Proyectos de Subversion Moodle

<?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 core_ai;

use Psr\Clock\ClockInterface;

/**

 * Rate limiting functionality that can be used by AI providers.

 *

 * @package    core_ai

 * @copyright  2024 Matt Porritt <matt.porritt@moodle.com>

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

class rate_limiter {

    /** @var int TIME_WINDOW Time window in seconds (1 hour). */

    public const TIME_WINDOW = HOURSECS;

    /** @var null|rate_limiter Singleton instance of the rate limiter. */

    private static ?rate_limiter $instance = null;

    /** @var \cache_application Cache instance for rate limiter. */

    private \cache_application $cache;

    /**

     * Constructor.

     *

     * @param ClockInterface $clock Clock instance for time management.

     */

    public function __construct(

        /** @var ClockInterface Clock instance for time management. */

        private ClockInterface $clock,

    ) {

        $this->cache = \cache::make('core', 'ai_ratelimit');

    }

    /**

     * Check global rate limit for a component.

     *

     * @param string $component Name of the component.

     * @param int $ratelimit Number of requests per time window.

     * @return bool True if request is allowed, false otherwise.

     */

    public function check_global_rate_limit(string $component, int $ratelimit): bool {

        $currenttime = $this->clock->now()->getTimestamp();

        return $this->check_limit("global_{$component}", $ratelimit, $currenttime);

    }

    /**

     * Check user rate limit for a component.

     *

     * @param string $component Name of the component.

     * @param int $ratelimit Number of requests per time window.

     * @param int $userid User ID for user-specific rate limit.

     * @return bool True if request is allowed, false otherwise.

     */

    public function check_user_rate_limit(string $component, int $ratelimit, int $userid): bool {

        $currenttime = $this->clock->now()->getTimestamp();

        // Check and update user limit.

        return $this->check_limit("user_{$component}_{$userid}", $ratelimit, $currenttime);

    }

    /**

     * Helper function to check limit in cache.

     *

     * @param string $key Cache key.

     * @param int $ratelimit Number of requests per time window.

     * @param int $currenttime Current timestamp.

     * @return bool True if request is allowed, false otherwise.

     */

    private function check_limit(string $key, int $ratelimit, int $currenttime): bool {

        $ratedata = $this->cache->get($key);

        if ($ratedata === false) {

            // No data found, initialize rate data.

            $ratedata = ['count' => 0, 'start_time' => $currenttime];

        }

        // Remove expired rate data.

        if ($currenttime - $ratedata['start_time'] > self::TIME_WINDOW) {

            $ratedata['count'] = 0;

            $ratedata['start_time'] = $currenttime;

        }

        // Check rate limit.

        if ($ratedata['count'] < $ratelimit) {

            $ratedata['count']++;

            $this->cache->set($key, $ratedata);

            return true;

        }

        // Rate limit exceeded.

        return false;

    }

}