72 # http 缓存策略

// 核心模块
const http = require("http");
const path = require("path");
const url = require("url");
const fs = require("fs").promises;
const crypto = require("crypto");
const { createReadStream, createWriteStream, readFileSync } = require("fs");
// 第三方模块
const ejs = require("ejs"); // 服务端读取目录进行渲染
const mime = require("mime");
const chalk = require("chalk");
const debug = require("debug")("server");
// 根据环境变量来进行打印 process.env.EDBUG
debug("hello kaimo-http-server");
// 同步读取模板
const template = readFileSync(path.resolve(__dirname, "template.ejs"), "utf-8");
class Server {
    constructor(config) {
        this.host = config.host;
        this.port = config.port;
        this.directory = config.directory;
        this.template = template;
    }
    async handleRequest(req, res) {
        let { pathname } = url.parse(req.url);
        // 需要对 pathname 进行一次转义，避免访问中文名称文件找不到问题
        console.log(pathname);
        pathname = decodeURIComponent(pathname);
        console.log(pathname);
        // 通过路径找到这个文件返回
        let filePath = path.join(this.directory, pathname);
        console.log(filePath);
        try {
            // 用流读取文件
            let statObj = await fs.stat(filePath);
            // 判断是否是文件
            if (statObj.isFile()) {
                this.sendFile(req, res, filePath, statObj);
            } else {
                // 文件夹的话就先尝试找找 index.html
                let concatFilePath = path.join(filePath, "index.html");
                try {
                    let statObj = await fs.stat(concatFilePath);
                    this.sendFile(req, res, concatFilePath, statObj);
                } catch (e) {
                    // index.html 不存在就列出目录
                    this.showList(req, res, filePath, statObj, pathname);
                }
            }
        } catch (e) {
            this.sendError(req, res, e);
        }
    }
    // 列出目录
    async showList(req, res, filePath, statObj, pathname) {
        // 读取目录包含的信息
        let dirs = await fs.readdir(filePath);
        console.log(dirs, "-------------dirs----------");
        try {
            let parseObj = dirs.map((item) => ({
                dir: item,
                href: path.join(pathname, item) // url路径拼接自己的路径
            }));
            // 渲染列表：这里采用异步渲染
            let templateStr = await ejs.render(this.template, { dirs: parseObj }, { async: true });
            console.log(templateStr, "-------------templateStr----------");
            res.setHeader("Content-type", "text/html;charset=utf-8");
            res.end(templateStr);
        } catch (e) {
            this.sendError(req, res, e);
        }
    }
    gzip(req, res, filePath, statObj) {
        if (req.headers["accept-encoding"] && req.headers["accept-encoding"].includes("gzip")) {
            // 给响应头添加内容编码类型头，告诉浏览器内容是什么编码类型
            res.setHeader("Content-Encoding", "gzip");
            // 创建转化流
            return require("zlib").createGzip();
        } else {
            return false;
        }
    }
    // 设置缓存
    async cache(req, res, filePath, statObj) {
        // 先设置强制缓存
        res.setHeader("Expires", new Date(Date.now() + 10 * 1000).toGMTString());
        res.setHeader("Cache-Control", "max-age=10");
        // 再设置协商缓存
        let fileContent = await fs.readFile(filePath);
        // 指纹
        let ifNoneMatch = req.headers["if-none-match"];
        let etag = crypto.createHash("md5").update(fileContent).digest("base64");
        // 修改时间
        let ifModifiedSince = req.headers["if-modified-since"];
        let ctime = statObj.ctime.toGMTString();
        res.setHeader("Last-Modified", ctime);
        res.setHeader("ETag", etag);
        // 文件变动了就不缓存，读取新文件
        if (ifNoneMatch !== etag) {
            return false;
        }
        if (ifModifiedSince !== ctime) {
            return false;
        }
        return true;
    }
    // 读取文件返回
    async sendFile(req, res, filePath, statObj) {
        // 缓存
        let cache = await this.cache(req, res, filePath, statObj);
        // 有缓存直接让用户查找缓存即可
        if (cache) {
            res.statusCode = 304;
            return res.end();
        }
        // 设置类型
        res.setHeader("Content-type", mime.getType(filePath) + ";charset=utf-8");
        // 读取文件进行响应
        // 先判断浏览器是否支持 gzip 压缩
        let gzip = this.gzip(req, res, filePath, statObj);
        if (gzip) {
            createReadStream(filePath).pipe(gzip).pipe(res);
        } else {
            createReadStream(filePath).pipe(res);
        }
    }
    // 专门处理错误信息
    sendError(req, res, e) {
        debug(e);
        res.statusCode = 404;
        res.end("Not Found");
    }
    start() {
        const server = http.createServer(this.handleRequest.bind(this));
        server.listen(this.port, this.host, () => {
            console.log(chalk.yellow(`Starting up kaimo-http-server, serving ./${this.directory.split("\\").pop()}\r\n`));
            console.log(chalk.green(`       http://${this.host}:${this.port}`));
        });
    }
}
module.exports = Server;

kaimo-http-server