<?php
// This file is part of GNU social - https://www.gnu.org/software/social
//
// GNU social 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.
//
// GNU social 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 GNU social.  If not, see <http://www.gnu.org/licenses/>.

/**
 * OStatusPlugin implementation for GNU Social
 * Depends on: WebFinger plugin
 *
 * @package   OStatusPlugin
 * @author    Brion Vibber <brion@status.net>
 * @copyright 2009-2010 StatusNet, Inc.
 * @license   https://www.gnu.org/licenses/agpl.html GNU AGPL v3 or later
 */


defined('GNUSOCIAL') || die();

require_once __DIR__ . DIRECTORY_SEPARATOR . 'lib' . DIRECTORY_SEPARATOR . 'util.php';

class OStatusPlugin extends Plugin
{
    const PLUGIN_VERSION = '2.1.0';

    /**
     * Hook for RouterInitialized event.
     *
     * @param URLMapper $m path-to-action mapper
     * @return boolean hook return
     */
    public function onRouterInitialized(URLMapper $m)
    {
        // Discovery actions
        $m->connect(
            'main/ostatustag',
            ['action' => 'ostatustag']
        );
        $m->connect(
            'main/ostatustag?nickname=:nickname',
            ['action'   => 'ostatustag'],
            ['nickname' => '[A-Za-z0-9_-]+']
        );
        $m->connect(
            'main/ostatus/group/:group',
            ['action' => 'ostatusinit'],
            ['group'  => '[A-Za-z0-9_-]+']
        );
        $m->connect(
            'main/ostatus/peopletag/:peopletag/tagger/:tagger',
            ['action' => 'ostatusinit'],
            [
                'tagger'    => '[A-Za-z0-9_-]+',
                'peopletag' => '[A-Za-z0-9_-]+',
            ]
        );
        $m->connect(
            'main/ostatus',
            ['action' => 'ostatusinit']
        );

        // Remote subscription actions
        $m->connect(
            'main/ostatusgroup',
            ['action' => 'ostatusgroup']
        );
        $m->connect(
            'main/ostatuspeopletag',
            ['action' => 'ostatuspeopletag']
        );

        // WebSub actions
        $m->connect('main/push/hub', ['action' => 'pushhub']);

        $m->connect(
            'main/push/callback/:feed',
            ['action' => 'pushcallback'],
            ['feed' => '[0-9]+']
        );

        // Salmon endpoint
        $m->connect(
            'main/salmon/user/:id',
            ['action' => 'usersalmon'],
            ['id' => '[0-9]+']
        );
        $m->connect(
            'main/salmon/group/:id',
            ['action' => 'groupsalmon'],
            ['id' => '[0-9]+']
        );
        $m->connect(
            'main/salmon/peopletag/:id',
            ['action' => 'peopletagsalmon'],
            ['id' => '[0-9]+']
        );
        return true;
    }

    /**
     * Set up queue handlers for outgoing hub pushes
     * @param QueueManager $qm
     * @return boolean hook return
     */
    public function onEndInitializeQueueManager(QueueManager $qm)
    {
        // Prepare outgoing distributions after notice save.
        $qm->connect('ostatus', 'OStatusQueueHandler');

        // Outgoing from our internal WebSub hub
        $qm->connect('hubconf', 'HubConfQueueHandler');
        $qm->connect('hubprep', 'HubPrepQueueHandler');

        $qm->connect('hubout', 'HubOutQueueHandler');

        // Outgoing Salmon replies (when we don't need a return value)
        $qm->connect('salmon', 'SalmonQueueHandler');

        // Incoming from a foreign WebSub hub
        $qm->connect('pushin', 'PushInQueueHandler');

        // Re-subscribe feeds that need renewal
        $qm->connect('pushrenew', 'PushRenewQueueHandler');
        return true;
    }

    /**
     * Put saved notices into the queue for pubsub distribution.
     */
    public function onStartEnqueueNotice($notice, &$transports)
    {
        if ($notice->inScope(null) && $notice->getProfile()->hasRight(Right::PUBLICNOTICE)) {
            $transports[] = 'ostatus';
            $this->log(LOG_INFO, "OSTATUS [{$notice->getID()}]: queued for OStatus processing");
        } else {
            // FIXME: we don't do privacy-controlled OStatus updates yet.
            // once that happens, finer grain of control here.
            $this->log(LOG_NOTICE, "OSTATUS [{$notice->getID()}]: Not queueing because of privacy; scope = {$notice->scope}");
        }
        return true;
    }

    /**
     * Set up a WebSub hub link to our internal link for canonical timeline
     * Atom feeds for users and groups.
     */
    public function onStartApiAtom($feed)
    {
        $id = null;

        if ($feed instanceof AtomUserNoticeFeed) {
            $salmonAction = 'usersalmon';
            $user = $feed->getUser();
            $id   = $user->id;
            $profile = $user->getProfile();
        } elseif ($feed instanceof AtomGroupNoticeFeed) {
            $salmonAction = 'groupsalmon';
            $group = $feed->getGroup();
            $id = $group->id;
        } elseif ($feed instanceof AtomListNoticeFeed) {
            $salmonAction = 'peopletagsalmon';
            $peopletag = $feed->getList();
            $id = $peopletag->id;
        } else {
            return true;
        }

        if (!empty($id)) {
            $hub = common_config('ostatus', 'hub');
            if (empty($hub)) {
                // Updates will be handled through our internal WebSub hub.
                $hub = common_local_url('pushhub');
            }
            $feed->addLink($hub, array('rel' => 'hub'));

            // Also, we'll add in the salmon link
            $salmon = common_local_url($salmonAction, array('id' => $id));
            $feed->addLink($salmon, array('rel' => Salmon::REL_SALMON));

            // XXX: these are deprecated, but StatusNet only looks for NS_REPLIES
            $feed->addLink($salmon, array('rel' => Salmon::NS_REPLIES));
            $feed->addLink($salmon, array('rel' => Salmon::NS_MENTIONS));
        }

        return true;
    }

    /**
     * Add in an OStatus list button
     *
     * @param HTMLOutputter $output
     * @param Profile $profile
     * @return bool hook return value
     */
    public function onStartProfileRemoteSubscribe(HTMLOutputter $output, Profile $profile): bool
    {
        $this->onStartProfileListItemActionElements($output);
        return true;
    }

    public function onStartGroupSubscribe($widget, $group)
    {
        $cur = common_current_user();

        if (empty($cur)) {
            $widget->out->elementStart('li', 'entity_subscribe');

            $url = common_local_url(
                'ostatusinit',
                ['group' => $group->nickname]
            );
            $widget->out->element(
                'a',
                [
                    'href' => $url,
                    'class' => 'entity_remote_subscribe',
                ],
                // TRANS: Link to subscribe to a remote entity.
                _m('Subscribe')
            );

