convert old core plugins to new model, re #814

Merge request studip/studip!440

14 files changed, 2752 insertions, 8 deletions

diff --git a/lib/classes/ForumAbo.php b/lib/classes/ForumAbo.php
new file mode 100644
index 0000000..fa84a48
--- /dev/null
+++ b/lib/classes/ForumAbo.php
@@ -0,0 +1,186 @@
+<?php
+
+/**
+ * ForumAbo.php - Handle abonnements of areas/threads or even the whole forum
+ *
+ * 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 3 of
+ * the License, or (at your option) any later version.
+ *
+ * @author      Till Glöggler <tgloeggl@uos.de>
+ * @license     http://www.gnu.org/licenses/gpl-3.0.html GPL version 3
+ * @category    Stud.IP
+ */
+
+class ForumAbo
+{
+    /**
+     * add the passed user as a watcher for the passed topic (including all
+     * current and future childs)
+     *
+     * @param string $topic_id
+     * @param string $user_id
+     */
+    public static function add($topic_id, $user_id = null)
+    {
+        if (!$user_id) $user_id = $GLOBALS['user']->id;
+
+        $stmt = DBManager::get()->prepare("REPLACE INTO forum_abo_users
+            (topic_id, user_id) VALUEs (?, ?)");
+        $stmt->execute([$topic_id, $user_id]);
+    }
+
+    /**
+     * remove the passed user as a watcher from the passed topic (including all
+     * current and future childs)
+     *
+     * @param string $topic_id
+     * @param string $user_id
+     */
+    public static function delete($topic_id, $user_id = null)
+    {
+        if (!$user_id) $user_id = $GLOBALS['user']->id;
+
+        $stmt = DBManager::get()->prepare("DELETE FROM forum_abo_users
+            WHERE topic_id = ? AND user_id = ?");
+        $stmt->execute([$topic_id, $user_id]);
+    }
+
+    /**
+     * check, if the passed user watches the passed topic. If no user_id is passed,
+     * the currently logged in user is used
+     *
+     * @param string $topic_id
+     * @param string $user_id
+     *
+     * @return boolean returns true if user is watching, false otherwise
+     */
+    public static function has($topic_id, $user_id = null)
+    {
+        if (!$user_id) $user_id = $GLOBALS['user']->id;
+
+        $stmt = DBManager::get()->prepare("SELECT COUNT(*) FROM forum_abo_users
+            WHERE topic_id = ? AND user_id = ?");
+        $stmt->execute([$topic_id, $user_id]);
+
+        return $stmt->fetchColumn() > 0 ? true : false;
+    }
+
+    /**
+     * send out the notification messages for the passed topic. The contents
+     * and a link directly to the topic are added to the message.
+     *
+     * @param string $topic_id
+     */
+    public static function notify($topic_id)
+    {
+        // send message to all abo-users
+        $db = DBManager::get();
+        $messaging = new ForumBulkMail();
+        // $messaging = new Messaging();
+
+        // get all parent topic-ids, to find out which users to notify
+        $path = ForumEntry::getPathToPosting($topic_id);
+
+        // fetch all users to notify, exclude current user
+        $stmt = $db->prepare("SELECT DISTINCT user_id
+            FROM forum_abo_users
+            WHERE topic_id IN (:topic_ids)
+                AND user_id != :user_id");
+        $stmt->bindParam(':topic_ids', array_keys($path), StudipPDO::PARAM_ARRAY);
+        $stmt->bindParam(':user_id', $GLOBALS['user']->id);
+        $stmt->execute();
+
+        // get details for topic
+        $topic = ForumEntry::getConstraints($topic_id);
+
+        $template = $GLOBALS['template_factory']->open('mail/forum_notification');
+
+        // notify users
+        while ($data = $stmt->fetch(PDO::FETCH_ASSOC)) {
+            $user_id = $data['user_id'];
+
+            // don't notify user if view permission is not granted
+            if (!ForumPerm::has('view', $topic['seminar_id'], $user_id)) {
+                continue;
+            }
+
+            $user = User::find($user_id);
+
+            // check if user wants an email for all or selected messages only
+            $force_email = false;
+            if ($messaging->user_wants_email($user_id)) {
+                $force_email = true;
+            }
+            // do not send mails when account is locked or expired
+            $expiration = UserConfig::get($user->id)->EXPIRATION_DATE;
+            if ($user->locked || ($expiration > 0 && $expiration < time())) {
+                $force_email = false;
+            }
+            $parent_id = ForumEntry::getParentTopicId($topic['topic_id']);
+
+            setTempLanguage($data['user_id']);
+            $notification = sprintf(_("%s hat einen Beitrag geschrieben"), ($topic['anonymous'] ? _('Anonym') : $topic['author']));
+            restoreLanguage();
+
+            PersonalNotifications::add(
+                $user_id,
+                URLHelper::getURL(
+                    'dispatch.php/course/forum/index/index/' . $topic['topic_id'] . '#' . $topic['topic_id'],
+                    ['cid' => $topic['seminar_id']],
+                    true
+                ),
+                $notification,
+                "forumposting_" . $topic['topic_id'],
+                Icon::create('forum', 'clickable')
+            );
+
+            if ($force_email) {
+                $title = implode(' >> ', ForumEntry::getFlatPathToPosting($topic_id));
+
+                $subject = _('[Forum]') . ' ' . ($title ?: _('Neuer Beitrag'));
+
+                $htmlMessage = $template->render(
+                    compact('user_id', 'topic', 'path')
+                );
+
+                $textMessage = trim(kill_format($htmlMessage));
+
+                $userWantsHtml = UserConfig::get($user_id)->MAIL_AS_HTML;
+
+                StudipMail::sendMessage(
+                    $user->email,
+                    $subject,
+                    $textMessage,
+                    $userWantsHtml ? $htmlMessage : null
+                );
+            }
+        }
+
+        $messaging->bulkSend();
+    }
+
+    /**
+     * Removes all abos for a given course and user
+     *
+     * @param String $course_id Id of the course
+     * @param String $user_id   Id of the user
+     * @return int number of removed abos
+     */
+    public static function removeForCourseAndUser($course_id, $user_id)
+    {
+        $query = "DELETE FROM `forum_abo_users`
+                  WHERE `user_id` = :user_id
+                  AND `topic_id` IN (
+                      SELECT `topic_id`
+                      FROM `forum_entries`
+                      WHERE `seminar_id` = :course_id
+                  )";
+        $statement = DBManager::get()->prepare($query);
+        $statement->bindValue(':course_id', $course_id);
+        $statement->bindValue(':user_id', $user_id);
+        $statement->execute();
+        return $statement->rowCount();
+    }
+}
diff --git a/lib/classes/ForumActivity.php b/lib/classes/ForumActivity.php
new file mode 100644
index 0000000..20ebeb6
--- /dev/null
+++ b/lib/classes/ForumActivity.php
@@ -0,0 +1,149 @@
+<?php
+/**
+ * File - description
+ *
+ * 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     https://www.gnu.org/licenses/gpl-2.0.html GPL version 2
+ */
+
+class ForumActivity
+{
+    /**
+     * Post activity for new forum post
+     *
+     * @param string $event
+     * @param string $topic_id
+     * @param array $post
+     */
+    public static function newEntry($event, $topic_id, $post)
+    {
+        $verb = $post['depth'] == 3 ? 'answered' : 'created';
+
+        if ($verb == 'created') {
+            if ($post['depth'] == 1) {
+                $summary = _('%s hat im Forum der Veranstaltung "%s" einen Bereich erstellt.');
+            } else {
+                $summary = _('%s hat im Forum der Veranstaltung "%s" ein Thema erstellt.');
+            }
+        } else {
+            $summary = _('%s hat im Forum der Veranstaltung "%s" auf ein Thema geantwortet.');
+        }
+
+        self::post($post, $verb, $summary);
+    }
+
+    /**
+     * Post activity for updating a forum post
+     * @param string $event
+     * @param string $topic_id
+     * @param string $post
+     */
+    public static function updateEntry($event, $topic_id, $post)
+    {
+        $summary = _('%s hat im Forum der Veranstaltung "%s" einen Beitrag editiert.');
+
+        if ($post['user_id'] == $GLOBALS['user']->id) {
+            $content = sprintf(
+                _('%s hat seinen eigenen Beitrag vom %s editiert.'),
+                self::getPostUsername($post),
+                date('d.m.y, H:i', $post['mkdate'])
+            );
+        } else {
+            $content = sprintf(
+                _('%s hat den Beitrag von %s vom %s editiert.'),
+                get_fullname($GLOBALS['user']->id),
+                self::getPostUsername($post),
+                date('d.m.y, H:i', $post['mkdate'])
+            );
+        }
+
+        self::post($post, 'edited', $summary, $content);
+    }
+
+    /**
+     * Post activity for deleting a forum post
+     * $param string $event
+     * @param string $topic_id
+     * @param string $post
+     */
+    public static function deleteEntry($event, $topic_id, $post)
+    {
+        // Remove all previous activities for the post
+        Studip\Activity\Activity::deleteBySQL(
+            "provider = ? AND object_type = 'forum' AND object_id = ?",
+            [Studip\Activity\ForumProvider::class, $topic_id]
+        );
+
+        $summary = _('%s hat im Forum der Veranstaltung "%s" einen Beitrag gelöscht.');
+
+        if ($post['user_id'] == $GLOBALS['user']->id) {
+            $content = sprintf(
+                _('%s hat seinen Beitrag vom %s gelöscht.'),
+                self::getPostUsername($post),
+                date('d.m.y, H:i', $post['mkdate'])
+            );
+        } else {
+            $content = sprintf(
+                _('%s hat den Beitrag von %s vom %s gelöscht.'),
+                get_fullname($GLOBALS['user']->id),
+                self::getPostUsername($post),
+                date('d.m.y, H:i', $post['mkdate'])
+            );
+        }
+
+        self::post($post, 'deleted', $summary, $content);
+    }
+
+    private static function post($post, $verb, $summary, $content = null)
+    {
+        // skip system-created entries like "Allgemeine Diskussionen"
+        if (!$post['user_id']) {
+            return;
+        }
+
+        $range_id = $post['seminar_id'];
+        $type     = get_object_type($range_id);
+
+        $obj = get_object_name($range_id, $type);
+
+        $data = [
+            'provider'     => 'Studip\Activity\ForumProvider',
+            'context'      => $type === 'sem' ? 'course' : 'institute',
+            'context_id'   => $post['seminar_id'],
+            'content'      => null,
+            'actor_type'   => 'user',             // who initiated the activity?
+            'actor_id'     => $post['user_id'],   // id of initiator
+            'verb'         => $verb,              // the activity type
+            'object_id'    => $post['topic_id'],  // the id of the referenced object
+            'object_type'  => 'forum',            // type of activity object
+            'mkdate'       => $post['mkdate'] ?: time()
+        ];
+
+        if ($post['anonymous']) {
+            $data['actor_type'] = 'anonymous';
+            $data['actor_id']   = '';
+        }
+
+        $activity = Studip\Activity\Activity::create($data);
+    }
+
+    /**
+     * Returns the poster's name for a forum post.
+     *
+     * @param array $post
+     * @return string
+     */
+    private static function getPostUsername($post)
+    {
+        if ($post['anonymous']) {
+            return _('Anonym');
+        }
+
+        return get_fullname($post['user_id']);
+    }
+}
diff --git a/lib/classes/ForumBulkMail.php b/lib/classes/ForumBulkMail.php
new file mode 100644
index 0000000..ec18de9
--- /dev/null
+++ b/lib/classes/ForumBulkMail.php
@@ -0,0 +1,135 @@
+<?php
+/**
+ * ForumBulkMail.php - Experimental mailer to handle large amounts of mails at high speed
+ *
+ * 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 3 of
+ * the License, or (at your option) any later version.
+ *
+ * @author      Till Glöggler <tgloeggl@uos.de>
+ * @license     http://www.gnu.org/licenses/gpl-3.0.html GPL version 3
+ * @category    Stud.IP
+ */
+
+class ForumBulkMail extends Messaging {
+    var $bulk_mail;
+
+    /**
+     * Overwrites the parent method. This method combines messages with the same
+     * content and prepares them for sending them as a mail with multiple
+     * recepients instead of one mail for each recipient.
+     * The actual sending task is done bulkSend().
+     *
+     * @global object $user
+     *
+     * @param string $rec_user_id  user_id of recipient
+     * @param string $snd_user_id  user_id of sender
+     * @param string $message      the message
+     * @param string $subject      subject for the message
+     * @param string $message_id   the message_id in the database
+     */
+    function sendingEmail($rec_user_id, $snd_user_id, $message, $subject, $message_id)
+    {
+        $receiver = User::find($rec_user_id);
+
+        if ($receiver && $receiver->email) {
+            $rec_fullname = 'Sie';
+
+            setTempLanguage($receiver->id);
+
+            if (empty($this->bulk_mail[md5($message)][getenv('LANG')])) {
+
+                $title = "[Stud.IP - " . Config::get()->UNI_NAME_CLEAN . "] ".stripslashes(kill_format(str_replace(["\r","\n"], '', $subject)));
+
+                if ($snd_user_id != "____%system%____") {
+                    $sender = User::find($snd_user_id);
+                    $reply_to = $sender->email;
+                }
+
+                $template = $GLOBALS['template_factory']->open('mail/text');
+                $template->message      = kill_format(stripslashes($message));
+                $template->rec_fullname = $receiver->getFullname();
+                $mailmessage = $template->render();
+
+                $template = $GLOBALS['template_factory']->open('mail/html');
+                $template->lang         = getUserLanguagePath($rec_user_id);
+                $template->message      = stripslashes($message);
+                $template->rec_fullname = $receiver->getFullname();
+                $mailhtml = $template->render();
+
+                $this->bulk_mail[md5($message)][getenv('LANG')] = [
+                    'text'       => $mailmessage,
+                    'html'       => $mailhtml,
+                    'title'      => $title,
+                    'reply_to'   => $reply_to,
+                    'message_id' => $message_id,
+                    'users'      => []
+                ];
+            }
+
+            $this->bulk_mail[md5($message)][getenv('LANG')]['users'][$receiver->id] = $receiver->email;
+
+            restoreLanguage();
+        }
+    }
+
+
+    /**
+     * Sends the collected messages from sendingMail as e-mail.
