<?php

declare(strict_types=1);

namespace LayLink\Protocol;

final class FrameType
{
    public const AUTH = 'AUTH';
    public const AUTH_OK = 'AUTH_OK';
    public const AUTH_FAIL = 'AUTH_FAIL';
    public const PING = 'PING';
    public const PONG = 'PONG';
    public const OPEN = 'OPEN';
    public const OPEN_OK = 'OPEN_OK';
    public const OPEN_FAIL = 'OPEN_FAIL';
    public const DATA = 'DATA';
    public const UDP_DATA = 'UDP_DATA';
    public const CLOSE = 'CLOSE';
    public const ERROR = 'ERROR';
    public const WINDOW = 'WINDOW';

    /**
     * @return array<string, string>
     */
    public static function descriptions(): array
    {
        return [
            self::AUTH => 'Agent authenticates to POP Server.',
            self::AUTH_OK => 'POP Server accepts Agent authentication.',
            self::AUTH_FAIL => 'POP Server rejects Agent authentication.',
            self::PING => 'Agent heartbeat to POP Server.',
            self::PONG => 'POP Server heartbeat response.',
            self::OPEN => 'Client Agent asks POP Server to open an authorized target stream.',
            self::OPEN_OK => 'POP Server confirms target stream is open.',
            self::OPEN_FAIL => 'POP Server rejects or fails target stream opening.',
            self::DATA => 'Bidirectional stream bytes, base64 encoded in MVP.',
            self::UDP_DATA => 'Bidirectional UDP datagram relay, base64 encoded in MVP.',
            self::CLOSE => 'Either side closes a stream session.',
            self::ERROR => 'Explicit protocol or session error.',
            self::WINDOW => 'Flow-control window update, reserved for backpressure.',
        ];
    }
}