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Alg.scala
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Alg.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.preparation
import gql._
import cats.implicits._
import cats._
import cats.arrow.FunctionK
import cats.data._
import org.typelevel.scalaccompat.annotation._
sealed trait Alg[+C, +A] {
def run[C2 >: C]: EitherNec[PositionalError[C2], A] = Alg.run(this)
}
object Alg {
case object NextId extends Alg[Nothing, Int]
final case class UseVariable(name: String) extends Alg[Nothing, Unit]
final case class UsedVariables() extends Alg[Nothing, Set[String]]
case object CycleAsk extends Alg[Nothing, Set[String]]
final case class CycleOver[C, A](name: String, fa: Alg[C, A]) extends Alg[C, A]
case object CursorAsk extends Alg[Nothing, Cursor]
final case class CursorOver[C, A](cursor: Cursor, fa: Alg[C, A]) extends Alg[C, A]
final case class RaiseError[C](pe: NonEmptyChain[PositionalError[C]]) extends Alg[C, Nothing]
final case class Pure[A](a: A) extends Alg[Nothing, A]
final case class FlatMap[C, A, B](
fa: Alg[C, A],
f: A => Alg[C, B]
) extends Alg[C, B]
final case class ParAp[C, A, B](
fa: Alg[C, A],
fab: Alg[C, A => B]
) extends Alg[C, B]
final case class Attempt[C, A](
fa: Alg[C, A]
) extends Alg[C, EitherNec[PositionalError[C], A]]
implicit def monadErrorForPreparationAlg[C]: MonadError[Alg[C, *], NonEmptyChain[PositionalError[C]]] =
new MonadError[Alg[C, *], NonEmptyChain[PositionalError[C]]] {
override def pure[A](x: A): Alg[C, A] = Ops[C].pure(x)
override def raiseError[A](e: NonEmptyChain[PositionalError[C]]): Alg[C, A] =
Alg.RaiseError(e)
override def handleErrorWith[A](fa: Alg[C, A])(
f: NonEmptyChain[PositionalError[C]] => Alg[C, A]
): Alg[C, A] =
Ops[C].flatMap(Ops[C].attempt(fa)) {
case Left(pe) => f(pe)
case Right(a) => Ops[C].pure(a)
}
override def flatMap[A, B](fa: Alg[C, A])(f: A => Alg[C, B]): Alg[C, B] =
Ops[C].flatMap(fa)(f)
override def tailRecM[A, B](a: A)(f: A => Alg[C, Either[A, B]]): Alg[C, B] =
Ops[C].flatMap(f(a)) {
case Left(a) => tailRecM(a)(f)
case Right(b) => Ops[C].pure(b)
}
}
implicit def parallelForPreparationAlg[C]: Parallel[Alg[C, *]] =
new Parallel[Alg[C, *]] {
type F[A] = Alg[C, A]
override def sequential: F ~> F = FunctionK.id[F]
override def parallel: F ~> F = FunctionK.id[F]
override def applicative: Applicative[F] =
new Applicative[F] {
override def pure[A](x: A): F[A] = Ops[C].pure(x)
override def ap[A, B](ff: F[A => B])(fa: F[A]): F[B] = Ops[C].parAp(fa)(ff)
}
override def monad: Monad[Alg[C, *]] = monadErrorForPreparationAlg[C]
}
def run[C, A](fa: Alg[C, A]): EitherNec[PositionalError[C], A] = {
final case class State(
nextId: Int,
usedVariables: Set[String],
cycleSet: Set[String],
cursor: Cursor
)
sealed trait Outcome[+B] {
def modifyState(f: State => State): Outcome[B]
}
object Outcome {
final case class Result[B](value: B, state: State) extends Outcome[B] {
def modifyState(f: State => State): Outcome[B] = Result(value, f(state))
}
final case class Errors(pe: NonEmptyChain[PositionalError[C]]) extends Outcome[Nothing] {
def modifyState(f: State => State): Outcome[Nothing] = this
}
}
@nowarn3("msg=.*cannot be checked at runtime because its type arguments can't be determined.*")
def go[B](
fa: Alg[C, B],
state: State
): Eval[Outcome[B]] = Eval.defer {
fa match {
case NextId =>
val s = state.copy(nextId = state.nextId + 1)
Eval.now(Outcome.Result(s.nextId, s))
case Pure(a) => Eval.now(Outcome.Result(a, state))
case bind: FlatMap[C, a, B] =>
go[a](bind.fa, state).flatMap {
