open Lwt.Infix
open Lwt.Syntax

let successful = ref 0
let failed = ref 0

(* middleware *)
let count_requests inner_handler request =
  try%lwt
    (inner_handler request) >>= (fun response ->
      successful := !successful + 1;
      Lwt.return response)

  with exn ->
    failed := !failed + 1;
    raise exn

let () =
  Dream.run
  @@ Dream.logger
  @@ count_requests
  @@ Dream.router [
    Dream.get "/"
      (fun _ ->
        Dream.html "Hello, world!");

    Dream.get "/error"
      (fun _ ->
        failwith "failed on purpose");

    Dream.get "/count"
      (fun _ ->
        Dream.html (Printf.sprintf "%3i successful requests<br>%3i failed requests" !successful !failed));

    Dream.get "/echo/:word"
      (fun request ->
        Dream.html (Dream.param request "word"));
  ]