Enterprise Multi-Tenancy Architecture in Laravel: Multi-DB & Single-DB Tenant Isolation

<?php

declare(strict_types=1);

namespace App\Http\Middleware;

use App\Models\Tenant;
use Closure;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Config;
use Illuminate\Support\Facades\DB;
use Symfony\Component\HttpFoundation\Response;

class ResolveTenantConnectionMiddleware
{
    public function handle(Request $request, Closure $next): Response
    {
        $tenantId = $request->header('X-Tenant-ID') ?? explode('.', $request->getHost())[0];
        $tenant = Tenant::where('domain', $tenantId)->orWhere('id', $tenantId)->first();
        if (!$tenant || !$tenant->is_active) {
            return response()->json(['error' => 'Tenant not found.'], 404);
        }
        Config::set('database.connections.tenant.database', $tenant->database_name);
        DB::purge('tenant');
        DB::reconnect('tenant');
        DB::setDefaultConnection('tenant');
        app()->instance('currentTenant', $tenant);
        return $next($request);
    }
}