// redux/rollup.config.js 有些省略
const sourcemap = {
  sourcemap: true,
};

output: {
    // ...
    ...sourcemap,
}

function counter(state, action) {
    if (typeof state === 'undefined') {
        return 0
    }

    switch (action.type) {
        case 'INCREMENT':
        return state + 1
        case 'DECREMENT':
        return state - 1
        default:
        return state
    }
}

var store = Redux.createStore(counter)
var valueEl = document.getElementById('value')

function render() {
    valueEl.innerHTML = store.getState().toString()
}
render()
store.subscribe(render)

document.getElementById('increment')
.addEventListener('click', function () {
    store.dispatch({ type: 'INCREMENT' })
})

// 省略部分暂时无效代码...

// 四处可以断点来看
// 1.
var store = Redux.createStore(counter)
// 2.
function render() {
valueEl.innerHTML = store.getState().toString()
}
render()
// 3.
store.subscribe(render)
// 4.
store.dispatch({ type: 'INCREMENT' })

// 省略了若干代码
export default function createStore(reducer, preloadedState, enhancer) {
    // 省略参数校验和替换
    // 当前的 reducer 函数
    let currentReducer = reducer
    // 当前state
    let currentState = preloadedState
    // 当前的监听数组函数
    let currentListeners = []
    // 下一个监听数组函数
    let nextListeners = currentListeners
    // 是否正在dispatch中
    let isDispatching = false
    function ensureCanMutateNextListeners() {
        if (nextListeners === currentListeners) {
        nextListeners = currentListeners.slice()
        }
    }
    function getState() {
        return currentState
    }
    function subscribe(listener) {}
    function dispatch(action) {}
    function replaceReducer(nextReducer) {}
    function observable() {}
    // ActionTypes.INIT @@redux/INITu.v.d.u.6.r
    dispatch({ type: ActionTypes.INIT })
    return {
        dispatch,
        subscribe,
        getState,
        replaceReducer,
        [$$observable]: observable
    }
}

function dispatch(action) {
    // 判断action是否是对象，不是则报错
    if (!isPlainObject(action)) {
      throw new Error(
        'Actions must be plain objects. ' +
          'Use custom middleware for async actions.'
      )
    }
    // 判断action.type 是否存在，没有则报错
    if (typeof action.type === 'undefined') {
      throw new Error(
        'Actions may not have an undefined "type" property. ' +
          'Have you misspelled a constant?'
      )
    }
    // 不是则报错
    if (isDispatching) {
      throw new Error('Reducers may not dispatch actions.')
    }

    try {
      isDispatching = true
      currentState = currentReducer(currentState, action)
    } finally {
        // 调用完后置为 false
      isDispatching = false
    }
    //  把 收集的函数拿出来依次调用
    const listeners = (currentListeners = nextListeners)
    for (let i = 0; i < listeners.length; i++) {
      const listener = listeners[i]
      listener()
    }
    // 最终返回 action
    return action
  }

var store = Redux.createStore(counter)

function render() {
    valueEl.innerHTML = store.getState().toString()
}
render()

function getState() {
    // 判断正在dispatch中，则报错
    if (isDispatching) {
        throw new Error(
        'You may not call store.getState() while the reducer is executing. ' +
            'The reducer has already received the state as an argument. ' +
            'Pass it down from the top reducer instead of reading it from the store.'
        )
    }
    // 返回当前的state
    return currentState
}

function subscribe(listener) {
    // 订阅参数校验不是函数报错
    if (typeof listener !== 'function') {
      throw new Error('Expected the listener to be a function.')
    }
    // 正在dispatch中，报错
    if (isDispatching) {
      throw new Error(
        'You may not call store.subscribe() while the reducer is executing. ' +
          'If you would like to be notified after the store has been updated, subscribe from a ' +
          'component and invoke store.getState() in the callback to access the latest state. ' +
          'See https://redux.js.org/api-reference/store#subscribelistener for more details.'
      )
    }
    // 订阅为 true
    let isSubscribed = true

    ensureCanMutateNextListeners()
    nextListeners.push(listener)

