From 0b3e54e8ca97a874e3bf25e6e519f23282bab2aa Mon Sep 17 00:00:00 2001
From: Johan Haleby <johan.haleby@gmail.com>
Date: Fri, 17 Nov 2023 17:20:05 +0100
Subject: [PATCH] Decider decideOnEvents can now take multiple commands as
 varargs

---
 .../org/occurrent/dsl/decider/Decider.java    | 40 ++++++++++++++-----
 .../RockPaperScissorsExample.kt               |  9 +----
 2 files changed, 32 insertions(+), 17 deletions(-)

diff --git a/dsl/decider/src/main/java/org/occurrent/dsl/decider/Decider.java b/dsl/decider/src/main/java/org/occurrent/dsl/decider/Decider.java
index 48b418cc3..e0c57d7b2 100644
--- a/dsl/decider/src/main/java/org/occurrent/dsl/decider/Decider.java
+++ b/dsl/decider/src/main/java/org/occurrent/dsl/decider/Decider.java
@@ -20,6 +20,7 @@
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
+import java.util.ArrayList;
 import java.util.List;
 import java.util.function.BiFunction;
 import java.util.function.Predicate;
@@ -36,19 +37,40 @@ default boolean isTerminal(@Nullable S state) {
         return false;
     }
 
-    default Decision<S, E> decideOnEvents(List<E> events, C command) {
-        @Nullable S currentState = fold(initialState(), events);
-        List<E> newEvents = decide(command, currentState);
-        S newState = fold(currentState, newEvents);
-        return new Decision<>(newState, newEvents);
+    @SuppressWarnings("unchecked")
+    default Decision<S, E> decideOnEvents(List<E> events, C command, C... additionalCommands) {
+        BiFunction<List<E>, C, Decision<S, E>> single = (es, c) -> {
+            @Nullable S currentState = fold(initialState(), es);
+            List<E> newEvents = decide(c, currentState);
+            S newState = fold(currentState, newEvents);
+            return new Decision<>(newState, newEvents);
+        };
+
+        Decision<S, E> decisionAfterFirstCommand = single.apply(events, command);
+        final Decision<S, E> finalDecision;
+        if (additionalCommands == null || additionalCommands.length == 0) {
+            finalDecision = decisionAfterFirstCommand;
+        } else {
+            Decision<S, E> decision = decisionAfterFirstCommand;
+            for (C additionalCommand : additionalCommands) {
+                Decision<S, E> thisDecision = single.apply(decision.events, additionalCommand);
+                List<E> accumulatedEvents = new ArrayList<>(decision.events);
+                accumulatedEvents.addAll(thisDecision.events);
+                decision = new Decision<>(thisDecision.state, accumulatedEvents);
+            }
+            finalDecision = decision;
+        }
+        return finalDecision;
     }
 
-    default List<E> decideOnEventsAndReturnEvents(List<E> events, C command) {
-        return decideOnEvents(events, command).events;
+    @SuppressWarnings("unchecked")
+    default List<E> decideOnEventsAndReturnEvents(List<E> events, C command, C... additionalCommands) {
+        return decideOnEvents(events, command, additionalCommands).events;
     }
 
-    default @Nullable S decideOnEventsAndReturnState(List<E> events, C command) {
-        return decideOnEvents(events, command).state;
+    @SuppressWarnings("unchecked")
+    default @Nullable S decideOnEventsAndReturnState(List<E> events, C command, C... additionalCommands) {
+        return decideOnEvents(events, command, additionalCommands).state;
     }
 
     default Decision<S, E> decideOnState(S state, C command) {
diff --git a/example/domain/rps/multiround-decider-model/src/test/kotlin/org/occurrent/example/domain/rps/multirounddecidermodel/RockPaperScissorsExample.kt b/example/domain/rps/multiround-decider-model/src/test/kotlin/org/occurrent/example/domain/rps/multirounddecidermodel/RockPaperScissorsExample.kt
index 89185a0b8..34de91234 100644
--- a/example/domain/rps/multiround-decider-model/src/test/kotlin/org/occurrent/example/domain/rps/multirounddecidermodel/RockPaperScissorsExample.kt
+++ b/example/domain/rps/multiround-decider-model/src/test/kotlin/org/occurrent/example/domain/rps/multirounddecidermodel/RockPaperScissorsExample.kt
@@ -21,7 +21,6 @@ import org.junit.jupiter.api.DisplayName
 import org.junit.jupiter.api.DisplayNameGeneration
 import org.junit.jupiter.api.DisplayNameGenerator
 import org.junit.jupiter.api.Test
-import org.occurrent.dsl.decider.Decider.Decision
 import org.occurrent.dsl.decider.component1
 import org.occurrent.dsl.decider.component2
 import org.occurrent.example.domain.rps.multirounddecidermodel.InitiateNewGame.NumberOfRounds.THREE
@@ -38,7 +37,7 @@ class RockPaperScissorsExample {
         val secondPlayerId = PlayerId.randomUUID()
 
         // When
-        val (state, events) = executeCommands(
+        val (state, events) = rps.decideOnEvents(emptyList(),
             InitiateNewGame(gameId, Timestamp.now(), firstPlayerId, THREE),
 
             ShowHandGesture(gameId, Timestamp.now(), firstPlayerId, HandGesture.PAPER),
@@ -56,10 +55,4 @@ class RockPaperScissorsExample {
         println()
         println("events:\n${events.joinToString("\n")}")
     }
-
-    private fun executeCommands(vararg gameCommands: GameCommand): Decision<GameState, GameEvent> =
-        gameCommands.fold(Decision<GameState, GameEvent>(null, emptyList())) { decision, c ->
-            val (newState, newEvents) = rps.decideOnState(decision.state, c)
-            Decision(newState, decision.events + newEvents)
-        }
 }
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