inject-reducer.utility

import { comp, into, map, filter } from 'transducers-js'

/* eslint-disable no-return-assign */
// setReducer :: (a -> {a}) -> ({b} -> {a})
// add reducers that are missing from the store
const setReducer = injectedReducers => ({key, reducer}) => injectedReducers[key] = reducer
/* eslint-enable */

// hasReducer :: (a -> {a}) -> ({b} -> bool)
// returns a boolean based if the reducer to inject exists already or not
const hasReducer = injectedReducers => ({key, reducer}) =>
  Reflect.has(injectedReducers, key) && injectedReducers[key] === reducer

// filterExistingReducersAddNewReducers :: a -> b
const filterExistingReducersAddNewReducers = injectReducers => comp(map(setReducer(injectReducers)), filter(hasReducer(injectReducers)))

// setupNewReducer ({a}, [{b}]) -> {a}
// add new reducers if they do do not already exist in the store
export const setupNewReducers = (injectedReducers, collection) => into(injectedReducers, filterExistingReducersAddNewReducers(injectedReducers), collection)