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39 lines
1.4 KiB
39 lines
1.4 KiB
package nova.monadic_sfx.util.reactive
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import cats.implicits._
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import monix.reactive.Observable
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import monix.reactive.ObservableLike
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object Reducer {
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/**
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* Creates a Reducer which yields a new State, as-well as an Observable of Effects
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* Effects are Actions which will be executed after the Action that caused them to occur.
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* This is accomplished by subscribing to the Effects Observable within the stores scan loop.
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*
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* CAUTION: There is currently a bug which causes the Effect-States to emit,
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* before the State of the action that caused the effects is emitted.
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* However, this only effects immediate emissions of the Effects Observable, delayed emissions should be fine.
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* @param f The Reducing Function returning the (Model, Effects) tuple.
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*/
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def withEffects[F[_]: ObservableLike, A, M](
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f: (M, A) => (M, F[A])
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): Reducer[A, M] = (s: M, a: A) => f(s, a).map(ObservableLike[F].apply)
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/**
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* Creates a reducer which just transforms the state, without additional effects.
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*/
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def apply[A, M](f: (M, A) => M): Reducer[A, M] =
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(s: M, a: A) => f(s, a) -> Observable.empty
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/**
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* Creates a Reducer with an optional effect.
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*/
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def withOptionalEffects[F[_]: ObservableLike, A, M](
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f: (M, A) => (M, Option[F[A]])
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): Reducer[A, M] =
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(s: M, a: A) =>
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f(s, a).map(
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_.fold[Observable[A]](Observable.empty)(ObservableLike[F].apply)
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)
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}
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