merge: Increase minimum Java version to 17 (#115)

This pull request increases the minimum version of Java required by OpenDC to 17.
This new version of Java introduces several new features compared to our old minimum 
version (11), which we attempt to apply in this conversion.

## Implementation Notes :hammer_and_pick:

* Increase minimum Java version to Java 17 
* Use RandomGenerator as randomness source 
* Add common dispatcher interface 
* Add compatibility with Kotlin coroutines
* Use InstantSource as time source
* Re-implement SimulationScheduler as Dispatcher 
* Replace use of CoroutineContext by Dispatcher 

## External Dependencies :four_leaf_clover:

* Java 17

## Breaking API Changes :warning:

* The use of `CoroutineContext` and `Clock` as parameters of classes has been replaced 
  by the `Dispatcher` interface.
* The use of `Clock` has been replaced by `InstantSource` which does not carry time
   zone info.
* The use of `Random` and `SplittableRandom` as parameter type has been replaced 
   by `RandomGenerator`

4 files changed, 18 insertions, 22 deletions

diff --git a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/FlowEngine.java b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/FlowEngine.java
index 0ebb0da9..c0f52505 100644
--- a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/FlowEngine.java
+++ b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/FlowEngine.java
@@ -23,11 +23,11 @@
 package org.opendc.simulator.flow2;
 
 import java.time.Clock;
+import java.time.InstantSource;
 import java.util.ArrayList;
 import java.util.List;
-import kotlin.coroutines.ContinuationInterceptor;
 import kotlin.coroutines.CoroutineContext;
-import kotlinx.coroutines.Delay;
+import org.opendc.common.Dispatcher;
 
 /**
  * A {@link FlowEngine} simulates a generic flow network.
@@ -56,29 +56,25 @@ public final class FlowEngine implements Runnable {
      */
     private boolean active;
 
-    private final CoroutineContext coroutineContext;
-    private final Clock clock;
-    private final Delay delay;
+    private final Dispatcher dispatcher;
+    private final InstantSource clock;
 
     /**
-     * Create a new {@link FlowEngine} instance using the specified {@link CoroutineContext} and {@link Clock}.
+     * Create a new {@link FlowEngine} instance using the specified {@link CoroutineContext} and {@link InstantSource}.
      */
-    public static FlowEngine create(CoroutineContext coroutineContext, Clock clock) {
-        return new FlowEngine(coroutineContext, clock);
+    public static FlowEngine create(Dispatcher dispatcher) {
+        return new FlowEngine(dispatcher);
     }
 
-    FlowEngine(CoroutineContext coroutineContext, Clock clock) {
-        this.coroutineContext = coroutineContext;
-        this.clock = clock;
-
-        CoroutineContext.Key<? extends ContinuationInterceptor> key = ContinuationInterceptor.Key;
-        this.delay = (Delay) coroutineContext.get(key);
+    FlowEngine(Dispatcher dispatcher) {
+        this.dispatcher = dispatcher;
+        this.clock = dispatcher.getTimeSource();
     }
 
     /**
      * Obtain the (virtual) {@link Clock} driving the simulation.
      */
-    public Clock getClock() {
+    public InstantSource getClock() {
         return clock;
     }
 
@@ -204,7 +200,7 @@ public final class FlowEngine implements Runnable {
         // Only schedule a new scheduler invocation in case the target is earlier than all other pending
         // scheduler invocations
         if (scheduled.tryAdd(target)) {
-            delay.invokeOnTimeout(target - now, this, coroutineContext);
+            dispatcher.schedule(target - now, this);
         }
     }
 
diff --git a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/FlowStage.java b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/FlowStage.java
index ed5579ea..25f87e04 100644
--- a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/FlowStage.java
+++ b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/FlowStage.java
@@ -22,7 +22,7 @@
 
 package org.opendc.simulator.flow2;
 
-import java.time.Clock;
+import java.time.InstantSource;
 import java.util.HashMap;
 import java.util.Map;
 import org.slf4j.Logger;
@@ -67,7 +67,7 @@ public final class FlowStage {
      */
     int timerIndex = -1;
 
-    final Clock clock;
+    final InstantSource clock;
     private final FlowStageLogic logic;
     final FlowGraphInternal parentGraph;
     private final FlowEngine engine;
diff --git a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/InPort.java b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/InPort.java
index fba12aaf..16fed4eb 100644
--- a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/InPort.java
+++ b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/InPort.java
@@ -22,7 +22,7 @@
 
 package org.opendc.simulator.flow2;
 
-import java.time.Clock;
+import java.time.InstantSource;
 import java.util.Objects;
 
 /**
@@ -40,7 +40,7 @@ public final class InPort implements Inlet {
 
     OutPort output;
     private InHandler handler = InHandlers.noop();
-    private final Clock clock;
+    private final InstantSource clock;
     private final String name;
     private final FlowStage stage;
 
diff --git a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/OutPort.java b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/OutPort.java
index 332296a0..1f7ed4ee 100644
--- a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/OutPort.java
+++ b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/OutPort.java
@@ -22,7 +22,7 @@
 
 package org.opendc.simulator.flow2;
 
-import java.time.Clock;
+import java.time.InstantSource;
 import java.util.Objects;
 
 /**
@@ -42,7 +42,7 @@ public final class OutPort implements Outlet {
     private OutHandler handler = OutHandlers.noop();
     private final String name;
     private final FlowStage stage;
-    private final Clock clock;
+    private final InstantSource clock;
 
     OutPort(FlowStage stage, String name, int id) {
         this.name = name;