aboutsummaryrefslogtreecommitdiff
path: root/engine/lib/entities.php
blob: 30bd2d89b58003b75791618d6733b6cded613920 (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
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
<?php
	/**
	 * Elgg entities.
	 * Functions to manage all elgg entities (sites, collections, objects and users).
	 * 
	 * @package Elgg
	 * @subpackage Core
	 * @license http://www.gnu.org/licenses/old-licenses/gpl-2.0.html GNU Public License version 2
	 * @author Marcus Povey <marcus@dushka.co.uk>
	 * @copyright Curverider Ltd 2008
	 * @link http://elgg.org/
	 */

	/// Cache objects in order to minimise database access.
	$ENTITY_CACHE = array();
	
	/// Cache subtype searches
	$SUBTYPE_CACHE = array();
	
	/**
	 * ElggEntity The elgg entity superclass
	 * This class holds methods for accessing the main entities table.
	 * 
	 * @author Marcus Povey <marcus@dushka.co.uk>
	 * @package Elgg
	 * @subpackage Core
	 */
	abstract class ElggEntity implements 
		Exportable, // Allow export of data
		Importable, // Allow import of data
		Loggable,	// Can events related to this object class be logged
		Iterator,	// Override foreach behaviour
		ArrayAccess // Override for array access
	{
		/** 
		 * The main attributes of an entity.
		 * Blank entries for all database fields should be created by the constructor.
		 * Subclasses should add to this in their constructors.
		 * Any field not appearing in this will be viewed as a 
		 */
		protected $attributes;

		/**
		 * If set, overrides the value of getURL()
		 */
		protected $url_override;
		
		/**
		 * Temporary cache for metadata, permitting meta data access before a guid has obtained.
		 */
		protected $temp_metadata;
				
		/**
		 * Temporary cache for annotations, permitting meta data access before a guid has obtained.
		 */
		protected $temp_annotations;
		
		/**
		 * Initialise the attributes array. 
		 * This is vital to distinguish between metadata and base parameters.
		 * 
		 * Place your base parameters here.
		 * 
		 * @return void
		 */
		protected function initialise_attributes()
		{
			initialise_entity_cache();

			// Create attributes array if not already created
			if (!is_array($this->attributes)) $this->attributes = array();
			if (!is_array($this->temp_metadata)) $this->temp_metadata = array();
			if (!is_array($this->temp_annotations)) $this->temp_annotations = array();
			
			$this->attributes['guid'] = "";
			$this->attributes['type'] = "";
			$this->attributes['subtype'] = "";
			$this->attributes['owner_guid'] = $_SESSION['guid'];
			$this->attributes['site_guid'] = 0;
			$this->attributes['access_id'] = 0;
			$this->attributes['time_created'] = "";
			$this->attributes['time_updated'] = "";
			
			// There now follows a bit of a hack
			/* Problem: To speed things up, some objects are split over several tables, this means that it requires
			 * n number of database reads to fully populate an entity. This causes problems for caching and create events
			 * since it is not possible to tell whether a subclassed entity is complete.
			 * Solution: We have two counters, one 'tables_split' which tells whatever is interested how many tables 
			 * are going to need to be searched in order to fully populate this object, and 'tables_loaded' which is how
			 * many have been loaded thus far.
			 * If the two are the same then this object is complete.
			 * 
			 * Use: isFullyLoaded() to check
			 */
			$this->attributes['tables_split'] = 1;
			$this->attributes['tables_loaded'] = 0;
		}
				
		/**
		 * Return the value of a given key.
		 * If $name is a key field (as defined in $this->attributes) that value is returned, otherwise it will
		 * then look to see if the value is in this object's metadata.
		 * 
		 * Q: Why are we not using __get overload here?
		 * A: Because overload operators cause problems during subclassing, so we put the code here and
		 * create overloads in subclasses. 
		 * 
		 * @param string $name
		 * @return mixed Returns the value of a given value, or null.
		 */
		public function get($name)
		{
			// See if its in our base attribute
			if (isset($this->attributes[$name])) {
				return $this->attributes[$name];
			}
			
			// No, so see if its in the meta data for this entity
			$meta = $this->getMetaData($name);
			if ($meta)
				return $meta;
			
			// Can't find it, so return null
			return null;
		}

		/**
		 * Set the value of a given key, replacing it if necessary.
		 * If $name is a base attribute (as defined in $this->attributes) that value is set, otherwise it will
		 * set the appropriate item of metadata.
		 * 
		 * Note: It is important that your class populates $this->attributes with keys for all base attributes, anything
		 * not in their gets set as METADATA.
		 * 
		 * Q: Why are we not using __set overload here?
		 * A: Because overload operators cause problems during subclassing, so we put the code here and
		 * create overloads in subclasses.
		 * 
		 * @param string $name
		 * @param mixed $value  
		 */
		public function set($name, $value)
		{
			if (array_key_exists($name, $this->attributes))
			{
				// Check that we're not trying to change the guid! 
				if ((array_key_exists('guid', $this->attributes)) && ($name=='guid'))
					return false;
					
