<?php
/**
 * @copyright Copyright (C) 2010-2024, 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\Protocol;

use DOMDocument;
use DOMElement;
use DOMXPath;
use Friendica\App;
use Friendica\Content\Text\BBCode;
use Friendica\Content\Text\HTML;
use Friendica\Core\Cache\Enum\Duration;
use Friendica\Core\Logger;
use Friendica\Core\Protocol;
use Friendica\Database\DBA;
use Friendica\DI;
use Friendica\Model\APContact;
use Friendica\Model\Contact;
use Friendica\Model\Conversation;
use Friendica\Model\Item;
use Friendica\Model\ItemURI;
use Friendica\Model\Post;
use Friendica\Model\Tag;
use Friendica\Model\User;
use Friendica\Network\HTTPClient\Client\HttpClientAccept;
use Friendica\Network\Probe;
use Friendica\Util\DateTimeFormat;
use Friendica\Util\Images;
use Friendica\Util\Proxy;
use Friendica\Util\Strings;
use Friendica\Util\XML;

/**
 * This class contain functions for the OStatus protocol
 */
class OStatus
{
	private static $itemlist;
	private static $conv_list = [];

	/**
	 * Fetches author data
	 *
	 * @param DOMXPath $xpath     The xpath object
	 * @param object   $context   The xml context of the author details
	 * @param array    $importer  user record of the importing user
	 * @param array    $contact   Called by reference, will contain the fetched contact
	 * @param bool     $onlyfetch Only fetch the header without updating the contact entries
	 *
	 * @return array Array of author related entries for the item
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 * @throws \ImagickException
	 */
	private static function fetchAuthor(DOMXPath $xpath, $context, array $importer, array &$contact = null, bool $onlyfetch): array
	{
		$author = [];
		$author['author-link'] = XML::getFirstNodeValue($xpath, 'atom:author/atom:uri/text()', $context);
		$author['author-name'] = XML::getFirstNodeValue($xpath, 'atom:author/atom:name/text()', $context);
		$addr = XML::getFirstNodeValue($xpath, 'atom:author/atom:email/text()', $context);

		$aliaslink = $author['author-link'];

		$alternate_item = $xpath->query("atom:author/atom:link[@rel='alternate']", $context)->item(0);
		if (is_object($alternate_item)) {
			foreach ($alternate_item->attributes as $attributes) {
				if (($attributes->name == 'href') && ($attributes->textContent != '')) {
					$author['author-link'] = $attributes->textContent;
				}
			}
		}
		$author['author-id'] = Contact::getIdForURL($author['author-link']);

		$author['contact-id'] = ($contact['id'] ?? 0) ?: $author['author-id'];

		$contact = [];

/*
		This here would be better, but we would get problems with contacts from the statusnet addon
		This is kept here as a reminder for the future

		$cid = Contact::getIdForURL($author['author-link'], $importer['uid']);
		if ($cid) {
			$contact = DBA::selectFirst('contact', [], ['id' => $cid]);
		}
*/
		if ($aliaslink != '') {
			$contact = DBA::selectFirst('contact', [], [
				"`uid` = ? AND `alias` = ? AND `rel` IN (?, ?)",
				$importer['uid'],
				$aliaslink,
				Contact::SHARING, Contact::FRIEND,
			]);
		}

		if (!DBA::isResult($contact) && $author['author-link'] != '') {
			if ($aliaslink == '') {
				$aliaslink = $author['author-link'];
			}

			$contact = DBA::selectFirst('contact', [], [
				"`uid` = ? AND `nurl` IN (?, ?) AND `rel` IN (?, ?)",
				$importer['uid'],
				Strings::normaliseLink($author['author-link']),
				Strings::normaliseLink($aliaslink),
				Contact::SHARING,
				Contact::FRIEND,
			]);
		}

		if (!DBA::isResult($contact) && ($addr != '')) {
			$contact = DBA::selectFirst('contact', [], [
				"`uid` = ? AND `addr` = ? AND `rel` IN (?, ?)",
				$importer['uid'],
				$addr,
				Contact::SHARING,
				Contact::FRIEND,
			]);
		}

		if (DBA::isResult($contact)) {
			if ($contact['blocked']) {
				$contact['id'] = -1;
			} elseif (!empty(APContact::getByURL($contact['url'], false))) {
				ActivityPub\Receiver::switchContact($contact['id'], $importer['uid'], $contact['url']);
			}
			$author['contact-id'] = $contact['id'];
		}

		$avatarlist = [];
		$avatars = $xpath->query("atom:author/atom:link[@rel='avatar']", $context);
		foreach ($avatars as $avatar) {
			$href = '';
			$width = 0;
			foreach ($avatar->attributes as $attributes) {
				if ($attributes->name == 'href') {
					$href = $attributes->textContent;
				}
				if ($attributes->name == 'width') {
					$width = $attributes->textContent;
				}
			}
			if ($href != '') {
				$avatarlist[$width] = $href;
			}
		}
		if (count($avatarlist) > 0) {
			krsort($avatarlist);
			$author['author-avatar'] = Probe::fixAvatar(current($avatarlist), $author['author-link']);
		}

		$displayname = XML::getFirstNodeValue($xpath, 'atom:author/poco:displayName/text()', $context);
		if ($displayname != '') {
			$author['author-name'] = $displayname;
		}

		$author['owner-id'] = $author['author-id'];

		// Only update the contacts if it is an OStatus contact
		if (DBA::isResult($contact) && ($contact['id'] > 0) && !$onlyfetch && ($contact['network'] == Protocol::OSTATUS)) {

			// Update contact data
			$current = $contact;
			unset($current['name-date']);

			// This query doesn't seem to work
			// $value = $xpath->query("atom:link[@rel='salmon']", $context)->item(0)->nodeValue;
			// if ($value != "")
			//	$contact["notify"] = $value;

			// This query doesn't seem to work as well - I hate these queries
			// $value = $xpath->query("atom:link[@rel='self' and @type='application/atom+xml']", $context)->item(0)->nodeValue;
			// if ($value != "")
			//	$contact["poll"] = $value;

			$contact['url'] = $author['author-link'];
			$contact['nurl'] = Strings::normaliseLink($contact['url']);

			$value = XML::getFirstNodeValue($xpath, 'atom:author/atom:uri/text()', $context);
			if ($value != '') {
				$contact['alias'] = $value;
			}

			$value = XML::getFirstNodeValue($xpath, 'atom:author/poco:displayName/text()', $context);
			if ($value != '') {
				$contact['name'] = $value;
			}

			$value = XML::getFirstNodeValue($xpath, 'atom:author/poco:preferredUsername/text()', $context);
			if ($value != '') {
				$contact['nick'] = $value;
			}

			$value = XML::getFirstNodeValue($xpath, 'atom:author/poco:note/text()', $context);
			if ($value != '') {
				$contact['about'] = HTML::toBBCode($value);
			}

			$value = XML::getFirstNodeValue($xpath, 'atom:author/poco:address/poco:formatted/text()', $context);
			if ($value != '') {
				$contact['location'] = $value;
			}

			$contact['name-date'] = DateTimeFormat::utcNow();

			Contact::update($contact, ['id' => $contact['id']], $current);

			if (!empty($author['author-avatar']) && ($author['author-avatar'] != $current['avatar'])) {
				Logger::info('Update profile picture for contact ' . $contact['id']);
				Contact::updateAvatar($contact['id'], $author['author-avatar']);
			}

			// Ensure that we are having this contact (with uid=0)
			$cid = Contact::getIdForURL($aliaslink);

			if ($cid) {
				$fields = ['url', 'nurl', 'name', 'nick', 'alias', 'about', 'location'];
				$old_contact = DBA::selectFirst('contact', $fields, ['id' => $cid]);

				// Update it with the current values
				$fields = [
					'url' => $author['author-link'],
					'name' => $contact['name'],
					'nurl' => Strings::normaliseLink($author['author-link']),
					'nick' => $contact['nick'],
					'alias' => $contact['alias'],
					'about' => $contact['about'],
					'location' => $contact['location'],
					'success_update' => DateTimeFormat::utcNow(),
					'last-update' => DateTimeFormat::utcNow(),
				];

				Contact::update($fields, ['id' => $cid], $old_contact);