            $widget->out->elementEnd('li');
            return false;
        }

        return true;
    }

    public function onStartSubscribePeopletagForm($output, $peopletag)
    {
        $cur = common_current_user();

        if (empty($cur)) {
            $output->elementStart('li', 'entity_subscribe');
            $profile = $peopletag->getTagger();
            $url = common_local_url(
                'ostatusinit',
                ['tagger' => $profile->nickname, 'peopletag' => $peopletag->tag]
            );
            $output->element(
                'a',
                [
                    'href'  => $url,
                    'class' => 'entity_remote_subscribe',
                ],
                // TRANS: Link to subscribe to a remote entity.
                _m('Subscribe')
            );

            $output->elementEnd('li');
            return false;
        }

        return true;
    }

    /*
     * If the field being looked for is URI look for the profile
     */
    public function onStartProfileCompletionSearch($action, $profile, $search_engine)
    {
        if ($action->field == 'uri') {
            $profile->joinAdd(['id', 'user:id']);
            $profile->whereAdd("uri LIKE '%" . $profile->escape($q) . "%'");
            $profile->query();

            $validate = new Validate();

            if ($profile->N == 0) {
                try {
                    if ($validate->email($q)) {
                        $oprofile = Ostatus_profile::ensureWebfinger($q);
                    } elseif ($validate->uri($q)) {
                        $oprofile = Ostatus_profile::ensureProfileURL($q);
                    } else {
                        // TRANS: Exception in OStatus when invalid URI was entered.
                        throw new Exception(_m('Invalid URI.'));
                    }
                    return $this->filter(array($oprofile->localProfile()));
                } catch (Exception $e) {
                    // TRANS: Error message in OStatus plugin. Do not translate the domain names example.com
                    // TRANS: and example.net, as these are official standard domain names for use in examples.
                    $this->msg = _m("Sorry, we could not reach that address. Please make sure that the OStatus address is like nickname@example.com or http://example.net/nickname.");
                    return array();
                }
            }
            return false;
        }
        return true;
    }

    /**
     * Webfinger matches: @user@example.com or even @user--one.george_orwell@1984.biz
     * @param   string  $text       The text from which to extract webfinger IDs
     * @param   string  $preMention Character(s) that signals a mention ('@', '!'...)
     *
     * @return  array   The matching IDs (without $preMention) and each respective position in the given string.
     */
    public static function extractWebfingerIds($text, $preMention = '@')
    {
        $wmatches = array();
        $result = preg_match_all(
            '/(?<!\S)' . preg_quote($preMention, '/') . '(' . Nickname::WEBFINGER_FMT . ')/',
            $text,
            $wmatches,
            PREG_OFFSET_CAPTURE
        );
        if ($result === false) {
            common_log(LOG_ERR, __METHOD__ . ': Error parsing webfinger IDs from text (preg_last_error=='.preg_last_error().').');
            return [];
        } elseif (count($wmatches)) {
            common_debug(sprintf('Found %d matches for WebFinger IDs: %s', count($wmatches), _ve($wmatches)));
        }
        return $wmatches[1];
    }

    /**
     * Profile URL matches: @example.com/mublog/user
     * @param   string  $text       The text from which to extract URL mentions
     * @param   string  $preMention Character(s) that signals a mention ('@', '!'...)
     *
     * @return  array   The matching URLs (without @ or acct:) and each respective position in the given string.
     */
    public static function extractUrlMentions($text, $preMention = '@')
    {
        $wmatches = array();
        // In the regexp below we need to match / _before_ URL_REGEX_VALID_PATH_CHARS because it otherwise gets merged
        // with the TLD before (but / is in URL_REGEX_VALID_PATH_CHARS anyway, it's just its positioning that is important)
        $result = preg_match_all(
            '/(?:^|\s+)' . preg_quote($preMention, '/') . '(' . URL_REGEX_DOMAIN_NAME . '(?:\/[' . URL_REGEX_VALID_PATH_CHARS . ']*)*)/',
            $text,
            $wmatches,
            PREG_OFFSET_CAPTURE
        );
        if ($result === false) {
            common_log(LOG_ERR, __METHOD__ . ': Error parsing profile URL mentions from text (preg_last_error=='.preg_last_error().').');
            return [];
        } elseif (count($wmatches)) {
            common_debug(sprintf('Found %d matches for profile URL mentions: %s', count($wmatches), _ve($wmatches)));
        }
        return $wmatches[1];
    }

    /**
     * Find any explicit remote mentions. Accepted forms:
     *   Webfinger: @user@example.com
     *   Profile link: @example.com/mublog/user
     * @param Profile $sender
     * @param string $text input markup text
     * @param array &$mention in/out param: set of found mentions
     * @return boolean hook return value
     */
    public function onEndFindMentions(Profile $sender, $text, &$mentions)
    {
        $matches = array();

        foreach (self::extractWebfingerIds($text, '@') as $wmatch) {
            list($target, $pos) = $wmatch;
            $this->log(LOG_INFO, "Checking webfinger person '$target'");
            $profile = null;
            try {
                $oprofile = Ostatus_profile::ensureWebfinger($target);
                if (!$oprofile instanceof Ostatus_profile || !$oprofile->isPerson()) {
                    continue;
                }
                $profile = $oprofile->localProfile();
            } catch (OStatusShadowException $e) {
                // This means we got a local user in the webfinger lookup
                $profile = $e->profile;
            } catch (Exception $e) {
                $this->log(LOG_ERR, "Webfinger check failed: " . $e->getMessage());
                continue;
            }

            assert($profile instanceof Profile);

            $displayName = !empty($profile->nickname) && mb_strlen($profile->nickname) < mb_strlen($target)
                    ? $profile->getNickname()   // TODO: we could do getBestName() or getFullname() here
                    : $target;
            $url = $profile->getUri();
            if (!common_valid_http_url($url)) {
                $url = $profile->getUrl();
            }
            $matches[$pos] = array('mentioned' => array($profile),
                                   'type' => 'mention',
                                   'text' => $displayName,
                                   'position' => $pos,
                                   'length' => mb_strlen($target),
                                   'url' => $url);
        }

        // Doing groups in a separate routine because webfinger lookups don't work
        // remotely until everyone updates etc. etc.
        foreach (self::extractWebfingerIds($text, '!') as $wmatch) {
            list($target, $pos) = $wmatch;
            list($target_nickname, $target_hostname) = explode('@', parse_url($target, PHP_URL_PATH));
            $this->log(LOG_INFO, sprintf('Checking webfinger group %s as user %s on server %s', $target, $target_nickname, $target_hostname));

