MireaBackend/Endpoint/Configuration/Core/Middleware/MaintenanceModeMiddleware.cs

using Microsoft.AspNetCore.Http;
using Mirea.Api.Endpoint.Common.Attributes;
using Mirea.Api.Endpoint.Common.Interfaces;
using System.Threading.Tasks;

namespace Mirea.Api.Endpoint.Configuration.Core.Middleware;

public class MaintenanceModeMiddleware(RequestDelegate next, IMaintenanceModeService maintenanceModeService, IMaintenanceModeNotConfigureService maintenanceModeNotConfigureService)
{
    private static bool IsIgnoreMaintenanceMode(HttpContext context)
    {
        var endpoint = context.GetEndpoint();
        return endpoint?.Metadata.GetMetadata<MaintenanceModeIgnoreAttribute>() != null;
    }

    public async Task InvokeAsync(HttpContext context)
    {
        if (!maintenanceModeService.IsMaintenanceMode && !maintenanceModeNotConfigureService.IsMaintenanceMode || IsIgnoreMaintenanceMode(context))
            await next(context);
        else
        {

            context.Response.StatusCode = StatusCodes.Status503ServiceUnavailable;
            context.Response.ContentType = "plain/text";

            string error;
            if (maintenanceModeService.IsMaintenanceMode)
            {
                context.Response.Headers.RetryAfter = "600";
                error = "The service is currently undergoing maintenance. Please try again later.";
            }
            else
                error =
                    "The service is currently not configured. Go to the setup page if you are an administrator or try again later.";

            await context.Response.WriteAsync(error);
        }
    }
}