Creating an Effectful API with Mutable State in TypeScript

type RequestStatus = "idle" | "pending" | "error" | "success";

type RequestState<T, E> = {
  data: T | undefined;
  error: E | null;
  status: RequestStatus;
  refresh: () => Promise<void>
};

function createRequestState<A, E>(effect: Effect.Effect<A, E>) {
  const state: RequestState<A, E> = {
    data: undefined,
    error: null,
    status: "idle",
    refresh: runRequest
  };

  async function runRequest() {
    state.status = "pending";
    state.error = null;
    effect.pipe(Effect.either, Effect.runPromise).then(
      Either.match({
        onLeft: (err) => {
          state.data = undefined;
          state.error = err;
          state.status = "error"
        },
        onRight: (data) => {
          state.data = data;
          state.error = null;
          state.status = "success"
        },
      }),
    );
  }

  runRequest()

  return state;
}