class contactFactory {
  verifyUser({
      UserName: string
      , Opcode: confFactory.VERIFYUSER_OPCODE_VERIFYOK
      , Scene: confFactory.ADDSCENE_PF_WEB
      , Ticket: Ticket
      , VerifyContent: string
  })
}

type RecommendInfo = {
  UserName: string
  NickName: string
  Content:     string // request message
  Ticket:         string // a pass token
  VerifyFlag:  number
}

interface Message = {
  RecommendInfo: RecommendInfo
}

class FriendRequest {
  private info: RecommentInfo
  private hello: string
  private ticket: string

  private contact: Contact

  constructor(): FriendRequest

  send(contact: string|Contact, hello?: string): Promise<any> // 1. send friend request to other
  receive(info?: RecommendInfo): FriendRequest    // 2. receive request from other

  accept(): Promise<any>
}

Interface Wechaty {
  on('friend', (contact: Contact, request: FriendRequest) => void): void
}

if (message.MsgType === MSGTYPE_VERIFYMSG) {
  const request = new FriendRequest()
  request.receive(message.RecommendInfo)
  emit('friend', request.contact, request)
}

// Be Accepted: I've accepted your friend request. Now let's chat!
// Accept: You have added ${NickName} as your WeChat contact. Start chatting!
case Message.Type.SYS:
if (/^You have added (. ) as your WeChat contact. Start chatting!$/.test(m.get('content'))) {
const request = new FriendRequest()
  const contact = Contact.load(m.get('from'))
  request.confirm(contact)

  this.emit('friend', contact)
}

wechaty.on('friend', (contact, request) => {
  if (request) { // 1. we got new request
    if (/secret/.test(request.hello)) {
      request.accept()
    }
  } else { // 2. we got new friend
    console.log('got new friend: '   contact)
  }
})