zio.http.codec.Alternator.scala Maven / Gradle / Ivy
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/*
* Copyright 2021 - 2023 Sporta Technologies PVT LTD & the ZIO HTTP contributors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* 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 zio.http.codec
import zio.ZNothing
import zio.stacktracer.TracingImplicits.disableAutoTrace
/**
* An alternator is a type class responsible for combining invariant type
* parameters using an Either. It is used to compose parameters of the
* [[zio.http.codec.HttpCodec]] data type.
*/
sealed trait Alternator[L, R] {
type Out
def left(l: L): Out
def right(r: R): Out
def unleft(out: Out): Option[L]
def unright(out: Out): Option[R]
}
object Alternator extends AlternatorLowPriority1 {
type WithOut[L, R, Out0] = Alternator[L, R] { type Out = Out0 }
implicit def leftRightEqual[A]: Alternator.WithOut[A, A, A] =
new Alternator[A, A] {
type Out = A
def left(l: A): Out = l
def right(r: A): Out = r
def unleft(out: Out): Option[A] = Some(out)
def unright(out: Out): Option[A] = Some(out)
}
}
trait AlternatorLowPriority1 extends AlternatorLowPriority2 {
implicit def leftEmpty[A]: Alternator.WithOut[ZNothing, A, A] =
(new Alternator[Any, A] {
type Out = A
def left(l: Any): Out = l.asInstanceOf[Out]
def right(r: A): Out = r
def unleft(out: Out): Option[Any] = None
def unright(out: Out): Option[A] = Some(out)
}).asInstanceOf[Alternator.WithOut[ZNothing, A, A]] // Work around compiler bug
}
trait AlternatorLowPriority2 extends AlternatorLowPriority3 {
implicit def rightEmpty[A]: Alternator.WithOut[A, ZNothing, A] =
(new Alternator[A, Any] {
type Out = A
def left(l: A): Out = l
def right(r: Any): Out = r.asInstanceOf[Out]
def unleft(out: Out): Option[A] = Some(out)
def unright(out: Out): Option[Any] = None
}).asInstanceOf[Alternator.WithOut[A, ZNothing, A]] // Work around compiler bug
}
trait AlternatorLowPriority3 {
implicit def either[A, B]: Alternator.WithOut[A, B, Either[A, B]] =
new Alternator[A, B] {
type Out = Either[A, B]
def left(l: A): Out = Left(l)
def right(r: B): Out = Right(r)
def unleft(out: Out): Option[A] = out.left.toOption
def unright(out: Out): Option[B] = out.toOption
}
}