				$this->attributes[$name] = $value;
			}
			else 
				return $this->setMetaData($name, $value);
		
			return true;
		}
			
		/**
		 * Get a given piece of metadata.
		 * 
		 * @param string $name
		 */
		public function getMetaData($name)
		{
			if ((int) ($this->guid) > 0) {
				$md = get_metadata_byname($this->getGUID(), $name);
			} else {
				if (isset($this->temp_metadata[$name]))
					return $this->temp_metadata[$name];
			}

			if ($md && !is_array($md)) {
				return $md->value;
			} else if ($md && is_array($md)) {
				return metadata_array_to_values($md);
			}
				
			return null;
		}
		
		/**
		 * Set a piece of metadata.
		 * 
		 * @param string $name
		 * @param mixed $value
		 * @param string $value_type
		 * @param bool $multiple
		 * @return bool
		 */
		public function setMetaData($name, $value, $value_type = "", $multiple = false)
		{
			if (is_array($value))
			{
				remove_metadata($this->getGUID(), $name);
				$multiple = true;
				foreach ($value as $v) {
					if ((int) $this->guid > 0) {
						if (!create_metadata($this->getGUID(), $name, $v, $value_type, $this->getOwner(), $this->getAccessID(), $multiple)) return false;
					} else {
						$this->temp_metadata[$name] = $value;
					}
				}
					
				return true;
			}
			else
			{
				if ((int) $this->guid > 0) {
					return create_metadata($this->getGUID(), $name, $value, $value_type, $this->getOwner(), $this->getAccessID());
				} else {
					$this->temp_metadata[$name] = $value;
					return true;
				}
			}
		}
		
		/**
		 * Clear metadata.
		 */
		public function clearMetaData($name = "")
		{
			if (empty($name)) {
				return clear_metadata($this->getGUID());
			} else {
				return remove_metadata($this->getGUID(),$name);
			}
		}
		
		/**
		 * Remove all entities associated with this entity
		 *
		 * @return true
		 */
		public function clearRelationships() {
			remove_entity_relationships($this->getGUID());
			remove_entity_relationships($this->getGUID(),"",true);
			return true;
		}
		
		/**
		 * Adds an annotation to an entity. By default, the type is detected automatically; however, 
		 * it can also be set. Note that by default, annotations are private.
		 * 
		 * @param string $name
		 * @param mixed $value
		 * @param int $access_id
		 * @param int $owner_id
		 * @param string $vartype
		 */
		function annotate($name, $value, $access_id = 0, $owner_id = 0, $vartype = "") 
		{ 
			if ((int) $this->guid > 0) {
				return create_annotation($this->getGUID(), $name, $value, $vartype, $owner_id, $access_id);
			} else {
				$this->temp_annotations[$name] = $value;
			}
			return true;
		}
		
		/**
		 * Get the annotations for an entity.
		 *
		 * @param string $name
		 * @param int $limit
		 * @param int $offset
		 * @param string $order
		 */
		function getAnnotations($name, $limit = 50, $offset = 0, $order="asc") 
		{ 
			if ((int) ($this->guid) > 0) {
				return get_annotations($this->getGUID(), "", "", $name, "", 0, $limit, $offset, $order);
			} else {
				return $this->temp_annotations[$name];
			}
		}
		
		/**
		 * Remove all annotations or all annotations for this entity.
		 *
		 * @param string $name
		 */
		function clearAnnotations($name = "")
		{
			return clear_annotations($this->getGUID(), $name);
		}
		
		/**
		 * Return the annotations for the entity.
		 *
		 * @param string $name The type of annotation.
		 */
		function countAnnotations($name) 
		{ 
			return count_annotations($this->getGUID(), "","",$name);
		}

		/**
		 * Get the average of an integer type annotation.
		 *
		 * @param string $name
		 */
		function getAnnotationsAvg($name) 
		{
			return get_annotations_avg($this->getGUID(), "","",$name);
		}
		
		/**
		 * Get the sum of integer type annotations of a given name.
		 *
		 * @param string $name
		 */
		function getAnnotationsSum($name) 
		{
			return get_annotations_sum($this->getGUID(), "","",$name);
		}
		
		/**
		 * Get the minimum of integer type annotations of given name.
		 *
		 * @param string $name
		 */
		function getAnnotationsMin($name)
		{
			return get_annotations_min($this->getGUID(), "","",$name);
		}
		
		/**
		 * Get the maximum of integer type annotations of a given name.
		 *
		 * @param string $name
		 */
		function getAnnotationsMax($name)
		{
			return get_annotations_max($this->getGUID(), "","",$name);
		}
		
		/**
		 * Gets an array of entities from a specific relationship type
		 *
		 * @param string $relationship Relationship type (eg "friends")
		 * @param true|false $inverse Is this an inverse relationship?
		 * @param int $limit Number of elements to return
		 * @param int $offset Indexing offset
		 * @return array|false An array of entities or false on failure
		 */		
		function getEntitiesFromRelationship($relationship, $inverse = false, $limit = 50, $offset = 0) {
			return get_entities_from_relationship($relationship,$this->getGUID(),$inverse,"","","","time_created desc",$limit,$offset);			
		}
		
		/**
		 * Gets the number of of entities from a specific relationship type
		 *
		 * @param string $relationship Relationship type (eg "friends")
		 * @return int|false The number of entities or false on failure
		 */		
		function countEntitiesFromRelationship($relationship) {
			return get_entities_from_relationship($relationship,$this->getGUID(),false,"","","","time_created desc",null,null,true);			
		}
		
		/**
		 * Determines whether or not the specified user (by default the current one) can edit the entity 
		 *
		 * @param int $user_guid The user GUID, optionally (defaults to the currently logged in user)
		 * @return true|false
		 */
		function canEdit($user_guid = 0) {
			return can_edit_entity($this->getGUID(),$user_guid);
		}
		
		/**
		 * Determines whether or not the specified user (by default the current one) can edit metadata on the entity 
		 *
		 * @param int $user_guid The user GUID, optionally (defaults to the currently logged in user)
		 * @return true|false
		 */
		function canEditMetadata($user_guid = 0) {
			return can_edit_entity_metadata($this->getGUID(), $user_guid);
		}
		
		/**
		 * Obtain this entity's access ID
		 *
		 * @return int The access ID
		 */
		public function getAccessID() { return $this->get('access_id'); }
		
		/**
		 * Obtain this entity's GUID
		 *
		 * @return int GUID
		 */
		public function getGUID() { return $this->get('guid'); }
		
