Cache managed resource (#71)

* Add .bsp to .gitignore

* Extract KeySet and MapKey out of Cache

Because they probably going to be shared with ManagedCache

* define interface for a ManagedCache

* Copy/Paste: cache implementation and cache test for managedCache

* Adapt cache implementation and test for ManagedCache

* make ManagedCache.get return Managed[Error, Value] instead of UIO[Managed[Error, Value]]

* Make ManagedCache work on 2.11 and Scala 3

* Fix doc after Adam's review

* fixup! Fix doc after Adam's review

* fixup! Fix doc after Adam's review

Author: strokyl

.gitignore

@@ -408,10 +408,12 @@ project/plugins/project/
 .metals/
 metals.sbt
 .bloop/
+.bsp/
 project/secret
 
 # mdoc
 website/node_modules
 website/build
 website/i18n/en.json
 website/static/api
+

build.sbt

@@ -60,9 +60,10 @@ lazy val zioCache = crossProject(JSPlatform, JVMPlatform, NativePlatform)
   .settings(buildInfoSettings("zio.cache"))
   .settings(
     libraryDependencies ++= Seq(
-      "dev.zio" %% "zio"          % zioVersion,
-      "dev.zio" %% "zio-test"     % zioVersion % Test,
-      "dev.zio" %% "zio-test-sbt" % zioVersion % Test
+      "dev.zio"                %% "zio"                     % zioVersion,
+      "org.scala-lang.modules" %% "scala-collection-compat" % "2.7.0",
+      "dev.zio"                %% "zio-test"                % zioVersion % Test,
+      "dev.zio"                %% "zio-test-sbt"            % zioVersion % Test
     )
   )
   .settings(testFrameworks += new TestFramework("zio.test.sbt.ZTestFramework"))

zio-cache/shared/src/main/scala/zio/cache/Cache.scala

@@ -281,17 +281,6 @@ object Cache {
       }
     }
 
-  /**
-   * A `MapKey` represents a key in the cache. It contains mutable references
-   * to the previous key and next key in the `KeySet` to support an efficient
-   * implementation of a sorted set of keys.
-   */
-  private final class MapKey[Key](
-    val value: Key,
-    var previous: MapKey[Key] = null,
-    var next: MapKey[Key] = null
-  )
-
   /**
    * A `MapValue` represents a value in the cache. A value may either be
    * `Pending` with a `Promise` that will contain the result of computing the
@@ -346,60 +335,4 @@ object Cache {
         new AtomicBoolean(false)
       )
   }
-
-  /**
-   * A `KeySet` is a sorted set of keys in the cache ordered by last access.
-   * For efficiency, the set is implemented in terms of a doubly linked list
-   * and is not safe for concurrent access.
-   */
-  private final class KeySet[Key] {
-    private[this] var head: MapKey[Key] = null
-    private[this] var tail: MapKey[Key] = null
-
-    /**
-     * Adds the specified key to the set.
-     */
-    def add(key: MapKey[Key]): Unit =
-      if (key ne tail) {
-        if (tail ne null) {
-          val previous = key.previous
-          val next     = key.next
-          if (next ne null) {
-            key.next = null
-            if (previous ne null) {
-              previous.next = next
-              next.previous = previous
-            } else {
-              head = next
-              head.previous = null
-            }
-          }
-          tail.next = key
-          key.previous = tail
-          tail = key
-        } else {
-          head = key
-          tail = key
-        }
-      }
-
-    /**
-     * Removes the lowest priority key from the set.
-     */
-    def remove(): MapKey[Key] = {
-      val key = head
-      if (key ne null) {
-        val next = key.next
-        if (next ne null) {
-          key.next = null
-          head = next
-          head.previous = null
-        } else {
-          head = null
-          tail = null
-        }
-      }
-      key
-    }
-  }
 }

zio-cache/shared/src/main/scala/zio/cache/KeySet.scala

@@ -0,0 +1,57 @@
+package zio.cache
+
+/**
+ * A `KeySet` is a sorted set of keys in the cache ordered by last access.
+ * For efficiency, the set is implemented in terms of a doubly linked list
+ * and is not safe for concurrent access.
+ */
+private[cache] final class KeySet[Key] {
+  private[this] var head: MapKey[Key] = null
+  private[this] var tail: MapKey[Key] = null
+
+  /**
+   * Adds the specified key to the set.
+   */
+  def add(key: MapKey[Key]): Unit =
+    if (key ne tail) {
+      if (tail ne null) {
+        val previous = key.previous
+        val next     = key.next
+        if (next ne null) {
+          key.next = null
+          if (previous ne null) {
+            previous.next = next
+            next.previous = previous
+          } else {
+            head = next
+            head.previous = null
+          }
+        }
+        tail.next = key
+        key.previous = tail
+        tail = key
+      } else {
+        head = key
+        tail = key
+      }
+    }
+
+  /**
+   * Removes the lowest priority key from the set.
+   */
+  def remove(): MapKey[Key] = {
+    val key = head
+    if (key ne null) {
+      val next = key.next
+      if (next ne null) {
+        key.next = null
+        head = next
+        head.previous = null
+      } else {
+        head = null
+        tail = null
+      }
+    }
+    key
+  }
+}