {$CONFIG->dbprefix}metadata"
		. " set name_id='$name_id', value_id='$value_id', value_type='$value_type', access_id=$access_id,"
		. " owner_guid=$owner_guid where id=$id";

	$result = update_data($query);
	if ($result !== false) {

		elgg_get_metadata_cache()->save($md->entity_guid, $name, $value);

		// @todo this event tells you the metadata has been updated, but does not
		// let you do anything about it. What is needed is a plugin hook before
		// the update that passes old and new values.
		$obj = elgg_get_metadata_from_id($id);
		elgg_trigger_event('update', 'metadata', $obj);
	}

	return $result;
}

/**
 * This function creates metadata from an associative array of "key => value" pairs.
 *
 * To achieve an array for a single key, pass in the same key multiple times with
 * allow_multiple set to TRUE. This creates an indexed array. It does not support
 * associative arrays and there is no guarantee on the ordering in the array.
 *
 * @param int    $entity_guid     The entity to attach the metadata to
 * @param array  $name_and_values Associative array - a value can be a string, number, bool
 * @param string $value_type      'text', 'integer', or '' for automatic detection
 * @param int    $owner_guid      GUID of entity that owns the metadata
 * @param int    $access_id       Default is ACCESS_PRIVATE
 * @param bool   $allow_multiple  Allow multiple values for one key. Default is FALSE
 *
 * @return bool
 */
function create_metadata_from_array($entity_guid, array $name_and_values, $value_type, $owner_guid,
$access_id = ACCESS_PRIVATE, $allow_multiple = false) {

	foreach ($name_and_values as $k => $v) {
		$result = create_metadata($entity_guid, $k, $v, $value_type, $owner_guid,
			$access_id, $allow_multiple);
		if (!$result) {
			return false;
		}
	}
	return true;
}

/**
 * Returns metadata.  Accepts all elgg_get_entities() options for entity
 * restraints.
 *
 * @see elgg_get_entities
 *
 * @warning 1.7's find_metadata() didn't support limits and returned all metadata.
 *          This function defaults to a limit of 25. There is probably not a reason
 *          for you to return all metadata unless you're exporting an entity,
 *          have other restraints in place, or are doing something horribly
 *          wrong in your code.
 *
 * @param array $options Array in format:
 *
 * metadata_names               => NULL|ARR metadata names
 * metadata_values              => NULL|ARR metadata values
 * metadata_ids                 => NULL|ARR metadata ids
 * metadata_case_sensitive      => BOOL Overall Case sensitive
 * metadata_owner_guids         => NULL|ARR guids for metadata owners
 * metadata_created_time_lower  => INT Lower limit for created time.
 * metadata_created_time_upper  => INT Upper limit for created time.
 * metadata_calculation         => STR Perform the MySQL function on the metadata values returned.
 *                                   The "metadata_calculation" option causes this function to
 *                                   return the result of performing a mathematical calculation on
 *                                   all metadata that match the query instead of returning
 *                                   ElggMetadata objects.
 *
 * @return ElggMetadata[]|mixed
 * @since 1.8.0
 */
function elgg_get_metadata(array $options = array()) {

	// @todo remove support for count shortcut - see #4393
	// support shortcut of 'count' => true for 'metadata_calculation' => 'count'
	if (isset($options['count']) && $options['count']) {
		$options['metadata_calculation'] = 'count';
		unset($options['count']);
	}

	$options['metastring_type'] = 'metadata';
	return elgg_get_metastring_based_objects($options);
}

/**
 * Deletes metadata based on $options.
 *
 * @warning Unlike elgg_get_metadata() this will not accept an empty options array!
 *          This requires at least one constraint: metadata_owner_guid(s),
 *          metadata_name(s), metadata_value(s), or guid(s) must be set.
 *
 * @param array $options An options array. {@see elgg_get_metadata()}
 * @return bool|null true on success, false on failure, null if no metadata to delete.
 * @since 1.8.0
 */
function elgg_delete_metadata(array $options) {
	if (!elgg_is_valid_options_for_batch_operation($options, 'metadata')) {
		return false;
	}
	$options['metastring_type'] = 'metadata';
	$result = elgg_batch_metastring_based_objects($options, 'elgg_batch_delete_callback', false);