		/**
		 * Get the owner of this entity
		 *
		 * @return int The owner GUID
		 */
		public function getOwner() { return $this->get('owner_guid'); }
		
		/**
		 * Returns the actual entity of the user who owns this entity, if any
		 *
		 * @return ElggEntity The owning user
		 */
		public function getOwnerEntity() { return get_entity($this->get('owner_guid')); }
		
		/**
		 * Gets the type of entity this is
		 *
		 * @return string Entity type
		 */
		public function getType() { return $this->get('type'); }
		
		/**
		 * Returns the subtype of this entity
		 *
		 * @return string The entity subtype
		 */
		public function getSubtype() {
			if (!((int) $this->guid > 0)) return $this->get('subtype'); // If this object hasn't been saved, then return the subtype string.
			
			return get_subtype_from_id($this->get('subtype')); 
		}
		
		/**
		 * Gets the UNIX epoch time that this entity was created
		 *
		 * @return int UNIX epoch time
		 */
		public function getTimeCreated() { return $this->get('time_created'); }
		
		/**
		 * Gets the UNIX epoch time that this entity was last updated
		 *
		 * @return int UNIX epoch time
		 */
		public function getTimeUpdated() { return $this->get('time_updated'); }
		
		/**
		 * Gets the display URL for this entity
		 *
		 * @return string The URL
		 */
		public function getURL() {
			if (!empty($this->url_override)) return $this->url_override;
			return get_entity_url($this->getGUID()); 
		}
		
		/**
		 * Overrides the URL returned by getURL
		 *
		 * @param string $url The new item URL
		 * @return string The URL
		 */
		public function setURL($url) {
			$this->url_override = $url;
			return $url;
		}
		
		/**
		 * Tests to see whether the object has been fully loaded.
		 * 
		 * @return bool
		 */
		public function isFullyLoaded() { return ! ($this->attributes['tables_loaded'] < $this->attributes['tables_split']); }
		
		/**
		 * Save generic attributes to the entities table.
		 */
		public function save()
		{
			$guid = (int) $this->guid;
			if ($guid > 0)
			{ 
				cache_entity($this);

				return update_entity(
					$this->get('guid'),
					$this->get('owner_guid'),
					$this->get('access_id')
				);
			}
			else
			{ 
				$this->attributes['guid'] = create_entity($this->attributes['type'], $this->attributes['subtype'], $this->attributes['owner_guid'], $this->attributes['access_id']); // Create a new entity (nb: using attribute array directly 'cos set function does something special!)
				if (!$this->attributes['guid']) throw new IOException(elgg_echo('IOException:BaseEntitySaveFailed')); 
				
				// Save any unsaved metadata
				if (sizeof($this->temp_metadata) > 0) {
					foreach($this->temp_metadata as $name => $value) {
						$this->$name = $value;
						unset($this->temp_metadata[$name]);
					}
				}
				
				// Cache object handle
				if ($this->attributes['guid']) cache_entity($this); 
				
				return $this->attributes['guid'];
			}
		}
		
		/**
		 * Load the basic entity information and populate base attributes array.
		 * 
		 * @param int $guid 
		 */
		protected function load($guid)
		{		
			$row = get_entity_as_row($guid); 
		
			if ($row)
			{
				// Create the array if necessary - all subclasses should test before creating
				if (!is_array($this->attributes)) $this->attributes = array();
				
				// Now put these into the attributes array as core values
				$objarray = (array) $row;
				foreach($objarray as $key => $value) 
					$this->attributes[$key] = $value;
				
				// Increment the portion counter
				if (!$this->isFullyLoaded()) $this->attributes['tables_loaded'] ++;
				
				// Cache object handle
				if ($this->attributes['guid']) cache_entity($this); 
					
				return true;
			}
			
			return false;
		}
		
		/**
		 * Disable this entity.
		 */
		public function disable()
		{
			return disable_entity($this->get('guid'));
		}
		
		/**
		 * Delete this entity.
		 */
		public function delete() 
		{ 
			$res = delete_entity($this->get('guid'));
			return $res;
		}

		// EXPORTABLE INTERFACE ////////////////////////////////////////////////////////////
		
		/**
		 * Export this class into a stdClass containing all necessary fields.
		 * Override if you wish to return more information than can be found in $this->attributes (shouldn't happen) 
		 * 
		 * @return stdClass
		 */
		public function export() 
		{ 
			$tmp = array();
			
			// Generate uuid
			$uuid = guid_to_uuid($this->getGUID());
			
			// Create entity 
			$odd = new ODDEntity(
				$uuid,
				$this->attributes['type'], 
				get_subtype_from_id($this->attributes['subtype'])
			);
			
			$tmp[] = $odd;
			
			// Now add its attributes
			foreach ($this->attributes as $k => $v)
			{
				$meta = NULL;
				
				switch ($k)
				{
					case 'guid' : 			// Dont use guid
					case 'subtype' :		// The subtype
					case 'type' : 			// Don't use type
					case 'access_id' : 		// Don't use access - if can export then its public for you, then importer decides what access to give this object.
					case 'time_updated' : 	// Don't use date in export

					case 'tables_split' :	// We don't want to export the internal counter variables.
					case 'tables_loaded' :  // Or this one
						
					case 'enabled' :		// Useless to an importer
						
					case 'email' :
					case 'password' : 		// Definitely don't want these two
					break;
					
					case 'time_created' :	// Created = published
						$odd->setAttribute('published', date("r", $v));
					break;

					case 'owner_guid' :			// Convert owner guid to uuid, this will be stored in metadata
						 $k = 'owner_uuid';
						 $v = guid_to_uuid($v);
						 $meta = new ODDMetaData($uuid . "attr/$k/", $uuid, $k, $v);
					break; 	
					
					default : 
						$meta = new ODDMetaData($uuid . "attr/$k/", $uuid, $k, $v);
				}
				
