<?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 2018-2019, 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;

use ActivityPhp\Type;
use ActivityPhp\Type\AbstractObject;
use App\Core\DB;
use App\Core\Event;
use App\Core\HTTPClient;
use function App\Core\I18n\_m;
use App\Core\Log;
use App\Core\Modules\Plugin;
use App\Core\Queue;
use App\Core\Router;
use App\Entity\Activity;
use App\Entity\Actor;
use App\Entity\Note;
use App\Util\Common;
use App\Util\Exception\BugFoundException;
use Component\Collection\Util\Controller\OrderedCollection;
use Component\FreeNetwork\Entity\FreeNetworkActorProtocol;
use Component\FreeNetwork\Util\Discovery;
use EventResult;
use Exception;
use InvalidArgumentException;
use Plugin\ActivityPub\Controller\Inbox;
use Plugin\ActivityPub\Controller\Outbox;
use Plugin\ActivityPub\Entity\ActivitypubActivity;
use Plugin\ActivityPub\Entity\ActivitypubActor;
use Plugin\ActivityPub\Entity\ActivitypubObject;
use Plugin\ActivityPub\Util\Explorer;
use Plugin\ActivityPub\Util\HTTPSignature;
use Plugin\ActivityPub\Util\Model;
use Plugin\ActivityPub\Util\OrderedCollectionController;
use Plugin\ActivityPub\Util\Response\ActivityResponse;
use Plugin\ActivityPub\Util\Response\ActorResponse;
use Plugin\ActivityPub\Util\Response\NoteResponse;
use Plugin\ActivityPub\Util\TypeResponse;
use Plugin\ActivityPub\Util\Validator\contentLangModelValidator;
use Plugin\ActivityPub\Util\Validator\manuallyApprovesFollowersModelValidator;
use Symfony\Component\HttpFoundation\JsonResponse;
use Symfony\Contracts\HttpClient\Exception\ClientExceptionInterface;
use Symfony\Contracts\HttpClient\Exception\RedirectionExceptionInterface;
use Symfony\Contracts\HttpClient\Exception\ServerExceptionInterface;
use Symfony\Contracts\HttpClient\Exception\TransportExceptionInterface;
use Symfony\Contracts\HttpClient\ResponseInterface;
use XML_XRD;
use XML_XRD_Element_Link;

/**
 * Adds ActivityPub support to GNU social when enabled
 *
 * @copyright 2018-2019, 2021 Free Software Foundation, Inc http://www.fsf.org
 * @license   https://www.gnu.org/licenses/agpl.html GNU AGPL v3 or later
 */
class ActivityPub extends Plugin
{
    // ActivityStreams 2.0 Accept Headers
    public static array $accept_headers = [
        'application/ld+json; profile="https://www.w3.org/ns/activitystreams"',
        'application/activity+json',
        'application/json',
        'application/ld+json',
    ];

    // So that this isn't hardcoded everywhere
    public const PUBLIC_TO = [
        'https://www.w3.org/ns/activitystreams#Public',
        'Public',
        'as:Public',
    ];
    public const HTTP_CLIENT_HEADERS = [
        'Accept'     => 'application/ld+json; profile="https://www.w3.org/ns/activitystreams"',
        'User-Agent' => 'GNUsocialBot ' . GNUSOCIAL_VERSION . ' - ' . GNUSOCIAL_PROJECT_URL,
    ];

    public static function version(): string
    {
        return '3.0.0';
    }

    public static array $activity_streams_two_context = [
        'https://www.w3.org/ns/activitystreams',
        'https://w3id.org/security/v1',
        ['gs'          => 'https://www.gnu.org/software/social/ns#'],
        ['litepub'     => 'http://litepub.social/ns#'],
        ['chatMessage' => 'litepub:chatMessage'],
        [
            'inConversation' => [
                '@id'   => 'gs:inConversation',
                '@type' => '@id',
            ],
        ],
    ];

    public function onInitializePlugin(): EventResult
    {
        Event::handle('ActivityStreamsTwoContext', [&self::$activity_streams_two_context]);
        self::$activity_streams_two_context = array_unique(self::$activity_streams_two_context, \SORT_REGULAR);
        return Event::next;
    }

    public function onQueueActivitypubInbox(ActivitypubActor $ap_actor, Actor $actor, string|AbstractObject $type): EventResult
    {
        // TODO: Check if Actor has authority over payload