	// This moved last in case an object's constructor sets metadata. Currently the batch
	// delete process has to create the entity to delete its metadata. See #5214
	elgg_get_metadata_cache()->invalidateByOptions('delete', $options);

	return $result;
}

/**
 * Disables metadata based on $options.
 *
 * @warning Unlike elgg_get_metadata() this will not accept an empty options array!
 *
 * @param array $options An options array. {@See elgg_get_metadata()}
 * @return bool|null true on success, false on failure, null if no metadata disabled.
 * @since 1.8.0
 */
function elgg_disable_metadata(array $options) {
	if (!elgg_is_valid_options_for_batch_operation($options, 'metadata')) {
		return false;
	}

	elgg_get_metadata_cache()->invalidateByOptions('disable', $options);

	$options['metastring_type'] = 'metadata';
	return elgg_batch_metastring_based_objects($options, 'elgg_batch_disable_callback', false);
}

/**
 * Enables metadata based on $options.
 *
 * @warning Unlike elgg_get_metadata() this will not accept an empty options array!
 *
 * @warning In order to enable metadata, you must first use
 * {@link access_show_hidden_entities()}.
 *
 * @param array $options An options array. {@See elgg_get_metadata()}
 * @return bool|null true on success, false on failure, null if no metadata enabled.
 * @since 1.8.0
 */
function elgg_enable_metadata(array $options) {
	if (!$options || !is_array($options)) {
		return false;
	}

	elgg_get_metadata_cache()->invalidateByOptions('enable', $options);

	$options['metastring_type'] = 'metadata';
	return elgg_batch_metastring_based_objects($options, 'elgg_batch_enable_callback');
}

/**
 * ElggEntities interfaces
 */

/**
 * Returns entities based upon metadata.  Also accepts all
 * options available to elgg_get_entities().  Supports
 * the singular option shortcut.
 *
 * @note Using metadata_names and metadata_values results in a
 * "names IN (...) AND values IN (...)" clause.  This is subtly
 * differently than default multiple metadata_name_value_pairs, which use
 * "(name = value) AND (name = value)" clauses.
 *
 * When in doubt, use name_value_pairs.
 *
 * To ask for entities that do not have a metadata value, use a custom
 * where clause like this:
 *
 * 	$options['wheres'][] = "NOT EXISTS (
 *			SELECT 1 FROM {$dbprefix}metadata md
 *			WHERE md.entity_guid = e.guid
 *				AND md.name_id = $name_metastring_id
 *				AND md.value_id = $value_metastring_id)";
 *
 * Note the metadata name and value has been denormalized in the above example.
 *
 * @see elgg_get_entities
 *
 * @param array $options Array in format:
 *
 * 	metadata_names => NULL|ARR metadata names
 *
 * 	metadata_values => NULL|ARR metadata values
 *
 * 	metadata_name_value_pairs => NULL|ARR (
 *                                         name => 'name',
 *                                         value => 'value',
 *                                         'operand' => '=',
 *                                         'case_sensitive' => TRUE
 *                                        )
 *                               Currently if multiple values are sent via
 *                               an array (value => array('value1', 'value2')
 *                               the pair's operand will be forced to "IN".
 *                               If passing "IN" as the operand and a string as the value, 
 *                               the value must be a properly quoted and escaped string.
 *
 * 	metadata_name_value_pairs_operator => NULL|STR The operator to use for combining
 *                                        (name = value) OPERATOR (name = value); default AND
 *
 * 	metadata_case_sensitive => BOOL Overall Case sensitive
 *
 *  order_by_metadata => NULL|ARR array(
 *                                      'name' => 'metadata_text1',
 *                                      'direction' => ASC|DESC,
 *                                      'as' => text|integer
 *                                     )
 *                                Also supports array('name' => 'metadata_text1')
 *
 *  metadata_owner_guids => NULL|ARR guids for metadata owners
 *
 * @return ElggEntity[]|mixed If count, int. If not count, array. false on errors.
 * @since 1.7.0
 */
function elgg_get_entities_from_metadata(array $options = array()) {
	$defaults = array(
		'metadata_names'                     => ELGG_ENTITIES_ANY_VALUE,
		'metadata_values'                    => ELGG_ENTITIES_ANY_VALUE,
		'metadata_name_value_pairs'          => ELGG_ENTITIES_ANY_VALUE,