				// set the time of any metadata created
				if ($meta)
				{
					$meta->setAttribute('published', date("r",$this->time_created));
					$tmp[] = $meta;
				}
			}
			
			// Now we do something a bit special.
			/*
			 * This provides a rendered view of the entity to foreign sites.
			 */
			
			elgg_set_viewtype('default');
			$view = elgg_view_entity($this, 'default');
			elgg_set_viewtype();
					
			$tmp[] = new ODDMetaData($uuid . "volatile/renderedentity/", $uuid, 'renderedentity', $view , 'volatile');
			
			
			return $tmp;
		}
		
		// IMPORTABLE INTERFACE ////////////////////////////////////////////////////////////
		
		/**
		 * Import data from an parsed xml data array.
		 * 
		 * @param array $data
		 * @param int $version 
		 */
		public function import(ODD $data)
		{
			if (!($data instanceof ODDEntity))
				throw new InvalidParameterException(elgg_echo('InvalidParameterException:UnexpectedODDClass')); 
			
			// Set type and subtype
			$this->attributes['type'] = $data->getAttribute('class');
			$this->attributes['subtype'] = $data->getAttribute('subclass');
			
			// Set owner
			$this->attributes['owner_guid'] = $_SESSION['id']; // Import as belonging to importer.
			
			// Set time
			$this->attributes['time_created'] = strtotime($data->getAttribute('published'));
			$this->attributes['time_updated'] = time();
			
			return true;
		}
		
		// SYSTEM LOG INTERFACE ////////////////////////////////////////////////////////////
		
		/**
		 * Return an identification for the object for storage in the system log. 
		 * This id must be an integer.
		 * 
		 * @return int 
		 */
		public function getSystemLogID() { return $this->getGUID();	}
		
		/**
		 * Return the class name of the object.
		 */
		public function getClassName() { return get_class($this); }
		
		/**
		 * For a given ID, return the object associated with it.
		 * This is used by the river functionality primarily.
		 * This is useful for checking access permissions etc on objects.
		 */
		public function getObjectFromID($id) { return get_entity($id); }
		
		/**
		 * Return the GUID of the owner of this object.
		 */
		public function getObjectOwnerGUID() { return $this->owner_guid; }

		// ITERATOR INTERFACE //////////////////////////////////////////////////////////////
		/*
		 * This lets an entity's attributes be displayed using foreach as a normal array.
		 * Example: http://www.sitepoint.com/print/php5-standard-library
		 */
		
		private $valid = FALSE; 
		
   		function rewind() 
   		{ 
   			$this->valid = (FALSE !== reset($this->attributes));  
   		}
   
   		function current() 
   		{ 
   			return current($this->attributes); 
   		}
		
   		function key() 
   		{ 
   			return key($this->attributes); 
   		}
		
   		function next() 
   		{
   			$this->valid = (FALSE !== next($this->attributes));  
   		}
   		
   		function valid() 
   		{ 
   			return $this->valid;  
   		}
	
   		// ARRAY ACCESS INTERFACE //////////////////////////////////////////////////////////
		/*
		 * This lets an entity's attributes be accessed like an associative array.
		 * Example: http://www.sitepoint.com/print/php5-standard-library
		 */

		function offsetSet($key, $value)
		{
   			if ( array_key_exists($key, $this->attributes) ) {
     			$this->attributes[$key] = $value;
   			}
 		} 
 		
 		function offsetGet($key) 
 		{
   			if ( array_key_exists($key, $this->attributes) ) {
     			return $this->attributes[$key];
   			}
 		} 
 		
 		function offsetUnset($key) 
 		{
   			if ( array_key_exists($key, $this->attributes) ) {
     			$this->attributes[$key] = ""; // Full unsetting is dangerious for our objects
   			}
 		} 
 		
 		function offsetExists($offset) 
 		{
   			return array_key_exists($offset, $this->attributes);
 		} 
	}

	/**
	 * Initialise the entity cache.
	 */
	function initialise_entity_cache()
	{
		global $ENTITY_CACHE;
		
		if (!is_array($ENTITY_CACHE))
			$ENTITY_CACHE = array();
	}
	
	/**
	 * Invalidate this class' entry in the cache.
	 * 
	 * @param int $guid The guid
	 */
	function invalidate_cache_for_entity($guid)
	{
		global $ENTITY_CACHE;
		
		$guid = (int)$guid;
			
		unset($ENTITY_CACHE[$guid]);
				
	}
	
	/**
	 * Cache an entity.
	 * 
	 * @param ElggEntity $entity Entity to cache
	 */
	function cache_entity(ElggEntity $entity)
	{
		global $ENTITY_CACHE;
		
		$ENTITY_CACHE[$entity->guid] = $entity;
	}
	
	/**
	 * Retrieve a entity from the cache.
	 * 
	 * @param int $guid The guid
	 */
	function retrieve_cached_entity($guid)
	{
		global $ENTITY_CACHE;
		
		$guid = (int)$guid;
			
		if (isset($ENTITY_CACHE[$guid])) 
			if ($ENTITY_CACHE[$guid]->isFullyLoaded()) return $ENTITY_CACHE[$guid];
				
		return false;
	}
	
	/**
	 * As retrieve_cached_entity, but returns the result as a stdClass (compatible with load functions that
	 * expect a database row.)
	 * 
	 * @param int $guid The guid
	 */
	function retrieve_cached_entity_row($guid)
	{
		$obj = retrieve_cached_entity($guid);
		if ($obj)
		{
			$tmp = new stdClass;
			
			foreach ($obj as $k => $v)
				$tmp->$k = $v;
				
			return $tmp;
		}

		return false;
	}
	
	/**
	 * Return the integer ID for a given subtype, or false.
	 * 
	 * TODO: Move to a nicer place?
	 * 
	 * @param string $type
	 * @param string $subtype
	 */
	function get_subtype_id($type, $subtype)
	{
		global $CONFIG, $SUBTYPE_CACHE;
		
		$type = sanitise_string($type);
		$subtype = sanitise_string($subtype);
	
		if ($subtype=="") return $subtype;
		
		// Todo: cache here? Or is looping less efficient that going to the db each time?
		
