open Unix
open Printf
open Thread
open Sexp

let send_error ch message details =
  let m = Message.error (Str message, details) in
  Log.warn "Sending error" [m];
  ch m

let send_sexp_syntax_error ch explanation =
  send_error ch explanation (Str "http://people.csail.mit.edu/rivest/Sexp.txt")

let dispatch_message n ch m =
  match m with
  | Message.Post (Str name, body, token) ->
      Node.send_ignore name body
  | Message.Subscribe (Str filter, sink, name, Str reply_sink, Str reply_name) ->
      if Node.bind(filter, n)
      then Node.post_ignore
	  reply_sink
	  (Str reply_name)
	  (Message.subscribe_ok (Str filter))
	  (Str "")
      else Log.warn "Bind failed" [Str filter]
  | Message.Unsubscribe (Str token) ->
      if Node.unbind token
      then ()
      else Log.warn "Unbind failed" [Str token]
  | _ ->
      send_error ch "Message not understood" (Message.sexp_of_message m)

let issue_banner cin cout =
  output_sexp_and_flush cout (Arr [Str "hop"; Str ""]);
  output_sexp_and_flush cout
    (Message.subscribe (Str (Node.local_container_name()),
			Str "", Str "",
			Str "", Str ""));
  true

let relay_handler mtx cin cout n m =
  Util.with_mutex mtx (output_sexp cout) m

let relay_mainloop peername mtx cin cout n =
  let write_sexp = Util.with_mutex mtx (output_sexp cout) in
  (try
    while true do
      dispatch_message n write_sexp (Message.message_of_sexp (Sexp.input_sexp cin))
    done
  with
  | Sexp.Syntax_error explanation ->
      (send_sexp_syntax_error write_sexp explanation;
       Log.info "Disconnected relay for syntax error"
	 [Str (Connections.endpoint_name peername); Str explanation])
  )

let start (s, peername) =
  Connections.start_connection "relay" issue_banner relay_handler relay_mainloop (s, peername)