		'metadata_name_value_pairs_operator' => 'AND',
		'metadata_case_sensitive'            => TRUE,
		'order_by_metadata'                  => array(),

		'metadata_owner_guids'               => ELGG_ENTITIES_ANY_VALUE,
	);

	$options = array_merge($defaults, $options);

	$singulars = array('metadata_name', 'metadata_value',
		'metadata_name_value_pair', 'metadata_owner_guid');

	$options = elgg_normalise_plural_options_array($options, $singulars);

	if (!$options = elgg_entities_get_metastrings_options('metadata', $options)) {
		return FALSE;
	}

	return elgg_get_entities($options);
}

/**
 * Returns metadata name and value SQL where for entities.
 * NB: $names and $values are not paired. Use $pairs for this.
 * Pairs default to '=' operand.
 *
 * This function is reused for annotations because the tables are
 * exactly the same.
 *
 * @param string     $e_table           Entities table name
 * @param string     $n_table           Normalized metastrings table name (Where entities,
 *                                    values, and names are joined. annotations / metadata)
 * @param array|null $names             Array of names
 * @param array|null $values            Array of values
 * @param array|null $pairs             Array of names / values / operands
 * @param string     $pair_operator     ("AND" or "OR") Operator to use to join the where clauses for pairs
 * @param bool       $case_sensitive    Case sensitive metadata names?
 * @param array|null $order_by_metadata Array of names / direction
 * @param array|null $owner_guids       Array of owner GUIDs
 *
 * @return false|array False on fail, array('joins', 'wheres')
 * @since 1.7.0
 * @access private
 */
function elgg_get_entity_metadata_where_sql($e_table, $n_table, $names = NULL, $values = NULL,
$pairs = NULL, $pair_operator = 'AND', $case_sensitive = TRUE, $order_by_metadata = NULL,
$owner_guids = NULL) {

	global $CONFIG;

	// short circuit if nothing requested
	// 0 is a valid (if not ill-conceived) metadata name.
	// 0 is also a valid metadata value for FALSE, NULL, or 0
	// 0 is also a valid(ish) owner_guid
	if ((!$names && $names !== 0)
		&& (!$values && $values !== 0)
		&& (!$pairs && $pairs !== 0)
		&& (!$owner_guids && $owner_guids !== 0)
		&& !$order_by_metadata) {
		return '';
	}

	// join counter for incremental joins.
	$i = 1;

	// binary forces byte-to-byte comparision of strings, making
	// it case- and diacritical-mark- sensitive.
	// only supported on values.
	$binary = ($case_sensitive) ? ' BINARY ' : '';

	$access = get_access_sql_suffix('n_table');

	$return = array (
		'joins' => array (),
		'wheres' => array(),
		'orders' => array()
	);

	// will always want to join these tables if pulling metastrings.
	$return['joins'][] = "JOIN {$CONFIG->dbprefix}{$n_table} n_table on
		{$e_table}.guid = n_table.entity_guid";

	$wheres = array();

	// get names wheres and joins
	$names_where = '';
	if ($names !== NULL) {
		if (!is_array($names)) {
			$names = array($names);
		}

		$sanitised_names = array();
		foreach ($names as $name) {
			// normalise to 0.
			if (!$name) {
				$name = '0';
			}
			$sanitised_names[] = '\'' . sanitise_string($name) . '\'';
		}

		if ($names_str = implode(',', $sanitised_names)) {
			$return['joins'][] = "JOIN {$CONFIG->dbprefix}metastrings msn on n_table.name_id = msn.id";
			$names_where = "(msn.string IN ($names_str))";
		}
	}

	// get values wheres and joins
	$values_where = '';
	if ($values !== NULL) {
		if (!is_array($values)) {
			$values = array($values);
		}