		$result = get_data_row("SELECT * from {$CONFIG->dbprefix}entity_subtypes where type='$type' and subtype='$subtype'");

		if ($result) {
			$SUBTYPE_CACHE[$result->id] = $result;
			return $result->id;
		}
		
		return 0;
	}
	
	/**
	 * For a given subtype ID, return its identifier text.
	 *  
	 * TODO: Move to a nicer place?
	 * 
	 * @param int $subtype_id
	 */
	function get_subtype_from_id($subtype_id)
	{
		global $CONFIG, $SUBTYPE_CACHE;
		
		$subtype_id = (int)$subtype_id;
		
		if (!$subtype_id) return false;
		
		if (isset($SUBTYPE_CACHE[$subtype_id]))
			return $SUBTYPE_CACHE[$subtype_id]->subtype;
		
		$result = get_data_row("SELECT * from {$CONFIG->dbprefix}entity_subtypes where id=$subtype_id");
		if ($result) {
			$SUBTYPE_CACHE[$subtype_id] = $result;
			return $result->subtype;
		}
		
		return false;
	}
	
	/**
	 * This function tests to see if a subtype has a registered class handler.
	 * 
	 * @param string $type The type
	 * @param string $subtype The subtype
	 * @return a class name or null
	 */
	function get_subtype_class($type, $subtype)
	{
		global $CONFIG, $SUBTYPE_CACHE;
		
		$type = sanitise_string($type);
		$subtype = sanitise_string($subtype);
		
		// Todo: cache here? Or is looping less efficient that going to the db each time?
		
		$result = get_data_row("SELECT * from {$CONFIG->dbprefix}entity_subtypes where type='$type' and subtype='$subtype'");
		if ($result) {
			$SUBTYPE_CACHE[$result->id] = $result;
			return $result->class;
		}
		
		return NULL;
	}
	
	/**
	 * This function tests to see if a subtype has a registered class handler by its id.
	 * 
	 * @param int $subtype_id The subtype
	 * @return a class name or null
	 */
	function get_subtype_class_from_id($subtype_id)
	{
		global $CONFIG, $SUBTYPE_CACHE;
		
		$subtype_id = (int)$subtype_id;
		
		if (!$subtype_id) return false;
		
		if (isset($SUBTYPE_CACHE[$subtype_id]))
			return $SUBTYPE_CACHE[$subtype_id]->class;
		
		$result = get_data_row("SELECT * from {$CONFIG->dbprefix}entity_subtypes where id=$subtype_id");
		if ($result) {
			$SUBTYPE_CACHE[$subtype_id] = $result;
			return $result->class;
		}
		
		return NULL;
	}
	
	/**
	 * This function will register a new subtype, returning its ID as required.
	 * 
	 * @param string $type The type you're subtyping
	 * @param string $subtype The subtype label
	 * @param string $class Optional class handler (if you don't want it handled by the generic elgg handler for the type)
	 */
	function add_subtype($type, $subtype, $class = "")
	{
		global $CONFIG;
		$type = sanitise_string($type);
		$subtype = sanitise_string($subtype);
		$class = sanitise_string($class);
	
		// Short circuit if no subtype is given
		if ($subtype == "")
			return 0;

		$id = get_subtype_id($type, $subtype);
	
		if ($id==0)
			return insert_data("insert into {$CONFIG->dbprefix}entity_subtypes (type, subtype, class) values ('$type','$subtype','$class')");
		
		return $id;
	}
	
	/**
	 * Update an existing entity.
	 *
	 * @param int $guid
	 * @param int $owner_guid
	 * @param int $access_id
	 */
	function update_entity($guid, $owner_guid,  $access_id)
	{
		global $CONFIG, $ENTITY_CACHE;
		
		$guid = (int)$guid;
		$owner_guid = (int)$owner_guid;
		$access_id = (int)$access_id;
		$time = time();

		$entity = get_entity($guid);
		
		if ($entity->canEdit()) {
			
			if (trigger_elgg_event('update',$entity->type,$entity)) {
				$ret = update_data("UPDATE {$CONFIG->dbprefix}entities set owner_guid='$owner_guid', access_id='$access_id', time_updated='$time' WHERE guid=$guid");
				
				// Handle cases where there was no error BUT no rows were updated!
				if ($ret===false)
					return false;

				return true;
			}
			
		}
	}
	
	/**
	 * Create a new entity of a given type.
	 * 
	 * @param string $type The type of the entity (site, user, object).
	 * @param string $subtype The subtype of the entity.
	 * @param int $owner_guid The GUID of the object's owner.
	 * @param int $access_id The access control group to create the entity with.
	 * @param int $site_guid The site to add this entity to. Leave as 0 (default) for the current site.
	 * @return mixed The new entity's GUID, or false on failure
	 */
	function create_entity($type, $subtype, $owner_guid, $access_id, $site_guid = 0)
	{
		global $CONFIG;
	
		$type = sanitise_string($type);
		$subtype = add_subtype($type, $subtype);
		$owner_guid = (int)$owner_guid; 
		$access_id = (int)$access_id;
		$time = time();
		if ($site_guid == 0)
			$site_guid = $CONFIG->site_guid;
		$site_guid = (int) $site_guid;
					
		if ($type=="") throw new InvalidParameterException(elgg_echo('InvalidParameterException:EntityTypeNotSet'));

		return insert_data("INSERT into {$CONFIG->dbprefix}entities (type, subtype, owner_guid, site_guid, access_id, time_created, time_updated) values ('$type',$subtype, $owner_guid, $site_guid, $access_id, $time, $time)"); 
	}
	
