HttpAppIsAFunction.scala

case class Request(
  method: Method,
  uri: Uri,
  // headers,
  // httpVersion,
  body: String = "",
)
case class Response(
  status: Status,
  // headers,
  // httpVersion,
  body: String = "",
)
type HttpApp = Request => Response

val helloWorld: HttpApp = {
  case Request(POST, Uri("/hello"), name) =>
    Response(OK, s"Hello, $name!")
  case _ => 
    Response(NotFound)
}

// Unit test
val req = Request(POST, Uri("/hello"), "Boston")
// req: Request = Request(POST,Uri(/hello),Boston)
assert("Hello, Boston!", helloWorld(req).body)
// ✔ Hello, Boston!