smithy4s.optics.Optional.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.optics
import smithy4s.Bijection
// inspired by and adapted from https://www.optics.dev/Monocle/ under the MIT license
/**
* Optional can be seen as the weak intersection between a [[Lens]]
* and a [[Prism]]. It contains the same `replace` function as a [[Lens]]
* and the same `project` function of a [[Prism]].
*/
trait Optional[S, A] { self =>
/**
* Returns a [[Some]] of A from S if it is able to obtain an A.
* Else returns [[None]].
*/
def project(s: S): Option[A]
/** Provides a function to replace the target of the [[Lens]] */
def replace(a: A): S => S
/** Modify the target of the [[Optional]] with a function from A => A */
def modify(f: A => A): S => S =
s => project(s).fold(s)(a => replace(f(a))(s))
/** Compose this [[Optional]] with another [[Optional]]. */
final def andThen[A0](that: Optional[A, A0]): Optional[S, A0] =
new Optional[S, A0] {
def project(s: S): Option[A0] =
self.project(s).flatMap(that.project)
def replace(a: A0): S => S =
self.modify(that.replace(a))
}
/**
* Allows abstracting over an optional target by pointing to
* the inside of the optional value (the value inside of the [[Some]]).
*/
def some[A0](implicit
ev1: A =:= Option[A0]
): Optional[S, A0] =
adapt[Option[A0]].andThen(
Prism[Option[A0], A0](identity)(Some(_))
)
private[this] final def adapt[A0](implicit
@annotation.unused evA: A =:= A0
): Optional[S, A0] =
// safe due to A =:= A0
this.asInstanceOf[Optional[S, A0]]
/**
* Helper function for targeting the value inside of a [[smithy4s.Newtype]]
* or other type with an implicit [[Bijection]] available.
*/
def value[A0](implicit bijection: Bijection[A0, A]): Optional[S, A0] =
new Optional[S, A0] {
def project(s: S): Option[A0] = self.project(s).map(bijection.from(_))
def replace(a: A0): S => S = self.replace(bijection.to(a))
}
}