Implement Multi-Step Undo

forge-game/src/main/java/forge/game/Game.java

@@ -97,8 +97,10 @@ public class Game {
     public boolean EXPERIMENTAL_RESTORE_SNAPSHOT = false;
     // While this is false here, its really set by the Match/Preferences
 
-    // If this merges with LKI In the future, it will need to change forms
     private GameSnapshot previousGameState = null;
+    private GameSnapshot pendingSnapshot = null;
+    private final Deque<GameSnapshot> undoStack = new ArrayDeque<>();
+    private static final int MAX_UNDO_DEPTH = 10;
     private CardCollection lastStateBattlefield = new CardCollection();
     private CardCollection lastStateGraveyard = new CardCollection();
 
@@ -186,23 +188,49 @@ public CardCollectionView getLastStateGraveyard() {
     }
 
     public void stashGameState() {
-        // Take a snapshot of the current state to restore to previous state
+        // Save a pending snapshot before the player chooses an action
         if (EXPERIMENTAL_RESTORE_SNAPSHOT) {
-            previousGameState = new GameSnapshot(this);
-            previousGameState.makeCopy();
+            pendingSnapshot = new GameSnapshot(this);
+            pendingSnapshot.makeCopy();
+        }
+    }
+
+    public void commitGameState() {
+        // Push the pending snapshot onto the undo stack (called after a successful action)
+        if (pendingSnapshot != null) {
+            undoStack.push(pendingSnapshot);
+            pendingSnapshot = null;
+            if (undoStack.size() > MAX_UNDO_DEPTH) {
+                undoStack.removeLast();
+            }
         }
     }
 
     public boolean restoreGameState() {
-        // Restore game state snapshot
-        if (previousGameState == null || !EXPERIMENTAL_RESTORE_SNAPSHOT) {
+        // Restore from pending snapshot only (used for rollback of a failed spell/ability).
+        // This must NOT fall through to the undo stack — that's for deliberate user undo only.
+        if (!EXPERIMENTAL_RESTORE_SNAPSHOT || pendingSnapshot == null) {
             return false;
         }
+        pendingSnapshot.restoreGameState(this);
+        pendingSnapshot = null;
+        return true;
+    }
 
-        previousGameState.restoreGameState(this);
+    public boolean undoToLastSnapshot() {
+        if (!EXPERIMENTAL_RESTORE_SNAPSHOT || undoStack.isEmpty()) return false;
+        GameSnapshot snapshot = undoStack.pop();
+        snapshot.restoreGameState(this);
+        // Re-stash so the pending snapshot reflects the restored state,
+        // not the pre-undo state that is now stale.
+        stashGameState();
         return true;
     }
 
+    public boolean canUndoToSnapshot() {
+        return EXPERIMENTAL_RESTORE_SNAPSHOT && !undoStack.isEmpty();
+    }
+
     public void copyLastState() {
         lastStateBattlefield.clear();
         lastStateGraveyard.clear();

forge-game/src/main/java/forge/game/phase/PhaseHandler.java

@@ -1083,6 +1083,7 @@ public void mainLoopStep() {
                         // 117.3c If a player has priority when they cast a spell, activate an ability, [play a land]
                         // that player receives priority afterward.
                         pFirstPriority = pPlayerPriority; // all opponents have to pass before stack is allowed to resolve
+                        game.commitGameState(); // push pre-action snapshot onto undo stack
                     } else if (game.EXPERIMENTAL_RESTORE_SNAPSHOT) {
                         rollback = true;
                     }

forge-game/src/main/java/forge/game/player/Player.java

@@ -1109,6 +1109,9 @@ public int getSurveilThisTurn() {
     public void resetSurveilThisTurn() {
         surveilThisTurn = 0;
     }
+    public void setSurveilThisTurn(int n) {
+        surveilThisTurn = n;
+    }
 
     public boolean canMulligan() {
         return !getZone(ZoneType.Hand).isEmpty();
@@ -1278,12 +1281,18 @@ public final void resetNumDrawnThisTurn() {
     public final int getNumDrawnThisTurn() {
         return numDrawnThisTurn;
     }
+    public final void setNumDrawnThisTurn(int n) {
+        numDrawnThisTurn = n;
+    }
     public final int getNumDrawnLastTurn() {
         return numDrawnLastTurn;
     }
     public final int numDrawnThisDrawStep() {
         return numDrawnThisDrawStep;
     }
+    public final void setNumDrawnThisDrawStep(int n) {
+        numDrawnThisDrawStep = n;
+    }
 