        // Store Activity
        $ap_act = Model\Activity::fromJson($type, ['source' => 'ActivityPub']);
        FreeNetworkActorProtocol::protocolSucceeded(
            'activitypub',
            $ap_actor->getActorId(),
            Discovery::normalize($actor->getNickname() . '@' . parse_url($ap_actor->getInboxUri(), \PHP_URL_HOST)),
        );

        DB::flush();
        if (($att_targets = $ap_act->getAttentionTargets()) !== []) {
            if (Event::handle('ActivityPubNewNotification', [$actor, ($act = $ap_act->getActivity()), $att_targets, _m('{actor_id} triggered a notification via ActivityPub.', ['{actor_id}' => $actor->getId()])]) === Event::next) {
                Event::handle('NewNotification', [$actor, $act, $att_targets, _m('{actor_id} triggered a notification via ActivityPub.', ['{nickname}' => $actor->getId()])]);
            }
        }

        return Event::stop;
    }

    /**
     * This code executes when GNU social creates the page routing, and we hook
     * on this event to add our Inbox and Outbox handler for ActivityPub.
     *
     * @param Router $r the router that was initialized
     */
    public function onAddRoute(Router $r): EventResult
    {
        $r->connect(
            'activitypub_inbox',
            '/inbox.json',
            Inbox::class,
            options: ['format' => self::$accept_headers[0]],
        );
        $r->connect(
            'activitypub_actor_inbox',
            '/actor/{gsactor_id<\d+>}/inbox.json',
            [Inbox::class, 'handle'],
            options: ['format' => self::$accept_headers[0]],
        );
        $r->connect(
            'activitypub_actor_outbox',
            '/actor/{gsactor_id<\d+>}/outbox.json',
            [Outbox::class, 'viewOutboxByActorId'],
            options: ['accept' => self::$accept_headers, 'format' => self::$accept_headers[0]],
        );
        return Event::next;
    }

    /**
     * Fill Actor->getUrl() calls with correct URL coming from ActivityPub
     */
    public function onStartGetActorUri(Actor $actor, int $type, ?string &$url): EventResult
    {
        if (
            // Is remote?
            !$actor->getIsLocal()
            // Is in ActivityPub?
            && !\is_null($ap_actor = DB::findOneBy(ActivitypubActor::class, ['actor_id' => $actor->getId()], return_null: true))
            // We can only provide a full URL (anything else wouldn't make sense)
            && $type === Router::ABSOLUTE_URL
        ) {
            $url = $ap_actor->getUri();
            return Event::stop;
        }

        return Event::next;
    }

    /**
     * Fill Actor->canAdmin() for Actors that came from ActivityPub
     */
    public function onFreeNetworkActorCanAdmin(Actor $actor, Actor $other, bool &$canAdmin): EventResult
    {
        // Are both in AP?
        if (
            !\is_null($ap_actor = DB::findOneBy(ActivitypubActor::class, ['actor_id' => $actor->getId()], return_null: true))
            && !\is_null($ap_other = DB::findOneBy(ActivitypubActor::class, ['actor_id' => $other->getId()], return_null: true))
        ) {
            // Are they both in the same server?
            $canAdmin = parse_url($ap_actor->getUri(), \PHP_URL_HOST) === parse_url($ap_other->getUri(), \PHP_URL_HOST);
            return Event::stop;
        }

        return Event::next;
    }

    /**
     * Overload core endpoints to make resources available in ActivityStreams 2.0
     *
     * @throws Exception
     */
    public function onControllerResponseInFormat(string $route, array $accept_header, array $vars, ?TypeResponse &$response = null): EventResult
    {
        if (\count(array_intersect(self::$accept_headers, $accept_header)) === 0) {
            return Event::next;
        }
        switch ($route) {
            case 'actor_view_id':
            case 'person_actor_view_id':
            case 'person_actor_view_nickname':
            case 'group_actor_view_id':
            case 'group_actor_view_nickname':
            case 'bot_actor_view_id':
            case 'bot_actor_view_nickname':
                $response = ActorResponse::handle($vars['actor']);
                break;
            case 'activity_view':
                $response = ActivityResponse::handle($vars['activity']);
                break;
            case 'note_view':
                $response = NoteResponse::handle($vars['note']);
                break;
            case 'activitypub_actor_outbox':
                $response = new TypeResponse($vars['type']);
                break;
            default:
                if (Event::handle('ActivityPubActivityStreamsTwoResponse', [$route, $vars, &$response]) !== Event::stop) {
                    if (is_subclass_of($vars['controller'][0], OrderedCollection::class)) {
                        $response = new TypeResponse(OrderedCollectionController::fromControllerVars($vars)['type']);
                    } else {
                        $response = new JsonResponse(['error' => 'Unknown Object cannot be represented.']);
                    }
                }
        }
        return Event::stop;
    }

