function createStore(reducer){
    let state       = reducer(undefined, {}) //стартовая инициализация состояния, запуск редьюсера со state === undefined
    let cbs         = []                     //массив подписчиков

    const getState  = () => state            //функция, возвращающая переменную из замыкания
    const subscribe = cb => (cbs.push(cb),   //запоминаем подписчиков в массиве
        () => cbs = cbs.filter(c => c !== cb)) //возвращаем функцию unsubscribe, которая удаляет подписчика из списка

    const dispatch  = action => {
        if (typeof action === 'function'){ //если action - не объект, а функция
            return action(dispatch, getState) //запускаем эту функцию и даем ей dispatch и getState для работы
        }
        const newState = reducer(state, action) //пробуем запустить редьюсер
        if (newState !== state){ //проверяем, смог ли редьюсер обработать action
            state = newState //если смог, то обновляем state
            for (let cb of cbs)  cb() //и запускаем подписчиков
        }
    }

    return {
        getState, //добавление функции getState в результирующий объект
        dispatch,
        subscribe //добавление subscribe в объект
    }
}


function jwtDecode(token){
    try {
        return JSON.parse(atob(token.split('.')[1]))
    }
    catch(e){
    }
}

function authReducer(state={}, {type, token}){
    //{
    //  token, payload
    //}

    if (type === 'AUTH_LOGIN'){
        //пытаемся токен раскодировать
        const payload = jwtDecode(token)
        if (payload){ //и если получилось
            return {
                token, payload //payload - раскодированный токен;
            }
        }
    }
    if (type === 'AUTH_LOGOUT'){
        return {}
    }
    return state;
}

const actionAuthLogin = (token) =>
    (dispatch, getState) => {
        const oldState = getState()
        dispatch({type: 'AUTH_LOGIN', token})
        const newState = getState()
        if (oldState !== newState)
            localStorage.authToken = token
    }

const actionAuthLogout = () =>
    dispatch => {
        dispatch({type: 'AUTH_LOGOUT'})
        localStorage.removeItem('authToken')
    }

const actionGoodById = _id =>
    actionPromise('goodById', gql(backendURL,`query goodByID($id: String) {
  GoodFindOne(query: $id) {
    _id
    name
    description
    price
    images {
      url
    }
    owner {
      nick
      avatar {
        url
        text
      }
    }
    categories {
      name
      subCategories {
        name
        goods {
          name
          price
        }
      }
    }
  }
}`, {"id": JSON.stringify([{_id}])}))


function promiseReducer(state = {}, { type, name, status, payload, error }) {
    if (type === "PROMISE") {
        return {
            ...state, //.......скопировать старый state
            [name]: { status, payload, error }, //....... перекрыть в нем один name на новый объект со status, payload и error
        };
    }
    return state;
}

const actionPending   = (name) => ({type: 'PROMISE', status: 'PENDING', name})
const actionFulfilled = (name, payload) => ({type: 'PROMISE', status: 'FULFILLED', name, payload})
const actionRejected  = (name, error) => ({type: 'PROMISE', status: 'REJECTED', name, error})

const actionPromise   = (name, promise) =>
    async dispatch => {
        try {
            dispatch(actionPending(name))
            let payload = await promise
            dispatch(actionFulfilled(name, payload))
            return payload
        }
        catch(e){
            dispatch(actionRejected(name, e))
        }
    }

// const delay = ms => new Promise(ok => setTimeout(() => ok(ms), ms))


function combineReducers(reducers){ //пачку редьюсеров как объект {auth: authReducer, promise: promiseReducer}
    function combinedReducer(combinedState={}, action){ //combinedState - типа {auth: {...}, promise: {....}}
        const newCombinedState = {}
        for (const [reducerName, reducer] of Object.entries(reducers)){
            const newSubState = reducer(combinedState[reducerName], action)
            if (newSubState !== combinedState[reducerName]){
                newCombinedState[reducerName] = newSubState
            }
        }
        if (Object.keys(newCombinedState).length === 0){
            return combinedState
        }
        return {...combinedState, ...newCombinedState}
    }

    return combinedReducer //нам возвращают один редьюсер, который имеет стейт вида {auth: {...стейт authReducer-а}, promise: {...стейт promiseReducer-а}}
}