     /**
      * Returns PlayerZone corresponding to the given zone of game.
@@ -1405,6 +1414,9 @@ public final void resetNumRollsThisTurn() {
     public final int getNumRollsThisTurn() {
         return numRollsThisTurn;
     }
+    public final void setNumRollsThisTurn(int n) {
+        numRollsThisTurn = n;
+    }
     public void roll() {
         numRollsThisTurn++;
     }
@@ -1415,6 +1427,9 @@ public final void resetNumFlipsThisTurn() {
     public final int getNumFlipsThisTurn() {
         return numFlipsThisTurn;
     }
+    public final void setNumFlipsThisTurn(int n) {
+        numFlipsThisTurn = n;
+    }
     public void flip() {
         numFlipsThisTurn++;
     }
@@ -1463,6 +1478,9 @@ public final void addTokensCreatedThisTurn(Card token) {
     public final int getNumTokenCreatedThisTurn() {
         return numTokenCreatedThisTurn;
     }
+    public final void setNumTokenCreatedThisTurn(int n) {
+        numTokenCreatedThisTurn = n;
+    }
 
     public final void resetNumTokenCreatedThisTurn() {
         numTokenCreatedThisTurn = 0;
@@ -1482,6 +1500,9 @@ public final void addForetoldThisTurn() {
     public final void resetNumForetoldThisTurn() {
         numForetoldThisTurn = 0;
     }
+    public final void setNumForetoldThisTurn(int n) {
+        numForetoldThisTurn = n;
+    }
 
     public final List<Card> getDiscardedThisTurn() {
         return discardedThisTurn;
@@ -1499,6 +1520,9 @@ public final void addExploredThisTurn() {
     public final void resetNumExploredThisTurn() {
         numExploredThisTurn = 0;
     }
+    public final void setNumExploredThisTurn(int n) {
+        numExploredThisTurn = n;
+    }
 
     public int getNumCardsInHandStartedThisTurnWith() {
         return numCardsInHandStartedThisTurnWith;
@@ -1773,7 +1797,7 @@ public final int setNumPowerSurgeLands(final int n) {
     public final Card getLastDrawnCard() {
         return lastDrawnCard;
     }
-    private Card setLastDrawnCard(final Card c) {
+    public Card setLastDrawnCard(final Card c) {
         lastDrawnCard = c;
         return lastDrawnCard;
     }
@@ -1819,6 +1843,9 @@ public final void incrementTurn() {
     public final int getLastTurnNr() {
         return this.lastTurnNr;
     }
+    public final void setLastTurnNr(int n) {
+        this.lastTurnNr = n;
+    }
 
     public boolean hasTappedLandForManaThisTurn() {
         return tappedLandForManaThisTurn;
@@ -1880,6 +1907,9 @@ public final void incrementVenturedThisTurn() {
     public final void resetVenturedThisTurn() {
         venturedThisTurn = 0;
     }
+    public final void setVenturedThisTurn(int n) {
+        venturedThisTurn = n;
+    }
 
     public final List<Card> getCompletedDungeons() {
         return completedDungeons;
@@ -2282,6 +2312,9 @@ public final void addInvestigatedThisTurn() {
     public final void resetInvestigatedThisTurn() {
         investigatedThisTurn = 0;
     }
+    public final void setInvestigatedThisTurn(int n) {
+        investigatedThisTurn = n;
+    }
 
     public final void addSacrificedThisTurn(final Card cpy, final SpellAbility source) {
         // Play the Sacrifice sound
@@ -2340,6 +2373,9 @@ public final void setSpellsCastLastTurn(int num) {
     public final int getSpellsCastThisGame() {
         return spellsCastThisGame;
     }
+    public final void setSpellsCastThisGame(int n) {
+        spellsCastThisGame = n;
+    }
     public final void resetSpellCastThisGame() {
         spellsCastThisGame = 0;
     }
@@ -2361,6 +2397,12 @@ public final void setLifeGainedThisTurn(final int n) {
     public final int getLifeGainedTimesThisTurn() {
         return lifeGainedTimesThisTurn;
     }
+    public final void setLifeGainedTimesThisTurn(int n) {
+        lifeGainedTimesThisTurn = n;
+    }
+    public final void setLifeGainedByTeamThisTurn(int n) {
+        lifeGainedByTeamThisTurn = n;
+    }
 
     public final int getLifeLostThisTurn() {
         return lifeLostThisTurn;
@@ -3397,6 +3439,31 @@ public CardCollectionView getGainedOwnership() {
         return gainedOwnership;
     }
 
