3 files changed, 50 insertions, 6 deletions
diff --git a/simulator/opendc-simulator/opendc-simulator-resources/src/main/kotlin/org/opendc/simulator/resources/SimResourceFlow.kt b/simulator/opendc-simulator/opendc-simulator-resources/src/main/kotlin/org/opendc/simulator/resources/SimResourceFlow.kt
new file mode 100644
index 00000000..bbf6ad44
--- /dev/null
+++ b/simulator/opendc-simulator/opendc-simulator-resources/src/main/kotlin/org/opendc/simulator/resources/SimResourceFlow.kt
@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.simulator.resources
+
+/**
+ * A [SimResourceFlow] acts as both a resource consumer and resource provider at the same time, simplifying bridging
+ * between different components.
+ */
+public interface SimResourceFlow : SimResourceConsumer, SimResourceProvider
diff --git a/simulator/opendc-simulator/opendc-simulator-resources/src/main/kotlin/org/opendc/simulator/resources/SimResourceSwitchExclusive.kt b/simulator/opendc-simulator/opendc-simulator-resources/src/main/kotlin/org/opendc/simulator/resources/SimResourceSwitchExclusive.kt
index a10f84b6..45e4c220 100644
--- a/simulator/opendc-simulator/opendc-simulator-resources/src/main/kotlin/org/opendc/simulator/resources/SimResourceSwitchExclusive.kt
+++ b/simulator/opendc-simulator/opendc-simulator-resources/src/main/kotlin/org/opendc/simulator/resources/SimResourceSwitchExclusive.kt
@@ -38,7 +38,7 @@ public class SimResourceSwitchExclusive : SimResourceSwitch {
     override val outputs: Set<SimResourceProvider>
         get() = _outputs
 
-    private val availableResources = ArrayDeque<SimResourceForwarder>()
+    private val availableResources = ArrayDeque<SimResourceTransformer>()
 
     private val _inputs = mutableSetOf<SimResourceProvider>()
     override val inputs: Set<SimResourceProvider>
@@ -83,7 +83,7 @@ public class SimResourceSwitchExclusive : SimResourceSwitch {
 
     private inner class Provider(
         private val capacity: Double,
-        private val forwarder: SimResourceForwarder
+        private val forwarder: SimResourceTransformer
     ) : SimResourceProvider by forwarder {
         override fun close() {
             // We explicitly do not close the forwarder here in order to re-use it across output resources.
diff --git a/simulator/opendc-simulator/opendc-simulator-resources/src/main/kotlin/org/opendc/simulator/resources/SimResourceForwarder.kt b/simulator/opendc-simulator/opendc-simulator-resources/src/main/kotlin/org/opendc/simulator/resources/SimResourceTransformer.kt
index 1a05accd..73f18c7c 100644
--- a/simulator/opendc-simulator/opendc-simulator-resources/src/main/kotlin/org/opendc/simulator/resources/SimResourceForwarder.kt
+++ b/simulator/opendc-simulator/opendc-simulator-resources/src/main/kotlin/org/opendc/simulator/resources/SimResourceTransformer.kt
@@ -23,9 +23,15 @@
 package org.opendc.simulator.resources
 
 /**
- * A helper class to construct a [SimResourceProvider] which forwards the requests to a [SimResourceConsumer].
+ * A [SimResourceFlow] that transforms the resource commands emitted by the resource commands to the resource provider.
+ *
+ * @param isCoupled A flag to indicate that the transformer will exit when the resource consumer exits.
+ * @param transform The function to transform the received resource command.
  */
-public class SimResourceForwarder : SimResourceProvider, SimResourceConsumer {
+public class SimResourceTransformer(
+    private val isCoupled: Boolean = false,
+    private val transform: (SimResourceContext, SimResourceCommand) -> SimResourceCommand
+) : SimResourceFlow {
     /**
      * The [SimResourceContext] in which the forwarder runs.
      */
@@ -98,7 +104,7 @@ public class SimResourceForwarder : SimResourceProvider, SimResourceConsumer {
         return if (state == SimResourceState.Stopped) {
             SimResourceCommand.Exit
         } else if (delegate != null) {
-            val command = delegate.onNext(ctx)
+            val command = transform(ctx, delegate.onNext(ctx))
             if (command == SimResourceCommand.Exit) {
                 // Warning: resumption of the continuation might change the entire state of the forwarder. Make sure we
                 // reset beforehand the existing state and check whether it has been updated afterwards
@@ -106,7 +112,7 @@ public class SimResourceForwarder : SimResourceProvider, SimResourceConsumer {
 
                 delegate.onFinish(ctx)
 
-                if (state == SimResourceState.Stopped)
+                if (isCoupled || state == SimResourceState.Stopped)
                     SimResourceCommand.Exit
                 else
                     onNext(ctx)
@@ -154,3 +160,12 @@ public class SimResourceForwarder : SimResourceProvider, SimResourceConsumer {
         }
     }
 }
+
+/**
+ * Constructs a [SimResourceTransformer] that forwards the received resource command with an identity transform.
+ *
+ * @param isCoupled A flag to indicate that the transformer will exit when the resource consumer exits.
+ */
+public fun SimResourceForwarder(isCoupled: Boolean = false): SimResourceTransformer {
+    return SimResourceTransformer(isCoupled) { _, command -> command }
+}