friendica/src/Content/Text/BBCode.php

<?php
/**
 * @copyright Copyright (C) 2020, Friendica
 *
 * @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\Content\Text;

use DOMDocument;
use DOMXPath;
use Exception;
use Friendica\Content\OEmbed;
use Friendica\Content\Smilies;
use Friendica\Core\Hook;
use Friendica\Core\Logger;
use Friendica\Core\Protocol;
use Friendica\Core\Renderer;
use Friendica\Core\System;
use Friendica\DI;
use Friendica\Model\Contact;
use Friendica\Model\Event;
use Friendica\Model\Photo;
use Friendica\Network\Probe;
use Friendica\Object\Image;
use Friendica\Protocol\Activity;
use Friendica\Util\Images;
use Friendica\Util\Map;
use Friendica\Util\Network;
use Friendica\Util\ParseUrl;
use Friendica\Util\Proxy as ProxyUtils;
use Friendica\Util\Strings;
use Friendica\Util\XML;

class BBCode
{
	const INTERNAL = 0;
	const API = 2;
	const DIASPORA = 3;
	const CONNECTORS = 4;
	const OSTATUS = 7;
	const TWITTER = 8;
	const BACKLINK = 8;
	const ACTIVITYPUB = 9;

	/**
	 * Fetches attachment data that were generated the old way
	 *
	 * @param string $body Message body
	 * @return array
	 *                     'type' -> Message type ('link', 'video', 'photo')
	 *                     'text' -> Text before the shared message
	 *                     'after' -> Text after the shared message
	 *                     'image' -> Preview image of the message
	 *                     'url' -> Url to the attached message
	 *                     'title' -> Title of the attachment
	 *                     'description' -> Description of the attachment
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 */
	private static function getOldAttachmentData($body)
	{
		$post = [];

		// Simplify image codes
		$body = preg_replace("/\[img\=([0-9]*)x([0-9]*)\](.*?)\[\/img\]/ism", '[img]$3[/img]', $body);

		if (preg_match_all("(\[class=(.*?)\](.*?)\[\/class\])ism", $body, $attached, PREG_SET_ORDER)) {
			foreach ($attached as $data) {
				if (!in_array($data[1], ['type-link', 'type-video', 'type-photo'])) {
					continue;
				}

				$post['type'] = substr($data[1], 5);

				$pos = strpos($body, $data[0]);
				if ($pos > 0) {
					$post['text'] = trim(substr($body, 0, $pos));
					$post['after'] = trim(substr($body, $pos + strlen($data[0])));
				} else {
					$post['text'] = trim(str_replace($data[0], '', $body));
					$post['after'] = '';
				}

				$attacheddata = $data[2];

				if (preg_match("/\[img\](.*?)\[\/img\]/ism", $attacheddata, $matches)) {

					$picturedata = Images::getInfoFromURLCached($matches[1]);

					if ($picturedata) {
						if (($picturedata[0] >= 500) && ($picturedata[0] >= $picturedata[1])) {
							$post['image'] = $matches[1];
						} else {
							$post['preview'] = $matches[1];
						}
					}
				}

				if (preg_match("/\[bookmark\=(.*?)\](.*?)\[\/bookmark\]/ism", $attacheddata, $matches)) {
					$post['url'] = $matches[1];
					$post['title'] = $matches[2];
				}
				if (!empty($post['url']) && (in_array($post['type'], ['link', 'video']))
					&& preg_match("/\[url\=(.*?)\](.*?)\[\/url\]/ism", $attacheddata, $matches)) {
					$post['url'] = $matches[1];
				}

				// Search for description
				if (preg_match("/\[quote\](.*?)\[\/quote\]/ism", $attacheddata, $matches)) {
					$post['description'] = $matches[1];
				}
			}
		}
		return $post;
	}

	/**
	 * Fetches attachment data that were generated with the "attachment" element
	 *
	 * @param string $body Message body
	 * @return array
	 *                     'type' -> Message type ('link', 'video', 'photo')
	 *                     'text' -> Text before the shared message
	 *                     'after' -> Text after the shared message
	 *                     'image' -> Preview image of the message
	 *                     'url' -> Url to the attached message
	 *                     'title' -> Title of the attachment
	 *                     'description' -> Description of the attachment
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 */
	public static function getAttachmentData($body)
	{
		$data = [
			'type'        => '',
			'text'        => '',
			'after'       => '',
			'image'       => null,
			'url'         => '',
			'title'       => '',
			'description' => '',
		];

		if (!preg_match("/(.*)\[attachment(.*?)\](.*?)\[\/attachment\](.*)/ism", $body, $match)) {
			return self::getOldAttachmentData($body);
		}

