refactor: replace marker battle events with typed dispatch

src/main/java/sc2002/turnbased/report/ActionEvent.java

@@ -7,65 +7,67 @@
 import sc2002.turnbased.domain.Combatant;
 import sc2002.turnbased.domain.CombatantId;
 
-public class ActionEvent implements BattleEvent {
-    private final CombatantId actorId;
-    private final String actorName;
-    private final String actionName;
-    private final CombatantId targetId;
-    private final String targetName;
-    private final int hpBefore;
-    private final int hpAfter;
-    private final int attackerAttack;
-    private final int targetDefense;
-    private final int damage;
-    private final boolean targetEliminated;
-    private final List<String> statusEffectNotes;
-
-    public ActionEvent(
-        CombatantId actorId,
-        String actorName,
-        String actionName,
-        CombatantId targetId,
-        String targetName,
-        int hpBefore,
-        int hpAfter,
-        int attackerAttack,
-        int targetDefense,
-        int damage,
-        boolean targetEliminated,
-        List<String> statusEffectNotes
-    ) {
-        this.actorId = Objects.requireNonNull(actorId, "actorId");
-        this.actorName = actorName;
-        this.actionName = actionName;
-        this.targetId = Objects.requireNonNull(targetId, "targetId");
-        this.targetName = targetName;
-        this.hpBefore = hpBefore;
-        this.hpAfter = hpAfter;
-        this.attackerAttack = attackerAttack;
-        this.targetDefense = targetDefense;
-        this.damage = damage;
-        this.targetEliminated = targetEliminated;
-        this.statusEffectNotes = List.copyOf(Objects.requireNonNull(statusEffectNotes, "statusEffectNotes"));
+public record ActionEvent(
+    CombatantId actorId,
+    String actorName,
+    String actionName,
+    CombatantId targetId,
+    String targetName,
+    int hpBefore,
+    int hpAfter,
+    int attackerAttack,
+    int targetDefense,
+    int damage,
+    boolean targetEliminated,
+    List<String> statusEffectNotes
+) implements BattleEvent {
+    public ActionEvent {
+        actorId = Objects.requireNonNull(actorId, "actorId");
+        actorName = Objects.requireNonNull(actorName, "actorName");
+        actionName = Objects.requireNonNull(actionName, "actionName");
+        targetId = Objects.requireNonNull(targetId, "targetId");
+        targetName = Objects.requireNonNull(targetName, "targetName");
+        statusEffectNotes = List.copyOf(Objects.requireNonNull(statusEffectNotes, "statusEffectNotes"));
     }
 
     public ActionEvent(Combatant actor, String actionName, Combatant target, AttackResolution attackResolution) {
         this(
-            actor.combatantId(),
-            actor.getName(),
+            requireActor(actor).combatantId(),
+            requireCombatantName(actor, "actor"),
             actionName,
-            target.combatantId(),
-            target.getName(),
-            attackResolution.hpBefore(),
-            attackResolution.hpAfter(),
-            attackResolution.attackUsed(),
-            attackResolution.targetDefense(),
-            attackResolution.damage(),
-            attackResolution.targetEliminated(),
-            StatusEffectReportMapper.toNotes(attackResolution.statusEffectOutcomes())
+            requireTarget(target).combatantId(),
+            requireCombatantName(target, "target"),
+            requireAttackResolution(attackResolution).hpBefore(),
+            requireAttackResolution(attackResolution).hpAfter(),
+            requireAttackResolution(attackResolution).attackUsed(),
+            requireAttackResolution(attackResolution).targetDefense(),
+            requireAttackResolution(attackResolution).damage(),
+            requireAttackResolution(attackResolution).targetEliminated(),
+            StatusEffectReportMapper.toNotes(requireAttackResolution(attackResolution).statusEffectOutcomes())
         );
     }
 
+    private static Combatant requireActor(Combatant actor) {
+        return Objects.requireNonNull(actor, "actor");
+    }
+
+    private static Combatant requireTarget(Combatant target) {
+        return Objects.requireNonNull(target, "target");
+    }
+
+    private static AttackResolution requireAttackResolution(AttackResolution attackResolution) {
+        return Objects.requireNonNull(attackResolution, "attackResolution");
+    }
+
+    private static String requireCombatantName(Combatant combatant, String role) {
+        return Objects.requireNonNull(Objects.requireNonNull(combatant, role).getName(), role + ".name");
+    }
+
+    @Override
+    public <T> T visit(Visitor<T> visitor) {
+        return visitor.onAction(this);
+    }
+
     public CombatantId getActorId() {
         return actorId;
     }