				// Update the avatar
				if (!empty($author['author-avatar'])) {
					Contact::updateAvatar($cid, $author['author-avatar']);
				}
			}
		} elseif (empty($contact['network']) || ($contact['network'] != Protocol::DFRN)) {
			$contact = [];
		}

		return $author;
	}

	/**
	 * Fetches author data from a given XML string
	 *
	 * @param string $xml      The XML
	 * @param array  $importer user record of the importing user
	 *
	 * @return array Array of author related entries for the item
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 * @throws \ImagickException
	 */
	public static function salmonAuthor(string $xml, array $importer): array
	{
		if (empty($xml)) {
			return [];
		}

		$doc = new DOMDocument();
		@$doc->loadXML($xml);

		$xpath = new DOMXPath($doc);
		$xpath->registerNamespace('atom', ActivityNamespace::ATOM1);
		$xpath->registerNamespace('thr', ActivityNamespace::THREAD);
		$xpath->registerNamespace('georss', ActivityNamespace::GEORSS);
		$xpath->registerNamespace('activity', ActivityNamespace::ACTIVITY);
		$xpath->registerNamespace('media', ActivityNamespace::MEDIA);
		$xpath->registerNamespace('poco', ActivityNamespace::POCO);
		$xpath->registerNamespace('ostatus', ActivityNamespace::OSTATUS);
		$xpath->registerNamespace('statusnet', ActivityNamespace::STATUSNET);

		$contact = ['id' => 0];

		// Fetch the first author
		$authordata = $xpath->query('//author')->item(0);
		$author = self::fetchAuthor($xpath, $authordata, $importer, $contact, true);
		return $author;
	}

	/**
	 * Read attributes from element
	 *
	 * @param object $element Element object
	 * @return array attributes
	 */
	private static function readAttributes($element): array
	{
		$attribute = [];

		foreach ($element->attributes as $attributes) {
			$attribute[$attributes->name] = $attributes->textContent;
		}

		return $attribute;
	}

	/**
	 * Imports an XML string containing OStatus elements
	 *
	 * @param string $xml      The XML
	 * @param array  $importer user record of the importing user
	 * @param array  $contact  contact
	 * @param string $hub      Called by reference, returns the fetched hub data
	 * @return void
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 * @throws \ImagickException
	 */
	public static function import($xml, array $importer, array &$contact, &$hub)
	{
		self::process($xml, $importer, $contact, $hub, false, true, Conversation::PUSH);
	}

	/**
	 * Internal feed processing
	 *
	 * @param string  $xml        The XML
	 * @param array   $importer   user record of the importing user
	 * @param array   $contact    contact
	 * @param string  $hub        Called by reference, returns the fetched hub data
	 * @param boolean $stored     Is the post fresh imported or from the database?
	 * @param boolean $initialize Is it the leading post so that data has to be initialized?
	 * @param integer $direction  Direction, default UNKNOWN(0)
	 * @return boolean Could the XML be processed?
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 * @throws \ImagickException
	 */
	private static function process(string $xml, array $importer, array &$contact = null, string &$hub, bool $stored = false, bool $initialize = true, int $direction = Conversation::UNKNOWN)
	{
		if ($initialize) {
			self::$itemlist = [];
			self::$conv_list = [];
		}

		Logger::info('Import OStatus message for user ' . $importer['uid']);

		if (empty($xml)) {
			return false;
		}

		$doc = new DOMDocument();
		@$doc->loadXML($xml);

		$xpath = new DOMXPath($doc);
		$xpath->registerNamespace('atom', ActivityNamespace::ATOM1);
		$xpath->registerNamespace('thr', ActivityNamespace::THREAD);
		$xpath->registerNamespace('georss', ActivityNamespace::GEORSS);
		$xpath->registerNamespace('activity', ActivityNamespace::ACTIVITY);
		$xpath->registerNamespace('media', ActivityNamespace::MEDIA);
		$xpath->registerNamespace('poco', ActivityNamespace::POCO);
		$xpath->registerNamespace('ostatus', ActivityNamespace::OSTATUS);
		$xpath->registerNamespace('statusnet', ActivityNamespace::STATUSNET);

		$hub = '';
		$hub_items = $xpath->query("/atom:feed/atom:link[@rel='hub']")->item(0);
		if (is_object($hub_items)) {
			$hub_attributes = $hub_items->attributes;
			if (is_object($hub_attributes)) {
				foreach ($hub_attributes as $hub_attribute) {
					if ($hub_attribute->name == 'href') {
						$hub = $hub_attribute->textContent;
						Logger::info('Found hub ', ['hub' => $hub]);
					}
				}
			}
		}

		// Initial header elements
		$header = [
			'uid'     => $importer['uid'],
			'network' => Protocol::OSTATUS,
			'wall'    => 0,
			'origin'  => 0,
			'gravity' => Item::GRAVITY_COMMENT,
		];

		if (!is_object($doc->firstChild) || empty($doc->firstChild->tagName)) {
			return false;
		}

		$first_child = $doc->firstChild->tagName;

		if ($first_child == 'feed') {
			$entries = $xpath->query('/atom:feed/atom:entry');
		} else {
			$entries = $xpath->query('/atom:entry');
		}

		if ($entries->length == 1) {
			// We reformat the XML to make it better readable
			$doc2 = new DOMDocument();
			$doc2->loadXML($xml);
			$doc2->preserveWhiteSpace = false;
			$doc2->formatOutput = true;
			$xml2 = $doc2->saveXML();

			$header['protocol'] = Conversation::PARCEL_SALMON;
			$header['source'] = $xml2;
			$header['direction'] = $direction;
		} elseif (!$initialize) {
			return false;
		}

		// Fetch the first author
		$authordata = $xpath->query('//author')->item(0);
		$author = self::fetchAuthor($xpath, $authordata, $importer, $contact, $stored);

		// Reverse the order of the entries
		$entrylist = [];

		foreach ($entries as $entry) {
			$entrylist[] = $entry;
		}

		foreach (array_reverse($entrylist) as $entry) {
			// fetch the author
			$authorelement = $xpath->query('/atom:entry/atom:author', $entry);

			if ($authorelement->length == 0) {
				$authorelement = $xpath->query('atom:author', $entry);
			}

			if ($authorelement->length > 0) {
				$author = self::fetchAuthor($xpath, $entry, $importer, $contact, $stored);
			}

			$item = array_merge($header, $author);

			$item['uri'] = XML::getFirstNodeValue($xpath, 'atom:id/text()', $entry);
			$item['uri-id'] = ItemURI::insert(['uri' => $item['uri']]);

			$item['verb'] = XML::getFirstNodeValue($xpath, 'activity:verb/text()', $entry);

			// Delete a message
			if (in_array($item['verb'], ['qvitter-delete-notice', Activity::DELETE, 'delete'])) {
				self::deleteNotice($item);
				continue;
			}

			if (in_array($item['verb'], [Activity::O_UNFAVOURITE, Activity::UNFAVORITE])) {
				// Ignore "Unfavorite" message
				Logger::info('Ignore unfavorite message ', ['item' => $item]);
				continue;
			}

			// Deletions come with the same uri, so we check for duplicates after processing deletions
			if (Post::exists(['uid' => $importer['uid'], 'uri' => $item['uri']])) {
				Logger::info('Post with URI ' . $item['uri'] . ' already existed for user ' . $importer['uid'] . '.');
				continue;
			} else {
				Logger::info('Processing post with URI ' .  $item['uri'] . ' for user ' . $importer['uid'] . '.');
			}

			if ($item['verb'] == Activity::JOIN) {
				// ignore "Join" messages
				Logger::info('Ignore join message ', ['item' => $item]);
				continue;
			}

			if ($item['verb'] == 'http://mastodon.social/schema/1.0/block') {
				// ignore mastodon "block" messages
				Logger::info('Ignore block message ', ['item' => $item]);
				continue;
			}

			if ($item['verb'] == Activity::FOLLOW) {
				Contact::addRelationship($importer, $contact, $item);
				continue;
			}

			if ($item['verb'] == Activity::O_UNFOLLOW) {
				$dummy = null;
				Contact::removeFollower($contact);
				continue;
			}

			if ($item['verb'] == Activity::FAVORITE) {
				$orig_uri = $xpath->query('activity:object/atom:id', $entry)->item(0)->nodeValue;
				Logger::notice('Favorite', ['uri' => $orig_uri, 'item' => $item]);

