<?php
/**
 * @copyright Copyright (C) 2010-2023, the Friendica project
 *
 * @license GNU AGPL version 3 or any later version
 *
 * 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 <https://www.gnu.org/licenses/>.
 *
 */

namespace Friendica\Protocol\ActivityPub;

use Friendica\Content\Text\Markdown;
use Friendica\Core\Logger;
use Friendica\Core\Protocol;
use Friendica\DI;
use Friendica\Model\APContact;
use Friendica\Model\Contact;
use Friendica\Model\Group;
use Friendica\Model\Item;
use Friendica\Model\Post;
use Friendica\Model\User;
use Friendica\Protocol\Activity;
use Friendica\Util\JsonLD;

/**
 * ActivityPub Client To Server class
 */
class ClientToServer
{
	/**
	 * Process client to server activities
	 *
	 * @param array $activity
	 * @param integer $uid
	 * @param array $application
	 * @return array
	 */
	public static function processActivity(array $activity, int $uid, array $application): array
	{
		$ldactivity = JsonLD::compact($activity);
		if (empty($ldactivity)) {
			Logger::notice('Invalid activity', ['activity' => $activity, 'uid' => $uid]);
			return [];
		}

		$type = JsonLD::fetchElement($ldactivity, '@type');
		if (!$type) {
			Logger::notice('Empty type', ['activity' => $ldactivity, 'uid' => $uid]);
			return [];
		}

		$object_id   = JsonLD::fetchElement($ldactivity, 'as:object', '@id') ?? '';
		$object_type = Receiver::fetchObjectType($ldactivity, $object_id, $uid);
		if (!$object_type && !$object_id) {
			Logger::notice('Empty object type or id', ['activity' => $ldactivity, 'uid' => $uid]);
			return [];
		}

		Logger::debug('Processing activity', ['type' => $type, 'object_type' => $object_type, 'object_id' => $object_id, 'activity' => $ldactivity]);
		return self::routeActivities($type, $object_type, $object_id, $uid, $application, $ldactivity);
	}

	/**
	 * Route client to server activities
	 *
	 * @param string $type
	 * @param string $object_type
	 * @param string $object_id
	 * @param integer $uid
	 * @param array $application
	 * @param array $ldactivity
	 * @return array
	 */
	private static function routeActivities(string $type, string $object_type, string $object_id, int $uid, array $application, array $ldactivity): array
	{
		switch ($type) {
			case 'as:Create':
				if (in_array($object_type, Receiver::CONTENT_TYPES)) {
					return self::createContent($uid, $application, $ldactivity);
				}
				break;
			case 'as:Update':
				if (in_array($object_type, Receiver::CONTENT_TYPES) && !empty($object_id)) {
					return self::updateContent($uid, $object_id, $application, $ldactivity);
				}
				break;
			case 'as:Follow':
				if (in_array($object_type, Receiver::ACCOUNT_TYPES) && !empty($object_id)) {
					return self::followAccount($uid, $object_id, $ldactivity);
				}
				break;
		}
		return [];
	}

	/**
	 * Create a new post or comment
	 *
	 * @param integer $uid
	 * @param array $application
	 * @param array $ldactivity
	 * @return array
	 */
	private static function createContent(int $uid, array $application, array $ldactivity): array
	{
		$object_data = self::processObject($ldactivity['as:object']);
		$item = ClientToServer::processContent($object_data, $application, $uid);
		Logger::debug('Got data', ['item' => $item, 'object' => $object_data]);

		$id = Item::insert($item, true);
		if (!empty($id)) {
			$item = Post::selectFirst(['uri-id'], ['id' => $id]);
			if (!empty($item['uri-id'])) {
				return Transmitter::createActivityFromItem($id);
			}
		}
		return [];
	}

	/**
	 * Update an existing post or comment
	 *
	 * @param integer $uid
	 * @param string $object_id
	 * @param array $application
	 * @param array $ldactivity
	 * @return array
	 */
	private static function updateContent(int $uid, string $object_id, array $application, array $ldactivity):array
	{
		$id = Item::fetchByLink($object_id, $uid);
		$original_post = Post::selectFirst(['uri-id'], ['uid' => $uid, 'origin' => true, 'id' => $id]);
		if (empty($original_post)) {
			Logger::debug('Item not found or does not belong to the user', ['id' => $id, 'uid' => $uid, 'object_id' => $object_id, 'activity' => $ldactivity]);
			return [];
		}