            $profile = null;
            if ($target_hostname === mb_strtolower(common_config('site', 'server'))) {
                try {
                    $profile = Local_group::getKV('nickname', $target_nickname)->getProfile();
                } catch (NoSuchGroupException $e) {
                    // referenced a local group which does not exist, so not returning it as a mention
                    $this->log(LOG_ERR, "Local group lookup failed: " . _ve($e->getMessage()));
                    continue;
                }
            } else {
                // XXX: Superhacky. Domain name can be incorrectly matched
                //      here. But since users are only members of groups
                //      they trust (of course they are!), the likelihood of
                //      a mention-hijacking is very very low... for now.
                $possible_groups = new User_group();
                $possible_groups->nickname = $target_nickname;
                if (!$possible_groups->find()) {
                    common_debug('No groups at all found with nickname: '._ve($target_nickname));
                    continue;
                }
                while ($possible_groups->fetch()) {
                    if (!$sender->isMember($possible_groups)) {
                        continue;
                    }
                    $group_hostname = mb_strtolower(parse_url($possible_groups->mainpage, PHP_URL_HOST));
                    if ($target_hostname === $group_hostname) {
                        common_debug(sprintf('Found group with nick@host (%s@%s) matching %s', _ve($possible_groups->nickname), _ve($group_hostname), _ve($target)));
                        $profile = $possible_groups->getProfile();
                        break;
                    }
                }
                $possible_groups->free();
                if (!$profile instanceof Profile) {
                    common_debug('Found groups with correct nickname but not hostname for: '._ve($target));
                    continue;
                }
            }

            assert($profile instanceof Profile);

            $displayName = !empty($profile->nickname) && mb_strlen($profile->nickname) < mb_strlen($target)
                    ? $profile->getNickname()   // TODO: we could do getBestName() or getFullname() here
                    : $target;
            $url = $profile->getUri();
            if (!common_valid_http_url($url)) {
                $url = $profile->getUrl();
            }
            $matches[$pos] = array('mentioned' => array($profile),
                                   'type' => 'group',
                                   'text' => $displayName,
                                   'position' => $pos,
                                   'length' => mb_strlen($target),
                                   'url' => $url);
        }

        foreach (self::extractUrlMentions($text) as $wmatch) {
            list($target, $pos) = $wmatch;
            $schemes = array('https', 'http');
            foreach ($schemes as $scheme) {
                $url = "$scheme://$target";
                $this->log(LOG_INFO, "Checking profile address '$url'");
                try {
                    $oprofile = Ostatus_profile::ensureProfileURL($url);
                    if ($oprofile instanceof Ostatus_profile && !$oprofile->isGroup()) {
                        $profile = $oprofile->localProfile();
                        $displayName = !empty($profile->nickname) && mb_strlen($profile->nickname) < mb_strlen($target) ?
                                $profile->nickname : $target;
                        $matches[$pos] = array('mentioned' => array($profile),
                                               'type' => 'mention',
                                               'text' => $displayName,
                                               'position' => $pos,
                                               'length' => mb_strlen($target),
                                               'url' => $profile->getUrl());
                        break;
                    }
                } catch (Exception $e) {
                    $this->log(LOG_ERR, "Profile check failed: " . $e->getMessage());
                }
            }
        }

        foreach ($mentions as $i => $other) {
            // If we share a common prefix with a local user, override it!
            $pos = $other['position'];
            if (isset($matches[$pos])) {
                $mentions[$i] = $matches[$pos];
                unset($matches[$pos]);
            }
        }
        foreach ($matches as $mention) {
            $mentions[] = $mention;
        }

        return true;
    }

    /**
     * Allow remote profile references to be used in commands:
     *   sub update@status.net
     *   whois evan@identi.ca
     *   reply http://identi.ca/evan hey what's up
     *
     * @param Command $command
     * @param string $arg
     * @param Profile &$profile
     * @return hook return code
     */
    public function onStartCommandGetProfile($command, $arg, &$profile)
    {
        $oprofile = $this->pullRemoteProfile($arg);
        if ($oprofile instanceof Ostatus_profile && !$oprofile->isGroup()) {
            try {
                $profile = $oprofile->localProfile();
            } catch (NoProfileException $e) {
                // No locally stored profile found for remote profile
                return true;
            }
            return false;
        } else {
            return true;
        }
    }

    /**
     * Allow remote group references to be used in commands:
     *   join group+statusnet@identi.ca
     *   join http://identi.ca/group/statusnet
     *   drop identi.ca/group/statusnet
     *
     * @param Command $command
     * @param string $arg
     * @param User_group &$group
     * @return hook return code
     */
    public function onStartCommandGetGroup($command, $arg, &$group)
    {
        $oprofile = $this->pullRemoteProfile($arg);
        if ($oprofile instanceof Ostatus_profile && $oprofile->isGroup()) {
            $group = $oprofile->localGroup();
            return false;
        } else {
            return true;
        }
    }

    protected function pullRemoteProfile($arg)
    {
        $oprofile = null;
        if (preg_match('!^((?:\w+\.)*\w+@(?:\w+\.)*\w+(?:\w+\-\w+)*\.\w+)$!', $arg)) {
            // webfinger lookup
            try {
                return Ostatus_profile::ensureWebfinger($arg);
            } catch (Exception $e) {
                common_log(LOG_ERR, 'Webfinger lookup failed for ' .
                                    $arg . ': ' . $e->getMessage());
            }
        }

        // Look for profile URLs, with or without scheme:
        $urls = array();
        if (preg_match('!^https?://((?:\w+\.)*\w+(?:\w+\-\w+)*\.\w+(?:/\w+)+)$!', $arg)) {
            $urls[] = $arg;
        }
        if (preg_match('!^((?:\w+\.)*\w+(?:\w+\-\w+)*\.\w+(?:/\w+)+)$!', $arg)) {
            $schemes = array('http', 'https');
            foreach ($schemes as $scheme) {
                $urls[] = "$scheme://$arg";
            }
        }

        foreach ($urls as $url) {
            try {
                return Ostatus_profile::ensureProfileURL($url);
            } catch (Exception $e) {
                common_log(LOG_ERR, 'Profile lookup failed for ' .
                                    $arg . ': ' . $e->getMessage());
            }
        }
        return null;
    }

    public function onEndProfileSettingsActions($out) {
        $siteName = common_config('site', 'name');
        $js = 'navigator.registerContentHandler("application/vnd.mozilla.maybe.feed", "'.addslashes(common_local_url('RemoteFollowSub', null, array('profile' => '%s'))).'", "'.addslashes($siteName).'")';
        $out->elementStart('li');
        $out->element(
            'a',
            ['href' => 'javascript:' . $js],
            // TRANS: Option in profile settings to add this instance to Firefox as a feedreader
            _('Add to Firefox as feedreader')
        );
        $out->elementEnd('li');
    }

    /**
     * Make sure necessary tables are filled out.
     */
    public function onCheckSchema()
    {
        $schema = Schema::get();
        $schema->ensureTable('ostatus_profile', Ostatus_profile::schemaDef());
        $schema->ensureTable('feedsub', FeedSub::schemaDef());
        $schema->ensureTable('hubsub', HubSub::schemaDef());
        $schema->ensureTable('magicsig', Magicsig::schemaDef());
        return true;
    }

    public function onEndShowStylesheets(Action $action)
    {
        $action->cssLink($this->path('theme/base/css/ostatus.css'));
        return true;
    }

    public function onEndShowStatusNetScripts($action)
    {
        $action->script($this->path('js/ostatus.js'));
        return true;
    }

