Make Event a sealed interface instead

Java has proper sum types now. We should use them. This requires
language level 21.

Author: emichael

framework/tst-self/dslabs/framework/testing/utils/CloningTest.java

@@ -416,17 +416,13 @@ public void serializableTraces()
       throws InvocationTargetException, InstantiationException, IllegalAccessException {
     List<Event> es = new ArrayList<>();
     es.add(
-        new Event(
-            new MessageEnvelope(
-                new LocalAddress("foo"),
-                new AddressExample("bar"),
-                new MessageExample("asdf", false))));
+        new MessageEnvelope(
+            new LocalAddress("foo"), new AddressExample("bar"), new MessageExample("asdf", false)));
     es.add(
-        new Event(
-            new MessageEnvelope(
-                new LocalAddress("asdf"),
-                new AddressExample("1234"),
-                new MessageExample("baz", false))));
+        new MessageEnvelope(
+            new LocalAddress("asdf"),
+            new AddressExample("1234"),
+            new MessageExample("baz", false)));
 
     var con = SerializableTrace.class.getDeclaredConstructors()[0];
     con.setAccessible(true);

framework/tst/dslabs/framework/testing/Event.java

@@ -24,54 +24,17 @@
 
 import dslabs.framework.Address;
 import java.io.Serializable;
-import lombok.EqualsAndHashCode;
-import lombok.Getter;
 
 /**
  * Represents either a timer to fire or a message to deliver.
  *
  * @see dslabs.framework.testing.search.SearchState
  * @see dslabs.framework.testing.runner.RunState
  */
-@Getter
-@EqualsAndHashCode
-public class Event implements Serializable {
-  // invariant: exactly one of the {message, timer} fields is null
-  private final MessageEnvelope message;
-  private final TimerEnvelope timer;
+public sealed interface Event extends Serializable permits MessageEnvelope, TimerEnvelope {
+  Address locationRootAddress();
 
-  public Event(MessageEnvelope messageEnvelope) {
-    this.message = messageEnvelope;
-    this.timer = null;
-  }
+  boolean isMessage();
 
-  public Event(TimerEnvelope timer) {
-    this.message = null;
-    this.timer = timer;
-  }
-
-  public boolean isMessage() {
-    return message != null;
-  }
-
-  public boolean isTimer() {
-    return timer != null;
-  }
-
-  public Address locationRootAddress() {
-    if (isMessage()) {
-      return message.to().rootAddress();
-    } else {
-      return timer.to().rootAddress();
-    }
-  }
-
-  @Override
-  public String toString() {
-    if (isMessage()) {
-      return message.toString();
-    } else {
-      return timer.toString();
-    }
-  }
+  boolean isTimer();
 }

framework/tst/dslabs/framework/testing/MessageEnvelope.java

@@ -24,22 +24,26 @@
 
 import dslabs.framework.Address;
 import dslabs.framework.Message;
-import java.io.Serializable;
-import lombok.Data;
+import org.checkerframework.checker.nullness.qual.NonNull;
 
-@Data
-public final class MessageEnvelope implements Serializable {
-  private final Address from, to;
-  private final Message message;
+public record MessageEnvelope(Address from, Address to, Message message) implements Event {
+  @Override
+  public Address locationRootAddress() {
+    return to.rootAddress();
+  }
+
+  @Override
+  public boolean isMessage() {
+    return true;
+  }
 
-  public MessageEnvelope(Address from, Address to, Message message) {
-    this.from = from;
-    this.to = to;
-    this.message = message;
+  @Override
+  public boolean isTimer() {
+    return false;
   }
 
   @Override
-  public String toString() {
+  public @NonNull String toString() {
     return String.format("Message(%s -> %s, %s)", from, to, message);
   }
 }

framework/tst/dslabs/framework/testing/TimerEnvelope.java

@@ -25,10 +25,10 @@
 import dslabs.framework.Address;
 import dslabs.framework.Timer;
 import dslabs.framework.VizIgnore;
-import java.io.Serializable;
 import java.util.Random;
 import lombok.Data;
 import lombok.EqualsAndHashCode;
+import org.checkerframework.checker.nullness.qual.NonNull;
 