+     */
+    function bulkSend()
+    {
+        // if nothing to do, return
+        if (empty($this->bulk_mail)) return;
+
+        // send a mail, for each language one
+        foreach ($this->bulk_mail as $lang_data) {
+            foreach ($lang_data as $data) {
+                $mail = new StudipMail();
+                $mail->setSubject($data['title']);
+
+                foreach ($data['users'] as $user_id => $to) {
+                    $mail->addRecipient($to, get_fullname($user_id), 'Bcc');
+                }
+
+                $mail->setReplyToEmail('')
+                ->setBodyText($data['text']);
+
+                if (mb_strlen($data['reply_to'])) {
+                    $mail->setSenderEmail($data['reply_to'])
+                         ->setSenderName($snd_fullname);
+                }
+
+                $user_cfg = UserConfig::get($user_id);
+                if ($user_cfg->getValue('MAIL_AS_HTML')) {
+                    $mail->setBodyHtml($mailhtml);
+                }
+
+                if($GLOBALS["ENABLE_EMAIL_ATTACHMENTS"]){
+                    $message = Message::find($data['message_id']);
+
+                    $current_user = User::findCurrent();
+
+                    $message_folder = MessageFolder::findMessageTopFolder(
+                        $message->id,
+                        $current_user->id
+                    );
+
+                    $message_folder = $message_folder->getTypedFolder();
+
+                    $attachments = FileManager::getFolderFilesRecursive(
+                        $message_folder,
+                        $current_user->id
+                    );
+
+
+                    foreach($attachments as $attachment) {
+                        $mail->addStudipAttachment($attachment);
+                    }
+                }
+                $mail->send();
+            }
+        }
+    }
+}
diff --git a/lib/classes/ForumEntry.php b/lib/classes/ForumEntry.php
new file mode 100644
index 0000000..bd62b08
--- /dev/null
+++ b/lib/classes/ForumEntry.php
@@ -0,0 +1,1385 @@
+<?php
+/**
+ * ForumEntry.php - Allows the retrieval and handling of forum-entrys
+ *
+ * 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 3 of
+ * the License, or (at your option) any later version.
+ *
+ * @author      Till Glöggler <tgloeggl@uos.de>
+ * @license     http://www.gnu.org/licenses/gpl-3.0.html GPL version 3
+ * @category    Stud.IP
+ */
+
+class ForumEntry  implements PrivacyObject
+{
+    const WITH_CHILDS = true;
+    const WITHOUT_CHILDS = false;
+    const THREAD_PREVIEW_LENGTH = 100;
+    const POSTINGS_PER_PAGE = 10;
+    const FEED_POSTINGS = 100;
+
+
+    /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+     * H   E   L   P   E   R   -   F   U   N   C   T   I   O   N   S *
+     * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+    /**
+     * is used for posting-preview. replaces all newlines with spaces
+     *
+     * @param string $text the text to work on
+     * @returns string
+     */
+    public static function br2space($text)
+    {
+        return str_replace("\n", ' ', str_replace("\r", '', $text));
+    }
+
+    /**
+     * remove the edit-html from a posting
+     *
+     * @param string $description the posting-content
+     * @return string the content stripped by the edit-mark
+     */
+    public static function killEdit($description)
+    {
+        // wurde schon mal editiert
+        if (preg_match('/^(.*)(<admin_msg.*?)$/s', $description, $match)) {
+            return $match[1];
+        }
+        return $description;
+    }
+
+    /**
+     * add the edit-html to a posting
+     *
+     * @param string $description the posting-content
+     * @return string the content with the edit-mark
+     */
+    public static function appendEdit($description)
+    {
+        $edit = "<admin_msg autor=\"" . addslashes(get_fullname()) . "\" chdate=\"" . time() . "\">";
+        return $description . $edit;
+    }
+
+    /**
+     * convert the edit-html to raw text
+     *
+     * @param string $description the posting-content
+     * @return string the content with the raw text version of the edit-mark
+     */
+    public static function parseEdit($description, $anonymous = false)
+    {
+        // TODO figure out if this function can be removed
+        //      has been replaced with getContentAsHTML in core code
+        $content = ForumEntry::killEdit($description);
+        $comment = ForumEntry::getEditComment($description, $anonymous);
+        return $content . ($comment ? "\n\n%%" . $comment .'%%' : '');
+    }
+
+    /**
+     * Get content with appended edit comment as HTML.
+     *
+     * @param string  $description  Database entry of forum entry's body.
+     * @param bool    $anonymous    True, if only root is allowed to see
+     *                              authors.
+     * @return string  Content and edit comment as HTML.
+     */
+    public static function getContentAsHtml($description, $anonymous = false)
+    {
+        $raw_content = ForumEntry::killEdit($description);
+
+        $comment = ForumEntry::getEditComment($description, $anonymous);
+        $content = formatReady($raw_content);
+
+        if ($comment) {
+            $content .= '<br><em>' . htmlReady($comment) . '</em>';
+        }
+
+        return $content;
+    }
+
+    /**
+     * Get author and time of an edited forum entry as a string.
+     *
+     * @param string  $description  Database entry of forum entry's body.
+     * @param bool    $anonymous    True, if only root is allowed to see
+     *                              authors.
+     * @return string  Author and time or empty string if not edited.
+     */
+    public static function getEditComment($description, $anonymous = false)
+    {
+        $info = ForumEntry::getEditInfo($description);
+        if ($info) {
+            $root = $GLOBALS['perm']->have_perm('root');
+            $author = ($anonymous && !$root) ? _('Anonym') : $info['author'];
+            $time = date('d.m.y - H:i', $info['time']);
+            return '[' . _('Zuletzt editiert von') . " $author - $time]";
+        }
+        return '';
+    }
+
+    /**
+     * Get author and time of an edited forum entry.
+     *
+     * @param string  $description  Database entry of forum entry's body.
+     * @return array    Associative array containing author and time.
+     *         boolean  False if edit tag was not found.
+     */
+    public static function getEditInfo($description) {
+        if (preg_match('/<admin_msg autor="([^"]*)" chdate="([^"]*)">\s*$/i', $description, $matches)) {
+            // wurde schon mal editiert
+            return ['author' => $matches[1], 'time' => $matches[2]];
+        }
+        return false;
+    }
+
+    /**
+     * Remove all quote blocks AND the quoted text from a forum post.
+     *
+     * @param String $string The string to remove the quote blocks from
+     * @return String the posting without the [quote]-blocks (not just tags!)
+     */
+    public static function removeQuotes($description)
+    {
+        if (Studip\Markup::isHtml($description)) {
+            // remove all blockquote tags
+            $dom = new DOMDocument();
+            $dom->loadHtml($description, LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD);
+            $nodes = iterator_to_array($dom->getElementsByTagName('blockquote'));
+
+            foreach ($nodes as $node) {
+                $node->parentNode->removeChild($node);
+            }
+
+            return $dom->saveHTML();
+        } else {
+            $description = preg_replace('/\[quote(=.*)\].*\[\/quote\]/isU', '', $description);
+            $description = str_replace('[/quote]', '', $description);
+        }
+        return $description;
+    }
+
+
+    /**
+     * calls Stud.IP's kill_format and additionally removes any found smiley-tag
+     *
+     * @param string $text the text to parse
+     * @return string the text without format-tags and without smileys
+     */
+    public static function killFormat($text)
+    {
+        $text = kill_format($text);
+
+        // find stuff which is enclosed between to colons
+        preg_match('/' . SmileyFormat::REGEXP . '/U', $text, $matches);
+
+        // remove the match if it is a smiley
+        foreach ($matches as $match) {
+            if (Smiley::getByName($match) || Smiley::getByShort($match)) {
+                $text = str_replace($match, '', $text);
+            }
+        }
+
+        return $text;
+    }
+
+    /**
+     * returns the entry for the passed topic_id
+     *
+     * @param  string  $topic_id
+     * @return array   array('lft' => ..., 'rgt' => ..., seminar_id => ...)
+     *
+     * @throws Exception
+     */
+    public static function getConstraints($topic_id)
+    {
+        //very bad performance if topic_id is 0 or false
+        if (!$topic_id) return false;
+
+        // look up the range of postings
+        $range_stmt = DBManager::get()->prepare("SELECT *
+            FROM forum_entries WHERE topic_id = ?");
+        $range_stmt->execute([$topic_id]);
+        if (!$data = $range_stmt->fetch(PDO::FETCH_ASSOC)) {
+            return false;
+            // throw new Exception("Could not find entry with id >>$topic_id<< in forum_entries, " . __FILE__ . " on line " . __LINE__);
+        }
+
+        if ($data['depth'] == 1) {
+            $data['area'] = 1;
+        }
+
+        return $data;
+    }
+
+    /**
+     * return the topic_id of the parent element, false if there is none (ie the
+     * passed topic_id is already the upper-most node in the tree)
+     *
+     * @param string $topic_id the topic_id for which the parent shall be found
+     *
+     * @return string the topic_id of the parent element or false
+     */
+    public static function getParentTopicId($topic_id)
+    {
+        $path = ForumEntry::getPathToPosting($topic_id);
+        array_pop($path);
+        $data = array_pop($path);
+
+        return $data['id'] ?: false;
+    }
+
+
+    /**
+     * get the topic_ids of all childs of the passed topic including itself
+     *
+     * @param string $topic_id the topic_id to find the childs for
+     * @return array a list if topic_ids
+     */
+    public static function getChildTopicIds($topic_id)
+    {
+        $constraints = ForumEntry::getConstraints($topic_id);
+
+        $stmt = DBManager::get()->prepare("SELECT topic_id
+            FROM forum_entries WHERE lft >= ? AND rgt <= ?
+                AND seminar_id = ?");
+        $stmt->execute([$constraints['lft'], $constraints['rgt'], $constraints['seminar_id']]);
+
+        return $stmt->fetchAll(PDO::FETCH_COLUMN);
+    }
+
+    /* * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+     * D   A   T   A   -   R   E   T   R   I   E   V   A   L *
+     * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+     /**
+      * get the page the passed posting is on
+      *
+      * @param  string  $topic_id
+      * @return  int
+      */
+    public static function getPostingPage($topic_id, $constraint = null)
+    {
+        if (!$constraint) {
+            $constraint = ForumEntry::getConstraints($topic_id);
+        }
+
+        // this calculation only works for postings
+        if ($constraint['depth'] <= 2) return ForumHelpers::getPage();
+
+        if ($parent_id = ForumEntry::getParentTopicId($topic_id)) {
+            $parent_constraint = ForumEntry::getConstraints($parent_id);
+
+            return ceil((($constraint['lft'] - $parent_constraint['lft'] + 3) / 2) / ForumEntry::POSTINGS_PER_PAGE);
+        }
+
+        return 0;
+    }
+
+    /**
+     * return the id for the oldest unread child-posting for the passed topic.
+     *
+     * @param string $parent_id
+     * @return string  id of oldest unread posting
+     */
+    public static function getLastUnread($parent_id)
+    {
+        $constraint = ForumEntry::getConstraints($parent_id);
+
+        // take users visitdate into account
+        $visitdate = ForumVisit::getLastVisit($constraint['seminar_id']);
+
+        // get the first unread entry
+        $stmt = DBManager::get()->prepare("SELECT * FROM forum_entries
+            WHERE lft > ? AND rgt < ? AND seminar_id = ?
+                AND mkdate >= ?
+            ORDER BY mkdate ASC LIMIT 1");
+        $stmt->execute([$constraint['lft'], $constraint['rgt'], $constraint['seminar_id'], $visitdate]);
+        $last_unread = $stmt->fetch(PDO::FETCH_ASSOC);
+
+        return $last_unread ? $last_unread['topic_id'] : null;
+    }
+
+    /**
+     * retrieve the the latest posting under $parent_id
+     * or false if the postings itself is the latest
+     *
+     * @param string $parent_id the node to lookup the childs in
+     * @return mixed the data for the latest postings or false
+     */
+    public static function getLatestPosting($parent_id)
+    {
+        $constraint = ForumEntry::getConstraints($parent_id);
+
+        // get last entry
+        $stmt = DBManager::get()->prepare("SELECT * FROM forum_entries
+            WHERE lft > ? AND rgt < ? AND seminar_id = ?