    /**
     * Add ActivityStreams 2 Extensions
     */
    public function onActivityPubValidateActivityStreamsTwoData(string $type_name, array &$validators): EventResult
    {
        switch ($type_name) {
            case 'Person':
                $validators['manuallyApprovesFollowers'] = manuallyApprovesFollowersModelValidator::class;
                break;
            case 'Note':
                $validators['contentLang'] = contentLangModelValidator::class;
                break;
        }
        return Event::next;
    }

    // FreeNetworkComponent Events

    /**
     * Let FreeNetwork Component know we exist and which class to use to call the freeNetworkDistribute method
     */
    public function onAddFreeNetworkProtocol(array &$protocols): EventResult
    {
        if (!\in_array('\Plugin\ActivityPub\ActivityPub', $protocols)) {
            $protocols[] = '\Plugin\ActivityPub\ActivityPub';
        }
        return Event::next;
    }

    /**
     * The FreeNetwork component will call this function to pull ActivityPub objects by URI
     *
     * @param string $uri Query
     *
     * @return bool true if imported, false otherwise
     */
    public static function freeNetworkGrabRemote(string $uri): bool
    {
        if (Common::isValidHttpUrl($uri)) {
            try {
                $object = self::getObjectByUri($uri);
                if (!\is_null($object)) {
                    if ($object instanceof Type\AbstractObject) {
                        if (\in_array($object->get('type'), array_keys(Model\Actor::$_as2_actor_type_to_gs_actor_type))) {
                            DB::wrapInTransaction(fn () => Model\Actor::fromJson($object));
                        } else {
                            DB::wrapInTransaction(fn () => Model\Activity::fromJson($object));
                        }
                    }
                    return true;
                }
            } catch (Exception|Throwable) {
                // May be invalid input, we can safely ignore in this case
            }
        }
        return false;
    }

    public function onQueueActivitypubPostman(
        Actor $sender,
        Activity $activity,
        string $inbox,
        array $to_actors,
        array &$retry_args,
    ): EventResult {
        try {
            $data = Model::toType($activity);
            if ($sender->isGroup()) { // When the sender is a group,
                if ($activity->getVerb() === 'subscribe') {
                    // Regular postman happens
                } elseif ($activity->getVerb() === 'undo' && $data->get('object')->get('type') === 'Follow') {
                    // Regular postman happens
                } else {
                    // For every other activity sent by a Group, we have to wrap it in a transient Announce activity
                    $data = Type::create('Announce', [
                        '@context' => 'https:\/\/www.w3.org\/ns\/activitystreams',
                        'actor'    => $sender->getUri(type: Router::ABSOLUTE_URL),
                        'object'   => $data,
                    ]);
                }
            }
            $res = self::postman($sender, $data->toJson(), $inbox);

            // accumulate errors for later use, if needed
            $status_code = $res->getStatusCode();
            if (!($status_code === 200 || $status_code === 202 || $status_code === 409)) {
                $res_body = json_decode($res->getContent(), true);
                $retry_args['reason'] ??= [];
                $retry_args['reason'][] = $res_body['error'] ?? 'An unknown error occurred.';
                return Event::next;
            } else {
                foreach ($to_actors as $actor) {
                    if ($actor->isPerson()) {
                        FreeNetworkActorProtocol::protocolSucceeded(
                            'activitypub',
                            $actor,
                            Discovery::normalize($actor->getNickname() . '@' . parse_url($inbox, \PHP_URL_HOST)),
                        );
                    }
                }
            }
            return Event::stop;
        } catch (Exception $e) {
            Log::error('ActivityPub @ freeNetworkDistribute: ' . $e->getMessage(), [$e]);
            $retry_args['reason'] ??= [];
            $retry_args['reason'][] = "Got an exception: {$e->getMessage()}";
            $retry_args['exception'] ??= [];
            $retry_args['exception'][] = $e;
            return Event::next;
        }
    }

