Radicade/Server/Middleware/FailureEnvelopeMiddleware.cs

using RadicadeServer.RecNet.Responses;

namespace RadicadeServer.Middleware
{
	public class FailureEnvelopeMiddleware
	{
		private readonly RequestDelegate _next;

		public FailureEnvelopeMiddleware(RequestDelegate next)
		{
			_next = next;
		}

		public async Task InvokeAsync(HttpContext context)
		{
			await _next(context);

			if (context.Response.HasStarted) return;

			var status = context.Response.StatusCode;
			if (status < 400 || status > 599) return;

			if (!string.IsNullOrEmpty(context.Response.ContentType) || context.Response.ContentLength > 0) return;

			await context.Response.WriteAsJsonAsync(new Failure(Why(status)));
		}

		public static string Why(int statusCode) => statusCode switch
		{
			400 => "bad request",
			401 => "unauthorized",
			403 => "forbidden",
			404 => "not found",
			405 => "method not allowed",
			408 => "request timeout",
			409 => "conflict",
			413 => "request too large",
			415 => "unsupported media type",
			422 => "unprocessable entity",
			429 => "too many requests",
			500 => "internal server error",
			501 => "not implemented",
			502 => "bad gateway",
			503 => "service unavailable",
			504 => "gateway timeout",
			_ => "request failed",
		};
	}
}