+            ORDER BY mkdate DESC LIMIT 1");
+        $stmt->execute([$constraint['lft'], $constraint['rgt'], $constraint['seminar_id']]);
+
+        if (!$data = $stmt->fetch(PDO::FETCH_ASSOC)) {
+            return false;
+        }
+
+        return $data;
+    }
+
+    /**
+     * returns a hashmap with arrays containing id and name with the entries
+     * which lead to the passed topic
+     *
+     * @param string $topic_id the topic to get the path for
+     *
+     * @return array
+     */
+    public static function getPathToPosting($topic_id)
+    {
+        $data = ForumEntry::getConstraints($topic_id);
+        $ret = [];
+
+        $stmt = DBManager::get()->prepare("SELECT * FROM forum_entries
+            WHERE lft <= ? AND rgt >= ? AND seminar_id = ? ORDER BY lft ASC");
+        $stmt->execute([$data['lft'], $data['rgt'], $data['seminar_id']]);
+
+        while ($data = $stmt->fetch(PDO::FETCH_ASSOC)) {
+            $ret[$data['topic_id']] = $data;
+            $ret[$data['topic_id']]['id'] = $data['topic_id'];
+        }
+
+        // set the name of the first entry to the name of the category the entry is in
+        if (sizeof($ret) > 1) {
+            reset($ret);
+            $tmp = array_slice($ret, 1, 1);
+            $area = array_pop($tmp);
+            $top  = current($ret);
+            $ret[$top['id']]['name'] = ForumCat::getCategoryNameForArea($area['id']) ?: _('Allgemein');
+        }
+
+        return $ret;
+    }
+
+    /**
+     * returns a hashmap where key is topic_id and value a posting-title from the
+     * entries which lead to the passed topic.
+     *
+     * WARNING: This function ommits postings with an empty title. For a full
+     * list please use ForumEntry::getPathToPosting()!
+     *
+     * @param string $topic_id the topic to get the path for
+     *
+     * @return array
+     */
+    public static function getFlatPathToPosting($topic_id)
+    {
+        // use only the part of the path until the thread, no posting title
+        $postings = array_slice(self::getPathToPosting($topic_id), 0, 3);
+
+        // var_dump($postings);
+
+        foreach ($postings as $post) {
+            if ($post['name']) {
+                $ret[$post['id']] = $post['name'];
+            }
+        }
+
+        return $ret;
+    }
+
+    /**
+     * fill the passed postings with additional data
+     *
+     * @param  array $postings
+     * @return array
+     */
+    public static function parseEntries($postings)
+    {
+        $posting_list = [];
+
+        // retrieve the postings
+        foreach ($postings as $data) {
+            // we throw away all formatting stuff, tags, etc, leaving the important bit of information
+            $desc_short = ForumEntry::br2space(ForumEntry::killFormat(strip_tags($data['content'])));
+            if (mb_strlen($desc_short) > (ForumEntry::THREAD_PREVIEW_LENGTH + 2)) {
+                $desc_short = mb_substr($desc_short, 0, ForumEntry::THREAD_PREVIEW_LENGTH) . '...';
+            } else {
+                $desc_short = $desc_short;
+            }
+
+            $posting_list[$data['topic_id']] = [
+                'author'          => $data['author'],
+                'topic_id'        => $data['topic_id'],
+                'name'            => formatReady($data['name']),
+                'name_raw'        => $data['name'],
+                'content'         => ForumEntry::getContentAsHtml($data['content'], $data['anonymous']),
+                'content_raw'     => ForumEntry::killEdit($data['content']),
+                'content_short'   => $desc_short,
+                'chdate'          => $data['chdate'],
+                'mkdate'          => $data['mkdate'],
+                'user_id'        => $data['user_id'],
+                'raw_title'       => $data['name'],
+                'raw_description' => ForumEntry::killEdit($data['content']),
+                'fav'             => ($data['fav'] == 'fav'),
+                'depth'           => $data['depth'],
+                'anonymous'       => $data['anonymous'],
+                'closed'          => $data['closed'],
+                'sticky'          => $data['sticky'],
+                'seminar_id'      => $data['seminar_id']
+            ];
+        } // retrieve the postings
+
+        return $posting_list;
+    }
+
+    /**
+     * Get all entries for the passed parent_id.
+     * Returns an array of the following structure:
+     * Array (
+     *     'list'  => Array (
+     *         'author'          =>
+     *         'topic_id'        =>
+     *         'name'            => formatReady()
+     *         'name_raw'        =>
+     *         'content'         => formatReady()
+     *         'content_raw'     =>
+     *         'content_short'   =>
+     *         'chdate'          =>
+     *         'mkdate'          =>
+     *         'user_id'        =>
+     *         'raw_title'       =>
+     *         'raw_description' =>
+     *         'fav'             =>
+     *         'depth'           =>
+     *         'sticky'          =>
+     *         'closed'          =>
+     *         'seminar_id'      =>
+     *     )
+     *     'count' =>
+     * )
+     *
+     * @param string $parent_id    id of parent-element to get entries for.
+     * @param boolean $with_childs  if true, the whole subtree is fetched
+     * @param string $add          for additional constraints in the WHERE-part of the query
+     * @param string $sort_order   can be ASC or DESC
+     * @param int $start        can be used for pagination, is used for the LIMIT-part of the query
+     * @param int $limit        number of entries to fetch, defaults to ForumEntry::POSTINGS_PER_PAGE
+     *
+     * @return array
+     *
+     * @throws Exception  if the retrieval failed, an Exception is thrown
+     */
+    public static function getEntries($parent_id, $with_childs = false, $add = '',
+        $sort_order = 'DESC', $start = 0, $limit = ForumEntry::POSTINGS_PER_PAGE)
+    {
+        $constraint = ForumEntry::getConstraints($parent_id);
+        $seminar_id = $constraint['seminar_id'];
+        $depth      = $constraint['depth'] + 1;
+
+        // count the entries and set correct page if necessary
+        if ($with_childs) {
+            $count_stmt = DBManager::get()->prepare("SELECT COUNT(*) FROM forum_entries
+                LEFT JOIN forum_favorites as ou ON (ou.topic_id = forum_entries.topic_id AND ou.user_id = ?)
+                WHERE (forum_entries.seminar_id = ?
+                    AND forum_entries.seminar_id != forum_entries.topic_id
+                    AND lft > ? AND rgt < ?) "
+                . ($depth > 2 ? " OR forum_entries.topic_id = ". DBManager::get()->quote($parent_id) : '')
+                . $add
+                . " ORDER BY forum_entries.mkdate $sort_order");
+            $count_stmt->execute([$GLOBALS['user']->id, $seminar_id, $constraint['lft'], $constraint['rgt']]);
+            $count = $count_stmt->fetchColumn();
+        } else {
+            $count_stmt = DBManager::get()->prepare("SELECT COUNT(*) FROM forum_entries
+                LEFT JOIN forum_favorites as ou ON (ou.topic_id = forum_entries.topic_id AND ou.user_id = ?)
+                WHERE ((depth = ? AND forum_entries.seminar_id = ?
+                    AND forum_entries.seminar_id != forum_entries.topic_id
+                    AND lft > ? AND rgt < ?) "
+                . ($depth > 2 ? " OR forum_entries.topic_id = ". DBManager::get()->quote($parent_id) : '')
+                . ') '. $add
+                . " ORDER BY forum_entries.mkdate $sort_order");
+            $count_stmt->execute([$GLOBALS['user']->id, $depth, $seminar_id, $constraint['lft'], $constraint['rgt']]);
+            $count = $count_stmt->fetchColumn();
+        }
+
+        // use the last page if the requested page does not exist
+        if ($start > $count) {
+            $page = ceil($count / ForumEntry::POSTINGS_PER_PAGE);
+            ForumHelpers::setPage($page);
+            $start = max(1, $page - 1) * ForumEntry::POSTINGS_PER_PAGE;
+        }
+
+        if ($with_childs) {
+            $stmt = DBManager::get()->prepare("SELECT forum_entries.*, IF(ou.topic_id IS NOT NULL, 'fav', NULL) as fav
+                    FROM forum_entries
+                LEFT JOIN forum_favorites as ou ON (ou.topic_id = forum_entries.topic_id AND ou.user_id = ?)
+                WHERE (forum_entries.seminar_id = ?
+                    AND forum_entries.seminar_id != forum_entries.topic_id
+                    AND lft > ? AND rgt < ?) "
+                . ($depth > 2 ? " OR forum_entries.topic_id = ". DBManager::get()->quote($parent_id) : '')
+                . $add
+                . " ORDER BY forum_entries.mkdate $sort_order"
+                . ($limit ? " LIMIT $start, $limit" : ''));
+            $stmt->execute([$GLOBALS['user']->id, $seminar_id, $constraint['lft'], $constraint['rgt']]);
+        } else {
+            $stmt = DBManager::get()->prepare("SELECT forum_entries.*, IF(ou.topic_id IS NOT NULL, 'fav', NULL) as fav
+                    FROM forum_entries
+                LEFT JOIN forum_favorites as ou ON (ou.topic_id = forum_entries.topic_id AND ou.user_id = ?)
+                WHERE ((depth = ? AND forum_entries.seminar_id = ?
+                    AND lft > ? AND rgt < ?) "
+                . ($depth > 2 ? " OR forum_entries.topic_id = ". DBManager::get()->quote($parent_id) : '')
+                . ') '. $add
+                . " ORDER BY forum_entries.mkdate $sort_order"
+                . ($limit ? " LIMIT $start, $limit" : ''));
+            $stmt->execute([$GLOBALS['user']->id, $depth, $seminar_id, $constraint['lft'], $constraint['rgt']]);
+        }
+
+        if (!$stmt) {
+            throw new Exception("Error while retrieving postings in " . __FILE__ . " on line " . __LINE__);
+        }
+
+        return ['list' => ForumEntry::parseEntries($stmt->fetchAll(PDO::FETCH_ASSOC)), 'count' => $count];
+    }
+
+
+    /**
+     * Takes a posting-array like the one generated by ForumEntry::getList()
+     * and adds the child-posting with the freshest creation-date to it.
+     *
+     * @param array $postings
+     * @return array
+     */
+    public static function getLastPostings($postings)
+    {
+        foreach ($postings as $key => $posting) {
+
+            if ($data = ForumEntry::getLatestPosting($posting['topic_id'])) {
+                $last_posting['topic_id']      = $data['topic_id'];
+                $last_posting['date']          = $data['mkdate'];
+                $last_posting['user_id']       = $data['user_id'];
+                $last_posting['user_fullname'] = $data['author'];
+                $last_posting['username']      = get_username($data['user_id']);
+                $last_posting['anonymous']     = $data['anonymous'];
+
+                // we throw away all formatting stuff, tags, etc, so we have just the important bit of information
+                $text = strip_tags($data['name']);
+                $text = ForumEntry::br2space($text);
+                $text = ForumEntry::killFormat(ForumEntry::removeQuotes($text));
+
+                if (mb_strlen($text) > 42) {
+                    $text = mb_substr($text, 0, 40) . '...';
+                }
+
+                $last_posting['text'] = $text;
+            }
+
+            $postings[$key]['last_posting'] = $last_posting;
+            if (!$postings[$key]['last_unread']  = ForumEntry::getLastUnread($posting['topic_id'])) {
+                $postings[$key]['last_unread'] = $last_posting['topic_id'];
+            }
+            $postings[$key]['num_postings'] = ForumEntry::countEntries($posting['topic_id']);
+
+            unset($last_posting);
+        }
+
+        return $postings;
+    }
+
+    /**
+     * get a list of postings of a special type
+     *
+     * @param string $type one of 'area', 'list', 'postings', 'latest', 'favorites', 'dump', 'flat'
+     * @param string $parent_id the are to fetch from
+     * @return array array('list' => ..., 'count' => ...);
+     */
+    public static function getList($type, $parent_id)
+    {
+        $start = (ForumHelpers::getPage() - 1) * ForumEntry::POSTINGS_PER_PAGE;
+
+        switch ($type) {
+            case 'area':
+                $list = ForumEntry::getEntries($parent_id, ForumEntry::WITHOUT_CHILDS, '', 'DESC', 0, 1000);
+                $postings = $list['list'];
+
+                $postings = ForumEntry::getLastPostings($postings);
+                return ['list' => $postings, 'count' => $list['count']];
+
+                break;
+
+            case 'list':
+                $constraint = ForumEntry::getConstraints($parent_id);
+
+                // purpose of the following query is to retrieve the threads
+                // for an area ordered by the mkdate of their latest posting
+                $stmt = DBManager::get()->prepare("SELECT SQL_CALC_FOUND_ROWS
+                        fe.*, IF(ou.topic_id IS NOT NULL, 'fav', NULL) as fav
+                    FROM forum_entries AS fe
+                    LEFT JOIN forum_favorites as ou ON (ou.topic_id = fe.topic_id AND ou.user_id = :user_id)
+                    WHERE fe.seminar_id = :seminar_id AND fe.lft > :left
+                        AND fe.rgt < :right AND fe.depth = 2
+                    ORDER BY sticky DESC, latest_chdate DESC
+                    LIMIT $start, ". ForumEntry::POSTINGS_PER_PAGE);
+                $stmt->bindParam(':seminar_id', $constraint['seminar_id']);
+                $stmt->bindParam(':left', $constraint['lft'], PDO::PARAM_INT);
+                $stmt->bindParam(':right', $constraint['rgt'], PDO::PARAM_INT);
+                $stmt->bindParam(':user_id', $GLOBALS['user']->id);
+                $stmt->execute();
+
+                $postings = $stmt->fetchAll(PDO::FETCH_ASSOC);
+                $count = DBManager::get()->query("SELECT FOUND_ROWS()")->fetchColumn();
+                $postings = ForumEntry::parseEntries($postings);
+                $postings = ForumEntry::getLastPostings($postings);
+
+                return ['list' => $postings, 'count' => $count];
+                break;
+
+            case 'postings':
+                return ForumEntry::getEntries($parent_id, ForumEntry::WITH_CHILDS, '', 'ASC', $start);
+                break;
+
+            case 'newest':
+                $constraint = ForumEntry::getConstraints($parent_id);
+
+                // get postings
+                $stmt = DBManager::get()->prepare("SELECT forum_entries.*, IF(ou.topic_id IS NOT NULL, 'fav', NULL) as fav
+                    FROM forum_entries
+                    LEFT JOIN forum_favorites as ou ON (ou.topic_id = forum_entries.topic_id AND ou.user_id = :user_id)
+                    WHERE seminar_id = :seminar_id AND lft > :left
+                        AND rgt < :right AND (mkdate >= :mkdate OR chdate >= :mkdate)
+                    ORDER BY mkdate ASC
+                    LIMIT $start, ". ForumEntry::POSTINGS_PER_PAGE);
+
+                $stmt->bindParam(':seminar_id', $constraint['seminar_id']);
+                $stmt->bindParam(':left', $constraint['lft']);
+                $stmt->bindParam(':right', $constraint['rgt']);
+                $stmt->bindParam(':mkdate', ForumVisit::getLastVisit($constraint['seminar_id']));
+                $stmt->bindParam(':user_id', $GLOBALS['user']->id);
+                $stmt->execute();
+
+                $postings = $stmt->fetchAll(PDO::FETCH_ASSOC);
+
+                $postings = ForumEntry::parseEntries($postings);
+                // var_dump($postings);
+
+                // count found postings
+                $stmt_count = DBManager::get()->prepare("SELECT COUNT(*)
+                    FROM forum_entries
+                    WHERE seminar_id = :seminar_id AND lft > :left
+                        AND rgt < :right AND mkdate >= :mkdate
+                    ORDER BY mkdate ASC");
+
+                $stmt_count->bindParam(':seminar_id', $constraint['seminar_id']);
+                $stmt_count->bindParam(':left', $constraint['lft']);
+                $stmt_count->bindParam(':right', $constraint['rgt']);
+                $stmt_count->bindParam(':mkdate', ForumVisit::getLastVisit($constraint['seminar_id']));
+                $stmt_count->execute();
+
+
+                // return results
+                return ['list' => $postings, 'count' => $stmt_count->fetchColumn()];
+                break;
+
+            case 'latest':
+                return ForumEntry::getEntries($parent_id, ForumEntry::WITH_CHILDS, '', 'DESC', $start);
+                break;
+
+            case 'favorites':
+                $add = "AND ou.topic_id IS NOT NULL";
+                return ForumEntry::getEntries($parent_id, ForumEntry::WITH_CHILDS, $add, 'DESC', $start);
+                break;
+
+            case 'dump':
+                $constraint = ForumEntry::getConstraints($parent_id);
+                $seminar_id = $constraint['seminar_id'];
+                $depth      = $constraint['depth'] + 1;
+
+                $stmt = DBManager::get()->prepare("SELECT * FROM forum_entries
+                    WHERE (forum_entries.seminar_id = ?
