<?php

declare(strict_types = 1);

// {{{ License
// 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/>.
// }}}

/**
 * ActivityPub implementation for GNU social
 *
 * @package   GNUsocial
 * @category  ActivityPub
 *
 * @author    Diogo Peralta Cordeiro <@diogo.site>
 * @copyright 2021 Free Software Foundation, Inc http://www.fsf.org
 * @license   https://www.gnu.org/licenses/agpl.html GNU AGPL v3 or later
 */

namespace Plugin\ActivityPub\Util\Model;

use ActivityPhp\Type;
use ActivityPhp\Type\AbstractObject;
use App\Core\DB;
use App\Core\Event;
use App\Core\Log;
use App\Core\Router;
use App\Entity\Activity as GSActivity;
use App\Util\Common;
use App\Util\Exception\ClientException;
use App\Util\Exception\NoSuchActorException;
use App\Util\Exception\NotFoundException;
use App\Util\Exception\NotImplementedException;
use DateTimeInterface;
use Exception;
use InvalidArgumentException;
use Plugin\ActivityPub\ActivityPub;
use Plugin\ActivityPub\Entity\ActivitypubActivity;
use Plugin\ActivityPub\Util\Explorer;
use Plugin\ActivityPub\Util\Model;
use Symfony\Contracts\HttpClient\Exception\ClientExceptionInterface;
use Symfony\Contracts\HttpClient\Exception\RedirectionExceptionInterface;
use Symfony\Contracts\HttpClient\Exception\ServerExceptionInterface;
use Symfony\Contracts\HttpClient\Exception\TransportExceptionInterface;

/**
 * This class handles translation between JSON and ActivityPub Activities
 *
 * @copyright 2021 Free Software Foundation, Inc http://www.fsf.org
 * @license   https://www.gnu.org/licenses/agpl.html GNU AGPL v3 or later
 */
class Activity extends Model
{
    /**
     * Create an Entity from an ActivityStreams 2.0 JSON string
     * This will persist new GSActivities, GSObjects, and APActivity
     *
     * @throws ClientExceptionInterface
     * @throws NoSuchActorException
     * @throws NotImplementedException
     * @throws RedirectionExceptionInterface
     * @throws ServerExceptionInterface
     * @throws TransportExceptionInterface
     */
    public static function fromJson(string|AbstractObject $json, array $options = []): ActivitypubActivity
    {
        $type_activity = \is_string($json) ? self::jsonToType($json) : $json;

        // Ditch known activities
        if ($type_activity->has('id')) { // We can't dereference a transient activity
            $ap_act = DB::findOneBy(ActivitypubActivity::class, ['activity_uri' => $type_activity->get('id')], return_null: true);
            if (!\is_null($ap_act)) {
                return $ap_act;
            }
        }

        // Find Actor and Object
        $actor       = Explorer::getOneFromUri($type_activity->get('actor'));
        $type_object = $type_activity->get('object');
        if (\is_string($type_object)) {
            if (Common::isValidHttpUrl($type_object)) { // Retrieve it
                $type_object = ActivityPub::getObjectByUri($type_object, try_online: true);
            } else {
                $type_object = Type::fromJson($type_object);
            }
        }
        if ($type_object instanceof AbstractObject) { // Encapsulated, if we have it locally, prefer it
            // TODO: Test authority of activity over object
            try {
                $type_object = ActivityPub::getObjectByUri($type_object->get('id'), try_online: false);
            } catch (Exception $e) {
                // Use the encapsulated then
                Log::debug('Failed to find a local activity, will continue with encapsulated.', [$e]);
            }
        }

        if (($type_object instanceof Type\AbstractObject)) { // It's a new object apparently
            if (Event::handle('NewActivityPubActivity', [$actor, $type_activity, $type_object, &$ap_act]) !== Event::stop) {
                return self::handle_core_activity($actor, $type_activity, $type_object, $ap_act);
            }
        } else { // Object was already stored locally then
            if (Event::handle('NewActivityPubActivityWithObject', [$actor, $type_activity, $type_object, &$ap_act]) !== Event::stop) {
                return self::handle_core_activity($actor, $type_activity, $type_object, $ap_act);
            }
        }

