wechat-lite/server.js

wechat js api

'use strict';
const url = require('url');
const crypto = require('crypto');
const xml2js = require('xml2js');
const js2xml = require('jstoxml');
const { monitorEventLoopDelay } = require('perf_hooks');

/**
   * [parse description]
   * @param  {[type]} data [description]
   * @return {[type]}      [description]
   * @docs http://mp.weixin.qq.com/wiki/17/f298879f8fb29ab98b2f2971d42552fd.html
   */
function parseMessage(xml) {
  return new Promise((resolve, reject) => {
    xml2js.parseString(xml, (err, result) => {
      if (err) return reject(err);
      resolve(Object.keys(result.xml).reduce((item, key) => {
        item[key] = result.xml[key][0];
        return item;
      }, {}));
    });
  });
};

/**
 * [genSignature description]
 * @param  {[type]} token     [description]
 * @param  {[type]} timestamp [description]
 * @param  {[type]} nonce     [description]
 * @return {[type]}           [description]
 */
function genSignature(token, timestamp, nonce) {
  return crypto
    .createHash('sha1')
    .update(([]).slice.call(arguments).sort().join(''))
    .digest('hex');
}

const parseBody = req => {
  return new Promise((resolve, reject) => {
    var buffer = ''; req
      .on('error', reject)
      .on('data', chunk => buffer += chunk)
      .on('end', () => resolve(buffer));
  });
};

/**
 * [WeChatServer]
 * @param {[type]}   token    [description]
 * @param {Function} handler [description]
 */
function WeChatServer(token, handler) {
  /**
   * [send description]
   * @param  {[type]} reply [description]
   * @return {[type]}       [description]
   * @docs http://mp.weixin.qq.com/wiki/1/6239b44c206cab9145b1d52c67e6c551.html
   */
  function sendMsg(message, reply) {
    if (!reply) return;
    const { FromUserName, ToUserName } = message;
    if (typeof reply == 'string') {
      reply = {
        MsgType: 'text',
        Content: reply
      };
    }
    reply = Object.assign(reply, {
      FromUserName: ToUserName,
      ToUserName: FromUserName,
      CreateTime: +new Date,
      MsgId: ~new Date,
    });
    // reply
    const res = this;
    const data = js2xml.toXML({ xml: reply });
    res.setHeader('Content-Type', 'application/xml');
    res.setHeader('Content-Length', new Buffer(data).length);
    res.end(data);
  }
  /**
   * [function description]
   * @param  {[type]} req [description]
   * @param  {[type]} res [description]
   * @return {[type]}     [description]
   */
  return function request(req, res) {
    const { query } = url.parse(req.url, true);
    const { signature, echostr, timestamp, nonce } = query;
    const sign = genSignature(token, timestamp, nonce);
    if (!(signature === sign)) return res.end('Invalidate signature');
    if (req.method === 'GET') return res.end(echostr);
    Promise.resolve(req)
      .then(parseBody)
      .then(parseMessage)
      .then(message => {
        const send = sendMsg.bind(res, message);
        send(handler.call({ send }, null, message));
      }, handler);
  };
};

module.exports = WeChatServer;