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Resolver.scala
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Resolver.scala
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/*
* Copyright 2023 Valdemar Grange
*
* 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 gql.resolver
import cats.data._
import cats._
import cats.implicits._
import gql._
/** Resolver is one of the core abstractions of gql. The resolver class contains a collection of methods to aid comosition.
*
* A Resolver forms an [[cats.arrow.Arrow]]; it can lift a function I => O. Resolver also forms [[cats.arrow.Choice]] which allows
* conditional branching.
*
* Resolver also forms an [[cats.Applicative]] instance that sequences the operations.
*
* Some methods are only available resolvers that have a certain shape. Consider taking a look at the companion object for more
* information.
*/
final class Resolver[+F[_], -I, +O](private[gql] val underlying: Step[F, I, O]) {
def andThen[F2[x] >: F[x], O2](that: Resolver[F2, O, O2]): Resolver[F2, I, O2] =
new Resolver(Step.compose(underlying, that.underlying))
def compose[F2[x] >: F[x], I1 <: I, I2](that: Resolver[F2, I2, I1]): Resolver[F2, I2, O] =
that andThen this
def map[O2](f: O => O2): Resolver[F, I, O2] =
this andThen Resolver.lift(f)
def evalMap[F2[x] >: F[x], O2](f: O => F2[O2]): Resolver[F2, I, O2] =
this andThen Resolver.effect(f)
def emap[O2](f: O => Ior[String, O2]): Resolver[F, I, O2] =
this.map(f) andThen (new Resolver(Step.embedError))
def first[C]: Resolver[F, (I, C), (O, C)] =
new Resolver(Step.first(underlying))
def arg[A](arg: Arg[A]): Resolver[F, I, (A, O)] =
this andThen Resolver.argument[F, O, A](arg).tupleIn
def contraArg[A, I2](arg: Arg[A])(implicit ev: (A, I2) <:< I): Resolver[F, I2, O] =
Resolver.id[F, I2].arg(arg) andThen this.contramap(ev.apply)
def meta[F2[x] >: F[x]]: Resolver[F2, I, (FieldMeta[F2], O)] =
this andThen Resolver.meta[F2, O].tupleIn
def streamMap[F2[x] >: F[x], O2](f: O => fs2.Stream[F2, O2]): Resolver[F2, I, O2] =
this.map(f).embedStream
def sequentialStreamMap[F2[x] >: F[x], O2](f: O => fs2.Stream[F2, O2]): Resolver[F2, I, O2] =
this.map(f).embedSequentialStream
def step: Step[F, I, O] = underlying
def covaryAll[F2[x] >: F[x], O2 >: O]: Resolver[F2, I, O2] = this
}
object Resolver extends ResolverInstances {
def liftFull[F[_], I, O](f: I => O): Resolver[F, I, O] =
new Resolver(Step.lift(f))
final class PartiallyAppliedLift[F[_], I](private val dummy: Boolean = true) extends AnyVal {
def apply[O](f: I => O): Resolver[F, I, O] = liftFull(f)
}
def lift[F[_], I]: PartiallyAppliedLift[F, I] = new PartiallyAppliedLift[F, I]
def id[F[_], I]: Resolver[F, I, I] =
lift(identity)
def effectFull[F[_], I, O](f: I => F[O]): Resolver[F, I, O] =
liftFull(f).andThen(new Resolver(Step.embedEffect))
final class PartiallAppliedEffect[F[_], I](private val dummy: Boolean = true) extends AnyVal {
def apply[O](f: I => F[O]): Resolver[F, I, O] = effectFull(f)
}
def effect[F[_], I]: PartiallAppliedEffect[F, I] = new PartiallAppliedEffect[F, I]
def argument[F[_], I <: Any, A](arg: Arg[A]): Resolver[F, I, A] =
new Resolver(Step.argument(arg))
def meta[F[_], I <: Any]: Resolver[F, I, FieldMeta[F]] =
new Resolver(Step.getMeta)
def streamFull[F[_], I, O](f: I => fs2.Stream[F, O]): Resolver[F, I, O] =
liftFull(f).andThen(new Resolver(Step.embedStream))
final class PartiallyAppliedStream[F[_], I](private val dummy: Boolean = true) extends AnyVal {
def apply[O](f: I => fs2.Stream[F, O]): Resolver[F, I, O] = streamFull(f)
}
def stream[F[_], I]: PartiallyAppliedStream[F, I] = new PartiallyAppliedStream[F, I]
def batch[F[_], K, V](f: Set[K] => F[Map[K, V]]): State[gql.SchemaState[F], Resolver[F, Set[K], Map[K, V]]] =
Step.batch[F, K, V](f).map(new Resolver(_))
def inlineBatch[F[_], K, V](f: Set[K] => F[Map[K, V]]): Resolver[F, Set[K], Map[K, V]] =
new Resolver(Step.inlineBatch(f))