        return $ap_act;
    }

    private static function handle_core_activity(\App\Entity\Actor $actor, AbstractObject $type_activity, mixed $type_object, ?ActivitypubActivity &$ap_act): ActivitypubActivity
    {
        $t = $type_activity->get('type');
        switch ($t) {
            case 'Create':
                ActivityCreate::handle_core_activity($actor, $type_activity, $type_object, $ap_act);
                break;
            case 'Follow':
                ActivityFollow::handle_core_activity($actor, $type_activity, $type_object, $ap_act);
                break;
            case 'Undo':
                $object_type = $type_object instanceof AbstractObject ? match ($type_object->get('type')) {
                    'Note' => \App\Entity\Note::class,
                    // no break
                    default => throw new NotImplementedException('Unsupported Undo of Object Activity.'),
                } : $type_object::class;

                switch ($object_type) {
                    case GSActivity::class:
                        switch ($type_object->getVerb()) {
                            case 'subscribe':
                                ActivityFollow::handle_undo($actor, $type_activity, $type_object, $ap_act);
                                break;
                        }
                        break;
                }
                break;
            case 'Announce':
                ActivityAnnounce::handle_core_activity($actor, $type_activity, $type_object, $ap_act);
                break;
            default:
                Log::debug('ActivityPub: nothing to handle for type ' . $t);
        }
        return $ap_act;
    }

    /**
     * Get a JSON
     *
     * @throws ClientException
     */
    public static function toType(mixed $object): AbstractObject
    {
        if ($object::class !== GSActivity::class) {
            throw new InvalidArgumentException('First argument type must be an Activity.');
        }

        $gs_verb_to_activity_streams_two_verb = null;
        if (Event::handle('GSVerbToActivityStreamsTwoActivityType', [($verb = $object->getVerb()), &$gs_verb_to_activity_streams_two_verb]) === Event::next) {
            $gs_verb_to_activity_streams_two_verb = match ($verb) {
                'undo'      => 'Undo',
                'create'    => 'Create',
                'subscribe' => 'Follow',
                default     => throw new ClientException('Invalid verb'),
            };
        }

        $attr = [
            'type'       => $gs_verb_to_activity_streams_two_verb,
            '@context'   => ActivityPub::$activity_streams_two_context,
            'instrument' => Type::create('Service', [
                'name' => 'GNU social ActivityPub Plugin - v' . ActivityPub::version(),
                'url'  => GNUSOCIAL_ENGINE_URL,
            ]),
            'id'        => Router::url('activity_view', ['id' => $object->getId()], Router::ABSOLUTE_URL),
            'published' => $object->getCreated()->format(DateTimeInterface::RFC3339),
            'actor'     => $object->getActor()->getUri(Router::ABSOLUTE_URL),
        ];

        $attr['to'] = ['https://www.w3.org/ns/activitystreams#Public'];
        $attr['cc'] = [];
        foreach ($object->getAttentionTargets() as $target) {
            $attr['cc'][] = $target->getUri();
        }

        // Get object or Tombstone
        try {
            $child          = $object->getObject(); // Throws NotFoundException
            $prefer_embed   = ['Create', 'Undo'];
            $attr['object'] = \in_array($attr['type'], $prefer_embed) ? self::jsonToType(Model::toJson($child)) : ActivityPub::getUriByObject($child);
        } catch (NotFoundException) {
            // It seems this object was deleted, refer to it as a Tombstone
            $uri = match ($object->getObjectType()) {
                'note'  => Router::url('note_view', ['id' => $object->getObjectId()], type: Router::ABSOLUTE_URL),
                'actor' => Router::url('actor_view_id', ['id' => $object->getObjectId()], type: Router::ABSOLUTE_URL),
                default => throw new NotImplementedException(),
            };
            $attr['object'] = Type::create('Tombstone', ['id' => $uri]);
        }

        if (!\is_string($attr['object'])) {
            $attr['@context'] = $attr['object']->get('@context');
            $attr['object']->set('@context', null);
        }
        $type = self::jsonToType($attr);
        Event::handle('ActivityPubAddActivityStreamsTwoData', [$type->get('type'), &$type]);
        return $type;
    }
}