createContacts.swift

func create(_ req: Request) throws -> EventLoopFuture<[Contact.ReqRes]> {
    if req.loggedIn == false { throw Abort(.unauthorized) }

    let inputData = try req.content.decode([Contact.ReqRes].self)

    return Contact.query(on: req.db).filter(\.$user.$id == req.payload.userId).all().flatMap { contactsRes in
        let contacts = contactsRes.map { $0.response }
        
        let setOriginal = Set(inputData)
        let setServerContacts = Set(contacts)
        let uniqServer = setOriginal.subtracting(setServerContacts)
        let uniqOrg = setServerContacts.subtracting(setOriginal)

        if uniqServer.isEmpty && uniqOrg.isEmpty {
          let contsss = Contact.query(on: req.db)
          .filter(\.$user.$id == req.payload.userId)
          .filter(\.$isRegister == true)
          .all()
          .map { uniqContacts in
            return uniqContacts.map { cc in
              return cc.response
            }
          }
        
        return contsss 
        }

        let newContacts = uniqServer.isEmpty ? uniqOrg : uniqServer

        let results = newContacts.compactMap { (contact: Contact.ReqRes) -> EventLoopFuture<Contact.ReqRes> in
          
          return User.query(on: req.db)
            .filter(\.$phoneNumber == contact.phoneNumber)
            .all()
            .flatMap { users -> EventLoopFuture<Contact.ReqRes> in
              
              let user = users.first == nil ? User(phoneNumber: "") : users.first!

              let contact = Contact(
                phoneNumber: contact.phoneNumber,
                identifier: contact.identifier ?? "",
                fullName: contact.fullName,
                avatar: user.avatar,
                isRegister: user.phoneNumber == contact.phoneNumber,
                userId: contact.userId
              )
              
              return contact.save(on: req.db).transform(to: contact.response) //.map { _ in contact }
              
            }
          
        }

        return results.flatten(on: req.eventLoop)
      
      }
    }