<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

namespace auth_jwt;

require_once(__DIR__ . '/../vendor/autoload.php');

use \Firebase\JWT\JWT;

/**
 * Key manager class.
 *
 * @package    auth_jwt
 * @copyright  2016 Dmitrii Metelkin (dmitriim@catalyst-au.net), 2024 Kumi Systems e.U.
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class core_jwt_manager
{

    /**
     * Default life time of the user key in seconds.
     */
    const DEFAULT_KEY_LIFE_TIME_IN_SECONDS = 60;

    /**
     * Config object.
     *
     * @var \stdClass
     */
    protected $config;

    /**
     * Constructor.
     *
     * @param \stdClass $config
     */
    public function __construct(\stdClass $config)
    {
        $this->config = $config;
    }

    /**
     * Create a user key.
     *
     * @param int $userid User ID.
     * @param null|array $allowedips A list of allowed ips for this key.
     *
     * @return string Generated key.
     */
    public function create_key($userid, $allowedips = null)
    {
        if (isset($this->config->keylifetime) && (int)$this->config->keylifetime > 0) {
            $validuntil = time() + $this->config->keylifetime;
        } else {
            $validuntil = time() + self::DEFAULT_KEY_LIFE_TIME_IN_SECONDS;
        }

        $payload = [
            'userid' => $userid,
            'exp' => $validuntil
        ];

        if ($allowedips) {
            $payload['allowedips'] = $allowedips;
        }

        $secret = $this->config->jwtsecret;

        return JWT::encode($payload, $secret);
    }

    /**
     * Validates key and returns key data object if valid.
     *
     * @param string $keyvalue User key value.
     *
     * @return object Key object including userid property.
     *
     * @throws \moodle_exception If provided key is not valid.
     */
    public function validate_key($keyvalue)
    {
        $secret = $this->config->jwtsecret;

        try {
            $decoded = JWT::decode($keyvalue, $secret, ['HS256']);
        } catch (\Exception $e) {
            throw new \moodle_exception('invalidkey');
        }

        if (!empty($decoded->exp) && $decoded->exp < time()) {
            throw new \moodle_exception('expiredkey');
        }

        $this->validate_ip_address($decoded);

        return $decoded;
    }

    /**
     * Validates key IP address and returns true if valid.
     *
     * @param object $key Key object including userid property.
     *
     * @throws \moodle_exception If provided key is not valid.
     */
    protected function validate_ip_address($key)
    {
        if (empty($key->allowedips)) {
            return true;
        }

        $remoteaddr = getremoteaddr(null);

        if (empty($remoteaddr)) {
            throw new \moodle_exception('noip', 'auth_jwt');
        }

        foreach ($key->allowedips as $allowedip) {
            if (address_in_subnet($remoteaddr, $allowedip)) {
                return true;
            }
        }

        throw new \moodle_exception('ipmismatch', 'error', '', null, "Remote address: $remoteaddr\nKey IP: " . implode(', ', $key->allowedips));
    }
}