https://www.youtube.com/watch?v=YXDm3WHZT5g

plain-fp.sc

case class Config(name: String, age: Int)
case class Name(firstName: String, lastName: String)
case class Age(age: Int) extends AnyVal
case class Person(name: Name, age: Age)

object Configs:
  type Configured[T] = Config ?=> T
  def config: Configured[Config] = summon[Config]

object Exceptions:
  private class E extends Exception

  class CanThrow private[Exceptions]():
    private[Exceptions] def throwE() = throw new E

  type Possibly[T] = CanThrow ?=> T

  def require(p: Boolean)(using ct: CanThrow):Unit = if (!p) ct.throwE()

  def attempt[T](op: Possibly[T]) = new OnError(op)

  class OnError[T](op: Possibly[T]):
    def onError(fallback: => T): T =
      try op(using new CanThrow)
      catch 
        case ex: E => fallback

import Configs.*
import Exceptions.*

def readName: Possibly[Configured[Name]] =
  val parts = config.name.split(" ")
  require(parts.length >= 2)
  Name(parts(0), parts.tail.mkString)

def readAge: Configured[Possibly[Age]] =
  val age = config.age
  require(1 <= age && age <= 150)
  Age(age)

// Note: readName & readAge can only be invoked in attempt
// because of Context Functions i.e. Algebraic Effect
def readPerson: Configured[Option[Person]] =
  attempt(Some(Person(readName, readAge))).onError(None)

println(readPerson(using Config("John Doe", 20)))
println(readPerson(using Config("Incognito", 99)))