<?php
/**
 * GNU social - a federating social network
 *
 * ActivityPubPlugin implementation for GNU Social
 *
 * LICENCE: 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/>.
 *
 * @category  Plugin
 * @package   GNUsocial
 * @author    Diogo Cordeiro <diogo@fc.up.pt>
 * @author    Daniel Supernault <danielsupernault@gmail.com>
 * @copyright 2018 Free Software Foundation http://fsf.org
 * @license   http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
 * @link      https://www.gnu.org/software/social/
 */
if (!defined('GNUSOCIAL')) {
    exit(1);
}

/**
 * ActivityPub Inbox Handler
 *
 * @category  Plugin
 * @package   GNUsocial
 * @author    Diogo Cordeiro <diogo@fc.up.pt>
 * @license   http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
 * @link      http://www.gnu.org/software/social/
 */
class Activitypub_inbox_handler
{
    private $activity;
    private $actor;
    private $object;

    /**
     * Create a Inbox Handler to receive something from someone.
     *
     * @author Diogo Cordeiro <diogo@fc.up.pt>
     * @param Array $activity Activity we are receiving
     */
    public function __construct($activity)
    {
        $this->activity = $activity;
        $this->object = $activity['object'];

        // Validate Activity
        $this->validate_activity();

        // Get Actor's Profile
        $this->actor = ActivityPub_explorer::get_profile_from_url($this->activity['actor']);

        // Handle the Activity
        $this->process();
    }

    /**
     * Validates if a given Activity is valid. Throws exception if not.
     *
     * @author Diogo Cordeiro <diogo@fc.upt.pt>
     * @throws Exception
     */
    private function validate_activity()
    {
        // Activity validation
        // Validate data
        if (!(isset($this->activity['type']))) {
            throw new Exception('Activity Validation Failed: Type was not specified.');
        }
        if (!isset($this->activity['actor'])) {
            throw new Exception('Activity Validation Failed: Actor was not specified.');
        }
        if (!isset($this->activity['object'])) {
            throw new Exception('Activity Validation Failed: Object was not specified.');
        }

        // Object validation
        switch ($this->activity['type']) {
            case 'Accept':
                Activitypub_accept::validate_object($this->object);
                break;
            case 'Create':
                Activitypub_create::validate_object($this->object);
                break;
            case 'Delete':
            case 'Follow':
            case 'Like':
            case 'Announce':
                if (!filter_var($this->object, FILTER_VALIDATE_URL)) {
                    throw new Exception("Object is not a valid Object URI for Activity.");
                }
                break;
            case 'Undo':
                Activitypub_undo::validate_object($this->object);
                break;
            default:
                throw new Exception('Unknown Activity Type.');
        }
    }

    /**
     * Sends the Activity to proper handler in order to be processed.
     *
     * @author Diogo Cordeiro <diogo@fc.upt.pt>
     */
    private function process()
    {
        switch ($this->activity['type']) {
            case 'Accept':
                $this->handle_accept($this->actor, $this->object);
                break;
            case 'Create':
                $this->handle_create($this->actor, $this->object);
                break;
            case 'Delete':
                $this->handle_delete($this->actor, $this->object);
                break;
            case 'Follow':
                $this->handle_follow($this->actor, $this->object);
                break;
            case 'Like':
                $this->handle_like($this->actor, $this->object);
                break;
            case 'Undo':
                $this->handle_undo($this->actor, $this->object);
                break;
            case 'Announce':
                $this->handle_announce($this->actor, $this->object);
                break;
        }
    }

    /**
     * Handles an Accept Activity received by our inbox.
     *
     * @author Diogo Cordeiro <diogo@fc.upt.pt>
     * @param Profile $actor Actor
     * @param Array $object Activity
     */
    private function handle_accept($actor, $object)
    {
        switch ($object['type']) {
            case 'Follow':
                $this->handle_accept_follow($actor, $object);
                break;
        }
    }