const store = createStore(combineReducers({auth: authReducer, promise: promiseReducer})) //не забудьте combineReducers если он у вас уже есть
if (localStorage.authToken){
    store.dispatch(actionAuthLogin(localStorage.authToken))
}
//const store = createStore(combineReducers({promise: promiseReducer, auth: authReducer, cart: cartReducer}))
// store.subscribe(() => console.log(store.getState()))



const gql =    (url, query, variables) => fetch(url, {
    method: 'POST',
    headers: {
        "Content-Type": "application/json",
        Accept: "application/json",
    },
    body: JSON.stringify({query, variables})
}).then(res => res.json())
const url = 'http://shop-roles.node.ed.asmer.org.ua'
const backendURL = 'http://shop-roles.node.ed.asmer.org.ua/graphql'

const actionRootCats = () =>
    actionPromise('rootCats', gql(backendURL, `query {
        CategoryFind(query: "[{\\"parent\\":null}]"){
            _id name
        }
    }`))
const actionCatById = (_id) =>  //добавить подкатегории
    actionPromise('catById', gql(backendURL,  `query catById($q: String){
        CategoryFindOne(query: $q){
            _id name goods {
                _id name price images {
                    url
                }
            }
            subCategories {
                name
                _id
            }
        }
    }`, {q: JSON.stringify([{_id}])}))


const actionLogin = (login, password) =>
    actionPromise('login', gql(backendURL,`query log($login:String, $password:String){
                                              login(login:$login, password:$password)
                                            }`, {login, password}))

store.dispatch(actionRootCats())
store.dispatch(actionLogin('test456', '123123'))

//show root categories aside
store.subscribe( () => {
    const rootCats = store.getState().promise.rootCats?.payload?.data.CategoryFind
    if (rootCats){
        aside.innerHTML = ''
        for (let {_id, name} of rootCats){
            const a = document.createElement('a')
            a.href  = `#/category/${_id}`
            a.innerHTML = name
            aside.append(a)
        }
    }
})

// store.subscribe(() => {
//     const catById = store.getState().catById?.payload?.data.CategoryFindOne
// })

//cards showing
store.subscribe( () => {
    let {catById} = store.getState().promise;
    const [,route, _id] = location.hash.split('/')
let subCats = catById.payload?.data.CategoryFindOne.subCategories

    if(catById?.status === 'PENDING') { // if pending, show loading gif
        main.innerHTML = `<img src="Loading_icon.gif">`
    } else if(catById?.payload && route === 'category'){ // if pending stopped
        main.innerHTML = ''
        const {name, id, goods} = catById.payload?.data.CategoryFindOne
        main.innerHTML = `<h1>${name}</h1>`

        if(subCats.length > 0) {
            for(let sub of subCats) {
                console.log(sub)
                let subCat = document.createElement('a')
                subCat.text = sub.name
                subCat.href = `#/category/${sub._id}`
                main.append(subCat)
            }
        }
        // ask about showing subcats
        console.log(store.getState().promise)
        for(let good of goods) {
            let {name, price, images} = good
            let card = document.createElement('div')
            card.className = 'card'
            let cardBody = document.createElement('div')
            let title = document.createElement('p')
            title.className = 'title'
            let img = document.createElement('img')
            let desc = document.createElement('p')
            let cardPrice = document.createElement('p')
            title.innerHTML = name;
            // img.src = `${url}/${images[0].url}`  //ACTIVATE THIS CODE AFTER FINISHING
            cardPrice.innerHTML = `${price} UAH`
            cardBody.append(title, desc, cardPrice) //ADD IMG
            card.append(cardBody)
            main.append(card);
        }

        }
});
//SHOW GOOD
store.subscribe(() => {
    // console.log(store.getState().promise)
    let {goodById} = store.getState().promise
})

window.onhashchange = () => {
    const [,route, _id] = location.hash.split('/')
    const routes = {
        category(){
            store.dispatch(actionCatById(_id))
        },
        good(){
            store.dispatch(actionGoodById(_id));
        }
    }
    console.log(route)
    if (route in routes) {
        routes[route]()
    }
    routes.good()
    console.log(route)
}

window.onhashchange()