src/main/java/sc2002/turnbased/report/BattleEvent.java

@@ -1,4 +1,19 @@
 package sc2002.turnbased.report;
 
 public interface BattleEvent {
+    <T> T visit(Visitor<T> visitor);
+
+    interface Visitor<T> {
+        T onAction(ActionEvent actionEvent);
+
+        T onNarration(NarrationEvent narrationEvent);
+
+        T onRoundStart(RoundStartEvent roundStartEvent);
+
+        T onRoundSummary(RoundSummaryEvent roundSummaryEvent);
+
+        T onSkippedTurn(SkippedTurnEvent skippedTurnEvent);
+
+        T onStatusEffectReport(StatusEffectReportEvent statusEffectReportEvent);
+    }
 }

src/main/java/sc2002/turnbased/report/CombatantSummary.java

@@ -1,39 +1,24 @@
 package sc2002.turnbased.report;
 
-import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
+import java.util.Objects;
 
 import sc2002.turnbased.domain.CombatantId;
 
-public class CombatantSummary {
-    private final CombatantId combatantId;
-    private final String name;
-    private final int currentHp;
-    private final int maxHp;
-    private final int currentAttack;
-    private final int baseAttack;
-    private final boolean alive;
-    private final List<String> activeStatuses;
-
-    public CombatantSummary(
-        CombatantId combatantId,
-        String name,
-        int currentHp,
-        int maxHp,
-        int currentAttack,
-        int baseAttack,
-        boolean alive,
-        List<String> activeStatuses
-    ) {
-        this.combatantId = combatantId;
-        this.name = name;
-        this.currentHp = currentHp;
-        this.maxHp = maxHp;
-        this.currentAttack = currentAttack;
-        this.baseAttack = baseAttack;
-        this.alive = alive;
-        this.activeStatuses = new ArrayList<>(activeStatuses);
+public record CombatantSummary(
+    CombatantId combatantId,
+    String name,
+    int currentHp,
+    int maxHp,
+    int currentAttack,
+    int baseAttack,
+    boolean alive,
+    List<String> activeStatuses
+) {
+    public CombatantSummary {
+        combatantId = Objects.requireNonNull(combatantId, "combatantId");
+        name = Objects.requireNonNull(name, "name");
+        activeStatuses = List.copyOf(Objects.requireNonNull(activeStatuses, "activeStatuses"));
     }
 
     public CombatantId getCombatantId() {
@@ -65,6 +50,6 @@ public boolean isAlive() {
     }
 
     public List<String> getActiveStatuses() {
-        return Collections.unmodifiableList(activeStatuses);
+        return activeStatuses;
     }
 }

src/main/java/sc2002/turnbased/report/NarrationEvent.java

@@ -1,10 +1,15 @@
 package sc2002.turnbased.report;
 
-public class NarrationEvent implements BattleEvent {
-    private final String text;
+import java.util.Objects;
 
-    public NarrationEvent(String text) {
-        this.text = text;
+public record NarrationEvent(String text) implements BattleEvent {
+    public NarrationEvent {
+        text = Objects.requireNonNull(text, "text");
+    }
+
+    @Override
+    public <T> T visit(Visitor<T> visitor) {
+        return visitor.onNarration(this);
     }
 
     public String getText() {

src/main/java/sc2002/turnbased/report/RoundStartEvent.java

@@ -1,10 +1,9 @@
 package sc2002.turnbased.report;
 
-public class RoundStartEvent implements BattleEvent {
-    private final int roundNumber;
-
-    public RoundStartEvent(int roundNumber) {
-        this.roundNumber = roundNumber;
+public record RoundStartEvent(int roundNumber) implements BattleEvent {
+    @Override
+    public <T> T visit(Visitor<T> visitor) {
+        return visitor.onRoundStart(this);
     }
 
     public int getRoundNumber() {

src/main/java/sc2002/turnbased/report/RoundSummaryEvent.java

@@ -1,31 +1,31 @@
 package sc2002.turnbased.report;
 
-import java.util.ArrayList;
 import java.util.Collections;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 
 import sc2002.turnbased.domain.ItemType;
 
