手写一个http容器【下】下一代渐进式web框架

// 静态文件中间件的伪代码

const path = require("path");
const fs = require("fs");
const { Readable } = require("stream");
// this代表对等体的生命周期；global是全局作用域
const req = this.request;
const res = this.response;
const cfg = global.config;

// path/to/public/是FS中被托管的文件夹路径
// req.staticPath是从url中提炼出来的文件的相对路径
const absPath = path.join(__dirname, "path/to/public/", req.staticPath);
const isFile = await new Promise((resolve, reject) => {
  fs.stat(absPath, (err, stats) => {
    if (err) reject(err);
    else if (stats.isFile()) resolve(true);
    else if (stats.isDirectory()) resolve(false);
    else reject(`${req.url}既不是文件也不是文件夹！`);
  });
});

// 根据文件后缀名判断mime类型
const suffix = isFile ? path.extname(req.url) : "directory";
res.setHeader(
  "Content-Type",
  {
    ".js": "text/javascript; charset=UTF-8",
    ".wasm": "application/wasm",
    ".html": "text/html",
    ".css": "text/css",
    ".png": "image/png",
    directory: "text/plain; charset=UTF-8"
  }[suffix] || "application/octet-stream"
);
// 利用浏览器的古典缓存机制
res.setHeader("Cache-Control", `public, max-age=${cfg.cacheInSec}`);
res.setHeader("ETag", cfg.version);

let r;
if (isFile) {
  r = fs.createReadStream(absPath);
} else {
  // 如果请求的是目录，则构建一个虚拟流来读取目录下的所有内容
  r = new Readable({
    read() {}
  });
  fs.readdirSync(absPath)
    .map(name => path.join(req.staticPath, name))
    .forEach(pa => r.push(pa + "\n"));
  r.push(null);
}
if (!res.headerSent) res.writeHead();

await new Promise((resolve, reject) => {
  r.on("error", err => reject(err));
  r.on("end", resolve);
  r.pipe(res);
});

// 决策树错误处理的伪代码

module.exports = async error => {
  const message = error.message || error || "有内鬼，终止交易";

  //   判断response是否已经发出
  if (this.response.headersSent) {
    //   将message存入假想的日志系统
    await require("path/to/logger").add(message);
  } else {
    this.response.writeHead(400, {
      "Content-Type": "text/html; charset=utf-8",
      "my-error": encodeURIComponent(message)
    });
    this.response.end(`<h1>${message}</h1>`);
  }
};