let rec dict_entry_single_object f pdf = function
  | (Pdf.Dictionary d) -> f (Pdf.recurse_dict (dict_entry_single_object f pdf) d)
  | (Pdf.Stream {contents = (Pdf.Dictionary dict, data)}) ->
      f (Pdf.Stream {contents = (Pdf.recurse_dict (dict_entry_single_object f pdf) dict, data)})
  | Pdf.Array a -> Pdf.recurse_array (dict_entry_single_object f pdf) a
  | x -> x

(* FIXME are we sure that functional values can never appear in the equality here? *)
let remove_dict_entry pdf key search =
  let f d =
    match search with
    | None -> Pdf.remove_dict_entry d key
    | Some s ->
        match Pdf.lookup_direct pdf key d with
        | Some v when v = s -> Pdf.remove_dict_entry d key
        | _ -> d
  in
    Pdf.objselfmap (dict_entry_single_object f pdf) pdf;
    pdf.Pdf.trailerdict <- dict_entry_single_object f pdf pdf.Pdf.trailerdict

let replace_dict_entry pdf key value search =
  let f d =
    match search with
    | None -> begin try Pdf.replace_dict_entry d key value with _ -> d end
    | Some s ->
        match Pdf.lookup_direct pdf key d with
        | Some v when v = s -> Pdf.replace_dict_entry d key value
        | _ -> d
  in
    Pdf.objselfmap (dict_entry_single_object f pdf) pdf;
    pdf.Pdf.trailerdict <- dict_entry_single_object f pdf pdf.Pdf.trailerdict