    /**
     * The FreeNetwork component will call this function to distribute this instance's activities
     *
     * @throws ClientExceptionInterface
     * @throws RedirectionExceptionInterface
     * @throws ServerExceptionInterface
     * @throws TransportExceptionInterface
     */
    public static function freeNetworkDistribute(Actor $sender, Activity $activity, array $targets, ?string $reason = null): void
    {
        $to_addr = [];
        foreach ($targets as $actor) {
            if (FreeNetworkActorProtocol::canIActor('activitypub', $actor->getId())) {
                // Sometimes FreeNetwork can allow us to actor even though we don't have an internal representation of
                // the actor, that could for example mean that OStatus handled this actor while we were deactivated
                // On next interaction this should be resolved, for now continue
                if (\is_null($ap_target = DB::findOneBy(ActivitypubActor::class, ['actor_id' => $actor->getId()], return_null: true))) {
                    Log::info('FreeNetwork wrongly told ActivityPub that it can handle actor id: ' . $actor->getId() . ' you might want to keep an eye on it.');
                    continue;
                }
                $to_addr[$ap_target->getInboxSharedUri() ?? $ap_target->getInboxUri()][] = $actor;
            } else {
                continue;
            }
        }

        foreach ($to_addr as $inbox => $to_actors) {
            Queue::enqueue(
                payload: [$sender, $activity, $inbox, $to_actors],
                queue: 'ActivitypubPostman',
                priority: false,
            );
        }
    }

    /**
     * Internal tool to sign and send activities out
     *
     * @throws Exception
     */
    private static function postman(Actor $sender, string $json_activity, string $inbox, string $method = 'post'): ResponseInterface
    {
        Log::debug('ActivityPub Postman: Delivering ' . $json_activity . ' to ' . $inbox);

        $headers = HTTPSignature::sign($sender, $inbox, $json_activity);
        Log::debug('ActivityPub Postman: Delivery headers were: ' . print_r($headers, true));

        $response = HTTPClient::$method($inbox, ['headers' => $headers, 'body' => $json_activity]);
        Log::debug('ActivityPub Postman: Delivery result with status code ' . $response->getStatusCode() . ': ' . $response->getContent());
        return $response;
    }

    // WebFinger Events

    /**
     * Add activity+json mimetype to WebFinger
     */
    public function onEndWebFingerProfileLinks(XML_XRD $xrd, Actor $object): EventResult
    {
        if ($object->isPerson()) {
            $link = new XML_XRD_Element_Link(
                rel: 'self',
                href: $object->getUri(Router::ABSOLUTE_URL),//Router::url('actor_view_id', ['id' => $object->getId()], Router::ABSOLUTE_URL),
                type: 'application/activity+json',
            );
            $xrd->links[] = clone $link;
        }
        return Event::next;
    }

    /**
     * When FreeNetwork component asks us to help with identifying Actors from XRDs
     */
    public function onFreeNetworkFoundXrd(XML_XRD $xrd, ?Actor &$actor = null): EventResult
    {
        $addr = null;
        foreach ($xrd->aliases as $alias) {
            if (Discovery::isAcct($alias)) {
                $addr = Discovery::normalize($alias);
            }
        }
        if (\is_null($addr)) {
            return Event::next;
        } else {
            if (!FreeNetworkActorProtocol::canIAddr('activitypub', $addr)) {
                return Event::next;
            }
        }
        try {
            $ap_actor = ActivitypubActor::fromXrd($addr, $xrd);
            $actor    = Actor::getById($ap_actor->getActorId());
            FreeNetworkActorProtocol::protocolSucceeded('activitypub', $actor, $addr);
            return Event::stop;
        } catch (Exception $e) {
            Log::error('ActivityPub Actor from URL Mention check failed: ' . $e->getMessage());
            return Event::next;
        }
    }

    // Discovery Events

    /**
     * When FreeNetwork component asks us to help with identifying Actors from URIs
     */
    public function onFreeNetworkFindMentions(string $target, ?Actor &$actor = null): EventResult
    {
        try {
            if (FreeNetworkActorProtocol::canIAddr('activitypub', $addr = Discovery::normalize($target))) {
                $ap_actor = DB::wrapInTransaction(fn () => ActivitypubActor::getByAddr($addr));
                $actor    = Actor::getById($ap_actor->getActorId());
                FreeNetworkActorProtocol::protocolSucceeded('activitypub', $actor->getId(), $addr);
                return Event::stop;
            } else {
                return Event::next;
            }
        } catch (Exception $e) {
            Log::error('ActivityPub WebFinger Mention check failed.', [$e]);
            return Event::next;
        }
    }

