Refactor Event Manager

.gitattributes

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+tests export-ignore
+bin export-ignore
+.gitattributes export-ignore
+.gitignore export-ignore
+.travis.yml export-ignore
+phpcs.xml export-ignore
+README.md export-ignore
+LICENSE export-ignore

EventManager.php

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+<?php
+/**
+ * Event Manager for events and listeners.
+ * Based on https://carlalexander.ca/designing-system-wordpress-event-management/
+ *
+ * @package WPMedia\EventManager
+ */
+
+namespace WPMedia\EventManager;
+
+/**
+ * The event manager manages events using the WordPress plugin API.
+ */
+class EventManager
+{
+    /**
+     * WordPress plugin API manager
+     *
+     * @var PluginApiManager
+     */
+    private $plugin_api_manager;
+
+    /**
+     * Constructor
+     *
+     * @param PluginApiManager $plugin_api_manager WordPress plugin API manager.
+     */
+    public function __construct(PluginApiManager $plugin_api_manager)
+    {
+        $this->plugin_api_manager = $plugin_api_manager;
+    }
+
+    /**
+     * Adds the given event listener to the list of event listeners
+     *
+     * @param string   $event_name     Name of the event.
+     * @param callable $listener      Listener Callback function.
+     * @param int      $priority      Priority.
+     * @param int      $accepted_args Number of arguments.
+     */
+    public function addListener($event_name, $listener, $priority = 10, $accepted_args = 1)
+    {
+        $this->plugin_api_manager->addCallback($event_name, $listener, $priority, $accepted_args);
+    }
+
+    /**
+     * Adds an event subscriber.
+     *
+     * The event manager adds the given subscriber to the list of event listeners
+     * for all the events that it wants to listen to.
+     *
+     * @param SubscriberInterface $subscriber SubscriberInterface implementation.
+     */
+    public function addSubscriber(SubscriberInterface $subscriber)
+    {
+        if ($subscriber instanceof EventManagerAwareSubscriberInterface) {
+            $subscriber->setEventManager($this);
+        }
+
+        foreach ($subscriber->getSubscribedEvents() as $event_name => $parameters) {
+            $this->addSubscriberListener($subscriber, $event_name, $parameters);
+        }
+    }
+
+    /**
+     * Removes the given event listener from the list of event listeners
+     * that listen to the given event.
+     *
+     * @param string   $event_name Event name.
+     * @param callable $callback  Callback.
+     * @param int      $priority  Priority.
+     *
+     * @return bool
+     */
+    public function removeListener($event_name, $callback, $priority = 10)
+    {
+        return $this->plugin_api_manager->removeCallback($event_name, $callback, $priority);
+    }
+
+    /**
+     * Removes an event subscriber.
+     *
+     * The event manager removes the given subscriber from the list of event listeners
+     * for all the events that it wants to listen to.
+     *
+     * @param SubscriberInterface $subscriber SubscriberInterface implementation.
+     */
+    public function removeSubscriber(SubscriberInterface $subscriber)
+    {
+        foreach ($subscriber->getSubscribedEvents() as $event_name => $parameters) {
+            $this->removeSubscriberListener($subscriber, $event_name, $parameters);
+        }
+    }
+
+    /**
+     * Adds the given subscriber listener to the list of event listeners
+     * that listen to the given event.
+     *
+     * @param SubscriberInterface $subscriber SubscriberInterface implementation.
+     * @param string              $event_name Event name.
+     * @param mixed               $parameters Parameters, can be a string, an array or a multidimensional array.
+     */
+    private function addSubscriberListener(SubscriberInterface $subscriber, $event_name, $parameters)
+    {
+        if (is_string($parameters)) {
+            $this->addListener($event_name, [ $subscriber, $parameters ]);
+        } elseif (is_array($parameters) && count($parameters) !== count($parameters, COUNT_RECURSIVE)) {
+            foreach ($parameters as $parameter) {
+                $this->addSubscriberListener($subscriber, $event_name, $parameter);
+            }
+        } elseif (is_array($parameters) && isset($parameters[0])) {
+            $this->addListener($event_name, [ $subscriber, $parameters[0] ], isset($parameters[1]) ? $parameters[1] : 10, isset($parameters[2]) ? $parameters[2] : 1);
+        }
+    }
+
+    /**
+     * Removes the given subscriber listener to the list of event listeners
+     * that listen to the given event.
+     *
+     * @param SubscriberInterface $subscriber SubscriberInterface implementation.
+     * @param string              $event_name Event name.
+     * @param mixed               $parameters Parameters, can be a string, an array or a multidimensional array.
+     */
+    private function removeSubscriberListener(SubscriberInterface $subscriber, $event_name, $parameters)
+    {
+        if (is_string($parameters)) {
+            $this->removeListener($event_name, [ $subscriber, $parameters ]);
+        } elseif (is_array($parameters) && count($parameters) !== count($parameters, COUNT_RECURSIVE)) {
+            foreach ($parameters as $parameter) {
+                $this->removeSubscriberListener($subscriber, $event_name, $parameter);
+            }
+        } elseif (is_array($parameters) && isset($parameters[0])) {
+            $this->removeListener($event_name, [ $subscriber, $parameters[0] ], isset($parameters[1]) ? $parameters[1] : 10);
+        }
+    }
+}