    /**
     * Override the "from ostatus" bit in notice lists to link to the
     * original post and show the domain it came from.
     *
     * @param Notice in $notice
     * @param string out &$name
     * @param string out &$url
     * @param string out &$title
     * @return mixed hook return code
     */
    public function onStartNoticeSourceLink($notice, &$name, &$url, &$title)
    {
        // If we don't handle this, keep the event handler going
        if (!in_array($notice->source, array('ostatus', 'share'))) {
            return true;
        }

        try {
            $url = $notice->getUrl();
            // If getUrl() throws exception, $url is never set

            $bits = parse_url($url);
            $domain = $bits['host'];
            if (substr($domain, 0, 4) == 'www.') {
                $name = substr($domain, 4);
            } else {
                $name = $domain;
            }

            // TRANS: Title. %s is a domain name.
            $title = sprintf(_m('Sent from %s via OStatus'), $domain);

            // Abort event handler, we have a name and URL!
            return false;
        } catch (InvalidUrlException $e) {
            // This just means we don't have the notice source data
            return true;
        }
    }

    /**
     * Send incoming WebSub feeds for OStatus endpoints in for processing.
     *
     * @param FeedSub $feedsub
     * @param DOMDocument $feed
     * @return mixed hook return code
     */
    public function onStartFeedSubReceive($feedsub, $feed)
    {
        $oprofile = Ostatus_profile::getKV('feeduri', $feedsub->uri);
        if ($oprofile instanceof Ostatus_profile) {
            $oprofile->processFeed($feed, 'push');
        } else {
            common_log(LOG_DEBUG, "No ostatus profile for incoming feed $feedsub->uri");
        }
    }

    /**
     * Tell the FeedSub infrastructure whether we have any active OStatus
     * usage for the feed; if not it'll be able to garbage-collect the
     * feed subscription.
     *
     * @param FeedSub $feedsub
     * @param integer $count in/out
     * @return mixed hook return code
     */
    public function onFeedSubSubscriberCount($feedsub, &$count)
    {
        $oprofile = Ostatus_profile::getKV('feeduri', $feedsub->uri);
        if ($oprofile instanceof Ostatus_profile) {
            $count += $oprofile->subscriberCount();
        }
        return true;
    }

    /**
     * When about to subscribe to a remote user, start a server-to-server
     * WebSub subscription if needed. If we can't establish that, abort.
     *
     * @fixme If something else aborts later, we could end up with a stray
     *        WebSub subscription. This is relatively harmless, though.
     *
     * @param Profile $profile  subscriber
     * @param Profile $other    subscribee
     *
     * @return hook return code
     *
     * @throws Exception
     */
    public function onStartSubscribe(Profile $profile, Profile $other)
    {
        if (!$profile->isLocal()) {
            return true;
        }

        $oprofile = Ostatus_profile::getKV('profile_id', $other->id);
        if (!$oprofile instanceof Ostatus_profile) {
            return true;
        }

        $oprofile->subscribe();
    }

    /**
     * Having established a remote subscription, send a notification to the
     * remote OStatus profile's endpoint.
     *
     * @param Profile $profile  subscriber
     * @param Profile $other    subscribee
     *
     * @return hook return code
     *
     * @throws Exception
     */
    public function onEndSubscribe(Profile $profile, Profile $other)
    {
        if (!$profile->isLocal()) {
            return true;
        }

        $oprofile = Ostatus_profile::getKV('profile_id', $other->id);
        if (!$oprofile instanceof Ostatus_profile) {
            return true;
        }

        $sub = Subscription::pkeyGet(array('subscriber' => $profile->id,
                                           'subscribed' => $other->id));

        $act = $sub->asActivity();

        $oprofile->notifyActivity($act, $profile);

        return true;
    }

    /**
     * Notify remote server and garbage collect unused feeds on unsubscribe.
     * @todo FIXME: Send these operations to background queues
     *
     * @param User $user
     * @param Profile $other
     * @return hook return value
     */
    public function onEndUnsubscribe(Profile $profile, Profile $other)
    {
        if (!$profile->isLocal()) {
            return true;
        }

        $oprofile = Ostatus_profile::getKV('profile_id', $other->id);
        if (!$oprofile instanceof Ostatus_profile) {
            return true;
        }

        // Drop the WebSub subscription if there are no other subscribers.
        $oprofile->garbageCollect();

        $act = new Activity();

        $act->verb = ActivityVerb::UNFOLLOW;

        $act->id   = TagURI::mint(
            'unfollow:%d:%d:%s',
            $profile->id,
            $other->id,
            common_date_iso8601(time())
        );

        $act->time    = time();
        // TRANS: Title for unfollowing a remote profile.
        $act->title   = _m('TITLE', 'Unfollow');
        // TRANS: Success message for unsubscribe from user attempt through OStatus.
        // TRANS: %1$s is the unsubscriber's name, %2$s is the unsubscribed user's name.
        $act->content = sprintf(
            _m('%1$s stopped following %2$s.'),
            $profile->getBestName(),
            $other->getBestName()
        );

        $act->actor   = $profile->asActivityObject();
        $act->objects[] = $other->asActivityObject();

        $oprofile->notifyActivity($act, $profile);

        return true;
    }

    /**
     * When one of our local users tries to join a remote group,
     * notify the remote server. If the notification is rejected,
     * deny the join.
     *
     * @param User_group $group
     * @param Profile    $profile
     *
     * @return mixed hook return value
     * @throws Exception of various kinds, some from $oprofile->subscribe();
     */
    public function onStartJoinGroup($group, $profile)
    {
        $oprofile = Ostatus_profile::getKV('group_id', $group->id);
        if (!$oprofile instanceof Ostatus_profile) {
            return true;
        }

        $oprofile->subscribe();

        // NOTE: we don't use Group_member::asActivity() since that record
        // has not yet been created.

