example.sc

// If you have some wrappers describing some terms in your model ...
case class Household(owner: String) extends AnyVal
case class Owner(name: String) extends AnyVal

// ... and some adjective or property that describes entities.
case class Rich[T](t: T) extends AnyVal

object Rich {
  import co.upvest.terminology.adjectives.semiauto._
  implicit val adj = deriveAdjective[Rich]
}

// If we import some implicits giving us access to the syntaxes...
import co.upvest.terminology.adjectives.syntax._

// ... we can drop adjectives by using `.as[T]` syntax,
Rich(Household("foo")).as[Household] : Household

// and map on underlying type using `mapU` syntax.
Rich(Household("foo")) mapU { (h: Household) => Owner(h.owner) } : Rich[Owner]


// There are some predefined adjectives.
import co.upvest.terminology.adjectives.common._

// If we have a model password and its length:
case class Password(pw: String) extends AnyVal {
  def length = PasswordLength(pw.length)
}
case class PasswordLength(n: Int) extends AnyVal

// Then we can map the inner-most type (`Password`) as we did above
Secret(Weak(Password("1234"))) mapU { p: Password => p.length } : Secret[Weak[PasswordLength]]

// but we can also let `mapU` select the nesting-level specified by the
// mapped function type:

val passwordStretching: Weak[Password] => Strong[Password] = {
  case Weak(pw) => /* do something clever */; Strong(pw)
}

Secret(Weak(Password("1234"))) mapU passwordStretching : Secret[Strong[Password]]

// We can also make descriptions of our models:
import co.upvest.terminology.description.Description
object Password {
  implicit val description: Description[Password, Weak[Entropic[Array[Byte]]]] = {
    case Password(s) => Weak(Entropic(s.getBytes))
  }
}

// which here expresses that in general users can't be trusted to pick a strong
// password.

import co.upvest.terminology.description.syntax._

Password("1234").description : Weak[Entropic[Array[Byte]]]


// If we then have a cipher algorithm that we want to use:
def cipher(pt: PlainText[Array[Byte]], key: Strong[Entropic[Array[Byte]]]): Encrypted[Array[Byte]] =
  Encrypted(/* some clever transformation using `key` */ pt.as[Array[Byte]])

// We get a compilation error if we try to use the password:
val msg = PlainText("lol".getBytes)
val pwd = Password("1234")
shapeless.test.illTyped("""cipher(msg, pwd)""")

// But if we apply some key stretching:
val keyStretching: Weak[Entropic[Array[Byte]]] => Strong[Entropic[Array[Byte]]] = {
  case Weak(ebs) => /* do something clever */ Strong(ebs)
}

// then the type-checker says we're good to go:
cipher(msg, keyStretching(pwd.description))

// The described types also get access to the `as` and `mapU` syntaxes:
pwd.as[Array[Byte]] : Array[Byte]
pwd mapU { bs: Array[Byte] => new String(bs) } : Weak[Entropic[String]]