    /**
     * @return string got from URI
     */
    public static function getUriByObject(mixed $object): string
    {
        switch ($object::class) {
            case Note::class:
                if ($object->getIsLocal()) {
                    return $object->getUrl();
                } else {
                    // Try known remote objects
                    $known_object = DB::findOneBy(ActivitypubObject::class, ['object_type' => 'note', 'object_id' => $object->getId()], return_null: true);
                    if ($known_object instanceof ActivitypubObject) {
                        return $known_object->getObjectUri();
                    } else {
                        throw new BugFoundException('ActivityPub cannot generate an URI for a stored note.', [$object, $known_object]);
                    }
                }
                break;
            case Actor::class:
                return $object->getUri();
                break;
            case Activity::class:
                // Try known remote activities
                $known_activity = DB::findOneBy(ActivitypubActivity::class, ['activity_id' => $object->getId()], return_null: true);
                if (!\is_null($known_activity)) {
                    return $known_activity->getActivityUri();
                } else {
                    return Router::url('activity_view', ['id' => $object->getId()], Router::ABSOLUTE_URL);
                }
                break;
            default:
                throw new InvalidArgumentException('ActivityPub::getUriByObject found a limitation with: ' . var_export($object, true));
        }
    }

    /**
     * Get a Note from ActivityPub URI, if it doesn't exist, attempt to fetch it
     * This should only be necessary internally.
     *
     * @throws ClientExceptionInterface
     * @throws RedirectionExceptionInterface
     * @throws ServerExceptionInterface
     * @throws TransportExceptionInterface
     *
     * @return null|Actor|mixed|Note got from URI
     */
    public static function getObjectByUri(string $resource, bool $try_online = true): mixed
    {
        // Try known object
        $known_object = DB::findOneBy(ActivitypubObject::class, ['object_uri' => $resource], return_null: true);
        if (!\is_null($known_object)) {
            return $known_object->getObject();
        }

        // Try known activity
        $known_activity = DB::findOneBy(ActivitypubActivity::class, ['activity_uri' => $resource], return_null: true);
        if (!\is_null($known_activity)) {
            return $known_activity->getActivity();
        }

        // Try Actor
        try {
            return Explorer::getOneFromUri($resource, try_online: false);
        } catch (\Exception) {
            // Ignore, this is brute forcing, it's okay not to find
        }

        // Is it a HTTP URL?
        if (Common::isValidHttpUrl($resource)) {
            $resource_parts = parse_url($resource);
            // If it is local
            if ($resource_parts['host'] === Common::config('site', 'server')) {
                // Try Local Note
                $local_note = DB::findOneBy(Note::class, ['url' => $resource], return_null: true);
                if (!\is_null($local_note)) {
                    return $local_note;
                }

                // Try local Activity
                try {
                    $match          = Router::match($resource_parts['path']);
                    $local_activity = DB::findOneBy(Activity::class, ['id' => $match['id']], return_null: true);
                    if (!\is_null($local_activity)) {
                        return $local_activity;
                    } else {
                        throw new InvalidArgumentException('Tried to retrieve a non-existent local activity.');
                    }
                } catch (\Exception) {
                    // Ignore, this is brute forcing, it's okay not to find
                }

                throw new BugFoundException('ActivityPub failed to retrieve local resource: "' . $resource . '". This is a big issue.');
            } else {
                // Then it's remote
                if (!$try_online) {
                    throw new Exception("Remote resource {$resource} not found without online resources.");
                }

                $response = HTTPClient::get($resource, ['headers' => self::HTTP_CLIENT_HEADERS]);
                // If it was deleted
                if ($response->getStatusCode() == 410) {
                    //$obj = Type::create('Tombstone', ['id' => $resource]);
                    return null;
                } elseif (!HTTPClient::statusCodeIsOkay($response)) { // If it is unavailable
                    throw new Exception('Non Ok Status Code for given Object id.');
                } else {
                    return Model::jsonToType($response->getContent());
                }
            }
        }

        return null;
    }
}