resolveStyle.js

// asPairs :: (Object Any) -> [ (String, Any) ]
const asPairs = object =>
  Object.keys(object).map(key => [key, object[key]])

// asObject :: [ (string, Any) ] -> Object
const asObject = pairs =>
  pairs.reduce((object, [key, value]) => {
    object[key] = value
    return object
  }, {})

// This is not a real haskell type signature, I know
// resolveStyles :: (Object (Or Callable (Object Any))) -> (Object (Object Any))
const resolveStyles = styles => {
  const result = {}

  const functions = asObject(asPairs(styles).map( ([key, value]) =>
    [key, () => {
      if(result[key]) return result[key]
      const x = typeof(value) === 'function'
              ? value.call(functions)
              : value
      result[key] = x
    }]
  ))

  Object.keys(styles).forEach(key => functions[key]())
  return result
}

export default resolveStyles