smithy4s.Nullable.scala Maven / Gradle / Ivy
/*
* Copyright 2021-2024 Disney Streaming
*
* Licensed under the Tomorrow Open Source Technology License, Version 1.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://disneystreaming.github.io/TOST-1.0.txt
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package smithy4s
import smithy4s.Nullable._
/**
* ADT isomorphic to `Option`, but representing types that were passed explicitly as
* null rather than ones that were absent.
*
* The goal of this datatype is to offer the ability to distinguish, during
* serialisation, between the absence of a field and the nullity of a field.
*/
sealed trait Nullable[+A] {
def map[B](f: A => B): Nullable[B] = this match {
case Value(a) => Value(f(a))
case Null => Null
}
def fold[B](whenNull: => B)(whenValue: A => B): B =
this match {
case Value(a) => whenValue(a)
case Null => whenNull
}
def toOption: Option[A] = this match {
case Value(a) => Some(a)
case Null => None
}
}
object Nullable {
def value[A](a: A): Nullable[A] = Value(a)
def fromOption[A](option: Option[A]) = option match {
case Some(a) => Value(a)
case None => Null
}
final case class Value[A](a: A) extends Nullable[A]
case object Null extends Nullable[Nothing]
private[smithy4s] def schema[A](schemaA: Schema[A]): Schema[Nullable[A]] = {
schemaA.addMemberHints(alloy.Nullable()).option.biject {
Bijection[Option[A], Nullable[A]](fromOption, _.toOption)
}
}
private[smithy4s] object Schema {
import smithy4s.Schema.{BijectionSchema, OptionSchema}
def unapply[A](schema: Schema[A]): Option[Schema[_]] = {
schema match {
case bs: BijectionSchema[_, _] if bs.hints.has(alloy.Nullable) =>
bs.underlying match {
case os: OptionSchema[_] => Some(os.underlying)
case _ => None
}
case _ => None
}
}
}
}