	/**
	 * Retrieve the entity details for a specific GUID, returning it as a stdClass db row.
	 * 
	 * You will only get an object if a) it exists, b) you have access to it.
	 *
	 * @param int $guid The GUID of the object to extract
	 */
	function get_entity_as_row($guid)
	{
		global $CONFIG;
		
		$guid = (int) $guid;
		
		$row = retrieve_cached_entity_row($guid);
		if ($row)
		{
			// We have already cached this object, so retrieve its value from the cache
			if (isset($CONFIG->debug) && $CONFIG->debug)
				error_log("** Retrieving GUID:$guid from cache");

			return $row;
		}
		else
		{	
			// Object not cached, load it.
			if (isset($CONFIG->debug) && $CONFIG->debug == true)
				error_log("** GUID:$guid loaded from DB");
			
			$access = get_access_sql_suffix();
		
			return get_data_row("SELECT * from {$CONFIG->dbprefix}entities where guid=$guid and $access");
		}
	}
	
	/**
	 * Create an Elgg* object from a given entity row. 
	 */
	function entity_row_to_elggstar($row)
	{
		if (!($row instanceof stdClass))
			return $row;
		// See if there are any registered subtype handler classes for this type and subtype

		$classname = get_subtype_class_from_id($row->subtype);
		if ($classname!="")
		{
			if (class_exists($classname))
			{
				$tmp = new $classname($row);
				
				if (!($tmp instanceof ElggEntity))
					throw new ClassException(sprintf(elgg_echo('ClassException:ClassnameNotClass'), $classname, get_class()));
	
				return $tmp;
			}
			else
				error_log(sprintf(elgg_echo('ClassNotFoundException:MissingClass'), $classname));
		}
		else
		{
			switch ($row->type)
			{
				case 'object' : 
					return new ElggObject($row);
				case 'user' : 
					return new ElggUser($row);
				case 'group' : 
					return new ElggGroup($row); 
				case 'site' : 
					return new ElggSite($row); 
				default: throw new InstallationException(sprintf(elgg_echo('InstallationException:TypeNotSupported'), $row->type));
			}
		}
		
		return false;
	}
	
	/**
	 * Return the entity for a given guid as the correct object.
	 * @param int $guid The GUID of the entity
	 * @return a child of ElggEntity appropriate for the type.
	 */
	function get_entity($guid)
	{
		return entity_row_to_elggstar(get_entity_as_row($guid));
	}
	
	/**
	 * Return entities matching a given query, or the number thereof
	 * 
	 * @param string $type The type of entity (eg "user", "object" etc)
	 * @param string $subtype The arbitrary subtype of the entity
	 * @param int $owner_guid The GUID of the owning user
	 * @param string $order_by The field to order by; by default, time_created desc
	 * @param int $limit The number of entities to return; 10 by default
	 * @param int $offset The indexing offset, 0 by default
	 * @param boolean $count Set to true to get a count rather than the entities themselves (limits and offsets don't apply in this context). Defaults to false.
	 * @param int $site_guid The site to get entities for. Leave as 0 (default) for the current site; -1 for all sites. 
	 */
	function get_entities($type = "", $subtype = "", $owner_guid = 0, $order_by = "", $limit = 10, $offset = 0, $count = false, $site_guid = 0)
	{
		global $CONFIG;
		
		if ($subtype === false || $subtype === null || $subtype === 0)
			return false;
		
		$type = sanitise_string($type);
		$subtype = get_subtype_id($type, $subtype);
		
		if ($order_by == "") $order_by = "time_created desc";
		$order_by = sanitise_string($order_by);
		$limit = (int)$limit;
		$offset = (int)$offset;
		$site_guid = (int) $site_guid;
		if ($site_guid == 0)
			$site_guid = $CONFIG->site_guid;
				
		$where = array();
		
		if ($type != "")
			$where[] = "type='$type'";
		if ($subtype!=="")
			$where[] = "subtype=$subtype";
		if ($owner_guid != "") {
			if (!is_array($owner_guid)) {
				$owner_guid = (int) $owner_guid;
				$where[] = "owner_guid = '$owner_guid'";
			} else if (sizeof($owner_guid) > 0) {
				// Cast every element to the owner_guid array to int
				$owner_guid = array_map("sanitise_int", $owner_guid);
				$owner_guid = implode(",",$owner_guid);
				$where[] = "owner_guid in ({$owner_guid})";
			}
		}
		if ($site_guid > 0)
			$where[] = "site_guid = {$site_guid}";

		if (!$count) {
			$query = "SELECT * from {$CONFIG->dbprefix}entities where ";
		} else {
			$query = "select count(guid) as total from {$CONFIG->dbprefix}entities where ";
		}
		foreach ($where as $w)
			$query .= " $w and ";
		$query .= get_access_sql_suffix(); // Add access controls
		if (!$count) {
			$query .= " order by $order_by";
			if ($limit) $query .= " limit $offset, $limit"; // Add order and limit

			$dt = get_data($query, "entity_row_to_elggstar");
			return $dt;
		} else {
			$total = get_data_row($query);
			return $total->total;
		}
	}
	
	/**
	 * Returns a viewable list of entities
	 *
	 * @see elgg_view_entity_list
	 * 
	 * @param string $type The type of entity (eg "user", "object" etc)
	 * @param string $subtype The arbitrary subtype of the entity
	 * @param int $owner_guid The GUID of the owning user
	 * @param int $limit The number of entities to display per page (default: 10)
	 * @param true|false $fullview Whether or not to display the full view (default: true)
	 * @return string A viewable list of entities
	 */
	function list_entities($type= "", $subtype = "", $owner_guid = 0, $limit = 10, $fullview = true) {
		