 /**
  * Stores a timer, its delivery address, its duration, and its creation time. Equality is based on
@@ -38,7 +38,7 @@
  */
 @Data
 @EqualsAndHashCode(of = {"to", "timer", "minTimerLengthMillis", "maxTimerLengthMillis"})
-public final class TimerEnvelope implements Serializable, Comparable<TimerEnvelope> {
+public final class TimerEnvelope implements Event, Comparable<TimerEnvelope> {
   private static final Random rand = new Random();
 
   private final Address to;
@@ -69,6 +69,21 @@ public TimerEnvelope(
     this.startTimeNanos = System.nanoTime();
   }
 
+  @Override
+  public Address locationRootAddress() {
+    return to.rootAddress();
+  }
+
+  @Override
+  public boolean isMessage() {
+    return false;
+  }
+
+  @Override
+  public boolean isTimer() {
+    return true;
+  }
+
   public long endTimeNanos() {
     return startTimeNanos + (((long) timerLengthMillis()) * 1000000);
   }
@@ -82,7 +97,7 @@ public boolean isDue() {
   }
 
   @Override
-  public int compareTo(TimerEnvelope o) {
+  public int compareTo(@NonNull TimerEnvelope o) {
     if (o == null) {
       return 1;
     }

framework/tst/dslabs/framework/testing/runner/Network.java

@@ -102,13 +102,13 @@ Event take() throws InterruptedException {
         newTimerEndTime.set(Long.MAX_VALUE);
         TimerEnvelope te = timers.peek();
         if (te != null && te.isDue()) {
-          return new Event(timers.poll());
+          return timers.poll();
         }
 
         newMessageAvailable = false;
         MessageEnvelope me = messages.poll();
         if (me != null) {
-          return new Event(me);
+          return me;
         }
 
         // Wait for new message or timer
@@ -129,7 +129,7 @@ Event take() throws InterruptedException {
           long endTime = te.endTimeNanos();
           long waitTime = endTime - System.nanoTime();
           if (waitTime <= MIN_WAIT_TIME_NANOS) {
-            return new Event(timers.poll());
+            return timers.poll();
           }
 
           synchronized (this) {

framework/tst/dslabs/framework/testing/runner/RunState.java

@@ -139,17 +139,16 @@ private void runNode(Address address, Node node, Inbox inbox) {
         break;
       }
 
-      if (item.isMessage()) {
-        MessageEnvelope me = item.message();
-        if (settings.shouldDeliver(me)) {
-          node.handleMessage(me.message(), me.from(), me.to());
+      switch (item) {
+        case MessageEnvelope me -> {
+          if (settings.shouldDeliver(me)) {
+            node.handleMessage(me.message(), me.from(), me.to());
+          }
         }
-      }
-
-      if (item.isTimer()) {
-        TimerEnvelope te = item.timer();
-        if (settings.deliverTimers()) {
-          node.onTimer(te.timer(), te.to());
+        case TimerEnvelope te -> {
+          if (settings.deliverTimers()) {
+            node.onTimer(te.timer(), te.to());
+          }
         }
       }
 

framework/tst/dslabs/framework/testing/search/SearchState.java

@@ -235,15 +235,15 @@ Collection<Event> events(SearchSettings settings) {
     // Deliver all possible messages
     for (MessageEnvelope message : network) {
       if (hasNode(message.to().rootAddress()) && settings.shouldDeliver(message)) {
-        events.add(new Event(message));
+        events.add(message);
       }
     }
 
     // Deliver all possible timers
     for (Address address : addresses()) {
       if (settings.deliverTimers(address)) {
         for (TimerEnvelope timer : timers.get(address).deliverable()) {
-          events.add(new Event(timer));
+          events.add(timer);
         }
       }
     }
@@ -273,16 +273,10 @@ Collection<SearchState> step(SearchSettings settings) {
   }
 
   public SearchState stepEvent(Event event, SearchSettings settings, boolean skipChecks) {
-    // TODO: use enum for event type
-
-    if (event.isMessage()) {
-      return stepMessage(event.message(), settings, skipChecks);
-    }
-    if (event.isTimer()) {
-      return stepTimer(event.timer(), settings, skipChecks);
-    }
-
-    return null;
+    return switch (event) {
+      case MessageEnvelope messageEnvelope -> stepMessage(messageEnvelope, settings, skipChecks);
+      case TimerEnvelope timerEnvelope -> stepTimer(timerEnvelope, settings, skipChecks);
+    };
   }
 
   public SearchState stepMessage(
@@ -299,7 +293,7 @@ public SearchState stepMessage(
       return null;
     }
 