        $act = new Activity();
        $act->id = TagURI::mint(
            'join:%d:%d:%s',
            $profile->id,
            $group->id,
            common_date_iso8601(time())
        );

        $act->actor = $profile->asActivityObject();
        $act->verb = ActivityVerb::JOIN;
        $act->objects[] = $oprofile->asActivityObject();

        $act->time = time();
        // TRANS: Title for joining a remote groep.
        $act->title = _m('TITLE', 'Join');
        // TRANS: Success message for subscribe to group attempt through OStatus.
        // TRANS: %1$s is the member name, %2$s is the subscribed group's name.
        $act->content = sprintf(
            _m('%1$s has joined group %2$s.'),
            $profile->getBestName(),
            $oprofile->getBestName()
        );

        if ($oprofile->notifyActivity($act, $profile)) {
            return true;
        } else {
            $oprofile->garbageCollect();
            // TRANS: Exception thrown when joining a remote group fails.
            throw new Exception(_m('Failed joining remote group.'));
        }
    }

    /**
     * When one of our local users leaves a remote group, notify the remote
     * server.
     *
     * @fixme Might be good to schedule a resend of the leave notification
     * if it failed due to a transitory error. We've canceled the local
     * membership already anyway, but if the remote server comes back up
     * it'll be left with a stray membership record.
     *
     * @param User_group $group
     * @param Profile $profile
     *
     * @return mixed hook return value
     */
    public function onEndLeaveGroup($group, $profile)
    {
        $oprofile = Ostatus_profile::getKV('group_id', $group->id);
        if (!$oprofile instanceof Ostatus_profile) {
            return true;
        }

        // Drop the WebSub subscription if there are no other subscribers.
        $oprofile->garbageCollect();

        $member = $profile;

        $act = new Activity();
        $act->id = TagURI::mint(
            'leave:%d:%d:%s',
            $member->id,
            $group->id,
            common_date_iso8601(time())
        );

        $act->actor = $member->asActivityObject();
        $act->verb = ActivityVerb::LEAVE;
        $act->objects[] = $oprofile->asActivityObject();

        $act->time = time();
        // TRANS: Title for leaving a remote group.
        $act->title = _m('TITLE', 'Leave');
        // TRANS: Success message for unsubscribe from group attempt through OStatus.
        // TRANS: %1$s is the member name, %2$s is the unsubscribed group's name.
        $act->content = sprintf(
            _m('%1$s has left group %2$s.'),
            $member->getBestName(),
            $oprofile->getBestName()
        );

        $oprofile->notifyActivity($act, $member);
    }

    /**
     * When one of our local users tries to subscribe to a remote peopletag,
     * notify the remote server. If the notification is rejected,
     * deny the subscription.
     *
     * @param Profile_list $peopletag
     * @param User         $user
     *
     * @return mixed hook return value
     * @throws Exception of various kinds, some from $oprofile->subscribe();
     */

    public function onStartSubscribePeopletag($peopletag, $user)
    {
        $oprofile = Ostatus_profile::getKV('peopletag_id', $peopletag->id);
        if (!$oprofile instanceof Ostatus_profile) {
            return true;
        }

        $oprofile->subscribe();

        $sub = $user->getProfile();
        $tagger = Profile::getKV($peopletag->tagger);

        $act = new Activity();
        $act->id = TagURI::mint(
            'subscribe_peopletag:%d:%d:%s',
            $sub->id,
            $peopletag->id,
            common_date_iso8601(time())
        );

        $act->actor = $sub->asActivityObject();
        $act->verb = ActivityVerb::FOLLOW;
        $act->objects[] = $oprofile->asActivityObject();

        $act->time = time();
        // TRANS: Title for following a remote list.
        $act->title = _m('TITLE', 'Follow list');
        // TRANS: Success message for remote list follow through OStatus.
        // TRANS: %1$s is the subscriber name, %2$s is the list, %3$s is the lister's name.
        $act->content = sprintf(
            _m('%1$s is now following people listed in %2$s by %3$s.'),
            $sub->getBestName(),
            $oprofile->getBestName(),
            $tagger->getBestName()
        );

        if ($oprofile->notifyActivity($act, $sub)) {
            return true;
        } else {
            $oprofile->garbageCollect();
            // TRANS: Exception thrown when subscription to remote list fails.
            throw new Exception(_m('Failed subscribing to remote list.'));
        }
    }

    /**
     * When one of our local users unsubscribes to a remote peopletag, notify the remote
     * server.
     *
     * @param Profile_list $peopletag
     * @param User         $user
     *
     * @return mixed hook return value
     */

    public function onEndUnsubscribePeopletag($peopletag, $user)
    {
        $oprofile = Ostatus_profile::getKV('peopletag_id', $peopletag->id);
        if (!$oprofile instanceof Ostatus_profile) {
            return true;
        }

        // Drop the WebSub subscription if there are no other subscribers.
        $oprofile->garbageCollect();

        $sub = Profile::getKV($user->id);
        $tagger = Profile::getKV($peopletag->tagger);

        $act = new Activity();
        $act->id = TagURI::mint(
            'unsubscribe_peopletag:%d:%d:%s',
            $sub->id,
            $peopletag->id,
            common_date_iso8601(time())
        );

        $act->actor = $member->asActivityObject();
        $act->verb = ActivityVerb::UNFOLLOW;
        $act->objects[] = $oprofile->asActivityObject();

        $act->time = time();
        // TRANS: Title for unfollowing a remote list.
        $act->title = _m('Unfollow list');
        // TRANS: Success message for remote list unfollow through OStatus.
        // TRANS: %1$s is the subscriber name, %2$s is the list, %3$s is the lister's name.
        $act->content = sprintf(
            _m('%1$s stopped following the list %2$s by %3$s.'),
            $sub->getBestName(),
            $oprofile->getBestName(),
            $tagger->getBestName()
        );

        $oprofile->notifyActivity($act, $user);
    }

    /**
     * Notify remote users when their notices get favorited.
     *
     * @param Profile or User $profile of local user doing the faving
     * @param Notice $notice being favored
     * @return hook return value
     */
    public function onEndFavorNotice(Profile $profile, Notice $notice)
    {
        // Only distribute local users' favor actions, remote users
        // will have already distributed theirs.
        if (!$profile->isLocal()) {
            return true;
        }

        $oprofile = Ostatus_profile::getKV('profile_id', $notice->profile_id);
        if (!$oprofile instanceof Ostatus_profile) {
            return true;
        }

        $fav = Fave::pkeyGet(array('user_id' => $profile->id,
                                   'notice_id' => $notice->id));

        if (!$fav instanceof Fave) {
            // That's weird.
            // TODO: Make pkeyGet throw exception, since this is a critical failure.
            return true;
        }

        $act = $fav->asActivity();

        $oprofile->notifyActivity($act, $profile);

        return true;
    }

    /**
     * Notify remote user it has got a new people tag
     *   - tag verb is queued
     *   - the subscription is done immediately if not present
     *
     * @param Profile_tag $ptag the people tag that was created
     * @return hook return value
     * @throws Exception of various kinds, some from $oprofile->subscribe();
     */
    public function onEndTagProfile($ptag)
    {
        $oprofile = Ostatus_profile::getKV('profile_id', $ptag->tagged);
        if (!$oprofile instanceof Ostatus_profile) {
            return true;
        }

        $plist = $ptag->getMeta();
        if ($plist->private) {
            return true;
        }

        $act = new Activity();

        $tagger = $plist->getTagger();
        $tagged = Profile::getKV('id', $ptag->tagged);