		$attributes = $match[2];

		$data['text'] = trim($match[1]);

		$type = '';
		preg_match("/type='(.*?)'/ism", $attributes, $matches);
		if (!empty($matches[1])) {
			$type = strtolower($matches[1]);
		}

		preg_match('/type="(.*?)"/ism', $attributes, $matches);
		if (!empty($matches[1])) {
			$type = strtolower($matches[1]);
		}

		if ($type == '') {
			return [];
		}

		if (!in_array($type, ['link', 'audio', 'photo', 'video'])) {
			return [];
		}

		if ($type != '') {
			$data['type'] = $type;
		}

		$url = '';
		preg_match("/url='(.*?)'/ism", $attributes, $matches);
		if (!empty($matches[1])) {
			$url = $matches[1];
		}

		preg_match('/url="(.*?)"/ism', $attributes, $matches);
		if (!empty($matches[1])) {
			$url = $matches[1];
		}

		if ($url != '') {
			$data['url'] = html_entity_decode($url, ENT_QUOTES, 'UTF-8');
		}

		$title = '';
		preg_match("/title='(.*?)'/ism", $attributes, $matches);
		if (!empty($matches[1])) {
			$title = $matches[1];
		}

		preg_match('/title="(.*?)"/ism', $attributes, $matches);
		if (!empty($matches[1])) {
			$title = $matches[1];
		}

		if ($title != '') {
			$title = self::convert(html_entity_decode($title, ENT_QUOTES, 'UTF-8'), false, true);
			$title = html_entity_decode($title, ENT_QUOTES, 'UTF-8');
			$title = str_replace(['[', ']'], ['&#91;', '&#93;'], $title);
			$data['title'] = $title;
		}

		$image = '';
		preg_match("/image='(.*?)'/ism", $attributes, $matches);
		if (!empty($matches[1])) {
			$image = $matches[1];
		}

		preg_match('/image="(.*?)"/ism', $attributes, $matches);
		if (!empty($matches[1])) {
			$image = $matches[1];
		}

		if ($image != '') {
			$data['image'] = html_entity_decode($image, ENT_QUOTES, 'UTF-8');
		}

		$preview = '';
		preg_match("/preview='(.*?)'/ism", $attributes, $matches);
		if (!empty($matches[1])) {
			$preview = $matches[1];
		}

		preg_match('/preview="(.*?)"/ism', $attributes, $matches);
		if (!empty($matches[1])) {
			$preview = $matches[1];
		}

		if ($preview != '') {
			$data['preview'] = html_entity_decode($preview, ENT_QUOTES, 'UTF-8');
		}

		$data['description'] = trim($match[3]);

		$data['after'] = trim($match[4]);

		return $data;
	}

	public static function getAttachedData($body, $item = [])
	{
		/*
		- text:
		- type: link, video, photo
		- title:
		- url:
		- image:
		- description:
		- (thumbnail)
		*/

		$has_title = !empty($item['title']);
		$plink = $item['plink'] ?? '';
		$post = self::getAttachmentData($body);

		// Get all linked images with alternative image description
		if (preg_match_all("/\[img=([^\[\]]*)\]([^\[\]]*)\[\/img\]/Usi", $body, $pictures, PREG_SET_ORDER)) {
			foreach ($pictures as $picture) {
				if (Photo::isLocal($picture[1])) {
					$post['images'][] = ['url' => str_replace('-1.', '-0.', $picture[1]), 'description' => $picture[2]];
				}
			}
			if (!empty($post['images']) && !empty($post['images'][0]['description'])) {
				$post['image_description'] = $post['images'][0]['description'];
			}
		}

		if (preg_match_all("/\[img\]([^\[\]]*)\[\/img\]/Usi", $body, $pictures, PREG_SET_ORDER)) {
			foreach ($pictures as $picture) {
				if (Photo::isLocal($picture[1])) {
					$post['images'][] = ['url' => str_replace('-1.', '-0.', $picture[1]), 'description' => ''];
				}
			}
		}

