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LazyResource.scala
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LazyResource.scala
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/*
* Copyright 2023 Valdemar Grange
*
* 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 gql.relational
import cats._
import cats.implicits._
import cats.effect.std.Hotswap
import cats.effect.std.Mutex
import cats.effect._
trait LazyResource[F[_], A] { self =>
def get: Resource[F, A]
def forceClose: F[Unit]
def mapK[G[_]: MonadCancelThrow](fk: F ~> G)(implicit F: MonadCancelThrow[F]) = new LazyResource[G, A] {
def get = self.get.mapK(fk)
def forceClose = fk(self.forceClose)
}
}
object LazyResource {
def fromResource[F[_], A](res: Resource[F, A])(implicit F: Concurrent[F]): Resource[F, LazyResource[F, A]] =
Hotswap.create[F, A].evalMap { hs =>
Mutex[F].map { mtx =>
new LazyResource[F, A] {
override def forceClose: F[Unit] = hs.clear
override def get: Resource[F, A] =
mtx.lock >>
hs.get.evalMap {
case None => hs.swap(res)
case Some(ses) => F.pure(ses)
}
}
}
}
implicit def functorForLazyResource[F[_]]: Functor[LazyResource[F, *]] = new Functor[LazyResource[F, *]] {
override def map[A, B](fa: LazyResource[F, A])(f: A => B): LazyResource[F, B] = new LazyResource[F, B] {
override def get: Resource[F, B] = fa.get.map(f)
override def forceClose: F[Unit] = fa.forceClose
}
}
}