				$item['body'] = $item['verb'] = Activity::LIKE;
				$item['thr-parent'] = $orig_uri;
				$item['gravity'] = Item::GRAVITY_ACTIVITY;
				$item['object-type'] = Activity\ObjectType::NOTE;
			}

			// http://activitystrea.ms/schema/1.0/rsvp-yes
			if (!in_array($item['verb'], [Activity::POST, Activity::LIKE, Activity::SHARE])) {
				Logger::info('Unhandled verb', ['verb' => $item['verb'], 'item' => $item]);
			}

			self::processPost($xpath, $entry, $item, $importer);

			if ($initialize && (count(self::$itemlist) > 0)) {
				if (self::$itemlist[0]['uri'] == self::$itemlist[0]['thr-parent']) {
					$uid = self::$itemlist[0]['uid'];
					// We will import it everytime, when it is started by our contacts
					$valid = Contact::isSharingByURL(self::$itemlist[0]['author-link'], $uid);

					if (!$valid) {
						// If not, then it depends on this setting
						$valid = !$uid || DI::pConfig()->get($uid, 'system', 'accept_only_sharer') != Item::COMPLETION_NONE;

						if ($valid) {
							Logger::info('Item with URI ' . self::$itemlist[0]['uri'] . ' will be imported due to the system settings.');
						}
					} else {
						Logger::info('Item with URI ' . self::$itemlist[0]['uri'] . ' belongs to a contact (' . self::$itemlist[0]['contact-id'] . '). It will be imported.');
					}

					if ($valid && DI::pConfig()->get($uid, 'system', 'accept_only_sharer') != Item::COMPLETION_LIKE) {
						// Never post a thread when the only interaction by our contact was a like
						$valid = false;
						$verbs = [Activity::POST, Activity::SHARE];
						foreach (self::$itemlist as $item) {
							if (in_array($item['verb'], $verbs) && Contact::isSharingByURL($item['author-link'], $item['uid'])) {
								$valid = true;
							}
						}
						if ($valid) {
							Logger::info('Item with URI ' . self::$itemlist[0]['uri'] . ' will be imported since the thread contains posts or shares.');
						}
					}
				} else {
					$valid = true;
				}

				if ($valid) {
					$default_contact = 0;
					for ($key = count(self::$itemlist) - 1; $key >= 0; $key--) {
						if (empty(self::$itemlist[$key]['contact-id'])) {
							self::$itemlist[$key]['contact-id'] = $default_contact;
						} else {
							$default_contact = $item['contact-id'];
						}
					}
					foreach (self::$itemlist as $item) {
						$found = Post::exists(['uid' => $importer['uid'], 'uri' => $item['uri']]);
						if ($found) {
							Logger::notice('Item with URI ' . $item['uri'] . ' for user ' . $importer['uid'] . ' already exists.');
						} elseif ($item['contact-id'] < 0) {
							Logger::notice('Item with URI ' . $item['uri'] . ' is from a blocked contact.');
						} else {
							$ret = Item::insert($item);
							Logger::info('Item with URI ' . $item['uri'] . ' for user ' . $importer['uid'] . ' stored. Return value: ' . $ret);
						}
					}
				}
				self::$itemlist = [];
			}
			Logger::info('Processing done for post with URI ' . $item['uri'] . ' for user '.$importer['uid'] . '.');
		}
		return true;
	}

	/**
	 * Removes notice item from database
	 *
	 * @param array $item item
	 * @return void
	 * @throws \Exception
	 */
	private static function deleteNotice(array $item)
	{
		$condition = ['uid' => $item['uid'], 'author-id' => $item['author-id'], 'uri' => $item['uri']];
		if (!Post::exists($condition)) {
			Logger::notice('Item from ' . $item['author-link'] . ' with uri ' . $item['uri'] . ' for user ' . $item['uid'] . " wasn't found. We don't delete it.");
			return;
		}

		Item::markForDeletion($condition);

		Logger::notice('Deleted item with URI ' . $item['uri'] . ' for user ' . $item['uid']);
	}

	/**
	 * Processes the XML for a post
	 *
	 * @param DOMXPath $xpath    The xpath object
	 * @param object   $entry    The xml entry that is processed
	 * @param array    $item     The item array
	 * @param array    $importer user record of the importing user
	 * @return void
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 * @throws \ImagickException
	 */
	private static function processPost(DOMXPath $xpath, $entry, array &$item, array $importer)
	{
		$item['body'] = HTML::toBBCode(XML::getFirstNodeValue($xpath, 'atom:content/text()', $entry));
		$item['object-type'] = XML::getFirstNodeValue($xpath, 'activity:object-type/text()', $entry);
		if (($item['object-type'] == Activity\ObjectType::BOOKMARK) || ($item['object-type'] == Activity\ObjectType::EVENT)) {
			$item['title'] = XML::getFirstNodeValue($xpath, 'atom:title/text()', $entry);
			$item['body'] = XML::getFirstNodeValue($xpath, 'atom:summary/text()', $entry);
		} elseif ($item['object-type'] == Activity\ObjectType::QUESTION) {
			$item['title'] = XML::getFirstNodeValue($xpath, 'atom:title/text()', $entry);
		}

		$item['created'] = XML::getFirstNodeValue($xpath, 'atom:published/text()', $entry);
		$item['edited'] = XML::getFirstNodeValue($xpath, 'atom:updated/text()', $entry);
		$item['conversation'] = XML::getFirstNodeValue($xpath, 'ostatus:conversation/text()', $entry);

		$conv = $xpath->query('ostatus:conversation', $entry);
		if (is_object($conv->item(0))) {
			foreach ($conv->item(0)->attributes as $attributes) {
				if ($attributes->name == 'ref') {
					$item['conversation'] = $attributes->textContent;
				}
				if ($attributes->name == 'href') {
					$item['conversation'] = $attributes->textContent;
				}
			}
		}

		$related = '';

		$inreplyto = $xpath->query('thr:in-reply-to', $entry);
		if (is_object($inreplyto->item(0))) {
			foreach ($inreplyto->item(0)->attributes as $attributes) {
				if ($attributes->name == 'ref') {
					$item['thr-parent'] = $attributes->textContent;
				}
				if ($attributes->name == 'href') {
					$related = $attributes->textContent;
				}
			}
		}

		$georsspoint = $xpath->query('georss:point', $entry);
		if (!empty($georsspoint) && ($georsspoint->length > 0)) {
			$item['coord'] = $georsspoint->item(0)->nodeValue;
		}

		$categories = $xpath->query('atom:category', $entry);
		if ($categories) {
			foreach ($categories as $category) {
				foreach ($category->attributes as $attributes) {
					if ($attributes->name == 'term') {
						// Store the hashtag
						Tag::store($item['uri-id'], Tag::HASHTAG, $attributes->textContent);
					}
				}
			}
		}

		$self = '';
		$add_body = '';

		$links = $xpath->query('atom:link', $entry);
		if ($links) {
			$link_data = self::processLinks($links, $item);
			$self = $link_data['self'];
			$add_body = $link_data['add_body'];
		}

		$repeat_of = '';

		$notice_info = $xpath->query('statusnet:notice_info', $entry);
		if ($notice_info && ($notice_info->length > 0)) {
			foreach ($notice_info->item(0)->attributes as $attributes) {
				if ($attributes->name == 'source') {
					$item['app'] = strip_tags($attributes->textContent);
				}
				if ($attributes->name == 'repeat_of') {
					$repeat_of = $attributes->textContent;
				}
			}
		}
		// Is it a repeated post?
		if (($repeat_of != '') || ($item['verb'] == Activity::SHARE)) {
			$link_data = self::processRepeatedItem($xpath, $entry, $item, $importer);
			if (!empty($link_data['add_body'])) {
				$add_body .= $link_data['add_body'];
			}
		}

		$item['body'] .= $add_body;

		Tag::storeFromBody($item['uri-id'], $item['body']);