-    SearchState ns = new SearchState(this, toAddress, new Event(message));
+    SearchState ns = new SearchState(this, toAddress, message);
     Message nm = Cloning.clone(message.message());
     Node n = ns.node(toAddress);
 
@@ -355,7 +349,7 @@ public SearchState stepTimer(TimerEnvelope timer, SearchSettings settings, boole
       return null;
     }
 
-    SearchState ns = new SearchState(this, toAddress, new Event(timer));
+    SearchState ns = new SearchState(this, toAddress, timer);
     Timer nt = Cloning.clone(timer.timer());
     Node n = ns.node(toAddress);
 
@@ -397,8 +391,7 @@ class GraphNode {
       Event event = state.previousEvent;
       GraphNode node = new GraphNode(event);
 
-      if (event.isMessage()) {
-        MessageEnvelope me = event.message();
+      if (event instanceof MessageEnvelope me) {
         if (whenSent.containsKey(me)) {
           GraphNode p = whenSent.get(me);
           p.next.add(node);

framework/tst/dslabs/framework/testing/utils/CheckLogger.java

@@ -25,6 +25,8 @@
 import dslabs.framework.Node;
 import dslabs.framework.testing.ClientWorker;
 import dslabs.framework.testing.Event;
+import dslabs.framework.testing.MessageEnvelope;
+import dslabs.framework.testing.TimerEnvelope;
 import dslabs.framework.testing.Workload;
 import dslabs.framework.testing.search.SearchState;
 import java.util.Map;
@@ -53,15 +55,13 @@ public final class CheckLogger {
   }
 
   private static String methodName(Event event, SearchState state) {
-    String methodName;
-    if (event.isMessage()) {
-      methodName = "handle" + event.message().message().getClass().getSimpleName();
-    } else if (event.isTimer()) {
-      methodName = "on" + event.timer().timer().getClass().getSimpleName();
-    } else {
-      // Don't handle other methods for now
-      return null;
-    }
+    String methodName =
+        switch (event) {
+          case MessageEnvelope messageEnvelope ->
+              "handle" + messageEnvelope.message().getClass().getSimpleName();
+          case TimerEnvelope timerEnvelope ->
+              "on" + timerEnvelope.timer().getClass().getSimpleName();
+        };
 
     Node n = state.node(event.locationRootAddress().rootAddress());
     if (n instanceof ClientWorker) {

framework/tst/dslabs/framework/testing/visualization/EventTreeState.java

@@ -91,8 +91,8 @@ private EventTreeState(@NonNull SearchState state, EventTreeState parent) {
       assert e != null;
       Set<MessageEnvelope> temp = new HashSet<>(parent.undeliveredMessages);
       // Remove this message from the message list
-      if (e.isMessage()) {
-        temp.remove(e.message());
+      if (e instanceof MessageEnvelope) {
+        temp.remove(e);
       }
       temp.addAll(state.newMessages());
       undeliveredMessages = ImmutableSet.copyOf(temp);
@@ -200,7 +200,7 @@ boolean sendsDeliveredMessages() {
         continue;
       }
       Event e = state.previousEvent();
-      if (e.isMessage() && !state.parent().undeliveredMessages().contains(e.message())) {
+      if (e instanceof MessageEnvelope && !state.parent().undeliveredMessages().contains(e)) {
         return true;
       }
     }

framework/tst/dslabs/framework/testing/visualization/EventVisibilityPane.java

@@ -27,6 +27,8 @@
 import dslabs.framework.Message;
 import dslabs.framework.Timer;
 import dslabs.framework.testing.Event;
+import dslabs.framework.testing.MessageEnvelope;
+import dslabs.framework.testing.TimerEnvelope;
 import java.util.Comparator;
 import java.util.Map.Entry;
 import java.util.SortedMap;
@@ -150,7 +152,10 @@ boolean isHidden(Timer t) {
     }
 
     boolean isHidden(Event e) {
-      return e.isMessage() ? isHidden(e.message().message()) : isHidden(e.timer().timer());
+      return switch (e) {
+        case MessageEnvelope messageEnvelope -> isHidden(messageEnvelope.message());
+        case TimerEnvelope timerEnvelope -> isHidden(timerEnvelope.timer());
+      };
     }
   }