(*
copyright (c) 2013-2014, simon cruanes
all rights reserved.

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modification, are permitted provided that the following conditions are met:

redistributions of source code must retain the above copyright notice, this
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*)

(** {1 Hash Table with Heterogeneous Keys} *)

type 'b injection = {
  get : (unit -> unit) -> 'b option;
  set : 'b -> (unit -> unit);
}

type 'a t = ('a, unit -> unit) Hashtbl.t

let create n = Hashtbl.create n

let create_inj () =
  let r = ref None in
  let get f =
    r := None;
    f ();
    !r
  and set v =
    (fun () -> r := Some v)
  in
  {get;set}

let get ~inj tbl x =
  try inj.get (Hashtbl.find tbl x)
  with Not_found -> None

let set ~inj tbl x y =
  Hashtbl.replace tbl x (inj.set y)

let length tbl = Hashtbl.length tbl

let clear tbl = Hashtbl.clear tbl

let remove tbl x = Hashtbl.remove tbl x

let copy tbl = Hashtbl.copy tbl

let mem ~inj tbl x =
  try
    inj.get (Hashtbl.find tbl x) <> None
  with Not_found -> false

let find ~inj tbl x =
  match inj.get (Hashtbl.find tbl x) with
    | None -> raise Not_found
    | Some v -> v

let iter_keys tbl f =
  Hashtbl.iter (fun x _ -> f x) tbl

let fold_keys tbl acc f =
  Hashtbl.fold (fun x _ acc -> f acc x) tbl acc

(** {2 Iterators} *)

type 'a sequence = ('a -> unit) -> unit

let keys_seq tbl yield =
  Hashtbl.iter
    (fun x _ -> yield x)
    tbl

let bindings_of ~inj tbl yield =
  Hashtbl.iter
    (fun k value ->
      match inj.get value with
      | None -> ()
      | Some v -> yield (k, v)
    ) tbl

type value =
  | Value : ('b injection -> 'b option) -> value

let bindings tbl yield =
  Hashtbl.iter
    (fun x y -> yield (x, Value (fun inj -> inj.get y)))
    tbl