aboutsummaryrefslogtreecommitdiff
path: root/lib/dokuwiki/inc/events.php
blob: 1604c73c6b0c8ea385b9fc97c20667c6db15a63c (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
<?php
/**
 * DokuWiki Events
 *
 * @license    GPL 2 (http://www.gnu.org/licenses/gpl.html)
 * @author     Christopher Smith <chris@jalakai.co.uk>
 */

if(!defined('DOKU_INC')) die('meh.');
require_once(DOKU_INC.'inc/pluginutils.php');

class Doku_Event {

  // public properties
  var $name = '';                // READONLY  event name, objects must register against this name to see the event
  var $data = NULL;              // READWRITE data relevant to the event, no standardised format (YET!)
  var $result = NULL;            // READWRITE the results of the event action, only relevant in "_AFTER" advise
                                 //    event handlers may modify this if they are preventing the default action
                                 //    to provide the after event handlers with event results
  var $canPreventDefault = true; // READONLY  if true, event handlers can prevent the events default action

  // private properties, event handlers can effect these through the provided methods
  var $_default = true;     // whether or not to carry out the default action associated with the event
  var $_continue = true;    // whether or not to continue propagating the event to other handlers

  /**
   * event constructor
   */
  function Doku_Event($name, &$data) {

    $this->name = $name;
    $this->data =& $data;

  }

  /**
   * advise functions
   *
   * advise all registered handlers of this event
   *
   * if these methods are used by functions outside of this object, they must
   * properly handle correct processing of any default action and issue an
   * advise_after() signal. e.g.
   *    $evt = new Doku_Event(name, data);
   *    if ($evt->advise_before(canPreventDefault) {
   *      // default action code block
   *    }
   *    $evt->advise_after();
   *    unset($evt);
   *
   * @return  results of processing the event, usually $this->_default
   */
  function advise_before($enablePreventDefault=true) {
    global $EVENT_HANDLER;

    $this->canPreventDefault = $enablePreventDefault;
    $EVENT_HANDLER->process_event($this,'BEFORE');

    return (!$enablePreventDefault || $this->_default);
  }

  function advise_after() {
    global $EVENT_HANDLER;

    $this->_continue = true;
    $EVENT_HANDLER->process_event($this,'AFTER');
  }

  /**
   * trigger
   *
   * - advise all registered (<event>_BEFORE) handlers that this event is about to take place
   * - carry out the default action using $this->data based on $enablePrevent and
   *   $this->_default, all of which may have been modified by the event handlers.
   * - advise all registered (<event>_AFTER) handlers that the event has taken place
   *
   * @return  $event->results
   *          the value set by any <event>_before or <event> handlers if the default action is prevented
   *          or the results of the default action (as modified by <event>_after handlers)
   *          or NULL no action took place and no handler modified the value
   */
  function trigger($action=NULL, $enablePrevent=true) {

    if (!is_callable($action)) $enablePrevent = false;

    if ($this->advise_before($enablePrevent) && is_callable($action)) {
      if (is_array($action)) {
        list($obj,$method) = $action;
        $this->result = $obj->$method($this->data);
      } else {
        $this->result = $action($this->data);
      }
    }

    $this->advise_after();

    return $this->result;
  }

  /**
   * stopPropagation
   *
   * stop any further processing of the event by event handlers
   * this function does not prevent the default action taking place
   */
  function stopPropagation() { $this->_continue = false;  }

  /**
   * preventDefault
   *
   * prevent the default action taking place
   */
  function preventDefault() { $this->_default = false;  }
}

class Doku_Event_Handler {

  // public properties:  none

  // private properties
  var $_hooks = array();          // array of events and their registered handlers

  /**
   * event_handler
   *
   * constructor, loads all action plugins and calls their register() method giving them
   * an opportunity to register any hooks they require
   */
  function Doku_Event_Handler() {

    // load action plugins
    $plugin = NULL;
    $pluginlist = plugin_list('action');

    foreach ($pluginlist as $plugin_name) {
      $plugin =& plugin_load('action',$plugin_name);

      if ($plugin !== NULL) $plugin->register($this);
    }
  }

  /**
   * register_hook
   *
   * register a hook for an event
   *
   * @PARAM  $event   (string)   name used by the event, (incl '_before' or '_after' for triggers)
   * @PARAM  $obj     (obj)      object in whose scope method is to be executed,
   *                             if NULL, method is assumed to be a globally available function
   * @PARAM  $method  (function) event handler function
   * @PARAM  $param   (mixed)    data passed to the event handler
   */
  function register_hook($event, $advise, &$obj, $method, $param=NULL) {
    $this->_hooks[$event.'_'.$advise][] = array(&$obj, $method, $param);
  }

  function process_event(&$event,$advise='') {

    $evt_name = $event->name . ($advise ? '_'.$advise : '_BEFORE');

    if (!empty($this->_hooks[$evt_name])) {
      $hook = reset($this->_hooks[$evt_name]);
      do {
//        list($obj, $method, $param) = $hook;
        $obj =& $hook[0];
        $method = $hook[1];
        $param = $hook[2];

        if (is_null($obj)) {
          $method($event, $param);
        } else {
          $obj->$method($event, $param);
        }

      } while ($event->_continue && $hook = next($this->_hooks[$evt_name]));
    }
  }
}

/**
 *  trigger_event
 *
 *  function wrapper to process (create, trigger and destroy) an event
 *
 *  @PARAM  $name               (string)   name for the event
 *  @PARAM  $data               (mixed)    event data
 *  @PARAM  $action             (callback) (optional, default=NULL) default action, a php callback function
 *  @PARAM  $canPreventDefault  (bool)     (optional, default=true) can hooks prevent the default action
 *
 *  @RETURN (mixed)                        the event results value after all event processing is complete
 *                                         by default this is the return value of the default action however
 *                                         it can be set or modified by event handler hooks
 */
function trigger_event($name, &$data, $action=NULL, $canPreventDefault=true) {

  $evt = new Doku_Event($name, $data);
  return $evt->trigger($action, $canPreventDefault);
}

// create the event handler
global $EVENT_HANDLER;
$EVENT_HANDLER = new Doku_Event_Handler();