open Wonka_types;

let throttle = f => curry(source => curry(sink => {
  let skip = ref(false);
  let id: ref(option(Js.Global.timeoutId)) = ref(None);
  let clearTimeout = () =>
    switch (id^) {
    | Some(timeoutId) => Js.Global.clearTimeout(timeoutId);
    | None => ()
    };

  source((.signal) => {
    switch (signal) {
    | Start(tb) => {
      sink(.Start((.signal) => {
        switch (signal) {
        | Close => {
          clearTimeout();
          tb(.Close);
        }
        | _ => tb(.signal)
        }
      }));
    }
    | End => {
      clearTimeout();
      sink(.End);
    }
    | Push(x) when !skip^ => {
      skip := true;
      clearTimeout();
      id := Some(Js.Global.setTimeout(() => {
        id := None;
        skip := false;
      }, f(.x)));
      sink(.signal);
    }
    | Push(_) => ()
    }
  });
}));