import { createStore } from 'redux'
import transys from 'transys'

/**
 *  States
 */
const INVALIDATED = 'INVALIDATED'
const FETCHING = 'FETCHING'
const OK = 'OK'
const states = [INVALIDATED, FETCHING, OK]

const initialState = {
    systemState: INVALIDATED,
    data: null
}

const transitionMatrix = [
    {
        from: INVALIDATED,
        to: FETCHING
    },
    {
        from: FETCHING,
        to: OK,
        do: (state = {}, { data }) => ({
            ...state,
            data
        })
    },
    {
        from: OK,
        to: INVALIDATED
    }
]

const store = createStore(
    transys.buildReducer({
        initialState,
        states,
        transitionMatrix
    })
)

console.log(store.getState().systemState)
// => 'INVALIDATED'

// When dispatching a FETCHING action while in INVALIDATED, the transition is
// applied:
store.dispatch({ type: FETCHING })
console.log(store.getState().systemState)
// => 'FETCHING'

// There is no transition from FETCHING to INVALIDATED:
store.dispatch({ type: INVALIDATED })
console.log(store.getState().systemState)
// => 'FETCHING'

store.dispatch({ type: OK })
console.log(store.getState().systemState)
// => 'OK'

import reduceReducers from 'reduce-reducers'

const store = createStore(
    reduceReducers(
        anotherReducer,
        yourReducer,
        transys.buildReducer({ ... }),
        initialState
    )
)