        $act->verb = ActivityVerb::TAG;
        $act->id   = TagURI::mint(
            'tag_profile:%d:%d:%s',
            $plist->tagger,
            $plist->id,
            common_date_iso8601(time())
        );
        $act->time = time();
        // TRANS: Title for listing a remote profile.
        $act->title = _m('TITLE', 'List');
        // TRANS: Success message for remote list addition through OStatus.
        // TRANS: %1$s is the list creator's name, %2$s is the added list member, %3$s is the list name.
        $act->content = sprintf(
            _m('%1$s listed %2$s in the list %3$s.'),
            $tagger->getBestName(),
            $tagged->getBestName(),
            $plist->getBestName()
        );

        $act->actor  = $tagger->asActivityObject();
        $act->objects = array($tagged->asActivityObject());
        $act->target = ActivityObject::fromPeopletag($plist);

        $oprofile->notifyDeferred($act, $tagger);

        // initiate a WebSub subscription for the person being tagged
        $oprofile->subscribe();
        return true;
    }

    /**
     * Notify remote user that a people tag has been removed
     *   - untag verb is queued
     *   - the subscription is undone immediately if not required
     *     i.e garbageCollect()'d
     *
     * @param Profile_tag $ptag the people tag that was deleted
     * @return hook return value
     */
    public function onEndUntagProfile($ptag)
    {
        $oprofile = Ostatus_profile::getKV('profile_id', $ptag->tagged);
        if (!$oprofile instanceof Ostatus_profile) {
            return true;
        }

        $plist = $ptag->getMeta();
        if ($plist->private) {
            return true;
        }

        $act = new Activity();

        $tagger = $plist->getTagger();
        $tagged = Profile::getKV('id', $ptag->tagged);

        $act->verb = ActivityVerb::UNTAG;
        $act->id   = TagURI::mint(
            'untag_profile:%d:%d:%s',
            $plist->tagger,
            $plist->id,
            common_date_iso8601(time())
        );
        $act->time = time();
        // TRANS: Title for unlisting a remote profile.
        $act->title = _m('TITLE', 'Unlist');
        // TRANS: Success message for remote list removal through OStatus.
        // TRANS: %1$s is the list creator's name, %2$s is the removed list member, %3$s is the list name.
        $act->content = sprintf(
            _m('%1$s removed %2$s from the list %3$s.'),
            $tagger->getBestName(),
            $tagged->getBestName(),
            $plist->getBestName()
        );

        $act->actor  = $tagger->asActivityObject();
        $act->objects = array($tagged->asActivityObject());
        $act->target = ActivityObject::fromPeopletag($plist);

        $oprofile->notifyDeferred($act, $tagger);

        // unsubscribe to WebSub feed if no more required
        $oprofile->garbageCollect();

        return true;
    }

    /**
     * Notify remote users when their notices get de-favorited.
     *
     * @param Profile $profile Profile person doing the de-faving
     * @param Notice  $notice  Notice being favored
     *
     * @return hook return value
     */
    public function onEndDisfavorNotice(Profile $profile, Notice $notice)
    {
        // Only distribute local users' disfavor actions, remote users
        // will have already distributed theirs.
        if (!$profile->isLocal()) {
            return true;
        }

        $oprofile = Ostatus_profile::getKV('profile_id', $notice->profile_id);
        if (!$oprofile instanceof Ostatus_profile) {
            return true;
        }

        $act = new Activity();

        $act->verb = ActivityVerb::UNFAVORITE;
        $act->id   = TagURI::mint(
            'disfavor:%d:%d:%s',
            $profile->id,
            $notice->id,
            common_date_iso8601(time())
        );
        $act->time    = time();
        // TRANS: Title for unliking a remote notice.
        $act->title   = _m('Unlike');
        // TRANS: Success message for remove a favorite notice through OStatus.
        // TRANS: %1$s is the unfavoring user's name, %2$s is URI to the no longer favored notice.
        $act->content = sprintf(
            _m('%1$s no longer likes %2$s.'),
            $profile->getBestName(),
            $notice->getUrl()
        );

        $act->actor   = $profile->asActivityObject();
        $act->objects[]  = $notice->asActivityObject();

        $oprofile->notifyActivity($act, $profile);

        return true;
    }

    public function onStartGetProfileUri($profile, &$uri)
    {
        $oprofile = Ostatus_profile::getKV('profile_id', $profile->id);
        if ($oprofile instanceof Ostatus_profile) {
            $uri = $oprofile->uri;
            return false;
        }
        return true;
    }

    public function onStartUserGroupHomeUrl($group, &$url)
    {
        return $this->onStartUserGroupPermalink($group, $url);
    }

    public function onStartUserGroupPermalink($group, &$url)
    {
        $oprofile = Ostatus_profile::getKV('group_id', $group->id);
        if ($oprofile instanceof Ostatus_profile) {
            // @fixme this should probably be in the user_group table
            // @fixme this uri not guaranteed to be a profile page
            $url = $oprofile->uri;
            return false;
        }
    }

    public function onStartShowUserGroupsContent($action)
    {
        $this->showEntityRemoteSubscribe($action);

        return true;
    }

    public function onEndShowGroupsMiniList($action)
    {
        $this->showEntityRemoteSubscribe($action);

        return true;
    }

    public function showEntityRemoteSubscribe($action)
    {
        if (!$action->getScoped() instanceof Profile) {
            // early return if we're not logged in
            return true;
        }

        if ($action->getScoped()->sameAs($action->getTarget())) {
            $action->elementStart('div', 'entity_actions');
            $action->elementStart('p', array('id' => 'entity_remote_subscribe',
                                             'class' => 'entity_subscribe'));
            $action->element(
                'a',
                [
                    'href' => common_local_url('ostatusgroup'),
                    'class' => 'entity_remote_subscribe',
                ],
                // TRANS: Link text for link to remote subscribe.
                _m('Remote')
            );
            $action->elementEnd('p');
            $action->elementEnd('div');
        }
    }

    /**
     * Ping remote profiles with updates to this profile.
     * Salmon pings are queued for background processing.
     */
    public function onEndBroadcastProfile(Profile $profile)
    {
        $user = User::getKV('id', $profile->id);

        // Find foreign accounts I'm subscribed to that support Salmon pings.
        //
        // @fixme we could run updates through the WebSub feed too,
        // in which case we can skip Salmon pings to folks who
        // are also subscribed to me.
        $sql = "SELECT * FROM ostatus_profile " .
               "WHERE profile_id IN " .
               "(SELECT subscribed FROM subscription WHERE subscriber=%d) " .
               "OR group_id IN " .
               "(SELECT group_id FROM group_member WHERE profile_id=%d)";
        $oprofile = new Ostatus_profile();
        $oprofile->query(sprintf($sql, $profile->id, $profile->id));

        if ($oprofile->N == 0) {
            common_log(LOG_DEBUG, "No OStatus remote subscribees for $profile->nickname");
            return true;
        }

