federator/php/federator/dio/followers.php

<?php
/**
 * SPDX-FileCopyrightText: 2024 Sascha Nitsch (grumpydeveloper) https://contentnation.net/@grumpydevelop
 * SPDX-License-Identifier: GPL-3.0-or-later
 *
 * @author Yannis Vogel (vogeldevelopment)
 **/

namespace Federator\DIO;

/**
 * IO functions related to followers
 */
class Followers
{
    /**
     * get followers of user
     *
     * @param \mysqli $dbh
     *          database handle
     * @param string $id
     *          user id
     * @param \Federator\Connector\Connector $connector
     *          connector to fetch use with
     * @param \Federator\Cache\Cache|null $cache
     *          optional caching service
     * @return \Federator\Data\FedUser[]
     */
    public static function getFollowersByUser($dbh, $id, $connector, $cache)
    {
        // ask cache
        if ($cache !== null) {
            $followers = $cache->getRemoteFollowersOfUser($id);
            if ($followers !== false) {
                return $followers;
            }
        }
        $followers = [];
        $sql = 'select source_user from follows where target_user = ?';
        $stmt = $dbh->prepare($sql);
        if ($stmt === false) {
            throw new \Federator\Exceptions\ServerError();
        }
        $stmt->bind_param("s", $id);
        $stmt->execute();
        $followerIds = [];
        $stmt->bind_result($sourceUser);
        while ($stmt->fetch()) {
            $followerIds[] = $sourceUser;
        }
        $stmt->close();
        foreach ($followerIds as $followerId) {
            $user = \Federator\DIO\FedUser::getUserByName(
                $dbh,
                $followerId,
                $cache,
            );
            if ($user !== false && $user->id !== null) {
                $followers[] = $user;
            }
        }

        if ($followers === []) {
            // ask connector for user-id
            $followers = $connector->getRemoteFollowersOfUser($id);
            if ($followers === false) {
                $followers = [];
            }
        }
        // save posts to DB
        if ($cache !== null) {
            $cache->saveRemoteFollowersOfUser($id, $followers);
        }
        return $followers;
    }
    /**
     * get following for user - who does the user follow
     *
     * @param \mysqli $dbh
     *          database handle
     * @param string $id
     *          user id
     * @param \Federator\Connector\Connector $connector
     *          connector to fetch use with
     * @param \Federator\Cache\Cache|null $cache
     *          optional caching service
     * @return \Federator\Data\FedUser[]
     */

    public static function getFollowingForUser($dbh, $id, $connector, $cache)
    {
        // ask cache
        if ($cache !== null) {
            $following = $cache->getRemoteFollowingForUser($id);
            if ($following !== false) {
                return $following;
            }
        }
        $following = [];
        $sql = 'select target_user from follows where source_user = ?';
        $stmt = $dbh->prepare($sql);
        if ($stmt === false) {
            throw new \Federator\Exceptions\ServerError();
        }
        $stmt->bind_param("s", $id);
        $stmt->execute();
        $followingIds = [];
        $stmt->bind_result($sourceUser);
        while ($stmt->fetch()) {
            $followingIds[] = $sourceUser;
        }
        $stmt->close();
        foreach ($followingIds as $followingId) {
            $user = \Federator\DIO\FedUser::getUserByName(
                $dbh,
                $followingId,
                $cache,
            );
            if ($user !== false && $user->id !== null) {
                $following[] = $user;
            }
        }

        if ($following === []) {
            // ask connector for user-id
            $following = $connector->getRemoteFollowingForUser($id);
            if ($following === false) {
                $following = [];
            }
        }
        // save posts to DB
        if ($cache !== null) {
            $cache->saveRemoteFollowingForUser($id, $following);
        }
        return $following;
    }

    /**
     * get followers of federated external user (e.g. mastodon)
     *
     * @param \mysqli $dbh
     *          database handle
     * @param \Federator\Connector\Connector $connector
     *          connector to fetch use with
     * @param \Federator\Cache\Cache|null $cache
     *          optional caching service
     * @param string $id
     *          user id
     * @return \Federator\Data\User[]
     */

    public static function getFollowersByFedUser($dbh, $connector, $cache, $id)
    {
        $followers = [];