+                        AND forum_entries.seminar_id != forum_entries.topic_id
+                        AND lft > ? AND rgt < ?) "
+                    . ($depth > 2 ? " OR forum_entries.topic_id = ". DBManager::get()->quote($parent_id) : '')
+                    . " ORDER BY forum_entries.lft ASC");
+                $stmt->execute([$seminar_id, $constraint['lft'], $constraint['rgt']]);
+
+                return ForumEntry::parseEntries($stmt->fetchAll(PDO::FETCH_ASSOC));
+                break;
+
+            case 'flat':
+                $constraint = ForumEntry::getConstraints($parent_id);
+
+                $stmt = DBManager::get()->prepare("SELECT SQL_CALC_FOUND_ROWS * FROM forum_entries
+                    WHERE lft > ? AND rgt < ? AND seminar_id = ? AND depth = ?
+                    ORDER BY name ASC");
+                $stmt->execute([$constraint['lft'], $constraint['rgt'], $constraint['seminar_id'], $constraint['depth'] + 1]);
+
+                $count = DBManager::get()->query("SELECT FOUND_ROWS()")->fetchColumn();
+
+                $posting_list = [];
+
+                // speed up things a bit by leaving out the formatReady fields
+                foreach ($stmt->fetchAll(PDO::FETCH_ASSOC) as $data) {
+                    // we throw away all formatting stuff, tags, etc, leaving the important bit of information
+                    $desc_short = ForumEntry::br2space(ForumEntry::killFormat(strip_tags($data['content'])));
+                    if (mb_strlen($desc_short) > (ForumEntry::THREAD_PREVIEW_LENGTH + 2)) {
+                        $desc_short = mb_substr($desc_short, 0, ForumEntry::THREAD_PREVIEW_LENGTH) . '...';
+                    } else {
+                        $desc_short = $desc_short;
+                    }
+                    $posting_list[$data['topic_id']] = [
+                        'author'          => $data['author'],
+                        'topic_id'        => $data['topic_id'],
+                        'name_raw'        => $data['name'],
+                        'content_raw'     => ForumEntry::killEdit($data['content']),
+                        'content_short'   => $desc_short,
+                        'chdate'          => $data['chdate'],
+                        'mkdate'          => $data['mkdate'],
+                        'user_id'         => $data['user_id'],
+                        'raw_title'       => $data['name'],
+                        'raw_description' => ForumEntry::killEdit($data['content']),
+                        'fav'             => ($data['fav'] == 'fav'),
+                        'depth'           => $data['depth'],
+                        'seminar_id'      => $data['seminar_id']
+                    ];
+                }
+
+                return ['list' => $posting_list, 'count' => $count];
+                break;
+
+            case 'depth_to_large':
+                $constraint = ForumEntry::getConstraints($parent_id);
+
+                $stmt = DBManager::get()->prepare("SELECT SQL_CALC_FOUND_ROWS * FROM forum_entries
+                    WHERE lft > ? AND rgt < ? AND seminar_id = ? AND depth > 3
+                    ORDER BY name ASC");
+                $stmt->execute([$constraint['lft'], $constraint['rgt'], $constraint['seminar_id']]);
+
+                $count = DBManager::get()->query("SELECT FOUND_ROWS()")->fetchColumn();
+
+                return ['list' => $stmt->fetchAll(PDO::FETCH_ASSOC), 'count' => $count];
+                break;
+        }
+    }
+
+    /**
+     * Get the latest forum entries for the passed entries childs
+     *
+     * @param string $parent_id
+     * @param int $start_date  timestamp
+     * @param int $end_date    timestamp
+     *
+     * @return array list of postings
+     */
+    public static function getLatestSince($parent_id, $start_date, $end_date)
+    {
+        $constraint = ForumEntry::getConstraints($parent_id);
+
+        $stmt = DBManager::get()->prepare("SELECT SQL_CALC_FOUND_ROWS * FROM forum_entries
+            WHERE lft > ? AND rgt < ? AND seminar_id = ?
+                AND mkdate BETWEEN ? AND ?
+            ORDER BY name ASC");
+        $stmt->execute([$constraint['lft'], $constraint['rgt'], $constraint['seminar_id'], $start_date, $end_date]);
+
+        return $stmt->fetchAll(PDO::FETCH_ASSOC);
+    }
+
+    /**
+     ** returns a list of postings for the passed search-term
+     *
+     * @param string $parent_id the area to search in (can be a whole seminar)
+     * @param string $_searchfor the term to search for
+     * @param array $options filter-options: search_title, search_content, search_author
+     * @return array array('list' => ..., 'count' => ...);
+     */
+    public static function getSearchResults($parent_id, $_searchfor, $options)
+    {
+        $start = (ForumHelpers::getPage() - 1) * ForumEntry::POSTINGS_PER_PAGE;
+
+        // if there are quoted parts, they should not be separated
+        $suchmuster = '/".*"/U';
+        preg_match_all($suchmuster, $_searchfor, $treffer);
+        array_walk($treffer[0], function(&$value) { $value = trim($value, '"'); });
+
+        // remove the quoted parts from $_searchfor
+        $_searchfor = trim(preg_replace($suchmuster, '', $_searchfor));
+
+        // split the searchstring $_searchfor at every space
+        $parts = explode(' ', $_searchfor);
+
+        foreach ($parts as $key => $val) {
+            if ($val == '') {
+                unset($parts[$key]);
+            }
+        }
+
+        if (!empty($parts)) {
+            $_searchfor = array_merge($parts, $treffer[0]);
+        } else  {
+            $_searchfor = $treffer[0];
+        }
+
+        // make an SQL-statement out of the searchstring
+        $search_string = [];
+        foreach ($_searchfor as $key => $val) {
+            if (!$val) {
+                unset($_searchfor[$key]);
+            } else {
+                $search_word = '%'. $val .'%';
+                $zw_search_string = [];
+                if ($options['search_title']) {
+                    $zw_search_string[] .= "name LIKE " . DBManager::get()->quote($search_word);
+                }
+
+                if ($options['search_content']) {
+                    $zw_search_string[] .= "content LIKE " . DBManager::get()->quote($search_word);
+                }
+
+                if ($options['search_author']) {
+                    $zw_search_string[] .= "author LIKE " . DBManager::get()->quote($search_word);
+                }
+
+                if (!empty($zw_search_string)) {
+                    $search_string[] = '(' . implode(' OR ', $zw_search_string) . ')';
+                }
+            }
+        }
+
+        if (!empty($search_string)) {
+            $add = "AND (" . implode(' AND ', $search_string) . ")";
+            return array_merge(
+                ['highlight' => $_searchfor],
+                ForumEntry::getEntries($parent_id, ForumEntry::WITH_CHILDS, $add, 'DESC', $start)
+            );
+        }
+
+        return ['num_postings' => 0, 'list' => []];
+    }
+
+    /**
+     * returns the entry for the passed topic_id
+     *
+     * @param string $topic_id
+     * @return array hash-array with the entries fields
+     */
+    public static function getEntry($topic_id)
+    {
+        return ForumEntry::getConstraints($topic_id);
+    }
+
+    /**
+     * Count the number of child-elements that the passed entry has and return it.
+     *
+     * @param string $parent_id
+     *
+     * @return int  the number of child entries for the passed entry
+     */
+    public static function countEntries($parent_id)
+    {
+        $data = ForumEntry::getConstraints($parent_id);
+        return max((($data['rgt'] - $data['lft'] - 1) / 2) + 1, 0);
+    }
+
+    /**
+    * Count the number of postings in a given course and return it.
+    *
+    * @param string $course_id the id of the given course
+    *
+    * @return int the number of postings in the course
+    */
+    public static function countPostings($course_id)
+    {
+        $stmt = DBManager::get()->prepare("SELECT COUNT(*) FROM forum_entries
+            WHERE seminar_id = ? AND depth >= 2");
+        $stmt->execute([$course_id]);
+
+        return $stmt->fetchColumn(0);
+    }
+
+    /**
+     * Count all entries the passed user has ever written and return the result
+     *
+     * @staticvar type $entries
+     *
+     * @param string $user_id
+     *
+     * @return int  number of entries user has ever written
+     */
+    public static function countUserEntries($user_id, $seminar_id = null)
+    {
+        static $entries;
+
+        if (!$entries[$user_id]) {
+            $stmt = DBManager::get()->prepare("SELECT COUNT(*)
+                FROM forum_entries
+                WHERE user_id = ? AND seminar_id = IFNULL(?, seminar_id)");
+            $stmt->execute([$user_id, $seminar_id]);
+
+            $entries[$user_id] = $stmt->fetchColumn();
+        }
+
+        return $entries[$user_id];
+    }
+
+    /* * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+     *   D   A   T   A   -   C   R   E   A   T   I   O   N   *
+     * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+    /**
+     * insert a node into the table
+     *
+     * @param array $data an array containing the following fields:
+     *     topic_id     the id of the new topic
+     *     seminar_id   the id of the seminar to add the topic to
+     *     user_id      the id of the user who created the topic
+     *     name         the title of the entry
+     *     content      the content of the entry
+     *     author       the author's name as a plaintext string
+     *     author_host  ip-address of creator
+     * @param string $parent_id the node to add the topic to
+     *
+     * @return void
+     */
+    public static function insert($data, $parent_id)
+    {
+        $constraint = ForumEntry::getConstraints($parent_id);
+
+        // #TODO: Zusammenfassen in eine Transaktion!!!
