application.js

实现

---

const http = require("http");
const context = require("./context");
const request = require("./request");
const response = require("./response");
const EventEmitter = require("events");
const Stream = require("stream");

class Application extends EventEmitter {
  constructor(props) {
    super(props);
    this.context = Object.create(context);
    this.request = Object.create(request);
    this.response = Object.create(response);
    this.middlewares = [];
  }
  use(middleware) {
    this.middlewares.push(middleware);
  }
  createContext(req, res) {
    let ctx = Object.create(this.context);
    let request = Object.create(this.request);
    let response = Object.create(this.response);

    ctx.request = request;
    ctx.response = response;
    ctx.request.req = ctx.req = req;
    ctx.response.res = ctx.res = res;

    return ctx;
  }
  compose(ctx) {
    const dispatch = (i) => {
      if (i === this.middlewares.length) {
        return Promise.resolve();
      }
      let middleware = this.middlewares[i];
      try {
        return Promise.resolve(middleware(ctx, () => dispatch(i + 1)));
      } catch (error) {
        return Promise.reject(error);
      }
    };
    return dispatch(0);
  }
  handleRequest = (req, res) => {
    let ctx = this.createContext(req, res);
    this.compose(ctx)
      .then(() => {
        if (ctx.body instanceof Stream) {
          ctx.res.setHeader("Content-Type", "application/octet-stream");
          ctx.body.pipe(res);
        } else {
          res.end(ctx.body);
        }
      })
      .catch((error) => {
        this.emit("error", error);
      });
  };
  listen() {
    const server = http.createServer(this.handleRequest);
    server.listen(...arguments);
  }
}

module.exports = Application;