        $sql = 'select source_user from follows where target_user = ?';
        $stmt = $dbh->prepare($sql);
        if ($stmt === false) {
            throw new \Federator\Exceptions\ServerError();
        }
        $stmt->bind_param("s", $id);
        $stmt->execute();
        $followerIds = [];
        $stmt->bind_result($sourceUser);
        while ($stmt->fetch()) {
            $followerIds[] = $sourceUser;
        }
        foreach ($followerIds as $followerId) {
            $user = \Federator\DIO\User::getUserByName(
                $dbh,
                $followerId,
                $connector,
                $cache
            );
            if ($user !== false && $user->id !== null) {
                $followers[] = $user;
            }
        }
        return $followers;
    }

    /**
     * send follow request
     *
     * @param \mysqli $dbh database handle
     * @param \Federator\Connector\Connector $connector connector to use
     * @param \Federator\Cache\Cache|null $cache optional caching service
     * @param string $_user source user
     * @param string $_targetUser target user id
     * @param string $host the host for generating the follow ID
     * @return string|false the generated follow ID on success, false on failure
     */
    public static function sendFollowRequest($dbh, $connector, $cache, $_user, $_targetUser, $host)
    {
        if ($dbh === false) {
            throw new \Federator\Exceptions\ServerError();
        }
        $user = \Federator\DIO\User::getUserByName(
            $dbh,
            $_user,
            $connector,
            $cache
        );
        if ($user === false || $user->id === null) {
            throw new \Federator\Exceptions\FileNotFound();
        }

        $fedUser = \Federator\DIO\FedUser::getUserByName(
            $dbh,
            $_targetUser,
            $cache
        );
        if ($fedUser === false || $fedUser->actorURL === null) {
            throw new \Federator\Exceptions\FileNotFound();
        }

        $sourceUser = $user->id;
        $idUrl = self::addFollow($dbh, $sourceUser, $fedUser->id, $host);
        if ($idUrl === false) {
            return false; // Failed to add follow
        }
        $followObj = new \Federator\Data\ActivityPub\Common\Follow();
        $sourceUserUrl = 'https://' . $host . '/' . $sourceUser;
        $followObj->setFObject($fedUser->actorURL);
        $followObj->setAActor($sourceUserUrl);
        $followObj->setID($idUrl);

        // Send the Follow activity
        $inboxUrl = $fedUser->inboxURL;

        $json = json_encode($followObj, JSON_UNESCAPED_SLASHES);

        if ($json === false) {
            self::removeFollow($dbh, $sourceUser, $fedUser->id);
            throw new \Exception('Failed to encode JSON: ' . json_last_error_msg());
        }
        $digest = 'SHA-256=' . base64_encode(hash('sha256', $json, true));
        $date = gmdate('D, d M Y H:i:s') . ' GMT';
        $parsed = parse_url($inboxUrl);
        if ($parsed === false) {
            self::removeFollow($dbh, $sourceUser, $fedUser->id);
            throw new \Exception('Failed to parse URL: ' . $inboxUrl);
        }

        if (!isset($parsed['host']) || !isset($parsed['path'])) {
            self::removeFollow($dbh, $sourceUser, $fedUser->id);
            throw new \Exception('Invalid inbox URL: missing host or path');
        }
        $extHost = $parsed['host'];
        $path = $parsed['path'];

        // Build the signature string
        $signatureString = "(request-target): post {$path}\n" .
            "host: {$extHost}\n" .
            "date: {$date}\n" .
            "digest: {$digest}";

        // Get rsa private key
        $privateKey = \Federator\DIO\User::getrsaprivate($dbh, $user->id); // OR from DB
        if ($privateKey === false) {
            self::removeFollow($dbh, $sourceUser, $fedUser->id);
            throw new \Exception('Failed to get private key');
        }
        $pkeyId = openssl_pkey_get_private($privateKey);

        if ($pkeyId === false) {
            self::removeFollow($dbh, $sourceUser, $fedUser->id);
            throw new \Exception('Invalid private key');
        }

        openssl_sign($signatureString, $signature, $pkeyId, OPENSSL_ALGO_SHA256);
        $signature_b64 = base64_encode($signature);

