import invariant from 'invariant'
import { isEmpty, isFunction, isString } from 'lodash'

import checkStore from './checkStore'
import createReducer from '../reducers'

export function injectReducerFactory (store, isValid) {
  return function injectReducer (key, reducer) {
    if (!isValid) { checkStore(store) }

    invariant(
      isString(key) && !isEmpty(key) && isFunction(reducer),
      '(app/utils...) injectReducer: Expected `reducer` to be a reducer function'
    )

    // Check `store.injectedReducers[key] === reducer` for hot reloading when a key is the same but a reducer is different
    if (
      Reflect.has(store.injectedReducers, key) &&
      store.injectedReducers[key] === reducer
    ) {
      return
    }

    store.injectedReducers[key] = reducer // eslint-disable-line no-param-reassign
    store.replaceReducer(createReducer(store.injectedReducers))
  }
}

export default function getInjectors (store) {
  checkStore(store)

  return {
    injectReducer: injectReducerFactory(store, true)
  }
}