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<?php
/*
 * File: ratatoeskr/sys/urlprocess.php
 *
 * Providing functions / classes to handle URLs
 *
 * License:
 * This file is part of Ratatöskr.
 * Ratatöskr is licensed unter the MIT / X11 License.
 * See "ratatoeskr/licenses/ratatoeskr" for more information.
 */

/*
 * Function: url_action_simple
 * Generate an action in a more simple way.
 *
 * Parameters:
 *  $function - A callback that gets the $data var as an input and returns the new $data var. Can throw an <Redirect> Exception.
 *
 * Returns:
 *  A callback that can be used as an url action.
 */
function url_action_simple($function)
{
    return function(&$data, $url_now, &$url_next) use ($function)
    {
        try
        {
            $data = call_user_func($function, $data);
            $url_next = array();
        }
        catch(Redirect $e)
        {
            $url_next = $e->nextpath;
        }
    };
}

/*
 * Function: url_action_subactions
 * Generate an action that contains subactions. Subactions can redirect to ".." to go to the level above.
 *
 * Parameters:
 *  $actions - Associative array of actions.
 *
 * Returns:
 *  A callback that can be used as an url action.
 */
function url_action_subactions($actions)
{
    return function(&$data, $url_now, &$url_next) use ($actions)
    {
        $result = url_process($url_next, $actions, $data);
        if($result !== NULL)
            $url_next = $result;
        else
            $url_next = array();
    };
}

/*
 * Function: url_action_alias
 * Generate an action that is an alias for another one (i.e. redirects).
 *
 * Parameters:
 *  $for - Path (array) of the action this one should be an alias of.
 *
 * Returns:
 *  A callback that can be used as an url action.
 */
function url_action_alias($for)
{
    return function(&$data, $url_now, &$url_next) use($for)
    {
        $url_next = array_merge($for, $url_next);
    };
}

/*
 * Function: url_process
 * Choose an appropiate action for the given URL.
 *
 * Parameters:
 *  $url - Either an array containing the URL components or the URL (both relative).
 *  $actions - Associative array of actions.
 *             Key is the name (anything alphanumeric, should usually not start with '_', reserved for special URL names, see beneath).
 *             Value is a callback of the form: function(&$data, $url_now, &$url_next). $data can be used for shared data between subactions. $url_next can be modified in order to redirect to another action / stop the routing.
 *
 * Special actions:
 *  _index - If name is empty, the index will be called.
 *  _default - If nothing was found, this is the default.
 *  _notfound - If not even _default exists or NotFoundError was thrown.
 *  _prelude - If existant, will be executed before everything else.
 *  _epilog - If existant, will be executed after evrything else.
 */
function url_process($url, $actions, &$data)
{
    $epilog_running = 0;
    if(is_string($url))
        $url = explode("/", $url);
    $url = array_filter($url, function($x) { return !empty($x); });
    if(count($url) == 0)
        $url = array("_index");

    if(isset($actions["_prelude"]))
        $url = array_merge(array("_prelude"), $url);

    $url_now  = $url[0];
    $url_next = array_slice($url, 1);

    while(is_string($url_now) and ($url_now != "") and ($url_now != ".."))
    {
        $cb = NULL;
        if(empty($url_now))
            $url_now = "_index";
        if(isset($actions[$url_now]))
            $cb = $actions[$url_now];
        else if(isset($actions["_default"]))
            $cb = $actions["_default"];
        else if(isset($actions["_notfound"]))
            $cb = $actions["_notfound"];
        else
            throw new NotFoundError();

        try
        {
            call_user_func_array($cb, array(&$data, $url_now, &$url_next));
        }
        catch(NotFoundError $e)
        {
            if(isset($actions["_notfound"]))
                $url_next = array("_notfound");
            else
                throw $e;
        }

        if(count($url_next) > 0)
        {
            $url_now  = $url_next[0];
            $url_next = array_slice($url_next, 1);
        }
        else if(isset($actions["_epilog"]) and ($epilog_running <= 0))
        {
            $epilog_running = 2;
            $url_now        = "_epilog";
        }
        else
            $url_now = "";

        --$epilog_running;
    }

    if($url_now == "..")
        return $url_next;
    else
        return NULL;
}

/*
 * Class: Redirect
 * Exception that can be thrown inside an <url_action_simple>.
 * throw new Redirect(array("..", "foo")); will redirect to "../foo" and won't touch $data.
 */
class Redirect extends Exception
{
    public $nextpath;
    public function __construct($nextpath)
    {
        $this->nextpath = $nextpath;
        parent::__construct();
    }
}
/*
 * Class: NotFoundError
 * An Exception
 */
class NotFoundError extends Exception { }

?>