aboutsummaryrefslogtreecommitdiff
path: root/engine/lib/plugins.php
blob: d6352cbc69aeb5461601a48365888cba7afe9714 (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
<?php
/**
 * Elgg plugins library
 * Contains functions for managing plugins
 *
 * @package Elgg.Core
 * @subpackage Plugins
 */

/// Cache enabled plugins per page
$ENABLED_PLUGINS_CACHE = NULL;

/**
 * Returns a list of plugins to load, in the order that they should be loaded.
 *
 * @return array List of plugins
 */
function get_plugin_list() {
	global $CONFIG;

	if (!empty($CONFIG->pluginlistcache)) {
		return $CONFIG->pluginlistcache;
	}

	if ($site = get_entity($CONFIG->site_guid)) {
		$pluginorder = $site->pluginorder;
		if (!empty($pluginorder)) {
			$plugins = unserialize($pluginorder);

			$CONFIG->pluginlistcache = $plugins;
			return $plugins;
		} else {
			// this only runs on install, otherwise uses serialized plugin order
			$plugins = array();

			if ($handle = opendir($CONFIG->pluginspath)) {
				while ($mod = readdir($handle)) {
					// must be directory and not begin with a .
					if (substr($mod, 0, 1) !== '.' && is_dir($CONFIG->pluginspath . "/" . $mod)) {
						$plugins[] = $mod;
					}
				}
			}

			sort($plugins);

			$CONFIG->pluginlistcache = $plugins;
			return $plugins;
		}
	}

	return false;
}

/**
 * Regenerates the list of known plugins and saves it to the current site
 *
 * Important: You should regenerate simplecache and the viewpath cache after executing this function
 * otherwise you may experience view display artifacts. Do this with the following code:
 *
 * 		elgg_view_regenerate_simplecache();
 *		elgg_filepath_cache_reset();
 *
 * @param array $pluginorder Optionally, a list of existing plugins and their orders
 *
 * @return array The new list of plugins and their orders
 */
function regenerate_plugin_list($pluginorder = FALSE) {
	global $CONFIG;

	$CONFIG->pluginlistcache = NULL;

	if ($site = get_entity($CONFIG->site_guid)) {
		if (empty($pluginorder)) {
			$pluginorder = $site->pluginorder;
			$pluginorder = unserialize($pluginorder);
		} else {
			ksort($pluginorder);
		}

		if (empty($pluginorder)) {
			$pluginorder = array();
		}

		$max = 0;
		if (sizeof($pluginorder)) {
			foreach ($pluginorder as $key => $plugin) {
				if (is_dir($CONFIG->pluginspath . "/" . $plugin)) {
					if ($key > $max) {
						$max = $key;
					}
				} else {
					unset($pluginorder[$key]);
				}
			}
		}
		// Add new plugins to the end
		if ($handle = opendir($CONFIG->pluginspath)) {
			while ($mod = readdir($handle)) {
				// must be directory and not begin with a .
				if (substr($mod, 0, 1) !== '.' && is_dir($CONFIG->pluginspath . "/" . $mod)) {
					if (!in_array($mod, $pluginorder)) {
						$max = $max + 10;
						$pluginorder[$max] = $mod;
					}
				}
			}
		}

		ksort($pluginorder);

		// Now reorder the keys ..
		$key = 10;
		$plugins = array();
		if (sizeof($pluginorder)) {
			foreach ($pluginorder as $plugin) {
				$plugins[$key] = $plugin;
				$key = $key + 10;
			}
		}

		$plugins = serialize($plugins);

		$site->pluginorder = $plugins;

		return $plugins;
	}

	return FALSE;
}


/**
 * For now, loads plugins directly
 *
 * @todo Add proper plugin handler that launches plugins in an
 * admin-defined order and activates them on admin request
 *
 * @return void
 */
function load_plugins() {
	global $CONFIG;

	if (!empty($CONFIG->pluginspath)) {
		// See if we have cached values for things
		$cached_view_paths = elgg_filepath_cache_load();
		if ($cached_view_paths) {
			$CONFIG->views = unserialize($cached_view_paths);
		}

		// temporary disable all plugins if there is a file called 'disabled' in the plugin dir
		if (file_exists($CONFIG->pluginspath . "disabled")) {
			return;
		}

