<?php

namespace App\Services;

use Carbon\Carbon;
use Illuminate\Support\Facades\Redis;

final readonly class UserService
{
    private static function lastSeenKey(int $userId): string
    {
        return sprintf('last_seen:%d', $userId);
    }

    public static function setLastSeen(int $userId, ?Carbon $seenAt = null): void
    {
        Redis::connection()->set(self::lastSeenKey($userId), ($seenAt ?? Carbon::now())->toISOString());
    }

    public static function getLastSeen(int $userId): ?Carbon
    {
        $lastSeen = Redis::connection()->get(self::lastSeenKey($userId));

        return $lastSeen ? Carbon::parse($lastSeen) : null;
    }
}