import { useCallback, useEffect, useState, useTransition } from "react";

type UseAsync = <T>(
  asyncFunction: () => Promise<T>,
  initialValue: T,
) => {
  pending: boolean;
  value: T;
  error: Error | null;
  reload: () => Promise<void>;
};

export const useAsync: UseAsync = <T extends any>(
  asyncFunction: () => Promise<T>,
  initialValue: T,
) => {
  const [pending, setPending] = useState(false);
  const [value, setValue] = useState<T>(initialValue);
  const [error, setError] = useState(null);
  const [, startTransition] = useTransition();

  // The execute function wraps asyncFunction and
  // handles setting state for pending, value, and error.
  // useCallback ensures the below useEffect is not called
  // on every render, but only if asyncFunction changes.
  const execute = useCallback(() => {
    startTransition(() => {
      setPending(true);
      setError(null);
    });

    return asyncFunction()
      .then((response) => startTransition(() => setValue(response)))
      .catch((err) => startTransition(() => setError(err)))
      .finally(() => startTransition(() => setPending(false)));
  }, [asyncFunction]);

  // Call execute if we want to fire it right away.
  // Otherwise execute can be called later, such as
  // in an onClick handler.
  useEffect(() => {
    execute();
  }, [execute]);

  return { reload: execute, pending, value, error };
};