    // 返回一个取消订阅的函数
    return function unsubscribe() {
      if (!isSubscribed) {
        return
      }
      // 正在dispatch中，则报错
      if (isDispatching) {
        throw new Error(
          'You may not unsubscribe from a store listener while the reducer is executing. ' +
            'See https://redux.js.org/api-reference/store#subscribelistener for more details.'
        )
      }
      // 订阅为 false
      isSubscribed = false

      ensureCanMutateNextListeners()
    //   找到当前监听函数
      const index = nextListeners.indexOf(listener)
    //   在数组中删除
      nextListeners.splice(index, 1)
      currentListeners = null
    }
  }

// examples/js/middlewares.logger.example.js
function logger1({ getState }) {
  return next => action => {
      console.log('will dispatch--1--next, action:', next, action)

      // Call the next dispatch method in the middleware chain.
      const returnValue = next(action)

      console.log('state after dispatch--1', getState())

      // This will likely be the action itself, unless
      // a middleware further in chain changed it.
      return returnValue
  }
}
// 省略 logger2、logger3

// examples/index.2.redux.applyMiddleware.compose.html
var store = Redux.createStore(counter, Redux.applyMiddleware(logger1, logger2,  logger3))

// redux/src/applyMiddleware.js
/**
 * ...
 * @param {...Function} middlewares The middleware chain to be applied.
 * @returns {Function} A store enhancer applying the middleware.
 */
export default function applyMiddleware(...middlewares) {
  return createStore => (...args) => {
    const store = createStore(...args)
    let dispatch = () => {
      throw new Error(
        'Dispatching while constructing your middleware is not allowed. ' +
          'Other middleware would not be applied to this dispatch.'
      )
    }

    const middlewareAPI = {
      getState: store.getState,
      dispatch: (...args) => dispatch(...args)
    }
    const chain = middlewares.map(middleware => middleware(middlewareAPI))
    dispatch = compose(...chain)(store.dispatch)

    return {
      ...store,
      dispatch
    }
  }
}

// redux/src/createStore.js
export default function createStore(reducer, preloadedState, enhancer) {
  // 省略参数校验
  // 如果第二个参数`preloadedState`是函数，并且第三个参数`enhancer`是undefined，把它们互换一下。
  if (typeof preloadedState === 'function' && typeof enhancer === 'undefined') {
    enhancer = preloadedState
    preloadedState = undefined
  }

  if (typeof enhancer !== 'undefined') {
    if (typeof enhancer !== 'function') {
      throw new Error('Expected the enhancer to be a function.')
    }
    // enhancer 也就是`Redux.applyMiddleware`返回的函数
    // createStore 的 args 则是 `reducer, preloadedState`
    /**
     * createStore => (...args) => {
            const store = createStore(...args)
            return {
              ...store,
               dispatch,
            }
        }
     ** /
    // 最终返回增强的store对象。
    return enhancer(createStore)(reducer, preloadedState)
  }
  // 省略后续代码
}

// examples/index.2.redux.applyMiddleware.compose.html
var store = Redux.createStore(counter, Redux.applyMiddleware(logger1, logger2,  logger3))

export default function compose(...funcs) {
  if (funcs.length === 0) {
    return arg => arg
  }

  if (funcs.length === 1) {
    return funcs[0]
  }

  return funcs.reduce((a, b) => (...args) => a(b(...args)))
}

// applyMiddleware.js
dispatch = compose(...chain)(store.dispatch)
// compose
funcs.reduce((a, b) => (...args) => a(b(...args)))

funcs.reduce(function(a, b){
  return function(...args){
    return a(b(...args));
  };
});

const calc = (num) => num * 10 + 10 - 2;
calc(10); // 108

const multiply = (x) => {
   const result = x * 10;
   console.log(result);
   return result;
};
const add = (y) => y + 10;
const minus = (z) => z - 2;

// 计算结果
console.log(minus(add(multiply(10))));
// 100
// 108
// 这样我们就把三个函数计算结果出来了。

const compose = (f, g, h) => {
  return function(x){
    return f(g(h(x)));
  }
}
const calc = compose(minus, add, multiply);
console.log(calc(10));
// 100
// 108