+        DBManager::get()->exec('UPDATE forum_entries SET lft = lft + 2
+            WHERE lft > '. $constraint['rgt'] ." AND seminar_id = '". $constraint['seminar_id'] ."'");
+        DBManager::get()->exec('UPDATE forum_entries SET rgt = rgt + 2
+            WHERE rgt >= '. $constraint['rgt'] ." AND seminar_id = '". $constraint['seminar_id'] ."'");
+
+        $stmt = DBManager::get()->prepare("INSERT INTO forum_entries
+            (topic_id, seminar_id, user_id, name, content, mkdate, latest_chdate,
+                chdate, author, author_host, lft, rgt, depth, anonymous)
+            VALUES (? ,?, ?, ?, ?, UNIX_TIMESTAMP(), UNIX_TIMESTAMP(), UNIX_TIMESTAMP(), ?, ?, ?, ?, ?, ?)");
+        $stmt->execute([$data['topic_id'], $data['seminar_id'], $data['user_id'],
+            $data['name'], transformBeforeSave($data['content']), $data['author'], $data['author_host'],
+            $constraint['rgt'], $constraint['rgt'] + 1, $constraint['depth'] + 1, $data['anonymous'] ? : 0]);
+
+        // update "latest_chdate" for easier sorting of actual threads
+        DBManager::get()->exec("UPDATE forum_entries SET latest_chdate = UNIX_TIMESTAMP()
+            WHERE topic_id = '" . $constraint['topic_id'] . "'");
+
+        NotificationCenter::postNotification('ForumAfterInsert', $data['topic_id'], $data);
+    }
+
+
+    /**
+     * update the passed topic
+     *
+     * @param string $topic_id the id of the topic to update
+     * @param string $name the new name
+     * @param string $content the new content
+     *
+     * @return void
+     */
+    public static function update($topic_id, $name, $content)
+    {
+        $post = ForumEntry::getConstraints($topic_id);
+
+        if (time() - $post['mkdate'] > 5 * 60) {
+            $content = ForumEntry::appendEdit($content);
+        }
+
+        $stmt = DBManager::get()->prepare("UPDATE forum_entries
+            SET name = ?, content = ?, chdate = UNIX_TIMESTAMP(), latest_chdate = UNIX_TIMESTAMP()
+            WHERE topic_id = ?");
+        $stmt->execute([$name, transformBeforeSave($content), $topic_id]);
+
+        // update "latest_chdate" for easier sorting of actual threads
+        $parent_id = ForumEntry::getParentTopicId($topic_id);
+        DBManager::get()->exec("UPDATE forum_entries SET latest_chdate = UNIX_TIMESTAMP()
+            WHERE topic_id = '" . $parent_id . "'");
+
+        $post['name']    = $name;
+        $post['content'] = $content;
+
+        NotificationCenter::postNotification('ForumAfterUpdate', $topic_id, $post);
+    }
+
+    /**
+     * delete an entry and all his descendants from the mptt-table
+     *
+     * @param string $topic_id the id of the entry to delete
+     *
+     * @return void
+     */
+    public static function delete($topic_id)
+    {
+        $post   = ForumEntry::getConstraints($topic_id);
+        $parent = ForumEntry::getConstraints(ForumEntry::getParentTopicId($topic_id));
+
+        NotificationCenter::postNotification('ForumBeforeDelete', $topic_id, $post);
+
+        // #TODO: Zusammenfassen in eine Transaktion!!!
+        // get all entry-ids to delete them from the category-reference-table
+        $stmt = DBManager::get()->prepare("SELECT topic_id FROM forum_entries
+            WHERE seminar_id = ? AND lft >= ? AND rgt <= ? AND depth = 1");
+        $stmt->execute([$post['seminar_id'], $post['lft'], $post['rgt']]);
+        $ids = $stmt->fetchAll(PDO::FETCH_COLUMN);
+
+        if ($ids != false && !is_array($ids)) $ids = [$ids];
+
+        if (!empty($ids)) {
+            $stmt = DBManager::get()->prepare("DELETE FROM forum_categories_entries
+                WHERE topic_id IN (:ids)");
+            $stmt->bindParam(':ids', $ids, StudipPDO::PARAM_ARRAY);
+            $stmt->execute();
+        }
+
+        // delete all entries
+        $stmt = DBManager::get()->prepare("DELETE FROM forum_entries
+            WHERE seminar_id = ? AND lft >= ? AND rgt <= ?");
+
+        $stmt->execute([$post['seminar_id'], $post['lft'], $post['rgt']]);
+
+        // update lft and rgt
+        $diff = $post['rgt'] - $post['lft'] + 1;
+        $stmt = DBManager::get()->prepare("UPDATE forum_entries SET lft = lft - $diff
+            WHERE lft > ? AND seminar_id = ?");
+        $stmt->execute([$post['rgt'], $post['seminar_id']]);
+
+        $stmt = DBManager::get()->prepare("UPDATE forum_entries SET rgt = rgt - $diff
+            WHERE rgt > ? AND seminar_id = ?");
+        $stmt->execute([$post['rgt'], $post['seminar_id']]);
+
+
+        // set the latest_chdate to the latest child's chdate
+        $stmt = DBManager::get()->prepare("SELECT chdate FROM forum_entries
+            WHERE lft > ? AND rgt < ? AND seminar_id = ?
+            ORDER BY chdate DESC LIMIT 1");
+        $stmt->execute([$parent['lft'], $parent['rgt'], $parent['seminar_id']]);
+        $chdate = $stmt->fetchColumn();
+
+        $stmt_insert = DBManager::get()->prepare("UPDATE forum_entries
+            SET chdate = ? WHERE topic_id = ?");
+        if ($chdate) {
+            $stmt_insert->execute([$chdate, $parent['topic_id']]);
+        } else {
+            $stmt_insert->execute([$parent['chdate'], $parent['topic_id']]);
+        }
+    }
+
+    /**
+     * move the passed topic to the passed area
+     *
+     * @param string $topic_id the topic to move
+     * @param string $destination the area_id where the topic is moved to
+     *
+     * @return void
+     */
+    public static function move($topic_id, $destination)
+    {
+        // #TODO: Zusammenfassen in eine Transaktion!!!
+        $constraints = ForumEntry::getConstraints($topic_id);
+
+        // move the affected entries "outside" the tree
+        $stmt = DBManager::get()->prepare("UPDATE forum_entries
+            SET lft = lft * -1, rgt = rgt * -1
+            WHERE seminar_id = ? AND lft >= ? AND rgt <= ?");
+        $stmt->execute([$constraints['seminar_id'], $constraints['lft'], $constraints['rgt']]);
+
+        // update the lft and rgt values of the parent to reflect the "deletion"
+        $diff = $constraints['rgt'] - $constraints['lft'] + 1;
+        $stmt = DBManager::get()->prepare("UPDATE forum_entries SET lft = lft - ?
+            WHERE lft > ? AND seminar_id = ?");
+        $stmt->execute([$diff, $constraints['rgt'], $constraints['seminar_id']]);
+
+        $stmt = DBManager::get()->prepare("UPDATE forum_entries SET rgt = rgt - ?
+            WHERE rgt > ? AND seminar_id = ?");
+        $stmt->execute([$diff, $constraints['rgt'], $constraints['seminar_id']]);
+
+        // make some space by updating the lft and rgt values of the target node
+        $constraints_destination = ForumEntry::getConstraints($destination);
+        $size = $constraints['rgt'] - $constraints['lft'] + 1;
+
+        $stmt = DBManager::get()->prepare("UPDATE forum_entries SET lft = lft + ?
+            WHERE lft > ? AND seminar_id = ?");
+        $stmt->execute([$size, $constraints_destination['rgt'], $constraints_destination['seminar_id']]);
+
+        $stmt = DBManager::get()->prepare("UPDATE forum_entries SET rgt = rgt + ?
+            WHERE rgt >= ? AND seminar_id = ?");
+        $stmt->execute([$size, $constraints_destination['rgt'], $constraints_destination['seminar_id']]);
+
+        //move the entries from "outside" the tree to the target node
+        $constraints_destination = ForumEntry::getConstraints($destination);
+
+
+        // update the depth to reflect the new position in the tree
+        // determine if we need to add, subtract or even do nothing to/from the depth
+        $depth_mod = $constraints_destination['depth'] - $constraints['depth'] + 1;
+
+        $stmt = DBManager::get()->prepare("UPDATE forum_entries
+            SET depth = depth + ?
+            WHERE seminar_id = ? AND lft < 0");
+        $stmt->execute([$depth_mod, $constraints_destination['seminar_id']]);
+
+        // if the depth is larger than 3, fix it
+        $stmt = DBManager::get()->prepare("UPDATE forum_entries
+            SET depth = 3
+            WHERE seminar_id = ? AND depth > 3 AND lft < 0");
+        $stmt->execute([$constraints_destination['seminar_id']]);
+
+        // move the tree to its destination
+        $diff = ($constraints_destination['rgt'] - ($constraints['rgt'] - $constraints['lft'])) - 1 - $constraints['lft'];
+
+        $stmt = DBManager::get()->prepare("UPDATE forum_entries
+            SET lft = (lft * -1) + ?, rgt = (rgt * -1) + ?
+            WHERE seminar_id = ? AND lft < 0");
+        $stmt->execute([$diff, $diff, $constraints_destination['seminar_id']]);
+
+        if ($depth_mod != 0) {
+            self::fix_ordering($topic_id);
+        }
+    }
+
+    private static function fix_ordering($parent_id)
+    {
+        $db = DBManager::get();
+
+        $entry = ForumEntry::getConstraints($parent_id);
+
+        $stmt= $db->prepare('SELECT topic_id FROM forum_entries
+                               WHERE lft > ? AND rgt < ? AND depth = 3
+                                    AND seminar_id = ?
+                               ORDER BY mkdate');
+
+        $stmt->execute([$entry['lft'], $entry['rgt'], $entry['seminar_id']]);
+
+        $lft = $entry['lft'] + 1;
+        $rgt = $lft + 1;
+
+        $inner_stmt = $db->prepare("UPDATE forum_entries SET lft=?, rgt=?
+            WHERE topic_id = ?");
+        while ($topic_id = $stmt->fetchColumn()) {
+            $inner_stmt->execute([$lft, $rgt, $topic_id]);
+
+            $lft += 2;
+            $rgt += 2;
+        }
+    }
+
+    /**
+     * close the passed topic
+     *
+     * @param string $topic_id the topic to close
+     *
+     * @return void
+     */
+    public static function close($topic_id)
+    {
+        // close all entries belonging to the topic
+        $stmt = DBManager::get()->prepare("UPDATE forum_entries
+            SET closed = 1
+            WHERE topic_id = ?");
+        $stmt->execute([$topic_id]);
+    }
+
+    /**
+     * open the passed topic
+     *
+     * @param string $topic_id the topic to open
+     *
+     * @return void
+     */
+    public static function open($topic_id)
+    {
+        // open all entries belonging to the topic
+        $stmt = DBManager::get()->prepare("UPDATE forum_entries
+            SET closed = 0
+            WHERE topic_id = ?");
+        $stmt->execute([$topic_id]);
+    }
+
+    /**
+     * make the passed topic sticky
+     *
+     * @param string $topic_id the topic to make sticky
+     *
+     * @return void
+     */
+    public static function sticky($topic_id)
+    {
+        // open all entries belonging to the topic
+        $stmt = DBManager::get()->prepare("UPDATE forum_entries
+            SET sticky = 1
+            WHERE topic_id = ?");
+        $stmt->execute([$topic_id]);
+    }
+
+    /**
+     * make the passed topic unsticky
+     *
+     * @param string $topic_id the topic to make unsticky
+     *
+     * @return void
+     */
+    public static function unsticky($topic_id)
+    {
+        // open all entries belonging to the topic
+        $stmt = DBManager::get()->prepare("UPDATE forum_entries
+            SET sticky = 0
+            WHERE topic_id = ?");
+        $stmt->execute([$topic_id]);
+    }
+
+    /**
+     * check, if the default root-node for this seminar exists and make sure
+     * the default category exists as well
+     *
+     * @param string $seminar_id
+     *
+     * @return void
+     */
+    public static function checkRootEntry($seminar_id)
+    {
+        setTempLanguage();
+
+        // check, if the root entry in the topic tree exists
+        $stmt = DBManager::get()->prepare("SELECT COUNT(*) FROM forum_entries
+            WHERE topic_id = ? AND seminar_id = ?");
+        $stmt->execute([$seminar_id, $seminar_id]);
+        if ($stmt->fetchColumn() == 0) {
+            $stmt = DBManager::get()->prepare("INSERT INTO forum_entries
+                (topic_id, seminar_id, name, mkdate, chdate, lft, rgt, depth)
+                VALUES (?, ?, 'Übersicht', UNIX_TIMESTAMP(), UNIX_TIMESTAMP(), 0, 1, 0)");
+            $stmt->execute([$seminar_id, $seminar_id]);
+        }
+
+
+        // make sure, that the category "Allgemein" exists
+        $stmt = DBManager::get()->prepare("INSERT IGNORE INTO forum_categories
+            (category_id, seminar_id, entry_name) VALUES (?, ?, ?)");
+        $stmt->execute([$seminar_id, $seminar_id, _('Allgemein')]);
+
+        // make sure that the default area "Allgemeine Diskussionen" exists, if there is nothing else present
+        $stmt = DBManager::get()->prepare("SELECT COUNT(*) FROM forum_entries
+            WHERE seminar_id = ? AND depth = 1");
+        $stmt->execute([$seminar_id]);
+
+        // add default area
+        if ($stmt->fetchColumn() == 0) {
+            $data = [
+                'topic_id'    => md5(uniqid()),
+                'seminar_id'  => $seminar_id,
+                'user_id'     => '',
+                'name'        => _('Allgemeine Diskussion'),
+                'content'     => _('Hier ist Raum für allgemeine Diskussionen'),
+                'author'      => '',
+                'author_host' => ''
+            ];
+            ForumEntry::insert($data, $seminar_id);
+        }
+
+        restoreLanguage();
+    }
+
+    /**
+     * returns the ten most active seminars
+     *
+     * @return array
+     */
+    public static function getTopTenSeminars()
+    {
+        return DBManager::get()->query("SELECT a.seminar_id, b.name AS display,
+            count( a.seminar_id ) AS count FROM forum_entries a
+            INNER JOIN seminare b USING ( seminar_id )
+            WHERE b.visible = 1
+            AND a.mkdate > UNIX_TIMESTAMP( NOW( ) - INTERVAL 2 WEEK )
+            GROUP BY a.seminar_id
+            ORDER BY count DESC
+            LIMIT 10")->fetchAll(PDO::FETCH_ASSOC);
+    }
+
+    /**
+     * count all entries that exists in the whole installation and return it.
