问Dart HttpServer HttpResponse重定向

EN

import 'dart:io';

Future<void> main() async {
  HttpServer server = await HttpServer.bind(InternetAddress.loopbackIPv4, 8000);

  // assert(app.server != null);
  await for (HttpRequest request in server) {
    String path = request.uri.path;
    String method = request.method;

    if (path == "/" && method == "GET") {
      print("get home");
      request.response.write('home page');
      await request.response.close();
    }
    if (path == "/" && method == 'DELETE') {
      print("delete home");
      request.response.write('home page, with delete method');
      await request.response.close();
    }
    if (path == "/thing" && method == "GET") {
      print("get thing");
      request.response.headers.contentType = ContentType.html;
      request.response.write(
          """<form action="/thing"><input type="submit" value="delete"></form>
            <script>
              const form = document.querySelector("form");
              form.addEventListener("submit", event => {
                event.preventDefault();
                fetch("/thing", { method: "DELETE", redirect: 'follow'}).then(response => 
                alert("deleted thing"));
              });
            </script>""");
    }
    if (path == "/thing" && method == "DELETE") {
      print("delete thing");
      await request.response.redirect(Uri(
          scheme: request.requestedUri.scheme,
          host: request.requestedUri.host,
          port: request.requestedUri.port,
          path: "/deleted"));
    }
    if (path == "/deleted" && method == "GET") {
      print("get deleted");
      request.response.write('deleted thing');
      await request.response.close();
    }
    await request.response.close();
  }
}