		$object_data = self::processObject($ldactivity['as:object']);
		$item = ClientToServer::processContent($object_data, $application, $uid);
		if (empty($item['title']) && empty($item['body'])) {
			Logger::debug('Empty body and title', ['id' => $id, 'uid' => $uid, 'object_id' => $object_id, 'activity' => $ldactivity]);
			return [];
		}
		$post = ['title' => $item['title'], 'body' => $item['body']];
		Logger::debug('Got data', ['id' => $id, 'uid' => $uid, 'item' => $post]);
		Item::update($post, ['id' => $id]);
		Item::updateDisplayCache($original_post['uri-id']);

		return Transmitter::createActivityFromItem($id);
	}

	/**
	 * Follow a given account
	 * @todo Check the expected return value
	 *
	 * @param integer $uid
	 * @param string $object_id
	 * @param array $ldactivity
	 * @return array
	 */
	private static function followAccount(int $uid, string $object_id, array $ldactivity): array
	{
		return [];
	}

	/**
	 * Fetches data from the object part of an client to server activity
	 *
	 * @param array $object
	 *
	 * @return array Object data
	 */
	private static function processObject(array $object): array
	{
		$object_data = Receiver::getObjectDataFromActivity($object);

		$object_data['target']   = self::getTargets($object, $object_data['actor'] ?? '');
		$object_data['receiver'] = [];

		return $object_data;
	}

	/**
	 * Accumulate the targets and visibility of this post
	 *
	 * @param array $object
	 * @param string $actor
	 * @return array
	 */
	private static function getTargets(array $object, string $actor): array
	{
		$profile   = APContact::getByURL($actor);
		$followers = $profile['followers'];

		$targets = [];

		foreach (['as:to', 'as:cc', 'as:bto', 'as:bcc'] as $element) {
			switch ($element) {
				case 'as:to':
					$type = Receiver::TARGET_TO;
					break;
				case 'as:cc':
					$type = Receiver::TARGET_CC;
					break;
				case 'as:bto':
					$type = Receiver::TARGET_BTO;
					break;
				case 'as:bcc':
					$type = Receiver::TARGET_BCC;
					break;
			}
			$receiver_list = JsonLD::fetchElementArray($object, $element, '@id');
			if (empty($receiver_list)) {
				continue;
			}

			foreach ($receiver_list as $receiver) {
				if ($receiver == Receiver::PUBLIC_COLLECTION) {
					$targets[Receiver::TARGET_GLOBAL] = ($element == 'as:to');
					continue;
				}

				if ($receiver == $followers) {
					$targets[Receiver::TARGET_FOLLOWER] = true;
					continue;
				}
				$targets[$type][] = Contact::getIdForURL($receiver);
			}
		}
		return $targets;
	}

	/**
	 * Create an item array from client to server object data
	 *
	 * @param array $object_data
	 * @param array $application
	 * @param integer $uid
	 * @return array
	 */
	private static function processContent(array $object_data, array $application, int $uid): array
	{
		$owner = User::getOwnerDataById($uid);

		$item = [];

		$item['network']    = Protocol::DFRN;
		$item['uid']        = $uid;
		$item['verb']       = Activity::POST;
		$item['contact-id'] = $owner['id'];
		$item['author-id']  = $item['owner-id'] = Contact::getPublicIdByUserId($uid);
		$item['title']      = $object_data['name'];
		$item['body']       = Markdown::toBBCode($object_data['content']);
		$item['app']        = $application['name'] ?? 'API';

		if (!empty($object_data['target'][Receiver::TARGET_GLOBAL])) {
			$item['allow_cid'] = '';
			$item['allow_gid'] = '';
			$item['deny_cid']  = '';
			$item['deny_gid']  = '';
			$item['private']   = Item::PUBLIC;
		} elseif (isset($object_data['target'][Receiver::TARGET_GLOBAL])) {
			$item['allow_cid'] = '';
			$item['allow_gid'] = '';
			$item['deny_cid']  = '';
			$item['deny_gid']  = '';
			$item['private']   = Item::UNLISTED;
		} elseif (!empty($object_data['target'][Receiver::TARGET_FOLLOWER])) {
			$item['allow_cid'] = '';
			$item['allow_gid'] = '<' . Group::FOLLOWERS . '>';
			$item['deny_cid']  = '';
			$item['deny_gid']  = '';
			$item['private'] = Item::PRIVATE;
		} else {
			// @todo Set permissions via the $object_data['target'] array
			$item['allow_cid'] = '<' . $owner['id'] . '>';
			$item['allow_gid'] = '';
			$item['deny_cid']  = '';
			$item['deny_gid']  = '';
			$item['private'] = Item::PRIVATE;
		}

		if (!empty($object_data['summary'])) {
			$item['body'] = '[abstract=' . Protocol::ACTIVITYPUB . ']' . $object_data['summary'] . "[/abstract]\n" . $item['body'];
		}

		if ($object_data['reply-to-id']) {
			$item['thr-parent'] = $object_data['reply-to-id'];
			$item['gravity'] = Item::GRAVITY_COMMENT;
		} else {
			$item['gravity'] = Item::GRAVITY_PARENT;
		}

		$item = DI::contentItem()->expandTags($item);

		return $item;
	}
}