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

export function useVariation(experimentKey: number): string {
  const { hackle, userVersion } = useContext(HackleContext);
  const getVariation = useCallback(() => {
    return hackle?.variationSync(experimentKey) || DEFAULT_VARIATION;
  }, [experimentKey, hackle]);

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

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

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

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

  return variation;
}