import R from 'ramda'

const isObject = R.compose(R.equals('Object'), R.type);
const allAreObjects = R.compose(R.all(isObject), R.values);
const hasLeft = R.has('left');
const hasRight = R.has('right');
const hasBoth = R.both(hasLeft, hasRight);
const isEqual = R.both(hasBoth, R.compose(R.apply(R.equals), R.values));

const markAdded = R.compose(R.append(undefined), R.values);
const markRemoved = R.compose(R.prepend(undefined), R.values);
const isAddition = R.both(hasLeft, R.complement(hasRight));
const isRemoval = R.both(R.complement(hasLeft), hasRight);

const objectDiff = R.curry(_diff);
function _diff(l, r) {
  return R.compose(
    R.map(R.cond([
      [isAddition, markAdded],
      [isRemoval, markRemoved],
      [hasBoth, R.ifElse(
        allAreObjects,
        R.compose(R.apply(objectDiff), R.values),
        R.values)
      ]
    ])),
    R.reject(isEqual),
    R.useWith(R.mergeWith(R.merge), [R.map(R.objOf('left')), R.map(R.objOf('right'))])
  )(l, r);
}

export default objectDiff;