		$plugins = get_plugin_list();

		if (sizeof($plugins)) {
			foreach ($plugins as $mod) {
				if (is_plugin_enabled($mod)) {
					if (file_exists($CONFIG->pluginspath . $mod)) {
						if (!include($CONFIG->pluginspath . $mod . "/start.php")) {
							// automatically disable the bad plugin
							disable_plugin($mod);

							// register error rather than rendering the site unusable with exception
							register_error(sprintf(elgg_echo('PluginException:MisconfiguredPlugin'), $mod));

							// continue loading remaining plugins
							continue;
						}

						if (!$cached_view_paths) {
							$view_dir = $CONFIG->pluginspath . $mod . '/views/';

							if (is_dir($view_dir) && ($handle = opendir($view_dir))) {
								while (FALSE !== ($view_type = readdir($handle))) {
									$view_type_dir = $view_dir . $view_type;

									if ('.' !== substr($view_type, 0, 1) && is_dir($view_type_dir)) {
										if (autoregister_views('', $view_type_dir, $view_dir, $view_type)) {
											// add the valid view type.
											if (!in_array($view_type, $CONFIG->view_types)) {
												$CONFIG->view_types[] = $view_type;
											}
										}
									}
								}
							}
						}

						if (is_dir($CONFIG->pluginspath . $mod . "/languages")) {
							register_translations($CONFIG->pluginspath . $mod . "/languages/");
						}

						if (is_dir($CONFIG->pluginspath . "$mod/classes")) {
							elgg_register_classes($CONFIG->pluginspath . "$mod/classes");
						}
					}
				}
			}
		}

		// Cache results
		if (!$cached_view_paths) {
			elgg_filepath_cache_save(serialize($CONFIG->views));
		}
	}
}

/**
 * Get the name of the most recent plugin to be called in the
 * call stack (or the plugin that owns the current page, if any).
 *
 * i.e., if the last plugin was in /mod/foobar/, get_plugin_name would return foo_bar.
 *
 * @param boolean $mainfilename If set to true, this will instead determine the
 *                              context from the main script filename called by
 *                              the browser. Default = false.
 *
 * @return string|false Plugin name, or false if no plugin name was called
 */
function get_plugin_name($mainfilename = false) {
	if (!$mainfilename) {
		if ($backtrace = debug_backtrace()) {
			foreach ($backtrace as $step) {
				$file = $step['file'];
				$file = str_replace("\\", "/", $file);
				$file = str_replace("//", "/", $file);
				if (preg_match("/mod\/([a-zA-Z0-9\-\_]*)\/start\.php$/", $file, $matches)) {
					return $matches[1];
				}
			}
		}
	} else {
		if (preg_match("/pg\/([a-zA-Z0-9\-\_]*)\//", $_SERVER['REQUEST_URI'], $matches)) {
			return $matches[1];
		} else {
			$file = $_SERVER["SCRIPT_NAME"];
			$file = str_replace("\\", "/", $file);
			$file = str_replace("//", "/", $file);
			if (preg_match("/mod\/([a-zA-Z0-9\-\_]*)\//", $file, $matches)) {
				return $matches[1];
			}
		}
	}
	return false;
}

/**
 * Load and parse a plugin manifest from a plugin XML file.
 *
 * Example file:
 *
 *	<plugin_manifest>
 *		<!-- Basic information -->
 *		<field key="name" value="My Plugin" />
 *		<field key="description" value="My Plugin's concise description" />
 *		<field key="version" value="1.0" />
 *		<field key="category" value="theme" />
 *		<field key="category" value="bundled" />
 *		<field key="screenshot" value="path/relative/to/my_plugin.jpg" />
 *		<field key="screenshot" value="path/relative/to/my_plugin_2.jpg" />
 *
 *		<field key="author" value="Curverider Ltd" />
 *		<field key="website" value="http://www.elgg.org/" />
 *		<field key="copyright" value="(C) Curverider 2008-2010" />
 *		<field key="licence" value="GNU Public License version 2" />
 *	</plugin_manifest>
 *
 * @param string $plugin Plugin name.
 *
 * @return array of values
 */
function load_plugin_manifest($plugin) {
	global $CONFIG;

