Cats validated example 2

CatsValidatedExample2.scala

import cats.data.Validated
import cats.implicits._

case class User(name: String, age: Int)

type FailFast[A] = Either[List[String], A]
type FailSlow[A] = Validated[List[String], A]

def createUser(html: Map[String, String]): FailSlow[User] =
  (
    readName(html).toValidated,
    readage(html).toValidated
  ).mapN(User.apply)


def readName(html: Map[String, String]): FailFast[String] =
  for {
    name <- getValue("name", html)
    res <- nonBlank(name)
  } yield res


def readage(html: Map[String, String]): FailFast[Int] =
  for {
    ageStr <- getValue("age", html)
    age <- parseInt(ageStr)
    res <- ageMustNotBeNegative(age)
  } yield res


//Predicates
def ageMustNotBeNegative(age: Int): FailFast[Int] =
  Either.cond(age >= 0, age, List(s"Age $age must not be negative"))

def foo(age: Int): FailFast[Int] =
  Either.cond(age != -1, age, List(s"Age $age must not be -1"))


def getValue(key: String, html: Map[String, String]): FailFast[String] =
  html.get(key).toRight(List(s"Key $key does not exist"))

def parseInt(str: String): FailFast[Int] =
  Either.catchOnly[NumberFormatException](str.toInt)
    .leftMap(throwable => List(s"$str must be an integer"))


def nonBlank(str: String): FailFast[String] =
  Right(str)
    .ensure(List(s"$str cannot be blank"))(_.length > 0)