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endless.core.interpret.EntityTLiftInstance.scala Maven / Gradle / Ivy
package endless.core.interpret
import cats.Monad
import cats.conversions.all.*
import cats.data.NonEmptyChain
import cats.syntax.applicative.*
import cats.syntax.either.*
import cats.syntax.flatMap.*
import cats.syntax.functor.*
import endless.core.entity.Entity
class EntityTLiftInstance[F[_], S, E](implicit fMonad: Monad[F])
extends Entity[EntityT[F, S, E, *], S, E]
with Monad[EntityT[F, S, E, *]] {
implicit lazy val monad: Monad[EntityT[F, S, E, *]] = new Monad[EntityT[F, S, E, *]] {
def pure[A](x: A): EntityT[F, S, E, A] = EntityT.purr(x)
def flatMap[A, B](fa: EntityT[F, S, E, A])(f: A => EntityT[F, S, E, B]): EntityT[F, S, E, B] =
fa.flatMap(f)
def tailRecM[A, B](a: A)(f: A => EntityT[F, S, E, Either[A, B]]): EntityT[F, S, E, B] =
new EntityT[F, S, E, B]((folder, events) =>
fMonad.tailRecM((events, a)) { case (events, a) =>
f(a).runAcc(folder, events).flatMap {
case Right((nextEvents, Left(nextA))) =>
f(nextA).runAcc(folder, nextEvents).map {
case Right((nextNextEvents, Left(a))) =>
(nextNextEvents, a).asLeft // we keep digging
case Right((nextNextEvents, Right(b))) => (nextNextEvents, b).asRight.asRight
case Left(invalidFoldReason) => invalidFoldReason.asLeft.asRight
}
case Right((nextEvents, Right(b))) => (nextEvents, b).asRight.asRight.pure[F]
case Left(invalidFoldReason) => invalidFoldReason.asLeft.asRight.pure[F]
}
}
)
}
override def read: EntityT[F, S, E, Option[S]] = EntityT.reader[F, S, E]
override def write(event: E, other: E*): EntityT[F, S, E, Unit] =
EntityT.writer(NonEmptyChain(event, other *))
def pure[A](x: A): EntityT[F, S, E, A] = monad.pure(x)
def flatMap[A, B](fa: EntityT[F, S, E, A])(f: A => EntityT[F, S, E, B]): EntityT[F, S, E, B] =
monad.flatMap(fa)(f)
def tailRecM[A, B](a: A)(f: A => EntityT[F, S, E, Either[A, B]]): EntityT[F, S, E, B] =
monad.tailRecM(a)(f)
}
