<?php
/**
 * Context.php - Helper class to handle the currently selected Stud.IP-object
 *
 * Usage:
 * Context::getId()
 *    -> to retrieve id of current Stud.IP-object
 *
 * Context::isCours()
 *    -> check if context is of type course/seminar
 *
 * Context::get()
 *    -> get sorm-object for current context
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 *
 * @author      Till Glöggler <tgloeggl@uos.de>
 * @license     http://www.gnu.org/licenses/gpl-2.0.html GPL version 2
 * @category    Stud.IP
 */

class Context
{
    /**
     * Constants to check for type of context
     */
    const COURSE    = 'course';
    const INSTITUTE = 'institute';
    const USER      = 'user';

    /**
     * storage for the current context
     */
    private static $context = null;
    private static $type    = null;

    /**
     * Load context for passed id.
     *
     * @param string $id seminar_id, institute_id or user_id
     */
    private static function loadContext($id)
    {
        $possible_sorms = ['Course', 'Institute'];
        foreach($possible_sorms as $sorm) {
            if ($context = $sorm::find($id)) {
                self::$context = $context;
                self::$type    = strtolower($sorm);
            }
        }
    }

    /**
     * Return sorm-object of currently active Stud.IP object
     *
     * @return Course|Institute sorm-object of current context
     */
    public static function get()
    {
        return self::$context;
    }

    /**
     * Return id of currently active Stud.IP object
     *
     * @return string md5-hash
     */
    public static function getId()
    {
        if (!self::$context) {
            return null;
        }

        return self::$context->getId();
    }

    /**
     * Return type of currently active Stud.IP object. To easily check what type
     * of object that is, check the return value against
     * Context::COURSE, Context::INSTITUTE or Context::USER
     *
     * @return mixed one of Context::COURSE, Context::INSTITUTE or Context::USER
     */
    public static function getType()
    {
        return self::$type;
    }

    /**
     * Checks if current context is a seminar
     *
     * @return bool
     */
    public static function isCourse()
    {
        return self::getType() === self::COURSE;
    }

    /**
     * Checks if current context is an institute
     *
     * @return bool
     */
    public static function isInstitute()
    {
        return self::getType() === self::INSTITUTE;
    }

    /**
     * Checks if current context is an user
     *
     * @return bool
     */
    public static function isUser()
    {
        return self::getType() === self::USER;
    }

    /**
     * Get string representation of object-type fpr legacy support
     *
     * @deprecated
     *
     * @return string returns 'sem' or 'inst'
     */
    public static function getClass()
    {
        switch (self::getType()) {
            case self::COURSE:
                return 'sem';

            case self::INSTITUTE:
                return 'inst';
        }

        throw new UnexpectedValueException('Invalid context type');
    }

    /**
     * Get SemClass-number (kind of) for current context. Only works for
     * seminar or institute
     *
     * @deprecated
     *
     * @return int
     */
    public static function getArtNum()
    {
        if (self::isCourse()) {
            return self::get()->status;
        }

        if (self::isInstitute()) {
            return self::get()->type;
        }

        throw new UnexpectedValueException('Invalid context type');
    }

    /**
     * Return human readable text for current context, excluding user
     *
     * @deprecated
     *
     * @return string
     */
    public static function getTypeName()
    {
        switch (self::getType()) {
            case self::COURSE:
                return _('Veranstaltung');

            case self::INSTITUTE:
                return _('Einrichtung');
        }

        throw new UnexpectedValueException('Invalid context type');
    }

    /**
     * Get Fullname of current context, to use it in the context-title
     *
     * @return string or null if no context is available
     */
    public static function getHeaderLine()
    {
        if (!self::$context) {
            return null;
        }
        return self::get()->getFullName();
    }

    /**
     * Set the context to the object denoted by the passed id.
     * Usually there is no need to call this on your own, since seminar_open
     * already does this for you!
     *
     * @param string $id
     *
     * @throws AccessDeniedException|LoginException
     */
    public static function set($id)
    {
        self::close();
        self::loadContext($id);

        if (!self::getType()) {
            return;
        }

        if (self::isCourse() || self::isInstitute()) {
            $GLOBALS['SessionSeminar'] = $id;
        }

        URLHelper::addLinkParam('cid', $GLOBALS['SessionSeminar']);

        $context = self::get();

        if ($context instanceof Course) {
            // check if current user can access the object
            if (!$GLOBALS['perm']->get_studip_perm($context->id)) {
                if ($context->lesezugriff > 0 || !Config::get()->ENABLE_FREE_ACCESS) {
                    // redirect to login page if user is not logged in
                    if (!User::findCurrent()) {
                        throw new LoginException();
                    }

                    if (
                        Request::int('from_short_url')
                        && !$GLOBALS['perm']->get_studip_perm($context->id)
                        && !match_route('dispatch.php/course/details')
                    ) {
                        PageLayout::postWarning(_('Sie sind noch nicht eingetragen. Bitte prüfen Sie eventuell geltende Anmelderegeln!'));
                        $url = URLHelper::getURL(
                            'dispatch.php/course/details',
                            [
                                'sem_id' => $context->id,
                                'from_short_url' => Request::int('from_short_url')
                            ],
                            true
                        );
                        header('Location: ' . $url);
                        die;
                    }
                }
            }

            // if the aux data is forced for this seminar forward all user that havent made an input to this site
            if (
                $context->aux_lock_rule_forced
                && !$GLOBALS['perm']->have_studip_perm('tutor', $context->id)
                && !match_route('dispatch.php/course/members/additional_input')
                && !match_route('dispatch.php/course/change_view/*')
            ) {
                $count = DatafieldEntryModel::countBySql(
                    'range_id = ? AND sec_range_id = ?',
                    [$GLOBALS['user']->id, $context->id]
                );
                if (!$count) {
                    header('Location: ' . URLHelper::getURL('dispatch.php/course/members/additional_input'));
                    sess()->save();
                    die;
                }
            }
        } else if ($context instanceof Institute) {
            // check if current user can access the object
            $no_access = (!Config::get()->ENABLE_FREE_ACCESS ||
                          (Config::get()->ENABLE_FREE_ACCESS == 'courses_only'))
                       && !$GLOBALS['perm']->have_perm('user');

            if ($no_access) {
                // redirect to login page if user is not logged in
                if (!User::findCurrent()) {
                    throw new LoginException();
                }

                if (!$GLOBALS['perm']->have_perm('user')) {
                    throw new AccessDeniedException();
                }
            }

            if (
                !$GLOBALS['perm']->get_studip_perm($context->id)
                && !match_route('dispatch.php/institute/overview')
            ) {
                PageLayout::postWarning(_('Sie sind dieser Einrichtung nicht zugeordnet!'));
                $url = URLHelper::getURL(
                    'dispatch.php/institute/overview',
                    ['cid' => $context->id]
                );
                header('Location: ' . $url);
                die;
            }
        }
    }

    /**
     * "Close" the current context
     */
    public static function close()
    {
        self::$context = null;
        self::$type    = null;

        URLHelper::removeLinkParam('cid');
        unset($GLOBALS['SessionSeminar']);
    }
}