	$xml = xml_to_object(file_get_contents($CONFIG->pluginspath . $plugin . "/manifest.xml"));

	if ($xml) {
		// set up some defaults to normalize expected values to arrays
		$elements = array(
			'screenshot' => array(),
			'category' => array()
		);

		foreach ($xml->children as $element) {
			$key = $element->attributes['key'];
			$value = $element->attributes['value'];

			// create arrays if multiple fields are set
			if (array_key_exists($key, $elements)) {
				if (!is_array($elements[$key])) {
					$orig = $elements[$key];
					$elements[$key] = array($orig);
				}

				$elements[$key][] = $value;
			} else {
				$elements[$key] = $value;
			}
		}

		// handle plugins that don't define a name
		if (!isset($elements['name'])) {
			$elements['name'] = ucwords($plugin);
		}

		return $elements;
	}

	return false;
}

/**
 * This function checks a plugin manifest 'elgg_version' value against the current install
 * returning TRUE if the elgg_version is >= the current install's version.
 *
 * @param string $manifest_elgg_version_string The build version (eg 2009010201).
 *
 * @return bool
 */
function check_plugin_compatibility($manifest_elgg_version_string) {
	$version = get_version();

	if (strpos($manifest_elgg_version_string, '.') === false) {
		// Using version
		$req_version = (int)$manifest_elgg_version_string;

		return ($version >= $req_version);
	}

	return false;
}

/**
 * Shorthand function for finding the plugin settings.
 *
 * @param string $plugin_name Optional plugin name, if not specified
 *                            then it is detected from where you are calling from.
 *
 * @return mixed
 */
function find_plugin_settings($plugin_name = "") {
	$options = array('type' => 'object', 'subtype' => 'plugin', 'limit' => 9999);
	$plugins = elgg_get_entities($options);
	$plugin_name = sanitise_string($plugin_name);
	if (!$plugin_name) {
		$plugin_name = get_plugin_name();
	}

	if ($plugins) {
		foreach ($plugins as $plugin) {
			if (strcmp($plugin->title, $plugin_name) == 0) {
				return $plugin;
			}
		}
	}

	return false;
}

/**
 * Find the plugin settings for a user.
 *
 * @param string $plugin_name Plugin name.
 * @param int    $user_guid   The guid who's settings to retrieve.
 *
 * @return array of settings in an associative array minus prefix.
 */
function find_plugin_usersettings($plugin_name = "", $user_guid = 0) {
	$plugin_name = sanitise_string($plugin_name);
	$user_guid = (int)$user_guid;

	if (!$plugin_name) {
		$plugin_name = get_plugin_name();
	}

	if ($user_guid == 0) {
		$user_guid = get_loggedin_userid();
	}

	// Get metadata for user
	$all_metadata = get_all_private_settings($user_guid); //get_metadata_for_entity($user_guid);
	if ($all_metadata) {
		$prefix = "plugin:settings:$plugin_name:";
		$return = new stdClass;

		foreach ($all_metadata as $key => $meta) {
			$name = substr($key, strlen($prefix));
			$value = $meta;

			if (strpos($key, $prefix) === 0) {
				$return->$name = $value;
			}
		}

		return $return;
	}

	return false;
}

/**
 * Set a user specific setting for a plugin.
 *
 * @param string $name        The name - note, can't be "title".
 * @param mixed  $value       The value.
 * @param int    $user_guid   Optional user.
 * @param string $plugin_name Optional plugin name, if not specified then it
 *                            is detected from where you are calling from.
 *
 * @return bool
 */
function set_plugin_usersetting($name, $value, $user_guid = 0, $plugin_name = "") {
	$plugin_name = sanitise_string($plugin_name);
	$user_guid = (int)$user_guid;
	$name = sanitise_string($name);

	if (!$plugin_name) {
		$plugin_name = get_plugin_name();
	}

	$user = get_entity($user_guid);
	if (!$user) {
		$user = get_loggedin_user();
	}

	if (($user) && ($user instanceof ElggUser)) {
		$prefix = "plugin:settings:$plugin_name:$name";
		//$user->$prefix = $value;
		//$user->save();