		$sanitised_values = array();
		foreach ($values as $value) {
			// normalize to 0
			if (!$value) {
				$value = 0;
			}
			$sanitised_values[] = '\'' . sanitise_string($value) . '\'';
		}

		if ($values_str = implode(',', $sanitised_values)) {
			$return['joins'][] = "JOIN {$CONFIG->dbprefix}metastrings msv on n_table.value_id = msv.id";
			$values_where = "({$binary}msv.string IN ($values_str))";
		}
	}

	if ($names_where && $values_where) {
		$wheres[] = "($names_where AND $values_where AND $access)";
	} elseif ($names_where) {
		$wheres[] = "($names_where AND $access)";
	} elseif ($values_where) {
		$wheres[] = "($values_where AND $access)";
	}

	// add pairs
	// pairs must be in arrays.
	if (is_array($pairs)) {
		// check if this is an array of pairs or just a single pair.
		if (isset($pairs['name']) || isset($pairs['value'])) {
			$pairs = array($pairs);
		}

		$pair_wheres = array();

		// @todo when the pairs are > 3 should probably split the query up to
		// denormalize the strings table.

		foreach ($pairs as $index => $pair) {
			// @todo move this elsewhere?
			// support shortcut 'n' => 'v' method.
			if (!is_array($pair)) {
				$pair = array(
					'name' => $index,
					'value' => $pair
				);
			}

			// must have at least a name and value
			if (!isset($pair['name']) || !isset($pair['value'])) {
				// @todo should probably return false.
				continue;
			}

			// case sensitivity can be specified per pair.
			// default to higher level setting.
			if (isset($pair['case_sensitive'])) {
				$pair_binary = ($pair['case_sensitive']) ? ' BINARY ' : '';
			} else {
				$pair_binary = $binary;
			}

			if (isset($pair['operand'])) {
				$operand = sanitise_string($pair['operand']);
			} else {
				$operand = ' = ';
			}

			// for comparing
			$trimmed_operand = trim(strtolower($operand));

			$access = get_access_sql_suffix("n_table{$i}");
			// if the value is an int, don't quote it because str '15' < str '5'
			// if the operand is IN don't quote it because quoting should be done already.
			if (is_numeric($pair['value'])) {
				$value = sanitise_string($pair['value']);
			} else if (is_bool($pair['value'])) {
				$value = (int) $pair['value'];
			} else if (is_array($pair['value'])) {
				$values_array = array();

				foreach ($pair['value'] as $pair_value) {
					if (is_numeric($pair_value)) {
						$values_array[] = sanitise_string($pair_value);
					} else {
						$values_array[] = "'" . sanitise_string($pair_value) . "'";
					}
				}

				if ($values_array) {
					$value = '(' . implode(', ', $values_array) . ')';
				}

				// @todo allow support for non IN operands with array of values.
				// will have to do more silly joins.
				$operand = 'IN';
			} else if ($trimmed_operand == 'in') {
				$value = "({$pair['value']})";
			} else {
				$value = "'" . sanitise_string($pair['value']) . "'";
			}

			$name = sanitise_string($pair['name']);

			// @todo The multiple joins are only needed when the operator is AND
			$return['joins'][] = "JOIN {$CONFIG->dbprefix}{$n_table} n_table{$i}
				on {$e_table}.guid = n_table{$i}.entity_guid";
			$return['joins'][] = "JOIN {$CONFIG->dbprefix}metastrings msn{$i}
				on n_table{$i}.name_id = msn{$i}.id";
			$return['joins'][] = "JOIN {$CONFIG->dbprefix}metastrings msv{$i}
				on n_table{$i}.value_id = msv{$i}.id";

			$pair_wheres[] = "(msn{$i}.string = '$name' AND {$pair_binary}msv{$i}.string
				$operand $value AND $access)";

			$i++;
		}

		if ($where = implode(" $pair_operator ", $pair_wheres)) {
			$wheres[] = "($where)";
		}
	}

	// add owner_guids
	if ($owner_guids) {
		if (is_array($owner_guids)) {
			$sanitised = array_map('sanitise_int', $owner_guids);
			$owner_str = implode(',', $sanitised);
		} else {
			$owner_str = sanitise_int($owner_guids);
		}

