1/* 2 * Copyright (c) 2023 Huawei Device Co., Ltd. 3 * Licensed under the Apache License, Version 2.0 (the "License"); 4 * you may not use this file except in compliance with the License. 5 * You may obtain a copy of the License at 6 * 7 * http://www.apache.org/licenses/LICENSE-2.0 8 * 9 * Unless required by applicable law or agreed to in writing, software 10 * distributed under the License is distributed on an "AS IS" BASIS, 11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 * See the License for the specific language governing permissions and 13 * limitations under the License. 14 */ 15 16import type { ActionData } from '../actions/Action'; 17import type { Dispatch } from '../store'; 18 19export interface Middleware { 20 (): (next: Dispatch) => (action: ActionData) => ActionData 21} 22 23export interface Enhancer { 24 (dispatch: Dispatch): Dispatch 25} 26 27export function applyMiddleware(...middlewares: Middleware[]): Enhancer { 28 return (dispatch: Dispatch) => { 29 const chain: Function[] = middlewares.map(middleware => middleware()); 30 return compose(chain)(dispatch); 31 }; 32} 33 34function compose(functions: Function[]): Function { 35 if (functions.length === 0) { 36 return <T = {}>(arg: T): T => arg; 37 } 38 if (functions.length === 1) { 39 return functions[0]; 40 } 41 42 return functions.reduce( 43 (a, b): Function => (...args): void => a(b(...args)) 44 ); 45}