path: root/prl_api/sakura_prl_api.ml

type value = Obj.t
type tuple = (string * value) list

type implementation =
  { membership_criteria: (tuple -> (bool, string) result) option;
    produce: (tuple -> (tuple list, string) result) option }

(* TODO: Rethink this instead in terms of a value.
   We need to store the references as a normal relation
   on the multigroup relation catalog. *)
let registry : (string, implementation) Hashtbl.t = Hashtbl.create 32
let mutex = Mutex.create ()
let register symbol impl = Mutex.protect mutex (fun () -> Hashtbl.replace registry symbol impl)
let find symbol = Mutex.protect mutex (fun () -> Hashtbl.find_opt registry symbol)
let symbols () = Mutex.protect mutex (fun () -> Hashtbl.to_seq_keys registry |> List.of_seq)

let implementation_of_rows ?membership_criteria (rows : tuple list) : implementation =
  {membership_criteria; produce= Some (fun _bindings -> Ok rows)}

let implementation_of_producer ?membership_criteria (produce : tuple -> (tuple list, string) result)
    : implementation =
  {membership_criteria; produce= Some produce}

let implementation_of_unit_producer ?membership_criteria
    (produce : unit -> (tuple list, string) result) : implementation =
  {membership_criteria; produce= Some (fun _bindings -> produce ())}