smithy4s.optics.Lens.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
/**
* Lens implementation which can be used to abstract over accessing/updating
* a member of a product type
*/
trait Lens[S, A] extends Optional[S, A] { self =>
/** Retrieve the target of the [[Lens]] */
def get(s: S): A
/** Provides a function to replace the target of the [[Lens]] */
def replace(a: A): S => S
/** Retrieve the target of the [[Lens]] as an Optional (implemented to conform to [[Optional]]) */
final def project(s: S): Option[A] = Some(get(s))
/** Modify the target of the [[Lens]] with a function from A => A */
override final def modify(f: A => A): S => S =
s => replace(f(get(s)))(s)
/**
* Compose this [[Lens]] with another [[Lens]].
* The result will be a lens that starts with the source
* of the first lens and points to the target of the second
* lens.
*/
final def andThen[A0](that: Lens[A, A0]): Lens[S, A0] =
new Lens[S, A0] {
def get(s: S): A0 =
that.get(self.get(s))
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]]).
*/
final override 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
): Lens[S, A0] =
// safe due to A =:= A0
this.asInstanceOf[Lens[S, A0]]
/**
* Helper function for targeting the value inside of a [[smithy4s.Newtype]]
* or other type with an implicit [[Bijection]] available.
*/
final override def value[A0](implicit
bijection: Bijection[A0, A]
): Lens[S, A0] =
new Lens[S, A0] {
def get(s: S): A0 = bijection.from(self.get(s))
def replace(a: A0): S => S = self.replace(bijection.to(a))
}
}
object Lens {
/**
* Construct a new [[Lens]] by providing functions for getting
* A from S and updating S given a new A.
*/
def apply[S, A](_get: S => A)(_replace: A => S => S): Lens[S, A] =
new Lens[S, A] {
def get(s: S): A = _get(s)
def replace(a: A): S => S = _replace(a)
}
}