		// Hook to validate setting
		$value = trigger_plugin_hook('plugin:usersetting', 'user', array(
			'user' => $user,
			'plugin' => $plugin_name,
			'name' => $name,
			'value' => $value
		), $value);

		return set_private_setting($user->guid, $prefix, $value);
	}

	return false;
}

/**
 * Clears a user-specific plugin setting
 *
 * @param str $name        Name of the plugin setting
 * @param int $user_guid   Defaults to logged in user
 * @param str $plugin_name Defaults to contextual plugin name
 *
 * @return bool Success
 */
function clear_plugin_usersetting($name, $user_guid = 0, $plugin_name = '') {
	$plugin_name = sanitise_string($plugin_name);
	$name = sanitise_string($name);

	if (!$plugin_name) {
		$plugin_name = get_plugin_name();
	}

	$user = get_entity((int) $user_guid);
	if (!$user) {
		$user = get_loggedin_user();
	}

	if (($user) && ($user instanceof ElggUser)) {
		$prefix = "plugin:settings:$plugin_name:$name";

		return remove_private_setting($user->getGUID(), $prefix);
	}

	return FALSE;
}

/**
 * Get a user specific setting for a plugin.
 *
 * @param string $name        The name.
 * @param int    $user_guid   Guid of owning user
 * @param string $plugin_name Optional plugin name, if not specified
 *                            then it is detected from where you are calling from.
 *
 * @return mixed
 */
function get_plugin_usersetting($name, $user_guid = 0, $plugin_name = "") {
	$plugin_name = sanitise_string($plugin_name);
	$user_guid = (int)$user_guid;
	$name = sanitise_string($name);

	if (!$plugin_name) {
		$plugin_name = get_plugin_name();
	}

	$user = get_entity($user_guid);
	if (!$user) {
		$user = get_loggedin_user();
	}

	if (($user) && ($user instanceof ElggUser)) {
		$prefix = "plugin:settings:$plugin_name:$name";
		return get_private_setting($user->guid, $prefix);
	}

	return false;
}

/**
 * Set a setting for a plugin.
 *
 * @param string $name        The name - note, can't be "title".
 * @param mixed  $value       The value.
 * @param string $plugin_name Optional plugin name, if not specified
 *                            then it is detected from where you are calling from.
 *
 * @return int|false
 */
function set_plugin_setting($name, $value, $plugin_name = "") {
	if (!$plugin_name) {
		$plugin_name = get_plugin_name();
	}
	$plugin = find_plugin_settings($plugin_name);

	if (!$plugin) {
		$plugin = new ElggPlugin();
	}

	if ($name != 'title') {
		// Hook to validate setting
		$value = trigger_plugin_hook('plugin:setting', 'plugin', array(
			'plugin' => $plugin_name,
			'name' => $name,
			'value' => $value
		), $value);

		$plugin->title = $plugin_name;
		$plugin->access_id = ACCESS_PUBLIC;
		$plugin->save();
		$plugin->$name = $value;

		return $plugin->getGUID();
	}

	return false;
}

/**
 * Get setting for a plugin.
 *
 * @param string $name        The name.
 * @param string $plugin_name Optional plugin name, if not specified
 *                            then it is detected from where you are calling from.
 *
 * @return mixed
 */
function get_plugin_setting($name, $plugin_name = "") {
	$plugin = find_plugin_settings($plugin_name);

	if ($plugin) {
		return $plugin->$name;
	}

	return false;
}

/**
 * Clear a plugin setting.
 *
 * @param string $name        The name.
 * @param string $plugin_name Optional plugin name, if not specified
 *                            then it is detected from where you are calling from.
 *
 * @return bool
 */
function clear_plugin_setting($name, $plugin_name = "") {
	$plugin = find_plugin_settings($plugin_name);

	if ($plugin) {
		return remove_private_setting($plugin->guid, $name);
	}

	return FALSE;
}

/**
 * Clear all plugin settings.
 *
 * @param string $plugin_name Optional plugin name, if not specified
 *                            then it is detected from where you are calling from.
 *
 * @return bool
 * @since 1.7.0
 */
function clear_all_plugin_settings($plugin_name = "") {
	$plugin = find_plugin_settings($plugin_name);

	if ($plugin) {
		return remove_all_private_settings($plugin->guid);
	}

	return FALSE;
}

/**
 * Return an array of installed plugins.
 *
 * @return array
 */
function get_installed_plugins() {
	global $CONFIG;

