Implementing decorators for event callables.

First commit, proof of concept like, tests will follow.

src/Event/Decorator/EventDecorator.php

@@ -0,0 +1,78 @@
+<?php
+/**
+ * CakePHP : Rapid Development Framework (http://cakephp.org)
+ * Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
+ *
+ * Licensed under The MIT License
+ * For full copyright and license information, please see the LICENSE.txt
+ * Redistributions of files must retain the above copyright notice.
+ *
+ * @copyright     Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
+ * @link          http://cakephp.org CakePHP Project
+ * @since         3.3.0
+ * @license       http://www.opensource.org/licenses/mit-license.php MIT License
+ */
+namespace Cake\Event\Decorator;
+
+class EventDecorator {
+
+    /**
+     * Callable
+     *
+     * @var callable
+     */
+    protected $_callable;
+
+    /**
+     * Decorator options
+     *
+     * @var array
+     */
+    protected $_options = [];
+
+    /**
+     * Constructor.
+     *
+     * @param $callable $callable Callable.
+     * @param array $options Decorator options.
+     */
+    public function __construct(callable $callable, array $options = [])
+    {
+        $this->_callable = $callable;
+        $this->_options = $options;
+    }
+
+    /**
+     * Invoke
+     *
+     * @link http://php.net/manual/en/language.oop5.magic.php#object.invoke
+     * @return mixed
+     */
+    public function __invoke()
+    {
+        return $this->call($this->_callable, func_get_args());
+    }
+
+    /**
+     * Calls a callable with the passed arguments.
+     *
+     * @param $callable The callable.
+     * @param array $args Arguments for the callable.
+     * @return mixed
+     */
+    public function call(callable $callable, $args)
+    {
+        switch (count($args)) {
+            case 0:
+                return $callable();
+            case 1:
+                return $callable($args[0]);
+            case 2:
+                return $callable($args[0], $args[1]);
+            case 3:
+                return $callable($args[0], $args[1], $args[2]);
+            default:
+                return call_user_func_array($callable, $args);
+        }
+    }
+}

src/Event/Decorator/FilterDecorator.php

@@ -0,0 +1,63 @@
+<?php
+/**
+ * CakePHP : Rapid Development Framework (http://cakephp.org)
+ * Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
+ *
+ * Licensed under The MIT License
+ * For full copyright and license information, please see the LICENSE.txt
+ * Redistributions of files must retain the above copyright notice.
+ *
+ * @copyright     Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
+ * @link          http://cakephp.org CakePHP Project
+ * @since         3.3.0
+ * @license       http://www.opensource.org/licenses/mit-license.php MIT License
+ */
+namespace Cake\Event\Decorator;
+
+use RuntimeException;
+
+class FilterDecorator extends EventDecorator {
+
+    /**
+     * @inheritdoc
+     */
+    public function __invoke() {
+        $args = func_get_args();
+        if (!$this->canTrigger($args[0])) {
+            return false;
+        }
+        return call_user_func_array('parent::__invoke', $args);
+    }
+
+    /**
+     * Checks if the event is triggered for this listener.
+     *
+     * @param \Cake\Event\Event $event Event object.
+     * @return bool
+     */
+    public function canTrigger(Event $event)
+    {
+        $if = $this->_evaluateCondition('if', $event);
+        $unless = $this->_evaluateCondition('unless', $event);
+
+        return $if && !$unless;
+    }
+
+    /**
+     * Evaluates the filter conditions
+     *
+     * @param string $condition Condition type
+     * @param \Cake\Event\Event $event Event objekt
+     * @return bool
+     */
+    protected function _evaluateCondition($condition, Event $event)
+    {
+        if (!isset($this->_options[$condition])) {
+            return true;
+        }
+        if (!is_callable($this->_options[$condition])) {
+            throw new RuntimeException('Is not a callable!');
+        }
+        return $this->_options[$condition]($event);
+    }
+}

src/Event/EventManager.php

@@ -14,6 +14,7 @@
  */
 namespace Cake\Event;
 
+use Cake\Event\Decorator\FilterDecorator;
 use InvalidArgumentException;
 
 /**
@@ -157,14 +158,14 @@ public function on($eventKey = null, $options = [], $callable = null)
         $argCount = func_num_args();
         if ($argCount === 2) {
             $this->_listeners[$eventKey][static::$defaultPriority][] = [
-                'callable' => $options
+                'callable' => new FilterDecorator($options),
             ];
             return;
         }
         if ($argCount === 3) {
             $priority = isset($options['priority']) ? $options['priority'] : static::$defaultPriority;
             $this->_listeners[$eventKey][$priority][] = [
-                'callable' => $callable
+                'callable' => new FilterDecorator($callable, $options)
             ];
             return;
         }