EventManagerAwareSubscriberInterface.php

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+<?php
+/**
+ * Interface for subscribers who need access to the event manager object
+ *
+ * @package WPMedia\EventManager
+ */
+
+namespace WPMedia\EventManager;
+
+interface EventManagerAwareSubscriberInterface extends SubscriberInterface
+{
+    /**
+     * Set the WordPress event manager for the subscriber.
+     *
+     * @param EventManager $event_manager EventManager instance.
+     */
+    public function setEventManager(EventManager $event_manager);
+}

PluginApiManager.php

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+<?php
+/**
+ * Based on https://carlalexander.ca/designing-system-wordpress-event-management/
+ *
+ * @package WPMedia\EventManager
+ */
+
+namespace WPMedia\EventManager;
+
+/**
+ * Wrapper class around the WordPress plugin API
+ */
+class PluginApiManager
+{
+    /**
+     * Adds a callback to a specific hook of the WordPress plugin API.
+     *
+     * @uses add_filter()
+     *
+     * @param string   $hook_name     Name of the hook.
+     * @param callable $callback      Callback function.
+     * @param int      $priority      Priority.
+     * @param int      $accepted_args Number of arguments.
+     */
+    public function addCallback($hook_name, $callback, $priority = 10, $accepted_args = 1)
+    {
+        add_filter($hook_name, $callback, $priority, $accepted_args);
+    }
+
+    /**
+     * Removes the given callback from the given hook. The WordPress plugin API only
+     * removes the hook if the callback and priority match a registered hook.
+     *
+     * @uses remove_filter()
+     *
+     * @param string   $hook_name Hook name.
+     * @param callable $callback  Callback.
+     * @param int      $priority  Priority.
+     *
+     * @return bool
+     */
+    public function removeCallback($hook_name, $callback, $priority = 10)
+    {
+        return remove_filter($hook_name, $callback, $priority);
+    }
+
+    /**
+     * Checks the WordPress plugin API to see if the given hook has
+     * the given callback. The priority of the callback will be returned
+     * or false. If no callback is given will return true or false if
+     * there's any callbacks registered to the hook.
+     *
+     * @uses has_filter()
+     *
+     * @param string $hook_name Hook name.
+     * @param mixed  $callback  Callback.
+     *
+     * @return bool|int
+     */
+    public function hasCallback($hook_name, $callback = false)
+    {
+        return has_filter($hook_name, $callback);
+    }
+
+    /**
+     * Get the name of the hook that WordPress plugin API is executing. Returns
+     * false if it isn't executing a hook.
+     *
+     * @uses current_filter()
+     *
+     * @return string|bool
+     */
+    public function getCurrentHook()
+    {
+        return current_filter();
+    }
+
+    /**
+     * Executes all the callbacks registered with the given hook.
+     *
+     * @uses do_action()
+     */
+    public function execute()
+    {
+        $args = func_get_args();
+        return call_user_func_array('do_action', $args);
+    }
+
+    /**
+     * Filters the given value by applying all the changes from the callbacks
+     * registered with the given hook. Returns the filtered value.
+     *
+     * @uses apply_filters()
+     *
+     * @return mixed
+     */
+    public function filter()
+    {
+        $args = func_get_args();
+        return call_user_func_array('apply_filters', $args);
+    }
+}

SubscriberInterface.php

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+<?php
+/**
+ * Interface for subscribers
+ *
+ * @package WPMedia\EventManager
+ */
+
+namespace WPMedia\EventManager;
+
+/**
+ * A Subscriber knows what specific WordPress events it wants to listen to.
+ *
+ * When an EventManager adds a Subscriber, it gets all the WordPress events that
+ * it wants to listen to. It then adds the subscriber as a listener for each of them.
+ */
+interface SubscriberInterface
+{
+    /**
+     * Returns an array of events that this subscriber wants to listen to.
+     *
+     * The array key is the event name. The value can be:
+     *
+     *  * The method name
+     *  * An array with the method name and priority
+     *  * An array with the method name, priority and number of accepted arguments
+     *  * An array containing arrays following the above patterns
+     *
+     * For instance:
+     *
+     *  * array('event_name' => 'method_name')
+     *  * array('event_name' => array('method_name', $priority))
+     *  * array('event_name' => array('method_name', $priority, $accepted_args))
+     *  * array('event_name' => array(array('method_name_1', $priority_1, $accepted_args_1)), array('method_name_2', $priority_2, $accepted_args_2)))
+     *
+     * @return array
+     */
+    public static function getSubscribedEvents();
+}