		// if nothing is found, it maybe having an image.
		if (!isset($post['type'])) {
			// Simplify image codes
			$body = preg_replace("/\[img\=([0-9]*)x([0-9]*)\](.*?)\[\/img\]/ism", '[img]$3[/img]', $body);
			$body = preg_replace("/\[img\=(.*?)\](.*?)\[\/img\]/ism", '[img]$1[/img]', $body);
			$post['text'] = $body;

			if (preg_match_all("#\[url=([^\]]+?)\]\s*\[img\]([^\[]+?)\[/img\]\s*\[/url\]#ism", $body, $pictures, PREG_SET_ORDER)) {
				if ((count($pictures) == 1) && !$has_title) {
					if (!empty($item['object-type']) && ($item['object-type'] == Activity\ObjectType::IMAGE)) {
						// Replace the preview picture with the real picture
						$url = str_replace('-1.', '-0.', $pictures[0][2]);
						$data = ['url' => $url, 'type' => 'photo'];
					} else {
						// Checking, if the link goes to a picture
						$data = ParseUrl::getSiteinfoCached($pictures[0][1], true);
					}

					// Workaround:
					// Sometimes photo posts to the own album are not detected at the start.
					// So we seem to cannot use the cache for these cases. That's strange.
					if (($data['type'] != 'photo') && strstr($pictures[0][1], "/photos/")) {
						$data = ParseUrl::getSiteinfo($pictures[0][1], true);
					}

					if ($data['type'] == 'photo') {
						$post['type'] = 'photo';
						if (isset($data['images'][0])) {
							$post['image'] = $data['images'][0]['src'];
							$post['url'] = $data['url'];
						} else {
							$post['image'] = $data['url'];
						}

						$post['preview'] = $pictures[0][2];
						$post['text'] = trim(str_replace($pictures[0][0], '', $body));
					} else {
						$imgdata = Images::getInfoFromURLCached($pictures[0][1]);
						if ($imgdata && substr($imgdata['mime'], 0, 6) == 'image/') {
							$post['type'] = 'photo';
							$post['image'] = $pictures[0][1];
							$post['preview'] = $pictures[0][2];
							$post['text'] = trim(str_replace($pictures[0][0], '', $body));
						}
					}
				} elseif (count($pictures) > 0) {
					$post['type'] = 'link';
					$post['url'] = $plink;
					$post['image'] = $pictures[0][2];
					$post['text'] = $body;

					foreach ($pictures as $picture) {
						$post['text'] = trim(str_replace($picture[0], '', $post['text']));
					}
				}
			} elseif (preg_match_all("(\[img\](.*?)\[\/img\])ism", $body, $pictures, PREG_SET_ORDER)) {
				if ((count($pictures) == 1) && !$has_title) {
					$post['type'] = 'photo';
					$post['image'] = $pictures[0][1];
					$post['text'] = str_replace($pictures[0][0], '', $body);
				} elseif (count($pictures) > 0) {
					$post['type'] = 'link';
					$post['url'] = $plink;
					$post['image'] = $pictures[0][1];
					$post['text'] = $body;

					foreach ($pictures as $picture) {
						$post['text'] = trim(str_replace($picture[0], '', $post['text']));
					}
				}
			}

			// Test for the external links
			preg_match_all("(\[url\](.*?)\[\/url\])ism", $post['text'], $links1, PREG_SET_ORDER);
			preg_match_all("(\[url\=(.*?)\].*?\[\/url\])ism", $post['text'], $links2, PREG_SET_ORDER);

			$links = array_merge($links1, $links2);

			// If there is only a single one, then use it.
			// This should cover link posts via API.
			if ((count($links) == 1) && !isset($post['preview']) && !$has_title) {
				$post['type'] = 'link';
				$post['url'] = $links[0][1];
			}

			// Simplify "video" element
			$post['text'] = preg_replace('(\[video.*?\ssrc\s?=\s?([^\s\]]+).*?\].*?\[/video\])ism', '[video]$1[/video]', $post['text']);

			// Now count the number of external media links
			preg_match_all("(\[vimeo\](.*?)\[\/vimeo\])ism", $post['text'], $links1, PREG_SET_ORDER);
			preg_match_all("(\[youtube\\](.*?)\[\/youtube\\])ism", $post['text'], $links2, PREG_SET_ORDER);
			preg_match_all("(\[video\\](.*?)\[\/video\\])ism", $post['text'], $links3, PREG_SET_ORDER);
			preg_match_all("(\[audio\\](.*?)\[\/audio\\])ism", $post['text'], $links4, PREG_SET_ORDER);

			// Add them to the other external links
			$links = array_merge($links, $links1, $links2, $links3, $links4);