		$offset = (int) get_input('offset');
		$count = get_entities($type, $subtype, $owner_guid, "", $limit, $offset, true);
		$entities = get_entities($type, $subtype, $owner_guid, "", $limit, $offset);

		return elgg_view_entity_list($entities, $count, $offset, $limit, $fullview);
		
	}
	
	/**
	 * Returns a viewable list of entities contained in a number of groups.
	 *
	 * @param string $subtype The arbitrary subtype of the entity
	 * @param int $owner_guid The GUID of the owning user
	 * @param int $container_guid The GUID of the containing group
	 * @param int $limit The number of entities to display per page (default: 10)
	 * @param true|false $fullview Whether or not to display the full view (default: true)
	 * @return string A viewable list of entities
	 */
	function list_entities_groups($subtype = "", $owner_guid = 0, $container_guid = 0, $limit = 10, $fullview = true)
	{
		$offset = (int) get_input('offset');
		$count = get_objects_in_group($container_guid, $subtype, $owner_guid, 0, "", $limit, $offset, true);
		$entities = get_objects_in_group($container_guid, $subtype, $owner_guid, 0, "", $limit, $offset);

		return elgg_view_entity_list($entities, $count, $offset, $limit, $fullview);
	}
	
	/**
	 * Disable an entity but not delete it.
	 *
	 * @param int $guid
	 */
	function disable_entity($guid)
	{
		global $CONFIG;
		
		$guid = (int)$guid;
		if ($entity = get_entity($guid)) {
			if (trigger_elgg_event('delete',$entity->type,$entity)) {
				if ($entity->canEdit()) {
					
					$res = update_data("UPDATE {$CONFIG->dbprefix}entities set enabled='no' where guid={$guid}");
					
					return $res;
				} 
			}
		}
		return false;
	}
	
	/**
	 * Delete a given entity.
	 * 
	 * @param int $guid
	 */
	function delete_entity($guid)
	{
		global $CONFIG;
		
		// TODO Make sure this deletes all metadata/annotations/relationships/etc!!
		
		$guid = (int)$guid;
		if ($entity = get_entity($guid)) {
			if (trigger_elgg_event('delete',$entity->type,$entity)) {
				if ($entity->canEdit()) {
					$entity->clearMetadata();
					$entity->clearAnnotations();
					$entity->clearRelationships();
					$res = delete_data("DELETE from {$CONFIG->dbprefix}entities where guid={$guid}");
					return $res;
				} 
			}
		}
		return false;
		
	}
	
	/**
	 * Delete multiple entities that match a given query.
	 * This function itterates through and calls delete_entity on each one, this is somewhat inefficient but lets 
	 * the 'delete' even be called for each entity.
	 * 
	 * @param string $type The type of entity (eg "user", "object" etc)
	 * @param string $subtype The arbitrary subtype of the entity
	 * @param int $owner_guid The GUID of the owning user
	 */
	function delete_entities($type = "", $subtype = "", $owner_guid = 0)
	{
		$entities = get_entities($type, $subtype, $owner_guid, "time_created desc", 0);
		
		foreach ($entities as $entity)
			delete_entity($entity->guid);
		
		return true;
	}

	/**
	 * Handler called by trigger_plugin_hook on the "export" event.
	 */
	function export_entity_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'));
			
		$guid = (int)$params['guid'];
		
		// Get the entity
		$entity = get_entity($guid);
		if (!($entity instanceof ElggEntity))
			throw new InvalidClassException(sprintf(elgg_echo('InvalidClassException:NotValidElggStar'), $guid, get_class()));
		
		$export = $entity->export();
		
		if (is_array($export))
			foreach ($export as $e)
				$returnvalue[] = $e;
		else
			$returnvalue[] = $export;
		
		return $returnvalue;
	}
	
	/**
	 * Utility function used by import_entity_plugin_hook() to process an ODDEntity into an unsaved ElggEntity.
	 *
	 * @param ODDEntity $element The OpenDD element
	 * @return ElggEntity the unsaved entity which should be populated by items.
	 */
	function oddentity_to_elggentity(ODDEntity $element)
	{
		$class = $element->getAttribute('class');
		$subclass = $element->getAttribute('subclass');
		
		// See if we already have imported this uuid
		$tmp = get_entity_from_uuid($element->getAttribute('uuid'));
		
		if (!$tmp)
		{
			// Construct new class with owner from session
			$classname = get_subtype_class($class, $subclass);
			if ($classname!="")
			{
				if (class_exists($classname))
				{
					$tmp = new $classname();
					
					if (!($tmp instanceof ElggEntity))
						throw new ClassException(sprintf(elgg_echo('ClassException:ClassnameNotClass', $classname, get_class())));
				}
				else
					error_log(sprintf(elgg_echo('ClassNotFoundException:MissingClass'), $classname));	
			}
			else
			{
				switch ($class)
				{
					case 'object' : $tmp = new ElggObject($row); break;
					case 'user' : $tmp = new ElggUser($row); break;
					case 'group' : $tmp = new ElggGroup($row); break; 
					case 'site' : $tmp = new ElggSite($row); break; 
					default: throw new InstallationException(sprintf(elgg_echo('InstallationException:TypeNotSupported'), $class));
				}
			}
		}
		
		if ($tmp)
		{
			if (!$tmp->import($element))
				throw new ImportException(sprintf(elgg_echo('ImportException:ImportFailed'), $element->getAttribute('uuid')));
			
			return $tmp;
		}
		
		return NULL;
	}
	
	/**
	 * Import an entity.
	 * This function checks the passed XML doc (as array) to see if it is a user, if so it constructs a new 
	 * elgg user and returns "true" to inform the importer that it's been handled.
	 */
	function import_entity_plugin_hook($hook, $entity_type, $returnvalue, $params)
	{
		$element = $params['element'];
		