+    // === Snapshot support setters ===
+
+    public void setSimultaneousDamage(int n) { simultaneousDamage = n; }
+    public int getSimultaneousDamage() { return simultaneousDamage; }
+    public void setTriedToDrawFromEmptyLibrary(boolean b) { triedToDrawFromEmptyLibrary = b; }
+    public boolean getTriedToDrawFromEmptyLibrary() { return triedToDrawFromEmptyLibrary; }
+
+    public void setDiscardedThisTurn(List<Card> cards) { discardedThisTurn = new ArrayList<>(cards); }
+    public void setSacrificedThisTurn(List<Card> cards) { sacrificedThisTurn = new ArrayList<>(cards); }
+    public void setDiceRollsThisTurn(List<Integer> rolls) { diceRollsThisTurn = new ArrayList<>(rolls); }
+    public List<Card> getSpellsCastSinceBeginningOfLastTurn() { return spellsCastSinceBeginningOfLastTurn; }
+    public void setSpellsCastSinceBeginningOfLastTurn(List<Card> cards) { spellsCastSinceBeginningOfLastTurn = new ArrayList<>(cards); }
+    public void setAttackedThisTurn(Map<GameEntity, List<Card>> map) { attackedThisTurn = new HashMap<>(map); }
+    public Map<GameEntity, List<Card>> getAttackedThisTurn() { return attackedThisTurn; }
+    public void setAttackedPlayersThisCombat(List<Player> players) { attackedPlayersThisCombat = new ArrayList<>(players); }
+    public void setCompletedDungeons(List<Card> dungeons) { completedDungeons = new ArrayList<>(dungeons); }
+    public void setLostOwnership(CardCollection cards) { lostOwnership = new CardCollection(cards); }
+    public void setGainedOwnership(CardCollection cards) { gainedOwnership = new CardCollection(cards); }
+    public void setElementalBendThisTurn(EnumSet<TriggerType> set) { elementalBendThisTurn = set.isEmpty() ? EnumSet.noneOf(TriggerType.class) : EnumSet.copyOf(set); }
+    public EnumSet<TriggerType> getElementalBendThisTurn() { return elementalBendThisTurn; }
+    public void setCurrentPlanes(CardCollection cards) { currentPlanes = new CardCollection(cards); }
+    public CardCollection getCurrentPlanes() { return currentPlanes; }
+    public void setPlaneswalkedToThisTurn(CardCollection cards) { planeswalkedToThisTurn = new CardCollection(cards); }
+    public void setActiveScheme(Card c) { activeScheme = c; }
+
     @Override
     public PlayerView getView() {
         return view;
@@ -3971,6 +4038,9 @@ public void rollToVisitAttractions() {
     public int getAttractionsVisitedThisTurn() {
         return this.attractionsVisitedThisTurn;
     }
+    public void setAttractionsVisitedThisTurn(int n) {
+        this.attractionsVisitedThisTurn = n;
+    }
 
     public int getCrankCounter() {
         return this.crankCounter;
@@ -4049,6 +4119,9 @@ public List<String> getUnlockedDoors() {
     public int getDevotionMod() {
         return devotionMod;
     }
+    public void setDevotionMod(int n) {
+        devotionMod = n;
+    }
 
     public void afterStaticAbilityLayer(StaticAbilityLayer layer) {
         if (layer != StaticAbilityLayer.TEXT) {

forge-game/src/main/java/forge/game/zone/MagicStack.java

@@ -933,9 +933,16 @@ public final boolean hasStateTrigger(final int triggerID) {
     public final List<Card> getSpellsCastThisTurn() {
         return thisTurnCast;
     }
+    public final void setSpellsCastThisTurn(List<Card> cards) {
+        thisTurnCast.clear();
+        thisTurnCast.addAll(cards);
+    }
     public final List<Card> getSpellsCastLastTurn() {
         return lastTurnCast;
     }
+    public final void setSpellsCastLastTurn(List<Card> cards) {
+        lastTurnCast = Lists.newArrayList(cards);
+    }
 
     public final void onNextTurn() {
         final Player active = game.getPhaseHandler().getPlayerTurn();
@@ -962,6 +969,10 @@ public void addAbilityActivatedThisTurn(SpellAbility sa, final Card source) {
     public List<SpellAbility> getAbilityActivatedThisTurn() {
         return thisTurnActivated;
     }
+    public void setAbilityActivatedThisTurn(List<SpellAbility> abilities) {
+        thisTurnActivated.clear();
+        thisTurnActivated.addAll(abilities);
+    }
 
     public final boolean hasSourceOnStack(final Card source, final Predicate<SpellAbility> pred) {
         if (source == null) {

forge-game/src/main/java/forge/game/zone/Zone.java

@@ -85,6 +85,12 @@ public final void reorder(final Card c, final int index) {
         cardList.add(index, c);
     }
 
+    /** Reorder the zone to match the given card list atomically (no empty-zone window). */
+    public final void setCardOrder(List<Card> order) {
+        cardList.clear();
+        cardList.addAll(order);
+    }
+
     public final void add(final Card c) {
         add(c, null);
     }