// config.js配置文件
var app = {
    dbUrl:'mongodb://localhost:27017',//数据库地址
    dbName:"koa"//数据库名称
}
module.exports = app;
//引入模块
const MongoDB = require('mongodb');
const MongoClient =MongoDB.MongoClient
const ObjectID = MongoDB.ObjectID;
const Config = require("./config.js");
class Db{
    static getInstance(){//解决多次实例化 实例不共享的问题
        if(!Db.instance){
            Db.instance = new Db();
        }
        return Db.instance;
    }
    constructor(){
        this.dbClient = "";
    }
    connect(){
        let _that = this;
        return new Promise((resolve,reject)=>{
            if(!_that.dbClient){//解决数据库多次连接的问题
消除 DeprecationWarning: current Server Discovery and Monitoring engine is deprecated, and will be removed in a future version. To use the new Server Discover and Monitoring engine, pass option { //useUnifiedTopology: true } to the MongoClient constructor.这个警告可以在 MongoClient.connect方法
的第二个参数传入{useUnifiedTopology: true }
                MongoClient.connect(Config.dbUrl,{useUnifiedTopology: true },function(err, client) {
                    if(err){
                        reject(err);
                    }else{
                        _that.dbClient = client.db(Config.dbName);
                        resolve(_that.dbClient)
                    }
                    //client.close();先不关闭 
                });
            }else{
                resolve(_that.dbClient);
            }
            
        })
       
    }
    find(collectionName,json){

        return new Promise((resolve,reject)=>{
            this.connect().then(function(db){
               var result = db.collection(collectionName).find(json);
               result.toArray(function(err,docs){
                   if(err){
                       reject(err);
                   }else{
                       resolve(docs);
                   }
               })
            })
        })
        
    }
    update(collectionName,json1,json2){
        return new Promise((resolve,reject)=>{
            this.connect().then((db)=>{
                db.collection(collectionName).updateOne(json1,{
                    $set:json2
                },(err,result)=>{
                    if(err){
                        reject(err);
                    }else{
                        resolve(result);
                    }
                })
            })
        })
    }
    insert(collectionName,json){
        return new Promise((resolve,reject)=>{
            this.connect().then((db)=>{
                db.collection(collectionName).insertOne(json,(err,result)=>{
                    if(err){
                        reject(err);
                    }
                    resolve(result);
                })
            })
        })
    }
    delete(collectionName,json){
        return new Promise((resolve,reject)=>{
            this.connect().then((db)=>{
                db.collection(collectionName).removeOne(json,(err,result)=>{
                    if(err){
                        reject(err);
                    }else{
                        resolve(result);
                    }
                })
            })
        })
    }
    // 把id转换为mongodb中的ObjectID对象，便于数据修改删除等操作
    getObjectId(id){
        return new ObjectID(id);
    }
}
module.exports = Db.getInstance();
//使用
const Koa = require('koa');
const path = require("path");
const render = require('koa-art-template');
var router = require('koa-router')();//初始化
const DB = require("./module/db.js");
const bodyParser = require('koa-bodyparser');
const static = require("koa-static");
const app = new Koa();
render(app, {
  root: path.join(__dirname, 'views'),
  extname: '.html',
  debug: process.env.NODE_ENV !== 'production'
});
app.use(bodyParser());
//静态资源中间件可以配置多个
app.use(static(__dirname + '/static'));
// app.use(async function (ctx) {
//   await ctx.render('user');
// });
router.get("/",async (ctx)=>{
  var result = await DB.find("user",{});
  await ctx.render('user',{
    list:result
  });
})
router.get("/add",async (ctx)=>{
  await ctx.render('add');
 
})
router.post("/doAdd",async (ctx)=>{
  var data = await DB.insert("user",ctx.request.body);
  try {
    if(data.result.ok == 1){
      console.log("增加成功");
      ctx.redirect("/");
    }
  } catch (error) {
    console.log(error);
    ctx.redirect("/add");
  }
  
})
router.get("/edit",async (ctx)=>{
  let id = ctx.query.id;//get方法获取id
  console.log(ctx.query);
  let data = await DB.find('user',{"_id":DB.getObjectId(id)})
  await ctx.render('edit',{
    list:data[0]
  });
 
})
router.post("/doEdit",async (ctx)=>{
  let id = ctx.request.body.id;//post方法获取id
  var json2={
    username:ctx.request.body.username,
    age:ctx.request.body.age,
    sex:ctx.request.body.sex
  }
  var data = await DB.update("user",{"_id":DB.getObjectId(id)},json2);
  try {
    if(data.result.ok == 1){
      console.log("编辑成功")
      ctx.redirect("/");
    };
  } catch (error) {
    if(error){
      ctx.redirect("/edit");
    }
  }
 
 
})
router.get("/delete",async (ctx)=>{
  let id = ctx.query.id;
  var data = await DB.delete("user",{"_id":DB.getObjectId(id)});
  try {
    if(data.result.ok == 1){
      console.log("删除成功")
      ctx.redirect("/");
    };
  } catch (error) {
    if(error){
      console.log("删除失败")
      ctx.redirect("/");
    }
  }
 
})
app
  .use(router.routes())//启动路由
  .use(router.allowedMethods());
app.listen(3008);