		// Mastodon Content Warning
		if (($item['verb'] == Activity::POST) && $xpath->evaluate('boolean(atom:summary)', $entry)) {
			$clear_text = XML::getFirstNodeValue($xpath, 'atom:summary/text()', $entry);
			if (!empty($clear_text)) {
				$item['content-warning'] = HTML::toBBCode($clear_text);
			}
		}

		if (isset($item['thr-parent'])) {
			if (!Post::exists(['uid' => $importer['uid'], 'uri' => $item['thr-parent']])) {
				if ($related != '') {
					self::fetchRelated($related, $item['thr-parent'], $importer);
				}
			} else {
				Logger::info('Reply with URI ' . $item['uri'] . ' already existed for user ' . $importer['uid'] . '.');
			}
		} else {
			$item['thr-parent'] = $item['uri'];
			$item['gravity'] = Item::GRAVITY_PARENT;
		}

		self::$itemlist[] = $item;
	}

	/**
	 * Fetch related posts and processes them
	 *
	 * @param string $related     The link to the related item
	 * @param string $related_uri The related item in "uri" format
	 * @param array  $importer    user record of the importing user
	 * @return void
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 * @throws \ImagickException
	 */
	private static function fetchRelated(string $related, string $related_uri, array $importer)
	{
		$stored = false;
		$curlResult = DI::httpClient()->get($related, HttpClientAccept::ATOM_XML);

		if (!$curlResult->isSuccess() || empty($curlResult->getBodyString())) {
			return;
		}

		$xml = '';

		if ($curlResult->inHeader('Content-Type') &&
			in_array('application/atom+xml', $curlResult->getHeader('Content-Type'))) {
			Logger::info('Directly fetched XML for URI ' . $related_uri);
			$xml = $curlResult->getBodyString();
		}

		if ($xml == '') {
			$doc = new DOMDocument();
			if (!@$doc->loadHTML($curlResult->getBodyString())) {
				return;
			}
			$xpath = new DOMXPath($doc);

			$atom_file = '';

			$links = $xpath->query('//link');
			if ($links) {
				foreach ($links as $link) {
					$attribute = self::readAttributes($link);
					if (($attribute['rel'] == 'alternate') && ($attribute['type'] == 'application/atom+xml')) {
						$atom_file = $attribute['href'];
					}
				}
				if ($atom_file != '') {
					$curlResult = DI::httpClient()->get($atom_file, HttpClientAccept::ATOM_XML);

					if ($curlResult->isSuccess()) {
						Logger::info('Fetched XML for URI ' . $related_uri);
						$xml = $curlResult->getBodyString();
					}
				}
			}
		}

		// Workaround for older GNU Social servers
		if (($xml == '') && strstr($related, '/notice/')) {
			$curlResult = DI::httpClient()->get(str_replace('/notice/', '/api/statuses/show/', $related) . '.atom', HttpClientAccept::ATOM_XML);

			if ($curlResult->isSuccess()) {
				Logger::info('GNU Social workaround to fetch XML for URI ' . $related_uri);
				$xml = $curlResult->getBodyString();
			}
		}

		// Even more worse workaround for GNU Social ;-)
		if ($xml == '') {
			$related_guess = self::convertHref($related_uri);
			$curlResult = DI::httpClient()->get(str_replace('/notice/', '/api/statuses/show/', $related_guess) . '.atom', HttpClientAccept::ATOM_XML);

			if ($curlResult->isSuccess()) {
				Logger::info('GNU Social workaround 2 to fetch XML for URI ' . $related_uri);
				$xml = $curlResult->getBodyString();
			}
		}

		if ($xml != '') {
			$hub = '';
			self::process($xml, $importer, $contact, $hub, $stored, false, Conversation::PULL);
		} else {
			Logger::info('XML could not be fetched for URI: ' . $related_uri . ' - href: ' . $related);
		}
		return;
	}

	/**
	 * Processes the XML for a repeated post
	 *
	 * @param DOMXPath $xpath    The xpath object
	 * @param object   $entry    The xml entry that is processed
	 * @param array    $item     The item array
	 * @param array    $importer user record of the importing user
	 *
	 * @return array with data from links
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 * @throws \ImagickException
	 */
	private static function processRepeatedItem(DOMXPath $xpath, $entry, array &$item, array $importer): array
	{
		$activityobject = $xpath->query('activity:object', $entry)->item(0);

		if (!is_object($activityobject)) {
			return [];
		}

		$link_data = [];

		$orig_uri = XML::getFirstNodeValue($xpath, 'atom:id/text()', $activityobject);

		$links = $xpath->query('atom:link', $activityobject);
		if ($links) {
			$link_data = self::processLinks($links, $item);
		}

		$orig_body = XML::getFirstNodeValue($xpath, 'atom:content/text()', $activityobject);
		$orig_created = XML::getFirstNodeValue($xpath, 'atom:published/text()', $activityobject);
		$orig_edited = XML::getFirstNodeValue($xpath, 'atom:updated/text()', $activityobject);

		$orig_author = self::fetchAuthor($xpath, $activityobject, $importer, $dummy, false);

		$item['author-name'] = $orig_author['author-name'];
		$item['author-link'] = $orig_author['author-link'];
		$item['author-id'] = $orig_author['author-id'];

		$item['body'] = HTML::toBBCode($orig_body);
		$item['created'] = $orig_created;
		$item['edited'] = $orig_edited;

		$item['uri'] = $orig_uri;

		$item['verb'] = XML::getFirstNodeValue($xpath, 'activity:verb/text()', $activityobject);

		$item['object-type'] = XML::getFirstNodeValue($xpath, 'activity:object-type/text()', $activityobject);

		// Mastodon Content Warning
		if (($item['verb'] == Activity::POST) && $xpath->evaluate('boolean(atom:summary)', $activityobject)) {
			$clear_text = XML::getFirstNodeValue($xpath, 'atom:summary/text()', $activityobject);
			if (!empty($clear_text)) {
				$item['content-warning'] = HTML::toBBCode($clear_text);
			}
		}

		$inreplyto = $xpath->query('thr:in-reply-to', $activityobject);
		if (is_object($inreplyto->item(0))) {
			foreach ($inreplyto->item(0)->attributes as $attributes) {
				if ($attributes->name == 'ref') {
					$item['thr-parent'] = $attributes->textContent;
				}
			}
		}

		return $link_data;
	}

	/**
	 * Processes links in the XML
	 *
	 * @param object $links The xml data that contain links
	 * @param array  $item  The item array
	 * @return array with data from the links
	 */
	private static function processLinks($links, array &$item): array
	{
		$link_data = ['add_body' => '', 'self' => ''];

		foreach ($links as $link) {
			$attribute = self::readAttributes($link);

			if (!empty($attribute['rel']) && !empty($attribute['href'])) {
				switch ($attribute['rel']) {
					case 'alternate':
						$item['plink'] = $attribute['href'];
						if (($item['object-type'] == Activity\ObjectType::QUESTION)
							|| ($item['object-type'] == Activity\ObjectType::EVENT)
						) {
							Post\Media::insert(['uri-id' => $item['uri-id'], 'type' => Post\Media::UNKNOWN,
								'url' => $attribute['href'], 'mimetype' => $attribute['type'] ?? null,
								'size' => $attribute['length'] ?? null, 'description' => $attribute['title'] ?? null]);
						}
						break;

					case 'ostatus:conversation':
						$link_data['conversation'] = $attribute['href'];
						$item['conversation'] = $link_data['conversation'];
						break;

					case 'enclosure':
						$filetype = strtolower(substr($attribute['type'], 0, strpos($attribute['type'], '/')));
						if ($filetype == 'image') {
							$link_data['add_body'] .= "\n[img]".$attribute['href'].'[/img]';
						} else {
							Post\Media::insert(['uri-id' => $item['uri-id'], 'type' => Post\Media::DOCUMENT,
								'url' => $attribute['href'], 'mimetype' => $attribute['type'],
								'size' => $attribute['length'] ?? null, 'description' => $attribute['title'] ?? null]);
						}
						break;

					case 'related':
						if ($item['object-type'] != Activity\ObjectType::BOOKMARK) {
							if (!isset($item['thr-parent'])) {
								$item['thr-parent'] = $attribute['href'];
							}
							$link_data['related'] = $attribute['href'];
						} else {
							Post\Media::insert(['uri-id' => $item['uri-id'], 'type' => Post\Media::UNKNOWN,
								'url' => $attribute['href'], 'mimetype' => $attribute['type'] ?? null,
								'size' => $attribute['length'] ?? null, 'description' => $attribute['title'] ?? null]);
						}
						break;

					case 'self':
						if (empty($item['plink'])) {
							$item['plink'] = $attribute['href'];
						}
						$link_data['self'] = $attribute['href'];
						break;

					default:
						Logger::notice('Unsupported rel=' . $attribute['rel'] . ', href=' . $attribute['href'] . ', object-type=' . $item['object-type']);
				}
			}
		}
		return $link_data;
	}