+     *
+     * @return int
+     */
+    public static function countAllEntries()
+    {
+        return count_table_rows('forum_entries');
+    }
+
+    /**
+     * updates the user-entries and replaces the old user-id by the new one
+     *
+     * @param string $user_from
+     * @param string $user_to
+     */
+    public static function migrateUser($user_from, $user_to)
+    {
+        $stmt = DBManager::get()->prepare("UPDATE forum_entries SET user_id = ? WHERE user_id = ?");
+        $stmt->execute([$user_to, $user_from]);
+
+        $stmt = DBManager::get()->prepare("UPDATE IGNORE forum_favorites SET user_id = ? WHERE user_id = ?");
+        $stmt->execute([$user_to, $user_from]);
+
+        $stmt = DBManager::get()->prepare("UPDATE IGNORE forum_visits SET user_id = ? WHERE user_id = ?");
+        $stmt->execute([$user_to, $user_from]);
+
+        $stmt = DBManager::get()->prepare("UPDATE IGNORE forum_likes SET user_id = ? WHERE user_id = ?");
+        $stmt->execute([$user_to, $user_from]);
+
+        $stmt = DBManager::get()->prepare("UPDATE IGNORE forum_abo_users SET user_id = ? WHERE user_id = ?");
+        $stmt->execute([$user_to, $user_from]);
+    }
+
+    /**
+     * returns the complete seminar or only the passed sub-tree as a html-string
+     *
+     * @param string $seminar_id
+     *
+     * @return string
+     */
+    public static function getDump($seminar_id, $parent_id = null)
+    {
+        $seminar_name = get_object_name($seminar_id, 'sem');
+        $content = '<h1>'. _('Forum') .': '  . $seminar_name['name'] .'</h1>';
+        $data = ForumEntry::getList('dump', $parent_id ?: $seminar_id);
+
+        foreach ($data as $entry) {
+            if ($entry['depth'] == 1) {
+                $content .= '<h2>'. _('Bereich') .': '. $entry['name'] .'</h2>';
+                $content .= $entry['content'] .'<br><br>';
+            } else if ($entry['depth'] == 2) {
+                $content .= '<h3 style="margin-bottom: 0px;">'. _('Thema') .': '. $entry['name'] .'</h3>';
+                $content .= '<i>' . sprintf(_('erstellt von %s am %s'), htmlReady($entry['author']),
+                    strftime('%A %d. %B %Y, %H:%M', (int)$entry['mkdate'])) . '</i><br>';
+                $content .= $entry['content'] .'<br><br>';
+            } else if ($entry['depth'] == 3) {
+                $content .= '<b>'.$entry['name'] .'</b><br>';
+                $content .= '<i>' . sprintf(_('erstellt von %s am %s'), htmlReady($entry['author']),
+                    strftime('%A %d. %B %Y, %H:%M', (int)$entry['mkdate'])) . '</i><br>';
+                $content .= $entry['content'] .'<hr><br>';
+            }
+        }
+
+        return $content;
+    }
+
+    public static function isClosed($topic_id)
+    {
+        foreach(ForumEntry::getPathToPosting($topic_id) as $entry) {
+            if ($entry['closed']) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    /**
+     * Export available data of a given user into a storage object
+     * (an instance of the StoredUserData class) for that user.
+     *
+     * @param StoredUserData $storage object to store data into
+     */
+    public static function exportUserData(StoredUserData $storage)
+    {
+        $field_data = DBManager::get()->fetchAll("SELECT * FROM forum_entries WHERE user_id = ?", [$storage->user_id]);
+        if ($field_data) {
+            $storage->addTabularData(_('Forum Einträge'), 'forum_entries', $field_data);
+        }
+    }
+
+}
diff --git a/lib/classes/ForumFavorite.php b/lib/classes/ForumFavorite.php
new file mode 100644
index 0000000..9ffebf5
--- /dev/null
+++ b/lib/classes/ForumFavorite.php
@@ -0,0 +1,41 @@
+<?php
+/**
+ * ForumFavorite.php - Add and remove favorite postings
+ *
+ * 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 3 of
+ * the License, or (at your option) any later version.
+ *
+ * @author      Till Glöggler <tgloeggl@uos.de>
+ * @license     http://www.gnu.org/licenses/gpl-3.0.html GPL version 3
+ * @category    Stud.IP
+ */
+
+class ForumFavorite {
+    
+    /**
+     * Set the topic denoted by the passed id as favorite for the 
+     * currently logged in user
+     * 
+     * @param string $topic_id
+     */
+    static function set($topic_id) {
+        $stmt = DBManager::get()->prepare("REPLACE INTO
+            forum_favorites (topic_id, user_id)
+            VALUES (?, ?)");
+        $stmt->execute([$topic_id, $GLOBALS['user']->id]);
+    }
+
+    /**
+     * Remove the topic denoted by the passed id as favorite for the 
+     * currently logged in user
+     * 
+     * @param string $topic_id
+     */
+    static function remove($topic_id) {
+        $stmt = DBManager::get()->prepare("DELETE FROM forum_favorites
+            WHERE topic_id = ? AND user_id = ?");
+        $stmt->execute([$topic_id, $GLOBALS['user']->id]);        
+    }
+}
\ No newline at end of file
diff --git a/lib/classes/ForumHelpers.php b/lib/classes/ForumHelpers.php
new file mode 100644
index 0000000..ed478ad
--- /dev/null
+++ b/lib/classes/ForumHelpers.php
@@ -0,0 +1,282 @@
+<?php
+/**
+ * ForumHelpers.php - Some useful helpers for the forum
+ *
+ * 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 3 of
+ * the License, or (at your option) any later version.
+ *
+ * @author      Till Glöggler <tgloeggl@uos.de>
+ * @license     http://www.gnu.org/licenses/gpl-3.0.html GPL version 3
+ * @category    Stud.IP
+ */
+
+class ForumHelpers {
+
+    /**
+     * The page for the current script run, modified by a global page-handle
+     * @var int
+     */
+    static $page = 1;
+
+    /**
+     * helper_function for highlight($text, $highlight)
+     *
+     * @param  string  $text
+     * @param  array   $highlight
+     * @return string
+     */
+    public static function do_highlight($text, $highlight)
+    {
+        foreach ($highlight as $hl) {
+            $text = preg_replace(
+                '/' . preg_quote(htmlReady($hl), '/') . '/i',
+                '<span class="highlight">$0</span>',
+                $text
+            );
+        }
+        return $text;
+    }
+
+    /**
+     * This function highlights Text HTML-safe
+     * (tags or words in tags are not highlighted, words between tags ARE highlighted)
+     *
+     * @param string $text the text where to words shall be highlighted, may contain tags
+     * @param array $highlight an array of words to be highlighted
+     * @return string the highlighted text
+     */
+    public static function highlight($text, $highlight)
+    {
+        if (empty($highlight)) {
+            return $text;
+        }
+
+        $data = [];
+        $treffer = [];
+
+        // split text at every tag
+        $pattern = '/<[^<]*>/U';
+        preg_match_all($pattern, $text, $treffer, PREG_OFFSET_CAPTURE);
+
+        if (sizeof($treffer[0]) == 0) {
+            return self::do_highlight($text, $highlight);
+        }
+
+        // cycle trough the text between the tags and highlight all hits
+        $last_pos = 0;
+        foreach ($treffer[0] as $taginfo) {
+            $size = mb_strlen($taginfo[0]);
+            if ($taginfo[1] != 0) {
+                $data[] = self::do_highlight(mb_substr($text, $last_pos, $taginfo[1] - $last_pos), $highlight);
+            }
+
+            $data[] = mb_substr($text, $taginfo[1], $size);
+            $last_pos = $taginfo[1] + $size;
+        }
+
+        // don't miss the last portion of a posting
+        if ($last_pos < mb_strlen($text)) {
+            $data[] = self::do_highlight(mb_substr($text, $last_pos, mb_strlen($text) - $last_pos), $highlight);
+        }
+
+        return implode('', $data);
+    }
+
+    /**
+     * Returns a human-readable version of the passed global Stud.IP permission.
+     *
+     * @param  string  $perm
+     * @return string
+     */
+    public static function translate_perm($perm)
+    {
+        $mapping = [
+            'root'   => _('Root'),
+            'admin'  => _('Administrator/-in'),
+            'dozent' => _('Lehrende/-r'),
+            'tutor'  => _('Tutor/-in'),
+            'autor'  => _('Autor/-in'),
+            'user'   => _('Leser/-in'),
+        ];
+
+        // TODO: Activate next when devboard reliably runs on PHP7
+        // return $mapping[$perm] ?? '';
+
+        return isset($mapping[$perm]) ? $mapping[$perm] : '';
+    }
+
+    /**
+     * return the currently chosen page
+     *
+     * @return  int
+     */
+    public static function getPage()
+    {
+        return self::$page;
+    }
+
+    /**
+     * set the current page
+     *
+     * @param int $page_num the page
+     */
+    public static function setPage($page_num)
+    {
+        self::$page = $page_num;
+    }
+
+    /**
+     * Return an info-text explaining the visit-status of the passed topic_di
+     * which has the passed number of new entries.
+     *
+     * @param string $num_entries  the number of new entries
+     * @param string $topic_id     the id of the topic
+     *
+     * @return string  a human readable, localized text
+     */
+    public static function getVisitText($num_entries, $topic_id)
+    {
+        if ($num_entries > 0) {
+            $text = sprintf(_('Seit Ihrem letzten Besuch gibt es %s neue Beiträge'), $num_entries);
+        } else {
+            $all_entries = ForumEntry::countPostings($topic_id);
+
+            if ($all_entries == 0) {
+                $text = sprintf(_('Es gibt bisher keine Beiträge.'));
+            } else if ($all_entries == 1) {
+                $text = sprintf(_('Seit Ihrem letzten Besuch gab es nichts Neues.'
+                      . ' Es ist ein alter Beitrag vorhanden.'));
+            } else {
+                $text = sprintf(_('Seit Ihrem letzten Besuch gab es nichts Neues.'
+                      . ' Es sind %s alte Beiträge vorhanden.'), $all_entries);
+            }
+        }
+
+        return $text;
+    }
+
+    /**
+     * return the online status of the passed user, one of three possible
+     * states is returned:
+     *  - available
+     *  - away
+     *  - offline
+     *
+     * @staticvar type $online_status
+     *
+     * @param string $user_id
+     *
+     * @return string
+     */
+    public static function getOnlineStatus($user_id)
+    {
+        static $online_status;
+
+        // check if the corresponding user's profile is visible
+        if (get_visibility_by_id($user_id) == false) {
+            return 'offline';
+        }
+
+        if ($GLOBALS['user']->id == $user_id) {
+            return 'available';
+        }
+
+        if (!$online_status) {
+            $online_users = get_users_online(10);
+            foreach ($online_users as $username => $data) {
+                if ($data['last_action'] >= 300) {
+                    $online_status[$data['user_id']] = 'away';
+                } else {
+                    $online_status[$data['user_id']] = 'available';
+                }
+            }
+        }
+
+        return $online_status[$user_id] ?: 'offline';
+    }
+
+    /**
+     * Create a pdf of all postings belonging to the passed seminar located
+     * under the passed topic_id. The PDF is dispatched automatically.
+     *
+     * BEWARE: This function never returns, it dies after the PDF has been
+     * (succesfully or not) dispatched.
