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<?php
/*
 +--------------------------------------------------------------------------+
 | This file is part of the Kolab Web Admin Panel                           |
 |                                                                          |
 | Copyright (C) 2011-2012, Kolab Systems AG                                |
 |                                                                          |
 | This program is free software: you can redistribute it and/or modify     |
 | it under the terms of the GNU Affero General Public License as published |
 | by the Free Software Foundation, either version 3 of the License, or     |
 | (at your option) any later version.                                      |
 |                                                                          |
 | This program is distributed in the hope that it will be useful,          |
 | but WITHOUT ANY WARRANTY; without even the implied warranty of           |
 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the             |
 | GNU Affero General Public License for more details.                      |
 |                                                                          |
 | You should have received a copy of the GNU Affero General Public License |
 | along with this program. If not, see <http://www.gnu.org/licenses/>      |
 +--------------------------------------------------------------------------+
 | Author: Daniel Hoffend <dh@dotlan.net>                                   |
 +--------------------------------------------------------------------------+
*/

class kolab_hooks {

    /**
     * contains all registeres callbacks
     *
     * @var array
     */
    private static $handlers = array();

    /**
     * contains the list of current executions, used for loop prevention
     */
    private static $stack = array();

    /**
     * initialize the hook system
     * if kolab_wap.custom_hooks is set an points to a custom php file
     * it will be included
     *
     * example:
     * [kolab_wap]
     * custom_hooks = /etc/kolab/hooks.php
     *
     * @static
     */
    public static function init()
    {
        $config = Conf::get_instance();
        $hooks = $config->get('kolab_wap', 'custom_hooks');
        if ($hooks && is_readable($hooks)) {
            Log::debug(__METHOD__.'() Loading '.$hooks);
            require_once($hooks);
        }
    }

    /**
     * check if callbacks are registered for a given hook
     *
     * @static
     * @param string $hook Hook name
     * @return bool
     */
    public static function exists($hook)
    {
        return isset(self::$handlers[$hook])
            && is_array(self::$handlers[$hook])
            && count(self::$handlers[$hook]);
    }

    /**
     * register a callback function for a certain hook
     *
     * @static
     * @param string $hook Hook name
     * @param function|string $callback function/closure, function string or array($obj, 'method')
     */
    public static function register($hook, $callback)
    {
        // if callable, register it
        if (is_callable($callback)) {
            self::$handlers[$hook][] = $callback;

        }

        // otherwise Log error
        else {
            Log::error('could not register callback for hook: '.$hook,$callback);
        }
    }

    /**
     * unregister a callback function for a certain hook
     *
     * @static
     * @param string $hook Hook name
     * @param function|string $callback function/closure, function string or array($obj, 'method')
     */
    public static function unregister($hook, $callback)
    {
        $callback_id = array_search($callback, (array) self::$handlers[$hook]);
        if ($callback_id !== false) {
            array_splice(self::$handlers[$hook], $callback_id, 1);
        }
    }


    /**
     * execute a hook and return the 'modified' or 'enhanced' arguments'
     *
     * @static
     * @param string $hook Hook Name
     * @param array $args given arguments to work with
     * @return array $args
     */
    public static function run($hook, array $args = array())
    {
        if (in_array($hook, self::$stack)) {
            Log::warning(__METHOD__.' possible recursion in execution of hook: '.$hook);
        }

        array_push(self::$stack, $hook);

        // Use for loop here, so handlers added in the hook will be executed too
        Log::trace(__METHOD__.' execute '.count(self::$handlers[$hook]).' hook(s) for '.$hook);
        for ($i = 0; $i < count(self::$handlers[$hook]); $i++) {
            Log::trace(__METHOD__.' execute hook['.$i.'] for '.$hook, self::$handlers[$hook][$i]);
            $ret = call_user_func(self::$handlers[$hook][$i], $args);
            if ($ret && is_array($ret)) {
                $args = $ret + $args;
            }

            if ($args['break']) {
                break;
            }
        }

        array_pop(self::$stack);
        return $args;
    }

}