			// Are there more than one?
			if (count($links) > 1) {
				// The post will be the type "text", which means a blog post
				unset($post['type']);
				$post['url'] = $plink;
			}

			if (!isset($post['type'])) {
				$post['type'] = "text";
				$post['text'] = trim($body);
			}
		} elseif (isset($post['url']) && ($post['type'] == 'video')) {
			$data = ParseUrl::getSiteinfoCached($post['url'], true);

			if (isset($data['images'][0])) {
				$post['image'] = $data['images'][0]['src'];
			}
		}

		return $post;
	}

	/**
	 * Remove [attachment] BBCode and replaces it with a regular [url]
	 *
	 * @param string  $body
	 * @param boolean $no_link_desc No link description
	 *
	 * @return string with replaced body
	 */
	public static function removeAttachment($body, $no_link_desc = false)
	{
		return preg_replace_callback("/\s*\[attachment (.*)\](.*?)\[\/attachment\]\s*/ism",
			function ($match) use ($no_link_desc) {
				$attach_data = self::getAttachmentData($match[0]);
				if (empty($attach_data['url'])) {
					return $match[0];
				} elseif (empty($attach_data['title']) || $no_link_desc) {
					return "\n[url]" . $attach_data['url'] . "[/url]\n";
				} else {
					return "\n[url=" . $attach_data['url'] . ']' . $attach_data['title'] . "[/url]\n";
				}
		}, $body);
	}

	/**
	 * Converts a BBCode text into plaintext
	 *
	 * @param      $text
	 * @param bool $keep_urls Whether to keep URLs in the resulting plaintext
	 *
	 * @return string
	 */
	public static function toPlaintext($text, $keep_urls = true)
	{
		$naked_text = HTML::toPlaintext(self::convert($text, false, 0, true), 0, !$keep_urls);

		return $naked_text;
	}

	private static function proxyUrl($image, $simplehtml = self::INTERNAL)
	{
		// Only send proxied pictures to API and for internal display
		if (in_array($simplehtml, [self::INTERNAL, self::API])) {
			return ProxyUtils::proxifyUrl($image);
		} else {
			return $image;
		}
	}

	/**
	 * This function changing the visual size (not the real size) of images.
	 * The function does not work for pictures with an alternate text description.
	 * This could only be changed by using some new "img" BBCode format.
	 *
	 * @param string $srctext The body with images
	 * @return string The body with possibly scaled images
	 */
	public static function scaleExternalImages(string $srctext)
	{
		$s = $srctext;

		// Simplify image links
		$s = preg_replace("/\[img\=([0-9]*)x([0-9]*)\](.*?)\[\/img\]/ism", '[img]$3[/img]', $s);

		$matches = null;
		$c = preg_match_all('/\[img.*?\](.*?)\[\/img\]/ism', $s, $matches, PREG_SET_ORDER);
		if ($c) {
			foreach ($matches as $mtch) {
				Logger::log('scale_external_image: ' . $mtch[1]);

				$hostname = str_replace('www.', '', substr(DI::baseUrl(), strpos(DI::baseUrl(), '://') + 3));
				if (stristr($mtch[1], $hostname)) {
					continue;
				}

				$curlResult = Network::curl($mtch[1], true);
				if (!$curlResult->isSuccess()) {
					continue;
				}

				$i = $curlResult->getBody();
				$type = $curlResult->getContentType();
				$type = Images::getMimeTypeByData($i, $mtch[1], $type);

				if ($i) {
					$Image = new Image($i, $type);
					if ($Image->isValid()) {
						$orig_width = $Image->getWidth();
						$orig_height = $Image->getHeight();

						if ($orig_width > 640 || $orig_height > 640) {
							$Image->scaleDown(640);
							$new_width = $Image->getWidth();
							$new_height = $Image->getHeight();
							Logger::log('scale_external_images: ' . $orig_width . '->' . $new_width . 'w ' . $orig_height . '->' . $new_height . 'h' . ' match: ' . $mtch[0], Logger::DEBUG);
							$s = str_replace(
								$mtch[0],
								'[img=' . $new_width . 'x' . $new_height. ']' . $mtch[1] . '[/img]'
								. "\n",
								$s
							);
							Logger::log('scale_external_images: new string: ' . $s, Logger::DEBUG);
						}
					}
				}
			}
		}

		return $s;
	}

	/**
	 * Truncates imported message body string length to max_import_size
	 *
	 * The purpose of this function is to apply system message length limits to
	 * imported messages without including any embedded photos in the length
	 *
	 * @param string $body
	 * @return string
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 */
	public static function limitBodySize($body)
	{
		$maxlen = DI::config()->get('config', 'max_import_size', 0);