		$wheres[] = "(n_table.owner_guid IN ($owner_str))";
	}

	if ($where = implode(' AND ', $wheres)) {
		$return['wheres'][] = "($where)";
	}

	if (is_array($order_by_metadata)) {
		if ((count($order_by_metadata) > 0) && !isset($order_by_metadata[0])) {
			// singleton, so fix
			$order_by_metadata = array($order_by_metadata);
		}
		foreach ($order_by_metadata as $order_by) {
			if (is_array($order_by) && isset($order_by['name'])) {
				$name = sanitise_string($order_by['name']);
				if (isset($order_by['direction'])) {
					$direction = sanitise_string($order_by['direction']);
				} else {
					$direction = 'ASC';
				}
				$return['joins'][] = "JOIN {$CONFIG->dbprefix}{$n_table} n_table{$i}
					on {$e_table}.guid = n_table{$i}.entity_guid";
				$return['joins'][] = "JOIN {$CONFIG->dbprefix}metastrings msn{$i}
					on n_table{$i}.name_id = msn{$i}.id";
				$return['joins'][] = "JOIN {$CONFIG->dbprefix}metastrings msv{$i}
					on n_table{$i}.value_id = msv{$i}.id";

				$access = get_access_sql_suffix("n_table{$i}");

				$return['wheres'][] = "(msn{$i}.string = '$name' AND $access)";
				if (isset($order_by['as']) && $order_by['as'] == 'integer') {
					$return['orders'][] = "CAST(msv{$i}.string AS SIGNED) $direction";
				} else {
					$return['orders'][] = "msv{$i}.string $direction";
				}
				$i++;
			}
		}
	}

	return $return;
}

/**
 * Returns a list of entities filtered by provided metadata.
 *
 * @see elgg_get_entities_from_metadata
 *
 * @param array $options Options array
 *
 * @return array
 * @since 1.7.0
 */
function elgg_list_entities_from_metadata($options) {
	return elgg_list_entities($options, 'elgg_get_entities_from_metadata');
}

/**
 * Other functions
 */

/**
 * Handler called by trigger_plugin_hook on the "export" event.
 *
 * @param string $hook        export
 * @param string $entity_type all
 * @param mixed  $returnvalue Value returned from previous hook
 * @param mixed  $params      Params
 *
 * @return array
 * @access private
 *
 * @throws InvalidParameterException
 */
function export_metadata_plugin_hook($hook, $entity_type, $returnvalue, $params) {
	// Sanity check values
	if ((!is_array($params)) && (!isset($params['guid']))) {
		throw new InvalidParameterException(elgg_echo('InvalidParameterException:GUIDNotForExport'));
	}

	if (!is_array($returnvalue)) {
		throw new InvalidParameterException(elgg_echo('InvalidParameterException:NonArrayReturnValue'));
	}

	$result = elgg_get_metadata(array(
		'guid' => (int)$params['guid'],
		'limit' => 0,
	));

	if ($result) {
		/* @var ElggMetadata[] $result */
		foreach ($result as $r) {
			$returnvalue[] = $r->export();
		}
	}

	return $returnvalue;
}

/**
 * Takes in a comma-separated string and returns an array of tags
 * which have been trimmed
 *
 * @param string $string Comma-separated tag string
 *
 * @return array|false An array of strings, or false on failure
 */
function string_to_tag_array($string) {
	if (is_string($string)) {
		$ar = explode(",", $string);
		$ar = array_map('trim', $ar);
		$ar = array_filter($ar, 'is_not_null');
		$ar = array_map('strip_tags', $ar);
		return $ar;
	}
	return false;
}

/**
 * Takes a metadata array (which has all kinds of properties)
 * and turns it into a simple array of strings
 *
 * @param array $array Metadata array
 *
 * @return array Array of strings
 */
function metadata_array_to_values($array) {
	$valuearray = array();

	if (is_array($array)) {
		foreach ($array as $element) {
			$valuearray[] = $element->value;
		}
	}

	return $valuearray;
}

/**
 * Get the URL for this metadata
 *
 * By default this links to the export handler in the current view.
 *
 * @param int $id Metadata ID
 *
 * @return mixed
 */
function get_metadata_url($id) {
	$id = (int)$id;

	if ($extender = elgg_get_metadata_from_id($id)) {
		return get_extender_url($extender);
	}
	return false;
}