case Outcome.Errors(pes) => Eval.now(Outcome.Errors(pes))
case Outcome.Result(a, state) => go(bind.f(a), state)
}
case parAp: ParAp[C, a, B] =>
go(parAp.fa, state).flatMap {
case Outcome.Errors(pes1) =>
go(parAp.fab, state).flatMap {
case Outcome.Errors(pes2) => Eval.now(Outcome.Errors(pes1 ++ pes2))
case Outcome.Result(_, _) => Eval.now(Outcome.Errors(pes1))
}
case Outcome.Result(a, state) =>
go(parAp.fab, state).flatMap {
case Outcome.Errors(pes2) => Eval.now(Outcome.Errors(pes2))
case Outcome.Result(f, state) => Eval.now(Outcome.Result(f(a), state))
}
}
case UseVariable(name) =>
Eval.now(Outcome.Result((), state.copy(usedVariables = state.usedVariables + name)))
case UsedVariables() =>
Eval.now(Outcome.Result(state.usedVariables, state))
case CycleAsk =>
Eval.now(Outcome.Result(state.cycleSet, state))
case CycleOver(name, fa) =>
go(fa, state.copy(cycleSet = state.cycleSet + name))
.map(_.modifyState(s => s.copy(cycleSet = s.cycleSet - name)))
case CursorAsk =>
Eval.now(Outcome.Result(state.cursor, state))
case CursorOver(cursor, fa) =>
go(fa, state.copy(cursor = cursor))
.map(_.modifyState(s => s.copy(cursor = s.cursor)))
case re: RaiseError[C] =>
Eval.now(Outcome.Errors(re.pe))
case alg: Attempt[C, a] =>
go(alg.fa, state).flatMap {
case Outcome.Errors(pes) => Eval.now(Outcome.Result(Left(pes), state))
case Outcome.Result(a, state) => Eval.now(Outcome.Result(Right(a), state))
}
}
}
go(fa, State(0, Set.empty, Set.empty, Cursor.empty)).value match {
case Outcome.Errors(pes) => Left(pes)
case Outcome.Result(a, _) => Right(a)
}
}
trait Ops[C] {
def nextId: Alg[C, Int] = Alg.NextId
def useVariable(name: String): Alg[C, Unit] =
Alg.UseVariable(name)
def usedVariables: Alg[C, Set[String]] =
Alg.UsedVariables()
def cycleAsk: Alg[C, Set[String]] = Alg.CycleAsk
def cycleOver[A](name: String, fa: Alg[C, A]): Alg[C, A] =
Alg.CycleOver(name, fa)
def cursorAsk: Alg[C, Cursor] = Alg.CursorAsk
def cursorOver[A](cursor: Cursor, fa: Alg[C, A]): Alg[C, A] =
Alg.CursorOver(cursor, fa)
def raiseError(pe: PositionalError[C]): Alg[C, Nothing] =
Alg.RaiseError(NonEmptyChain.one(pe))
def raise[A](message: String, carets: List[C]): Alg[C, A] =
cursorAsk.flatMap(c => raiseError(PositionalError(c, carets, message)))
def raiseEither[A](e: Either[String, A], carets: List[C]): Alg[C, A] =
e match {
case Left(value) => raise(value, carets)
case Right(value) => pure(value)
}
def raiseOpt[A](oa: Option[A], message: String, carets: List[C]): Alg[C, A] =
raiseEither(oa.toRight(message), carets)
def modifyError[A](f: PositionalError[C] => PositionalError[C])(fa: Alg[C, A]): Alg[C, A] =
attempt(fa).flatMap {
case Right(a) => pure(a)
case Left(pes) => Alg.RaiseError(pes.map(f))
}
def appendMessage[A](message: String)(fa: Alg[C, A]): Alg[C, A] =
modifyError[A](d => d.copy(message = d.message + "\n" + message))(fa)
def pure[A](a: A): Alg[Nothing, A] = Alg.Pure(a)
def flatMap[A, B](fa: Alg[C, A])(f: A => Alg[C, B]): Alg[C, B] =
Alg.FlatMap(fa, f)
def parAp[A, B](fa: Alg[C, A])(fab: Alg[C, A => B]): Alg[C, B] =
Alg.ParAp(fa, fab)
def attempt[A](fa: Alg[C, A]): Alg[C, EitherNec[PositionalError[C], A]] =
Alg.Attempt(fa)
def unit: Alg[C, Unit] = pure(())
def ambientEdge[A](edge: GraphArc)(fa: Alg[C, A]): Alg[C, A] =
cursorAsk.flatMap { cursor =>
cursorOver(cursor.add(edge), fa)
}
def ambientField[A](name: String)(fa: Alg[C, A]): Alg[C, A] =
ambientEdge(GraphArc.Field(name))(fa)
def ambientIndex[A](index: Int)(fa: Alg[C, A]): Alg[C, A] =
ambientEdge(GraphArc.Index(index))(fa)
}
object Ops {
def apply[C] = new Ops[C] {}
}
}