let http = require("http");

let fs = require("fs");

let path = require("path");

let cheerio = require("cheerio");

let iconv = require("iconv-lite");

let EventEmitter = require("events");

let targetUrl = "http://www.27270.com/ent/meinvtupian/"

//定义一个类继承由events导出的EventEmitter

class myEmitter extends EventEmitter{

    init(){

        //注册downHtmlSuccess，当触发这个事件时，调用里面的方法this.parseHtml(result)

        this.on("downHtmlSuccess",(result)=>{

            this.parseHtml(result)

        })

        //parseHtmlSuccess，当触发这个事件时，调用里面的方法this.downImages(result)

        this.on("parseHtmlSuccess",(result)=>{

            this.downImages(result)

        })

        //最开始运行的是下面这个方法

        this.downHtml(targetUrl)

    }

    downHtml(targetUrl) {

        let chunks = []

        http.get(targetUrl,(response)=>{

            response.on("data",(chunk)=>{

                chunks.push(chunk)

            })

            response.on("end",()=>{

                //重新编码原html的源代码，下面是死操作

                let htmlTar = iconv.decode(Buffer.concat(chunks),"gb2312");

                this.emit("downHtmlSuccess",htmlTar)

            })

        })

    }

    parseHtml(htmlTar){

        let $ = cheerio.load(htmlTar);

        let result = []

        let imgTags = $("div.MeinvTuPianBox>ul>li>a>i>img").toArray();

        for (let i = 0; i < imgTags.length; i++) {

            /*★★★尤其要注意，这里要把每个元素转成DOM对象再取attr值，所以下面两行是错的*/

            /*let src = imgTags[i].src

            let imgName = imgTags[i].alt*/

            let src = $(imgTags[i]).attr("src")

            let imgName = $(imgTags[i]).attr("alt")

            result.push({

                src,

                imgName

            })

        }

        this.emit("parseHtmlSuccess",result)

    }

    downImages(result){

        let targetDir = "images"

        for (let i = 0; i < result.length; i++) {

            let src = result[i].src

            let imgName = result[i].imgName

            http.get(src,(response)=>{

                let filePath = path.join(targetDir,imgName+path.extname(src));

                let writeStream = fs.createWriteStream(filePath);

                response.pipe(writeStream)

            })

        }

    }

}

//创建一个类并调用其init()方法

let emitter = new myEmitter();

emitter.init()