	$installed_plugins = array();

	if (!empty($CONFIG->pluginspath)) {
		$plugins = get_plugin_list();

		foreach ($plugins as $mod) {
			// require manifest.
			if (!$manifest = load_plugin_manifest($mod)) {
				continue;
			}
			$installed_plugins[$mod] = array();
			$installed_plugins[$mod]['active'] = is_plugin_enabled($mod);
			$installed_plugins[$mod]['manifest'] = $manifest;
		}
	}

	return $installed_plugins;
}

/**
 * Enable a plugin for a site (default current site)
 *
 * Important: You should regenerate simplecache and the viewpath cache after executing this function
 * otherwise you may experience view display artifacts. Do this with the following code:
 *
 * 		elgg_view_regenerate_simplecache();
 *		elgg_filepath_cache_reset();
 *
 * @param string $plugin    The plugin name.
 * @param int    $site_guid The site id, if not specified then this is detected.
 *
 * @return array
 * @throws InvalidClassException
 */
function enable_plugin($plugin, $site_guid = 0) {
	global $CONFIG, $ENABLED_PLUGINS_CACHE;

	$plugin = sanitise_string($plugin);
	$site_guid = (int) $site_guid;
	if ($site_guid == 0) {
		$site_guid = $CONFIG->site_guid;
	}

	$site = get_entity($site_guid);
	if (!($site instanceof ElggSite)) {
		$msg = sprintf(elgg_echo('InvalidClassException:NotValidElggStar'), $site_guid, "ElggSite");
		throw new InvalidClassException($msg);
	}

	if (!$plugin_info = load_plugin_manifest($plugin)) {
		return FALSE;
	}

	// getMetadata() doesn't return an array if only one plugin is enabled
	if ($enabled = $site->enabled_plugins) {
		if (!is_array($enabled)) {
			$enabled = array($enabled);
		}
	} else {
		$enabled = array();
	}

	$enabled[] = $plugin;
	$enabled = array_unique($enabled);

	if ($return = $site->setMetaData('enabled_plugins', $enabled)) {

		// for other plugins that want to hook into this.
		$params = array('plugin' => $plugin, 'manifest' => $plugin_info);
		if ($return && !trigger_elgg_event('enable', 'plugin', $params)) {
			$return = FALSE;
		}

		// for this plugin's on_enable
		if ($return && isset($plugin_info['on_enable'])) {
			// pull in the actual plugin's start so the on_enable function is callable
			// NB: this will not run re-run the init hooks!
			$start = "{$CONFIG->pluginspath}$plugin/start.php";
			if (!file_exists($start) || !include($start)) {
				$return = FALSE;
			}

			// need language files for the messages
			$translations = "{$CONFIG->pluginspath}$plugin/languages/";
			register_translations($translations);
			if (!is_callable($plugin_info['on_enable'])) {
				$return = FALSE;
			} else {
				$on_enable = call_user_func($plugin_info['on_enable']);
				// allow null to mean "I don't care" like other subsystems
				$return = ($on_disable === FALSE) ? FALSE : TRUE;
			}
		}

		// disable the plugin if the on_enable or trigger results failed
		if (!$return) {
			array_pop($enabled);
			$site->setMetaData('enabled_plugins', $enabled);
		}

		$ENABLED_PLUGINS_CACHE = $enabled;
	}

	return $return;
}

/**
 * Disable a plugin for a site (default current site)
 *
 * Important: You should regenerate simplecache and the viewpath cache after executing this function
 * otherwise you may experience view display artifacts. Do this with the following code:
 *
 * 		elgg_view_regenerate_simplecache();
 *		elgg_filepath_cache_reset();
 *
 * @param string $plugin    The plugin name.
 * @param int    $site_guid The site id, if not specified then this is detected.
 *
 * @return bool
 * @throws InvalidClassException
 */
function disable_plugin($plugin, $site_guid = 0) {
	global $CONFIG, $ENABLED_PLUGINS_CACHE;

	$plugin = sanitise_string($plugin);
	$site_guid = (int) $site_guid;
	if ($site_guid == 0) {
		$site_guid = $CONFIG->site_guid;
	}