// 我们常用reduce来计算数值数组的总和
[1,2,3,4,5].reduce((pre, item, index, arr) => {
  console.log('(pre, item, index, arr)', pre, item, index, arr);
  // (pre, item, index, arr) 1 2 1 (5) [1, 2, 3, 4, 5]
  // (pre, item, index, arr) 3 3 2 (5) [1, 2, 3, 4, 5]
  // (pre, item, index, arr) 6 4 3 (5) [1, 2, 3, 4, 5]
  // (pre, item, index, arr) 10 5 4 (5) [1, 2, 3, 4, 5]
  return pre + item;
});
// 15

function(x){
  return a(b(x));
}

const compose = (...funcs) => {
  return funcs.reduce((a, b) => {
    return function(x){
      return a(b(x));
    }
  })
}
const calc = compose(minus, add, multiply);
console.log(calc(10));
// 100
// 108

// lodash源码
function baseWrapperValue(value, actions) {
	var result = value;
	// 如果是lazyWrapper的实例，则调用LazyWrapper.prototype.value 方法，也就是 lazyValue 方法
	if (result instanceof LazyWrapper) {
		result = result.value();
	}
	// 类似 [].reduce()，把上一个函数返回结果作为参数传递给下一个函数
	return arrayReduce(actions, function(result, action) {
		return action.func.apply(action.thisArg, arrayPush([result], action.args));
	}, result);
}

export default function combineReducers(reducers) {
  const reducerKeys = Object.keys(reducers)
  const finalReducers = {}
  for (let i = 0; i < reducerKeys.length; i++) {
    const key = reducerKeys[i]

    // 省略一些开发环境判断的代码...

    if (typeof reducers[key] === 'function') {
      finalReducers[key] = reducers[key]
    }
  }

  // 经过一些处理后得到最后的finalReducerKeys
  const finalReducerKeys = Object.keys(finalReducers)

  // 省略一些开发环境判断的代码...

  return function combination(state = {}, action) {
    // ... 省略开发环境的一些判断

   // 用 hasChanged变量 记录前后 state 是否已经修改
    let hasChanged = false
    // 声明对象来存储下一次的state
    const nextState = {}
    //遍历 finalReducerKeys
    for (let i = 0; i < finalReducerKeys.length; i++) {
      const key = finalReducerKeys[i]
      const reducer = finalReducers[key]
      const previousStateForKey = state[key]
      // 执行 reducer
      const nextStateForKey = reducer(previousStateForKey, action)

      // 省略容错代码 ...

      nextState[key] = nextStateForKey
      // 两次 key 对比 不相等则发生改变
      hasChanged = hasChanged || nextStateForKey !== previousStateForKey
    }
    // 最后的 keys 数组对比 不相等则发生改变
    hasChanged =
      hasChanged || finalReducerKeys.length !== Object.keys(state).length
    return hasChanged ? nextState : state
  }
}

function bindActionCreator(actionCreator, dispatch) {
  return function() {
    return dispatch(actionCreator.apply(this, arguments))
  }
}

export default function bindActionCreators(actionCreators, dispatch) {
  if (typeof actionCreators === 'function') {
    return bindActionCreator(actionCreators, dispatch)
  }

  // ... 省略一些容错判断

  const boundActionCreators = {}
  for (const key in actionCreators) {
    const actionCreator = actionCreators[key]
    if (typeof actionCreator === 'function') {
      boundActionCreators[key] = bindActionCreator(actionCreator, dispatch)
    }
  }
  return boundActionCreators
}

// logger 插件，具体实现省略
function logger (store) {
  console.log('store', store);
}
// 作为数组传入
new Vuex.Store({
  state,
  getters,
  actions,
  mutations,
  plugins: process.env.NODE_ENV !== 'production'
    ? [logger]
    : []
})
// vuex 源码 插件执行部分
class Store{
  constructor(){
    // 把vuex的实例对象 store整个对象传递给插件使用
    plugins.forEach(plugin => plugin(this))
  }
}

function logger1({ getState }) {
  return next => action => {
      const returnValue = next(action)
      return returnValue
  }
}

const compose = (...funcs) => {
  if (funcs.length === 0) {
    return arg => arg
  }

  if (funcs.length === 1) {
    return funcs[0]
  }

  // 箭头函数
  // return funcs.reduce((a, b) => (...args) => a(b(...args)))
  return funcs.reduce((a, b) => {
    return function(x){
      return a(b(x));
    }
  })
}

const enhancerStore = Redux.create(reducer, Redux.applyMiddleware(logger1, ...))
enhancerStore.dispatch(action)