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Just playing around with the concept of Feature Flagging w/ZIO
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| package com.alterationx10 | |
| import com.alterationx10.ZFlag.ZIOFeatureFlag | |
| import zio._ | |
| // PSA, just a POC - bad code ahead :-) | |
| // ZIO 2.0.0-RC6 for this... | |
| // Feature flagging service, mainly driven by Ref[Set[String]]... | |
| trait FeatureFlag { | |
| def enabledFeatures: UIO[Set[String]] | |
| def isEnabled(feat: String): UIO[Boolean] | |
| def disableFeature(feat: String): UIO[Set[String]] | |
| def enableFeature(feat: String): UIO[Set[String]] | |
| def loadFeatures(feats: Set[String]): UIO[Unit] | |
| def disableAll(feats: Set[String]): UIO[Unit] | |
| } | |
| case class FeatureFlagLive(private val featRef: Ref[Set[String]]) extends FeatureFlag { | |
| override def enabledFeatures: UIO[Set[String]] = | |
| featRef.get | |
| override def isEnabled(feat: String): UIO[Boolean] = | |
| featRef.get.map(_.contains(feat)) | |
| override def disableFeature(feat: String): UIO[Set[String]] = | |
| featRef.getAndUpdate(_.filterNot(_ == feat)) | |
| override def enableFeature(feat: String): UIO[Set[String]] = | |
| featRef.getAndUpdate(_ + feat) | |
| override def loadFeatures(feats: Set[String]): UIO[Unit] = | |
| featRef.set(feats) | |
| override def disableAll(feats: Set[String]): UIO[Unit] = | |
| featRef.set(Set.empty[String]) | |
| } | |
| object FeatureFlag { | |
| val live: ZLayer[Any, Nothing, FeatureFlag] = ZLayer.fromZIO(for { | |
| ref <- Ref.make(Set.empty[String]) | |
| } yield FeatureFlagLive(ref)) | |
| def disableFeature(feat: String): ZIO[FeatureFlag, Nothing, Set[String]] = | |
| ZIO.serviceWithZIO[FeatureFlag](_.disableFeature(feat)) | |
| def enableFeature(feat: String): ZIO[FeatureFlag, Nothing, Set[String]] = | |
| ZIO.serviceWithZIO[FeatureFlag](_.enableFeature(feat)) | |
| def isEnabled(feat: String): ZIO[FeatureFlag, Nothing, Boolean] = | |
| ZIO.serviceWithZIO[FeatureFlag](_.isEnabled(feat)) | |
| } | |
| object ZFlag { | |
| // TODO need politely indicate that R need FeatureFlag, vs the `with FeatureFlag` that's hacked in. | |
| // Extension to work on our ZIO | |
| implicit final class ZIOFeatureFlag[R, E, A](private val io: ZIO[R, E, A]) extends AnyVal { | |
| def whenFlag(feat: String, alt: ZIO[R with FeatureFlag, E, A]): ZIO[R with FeatureFlag, E, A] = { | |
| new Flagged[R, E](feat).apply(default = io, onEnabled = alt) | |
| } | |
| } | |
| final class Flagged[R, E](private val f: String) extends AnyVal { | |
| def apply[R1 <: R with FeatureFlag, E1 <: E, A](default: => ZIO[R1, E1, A], onEnabled: => ZIO[R1, E1, A]) | |
| : ZIO[R1, E1, A] = { | |
| ZIO.ifZIO(FeatureFlag.isEnabled(f))( | |
| onTrue = onEnabled, | |
| onFalse = default | |
| ) | |
| } | |
| } | |
| } | |
| object FlaggedApp extends zio.ZIOAppDefault { | |
| val impl1: ZIO[Console, Throwable, Unit] = Console.printLine("defaultImpl") | |
| val impl2: ZIO[Console, Throwable, Unit] = Console.printLine("flaggedImpl") | |
| val program: ZIO[Console with FeatureFlag, Throwable, ExitCode] = for { | |
| // no features enabled | |
| _ <- impl1.whenFlag("feat1", impl2) | |
| _ <- FeatureFlag.enableFeature("feat1") | |
| _ <- impl1.whenFlag("feat1", impl2) | |
| _ <- FeatureFlag.disableFeature("feat1") | |
| _ <- impl1.whenFlag("feat1", impl2) | |
| } yield ExitCode.success | |
| override def run: ZIO[Any with ZIOAppArgs with Scope, Any, Any] = | |
| program.provideSome(Console.live ++ FeatureFlag.live) | |
| } |
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