(** main entry top-level function: `register_nick` *)
module Rwdb = Dokeysto.Db.RW

let get_db (db : string) : Rwdb.t =
  let open Unix in
  let already_exists =
    try access db [F_OK]; true
    with Unix_error(ENOENT,_,_) -> false in
  if already_exists
  then Rwdb.open_existing db
  else Rwdb.create db

let release_db (h : Rwdb.t) : unit = Rwdb.sync h; Rwdb.close h

let try_finalize f x finally y = let res = try f x with exn -> finally y; raise exn in finally y; res

let inc_nick_value (h : Rwdb.t) (nick : string) : unit =
  if Rwdb.mem h nick
  then let n = int_of_string (Rwdb.find h nick) in
       Rwdb.replace h nick (string_of_int (n+1))
  else Rwdb.add h nick "1"


let register_nick (db : string) (nick : string) =
  let h = get_db db in
  try_finalize (inc_nick_value h) nick
    release_db h