	/**
	 * Create an url out of an uri
	 *
	 * @param string $href URI in the format "parameter1:parameter1:..."
	 * @return string URL in the format http(s)://....
	 */
	private static function convertHref(string $href): string
	{
		$elements = explode(':', $href);

		if ((count($elements) <= 2) || ($elements[0] != 'tag')) {
			return $href;
		}

		$server = explode(',', $elements[1]);
		$conversation = explode('=', $elements[2]);

		if ((count($elements) == 4) && ($elements[2] == 'post')) {
			return 'http://' . $server[0] . '/notice/' . $elements[3];
		}

		if ((count($conversation) != 2) || ($conversation[1] == '')) {
			return $href;
		}

		if ($elements[3] == 'objectType=thread') {
			return 'http://' . $server[0] . '/conversation/' . $conversation[1];
		} else {
			return 'http://' . $server[0] . '/notice/' . $conversation[1];
		}
	}

	/**
	 * Adds the header elements to the XML document
	 *
	 * @param DOMDocument $doc       XML document
	 * @param array       $owner     Contact data of the poster
	 * @param string      $filter    The related feed filter (activity, posts or comments)
	 *
	 * @return DOMElement Header root element
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 */
	private static function addHeader(DOMDocument $doc, array $owner, string $filter): DOMElement
	{
		$root = $doc->createElementNS(ActivityNamespace::ATOM1, 'feed');
		$doc->appendChild($root);

		$root->setAttribute('xmlns:thr', ActivityNamespace::THREAD);
		$root->setAttribute('xmlns:georss', ActivityNamespace::GEORSS);
		$root->setAttribute('xmlns:activity', ActivityNamespace::ACTIVITY);
		$root->setAttribute('xmlns:media', ActivityNamespace::MEDIA);
		$root->setAttribute('xmlns:poco', ActivityNamespace::POCO);
		$root->setAttribute('xmlns:ostatus', ActivityNamespace::OSTATUS);
		$root->setAttribute('xmlns:statusnet', ActivityNamespace::STATUSNET);
		$root->setAttribute('xmlns:mastodon', ActivityNamespace::MASTODON);

		$title = '';
		$selfUri = '/feed/' . $owner['nick'] . '/';
		switch ($filter) {
			case 'activity':
				$title = DI::l10n()->t('%s\'s timeline', $owner['name']);
				$selfUri .= $filter;
				break;

			case 'posts':
				$title = DI::l10n()->t('%s\'s posts', $owner['name']);
				break;

			case 'comments':
				$title = DI::l10n()->t('%s\'s comments', $owner['name']);
				$selfUri .= $filter;
				break;
		}

		$selfUri = '/dfrn_poll/' . $owner['nick'];

		$attributes = [
			'uri' => 'https://friendi.ca',
			'version' => App::VERSION . '-' . DB_UPDATE_VERSION,
		];
		XML::addElement($doc, $root, 'generator', App::PLATFORM, $attributes);
		XML::addElement($doc, $root, 'id', DI::baseUrl() . '/profile/' . $owner['nick']);
		XML::addElement($doc, $root, 'title', $title);
		XML::addElement($doc, $root, 'subtitle', sprintf("Updates from %s on %s", $owner['name'], DI::config()->get('config', 'sitename')));
		XML::addElement($doc, $root, 'logo', User::getAvatarUrl($owner, Proxy::SIZE_SMALL));
		XML::addElement($doc, $root, 'updated', DateTimeFormat::utcNow(DateTimeFormat::ATOM));

		$author = self::addAuthor($doc, $owner, true);
		$root->appendChild($author);

		$attributes = [
			'href' => $owner['url'],
			'rel' => 'alternate',
			'type' => 'text/html',
		];
		XML::addElement($doc, $root, 'link', '', $attributes);

		/// @TODO We have to find out what this is
		/// $attributes = array("href" => DI::baseUrl()."/sup",
		///		"rel" => "http://api.friendfeed.com/2008/03#sup",
		///		"type" => "application/json");
		/// XML::addElement($doc, $root, "link", "", $attributes);

		self::addHubLink($doc, $root, $owner['nick']);

		$attributes = ['href' => DI::baseUrl() . '/salmon/' . $owner['nick'], 'rel' => 'salmon'];
		XML::addElement($doc, $root, 'link', '', $attributes);

		$attributes = ['href' => DI::baseUrl() . '/salmon/' . $owner['nick'], 'rel' => 'http://salmon-protocol.org/ns/salmon-replies'];
		XML::addElement($doc, $root, 'link', '', $attributes);

		$attributes = ['href' => DI::baseUrl() . '/salmon/' . $owner['nick'], 'rel' => 'http://salmon-protocol.org/ns/salmon-mention'];
		XML::addElement($doc, $root, 'link', '', $attributes);

		$attributes = ['href' => DI::baseUrl() . $selfUri, 'rel' => 'self', 'type' => 'application/atom+xml'];
		XML::addElement($doc, $root, 'link', '', $attributes);

		if ($owner['contact-type'] == Contact::TYPE_COMMUNITY) {
			$members = DBA::count('contact', [
				'uid'     => $owner['uid'],
				'self'    => false,
				'pending' => false,
				'archive' => false,
				'hidden'  => false,
				'blocked' => false,
			]);
			XML::addElement($doc, $root, 'statusnet:group_info', '', ['member_count' => $members]);
		}

		return $root;
	}

	/**
	 * Add the link to the push hubs to the XML document
	 *
	 * @param DOMDocument $doc  XML document
	 * @param DOMElement  $root XML root element where the hub links are added
	 * @param string      $nick Nickname
	 * @return void
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 */
	public static function addHubLink(DOMDocument $doc, DOMElement $root, string $nick)
	{
		$h = DI::baseUrl() . '/pubsubhubbub/' . $nick;
		XML::addElement($doc, $root, 'link', '', ['href' => $h, 'rel' => 'hub']);
	}

	/**
	 * Adds attachment data to the XML document
	 *
	 * @param DOMDocument $doc  XML document
	 * @param DOMElement  $root XML root element where the hub links are added
	 * @param array       $item Data of the item that is to be posted
	 * @return void
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 */
	public static function getAttachment(DOMDocument $doc, DOMElement $root, array $item)
	{
		foreach (Post\Media::getByURIId($item['uri-id'], [Post\Media::AUDIO, Post\Media::IMAGE, Post\Media::VIDEO, Post\Media::DOCUMENT, Post\Media::TORRENT]) as $attachment) {
			$attributes = ['rel' => 'enclosure',
				'href' => $attachment['url'],
				'type' => $attachment['mimetype']];

			if (!empty($attachment['size'])) {
				$attributes['length'] = intval($attachment['size']);
			}
			if (!empty($attachment['description'])) {
				$attributes['title'] = $attachment['description'];
			}

			XML::addElement($doc, $root, 'link', '', $attributes);
		}
	}

	/**
	 * Adds the author element to the XML document
	 *
	 * @param DOMDocument $doc          XML document
	 * @param array       $owner        Contact data of the poster
	 * @param bool        $show_profile Whether to show profile
	 * @return DOMElement Author element
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 */
	private static function addAuthor(DOMDocument $doc, array $owner, bool $show_profile = true): DOMElement
	{
		$profile = DBA::selectFirst('profile', ['homepage', 'publish'], ['uid' => $owner['uid']]);
		$author = $doc->createElement('author');
		XML::addElement($doc, $author, 'id', $owner['url']);
		if ($owner['contact-type'] == Contact::TYPE_COMMUNITY) {
			XML::addElement($doc, $author, 'activity:object-type', Activity\ObjectType::GROUP);
		} else {
			XML::addElement($doc, $author, 'activity:object-type', Activity\ObjectType::PERSON);
		}

		XML::addElement($doc, $author, 'uri', $owner['url']);
		XML::addElement($doc, $author, 'name', $owner['nick']);
		XML::addElement($doc, $author, 'email', $owner['addr']);
		if ($show_profile) {
			XML::addElement($doc, $author, 'summary', BBCode::convertForUriId($owner['uri-id'], $owner['about'], BBCode::OSTATUS));
		}

		$attributes = [
			'rel' => 'alternate',
			'type' => 'text/html',
			'href' => $owner['url'],
		];
		XML::addElement($doc, $author, 'link', '', $attributes);