        $act = new Activity();

        $act->verb = ActivityVerb::UPDATE_PROFILE;
        $act->id   = TagURI::mint(
            'update-profile:%d:%s',
            $profile->id,
            common_date_iso8601(time())
        );
        $act->time    = time();
        // TRANS: Title for activity.
        $act->title   = _m('Profile update');
        // TRANS: Ping text for remote profile update through OStatus.
        // TRANS: %s is user that updated their profile.
        $act->content = sprintf(
            _m('%s has updated their profile page.'),
            $profile->getBestName()
        );

        $act->actor   = $profile->asActivityObject();
        $act->objects[]  = $act->actor;

        while ($oprofile->fetch()) {
            $oprofile->notifyDeferred($act, $profile);
        }

        return true;
    }

    public function onEndShowAccountProfileBlock(HTMLOutputter $out, Profile $profile)
    {
        if ($profile->isLocal()) {
            return true;
        }
        try {
            $oprofile = Ostatus_profile::fromProfile($profile);
        } catch (Exception $e) {
            // Not a remote Ostatus_profile! Maybe some other network
            // that has imported a non-local user?
            return true;
        }
        try {
            $feedsub = $oprofile->getFeedSub();
        } catch (NoResultException $e) {
            // No WebSub subscription has been attempted or exists for this profile
            // which is the case, say for remote profiles that are only included
            // via mentions or repeat/share.
            return true;
        }

        $websub_states = [
            'subscribe'   => _m('Pending'),
            'active'      => _m('Active'),
            'unsubscribe' => _m('Unsubscribing'),
            'nohub'       => _m('Polling'),
            'inactive'    => _m('Inactive'),
        ];
        $out->elementStart('dl', 'entity_tags ostatus_profile');
        $out->element('dt', null, _m('WebSub'));
        $out->element('dd', null, $websub_states[$feedsub->sub_state]);
        $out->elementEnd('dl');
    }

    // FIXME: This one can accept both an Action and a Widget. Confusing! Refactor to (HTMLOutputter $out, Profile $target)!
    public function onStartProfileListItemActionElements($item)
    {
        if (common_logged_in()) {
            // only non-logged in users get to see the "remote subscribe" form
            return true;
        }

        $target = $item->getTarget();

        if (!$target->isLocal()) {
            // we can (for now) only provide remote subscribe forms for local users
            return true;
        }

        if ($item instanceof ProfileAction) {
            $output = $item;
        } elseif ($item instanceof Widget) {
            $output = $item->out;
        } else {
            // Bad $item class, don't know how to use this for outputting!
            throw new ServerException('Bad item type for onStartProfileListItemActionElements');
        }

        $output->elementStart('li', 'entity_tag');
        $url = common_local_url('ostatustag', ['nickname' => $target->getNickname()]);
        $output->element('a',
                         [
                             'href'  => $url,
                             'class' => 'entity_remote_tag',
                         ],
                         // TRANS: Link text for a user to list an OStatus user.
                         _m('List'));
        $output->elementEnd('li');

        return true;
    }

    /**
     * Plugin Nodeinfo information
     *
     * @param array $protocols
     * @return bool hook true
     */
    public function onNodeInfoProtocols(array &$protocols)
    {
        $protocols[] = "ostatus";
        return true;
    }

    public function onPluginVersion(array &$versions): bool
    {
        $versions[] = array('name' => 'OStatus',
                            'version' => self::PLUGIN_VERSION,
                            'author' => 'Evan Prodromou, James Walker, Brion Vibber, Zach Copley',
                            'homepage' => GNUSOCIAL_ENGINE_REPO_URL . 'tree/master/plugins/OStatus',
                            // TRANS: Plugin description.
                            'rawdescription' => _m('Follow people across social networks that implement '.
                               '<a href="http://ostatus.org/">OStatus</a>.'));

        return true;
    }

    /**
     * Subscribe OS's profile class to the TFN module
     * 
     * @param array $federation
     * @return bool event hook return
     */
    public function onStartTFNCensus(array &$federation): bool
    {
        $federation[] = 'Ostatus_profile';
        return true;
    }

    /**
     * Utility function to check if the given URI is a canonical group profile
     * page, and if so return the ID number.
     *
     * @param string $url
     * @return mixed int or false
     */
    public static function localGroupFromUrl($url)
    {
        $group = User_group::getKV('uri', $url);
        if ($group instanceof User_group) {
            if ($group->isLocal()) {
                return $group->id;
            }
        } else {
            // To find local groups which haven't had their uri fields filled out...
            // If the domain has changed since a subscriber got the URI, it'll
            // be broken.
            $template = common_local_url('groupbyid', array('id' => '31337'));
            $template = preg_quote($template, '/');
            $template = str_replace('31337', '(\d+)', $template);
            if (preg_match("/$template/", $url, $matches)) {
                return intval($matches[1]);
            }
        }
        return false;
    }

    public function onStartProfileGetAtomFeed($profile, &$feed)
    {
        $oprofile = Ostatus_profile::getKV('profile_id', $profile->id);

        if (!$oprofile instanceof Ostatus_profile) {
            return true;
        }

        $feed = $oprofile->feeduri;
        return false;
    }

    public function onStartGetProfileFromURI($uri, &$profile)
    {
        // Don't want to do Web-based discovery on our own server,
        // so we check locally first. This duplicates the functionality
        // in the Profile class, since the plugin always runs before
        // that local lookup, but since we return false it won't run double.

        $user = User::getKV('uri', $uri);
        if ($user instanceof User) {
            $profile = $user->getProfile();
            return false;
        } else {
            $group = User_group::getKV('uri', $uri);
            if ($group instanceof User_group) {
                $profile = $group->getProfile();
                return false;
            }
        }

        // Now, check remotely
        try {
            $oprofile = Ostatus_profile::ensureProfileURI($uri);
            $profile = $oprofile->localProfile();
            return !($profile instanceof Profile);  // localProfile won't throw exception but can return null
        } catch (Exception $e) {
            return true; // It's not an OStatus profile as far as we know, continue event handling
        }
    }

    public function onEndWebFingerNoticeLinks(XML_XRD $xrd, Notice $target)
    {
        $salmon_url = null;
        $actor = $target->getProfile();
        if ($actor->isLocal()) {
            $profiletype = $this->profileTypeString($actor);
            $salmon_url = common_local_url("{$profiletype}salmon", array('id' => $actor->getID()));
        } else {
            try {
                $oprofile = Ostatus_profile::fromProfile($actor);
                $salmon_url = $oprofile->salmonuri;
            } catch (Exception $e) {
                // Even though it's not a local user, we couldn't get an Ostatus_profile?!
            }
        }
        // Ostatus_profile salmon URL may be empty
        if (!empty($salmon_url)) {
            $xrd->links[] = new XML_XRD_Element_Link(Salmon::REL_SALMON, $salmon_url);
        }
        return true;
    }

    public function onEndWebFingerProfileLinks(XML_XRD $xrd, Profile $target)
    {
        if ($target->getObjectType() === ActivityObject::PERSON) {
            $this->addWebFingerPersonLinks($xrd, $target);
        } elseif ($target->getObjectType() === ActivityObject::GROUP) {
            $xrd->links[] = new XML_XRD_Element_Link(
                Discovery::UPDATESFROM,
                common_local_url(
                    'ApiTimelineGroup',
                    ['id' => $target->getGroup()->getID(), 'format' => 'atom']
                ),
                'application/atom+xml'
            );
        }