		$tmp = NULL;
		
		if ($element instanceof ODDEntity)
		{
			$tmp = oddentity_to_elggentity($element);
			
			if ($tmp)
			{
				if (!$tmp->save()) // Make sure its saved
					throw new ImportException(sprintf(elgg_echo('ImportException:ProblemSaving'), $element->getAttribute('uuid')));
	
				// Belts and braces
				if (!$tmp->guid)
					throw new ImportException(elgg_echo('ImportException:NoGUID')); 
				
				add_uuid_to_guid($tmp->guid, $element->getAttribute('uuid')); // We have saved, so now tag
				
				return $tmp;
			}
			
		}
	}
	
	/**
	 * Determines whether or not the specified user can edit the specified entity.
	 * 
	 * This is extendible by registering a plugin hook taking in the parameters 'entity' and 'user',
	 * which are the entity and user entities respectively
	 * 
	 * @see register_plugin_hook 
	 *
	 * @param int $entity_guid The GUID of the entity
	 * @param int $user_guid The GUID of the user
	 * @return true|false Whether the specified user can edit the specified entity.
	 */
	function can_edit_entity($entity_guid, $user_guid = 0) {
		global $CONFIG;
		if ($user_guid == 0) {
					
			if (isset($_SESSION['user'])) {			
				$user = $_SESSION['user'];
			} else {		
				$user = null;
			}
		} else {		
			$user = get_entity($user_guid);
		}

		if (($entity = get_entity($entity_guid)) && (!is_null($user))) {
			
			if ($entity->getOwner() == $user->getGUID()) return true;
			if ($entity->type == "user" && $entity->getGUID() == $user->getGUID()) return true;
		
			return trigger_plugin_hook('permissions_check',$entity->type,array('entity' => $entity, 'user' => $user),false);
		
		} else {		
			return false;
			
		}
		
	}
	
	/**
	 * Determines whether or not the specified user can edit metadata on the specified entity.
	 * 
	 * This is extendible by registering a plugin hook taking in the parameters 'entity' and 'user',
	 * which are the entity and user entities respectively
	 * 
	 * @see register_plugin_hook 
	 *
	 * @param int $entity_guid The GUID of the entity
	 * @param int $user_guid The GUID of the user
	 * @return true|false Whether the specified user can edit the specified entity.
	 */
	function can_edit_entity_metadata($entity_guid, $user_guid = 0) {
		
		if ($entity = get_entity($entity_guid)) {
			$return = can_edit_entity($entity_guid, $user_guid);
			$return = trigger_plugin_hook('permissions_check:metadata',$entity->type,array('entity' => $entity, 'user' => $user),$return);
			return $return;
		} else {
			return false;
		}
		
	}
	
	/**
	 * Gets the URL for an entity, given a particular GUID
	 *
	 * @param int $entity_guid The GUID of the entity
	 * @return string The URL of the entity
	 */
	function get_entity_url($entity_guid) {
		
		global $CONFIG;
		if ($entity = get_entity($entity_guid)) {

			$url = "";
			
			if (isset($CONFIG->entity_url_handler[$entity->getType()][$entity->getSubType()])) {
				$function =  $CONFIG->entity_url_handler[$entity->getType()][$entity->getSubType()];
				if (is_callable($function)) {
					$url = $function($entity);
				}
			}
			if (isset($CONFIG->entity_url_handler[$entity->getType()]['all'])) {
				$function =  $CONFIG->entity_url_handler[$entity->getType()]['all'];
				if (is_callable($function)) {
					$url = $function($entity);
				}
			}
			if (isset($CONFIG->entity_url_handler['all']['all'])) {
				$function =  $CONFIG->entity_url_handler['all']['all'];
				if (is_callable($function)) {
					$url = $function($entity);
				}
			}

			if ($url == "") {
				$url = $CONFIG->url . "pg/view/" . $entity_guid;
			}
			return $url;
			
		}
		return false;
		
	}
	
	/**
	 * Sets the URL handler for a particular entity type and subtype
	 *
	 * @param string $function_name The function to register
	 * @param string $entity_type The entity type
	 * @param string $entity_subtype The entity subtype
	 * @return true|false Depending on success
	 */
	function register_entity_url_handler($function_name, $entity_type = "all", $entity_subtype = "all") {
		global $CONFIG;
		
		if (!is_callable($function_name)) return false;
		
		if (!isset($CONFIG->entity_url_handler)) {
			$CONFIG->entity_url_handler = array();
		}
		if (!isset($CONFIG->entity_url_handler[$entity_type])) {
			$CONFIG->entity_url_handler[$entity_type] = array();
		}
		$CONFIG->entity_url_handler[$entity_type][$entity_subtype] = $function_name;
		
		return true;
		
	}
	
	/**
	 * Page handler for generic entities view system
	 *
	 * @param array $page Page elements from pain page handler
	 */
	function entities_page_handler($page) {
		if (isset($page[0])) {
			global $CONFIG;
			set_input('guid',$page[0]);
			@include($CONFIG->path . "entities/index.php");
		}
	}
	
	/**
	 * Entities init function; establishes the page handler
	 *
	 */
	function entities_init() {
		register_page_handler('view','entities_page_handler');
	}
	
	/** Register the import hook */
	register_plugin_hook("import", "all", "import_entity_plugin_hook", 0);
	
	/** Register the hook, ensuring entities are serialised first */
	register_plugin_hook("export", "all", "export_entity_plugin_hook", 0);
	
	/** Register init system event **/
	register_elgg_event_handler('init','system','entities_init');
	
?>