import { useContext, useCallback, useState } from 'react';
import { HackleContext } from '../components';
import { InputUtil } from '../utils';
import { useOnMount } from './useOnMount';
import { LoadableResult, DEFAULT_VARIATION } from '../models';

export function useLoadableVariation(
  experimentKey: number
): LoadableResult<string> {
  const { hackle, userVersion } = useContext(HackleContext);
  const getVariation = useCallback(() => {
    return (
      hackle?.variation(experimentKey) || Promise.resolve(DEFAULT_VARIATION)
    );
  }, [experimentKey, hackle]);

  const [variation, setVariation] = useState(() => {
    if (!hackle) {
      return Promise.resolve(DEFAULT_VARIATION);
    }
    return getVariation();
  });

  const currentInput = {
    key: experimentKey,
    userVersion,
  };

  const [prevInput, setPrevInput] = useState(currentInput);

  if (!InputUtil.isInputEqual(prevInput, currentInput)) {
    setPrevInput(currentInput);
    setVariation(getVariation());
  }

  return useOnMount(variation, DEFAULT_VARIATION);
}