        // Salmon
        $profiletype = $this->profileTypeString($target);
        $salmon_url = common_local_url("{$profiletype}salmon", array('id' => $target->id));

        $xrd->links[] = new XML_XRD_Element_Link(Salmon::REL_SALMON, $salmon_url);

        // XXX: these are deprecated, but StatusNet only looks for NS_REPLIES
        $xrd->links[] = new XML_XRD_Element_Link(Salmon::NS_REPLIES, $salmon_url);
        $xrd->links[] = new XML_XRD_Element_Link(Salmon::NS_MENTIONS, $salmon_url);

        return true;
    }

    protected function profileTypeString(Profile $target)
    {
        // This is just used to have a definitive string response to "USERsalmon" or "GROUPsalmon"
        switch ($target->getObjectType()) {
        case ActivityObject::PERSON:
            return 'user';
        case ActivityObject::GROUP:
            return 'group';
        default:
            throw new ServerException('Unknown profile type for WebFinger profile links');
        }
    }

    protected function addWebFingerPersonLinks(XML_XRD $xrd, Profile $target)
    {
        $xrd->links[] = new XML_XRD_Element_Link(
            Discovery::UPDATESFROM,
            common_local_url(
                'ApiTimelineUser',
                ['id' => $target->id, 'format' => 'atom']
            ),
            'application/atom+xml'
        );

        // Get this profile's keypair
        $magicsig = Magicsig::getKV('user_id', $target->id);
        if (!$magicsig instanceof Magicsig && $target->isLocal()) {
            $magicsig = Magicsig::generate($target->getUser());
        }

        if (!$magicsig instanceof Magicsig) {
            return false;   // value doesn't mean anything, just figured I'd indicate this function didn't do anything
        }
        if (Event::handle('StartAttachPubkeyToUserXRD', array($magicsig, $xrd, $target))) {
            $xrd->links[] = new XML_XRD_Element_Link(
                Magicsig::PUBLICKEYREL,
                'data:application/magic-public-key,' . $magicsig->toString()
            );
            // The following event handles plugins like Diaspora which add their own version of the Magicsig pubkey
            Event::handle('EndAttachPubkeyToUserXRD', array($magicsig, $xrd, $target));
        }
    }

    public function onGetLocalAttentions(Profile $actor, array $attention_uris, array &$mentions, array &$groups)
    {
        list($groups, $mentions) = Ostatus_profile::filterAttention($actor, $attention_uris);
    }

    // FIXME: Maybe this shouldn't be so authoritative that it breaks other remote profile lookups?
    public static function onCheckActivityAuthorship(Activity $activity, Profile &$profile)
    {
        try {
            $oprofile = Ostatus_profile::ensureProfileURL($profile->getUrl());
            $profile = $oprofile->checkAuthorship($activity);
        } catch (Exception $e) {
            common_log(LOG_ERR, 'Could not get a profile or check authorship ('.get_class($e).': "'.$e->getMessage().'") for activity ID: '.$activity->id);
            $profile = null;
            return false;
        }
        return true;
    }

    public function onProfileDeleteRelated($profile, &$related)
    {
        // Ostatus_profile has a 'profile_id' property, which will be used to find the object
        $related[] = 'Ostatus_profile';

        // Magicsig has a "user_id" column instead, so we have to delete it more manually:
        $magicsig = Magicsig::getKV('user_id', $profile->id);
        if ($magicsig instanceof Magicsig) {
            $magicsig->delete();
        }
        return true;
    }

    public function onSalmonSlap($endpoint_uri, MagicEnvelope $magic_env, Profile $target=null)
    {
        try {
            $envxml = $magic_env->toXML($target);
        } catch (Exception $e) {
            common_log(LOG_ERR, sprintf('Could not generate Magic Envelope XML for profile id=='.$target->getID().': '.$e->getMessage()));
            return false;
        }

        $headers = array('Content-Type: application/magic-envelope+xml');

        try {
            $client = new HTTPClient();
            $client->setBody($envxml);
            $response = $client->post($endpoint_uri, $headers);
        } catch (Exception $e) {
            common_log(LOG_ERR, "Salmon post to $endpoint_uri failed: " . $e->getMessage());
            return false;
        }
        if ($response->getStatus() === 422) {
            common_debug(sprintf('Salmon (from profile %d) endpoint %s returned status %s. We assume it is a Diaspora seed; will adapt and try again if that plugin is enabled!', $magic_env->getActor()->getID(), $endpoint_uri, $response->getStatus()));
            return true;
        }

        // The different kinds of accepted responses...
        // 200 OK means it's all ok
        // 201 Created is what Mastodon returns when it's ok
        // 202 Accepted is what we get from Diaspora, also good
        if (!in_array($response->getStatus(), array(200, 201, 202))) {
            common_log(LOG_ERR, sprintf(
                'Salmon (from profile %d) endpoint %s returned status %s: %s',
                $magic_env->getActor()->getID(),
                $endpoint_uri,
                $response->getStatus(),
                $response->getBody()
            ));
            return true;
        }

        // Since we completed the salmon slap, we discontinue the event
        return false;
    }

    public function onCronDaily()
    {
        try {
            $sub = FeedSub::renewalCheck();
        } catch (NoResultException $e) {
            common_log(LOG_INFO, "There were no expiring feeds.");
            return;
        }

        $qm = QueueManager::get();
        while ($sub->fetch()) {
            $item = array('feedsub_id' => $sub->id);
            $qm->enqueue($item, 'pushrenew');
        }
    }
    
    /**
     * Try to grab and store the remote profile by the given uri
     * 
     * @param string $uri
     * @param Profile &$profile
     * @return bool
     */
    public function onRemoteFollowPullProfile(string $uri, ?Profile &$profile): bool
    {
        $oprofile = pullRemoteProfile($uri);
        if ($oprofile instanceof Ostatus_profile) {

            // validation
            if ($oprofile->isGroup()) {
                $target = common_local_url('ostatusgroup', [], ['profile' => $uri]);
                common_redirect($target, 303);
            } else if ($oprofile->isPeopletag()) {
                $target = common_local_url('ostatuspeopletag', [], ['profile' => $uri]);
                common_redirect($target, 303);
            }

            $profile = $oprofile->localProfile();
        }

        return is_null($profile);
    }
}