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<?php
/**
 * icms_Event class definition
 *
 * @category    ICMS
 *
 * @copyright   The ImpressCMS Project <http://www.impresscms.org>
 * @license     http://www.gnu.org/licenses/old-licenses/gpl-2.0.html GNU General Public License (GPL)
 * @version     SVN: $Id$
 */

class icms_Event {
    /**
     * Registered event handlers
     * @var array
     */
    static protected $handlers = array();
    /**
     * Events currently being processed
     * @var array
     */
    static protected $events = array();

    /**
     * Returns information about a fired event.
     * @param int $index 0 for current, 1 for parent (if current event due to another event), and so on...
     * @return icms_Event
     */
    static public function current($index = 0) {
        return isset(self::$events[$index]) ? self::$events[$index] : false;
    }

    /**
     * Registers an event handler
     *
     * icms_Event::attach( 'icms_db_IConnection', 'connect', 'something' );
     * => will call something( $eventParams, $event ) when the event is fired
     * icms_Event::attach( 'icms_db_IConnection', 'connect', array( $object, 'something' ) );
     * => will call $object->something( $eventParams, $event ) when the event is fired
     * icms_Event::attach( 'icms_db_IConnection', '*', array( 'MyClass', 'something' ) );
     * => will call MyClass::something( $eventParams, $event ) when any event that
     * belongs to the 'icms_db_IConnection' namespace is fired
     * Also, on PHP 5.3+, you can use closures:
     * icms_Event::attach( 'icms_db_IConnection', 'execute', function ( $params, $event ) {
     *    echo 'Executing: ' . $params['sql'];
     * } );
     *
     * @param string $namespace Event namespace
     * @param string $name Event name (use * to attach to all signals of $namespace)
     * @param mixed $callback
     * @return void
     */
    static public function attach($namespace, $name, $callback) {
        if (!isset(self::$handlers[$namespace][$name])) {
            self::$handlers[$namespace][$name] = array();
        }
        self::$handlers[$namespace][$name][] = $callback;
    }
    /**
     * Detach the specified event handler.
     * @param string $namespace
     * @param string $name
     * @param mixed $callback
     */
    static public function detach($namespace, $name, $callback) {
        if (isset(self::$handlers[$namespace][$name])) {
            foreach (self::$handlers[$namespace][$name] as $k => $handler) {
                if ($handler === $callback) {
                    unset(self::$handlers[$namespace][$name][$k]);
                    return;
                }
            }
        }
    }

    /**
     * Triggers an event.
     *
     * @param string $namespace Event namespace
     * @param string $name Event name (use * to attach to all events of $namespace)
     * @param object $source Object that triggered this event
     * @param array $parameters Event parameters
     * @return icms_Event
     */
    static public function trigger($namespace, $name, $source, $parameters = array()) {
        $cancancel = false;
        if (substr($name, 0, 1) == "*") {
            $cancancel = true;
            $name = substr($name, 1);
        }
        $event = new icms_Event($namespace, $name, $source, $parameters, $cancancel);
        array_unshift(self::$events, $event);
        foreach (array("*", $name) as $handlers) {
            if (isset(self::$handlers[$namespace][$handlers])) {
                foreach (self::$handlers[$namespace][$handlers] as $callback) {
                    call_user_func($callback, $parameters, $event);
                    if ($cancancel && $event->canceled) break 2;
                }
            }
        }
        return array_shift(self::$events);
    }

    /**
     * Namespace this event belongs to.
     * @var string
     * @readonly
     */
    public $namespace = "";

    /**
     * Name of this event
     * @var string
     * @readonly
     */
    public $name = "";

    /**
     * Object that fired this event.
     * @var object
     * @readonly
     */
    public $source;

    /**
     * Parameters
     * @var array()
     * @readonly
     */
    public $parameters = array();

    /**
     * Whether this event can be canceled or not.
     * @var bool
     * @readonly
     */
    public $canCancel = false;

    /**
     * Whether this event has been canceled or not.
     * @var bool
     */
    public $canceled = false;

    public function __construct($namespace, $name, $source, $params = array(), $canCancel = false) {
        $this->namespace = $namespace;
        $this->name = $name;
        $this->source = $source;
        $this->parameters = $params;
        $this->canCancel = $canCancel;
    }
}