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package autolift.algebird

import autolift.LiftAp
import com.twitter.algebird.{Functor, Applicative}

trait AlgeLiftAp[Obj, Fn] extends LiftAp[Obj, Fn]

object AlgeLiftAp extends LowPriorityAlgeLiftAp {
	def apply[Obj, Fn](implicit lift: AlgeLiftAp[Obj, Fn]): Aux[Obj, Fn, lift.Out] = lift

	implicit def base[F[_], A, B](implicit ap: Applicative[F]): Aux[F[A], F[A => B], F[B]] =
		new AlgeLiftAp[F[A], F[A => B]]{
			type Out = F[B]

			def apply(fa: F[A], ff: F[A => B]) = ap.joinWith(fa, ff){ (a, f) => f(a) }
		}
}

trait LowPriorityAlgeLiftAp{
	type Aux[Obj, Fn, Out0] = AlgeLiftAp[Obj, Fn]{ type Out = Out0 }

	implicit def recur[F[_], G, Fn](implicit functor: Functor[F], lift: LiftAp[G, Fn]): Aux[F[G], Fn, F[lift.Out]] =
		new AlgeLiftAp[F[G], Fn]{
			type Out = F[lift.Out]

			def apply(fg: F[G], f: Fn) = functor.map(fg){ g: G => lift(g, f) }
		}
}

final class LiftedAp[F[_], A, B](protected val f: F[A => B])(implicit ap: Applicative[F]){
	def andThen[C >: B, D](lf: LiftedAp[F, C, D]) = new LiftedAp(ap.joinWith(f, lf.f){
		(f1, f2) => f1 andThen f2
	})

	def compose[C, D <: A](lf: LiftedAp[F, C, D]) = lf andThen this

	def map[C](g: B => C): LiftedAp[F, A, C] = new LiftedAp(ap.map(f){ _ andThen g })

	def apply[That](that: That)(implicit lift: LiftAp[That, F[A => B]]): lift.Out = lift(that, f)
}

trait LiftedApImplicits{
	implicit def liftedApFunctor[F[_], A] = new Functor[LiftedAp[F, A, ?]]{
		def map[B, C](lap: LiftedAp[F, A, B])(f: B => C) = lap map f
	}
}

trait LiftApContext{
	def liftAp[A, B, F[_]](f: F[A => B])(implicit ap: Applicative[F]) = new LiftedAp(f)
}