Merge branch 'main' into issue-3911issue-3911

1 files changed, 174 insertions, 0 deletions

diff --git a/lib/classes/NotificationCenter.php b/lib/classes/NotificationCenter.php
new file mode 100644
index 0000000..178fd62
--- /dev/null
+++ b/lib/classes/NotificationCenter.php
@@ -0,0 +1,174 @@
+<?php
+# Lifter010: TODO
+/*
+ * NotificationCenter.php - NotificationCenter class
+ *
+ * Copyright (c) 2009  Elmar Ludwig
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ */
+
+// ########################################################################
+//  MODULE DEFINITION
+/** @defgroup notifications Notifications */
+
+/**
+ * Special Exception that can be thrown to veto an announced change.
+ * Only some types of events support this (see documentation).
+ */
+class NotificationVetoException extends Exception
+{
+}
+
+/**
+ * The NotificationCenter class is the central event dispatcher
+ * for Stud.IP. Objects interested in receiving notifications for
+ * particular events need to register with the NotificationCenter:
+ *
+ * NotificationCenter::addObserver($this, 'update', 'shutdown');
+ *
+ * Event notifications are sent via the postNotification() method:
+ *
+ * NotificationCenter::postNotification('shutdown', $sender);
+ */
+class NotificationCenter
+{
+    /**
+     * array of registered notification observers
+     */
+    private static $observers = [];
+
+    /**
+     * Register an object to be notified. The same object may be
+     * registered several times (e.g. for different notifications).
+     * The event name may contain shell-style wildcards (like '*').
+     *
+     * @param object $observer  object to be notified
+     * @param string $method    method that will be called
+     * @param string $event     name of event (may be NULL)
+     * @param mixed  $object    subject to observe (may be NULL)
+     */
+    public static function addObserver($observer, $method, $event, $object = NULL)
+    {
+        if ($event === NULL) {
+            $event = '';
+        }
+
+        $predicate = null;
+
+        if ($object) {
+            $predicate = is_callable($object)
+                ? $object
+                : function ($other) use ($object) {
+                    return $object === $other;
+                  };
+        }
+
+        self::$observers[$event][] = [
+            'predicate' => $predicate,
+            'observer'  => [$observer, $method]
+        ];
+    }
+
+    /**
+     * Remove an object registered with the NotificationCenter.
+     * Trying to remove an observer that was not registered is
+     * allowed and has no effect.
+     *
+     * @param object $observer  object to be removed
+     * @param string $event     name of event (may be NULL)
+     * @param mixed  $object    subject to observe (may be NULL)
+     */
+    public static function removeObserver($observer, $event = NULL, $object = NULL)
+    {
+        if ($event === NULL) {
+            $events = array_keys(self::$observers);
+        } else if (isset(self::$observers[$event])) {
+            $events = [$event];
+        } else {
+            return;
+        }
+
+        foreach ($events as $event) {
+            foreach (self::$observers[$event] as $index => $list) {
+                if ($object === NULL
+                    || $list['predicate'] && $list['predicate']($object)) {
+
+                    if ($list['observer'][0] === $observer) {
+                        unset(self::$observers[$event][$index]);
+                    }
+                }
+            }
+        }
+    }
+
+    /**
+     * Post an event notification to all registered observers.
+     * Only observers registered for this event type and subject
+     * are notified.
+     *
+     * @param string $event     name of this notification
+     * @param mixed  $object    subject of this notification
+     * @param mixed  $user_data additional information (optional)
+     *
+     * @throws NotificationVetoException  on observer veto
+     */
+    public static function postNotification($event, $object, $user_data = null)
+    {
+        $current_observers = [];
+        foreach (self::$observers as $e => $l) {
+            if ($e === '' || fnmatch($e, $event, FNM_NOESCAPE)) {
+                $current_observers = array_merge($current_observers, $l);
+            }
+        }
+
+        foreach ($current_observers as $list) {
+            if (!$list['predicate'] || $list['predicate']($object)) {
+                call_user_func($list['observer'], $event, $object, $user_data);
+            }
+        }
+    }
+
+    /**
+     * Convenience method that uses a jQuery like structure for event
+     * registration by closures.
+     *
+     * @param string   $event
+     * @param Callable $callback
+     * @param mixed    $object
+     * @since Stud.IP 4.2
+     */
+    public static function on($event, Callable $callback, $object = null)
+    {
+        if ($callback instanceof Closure || is_object($callback)) {
+            static::addObserver($callback, '__invoke', $event, $object);
+        } elseif (is_array($callback)) {
+            static::addObserver($callback[0], $callback[1], $event, $object);
+        } elseif (is_string($callback)) {
+            throw new Exception('Strings as callable may not be passed to ' . __METHOD__);
+        }
+    }
+
+    /**
+     * Convenience method that uses a jQuery like structure for event
+     * unregistration by closures.
+     *
+     * @param string   $event
+     * @param Callable $callback
+     * @param mixed    $object
+     * @since Stud.IP 4.2
+     */
+    public static function off($event, Callable $callback, $object = null)
+    {
+        if ($callback instanceof Closure || is_object($callback)) {
+            static::removeObserver($callback, $event, $object);
+        } elseif (is_array($callback)) {
+            static::removeObserver($callback[0], $event, $object);
+        } elseif (is_string($callback)) {
+            throw new Exception('Strings as callable may not be passed to ' . __METHOD__);
+        }
+    }
+}