		// If the length of the body, including the embedded images, is smaller
		// than the maximum, then don't waste time looking for the images
		if ($maxlen && (strlen($body) > $maxlen)) {

			Logger::log('the total body length exceeds the limit', Logger::DEBUG);

			$orig_body = $body;
			$new_body = '';
			$textlen = 0;

			$img_start = strpos($orig_body, '[img');
			$img_st_close = ($img_start !== false ? strpos(substr($orig_body, $img_start), ']') : false);
			$img_end = ($img_start !== false ? strpos(substr($orig_body, $img_start), '[/img]') : false);
			while (($img_st_close !== false) && ($img_end !== false)) {

				$img_st_close++; // make it point to AFTER the closing bracket
				$img_end += $img_start;
				$img_end += strlen('[/img]');

				if (!strcmp(substr($orig_body, $img_start + $img_st_close, 5), 'data:')) {
					// This is an embedded image

					if (($textlen + $img_start) > $maxlen) {
						if ($textlen < $maxlen) {
							Logger::log('the limit happens before an embedded image', Logger::DEBUG);
							$new_body = $new_body . substr($orig_body, 0, $maxlen - $textlen);
							$textlen = $maxlen;
						}
					} else {
						$new_body = $new_body . substr($orig_body, 0, $img_start);
						$textlen += $img_start;
					}

					$new_body = $new_body . substr($orig_body, $img_start, $img_end - $img_start);
				} else {

					if (($textlen + $img_end) > $maxlen) {
						if ($textlen < $maxlen) {
							Logger::log('the limit happens before the end of a non-embedded image', Logger::DEBUG);
							$new_body = $new_body . substr($orig_body, 0, $maxlen - $textlen);
							$textlen = $maxlen;
						}
					} else {
						$new_body = $new_body . substr($orig_body, 0, $img_end);
						$textlen += $img_end;
					}
				}
				$orig_body = substr($orig_body, $img_end);

				if ($orig_body === false) {
					// in case the body ends on a closing image tag
					$orig_body = '';
				}

				$img_start = strpos($orig_body, '[img');
				$img_st_close = ($img_start !== false ? strpos(substr($orig_body, $img_start), ']') : false);
				$img_end = ($img_start !== false ? strpos(substr($orig_body, $img_start), '[/img]') : false);
			}

			if (($textlen + strlen($orig_body)) > $maxlen) {
				if ($textlen < $maxlen) {
					Logger::log('the limit happens after the end of the last image', Logger::DEBUG);
					$new_body = $new_body . substr($orig_body, 0, $maxlen - $textlen);
				}
			} else {
				Logger::log('the text size with embedded images extracted did not violate the limit', Logger::DEBUG);
				$new_body = $new_body . $orig_body;
			}

			return $new_body;
		} else {
			return $body;
		}
	}

	/**
	 * Processes [attachment] tags
	 *
	 * Note: Can produce a [bookmark] tag in the returned string
	 *
	 * @param string  $text
	 * @param integer $simplehtml
	 * @param bool    $tryoembed
	 * @return string
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 */
	private static function convertAttachment($text, $simplehtml = self::INTERNAL, $tryoembed = true)
	{
		$data = self::getAttachmentData($text);
		if (empty($data) || empty($data['url'])) {
			return $text;
		}

		if (isset($data['title'])) {
			$data['title'] = strip_tags($data['title']);
			$data['title'] = str_replace(['http://', 'https://'], '', $data['title']);
		} else {
			$data['title'] = null;
		}

		if (((strpos($data['text'], "[img=") !== false) || (strpos($data['text'], "[img]") !== false) || DI::config()->get('system', 'always_show_preview')) && !empty($data['image'])) {
			$data['preview'] = $data['image'];
			$data['image'] = '';
		}