implicit class ResolverInvariantOps[F[_], I, O](private val self: Resolver[F, I, O]) extends AnyVal {
def choose[I2, O2](that: Resolver[F, I2, O2]): Resolver[F, Either[I, I2], Either[O, O2]] =
new Resolver(Step.choose(self.underlying, that.underlying))
def choice[I2](that: Resolver[F, I2, O]): Resolver[F, Either[I, I2], O] =
choose[I2, O](that).map(_.merge)
def skippable: Resolver[F, Either[I, O], O] =
this.choice(Resolver.id[F, O])
def through[O2](f: Resolver[F, O, O] => Resolver[F, O, O2]): Resolver[F, I, O2] =
self andThen f(Resolver.id[F, O])
def contramap[I2](f: I2 => I): Resolver[F, I2, O] =
Resolver.lift(f) andThen self
def tupleIn: Resolver[F, I, (O, I)] =
self.first[I].contramap[I](i => (i, i))
def batch[K, V](implicit ev: Set[K] =:= I, ev2: O =:= Map[K, V]): ResolverBatchOps[F, K, V] =
new ResolverBatchOps[F, K, V](self.contramap(ev.apply(_)).map(ev2.apply(_)))
def rethrow[O2](implicit ev: O <:< Ior[String, O2]): Resolver[F, I, O2] =
self.map(ev.apply(_)) andThen (new Resolver(Step.embedError))
}
implicit class ResolverEitherOps[F[_], I, L, R](private val self: Resolver[F, I, Either[L, R]]) extends AnyVal {
def leftThrough[O2](f: Resolver[F, L, L] => Resolver[F, L, O2]): Resolver[F, I, Either[O2, R]] =
self andThen f(Resolver.id[F, L]).choose(Resolver.id[F, R])
def rightThrough[O2](f: Resolver[F, R, R] => Resolver[F, R, O2]): Resolver[F, I, Either[L, O2]] =
self andThen Resolver.id[F, L].choose(f(Resolver.id[F, R]))
}
implicit class ResolverStreamOps[F[_], I, O](private val self: Resolver[F, I, fs2.Stream[F, O]]) extends AnyVal {
def embedStream: Resolver[F, I, O] =
self andThen new Resolver(Step.embedStream)
def embedSequentialStream: Resolver[F, I, O] =
self andThen new Resolver(Step.embedStreamFull(signal = false))
}
implicit class ResolverBatchOps[F[_], K, V](private val r: Resolver[F, Set[K], Map[K, V]]) extends AnyVal {
def all[G[_]: Foldable: Functor]: Resolver[F, G[K], G[Option[V]]] =
r.contramap[G[K]](_.toList.toSet).tupleIn.map { case (m, g) => g.map(m.get) }
def traversable[G[_]: Traverse](implicit
S: ShowMissingKeys[K]
): Resolver[F, G[K], G[V]] =
r.contramap[G[K]](_.toList.toSet).tupleIn.emap { case (m, gks) =>
gks
.traverse(k => m.get(k).toValidNel(k))
.leftMap(S.showMissingKeys(_))
.toIor
}
def opt: Resolver[F, K, Option[V]] = all[Id]
def one(implicit S: ShowMissingKeys[K]): Resolver[F, K, V] =
traversable[Id]
}
}
trait ShowMissingKeys[A] {
def showMissingKeys(xs: NonEmptyList[A]): String
}
object ShowMissingKeys {
def apply[A](implicit ev: ShowMissingKeys[A]): ShowMissingKeys[A] = ev
def showFull[A](show: NonEmptyList[A] => String): ShowMissingKeys[A] =
new ShowMissingKeys[A] {
def showMissingKeys(xs: NonEmptyList[A]): String = show(xs)
}
def showForKey[A: Show](prefix: String): ShowMissingKeys[A] =
showFull(xs => s"$prefix: ${xs.map(_.show).mkString_(", ")}")
def show[A](showKey: A => String, prefix: String): ShowMissingKeys[A] =
showForKey[A](prefix)(Show.show(showKey))
}
trait ResolverInstances {
import cats.arrow._
implicit def arrowChoiceForResolver[F[_]]: ArrowChoice[Resolver[F, *, *]] = new ArrowChoice[Resolver[F, *, *]] {
override def choose[A, B, C, D](f: Resolver[F, A, C])(g: Resolver[F, B, D]): Resolver[F, Either[A, B], Either[C, D]] =
f.choose(g)
override def compose[A, B, C](f: Resolver[F, B, C], g: Resolver[F, A, B]): Resolver[F, A, C] =
f.compose(g)
override def first[A, B, C](fa: Resolver[F, A, B]): Resolver[F, (A, C), (B, C)] =
fa.first[C]
override def lift[A, B](f: A => B): Resolver[F, A, B] = Resolver.lift(f)
}
implicit def applicativeForResolver[F[_], I]: Applicative[Resolver[F, I, *]] = new Applicative[Resolver[F, I, *]] {
override def ap[A, B](ff: Resolver[F, I, A => B])(fa: Resolver[F, I, A]): Resolver[F, I, B] =
ff.tupleIn andThen
fa
.contramap[(A => B, I)] { case (_, i) => i }
.tupleIn
.map { case (a, (f, _)) => f(a) }
override def pure[A](x: A): Resolver[F, I, A] =
Resolver.lift(_ => x)
}
}