validation.ts

import { RequestHandler } from "express";
import { Connection } from "./connection";
import Joi from "joi";

export interface User {
 email: string;
 password: string;
}

export class UserModel implements User {
 constructor(public email: string, public password: string) {}


 // Return fields that can be publicly accessible
 get publicData() {
   return {
     email: this.email,
   };
 }
}

const userSchema = Joi.object<User>({
 // Ensure that email is valid and that it is not too long
 email: Joi.string().email().required().max(100),
 // Ensure that password is secure enough
 password: Joi.string().min(5).max(50),
});


// Inject “Connection” here for easier testing
export const makeCreateUser =
 (connection: Connection): RequestHandler =>
 async (req, res) => {
   // Note - this should be done via middleware, but for purposes of this  
   // article it’s done here instead
   const validationResult = userSchema.validate(req.body);

   if (validationResult.error) {
     throw validationResult.error;
   }

   // At this point we know that all the values are valid!
   const { email, password } = validationResult.value;

   const user = new UserModel(email, password);

   await connection.save(user);

   res.json({
     result: user.publicData,
   });
 };