let read file = ... let write file peers = ... let fetch peer = (* Fetch could mean either or both of: * - fetch peer's we-are-twtxt.txt * - fetch peer's twtxt.txt and extract mentioned peer URIs * *) ... let test peers = ... let rec discover peers_old = let peers_all = Set.fold peers_old ~init:peers_old ~f:(fun peers p -> match fetch p with | Error _ -> (* TODO: Should p be moved to down set here? *) log_warning ...; peers | Ok peers_fetched -> Set.union peers peers_fetched ) in if Set.empty (Set.diff peers_old peers_all) then peers_all else discover peers_all let rec loop interval peers_old = let peers_all = discover peers_old in let (peers_up, peers_down) = test peers_all in write "peers-all.txt" peers_all; write "peers-up.txt" peers_up; write "peers-down.txt" peers_down; sleep interval; loop interval peers_all let () = loop (Sys.argv.(1)) (read "peers-all.txt")