package bonsai

Functions that take bonsai values that contain t, and kicking off reads whenever those values change.

The arguments here are chosen to match the results from Bonsai_web_ui_form.Elements.File_picker. So you can do things like:

let%sub file_picker = Bonsai_web_ui_form.Elements.File_select.single () in
let%sub file_from_form =
  let%arr file_picker = file_picker in
  Bonsai_web_ui_form.value file_picker |> Or_error.ok
in
let%sub result = Bonsai_web_ui_file.Read_on_change.create_single_opt file_from_form in
match%sub result with
| None -> Bonsai.const None
| Some (filename, (Bonsai_web_ui_file.Read_on_change.Status.Starting | In_progress _))
  ->
  let%arr filename = filename in
  Some (filename, "file still loading")
| Some (filename, Complete (Error e)) ->
  let%arr e = e
  and filename = filename in
  Some (filename, Error.to_string_hum e)
| Some (filename, Complete (Ok contents)) ->
  let%arr filename = filename
  and contents = contents in
  Some (filename, contents)

NOTE: these computations are not safe for use in Tangle as internally they require a model which cannot be of_sexp'd.