		$attributes = [
			'rel' => 'avatar',
			'type' => 'image/jpeg', // To-Do?
			'media:width' => Proxy::PIXEL_SMALL,
			'media:height' => Proxy::PIXEL_SMALL,
			'href' => User::getAvatarUrl($owner, Proxy::SIZE_SMALL),
		];
		XML::addElement($doc, $author, 'link', '', $attributes);

		if (isset($owner['thumb'])) {
			$attributes = [
				'rel' => 'avatar',
				'type' => 'image/jpeg', // To-Do?
				'media:width' => Proxy::PIXEL_THUMB,
				'media:height' => Proxy::PIXEL_THUMB,
				'href' => User::getAvatarUrl($owner, Proxy::SIZE_THUMB),
			];
			XML::addElement($doc, $author, 'link', '', $attributes);
		}

		XML::addElement($doc, $author, 'poco:preferredUsername', $owner['nick']);
		XML::addElement($doc, $author, 'poco:displayName', $owner['name']);
		if ($show_profile) {
			XML::addElement($doc, $author, 'poco:note', BBCode::convertForUriId($owner['uri-id'], $owner['about'], BBCode::OSTATUS));

			if (trim($owner['location']) != '') {
				$element = $doc->createElement('poco:address');
				XML::addElement($doc, $element, 'poco:formatted', $owner['location']);
				$author->appendChild($element);
			}
		}

		if (DBA::isResult($profile) && !$show_profile) {
			if (trim($profile['homepage']) != '') {
				$urls = $doc->createElement('poco:urls');
				XML::addElement($doc, $urls, 'poco:type', 'homepage');
				XML::addElement($doc, $urls, 'poco:value', $profile['homepage']);
				XML::addElement($doc, $urls, 'poco:primary', 'true');
				$author->appendChild($urls);
			}

			XML::addElement($doc, $author, 'followers', '', ['url' => DI::baseUrl() . '/profile/' . $owner['nick'] . '/contacts/followers']);
			XML::addElement($doc, $author, 'statusnet:profile_info', '', ['local_id' => $owner['uid']]);

			if ($profile['publish']) {
				XML::addElement($doc, $author, 'mastodon:scope', 'public');
			}
		}

		return $author;
	}

	/**
	 * @TODO Picture attachments should look like this:
	 *	<a href="https://status.pirati.ca/attachment/572819" title="https://status.pirati.ca/file/heluecht-20151202T222602-rd3u49p.gif"
	 *	class="attachment thumbnail" id="attachment-572819" rel="nofollow external">https://status.pirati.ca/attachment/572819</a>
	 */

	/**
	 * Returns the given activity if present - otherwise returns the "post" activity
	 *
	 * @param array $item Data of the item that is to be posted
	 * @return string activity
	 */
	public static function constructVerb(array $item): string
	{
		if (!empty($item['verb'])) {
			return $item['verb'];
		}

		return Activity::POST;
	}

	/**
	 * Returns the given object type if present - otherwise returns the "note" object type
	 *
	 * @param array $item Data of the item that is to be posted
	 * @return string Object type
	 */
	private static function constructObjecttype(array $item): string
	{
		if (!empty($item['object-type']) && in_array($item['object-type'], [Activity\ObjectType::NOTE, Activity\ObjectType::COMMENT])) {
			return $item['object-type'];
		}

		return Activity\ObjectType::NOTE;
	}

	/**
	 * Adds an entry element to the XML document
	 *
	 * @param DOMDocument $doc       XML document
	 * @param array       $item      Data of the item that is to be posted
	 * @param array       $owner     Contact data of the poster
	 * @param bool        $toplevel  optional default false
	 *
	 * @return DOMElement Entry element
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 * @throws \ImagickException
	 */
	private static function entry(DOMDocument $doc, array $item, array $owner, bool $toplevel = false): DOMElement
	{
		if ($item['verb'] == Activity::LIKE) {
			return self::likeEntry($doc, $item, $owner, $toplevel);
		} elseif (in_array($item['verb'], [Activity::FOLLOW, Activity::O_UNFOLLOW])) {
			return self::followEntry($doc, $item, $owner, $toplevel);
		} else {
			return self::noteEntry($doc, $item, $owner, $toplevel);
		}
	}

	/**
	 * Adds an entry element with a "like"
	 *
	 * @param DOMDocument $doc      XML document
	 * @param array       $item     Data of the item that is to be posted
	 * @param array       $owner    Contact data of the poster
	 * @param bool        $toplevel Is it for en entry element (false) or a feed entry (true)?
	 * @return DOMElement Entry element with "like"
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 * @throws \ImagickException
	 */
	private static function likeEntry(DOMDocument $doc, array $item, array $owner, bool $toplevel): DOMElement
	{
		if (($item['gravity'] != Item::GRAVITY_PARENT) && (Strings::normaliseLink($item['author-link']) != Strings::normaliseLink($owner['url']))) {
			Logger::info('OStatus entry is from author ' . $owner['url'] . ' - not from ' . $item['author-link'] . '. Quitting.');
		}

		$entry = self::entryHeader($doc, $owner, $item, $toplevel);

		$verb = ActivityNamespace::ACTIVITY_SCHEMA . 'favorite';
		self::entryContent($doc, $entry, $item, $owner, 'Favorite', $verb, false);

		$parent = Post::selectFirst([], ['uri' => $item['thr-parent'], 'uid' => $item['uid']]);
		if (DBA::isResult($parent)) {
			$as_object = $doc->createElement('activity:object');

			XML::addElement($doc, $as_object, 'activity:object-type', self::constructObjecttype($parent));

			self::entryContent($doc, $as_object, $parent, $owner, 'New entry');

			$entry->appendChild($as_object);
		}

		self::entryFooter($doc, $entry, $item, $owner);

		return $entry;
	}

	/**
	 * Adds the person object element to the XML document
	 *
	 * @param DOMDocument $doc     XML document
	 * @param array       $owner   Contact data of the poster
	 * @param array       $contact Contact data of the target
	 * @return DOMElement author element
	 */
	private static function addPersonObject(DOMDocument $doc, array $owner, array $contact): DOMElement
	{
		$object = $doc->createElement('activity:object');
		XML::addElement($doc, $object, 'activity:object-type', Activity\ObjectType::PERSON);

		if ($contact['network'] == Protocol::PHANTOM) {
			XML::addElement($doc, $object, 'id', $contact['url']);
			return $object;
		}

		XML::addElement($doc, $object, 'id', $contact['alias']);
		XML::addElement($doc, $object, 'title', $contact['nick']);

		XML::addElement($doc, $object, 'link', '', [
			'rel' => 'alternate',
			'type' => 'text/html',
			'href' => $contact['url'],
		]);

		$attributes = [
			'rel' => 'avatar',
			'type' => 'image/jpeg', // To-Do?
			'media:width' => 300,
			'media:height' => 300,
			'href' => $contact['photo'],
		];
		XML::addElement($doc, $object, 'link', '', $attributes);

		XML::addElement($doc, $object, 'poco:preferredUsername', $contact['nick']);
		XML::addElement($doc, $object, 'poco:displayName', $contact['name']);

		if (trim($contact['location']) != '') {
			$element = $doc->createElement('poco:address');
			XML::addElement($doc, $element, 'poco:formatted', $contact['location']);
			$object->appendChild($element);
		}

		return $object;
	}

	/**
	 * Adds a follow/unfollow entry element
	 *
	 * @param DOMDocument $doc      XML document
	 * @param array       $item     Data of the follow/unfollow message
	 * @param array       $owner    Contact data of the poster
	 * @param bool        $toplevel Is it for en entry element (false) or a feed entry (true)?
	 * @return DOMElement Entry element
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 * @throws \ImagickException
	 */
	private static function followEntry(DOMDocument $doc, array $item, array $owner, bool $toplevel): DOMElement
	{
		$item['id'] = $item['parent'] = 0;
		$item['created'] = $item['edited'] = date('c');
		$item['private'] = Item::PRIVATE;

		$contact = Contact::getByURL($item['follow']);
		$item['follow'] = $contact['url'];

		if ($contact['alias']) {
			$item['follow'] = $contact['alias'];
		} else {
			$contact['alias'] = $contact['url'];
		}

