Source file server_service.ml

open Lwt.Syntax
module Sig = Server_service_sig

let run_forever () =
  let p, _ = Lwt.wait () in
  p
;;

let registered_endpoints : Server_core.endpoint list ref = ref []

(* This is all the Opium & Cohttp specific stuff, it has to live in the service
   implementation, so swapping web server services is easy *)
let res_to_opium res =
  match Http.Res.opium_res res with
  | Some res -> Lwt.return res
  | None ->
    let headers = res |> Http.Res.headers |> Cohttp.Header.of_list in
    let headers =
      Cohttp.Header.add
        headers
        "Content-Type"
        (Http.Core.show_content_type (Http.Res.content_type res))
    in
    let code = res |> Http.Res.status |> Cohttp.Code.status_of_code in
    let headers =
      match Http.Res.redirect_path res with
      | Some path -> Cohttp.Header.add headers "Location" path
      | None -> headers
    in
    let cookie_headers =
      res
      |> Http.Res.cookies
      |> List.map (fun cookie ->
             Cohttp.Cookie.Set_cookie_hdr.make ~secure:false ~path:"/" cookie)
      |> List.map Cohttp.Cookie.Set_cookie_hdr.serialize
    in
    let headers =
      List.fold_left
        (fun headers (k, v) -> Cohttp.Header.add headers k v)
        headers
        cookie_headers
    in
    (match Http.Res.body res with
    | None -> Opium.Std.respond ~headers ~code (`String "") |> Lwt.return
    | Some (Http.Res.String body) ->
      Opium.Std.respond ~headers ~code (`String body) |> Lwt.return
    | Some (File_path fname) ->
      let* cohttp_response = Cohttp_lwt_unix.Server.respond_file ~headers ~fname () in
      Opium_kernel.Rock.Response.of_response_body cohttp_response |> Lwt.return)
;;

let handler_to_opium_handler handler opium_req =
  let* handler = Core.Ctx.empty |> Http.Req.add_to_ctx opium_req |> handler in
  handler |> res_to_opium
;;

let to_opium_builder route =
  let meth = Http.Route.meth route in
  let path = Http.Route.path route in
  let handler = Http.Route.handler route in
  let handler = handler_to_opium_handler handler in
  match meth with
  | Get -> Opium.Std.get path handler
  | Post -> Opium.Std.post path handler
  | Put -> Opium.Std.put path handler
  | Delete -> Opium.Std.delete path handler
  | All -> Opium.Std.all path handler
;;

let endpoints_to_opium_builders endpoints =
  endpoints
  |> List.map (fun (prefix, routes, middleware_stack) ->
         routes
         |> List.map (Http.Route.prefix prefix)
         |> List.map (Middleware.apply_stack middleware_stack)
         |> List.map to_opium_builder)
  |> List.concat
;;

module Opium : Sig.SERVICE = struct
  type config = { port : int option }

  let config port = { port }

  let schema =
    let open Conformist in
    make [ optional (int "PORT") ] config
  ;;

  let start_server _ =
    Logs.debug (fun m -> m "WEB: Starting HTTP server");
    let port_nr = Option.value (Core.Configuration.read schema).port ~default:33000 in
    let app = Opium.Std.App.(empty |> port port_nr |> cmd_name "Sihl App") in
    let builders = endpoints_to_opium_builders !registered_endpoints in
    let app = List.fold_left (fun app builder -> builder app) app builders in
    (* We don't want to block here, the returned Lwt.t will never resolve *)
    let _ = Opium.Std.App.start app in
    run_forever ()
  ;;

  let start_cmd =
    Core.Command.make ~name:"start" ~help:"" ~description:"Start the web server" (fun _ ->
        let ctx = Core.Ctx.empty in
        start_server ctx)
  ;;

  let start ctx = Lwt.return ctx
  let stop _ = Lwt.return ()
  let lifecycle = Core.Container.Lifecycle.create "web-server" ~start ~stop
  let register_endpoints routes = registered_endpoints := routes

  let configure endpoints configuration =
    registered_endpoints := endpoints;
    let configuration = Core.Configuration.make ~schema configuration in
    Core.Container.Service.create ~configuration ~commands:[ start_cmd ] lifecycle
  ;;
end