type address = Unix.sockaddr
type socket  = Unix.file_descr

let create () : socket IO.t =
  try IO.return Unix.(socket PF_UNIX SOCK_STREAM 0) with
  | Unix.Unix_error (code, call, param) -> IO.error code call param

let bind socket address : unit IO.t =
  try IO.return (Unix.bind socket address) with
  | Unix.Unix_error (code, call, param) -> IO.error code call param

let connect socket address : unit IO.t =
  try IO.return (Unix.connect socket address) with
  | Unix.Unix_error (code, call, param) -> IO.error code call param

let listen socket limit : unit IO.t =
  try IO.return (Unix.listen socket limit) with
  | Unix.Unix_error (code, call, param) -> IO.error code call param

let accept socket : socket IO.t =
  try IO.return (Unix.accept socket |> fst) with
  | Unix.Unix_error (code, call, param) -> IO.error code call param

let close socket : unit IO.t =
  try IO.return (Unix.close socket) with
  | Unix.Unix_error (code, call, param) -> IO.error code call param

let address () : address IO.t =
  let open IO.Operators in
  let runtime = IO.environment_variable "XDG_RUNTIME_DIR" in
  let display = IO.environment_variable "WAYLAND_DISPLAY" in
  let socket  = IO.environment_variable "WAYLAND_SOCKET"  in
  let display = IO.recover display ~using:!"wayland-0" ~on:Unix.ENOENT in
  let concat runtime display = Format.asprintf "%s/%s" runtime display in
  let fallback = let* runtime in let+ display in concat runtime display in
  let+ filename = IO.recover socket ~using:fallback ~on:Unix.ENOENT in
  Unix.ADDR_UNIX filename