ndeg.fetch_sjs0.6_2.12.0.4.0.source-code.cache.scala Maven / Gradle / Ivy

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Simple & Efficient data access for Scala and Scala.js

There is a newer version: 0.5.0

/*
 * Copyright 2016 47 Degrees, LLC. 
 *
 * 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 fetch

/**
  * A `Cache` trait so the users of the library can provide their own cache.
  */
trait DataSourceCache {
  def update[A](k: DataSourceIdentity, v: A): DataSourceCache

  def get[A](k: DataSourceIdentity): Option[A]

  def cacheResults[I, A](results: Map[I, A], ds: DataSource[I, A]): DataSourceCache = {
    results.foldLeft(this)({
      case (acc, (i, a)) => acc.update(ds.identity(i), a)
    })
  }

  def contains(k: DataSourceIdentity): Boolean = get(k).isDefined
}

/**
  * A cache that stores its elements in memory.
  */
case class InMemoryCache(state: Map[DataSourceIdentity, Any]) extends DataSourceCache {
  override def get[A](k: DataSourceIdentity): Option[A] =
    state.get(k).asInstanceOf[Option[A]]

  override def update[A](k: DataSourceIdentity, v: A): InMemoryCache =
    copy(state = state.updated(k, v))
}

object InMemoryCache {
  def empty: InMemoryCache = InMemoryCache(Map.empty[DataSourceIdentity, Any])

  def apply(results: (DataSourceIdentity, Any)*): InMemoryCache =
    InMemoryCache(results.foldLeft(Map.empty[DataSourceIdentity, Any])({
      case (c, (k, v)) => c.updated(k, v)
    }))

  import cats.{Monoid, Semigroup}
  import cats.instances.map._
  import cats.syntax.semigroup._
  implicit val inMemoryCacheMonoid: Monoid[InMemoryCache] = {
    implicit val anySemigroup = new Semigroup[Any] {
      def combine(a: Any, b: Any): Any = b
    }
    new Monoid[InMemoryCache] {
      def empty: InMemoryCache = InMemoryCache.empty
      def combine(c1: InMemoryCache, c2: InMemoryCache): InMemoryCache =
        InMemoryCache(c1.state |+| c2.state)
    }
  }
}