		$condition = ['uid' => $owner['uid'], 'nurl' => Strings::normaliseLink($contact['url'])];
		$user_contact = DBA::selectFirst('contact', ['id'], $condition);

		if (DBA::isResult($user_contact)) {
			$connect_id = $user_contact['id'];
		} else {
			$connect_id = 0;
		}

		if ($item['verb'] == Activity::FOLLOW) {
			$message = DI::l10n()->t('%s is now following %s.');
			$title = DI::l10n()->t('following');
			$action = 'subscription';
		} else {
			$message = DI::l10n()->t('%s stopped following %s.');
			$title = DI::l10n()->t('stopped following');
			$action = 'unfollow';
		}

		$item['uri'] = $item['parent-uri'] = $item['thr-parent']
				= 'tag:' . DI::baseUrl()->getHost() .
				  ','.date('Y-m-d').':'.$action.':'.$owner['uid'].
				':person:'.$connect_id.':'.$item['created'];

		$item['body'] = sprintf($message, $owner['nick'], $contact['nick']);

		$entry = self::entryHeader($doc, $owner, $item, $toplevel);

		self::entryContent($doc, $entry, $item, $owner, $title);

		$object = self::addPersonObject($doc, $owner, $contact);
		$entry->appendChild($object);

		self::entryFooter($doc, $entry, $item, $owner);

		return $entry;
	}

	/**
	 * Adds a regular entry element
	 *
	 * @param DOMDocument $doc       XML document
	 * @param array       $item      Data of the item that is to be posted
	 * @param array       $owner     Contact data of the poster
	 * @param bool        $toplevel  Is it for en entry element (false) or a feed entry (true)?
	 * @return DOMElement Entry element
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 * @throws \ImagickException
	 */
	private static function noteEntry(DOMDocument $doc, array $item, array $owner, bool $toplevel): DOMElement
	{
		if (($item['gravity'] != Item::GRAVITY_PARENT) && (Strings::normaliseLink($item['author-link']) != Strings::normaliseLink($owner['url']))) {
			Logger::info('OStatus entry is from author ' . $owner['url'] . ' - not from ' . $item['author-link'] . '. Quitting.');
		}

		if (!$toplevel) {
			if (!empty($item['title'])) {
				$title = BBCode::convertForUriId($item['uri-id'], $item['title'], BBCode::OSTATUS);
			} else {
				$title = sprintf('New note by %s', $owner['nick']);
			}
		} else {
			$title = sprintf('New comment by %s', $owner['nick']);
		}

		$entry = self::entryHeader($doc, $owner, $item, $toplevel);

		XML::addElement($doc, $entry, 'activity:object-type', Activity\ObjectType::NOTE);

		self::entryContent($doc, $entry, $item, $owner, $title, '', true);

		self::entryFooter($doc, $entry, $item, $owner, true);

		return $entry;
	}

	/**
	 * Adds a header element to the XML document
	 *
	 * @param DOMDocument $doc      XML document
	 * @param array       $owner    Contact data of the poster
	 * @param array       $item
	 * @param bool        $toplevel Is it for en entry element (false) or a feed entry (true)?
	 * @return DOMElement The entry element where the elements are added
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 * @throws \ImagickException
	 */
	public static function entryHeader(DOMDocument $doc, array $owner, array $item, bool $toplevel): DOMElement
	{
		if (!$toplevel) {
			$entry = $doc->createElement('entry');

			if ($owner['contact-type'] == Contact::TYPE_COMMUNITY) {
				$entry->setAttribute('xmlns:activity', ActivityNamespace::ACTIVITY);

				$contact = Contact::getByURL($item['author-link']) ?: $owner;
				$contact['nickname'] = $contact['nickname'] ?? $contact['nick'];
				$author = self::addAuthor($doc, $contact, false);
				$entry->appendChild($author);
			}
		} else {
			$entry = $doc->createElementNS(ActivityNamespace::ATOM1, 'entry');

			$entry->setAttribute('xmlns:thr', ActivityNamespace::THREAD);
			$entry->setAttribute('xmlns:georss', ActivityNamespace::GEORSS);
			$entry->setAttribute('xmlns:activity', ActivityNamespace::ACTIVITY);
			$entry->setAttribute('xmlns:media', ActivityNamespace::MEDIA);
			$entry->setAttribute('xmlns:poco', ActivityNamespace::POCO);
			$entry->setAttribute('xmlns:ostatus', ActivityNamespace::OSTATUS);
			$entry->setAttribute('xmlns:statusnet', ActivityNamespace::STATUSNET);
			$entry->setAttribute('xmlns:mastodon', ActivityNamespace::MASTODON);

			$author = self::addAuthor($doc, $owner);
			$entry->appendChild($author);
		}

		return $entry;
	}

	/**
	 * Adds elements to the XML document
	 *
	 * @param DOMDocument $doc       XML document
	 * @param DOMElement  $entry     Entry element where the content is added
	 * @param array       $item      Data of the item that is to be posted
	 * @param array       $owner     Contact data of the poster
	 * @param string      $title     Title for the post
	 * @param string      $verb      The activity verb
	 * @param bool        $complete  Add the "status_net" element?
	 * @return void
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 */
	private static function entryContent(DOMDocument $doc, DOMElement $entry, array $item, array $owner, string $title, string $verb = '', bool $complete = true)
	{
		if ($verb == '') {
			$verb = self::constructVerb($item);
		}

		XML::addElement($doc, $entry, 'id', $item['uri']);
		XML::addElement($doc, $entry, 'title', html_entity_decode($title, ENT_QUOTES, 'UTF-8'));

		$body = Post\Media::addAttachmentsToBody($item['uri-id'], DI::contentItem()->addSharedPost($item));
		$body = Post\Media::addHTMLLinkToBody($item['uri-id'], $body);

		if (!empty($item['title'])) {
			$body = '[b]' . $item['title'] . "[/b]\n\n" . $body;
		}

		$body = BBCode::convertForUriId($item['uri-id'], $body, BBCode::OSTATUS);

		XML::addElement($doc, $entry, 'content', $body, ['type' => 'html']);

		XML::addElement($doc, $entry, 'link', '', [
			'rel' => 'alternate',
			'type' => 'text/html',
			'href' => DI::baseUrl() . '/display/' . $item['guid'],
		]);

		if ($complete && ($item['id'] > 0)) {
			XML::addElement($doc, $entry, 'status_net', '', ['notice_id' => $item['id']]);
		}

		XML::addElement($doc, $entry, 'activity:verb', $verb);

		XML::addElement($doc, $entry, 'published', DateTimeFormat::utc($item['created'] . '+00:00', DateTimeFormat::ATOM));
		XML::addElement($doc, $entry, 'updated', DateTimeFormat::utc($item['edited'] . '+00:00', DateTimeFormat::ATOM));
	}

	/**
	 * Adds the elements at the foot of an entry to the XML document
	 *
	 * @param DOMDocument $doc       XML document
	 * @param object      $entry     The entry element where the elements are added
	 * @param array       $item      Data of the item that is to be posted
	 * @param array       $owner     Contact data of the poster
	 * @param bool        $complete  default true
	 * @return void
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 */
	private static function entryFooter(DOMDocument $doc, $entry, array $item, array $owner, bool $complete = true)
	{
		$mentioned = [];

		if ($item['gravity'] != Item::GRAVITY_PARENT) {
			$parent = Post::selectFirst(['guid', 'author-link', 'owner-link'], ['id' => $item['parent']]);

			$thrparent = Post::selectFirst(['guid', 'author-link', 'owner-link', 'plink'], ['uid' => $owner['uid'], 'uri' => $item['thr-parent']]);

			if (DBA::isResult($thrparent)) {
				$mentioned[$thrparent['author-link']] = $thrparent['author-link'];
				$mentioned[$thrparent['owner-link']]  = $thrparent['owner-link'];
				$parent_plink                         = $thrparent['plink'];
			} elseif (DBA::isResult($parent)) {
				$mentioned[$parent['author-link']] = $parent['author-link'];
				$mentioned[$parent['owner-link']]  = $parent['owner-link'];
				$parent_plink                      = DI::baseUrl() . '/display/' . $parent['guid'];
			} else {
				DI::logger()->notice('Missing parent and thr-parent for child item', ['item' => $item]);
			}

			if (isset($parent_plink)) {
				$attributes = [
					'ref'  => $item['thr-parent'],
					'href' => $parent_plink];
				XML::addElement($doc, $entry, 'thr:in-reply-to', '', $attributes);