/**
 * Mark entities with a particular type and subtype as having access permissions
 * that can be changed independently from their parent entity
 *
 * @param string $type    The type - object, user, etc
 * @param string $subtype The subtype; all subtypes by default
 *
 * @return void
 */
function register_metadata_as_independent($type, $subtype = '*') {
	global $CONFIG;
	if (!isset($CONFIG->independents)) {
		$CONFIG->independents = array();
	}
	$CONFIG->independents[$type][$subtype] = true;
}

/**
 * Determines whether entities of a given type and subtype should not change
 * their metadata in line with their parent entity
 *
 * @param string $type    The type - object, user, etc
 * @param string $subtype The entity subtype
 *
 * @return bool
 */
function is_metadata_independent($type, $subtype) {
	global $CONFIG;
	if (empty($CONFIG->independents)) {
		return false;
	}
	if (!empty($CONFIG->independents[$type][$subtype])
		|| !empty($CONFIG->independents[$type]['*'])) {
			return true;
		}
	return false;
}

/**
 * When an entity is updated, resets the access ID on all of its child metadata
 *
 * @param string     $event       The name of the event
 * @param string     $object_type The type of object
 * @param ElggEntity $object      The entity itself
 *
 * @return true
 */
function metadata_update($event, $object_type, $object) {
	if ($object instanceof ElggEntity) {
		if (!is_metadata_independent($object->getType(), $object->getSubtype())) {
			$db_prefix = elgg_get_config('dbprefix');
			$access_id = (int) $object->access_id;
			$guid = (int) $object->getGUID();
			$query = "update {$db_prefix}metadata set access_id = {$access_id} where entity_guid = {$guid}";
			update_data($query);
		}
	}
	return true;
}

/**
 * Register a metadata url handler.
 *
 * @param string $extender_name The name, default 'all'.
 * @param string $function      The function name.
 *
 * @return bool
 */
function elgg_register_metadata_url_handler($extender_name, $function) {
	return elgg_register_extender_url_handler('metadata', $extender_name, $function);
}

/**
 * Get the global metadata cache instance
 *
 * @return ElggVolatileMetadataCache
 *
 * @access private
 */
function elgg_get_metadata_cache() {
	global $CONFIG;
	if (empty($CONFIG->local_metadata_cache)) {
		$CONFIG->local_metadata_cache = new ElggVolatileMetadataCache();
	}
	return $CONFIG->local_metadata_cache;
}

/**
 * Invalidate the metadata cache based on options passed to various *_metadata functions
 *
 * @param string $action  Action performed on metadata. "delete", "disable", or "enable"
 * @param array  $options Options passed to elgg_(delete|disable|enable)_metadata
 * @return void
 */
function elgg_invalidate_metadata_cache($action, array $options) {
	// remove as little as possible, optimizing for common cases
	$cache = elgg_get_metadata_cache();
	if (empty($options['guid'])) {
		// safest to clear everything unless we want to make this even more complex :(
		$cache->flush();
	} else {
		if (empty($options['metadata_name'])) {
			// safest to clear the whole entity
			$cache->clear($options['guid']);
		} else {
			switch ($action) {
				case 'delete':
					$cache->markEmpty($options['guid'], $options['metadata_name']);
					break;
				default:
					$cache->markUnknown($options['guid'], $options['metadata_name']);
			}
		}
	}
}

/** Register the hook */
elgg_register_plugin_hook_handler("export", "all", "export_metadata_plugin_hook", 2);

/** Call a function whenever an entity is updated **/
elgg_register_event_handler('update', 'all', 'metadata_update');

// unit testing
elgg_register_plugin_hook_handler('unit_test', 'system', 'metadata_test');

/**
 * Metadata unit test
 *
 * @param string $hook   unit_test
 * @param string $type   system
 * @param mixed  $value  Array of other tests
 * @param mixed  $params Params
 *
 * @return array
 * @access private
 */
function metadata_test($hook, $type, $value, $params) {
	global $CONFIG;
	$value[] = $CONFIG->path . 'engine/tests/api/metadata.php';
	$value[] = $CONFIG->path . 'engine/tests/api/metadata_cache.php';
	return $value;
}