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/*
* Copyright 2022-2024 John A. De Goes and the ZIO Contributors
*
* 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 zio
/**
* A [[Cached]] is a possibly resourceful value that is loaded into memory, and
* which can be refreshed either manually or automatically.
*/
trait Cached[+Error, +Resource] {
/**
* Retrieves the current value stored in the cache.
*/
def get(implicit trace: Trace): IO[Error, Resource]
/**
* Refreshes the cache. This method will not return until either the refresh
* is successful, or the refresh operation fails.
*/
def refresh(implicit trace: Trace): IO[Error, Unit]
}
object Cached {
/**
* Creates a new [[Cached]] value that is automatically refreshed according to
* the specified policy. Note that error retrying is not performed
* automatically, so if you want to retry on errors, you should first apply
* retry policies to the acquisition effect before passing it to this
* constructor.
*/
def auto[R, Error, Resource](acquire: ZIO[R, Error, Resource], policy: Schedule[Any, Any, Any])(implicit
trace: Trace
): ZIO[R with Scope, Nothing, Cached[Error, Resource]] =
for {
manual <- manual(acquire)
_ <- ZIO.acquireRelease(ZIO.interruptible(manual.refresh.schedule(policy)).forkDaemon)(_.interrupt)
} yield manual
/**
* Creates a new [[Cached]] value that must be manually refreshed by calling
* the refresh method. Note that error retrying is not performed
* automatically, so if you want to retry on errors, you should first apply
* retry policies to the acquisition effect before passing it to this
* constructor.
*/
def manual[R, Error, Resource](
acquire: ZIO[R, Error, Resource]
)(implicit trace: Trace): ZIO[R with Scope, Nothing, Cached[Error, Resource]] =
for {
env <- ZIO.environment[R]
ref <- ScopedRef.fromAcquire(acquire.exit)
} yield Manual(ref, acquire.provideEnvironment(env))
private final case class Manual[Error, Resource](
ref: ScopedRef[Exit[Error, Resource]],
acquire: ZIO[Scope, Error, Resource]
) extends Cached[Error, Resource] {
def get(implicit trace: Trace): IO[Error, Resource] = ref.get.flatMap(ZIO.done(_))
def refresh(implicit trace: Trace): IO[Error, Unit] = ref.set[Any, Error](acquire.map(Exit.succeed(_)))
}
}
