Plugin system - CORE

see shaarli/Shaarli#275

1 files changed, 184 insertions, 0 deletions

diff --git a/application/PluginManager.php b/application/PluginManager.php
new file mode 100644
index 00000000..e572ff7c
--- /dev/null
+++ b/application/PluginManager.php
@@ -0,0 +1,184 @@
+<?php
+
+/**
+ * Class PluginManager
+ *
+ * Use to manage, load and execute plugins.
+ *
+ * Using Singleton design pattern.
+ */
+class PluginManager
+{
+    /**
+     * PluginManager singleton instance.
+     * @var PluginManager $instance
+     */
+    private static $instance;
+
+    /**
+     * List of authorized plugins from configuration file.
+     * @var array $authorizedPlugins
+     */
+    private $authorizedPlugins;
+
+    /**
+     * List of loaded plugins.
+     * @var array $loadedPlugins
+     */
+    private $loadedPlugins = array();
+
+    /**
+     * Plugins subdirectory.
+     * @var string $PLUGINS_PATH
+     */
+    public static $PLUGINS_PATH = 'plugins';
+
+    /**
+     * Private constructor: new instances not allowed.
+     */
+    private function __construct()
+    {
+    }
+
+    /**
+     * Cloning isn't allowed either.
+     *
+     * @return void
+     */
+    private function __clone()
+    {
+    }
+
+    /**
+     * Return existing instance of PluginManager, or create it.
+     *
+     * @return PluginManager instance.
+     */
+    public static function getInstance()
+    {
+        if (!(self::$instance instanceof self)) {
+            self::$instance = new self();
+        }
+
+        return self::$instance;
+    }
+
+    /**
+     * Load plugins listed in $authorizedPlugins.
+     *
+     * @param array $authorizedPlugins Names of plugin authorized to be loaded.
+     *
+     * @return void
+     */
+    public function load($authorizedPlugins)
+    {
+        $this->authorizedPlugins = $authorizedPlugins;
+
+        $dirs = glob(self::$PLUGINS_PATH . '/*', GLOB_ONLYDIR);
+        $dirnames = array_map('basename', $dirs);
+        foreach ($this->authorizedPlugins as $plugin) {
+            $index = array_search($plugin, $dirnames);
+
+            // plugin authorized, but its folder isn't listed
+            if ($index === false) {
+                continue;
+            }
+
+            try {
+                $this->loadPlugin($dirs[$index], $plugin);
+            }
+            catch (PluginFileNotFoundException $e) {
+                error_log($e->getMessage());
+            }
+        }
+    }
+
+    /**
+     * Execute all plugins registered hook.
+     *
+     * @param string $hook   name of the hook to trigger.
+     * @param array  $data   list of data to manipulate passed by reference.
+     * @param array  $params additional parameters such as page target.
+     * 
+     * @return void
+     */
+    public function executeHooks($hook, &$data, $params = array())
+    {
+        if (!empty($params['target'])) {
+            $data['_PAGE_'] = $params['target'];
+        }
+
+        if (isset($params['loggedin'])) {
+            $data['_LOGGEDIN_'] = $params['loggedin'];
+        }
+
+        foreach ($this->loadedPlugins as $plugin) {
+            $hookFunction = $this->buildHookName($hook, $plugin);
+
+            if (function_exists($hookFunction)) {
+                $data = call_user_func($hookFunction, $data);
+            }
+        }
+    }
+
+    /**
+     * Load a single plugin from its files.
+     * Add them in $loadedPlugins if successful.
+     *
+     * @param string $dir        plugin's directory.
+     * @param string $pluginName plugin's name.
+     *
+     * @return void
+     * @throws PluginFileNotFoundException - plugin files not found.
+     */
+    private function loadPlugin($dir, $pluginName)
+    {
+        if (!is_dir($dir)) {
+            throw new PluginFileNotFoundException($pluginName);
+        }
+
+        $pluginFilePath = $dir . '/' . $pluginName . '.php';
+        if (!is_file($pluginFilePath)) {
+            throw new PluginFileNotFoundException($pluginName);
+        }
+
+        include_once $pluginFilePath;
+
+        $this->loadedPlugins[] = $pluginName;
+    }
+
+    /**
+     * Construct normalize hook name for a specific plugin.
+     *
+     * Format:
+     *      hook_<plugin_name>_<hook_name>
+     *
+     * @param string $hook       hook name.
+     * @param string $pluginName plugin name.
+     *
+     * @return string - plugin's hook name.
+     */
+    public function buildHookName($hook, $pluginName)
+    {
+        return 'hook_' . $pluginName . '_' . $hook;
+    }
+}
+
+/**
+ * Class PluginFileNotFoundException
+ *
+ * Raise when plugin files can't be found.
+ */
+class PluginFileNotFoundException extends Exception
+{
+    /**
+     * Construct exception with plugin name.
+     * Generate message.
+     *
+     * @param string $pluginName name of the plugin not found
+     */
+    public function __construct($pluginName)
+    {
+        $this->message = 'Plugin "'. $pluginName .'" files not found.';
+    }
+}
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