open Wonka_types;

let debounce = f => curry(source => curry(sink => {
  let gotEndSignal = ref(false);
  let id: ref(option(Js.Global.timeoutId)) = ref(None);

  let clearTimeout = () =>
    switch (id^) {
    | Some(timeoutId) => {
      id := None;
      Js.Global.clearTimeout(timeoutId);
    }
    | None => ()
    };

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

      switch (id^) {
      | None => sink(.End)
      | _ => ()
      };
    }
    }
  });
}));