+     *
+     * @param string $seminar_id
+     * @param string $parent_id
+     */
+    public static function createPdf($seminar_id, $parent_id = null)
+    {
+        $seminar_name = get_object_name($seminar_id, 'sem');
+        $data = ForumEntry::getList('dump', $parent_id ?: $seminar_id);
+        $first_page = true;
+
+        $document = new ExportPDF();
+        $document->SetTitle(_('Forum'));
+        $document->setHeaderTitle(sprintf(_("Forum \"%s\""), $seminar_name['name']));
+        $document->addPage();
+
+        foreach ($data as $entry) {
+            if (Config::get()->FORUM_ANONYMOUS_POSTINGS && $entry['anonymous']) {
+                $author = _('anonym');
+            } else {
+                $author = $entry['author'];
+            }
+            if ($entry['depth'] == 1) {
+                if (!$first_page) {
+                    $document->addPage();
+                }
+                $first_page = false;
+                $document->addContent('!! '. _('Bereich') . ": {$entry['name_raw']}\n");
+                $document->addContent($entry['content_raw']);
+                $document->addContent("\n\n");
+            } else if ($entry['depth'] == 2) {
+                $document->addContent('! '. _('Thema') . ": {$entry['name_raw']}\n");
+                $document->addContent('%%' . sprintf(_('erstellt von %s am %s'), $author,
+                    strftime('%A %d. %B %Y, %H:%M', (int)$entry['mkdate'])) . '%%' . "\n");
+                $document->addContent($entry['content_raw']);
+                $document->addContent("\n--\n");
+            } else if ($entry['depth'] == 3) {
+                $document->addContent("**{$entry['name_raw']}**\n");
+                $document->addContent('%%' . sprintf(_('erstellt von %s am %s'), $author,
+                    strftime('%A %d. %B %Y, %H:%M', (int)$entry['mkdate'])) . '%%' . "\n");
+                $document->addContent($entry['content_raw']);
+                $document->addContent("\n--\n");
+            }
+        }
+
+        $document->dispatch($seminar_name['name'] ." - Forum");
+        die;
+    }
+
+
+    /**
+     * Returns the id of the currently selected seminar or false, if no seminar
+     * is selected
+     *
+     * @return mixed  seminar_id or false
+     */
+    public static function getSeminarId()
+    {
+        return Context::getId();
+    }
+
+    /**
+     * replace in the passed text every %%% with <% and every ### with %>
+     * This is used to work around a limitation of the Button-API in combination
+     * with the underscore.js way of inserting template vars.
+     *
+     * The Button-API correctly replaces < > with tags, but underscore.js is
+     * unable to find them in their tag-represenation
+     *
+     * @param string $text the text to apply the replacements on
+     *
+     * @return string the modified text
+     */
+    public static function replace($text)
+    {
+        return str_replace('%%%', '<%', str_replace('###', '%>', $text));
+    }
+}
diff --git a/lib/classes/ForumIssue.php b/lib/classes/ForumIssue.php
new file mode 100644
index 0000000..8be894f
--- /dev/null
+++ b/lib/classes/ForumIssue.php
@@ -0,0 +1,96 @@
+<?php
+/**
+ * ForumIssue.php - Manage issues linked to postings
+ *
+ * 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 3 of
+ * the License, or (at your option) any later version.
+ *
+ * @author      Till Glöggler <tgloeggl@uos.de>
+ * @license     http://www.gnu.org/licenses/gpl-3.0.html GPL version 3
+ * @category    Stud.IP
+ */
+
+class ForumIssue
+{
+    /**
+     * Get the id of the topic linked to the issue denoted by the passed id.
+     *
+     * @param string $issue_id
+     * @return string  the id of the linked topic
+     */
+    static function getThreadIdForIssue($issue_id)
+    {
+        $stmt = DBManager::get()->prepare("SELECT topic_id FROM forum_entries_issues
+            WHERE issue_id = ?");
+        $stmt->execute([$issue_id]);
+
+        return ($stmt->fetchColumn());
+    }
+
+
+    /**
+     * Get the id of the issue linked to the topic denoted by the passed id.
+     * 
+     * @param string $topic_id
+     * @return string  the id of the linked topic
+     */
+    static function getIssueIdForThread($topic_id)
+    {
+        $stmt = DBManager::get()->prepare("SELECT issue_id FROM forum_entries_issues
+            WHERE topic_id = ?");
+        $stmt->execute([$topic_id]);
+        
+        return ($stmt->fetchColumn());
+    }
+
+
+    /**
+     * Create/Update the linked posting for the passed issue_id
+     *
+     * @param string $seminar_id
+     * @param string $issue_id    issue id to link to
+     * @param string $title       (new) title of the posting
+     * @param string $content     (new) content of the posting
+     */
+    static function setThreadForIssue($seminar_id, $issue_id, $title, $content)
+    {
+        if ($topic_id = self::getThreadIdForIssue($issue_id)) {   // update
+            ForumEntry::update($topic_id, $title ?: _('Ohne Titel'), $content);
+
+        } else {                                                  // create
+            // make sure the forum is set up properly
+            ForumEntry::checkRootEntry($seminar_id);
+
+            $topic_id = md5(uniqid(rand()));
+
+            ForumEntry::insert([
+                'topic_id'    => $topic_id,
+                'seminar_id'  => $seminar_id,
+                'user_id'     => $GLOBALS['user']->id,
+                'name'        => $title ?: _('Ohne Titel'),
+                'content'     => $content,
+                'author'      => get_fullname($GLOBALS['user']->id),
+                'author_host' => ($GLOBALS['user']->id == 'nobody') ? getenv('REMOTE_ADDR') : ''
+            ], $seminar_id);
+
+            $stmt = DBManager::get()->prepare("INSERT INTO forum_entries_issues
+                (issue_id, topic_id) VALUES (?, ?)");
+            $stmt->execute([$issue_id, $topic_id]);
+        }
+    }
+
+    /**
+     * Remove the link for the posting denoted by the passed topic_id
+     *
+     * @param object $notification
+     * @param string $topic_id
+     */
+    static function unlinkIssue($notification, $topic_id)
+    {
+        $stmt = DBManager::get()->prepare("DELETE FROM forum_entries_issues
+            WHERE topic_id = ?");
+        $stmt->execute([$topic_id]);
+    }
+}
diff --git a/lib/classes/ForumLike.php b/lib/classes/ForumLike.php
new file mode 100644
index 0000000..24cb478
--- /dev/null
+++ b/lib/classes/ForumLike.php
@@ -0,0 +1,99 @@
+<?php
+/**
+ * ForumLike.php - Manage the likes for postings
+ *
+ * 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 3 of
+ * the License, or (at your option) any later version.
+ *
+ * @author      Till Glöggler <tgloeggl@uos.de>
+ * @license     http://www.gnu.org/licenses/gpl-3.0.html GPL version 3
+ * @category    Stud.IP
+ */
+
+class ForumLike {
+    
+    /**
+     * Set the posting denoted by the passed topic_id as liked for the
+     * currently logged in user
+     * 
+     * @param string $topic_id
+     */
+    static function like($topic_id) {
+        $stmt = DBManager::get()->prepare("REPLACE INTO
+            forum_likes (topic_id, user_id)
+            VALUES (?, ?)");
+        $stmt->execute([$topic_id, $GLOBALS['user']->id]);
+    
+        // get posting owner
+        $data = ForumEntry::getConstraints($topic_id);
+        
+        // notify owner of posting about the like
+        setTempLanguage($data['user_id']);
+        $notification = get_fullname($GLOBALS['user']->id) . _(' gefällt einer deiner Forenbeiträge!');
+        restoreLanguage();
+        
+        PersonalNotifications::add(
+            $data['user_id'], URLHelper::getURL('dispatch.php/course/forum/index/index/' . $topic_id .'?highlight_topic='. $topic_id .'#'. $topic_id),
+            $notification, $topic_id,
+            Icon::create('forum', 'clickable')
+        );
+    }
+    
+    /**
+     * Revoke the liking of the posting denoted by the passed topic_id for the
+     * currently logged in user
+     * 
+     * @param string $topic_id
+     */
+    static function dislike($topic_id) {
+        $stmt = DBManager::get()->prepare("DELETE FROM forum_likes
+            WHERE topic_id = ? AND user_id = ?");
+        $stmt->execute([$topic_id, $GLOBALS['user']->id]);        
+    }
+    
+    /**
+     * Get the user_id for all likers of the topic denoted by the passed id
+     * 
+     * @param string $topic_id
+     * @return array  an array of user_id's
+     */
+    static function getLikes($topic_id) {
+        $stmt = DBManager::get()->prepare("SELECT 
+            auth_user_md5.user_id FROM forum_likes
+            LEFT JOIN auth_user_md5 USING (user_id)
+            LEFT JOIN user_info USING (user_id)
+            WHERE topic_id = ?");
+        $stmt->execute([$topic_id]);
+        
+        return $stmt->fetchAll(PDO::FETCH_COLUMN);
+    }
+    
+    /**
+     * count the number of likes the user has received - system-wide
+     * 
+     * @staticvar type $entries
+     * @param string $user_id  the user's id to count the received likes for
+     * 
+     * @return int  the number of likes received
+     */
+    static function receivedForUser($user_id)
+    {
+        static $entries;
+
+        if (!$entries[$user_id]) {
+            $stmt = DBManager::get()->prepare("SELECT COUNT(*)
+                FROM forum_entries
+                LEFT JOIN forum_likes USING (topic_id)
+                WHERE forum_entries.user_id = ?
+                    AND forum_likes.topic_id IS NOT NULL
+                    AND forum_likes.user_id != ?");
+            $stmt->execute([$user_id, $user_id]);
+
+            $entries[$user_id] = $stmt->fetchColumn();
+        }
+
+        return $entries[$user_id];
+    }
+}
diff --git a/lib/classes/ForumPerm.php b/lib/classes/ForumPerm.php
new file mode 100644
index 0000000..a5441fa
--- /dev/null
+++ b/lib/classes/ForumPerm.php
@@ -0,0 +1,215 @@
+<?php
+/**
+ * filename - Short description for file
+ *
+ * Long description for file (if any)...
+ *
+ * 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 3 of
+ * the License, or (at your option) any later version.
+ *
+ * @author      Till Glöggler <tgloeggl@uos.de>
+ * @license     http://www.gnu.org/licenses/gpl-3.0.html GPL version 3
+ * @category    Stud.IP
+ */
+
+class ForumPerm {
+
+    /**
+     * Check, if the a user has the passed permission in a seminar.
+     * Possible permissions are:
+     *   edit_category     - Editing the name of a category<br>
+     *   add_category      - Adding a new category<br>
+     *   remove_category   - Removing an existing category<br>
+     *   sort_category     - Sorting categories<br>
+     *   edit_area         - Editing an area (title + content)<br>
+     *   add_area          - Adding a new area<br>
+     *   remove_area       - Removing an area and all belonging threads<br>
+     *   sort_area         - Sorting of areas in categories and between categories<br>
+     *   search            - Searching in postings<br>
+     *   edit_entry        - Editing of foreign threads/postings<br>
+     *   add_entry         - Creating a new thread/posting<br>
+     *   remove_entry      - Removing of foreign threads/postings<br>
+     *   fav_entry         - Marking a Posting as "favorite"<br>
+     *   like_entry        - Liking a posting<br>
+     *   move_thread       - Moving a thrad between ares<br>
+     *   close_thread      - Close or open a thread<br>
+     *   make_sticky       - Make a thread sticky<br>
+     *   abo               - Signing up for mail-notifications for new entries<br>
+     *   forward_entry     - Forwarding an existing entry as a message<br>
+     *   pdfexport         - Exporting parts of the forum as PDF<br>
+     *   admin             - Allowed to mass-administrate the forum<br>
+     *   view              - Allowed to view the forum at all<br>
+     *   edit_closed       - Editing entries in a closed thread
+     *
+     * @param string $perm        one of the modular permissions
+     * @param string $seminar_id  the seminar to check for
+     * @param string $user_id     the user to check for
+     * @return boolean  true, if the user has the perms, false otherwise
+     */
+    public static function has($perm, $seminar_id, $user_id = null)
+    {
+        static $permissions = [];
+
+        // if no user-id is passed, use the current user (for your convenience)
+        if (!$user_id) {
+            $user_id = $GLOBALS['user']->id;
+        }
+
+        // get the status for the user in the passed seminar
+        if (!$permissions[$seminar_id][$user_id]) {
+            $permissions[$seminar_id][$user_id] = $GLOBALS['perm']->get_studip_perm($seminar_id, $user_id);
+        }
+
+        $status = $permissions[$seminar_id][$user_id];
+
+        // take care of the not logged in user
+        if ($user_id == 'nobody' || $status == false) {
+            // which status has nobody - read only or read/write?
+            if (get_object_type($seminar_id) == 'sem') {
+                $sem = Seminar::getInstance($seminar_id);
+
+                if ($sem->write_level == 0) {
+                    $status = 'nobody_write';
+                } else if ($sem->read_level == 0) {
+                    $status = 'nobody_read';
+                } else {
+                    return false;
+                }
+            } else {
+                return false;
+            }
+        }
+
+        // root and admins have all possible perms
+        if (in_array($status, words('root admin')) !== false) {
+            return true;
+        }
+
+        // eCULT Notlösung
+        if ($status == 'tutor' && $seminar_id == '30e0b89dcc9173d5fccf9f22b13b87bd') {
+            $status = 'autor';
+        }
+
+        // check the status and the passed permission
+        if (($status == 'dozent' || $status == 'tutor') && in_array($perm,
+            words('edit_category add_category remove_category sort_category '
+            . 'edit_area add_area remove_area sort_area '
+            . 'search edit_entry add_entry remove_entry fav_entry like_entry move_thread '
+            . 'make_sticky close_thread abo forward_entry pdfexport view edit_closed')
+        ) !== false) {
+            return true;
+        } else if ($status == 'autor' && in_array($perm, words('search add_entry fav_entry like_entry forward_entry abo pdfexport view')) !== false) {
+            return true;
+        } else if ($status == 'user' && in_array($perm, words('search forward_entry pdfexport view')) !== false) {
+            return true;
+        } else if ($status == 'nobody_write' && in_array($perm, words('search add_entry pdfexport view')) !== false) {
+            return true;
+        } else if ($status == 'nobody_read' && in_array($perm, words('search pdfexport view')) !== false) {
+            return true;
+        }
+
+        // user has no permission
+        return false;
+    }
+
+    /**
+     * If the user has not the passed perm in a seminar, an AccessDeniedException
+     * is thrown.
