wechat.js

'use strict';

const crypto = require('crypto');

const ejs = require('ejs');
const { hook } = require('fc-helper');
const WXBizMsgCrypt = require('wechat-crypto');
const xml2js = require('xml2js');

const {
  handle,
  config
} = require('./biz');

const {
  token: TOKEN,
  encodingAESkey: ENCODING_AES_KEY,
  appid: APPID } = config;

function getSignature (timestamp, nonce, token) {
  var shasum = crypto.createHash('sha1');
  var arr = [token, timestamp, nonce].sort();
  shasum.update(arr.join(''));

  return shasum.digest('hex');
}

function parseXML(xml) {
  return new Promise((resolve, reject) => {
    xml2js.parseString(xml, {trim: true}, function (err, obj) {
      if (err) {
        return reject(err);
      }

      resolve(obj);
    });
  });
}

/*!
 * 将xml2js解析出来的对象转换成直接可访问的对象
 */
function formatMessage (result) {
  var message = {};
  if (typeof result === 'object') {
    for (var key in result) {
      if (!(result[key] instanceof Array) || result[key].length === 0) {
        continue;
      }
      if (result[key].length === 1) {
        var val = result[key][0];
        if (typeof val === 'object') {
          message[key] = formatMessage(val);
        } else {
          message[key] = (val || '').trim();
        }
      } else {
        message[key] = result[key].map(function (item) {
          return formatMessage(item);
        });
      }
    }
  }
  return message;
}

/*!
 * 响应模版
 */
/* eslint-disable indent */
var tpl = ['<xml>',
    '<ToUserName><![CDATA[<%-toUsername%>]]></ToUserName>',
    '<FromUserName><![CDATA[<%-fromUsername%>]]></FromUserName>',
    '<CreateTime><%=createTime%></CreateTime>',
    '<MsgType><![CDATA[<%=msgType%>]]></MsgType>',
  '<% if (msgType === "news") { %>',
    '<ArticleCount><%=content.length%></ArticleCount>',
    '<Articles>',
    '<% content.forEach(function(item){ %>',
      '<item>',
        '<Title><![CDATA[<%-item.title%>]]></Title>',
        '<Description><![CDATA[<%-item.description%>]]></Description>',
        '<PicUrl><![CDATA[<%-item.picUrl || item.picurl || item.pic || item.thumb_url %>]]></PicUrl>',
        '<Url><![CDATA[<%-item.url%>]]></Url>',
      '</item>',
    '<% }); %>',
    '</Articles>',
  '<% } else if (msgType === "music") { %>',
    '<Music>',
      '<Title><![CDATA[<%-content.title%>]]></Title>',
      '<Description><![CDATA[<%-content.description%>]]></Description>',
      '<MusicUrl><![CDATA[<%-content.musicUrl || content.url %>]]></MusicUrl>',
      '<HQMusicUrl><![CDATA[<%-content.hqMusicUrl || content.hqUrl %>]]></HQMusicUrl>',
    '</Music>',
  '<% } else if (msgType === "voice") { %>',
    '<Voice>',
      '<MediaId><![CDATA[<%-content.mediaId%>]]></MediaId>',
    '</Voice>',
  '<% } else if (msgType === "image") { %>',
    '<Image>',
      '<MediaId><![CDATA[<%-content.mediaId%>]]></MediaId>',
    '</Image>',
  '<% } else if (msgType === "video") { %>',
    '<Video>',
      '<MediaId><![CDATA[<%-content.mediaId%>]]></MediaId>',
      '<Title><![CDATA[<%-content.title%>]]></Title>',
      '<Description><![CDATA[<%-content.description%>]]></Description>',
    '</Video>',
  '<% } else if (msgType === "transfer_customer_service") { %>',
    '<% if (content && content.kfAccount) { %>',
      '<TransInfo>',
        '<KfAccount><![CDATA[<%-content.kfAccount%>]]></KfAccount>',
      '</TransInfo>',
    '<% } %>',
  '<% } else { %>',
    '<Content><![CDATA[<%-content%>]]></Content>',
  '<% } %>',
  '</xml>'].join('');
/* eslint-enable indent */

