<?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 (empty($entries[$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];
    }
}