<?php
/*
 * StatusNet - the distributed open-source microblogging tool
 * Copyright (C) 2010, StatusNet, Inc.
 *
 * 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 <http://www.gnu.org/licenses/>.
 */

/**
 * Prepare PuSH and Salmon distributions for an outgoing message.
 *
 * @package OStatusPlugin
 * @author Brion Vibber <brion@status.net>
 */
class OStatusQueueHandler extends QueueHandler
{
    // If we have more than this many subscribing sites on a single feed,
    // break up the PuSH distribution into smaller batches which will be
    // rolled into the queue progressively. This reduces disruption to
    // other, shorter activities being enqueued while we work.
    const MAX_UNBATCHED = 50;

    // Each batch (a 'hubprep' entry) will have this many items.
    // Selected to provide a balance between queue packet size
    // and number of batches that will end up getting processed.
    // For 20,000 target sites, 1000 should work acceptably.
    const BATCH_SIZE = 1000;

    function transport()
    {
        return 'ostatus';
    }

    function handle($notice)
    {
        assert($notice instanceof Notice);

        $this->notice = $notice;
        $this->user = User::staticGet($notice->profile_id);

        $this->pushUser();

        foreach ($notice->getGroups() as $group) {
            $oprofile = Ostatus_profile::staticGet('group_id', $group->id);
            if ($oprofile) {
                $this->pingReply($oprofile);
            } else {
                $this->pushGroup($group->id);
            }
        }

        foreach ($notice->getReplies() as $profile_id) {
            $oprofile = Ostatus_profile::staticGet('profile_id', $profile_id);
            if ($oprofile) {
                $this->pingReply($oprofile);
            }
        }

        if (!empty($this->notice->reply_to)) {
            $replyTo = Notice::staticGet('id', $this->notice->reply_to);
            if (!empty($replyTo)) {
                foreach($replyTo->getReplies() as $profile_id) {
                    $oprofile = Ostatus_profile::staticGet('profile_id', $profile_id);
                    if ($oprofile) {
                        $this->pingReply($oprofile);
                    }
                }
            }
        }
        return true;
    }

    function pushUser()
    {
        if ($this->user) {
            // For local posts, ping the PuSH hub to update their feed.
            // http://identi.ca/api/statuses/user_timeline/1.atom
            $feed = common_local_url('ApiTimelineUser',
                                     array('id' => $this->user->id,
                                           'format' => 'atom'));
            $this->pushFeed($feed, array($this, 'userFeedForNotice'));
        }
    }

    function pushGroup($group_id)
    {
        // For a local group, ping the PuSH hub to update its feed.
        // Updates may come from either a local or a remote user.
        $feed = common_local_url('ApiTimelineGroup',
                                 array('id' => $group_id,
                                       'format' => 'atom'));
        $this->pushFeed($feed, array($this, 'groupFeedForNotice'), $group_id);
    }

    function pingReply($oprofile)
    {
        if ($this->user) {
            // For local posts, send a Salmon ping to the mentioned
            // remote user or group.
            // @fixme as an optimization we can skip this if the
            // remote profile is subscribed to the author.
            $oprofile->notifyDeferred($this->notice, $this->user);
        }
    }

    /**
     * @param string $feed URI to the feed
     * @param callable $callback function to generate Atom feed update if needed
     *        any additional params are passed to the callback.
     */
    function pushFeed($feed, $callback)
    {
        $hub = common_config('ostatus', 'hub');
        if ($hub) {
            $this->pushFeedExternal($feed, $hub);
        }

        $sub = new HubSub();
        $sub->topic = $feed;
        if ($sub->find()) {
            $args = array_slice(func_get_args(), 2);
            $atom = call_user_func_array($callback, $args);
            $this->pushFeedInternal($atom, $sub);
        } else {
            common_log(LOG_INFO, "No PuSH subscribers for $feed");
        }
        return true;
    }

    /**
     * Ping external hub about this update.
     * The hub will pull the feed and check for new items later.
     * Not guaranteed safe in an environment with database replication.
     *
     * @param string $feed feed topic URI
     * @param string $hub PuSH hub URI
     * @fixme can consolidate pings for user & group posts
     */
    function pushFeedExternal($feed, $hub)
    {
        $client = new HTTPClient();
        try {
            $data = array('hub.mode' => 'publish',
                          'hub.url' => $feed);
            $response = $client->post($hub, array(), $data);
            if ($response->getStatus() == 204) {
                common_log(LOG_INFO, "PuSH ping to hub $hub for $feed ok");
                return true;
            } else {
                common_log(LOG_ERR, "PuSH ping to hub $hub for $feed failed with HTTP " .
                                    $response->getStatus() . ': ' .
                                    $response->getBody());
            }
        } catch (Exception $e) {
            common_log(LOG_ERR, "PuSH ping to hub $hub for $feed failed: " . $e->getMessage());
            return false;
        }
    }

    /**
     * Queue up direct feed update pushes to subscribers on our internal hub.
     * If there are a large number of subscriber sites, intermediate bulk
     * distribution triggers may be queued.
     *
     * @param string $atom update feed, containing only new/changed items
     * @param HubSub $sub open query of subscribers
     */
    function pushFeedInternal($atom, $sub)
    {
        common_log(LOG_INFO, "Preparing $sub->N PuSH distribution(s) for $sub->topic");
        $n = 0;
        $batch = array();
        while ($sub->fetch()) {
            $n++;
            if ($n < self::MAX_UNBATCHED) {
                $sub->distribute($atom);
            } else {
                $batch[] = $sub->callback;
                if (count($batch) >= self::BATCH_SIZE) {
                    $sub->bulkDistribute($atom, $batch);
                    $batch = array();
                }
            }
        }
        if (count($batch) >= 0) {
            $sub->bulkDistribute($atom, $batch);
        }
    }

    /**
     * Build a single-item version of the sending user's Atom feed.
     * @return string
     */
    function userFeedForNotice()
    {
        $atom = new AtomUserNoticeFeed($this->user);
        $atom->addEntryFromNotice($this->notice);
        $feed = $atom->getString();

        return $feed;
    }

    function groupFeedForNotice($group_id)
    {
        $group = User_group::staticGet('id', $group_id);

        $atom = new AtomGroupNoticeFeed($group);
        $atom->addEntryFromNotice($this->notice);
        $feed = $atom->getString();

        return $feed;
    }
}