store.js

import { createStore, applyMiddleware, compose } from 'redux'
import { combineReducers } from 'redux'
import { createEpicMiddleware } from 'redux-observable';
import { combineEpics } from 'redux-observable';
import thunk from 'redux-thunk'

import overview from 'src/overview'

const rootReducer = combineReducers({
    overview: overview.reducer,
})

const rootEpic = combineEpics(
    ...Object.values(overview.epics),
)

export default function configureStore({ReduxDevTools=undefined}={}) {
  const enhancers = [
      applyMiddleware(
          createEpicMiddleware(rootEpic),
          thunk,
      ),
  ]
  if (ReduxDevTools) {
      enhancers.push(ReduxDevTools.instrument())
  }
  const enhancer = compose(...enhancers)

  const store = createStore(
    rootReducer,
    undefined, // initial state
    enhancer
  )

  return store
}