    /**
     * Handles an Accept Follow Activity received by our inbox.
     *
     * @author Diogo Cordeiro <diogo@fc.upt.pt>
     * @param Profile $actor Actor
     * @param Array $object Activity
     */
    private function handle_accept_follow($actor, $object)
    {
        // Get valid Object profile
        $object_profile = new Activitypub_explorer;
        $object_profile = $object_profile->lookup($object['object'])[0];

        $pending_list = new Activitypub_pending_follow_requests($actor->getID(), $object_profile->getID());
        $pending_list->remove();
    }

    /**
     * Handles a Create Activity received by our inbox.
     *
     * @author Diogo Cordeiro <diogo@fc.upt.pt>
     * @param Profile $actor Actor
     * @param Array $object Activity
     */
    private function handle_create($actor, $object)
    {
        switch ($object['type']) {
            case 'Note':
                Activitypub_notice::create_notice($object, $actor);
                break;
        }
    }

    /**
     * Handles a Delete Activity received by our inbox.
     *
     * @author Diogo Cordeiro <diogo@fc.upt.pt>
     * @param Profile $actor Actor
     * @param Array $object Activity
     */
    private function handle_delete($actor, $object)
    {
        $notice = ActivityPubPlugin::grab_notice_from_url($object['object']);
        $notice->deleteAs($actor);
    }

    /**
     * Handles a Follow Activity received by our inbox.
     *
     * @author Diogo Cordeiro <diogo@fc.upt.pt>
     * @param Profile $actor Actor
     * @param Array $object Activity
     */
    private function handle_follow($actor, $object)
    {
        Activitypub_follow::follow($actor, $object);
    }

    /**
     * Handles a Like Activity received by our inbox.
     *
     * @author Diogo Cordeiro <diogo@fc.upt.pt>
     * @param Profile $actor Actor
     * @param Array $object Activity
     */
    private function handle_like($actor, $object)
    {
        $notice = ActivityPubPlugin::grab_notice_from_url($object);
        Fave::addNew($actor, $notice);
    }

    /**
     * Handles a Undo Activity received by our inbox.
     *
     * @author Diogo Cordeiro <diogo@fc.upt.pt>
     * @param Profile $actor Actor
     * @param Array $object Activity
     */
    private function handle_undo($actor, $object)
    {
        switch ($object['type']) {
            case 'Follow':
                $this->handle_undo_follow($actor, $object['object']);
                break;
            case 'Like':
                $this->handle_undo_like($actor, $object['object']);
                break;
        }
    }

    /**
     * Handles a Undo Like Activity received by our inbox.
     *
     * @author Diogo Cordeiro <diogo@fc.upt.pt>
     * @param Profile $actor Actor
     * @param Array $object Activity
     */
    private function handle_undo_like($actor, $object)
    {
        $notice = ActivityPubPlugin::grab_notice_from_url($object);
        Fave::removeEntry($actor, $notice);
    }

    /**
     * Handles a Undo Follow Activity received by our inbox.
     *
     * @author Diogo Cordeiro <diogo@fc.upt.pt>
     * @param Profile $actor Actor
     * @param Array $object Activity
     */
    private function handle_undo_follow($actor, $object)
    {
        // Get Object profile
        $object_profile = new Activitypub_explorer;
        $object_profile = $object_profile->lookup($object)[0];

        if (Subscription::exists($actor, $object_profile)) {
            Subscription::cancel($actor, $object_profile);
        // You are no longer following this person.
        } else {
            // 409: You are not following this person already.
        }
    }

    /**
     * Handles a Announce Activity received by our inbox.
     *
     * @author Diogo Cordeiro <diogo@fc.upt.pt>
     * @param Profile $actor Actor
     * @param Array $object Activity
     */
    private function handle_announce($actor, $object)
    {
        $object_notice = ActivityPubPlugin::grab_notice_from_url($object);
        $object_notice->repeat($actor, 'ActivityPub');
    }
}