import { createStore } from 'redux'
// Reducer
function counterReducer (state = { value: 0 }, action) {
  switch (action.type) {
  case 'INCREMENT':
    return { value: state.value + 1 }
  case 'DECREMENT':
    return { value: state.value - 1 }
  default:
    return state
  }
}

let store = createStore(counter)

// Optional - you can pass `initialState` as a second argument
let store = createStore(counter, { value: 0 })

let store = createStore(counter)

// Dispatches an action; this changes the state
store.dispatch({ type: 'INCREMENT' })
store.dispatch({ type: 'DECREMENT' })

// Gets the current state
store.getState()

// Listens for changes
store.subscribe(() => { ... })

import { Provider } from 'react-redux'

React.render(
  <Provider store={store}>
    <App />
  </Provider>, mountNode)

// The <Provider> component makes the store available in your
// React components. You need this so you can use connect().

import { connect } from 'react-redux'

// A functional React component
function App ({ message, onMessageClick }) {
  return (
    <div onClick={() => onMessageClick('hello')}>
      {message}
    </div>
  )
}
// Maps `state` to `props`:
// These will be added as props to the component.
function mapStateToProps (state) {
  return { message: state.message }
}

// Maps `dispatch` to `props`:
function mapDispatchToProps (dispatch) {
  return {
    onMessageClick (message) {
      dispatch({ type: 'click', message })
    }
  }
}

// Connect :
export default connect(mapStateToProps, mapDispatchToProps)(App)

const reducer = combineReducers({
  counter, user, store
})
//Combines multiple reducers into one reducer function.
// See: combineReducers (redux.js.org)