Skip to content

Instantly share code, notes, and snippets.

@nuintun
Last active March 23, 2024 13:52
Show Gist options
  • Save nuintun/d851f276d511b710c6bf7a026f4d3cb2 to your computer and use it in GitHub Desktop.
Save nuintun/d851f276d511b710c6bf7a026f4d3cb2 to your computer and use it in GitHub Desktop.
koa-compose TypeScript 官方实现优化版
/**
* @module compose
*/
export interface Next {
(): Promise<void>;
}
export interface Composed<C> {
(context: C, next?: Next): Promise<void>;
}
export interface Middleware<C> {
(context: C, next: Next): Promise<void> | void;
}
/**
* @function compose
* @description 生成融合中间件
* @param middlewares 中间件数组
*/
export default function compose<C>(middlewares: Middleware<C>[]): Composed<C> {
/**
* @function middleware
* @description 融合中间件
* @param context 执行上下文
* @param next 下一个中间件
*/
return (context, next) => {
let current = -1;
const dispatch = async (index: number, next?: Next): Promise<void> => {
if (index <= current) {
throw new Error('next() called multiple times');
}
current = index;
const { length } = middlewares;
if (index < length) {
const middleware = middlewares[index];
await middleware(context, () => {
return dispatch(index + 1, next);
});
} else if (next) {
await next();
}
};
return dispatch(0, next);
};
}
@nuintun
Copy link
Author

nuintun commented Sep 17, 2021

/**
 * @module compose
 */

interface CallStack {
  index: number;
}

export interface Next {
  (): Promise<void>;
}

export interface Composed<C> {
  (context: C, next?: Next): Promise<void>;
}

export interface Middleware<C> {
  (context: C, next: Next): Promise<void> | void;
}

/**
 * @function dispatch
 * @param middlewares 中间件数组
 * @param index 要执行的中间件索引
 * @param stack 调用栈信息
 * @param context 执行上下文
 * @param [next] 下一个中间件
 */
async function dispatch<C>(
  middlewares: Middleware<C>[],
  index: number,
  stack: CallStack,
  context: C,
  next?: Next
): Promise<void> {
  if (index <= stack.index) {
    throw new Error('next() called multiple times');
  }

  stack.index = index;

  const { length } = middlewares;

  if (index < length) {
    const middleware = middlewares[index];

    await middleware(context, () => {
      return dispatch(middlewares, index + 1, stack, context, next);
    });
  } else if (next) {
    await next();
  }
}

/**
 * @function compose
 * @description 生成融合中间件
 * @param middlewares 中间件数组
 */
export default function compose<C>(middlewares: Middleware<C>[]): Composed<C> {
  /**
   * @function middleware
   * @description 融合中间件
   * @param context 执行上下文
   * @param [next] 下一个中间件
   */
  return (context, next) => {
    const stack = { index: -1 };

    return dispatch<C>(middlewares, 0, stack, context, next);
  };
}

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment