open Lwt.Infix

let session socket path () =
  let rec recv_all reply_bytes () =
    let recv_bytes = Bytes.create 4096 in
    Lwt_unix.recv socket recv_bytes 0 (Bytes.length recv_bytes) []
    >>= function
    | 0 -> Lwt.return (Bytes.to_string reply_bytes)
    | _ -> recv_all (Bytes.cat reply_bytes recv_bytes) ()
  in
  let path_bytes = Bytes.of_string path in
  Lwt_unix.send socket path_bytes 0 (Bytes.length path_bytes) []
  >>= function
  | -1 | 0 -> Lwt_result.fail "Couldn't send"
  | _  -> Lwt_result.ok (recv_all (Bytes.create 0) ())

let gopher ?(port=70) host path =
  let socket = Lwt_unix.(socket PF_INET SOCK_STREAM 0) in
  let host = Unix.inet_addr_of_string host in
  let connection = Lwt_unix.connect socket Unix.(ADDR_INET (host, port)) in
  Lwt_main.run (connection >>= session socket path)