	$site = get_entity($site_guid);
	if (!($site instanceof ElggSite)) {
		$msg = sprintf(elgg_echo('InvalidClassException:NotValidElggStar'), $site_guid, "ElggSite");
		throw new InvalidClassException();
	}

	if (!$plugin_info = load_plugin_manifest($plugin)) {
		return FALSE;
	}

	// getMetadata() doesn't return an array if only one plugin is enabled
	if ($enabled = $site->enabled_plugins) {
		if (!is_array($enabled)) {
			$enabled = array($enabled);
		}
	} else {
		$enabled = array();
	}

	$old_enabled = $enabled;

	// remove the disabled plugin from the array
	if (FALSE !== $i = array_search($plugin, $enabled)) {
		unset($enabled[$i]);
	}

	// if we're unsetting all the plugins, this will return an empty array.
	// it will fail with FALSE, though.
	$return = (FALSE === $site->enabled_plugins = $enabled) ? FALSE : TRUE;

	if ($return) {
		// for other plugins that want to hook into this.
		$params = array('plugin' => $plugin, 'manifest' => $plugin_info);
		if ($return && !trigger_elgg_event('disable', 'plugin', $params)) {
			$return = FALSE;
		}

		// for this plugin's on_disable
		if ($return && isset($plugin_info['on_disable'])) {
			if (!is_callable($plugin_info['on_disable'])) {
				$return = FALSE;
			} else {
				$on_disable = call_user_func($plugin_info['on_disable']);
				// allow null to mean "I don't care" like other subsystems
				$return = ($on_disable === FALSE) ? FALSE : TRUE;
			}
		}

		// disable the plugin if the on_enable or trigger results failed
		if (!$return) {
			$site->enabled_plugins = $old_enabled;
			$ENABLED_PLUGINS_CACHE = $old_enabled;
		} else {
			$ENABLED_PLUGINS_CACHE = $enabled;
		}
	}

	return $return;
}

/**
 * Return whether a plugin is enabled or not.
 *
 * @param string $plugin    The plugin name.
 * @param int    $site_guid The site id, if not specified then this is detected.
 *
 * @return bool
 * @throws InvalidClassException
 */
function is_plugin_enabled($plugin, $site_guid = 0) {
	global $CONFIG, $ENABLED_PLUGINS_CACHE;

	if (!file_exists($CONFIG->pluginspath . $plugin)) {
		return false;
	}

	$site_guid = (int) $site_guid;
	if ($site_guid == 0) {
		$site_guid = $CONFIG->site_guid;
	}

	if (!$ENABLED_PLUGINS_CACHE) {
		$site = get_entity($site_guid);
		if (!($site instanceof ElggSite)) {
			$msg = sprintf(elgg_echo('InvalidClassException:NotValidElggStar'), $site_guid, "ElggSite");
			throw new InvalidClassException($msg);
		}

		$enabled_plugins = $site->enabled_plugins;
		if ($enabled_plugins && !is_array($enabled_plugins)) {
			$enabled_plugins = array($enabled_plugins);
		}
		$ENABLED_PLUGINS_CACHE = $enabled_plugins;
	}

	foreach ($ENABLED_PLUGINS_CACHE as $e) {
		if ($e == $plugin) {
			return true;
		}
	}

	return false;
}

/**
 * Register object, plugin entities as ElggPlugin classes
 *
 *  @return void
 */
function plugin_run_once() {
	// Register a class
	add_subtype("object", "plugin", "ElggPlugin");
}

/**
 * Initialise the file modules.
 * Listens to system boot and registers any appropriate file types and classes
 *
 * @return void
 */
function plugin_init() {
	// Now run this stuff, but only once
	run_function_once("plugin_run_once");

	// Register some actions
	register_action("plugins/settings/save", false, "", true);
	register_action("plugins/usersettings/save");

	register_action('admin/plugins/enable', false, "", true);
	register_action('admin/plugins/disable', false, "", true);
	register_action('admin/plugins/enableall', false, "", true);
	register_action('admin/plugins/disableall', false, "", true);

	register_action('admin/plugins/reorder', false, "", true);
}

// Register a startup event
register_elgg_event_handler('init', 'system', 'plugin_init');