				$attributes = [
					'rel'  => 'related',
					'href' => $parent_plink];
				XML::addElement($doc, $entry, 'link', '', $attributes);
			}
		}

		if (intval($item['parent']) > 0) {
			$conversation_href = $conversation_uri = $item['conversation'];

			XML::addElement($doc, $entry, 'link', '', ['rel' => 'ostatus:conversation', 'href' => $conversation_href]);

			$attributes = [
				'href' => $conversation_href,
				'local_id' => $item['parent'],
				'ref' => $conversation_uri,
			];

			XML::addElement($doc, $entry, 'ostatus:conversation', $conversation_uri, $attributes);
		}

		// uri-id isn't present for follow entry pseudo-items
		$tags = Tag::getByURIId($item['uri-id'] ?? 0);
		foreach ($tags as $tag) {
			$mentioned[$tag['url']] = $tag['url'];
		}

		// Make sure that mentions are accepted (GNU Social has problems with mixing HTTP and HTTPS)
		$newmentions = [];
		foreach ($mentioned as $mention) {
			$newmentions[str_replace('http://', 'https://', $mention)] = str_replace('http://', 'https://', $mention);
			$newmentions[str_replace('https://', 'http://', $mention)] = str_replace('https://', 'http://', $mention);
		}
		$mentioned = $newmentions;

		foreach ($mentioned as $mention) {
			$contact = Contact::getByURL($mention, false, ['contact-type']);
			if (!empty($contact) && ($contact['contact-type'] == Contact::TYPE_COMMUNITY)) {
				XML::addElement($doc, $entry, 'link', '', [
					'rel' => 'mentioned',
					'ostatus:object-type' => Activity\ObjectType::GROUP,
					'href' => $mention,
				]);
			} else {
				XML::addElement($doc, $entry, 'link', '', [
					'rel' => 'mentioned',
					'ostatus:object-type' => Activity\ObjectType::PERSON,
						'href' => $mention,
				]);
			}
		}

		if ($owner['contact-type'] == Contact::TYPE_COMMUNITY) {
			XML::addElement($doc, $entry, 'link', '', [
				'rel' => 'mentioned',
				'ostatus:object-type' => 'http://activitystrea.ms/schema/1.0/group',
				'href' => $owner['url']
			]);
		}

		if ($item['private'] != Item::PRIVATE) {
			XML::addElement($doc, $entry, 'link', '', ['rel' => 'ostatus:attention',
									'href' => 'http://activityschema.org/collection/public']);
			XML::addElement($doc, $entry, 'link', '', ['rel' => 'mentioned',
									'ostatus:object-type' => 'http://activitystrea.ms/schema/1.0/collection',
									'href' => 'http://activityschema.org/collection/public']);
			XML::addElement($doc, $entry, 'mastodon:scope', 'public');
		}

		foreach ($tags as $tag) {
			if ($tag['type'] == Tag::HASHTAG) {
				XML::addElement($doc, $entry, 'category', '', ['term' => $tag['name']]);
			}
		}

		self::getAttachment($doc, $entry, $item);

		if ($complete && ($item['id'] > 0)) {
			$app = $item['app'];
			if ($app == '') {
				$app = 'web';
			}

			$attributes = ['local_id' => $item['id'], 'source' => $app];

			if (isset($parent['id'])) {
				$attributes['repeat_of'] = $parent['id'];
			}

			if ($item['coord'] != '') {
				XML::addElement($doc, $entry, 'georss:point', $item['coord']);
			}

			XML::addElement($doc, $entry, 'statusnet:notice_info', '', $attributes);
		}
	}

	/**
	 * Creates the XML feed for a given nickname
	 *
	 * Supported filters:
	 * - activity (default): all the public posts
	 * - posts: all the public top-level posts
	 * - comments: all the public replies
	 *
	 * Updates the provided last_update parameter if the result comes from the
	 * cache or it is empty
	 *
	 * @param string  $owner_nick  Nickname of the feed owner
	 * @param string  $last_update Date of the last update (in "Y-m-d H:i:s" format)
	 * @param integer $max_items   Number of maximum items to fetch
	 * @param string  $filter      Feed items filter (activity, posts or comments)
	 * @param boolean $nocache     Wether to bypass caching
	 * @return string XML feed or empty string on error
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 * @throws \ImagickException
	 */
	public static function feed(string $owner_nick, string &$last_update, int $max_items = 300, string $filter = 'activity', bool $nocache = false): string
	{
		$stamp = microtime(true);

		$owner = User::getOwnerDataByNick($owner_nick);
		if (!$owner) {
			return '';
		}

		$cachekey = 'ostatus:feed:' . $owner_nick . ':' . $filter . ':' . $last_update;

		$previous_created = $last_update;

		// Don't cache when the last item was posted less than 15 minutes ago (Cache duration)
		if ((time() - strtotime($owner['last-item'])) < 15*60) {
			$result = DI::cache()->get($cachekey);
			if (!$nocache && !is_null($result)) {
				Logger::info('Feed duration: ' . number_format(microtime(true) - $stamp, 3) . ' - ' . $owner_nick . ' - ' . $filter . ' - ' . $previous_created . ' (cached)');
				$last_update = $result['last_update'];
				return $result['feed'];
			}
		}

		if (!strlen($last_update)) {
			$last_update = 'now -30 days';
		}

		$check_date = DateTimeFormat::utc($last_update);
		$authorid = Contact::getIdForURL($owner['url']);

		$condition = [
			"`uid` = ? AND `received` > ? AND NOT `deleted` AND `private` != ? AND `visible` AND `wall` AND `parent-network` IN (?, ?)",
			$owner['uid'],
			$check_date,
			Item::PRIVATE,
			Protocol::OSTATUS,
			Protocol::DFRN,
		];

		if ($filter === 'comments') {
			$condition[0] .= " AND `object-type` = ? ";
			$condition[] = Activity\ObjectType::COMMENT;
		}

		if ($owner['contact-type'] != Contact::TYPE_COMMUNITY) {
			$condition[0] .= " AND `contact-id` = ? AND `author-id` = ?";
			$condition[] = $owner['id'];
			$condition[] = $authorid;
		}

		$params = ['order' => ['received' => true], 'limit' => $max_items];

		if ($filter === 'posts') {
			$ret = Post::selectThread([], $condition, $params);
		} else {
			$ret = Post::select([], $condition, $params);
		}

		$items = Post::toArray($ret);

		$doc = new DOMDocument('1.0', 'utf-8');
		$doc->formatOutput = true;

		$root = self::addHeader($doc, $owner, $filter);

		foreach ($items as $item) {
			if (DI::config()->get('system', 'ostatus_debug')) {
				$item['body'] .= '🍼';
			}

			if (in_array($item['verb'], [Activity::FOLLOW, Activity::O_UNFOLLOW, Activity::LIKE])) {
				continue;
			}

			$entry = self::entry($doc, $item, $owner, false);
			$root->appendChild($entry);

			if ($last_update < $item['created']) {
				$last_update = $item['created'];
			}
		}

		$feeddata = trim($doc->saveXML());

		$msg = ['feed' => $feeddata, 'last_update' => $last_update];
		DI::cache()->set($cachekey, $msg, Duration::QUARTER_HOUR);

		Logger::info('Feed duration: ' . number_format(microtime(true) - $stamp, 3) . ' - ' . $owner_nick . ' - ' . $filter . ' - ' . $previous_created);

		return $feeddata;
	}

	/**
	 * Creates the XML for a salmon message
	 *
	 * @param array $item  Data of the item that is to be posted
	 * @param array $owner Contact data of the poster
	 *
	 * @return string XML for the salmon
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 * @throws \ImagickException
	 */
	public static function salmon(array $item, array $owner): string
	{
		$doc = new DOMDocument('1.0', 'utf-8');
		$doc->formatOutput = true;

		if (DI::config()->get('system', 'ostatus_debug')) {
			$item['body'] .= '🐟';
		}

		$entry = self::entry($doc, $item, $owner, true);

		$doc->appendChild($entry);

		return trim($doc->saveXML());
	}

	/**
	 * Checks if the given contact url does support OStatus
	 *
	 * @param string  $url    profile url
	 * @return boolean
	 * @throws \Friendica\Network\HTTPException\InternalServerErrorException
	 * @throws \ImagickException
	 */
	public static function isSupportedByContactUrl(string $url): bool
	{
		$probe = Probe::uri($url, Protocol::OSTATUS);
		return $probe['network'] == Protocol::OSTATUS;
	}
}