		$return = '';
		try {
			if ($tryoembed && OEmbed::isAllowedURL($data['url'])) {
				$return = OEmbed::getHTML($data['url'], $data['title']);
			} else {
				throw new Exception('OEmbed is disabled for this attachment.');
			}
		} catch (Exception $e) {
			$data['title'] = ($data['title'] ?? '') ?: $data['url'];

			if ($simplehtml != self::CONNECTORS) {
				$return = sprintf('<div class="type-%s">', $data['type']);
			}

			if (!empty($data['title']) && !empty($data['url'])) {
				if (!empty($data['image']) && empty($data['text']) && ($data['type'] == 'photo')) {
					$return .= sprintf('<a href="%s" target="_blank" rel="noopener noreferrer"><img src="%s" alt="" title="%s" class="attachment-image" /></a>', $data['url'], self::proxyUrl($data['image'], $simplehtml), $data['title']);
				} else {
					if (!empty($data['image'])) {
						$return .= sprintf('<a href="%s" target="_blank" rel="noopener noreferrer"><img src="%s" alt="" title="%s" class="attachment-image" /></a><br />', $data['url'], self::proxyUrl($data['image'], $simplehtml), $data['title']);
					} elseif (!empty($data['preview'])) {
						$return .= sprintf('<a href="%s" target="_blank" rel="noopener noreferrer"><img src="%s" alt="" title="%s" class="attachment-preview" /></a><br />', $data['url'], self::proxyUrl($data['preview'], $simplehtml), $data['title']);
					}
					$return .= sprintf('<h4><a href="%s">%s</a></h4>', $data['url'], $data['title']);
				}
			}

			if (!empty($data['description']) && $data['description'] != $data['title']) {
				// Sanitize the HTML by converting it to BBCode
				$bbcode = HTML::toBBCode($data['description']);
				$return .= sprintf('<blockquote>%s</blockquote>', trim(self::convert($bbcode)));
			}

			if (!empty($data['url'])) {
				$return .= sprintf('<sup><a href="%s">%s</a></sup>', $data['url'], parse_url($data['url'], PHP_URL_HOST));
			}

			if ($simplehtml != self::CONNECTORS) {
				$return .= '</div>';
			}
		}

		return trim(($data['text'] ?? '') . ' ' . $return . ' ' . ($data['after'] ?? ''));
	}

	public static function removeShareInformation($Text, $plaintext = false, $nolink = false)
	{
		$data = self::getAttachmentData($Text);

		if (!$data) {
			return $Text;
		} elseif ($nolink) {
			return $data['text'] . ($data['after'] ?? '');
		}

		$title = htmlentities($data['title'] ?? '', ENT_QUOTES, 'UTF-8', false);
		$text = htmlentities($data['text'], ENT_QUOTES, 'UTF-8', false);
		if ($plaintext || (($title != '') && strstr($text, $title))) {
			$data['title'] = $data['url'];
		} elseif (($text != '') && strstr($title, $text)) {
			$data['text'] = $data['title'];
			$data['title'] = $data['url'];
		}

		if (empty($data['text']) && !empty($data['title']) && empty($data['url'])) {
			return $data['title'] . $data['after'];
		}

		// If the link already is included in the post, don't add it again
		if (!empty($data['url']) && strpos($data['text'], $data['url'])) {
			return $data['text'] . $data['after'];
		}

		$text = $data['text'];

		if (!empty($data['url']) && !empty($data['title'])) {
			$text .= "\n[url=" . $data['url'] . ']' . $data['title'] . '[/url]';
		} elseif (!empty($data['url'])) {
			$text .= "\n[url]" . $data['url'] . '[/url]';
		}

		return $text . "\n" . $data['after'];
	}

	/**
	 * Converts [url] BBCodes in a format that looks fine on Mastodon. (callback function)
	 *
	 * @param array $match Array with the matching values
	 * @return string reformatted link including HTML codes
	 */
	private static function convertUrlForActivityPubCallback($match)
	{
		$url = $match[1];

		if (isset($match[2]) && ($match[1] != $match[2])) {
			return $match[0];
		}

		$parts = parse_url($url);
		if (!isset($parts['scheme'])) {
			return $match[0];
		}

		return self::convertUrlForActivityPub($url);
	}

	/**
	 * Converts [url] BBCodes in a format that looks fine on ActivityPub systems.
	 *
	 * @param string $url URL that is about to be reformatted
	 * @return string reformatted link including HTML codes
	 */
	private static function convertUrlForActivityPub($url)
	{
		$html = '<a href="%s" target="_blank" rel="noopener noreferrer">%s</a>';
		return sprintf($html, $url, self::getStyledURL($url));
	}

	/**
	 * Converts an URL in a nicer format (without the scheme and possibly shortened)
	 *
	 * @param string $url URL that is about to be reformatted
	 * @return string reformatted link
	 */
	private static function getStyledURL($url)