-public class RoundSummaryEvent implements BattleEvent {
-    private final int roundNumber;
-    private final CombatantSummary playerSummary;
-    private final List<CombatantSummary> enemySummaries;
-    private final Map<ItemType, Integer> inventorySnapshot;
-    private final int specialSkillCooldown;
-
-    public RoundSummaryEvent(
-        int roundNumber,
-        CombatantSummary playerSummary,
-        List<CombatantSummary> enemySummaries,
-        Map<ItemType, Integer> inventorySnapshot,
-        int specialSkillCooldown
-    ) {
-        this.roundNumber = roundNumber;
-        this.playerSummary = playerSummary;
-        this.enemySummaries = new ArrayList<>(enemySummaries);
-        this.inventorySnapshot = inventorySnapshot;
-        this.specialSkillCooldown = specialSkillCooldown;
+public record RoundSummaryEvent(
+    int roundNumber,
+    CombatantSummary playerSummary,
+    List<CombatantSummary> enemySummaries,
+    Map<ItemType, Integer> inventorySnapshot,
+    int specialSkillCooldown
+) implements BattleEvent {
+    public RoundSummaryEvent {
+        playerSummary = Objects.requireNonNull(playerSummary, "playerSummary");
+        enemySummaries = List.copyOf(Objects.requireNonNull(enemySummaries, "enemySummaries"));
+        inventorySnapshot = Collections.unmodifiableMap(new LinkedHashMap<>(
+            Objects.requireNonNull(inventorySnapshot, "inventorySnapshot")
+        ));
+    }
+
+    @Override
+    public <T> T visit(Visitor<T> visitor) {
+        return visitor.onRoundSummary(this);
     }
 
     public int getRoundNumber() {
@@ -37,11 +37,11 @@ public CombatantSummary getPlayerSummary() {
     }
 
     public List<CombatantSummary> getEnemySummaries() {
-        return Collections.unmodifiableList(enemySummaries);
+        return enemySummaries;
     }
 
     public Map<ItemType, Integer> getInventorySnapshot() {
-        return Collections.unmodifiableMap(inventorySnapshot);
+        return inventorySnapshot;
     }
 
     public int getSpecialSkillCooldown() {

src/main/java/sc2002/turnbased/report/SkippedTurnEvent.java

@@ -7,17 +7,17 @@
 import sc2002.turnbased.domain.CombatantId;
 import sc2002.turnbased.domain.status.CombatantStatusOutcome;
 
-public class SkippedTurnEvent implements BattleEvent {
-    private final CombatantId combatantId;
-    private final String combatantName;
-    private final String reason;
-    private final List<String> statusEffectNotes;
-
-    public SkippedTurnEvent(CombatantId combatantId, String combatantName, String reason, List<String> statusEffectNotes) {
-        this.combatantId = Objects.requireNonNull(combatantId, "combatantId");
-        this.combatantName = combatantName;
-        this.reason = reason;
-        this.statusEffectNotes = List.copyOf(Objects.requireNonNull(statusEffectNotes, "statusEffectNotes"));
+public record SkippedTurnEvent(
+    CombatantId combatantId,
+    String combatantName,
+    String reason,
+    List<String> statusEffectNotes
+) implements BattleEvent {
+    public SkippedTurnEvent {
+        combatantId = Objects.requireNonNull(combatantId, "combatantId");
+        combatantName = Objects.requireNonNull(combatantName, "combatantName");
+        reason = Objects.requireNonNull(reason, "reason");
+        statusEffectNotes = List.copyOf(Objects.requireNonNull(statusEffectNotes, "statusEffectNotes"));
     }
 
     public static SkippedTurnEvent fromStatusEffectOutcomes(
@@ -34,6 +34,11 @@ public static SkippedTurnEvent fromStatusEffectOutcomes(
         );
     }
 
+    @Override
+    public <T> T visit(Visitor<T> visitor) {
+        return visitor.onSkippedTurn(this);
+    }
+
     public CombatantId getCombatantId() {
         return combatantId;
     }

src/main/java/sc2002/turnbased/report/StatusEffectReportEvent.java

@@ -10,6 +10,11 @@ public record StatusEffectReportEvent(List<String> statusEffectNotes) implements
         statusEffectNotes = List.copyOf(Objects.requireNonNull(statusEffectNotes, "statusEffectNotes"));
     }
 
+    @Override
+    public <T> T visit(Visitor<T> visitor) {
+        return visitor.onStatusEffectReport(this);
+    }
+
     public static StatusEffectReportEvent fromStatusEffectOutcomes(List<CombatantStatusOutcome> statusEffectOutcomes) {
         return new StatusEffectReportEvent(StatusEffectReportMapper.toNotes(statusEffectOutcomes));
     }