+     * An optional topic_id can be passed which is checked against the passed
+     * seminar if the topic_id belongs to that seminar
+     *
+     * @param string $perm        for the list of possible perms and their function see @ForumPerm::hasPerm()
+     * @param string $seminar_id  the seminar to check for
+     * @param string $topic_id    if passed, this topic_id is checked if it belongs to the passed seminar
+     *
+     * @throws AccessDeniedException
+     */
+    public static function check($perm, $seminar_id, $topic_id = null)
+    {
+        if (!self::has($perm, $seminar_id)) {
+            throw new AccessDeniedException(sprintf(
+                _("Sie haben keine Berechtigung für diese Aktion! Benötigte Berechtigung: %s"),
+                $perm)
+            );
+        }
+
+        // check the topic id (if any)
+        if ($topic_id) {
+            self::checkTopicId($seminar_id, $topic_id);
+        }
+    }
+
+    /**
+     * Check if the current user is allowed to edit the topic
+     *  denoted by the passed id
+     *
+     * @staticvar array $perms
+     *
+     * @param string $topic_id the id for the topic to check for
+     *
+     * @return bool true if the user has the necessary perms, false otherwise
+     */
+    public static function hasEditPerms($topic_id)
+    {
+        static $perms = [];
+
+        if (!$perms[$topic_id]) {
+            // find out if the posting is the last in the thread
+            $constraints = ForumEntry::getConstraints($topic_id);
+
+            $stmt = DBManager::get()->prepare("SELECT user_id, seminar_id
+                FROM forum_entries WHERE topic_id = ?");
+            $stmt->execute([$topic_id]);
+
+            $data = $stmt->fetch();
+
+            $closed = ForumEntry::isClosed($topic_id);
+
+            $perms[$topic_id] = (($GLOBALS['user']->id == $data['user_id'] && $GLOBALS['user']->id != 'nobody') ||
+                ForumPerm::has('edit_entry', $constraints['seminar_id']))
+                    && (!$closed || $closed && ForumPerm::has('edit_closed', $constraints['seminar_id']));
+        }
+
+        return $perms[$topic_id];
+    }
+
+    /**
+     * check if the passed category_id belongs to the passed seminar_id.
+     * Throws an AccessDenied denied exception if this is not the case
+     *
+     * @param string $seminar_id   id of the seminar, the category should belong to
+     * @param string $category_id  the id of the category to check
+     */
+    public static function checkCategoryId($seminar_id, $category_id)
+    {
+        $data = ForumCat::get($category_id);
+
+        if ($data['seminar_id'] != $seminar_id) {
+            throw new AccessDeniedException(sprintf(
+                _('Forum: Sie haben keine Berechtigung auf die Kategorie mit der ID %s zuzugreifen!'),
+                $category_id
+            ));
+        }
+    }
+
+    /**
+     * check if the passed topic_id belongs to the passed seminar_id.
+     * Throws an AccessDenied denied exception if this is not the case
+     *
+     * @param string $seminar_id  id of the seminar, the category should belong to
+     * @param string $topic_id    the id of the topic to check
+     */
+    public static function checkTopicId($seminar_id, $topic_id)
+    {
+        $data = ForumEntry::getConstraints($topic_id);
+
+        if ($data['seminar_id'] != $seminar_id) {
+            throw new AccessDeniedException(sprintf(
+                _('Forum: Sie haben keine Berechtigung auf den Eintrag mit der ID %s zuzugreifen!'),
+                $topic_id
+            ));
+        }
+    }
+}
diff --git a/lib/classes/ForumVisit.php b/lib/classes/ForumVisit.php
new file mode 100644
index 0000000..befe116
--- /dev/null
+++ b/lib/classes/ForumVisit.php
@@ -0,0 +1,162 @@
+<?php
+/**
+ * ForumVisit - Functions for visit-dates for threads
+ *
+ * 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 3 of
+ * the License, or (at your option) any later version.
+ *
+ * @author      Till Glöggler <tgloeggl@uos.de>
+ * @license     http://www.gnu.org/licenses/gpl-3.0.html GPL version 3
+ * @category    Stud.IP
+ */
+
+class ForumVisit {
+
+    /**
+     * This is the maximum number of seconds that unread entries are
+     * marked as new.
+     */
+    const LAST_VISIT_MAX = 7776000; // 90 days
+
+    /**
+     * return number of new entries since last visit up to 3 month ago
+     *
+     * @param string $parent_id the seminar_id for the entries
+     * @param string $visitdate count all entries newer than this timestamp
+     *
+     * @return int the number of entries
+     */
+    static function getCount($parent_id, $visitdate)
+    {
+        if ($visitdate < time() - ForumVisit::LAST_VISIT_MAX) {
+            $visitdate = time() - ForumVisit::LAST_VISIT_MAX;
+        }
+
+        $constraints = ForumEntry::getConstraints($parent_id);
+
+        $stmt = DBManager::get()->prepare("SELECT COUNT(*) FROM forum_entries
+            WHERE lft >= :lft AND rgt <= :rgt AND user_id != :user_id
+                AND seminar_id = :seminar_id
+                AND topic_id != seminar_id
+                AND chdate > :lastvisit");
+
+        $stmt->bindParam(':user_id', $GLOBALS['user']->id);
+        $stmt->bindParam(':lft', $constraints['lft']);
+        $stmt->bindParam(':rgt', $constraints['rgt']);
+        $stmt->bindParam(':seminar_id', $constraints['seminar_id']);
+        $stmt->bindParam(':lastvisit', $visitdate);
+
+        $stmt->execute();
+
+        return $stmt->fetchColumn();
+    }
+
+    /**
+     * Set the seminar denoted by the passed id as visited by the currently
+     * logged in user
+     *
+     * @param string $seminar_id
+     */
+    static function setVisit($seminar_id) {
+        $type = get_object_type($seminar_id, words('fak inst sem'));
+        if ($type === 'fak') {
+            $type = 'inst';
+        }
+        if (self::getVisit($seminar_id) < object_get_visit($seminar_id, $type, false, false)) {
+            self::setVisitdates($seminar_id);
+        }
+    }
+
+    /**
+     * Stores the visitdate in last_visitdate and sets the current time for as new visitdate
+     *
+     * @param string $seminar_id the seminar that has been entered
+     */
+    static function setVisitdates($seminar_id) {
+        $stmt = DBManager::get()->prepare('SELECT visitdate FROM forum_visits
+            WHERE user_id = ? AND seminar_id = ?');
+        $stmt->execute([$GLOBALS['user']->id, $seminar_id]);
+        $visitdate = $stmt->fetchColumn();
+
+        $stmt = DBManager::get()->prepare("REPLACE INTO forum_visits
+            (user_id, seminar_id, visitdate, last_visitdate)
+            VALUES (?, ?, UNIX_TIMESTAMP(), ?)");
+        $stmt->execute([$GLOBALS['user']->id, $seminar_id, $visitdate]);
+
+    }
+
+
+    /**
+     * returns visitdate and last_visitdate for the passed seminar and the
+     * currently logged in user
+     *
+     * @staticvar array $visit
+     *
+     * @param string $seminar_id the seminar to fetch the visitdates for
+     * @return mixed an array containing visitdate and last_visitdate
+     */
+    private static function getVisitDates($seminar_id)
+    {
+        static $visit = [];
+
+        // no costly checking for root or nobody necessary
+        if ($GLOBALS['perm']->have_perm('root') || $GLOBALS['user']->id == 'nobody') {
+            $tstamp = mktime(23, 59, 00, date('m'), 31, date('y'));
+            return ['visit' => $tstamp, 'last_visitdate' => $tstamp];
+        }
+
+        if (!isset($visit[$seminar_id])) {
+            $visit[$seminar_id] = [];
+        }
+        if (!isset($visit[$seminar_id][$GLOBALS['user']->id])) {
+            $stmt = DBManager::get()->prepare("SELECT visitdate, last_visitdate FROM forum_visits
+                WHERE seminar_id = ? AND user_id = ?");
+            $stmt->execute([$seminar_id, $GLOBALS['user']->id]);
+            $visit[$seminar_id][$GLOBALS['user']->id] = $stmt->fetch(PDO::FETCH_ASSOC);
+
+            // no entry for this seminar yet present
+            if (!$visit[$seminar_id][$GLOBALS['user']->id]) {
+                // set visitdate to current time
+                $visit[$seminar_id][$GLOBALS['user']->id] = [
+                    'visit'      => time() - ForumVisit::LAST_VISIT_MAX,
+                    'last_visitdate' => time() - ForumVisit::LAST_VISIT_MAX
+                ];
+            }
+
+            // prevent visit-dates from being older than LAST_VISIT_MAX allows
+            foreach ($visit[$seminar_id][$GLOBALS['user']->id] as $type => $date) {
+                if ($date < time() - ForumVisit::LAST_VISIT_MAX) {
+                    $visit[$seminar_id][$GLOBALS['user']->id][$type] = time() - ForumVisit::LAST_VISIT_MAX;
+                }
+            }
+        }
+
+        return $visit[$seminar_id][$GLOBALS['user']->id];
+    }
+
+    /**
+     * return the last_visitdate for the passed seminar and currently logged in user
+     *
+     * @param string $seminar_id the seminar to get the last_visitdate for
+     * @return int a timestamp
+     */
+    static function getLastVisit($seminar_id)
+    {
+        $visit = self::getVisitDates($seminar_id);
+        return $visit['last_visitdate'];
+    }
+
+    /**
+     * return the visitdate for the passed seminar and currently logged in user
+     *
+     * @param string $seminar_id the seminar to get the visitdate for
+     * @return int a timestamp
+     */
+    static function getVisit($seminar_id)
+    {
+        $visit = self::getVisitDates($seminar_id);
+        return $visit['visitdate'];
+    }
+}
diff --git a/lib/classes/JsonApi/Routes/Forum/ForumAuthority.php b/lib/classes/JsonApi/Routes/Forum/ForumAuthority.php
index c895a7b..acc5d2a 100644
--- a/lib/classes/JsonApi/Routes/Forum/ForumAuthority.php
+++ b/lib/classes/JsonApi/Routes/Forum/ForumAuthority.php
@@ -8,8 +8,6 @@ class ForumAuthority
 {
     public static function has(\User $user, $perm, \Course $course, ForumEntry $topic = null)
     {
-        require_once 'public/plugins_packages/core/Forum/models/ForumPerm.php';
-
         if (!\ForumPerm::has($perm, $course->id, $user->id)) {
             return false;
         }
diff --git a/lib/classes/JsonApi/Routes/Forum/ForumCategoriesShow.php b/lib/classes/JsonApi/Routes/Forum/ForumCategoriesShow.php
index 9e935e0..190efb2 100644
--- a/lib/classes/JsonApi/Routes/Forum/ForumCategoriesShow.php
+++ b/lib/classes/JsonApi/Routes/Forum/ForumCategoriesShow.php
@@ -2,8 +2,6 @@
 
 namespace JsonApi\Routes\Forum;
 
-// require_once 'public/plugins_packages/core/Forum/models/ForumCat.php';
-
 use Psr\Http\Message\ServerRequestInterface as Request;
 use Psr\Http\Message\ResponseInterface as Response;
 use JsonApi\Errors\AuthorizationFailedException;
diff --git a/lib/classes/Privacy.php b/lib/classes/Privacy.php
index 90ba9f7..bb3bcdd 100644
--- a/lib/classes/Privacy.php
+++ b/lib/classes/Privacy.php
@@ -85,8 +85,6 @@ class Privacy
      */
     public static function getUserdataInformation($user_id, $section = null)
     {
-        //workaround make Forum Model available
-        PluginEngine::getPlugin('CoreForum');
         $storage = new StoredUserData($user_id);
 
         if ($section && !isset(self::$privacy_classes[$section])) {
diff --git a/lib/classes/globalsearch/GlobalSearchForum.php b/lib/classes/globalsearch/GlobalSearchForum.php
index 83558bd..37efd26 100644
--- a/lib/classes/globalsearch/GlobalSearchForum.php
+++ b/lib/classes/globalsearch/GlobalSearchForum.php
@@ -144,7 +144,7 @@ class GlobalSearchForum extends GlobalSearchModule implements GlobalSearchFullte
                 'id'          => $data['topic_id'],
                 'name'        => $name,
                 'url'         => URLHelper::getURL(
-                    "plugins.php/coreforum/index/index/{$data['topic_id']}#{$data['topic_id']}",
+                    "dispatch.php/course/forum/index/index/{$data['topic_id']}#{$data['topic_id']}",
                     ['cid' => $data['seminar_id'], 'highlight_topic' => $data['topic_id']],
                     true
                 ),
@@ -152,7 +152,7 @@ class GlobalSearchForum extends GlobalSearchModule implements GlobalSearchFullte
                 'date'        => strftime('%x', $data['chdate']),
                 'description' => self::mark($filtered_content, $search, true),
                 'additional'  => htmlReady($additional),
-                'expand' => URLHelper::getURL('plugins.php/coreforum/index/search', [
+                'expand' => URLHelper::getURL('dispatch.php/course/forum/index/search', [
                     'cid'            => $data['seminar_id'],
                     'backend'        => 'search',
                     'searchfor'      => $search,