/*!
 * 编译过后的模版
 */
var compiled = ejs.compile(tpl);

var wrapTpl = '<xml>' +
  '<Encrypt><![CDATA[<%-encrypt%>]]></Encrypt>' +
  '<MsgSignature><![CDATA[<%-signature%>]]></MsgSignature>' +
  '<TimeStamp><%-timestamp%></TimeStamp>' +
  '<Nonce><![CDATA[<%-nonce%>]]></Nonce>' +
'</xml>';

var encryptWrap = ejs.compile(wrapTpl);

function reply2CustomerService (fromUsername, toUsername, kfAccount) {
  var info = {};
  info.msgType = 'transfer_customer_service';
  info.createTime = new Date().getTime();
  info.toUsername = toUsername;
  info.fromUsername = fromUsername;
  info.content = {};
  if (typeof kfAccount === 'string') {
    info.content.kfAccount = kfAccount;
  }
  return compiled(info);
}

/*!
 * 将内容回复给微信的封装方法
 */
function reply (content, fromUsername, toUsername) {
  var info = {};
  var type = 'text';
  info.content = content || '';
  if (Array.isArray(content)) {
    type = 'news';
  } else if (typeof content === 'object') {
    if (content.hasOwnProperty('type')) {
      if (content.type === 'customerService') {
        return reply2CustomerService(fromUsername, toUsername, content.kfAccount);
      }
      type = content.type;
      info.content = content.content;
    } else {
      type = 'music';
    }
  }
  info.msgType = type;
  info.createTime = new Date().getTime();
  info.toUsername = toUsername;
  info.fromUsername = fromUsername;
  return compiled(info);
}

const cryptor = new WXBizMsgCrypt(TOKEN, ENCODING_AES_KEY, APPID);

exports.get = hook(async (ctx) => {
  const query = ctx.query;
  // 加密模式
  const encrypted = !!(query.encrypt_type && query.encrypt_type === 'aes' && query.msg_signature);
  const timestamp = query.timestamp;
  const nonce = query.nonce;
  const echostr = query.echostr;

  var valid = false;
  if (encrypted) {
    var signature = query.msg_signature;
    valid = signature === cryptor.getSignature(timestamp, nonce, echostr);
  } else {
    // 校验
    valid = query.signature === getSignature(timestamp, nonce, TOKEN);
  }

  if (!valid) {
    ctx.status = 401;
    ctx.body = 'Invalid signature';
  } else {
    if (encrypted) {
      var decrypted = cryptor.decrypt(echostr);
      ctx.body = decrypted.message;
    } else {
      ctx.body = echostr;
    }
  }
});

exports.post = hook(async (ctx) => {
  const query = ctx.query;
  // 加密模式
  const encrypted = !!(query.encrypt_type && query.encrypt_type === 'aes' && query.msg_signature);
  const timestamp = query.timestamp;
  const nonce = query.nonce;

  if (!encrypted) {
    // 校验
    if (query.signature !== getSignature(timestamp, nonce, TOKEN)) {
      ctx.status = 401;
      ctx.body = 'Invalid signature';
      return;
    }
  }

  // 取原始数据
  var xml = ctx.req.body;
  var result = await parseXML(xml);
  var formatted = formatMessage(result.xml);
  if (encrypted) {
    var encryptMessage = formatted.Encrypt;
    if (query.msg_signature !== cryptor.getSignature(timestamp, nonce, encryptMessage)) {
      ctx.status = 401;
      ctx.body = 'Invalid signature';
      return;
    }
    var decryptedXML = cryptor.decrypt(encryptMessage);
    var messageWrapXml = decryptedXML.message;
    if (messageWrapXml === '') {
      ctx.status = 401;
      ctx.body = 'Invalid signature';
      return;
    }
    var decodedXML = await parseXML(messageWrapXml);
    formatted = formatMessage(decodedXML.xml);
  }

  // 业务逻辑处理
  const body = await handle(formatted);

  /*
   * 假如服务器无法保证在五秒内处理并回复，可以直接回复空串。
   * 微信服务器不会对此作任何处理，并且不会发起重试。
   */
  if (body === '') {
    ctx.body = '';
    return;
  }

  var replyMessageXml = reply(body, formatted.ToUserName, formatted.FromUserName);

  if (!query.encrypt_type || query.encrypt_type === 'raw') {
    ctx.body = replyMessageXml;
  } else {
    var wrap = {};
    wrap.encrypt = cryptor.encrypt(replyMessageXml);
    wrap.nonce = parseInt((Math.random() * 100000000000), 10);
    wrap.timestamp = new Date().getTime();
    wrap.signature = cryptor.getSignature(wrap.timestamp, wrap.nonce, wrap.encrypt);
    ctx.body = encryptWrap(wrap);
  }
});