friendica/src/Module/Item/Follow.php

<?php
/**
 * @copyright Copyright (C) 2010-2021, the Friendica project
 *
 * @license GNU AGPL version 3 or any later version
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 *
 */

namespace Friendica\Module\Item;

use Friendica\BaseModule;
use Friendica\Core\Session;
use Friendica\Core\System;
use Friendica\DI;
use Friendica\Model\Item;
use Friendica\Model\Post;
use Friendica\Network\HTTPException;

/**
 * Module for following threads
 */
class Follow extends BaseModule
{
	public static function rawContent()
	{
		$l10n = DI::l10n();

		if (!Session::isAuthenticated()) {
			throw new HttpException\ForbiddenException($l10n->t('Access denied.'));
		}

		if (empty(static::$parameters['id'])) {
			throw new HTTPException\BadRequestException();
		}

		$itemId = intval(static::$parameters['id']);

		if (!Item::performActivity($itemId, 'follow', local_user())) {
			throw new HTTPException\BadRequestException($l10n->t('Unable to follow this item.'));
		}

		// See if we've been passed a return path to redirect to
		$return_path = $_REQUEST['return'] ?? '';
		if (!empty($return_path)) {
			$rand = '_=' . time();
			if (strpos($return_path, '?')) {
				$rand = "&$rand";
			} else {
				$rand = "?$rand";
			}

			DI::baseUrl()->redirect($return_path . $rand);
		}

		$return = [
			'status' => 'ok',
			'item_id' => $itemId,
			'verb' => 'follow',
			'state' => 1
		];

		System::jsonExit($return);
	}
}