        // Build keyId (public key ID from your actor object)
        $keyId = 'https://' . $host . '/' . $user->id . '#main-key';

        $signatureHeader = 'keyId="' . $keyId . '",algorithm="rsa-sha256",headers="(request-target) host date digest",signature="' . $signature_b64 . '"';

        $ch = curl_init($inboxUrl);
        if ($ch === false) {
            self::removeFollow($dbh, $sourceUser, $fedUser->id);
            throw new \Exception('Failed to initialize cURL');
        }
        $headers = [
            'Host: ' . $extHost,
            'Date: ' . $date,
            'Digest: ' . $digest,
            'Content-Type: application/activity+json',
            'Signature: ' . $signatureHeader,
            'Accept: application/activity+json',
        ];

        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_POST, true);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $json);
        curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
        $response = curl_exec($ch);
        curl_close($ch);

        // Log the response for debugging if needed
        if ($response === false) {
            self::removeFollow($dbh, $sourceUser, $fedUser->id);
            throw new \Exception("Failed to send Follow activity: " . curl_error($ch));
        } else {
            $httpcode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
            if ($httpcode != 200 && $httpcode != 202) {
                self::removeFollow($dbh, $sourceUser, $fedUser->id);
                throw new \Exception("Unexpected HTTP code $httpcode: $response");
            }
        }
        return $idUrl;
    }

    /**
     * add follow
     *
     * @param \mysqli $dbh database handle
     * @param string $sourceUser source user id
     * @param string $targetUserId target user id
     * @param string $host the host for generating the follow ID
     * @return string|false the generated follow ID on success, false on failure
     */
    public static function addFollow($dbh, $sourceUser, $targetUserId, $host)
    {
        // Check if we already follow this user
        $sql = 'select id from follows where source_user = ? and target_user = ?';
        $stmt = $dbh->prepare($sql);
        if ($stmt === false) {
            throw new \Federator\Exceptions\ServerError();
        }
        $stmt->bind_param("ss", $sourceUser, $targetUserId);
        $foundId = 0;
        $ret = $stmt->bind_result($foundId);
        $stmt->execute();
        if ($ret) {
            $stmt->fetch();
        }
        $stmt->close();
        if ($foundId != 0) {
            return false; // Already following this user
        }

        // Generate a unique ID for the follow relationship
        do {
            $id = bin2hex(openssl_random_pseudo_bytes(16));
            $idurl = 'https://' . $host . '/' . $sourceUser . '/' . $id;

            // Check if the generated ID is unique
            $sql = 'select id from follows where id = ?';
            $stmt = $dbh->prepare($sql);
            if ($stmt === false) {
                throw new \Federator\Exceptions\ServerError();
            }
            $stmt->bind_param("s", $idurl);
            $foundId = 0;
            $ret = $stmt->bind_result($foundId);
            $stmt->execute();
            if ($ret) {
                $stmt->fetch();
            }
            $stmt->close();
        } while ($foundId > 0);

        // Add follow with created_at timestamp
        $sql = 'insert into follows (id, source_user, target_user, created_at) values (?, ?, ?, NOW())';
        $stmt = $dbh->prepare($sql);
        if ($stmt === false) {
            throw new \Federator\Exceptions\ServerError();
        }
        $stmt->bind_param("sss", $idurl, $sourceUser, $targetUserId);
        $stmt->execute();
        $stmt->close();
        return $idurl; // Return the generated follow ID
    }

    /**
     * remove follow
     *
     * @param \mysqli $dbh database handle
     * @param string $sourceUser source user id
     * @param string $targetUserId target user id
     * @return bool true on success
     */
    public static function removeFollow($dbh, $sourceUser, $targetUserId)
    {
        $sql = 'delete from follows where source_user = ? and target_user = ?';
        $stmt = $dbh->prepare($sql);
        if ($stmt === false) {
            throw new \Federator\Exceptions\ServerError();
        }
        $stmt->bind_param("ss", $sourceUser, $targetUserId);
        $stmt->execute();
        $affectedRows = $stmt->affected_rows;
        $stmt->close();
        return $affectedRows > 0;
    }
}