{ transaction_id: '4200000005201712165508745023', // 交易
 out_trade_no: '5b97cba0ae164bd58dfe9e77891d3aaf', // 自己这头的交易号
 out_refund_no: '6f3240c353934105be34eb9f2d364cec', // 退款订单，自己生成
 total_fee: 1, // 退款总额
 nonce_str: '1xSZW0op0KcdKoMYxnyxhEuF1fAQefhU', // 随机串
 appid: 'wxff154ce14ad59a55', // 小程序 appid
 mch_id: '1447716902', // 微信支付商户id
 sign: '416FCB62F9B8F03C82E83052CC77524B' // 签名,weixin-pay这个module帮助生成 }

const WXPay = require('weixin-pay'); // 引入weixin-pay这个第三方模块
const {weapp} = require('../../../utils/config'); // 我自己的全局配置文件，包括了appid key 等
const fs = require('fs');
const wxpay = WXPay({
 appid: weapp.APPID,
 mch_id: weapp.MCHID,
 partner_key: weapp.KEY, //微信商户平台 API secret，非小程序 secret
 pfx: fs.readFileSync(__dirname + '/../../../cert/apiclient_cert.p12'), 
});

module.exports = wxpay;

const wxpay = require('./wxpay');

const validateSign = results => {
 const sign = wxpay.sign(results);
 if (sign !== results.sign) {
 const error = new Error('微信返回参数签名结果不正确');
 error.code = 'INVALID_RESULT_SIGN';
 throw error;
 };
 return results;
};

const handleError = results => {
 if (results.return_code === 'FAIL') {
 throw new Error(results.return_msg);
 }
 if (results.result_code !== 'SUCCESS') {
 const error = new Error(results.err_code_des);
 error.code = results.err_code;
 throw error;
 }
 return results;
};

module.exports = {
 validateSign,
 handleError,
};

// 退款
router.post('/refund', function(req, res) {
 Order.findById(req.body._id, (err, order) => {
  if (err) {
   console.log(err);
  }
  console.log(order);
  // 生成微信设定的订单格式
  var data = {
   transaction_id: order.transactionId,
   out_trade_no: order.tradeId,
   out_refund_no: uuid().replace(/-/g, ''),
   total_fee: order.amount,
   refund_fee: order.amount
  };
  console.log(data);
  // 先查询订单，再退订单
  wxpay.refund(data, (err, result) => {
   if (err) {
    console.log(err);
    res.send(
     utils.json({
      code: 500,
      msg: '退款失败'
     })
    );
   }
   // 返回退款请求成功后，要将订单状态改成REFUNDED
   if (result.result_code === 'SUCCESS') {
    console.log(result);
    order.status = 'REFUNDED';
    order.save((err, response) => {
     res.send(
      utils.json({
       msg: '退款成功'
      })
     );
    });
   } else {
    res.send(
     utils.json({
      code: 500,
      msg: result.err_code_des
     })
    );
   }

  });
 });
});

 appid:"wxff154ce14ad59a55"
 cash_fee:"1"
 cash_refund_fee:"1"
 coupon_refund_count:"0"
 coupon_refund_fee:"0"
 mch_id:"1447716902"
 nonce_str:"c44wOvB6a4bQJfRk"
 out_refund_no:"9ace1466432a4d548065dc8df95d904a"
 out_trade_no:"5b97cba0ae164bd58dfe9e77891d3aaf"
 refund_channel:""
 refund_fee:"1"
 refund_id:"50000705182017121702756172970"
 result_code:"SUCCESS"
 return_code:"SUCCESS"
 return_msg:"OK"
 sign:"5C2E67B3250054E8A665BF1AE2E9BDA3"
 total_fee:"1"
 transaction_id:”4200000005201712165508745023”

 appid:"wxff154ce14ad59a55"
 err_code:"ERROR"
 err_code_des:"订单已全额退款"
 mch_id:"1447716902"
 nonce_str:"KP1YWlU7a5viZEgK"
 result_code:"FAIL"
 return_code:"SUCCESS"
 return_msg:"OK"
 sign:”C2A7DED787BEA644C325E37D96E9F41C”