internal.Waitlist.scala Maven / Gradle / Ivy
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/*
* Copyright 2021 Hossein Naderi
*
* 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 lepus.client
package internal
import cats.effect.Concurrent
import cats.effect.kernel.Deferred
import cats.effect.kernel.DeferredSource
import cats.effect.std.Queue
import cats.effect.std.Semaphore
import cats.implicits.*
private[client] trait Waitlist[F[_], T] {
def checkinAnd(eval: F[Unit]): F[DeferredSource[F, T]]
def nextTurn(t: T): F[Boolean]
}
private[client] object Waitlist {
def apply[F[_]: Concurrent, T](size: Int = 100): F[Waitlist[F, T]] = for {
l <- Queue.bounded[F, Deferred[F, T]](size)
sem <- Semaphore[F](1)
} yield new {
def checkinAnd(eval: F[Unit]): F[DeferredSource[F, T]] = for {
d <- Deferred[F, T]
_ <- sem.permit.use(_ => l.offer(d) >> eval)
} yield d
def nextTurn(t: T): F[Boolean] = l.tryTake.flatMap {
case Some(d) => d.complete(t)
case None => false.pure
}
}
}