Multiple small updates and fixes to support all upcoming tests.

- AnyVersionedMap.checkIntegrity added to the superclass
- Default value of the map is gettable.
- Errors fixed:
  - Delta store failed to update reference to the previous transaction in some cases. Fixed in VersionedMapStoreDeltaImpl.java
import java.util.HashMap;
  - Null values caused issues in UncommittedDeltaMapStore.java as putIfAbsent does not work with null.
  - Small fixes in DeltaDiffCursor.java and IteratorAsCursor.java

9 files changed, 107 insertions, 25 deletions

diff --git a/subprojects/store/src/main/java/tools/refinery/store/map/AnyVersionedMap.java b/subprojects/store/src/main/java/tools/refinery/store/map/AnyVersionedMap.java
index f82a8bb1..ead79878 100644
--- a/subprojects/store/src/main/java/tools/refinery/store/map/AnyVersionedMap.java
+++ b/subprojects/store/src/main/java/tools/refinery/store/map/AnyVersionedMap.java
@@ -37,4 +37,9 @@ public sealed interface AnyVersionedMap extends Versioned permits VersionedMap {
         @SuppressWarnings("squid:S1133")
         @Deprecated(since = "0.0.0")
         boolean equals(Object obj);
+
+        /**
+         * Checks the integrity of the map, and throws an exception if an inconsistency is detected.
+         */
+        void checkIntegrity();
 }
diff --git a/subprojects/store/src/main/java/tools/refinery/store/map/VersionedMap.java b/subprojects/store/src/main/java/tools/refinery/store/map/VersionedMap.java
index 31985e94..08ce1dbd 100644
--- a/subprojects/store/src/main/java/tools/refinery/store/map/VersionedMap.java
+++ b/subprojects/store/src/main/java/tools/refinery/store/map/VersionedMap.java
@@ -1,6 +1,8 @@
 package tools.refinery.store.map;
 
 public non-sealed interface VersionedMap<K, V> extends AnyVersionedMap {
+        V getDefaultValue();
+
         V get(K key);
 
         Cursor<K, V> getAll();
diff --git a/subprojects/store/src/main/java/tools/refinery/store/map/VersionedMapStoreDeltaImpl.java b/subprojects/store/src/main/java/tools/refinery/store/map/VersionedMapStoreDeltaImpl.java
index 98dec2bb..e556a8bb 100644
--- a/subprojects/store/src/main/java/tools/refinery/store/map/VersionedMapStoreDeltaImpl.java
+++ b/subprojects/store/src/main/java/tools/refinery/store/map/VersionedMapStoreDeltaImpl.java
@@ -49,21 +49,22 @@ public class VersionedMapStoreDeltaImpl<K, V> implements VersionedMapStore<K, V>
                 return states.get(state);
         }
 
-        public void getPath(long to, List<MapDelta<K, V>[]> forwardTransactions) {
+        public MapTransaction<K, V> getPath(long to, List<MapDelta<K, V>[]> forwardTransactions) {
                 MapTransaction<K, V> toTransaction = getState(to);
                 while (toTransaction != null) {
                         forwardTransactions.add(toTransaction.deltas());
                         toTransaction = toTransaction.parent();
                 }
+                return toTransaction;
         }
 
-        public void getPath(long from, long to,
+        public MapTransaction<K, V> getPath(long from, long to,
                                                 List<MapDelta<K, V>[]> backwardTransactions,
                                                 List<MapDelta<K, V>[]> forwardTransactions) {
                 MapTransaction<K, V> fromTransaction = getState(from);
                 MapTransaction<K, V> toTransaction = getState(to);
                 while (fromTransaction != toTransaction) {
-                        if (fromTransaction == null || fromTransaction.version() < toTransaction.version()) {
+                        if (fromTransaction == null || (toTransaction != null && fromTransaction.version() < toTransaction.version())) {
                                 forwardTransactions.add(toTransaction.deltas());
                                 toTransaction = toTransaction.parent();
                         } else {
@@ -71,6 +72,7 @@ public class VersionedMapStoreDeltaImpl<K, V> implements VersionedMapStore<K, V>
                                 fromTransaction = fromTransaction.parent();
                         }
                 }
+                return toTransaction;
         }
 
 
diff --git a/subprojects/store/src/main/java/tools/refinery/store/map/internal/DeltaDiffCursor.java b/subprojects/store/src/main/java/tools/refinery/store/map/internal/DeltaDiffCursor.java
index 75180bf9..49ea1f67 100644
--- a/subprojects/store/src/main/java/tools/refinery/store/map/internal/DeltaDiffCursor.java
+++ b/subprojects/store/src/main/java/tools/refinery/store/map/internal/DeltaDiffCursor.java
@@ -62,6 +62,7 @@ public class DeltaDiffCursor<K, V> implements DiffCursor<K, V> {
                 return this.direction && listIndex == -1;
         }
 
+
         @Override
         public boolean move() {
                 if (isTerminated()) {
@@ -74,6 +75,7 @@ public class DeltaDiffCursor<K, V> implements DiffCursor<K, V> {
                                 } else {
                                         if (listIndex-1 >= 0) {
                                                 listIndex--;
+                                                arrayIndex = 0;
                                                 return true;
                                         } else {
                                                 listIndex = -1;
diff --git a/subprojects/store/src/main/java/tools/refinery/store/map/internal/IteratorAsCursor.java b/subprojects/store/src/main/java/tools/refinery/store/map/internal/IteratorAsCursor.java
index 4a8e9709..c1a0aec4 100644
--- a/subprojects/store/src/main/java/tools/refinery/store/map/internal/IteratorAsCursor.java
+++ b/subprojects/store/src/main/java/tools/refinery/store/map/internal/IteratorAsCursor.java
@@ -18,7 +18,6 @@ public class IteratorAsCursor<K, V> implements Cursor<K, V> {
         public IteratorAsCursor(VersionedMap<K, V> source, Map<K, V> current) {
                 this.iterator = current.entrySet().iterator();
                 this.source = source;
-                move();
         }
 
         @Override
@@ -38,7 +37,7 @@ public class IteratorAsCursor<K, V> implements Cursor<K, V> {
 
         @Override
         public boolean move() {
-                terminated = iterator.hasNext();
+                terminated = !iterator.hasNext();
                 if (terminated) {
                         this.key = null;
                         this.value = null;
diff --git a/subprojects/store/src/main/java/tools/refinery/store/map/internal/UncommittedDeltaMapStore.java b/subprojects/store/src/main/java/tools/refinery/store/map/internal/UncommittedDeltaMapStore.java
index 73df5080..31423b1c 100644
--- a/subprojects/store/src/main/java/tools/refinery/store/map/internal/UncommittedDeltaMapStore.java
+++ b/subprojects/store/src/main/java/tools/refinery/store/map/internal/UncommittedDeltaMapStore.java
@@ -1,7 +1,6 @@
 package tools.refinery.store.map.internal;
 
-import java.util.HashMap;
-import java.util.Map;
+import java.util.*;
 import java.util.Map.Entry;
 
 import tools.refinery.store.map.VersionedMap;
@@ -16,7 +15,9 @@ public class UncommittedDeltaMapStore<K, V> implements UncommittedDeltaStore<K,
 
         @Override
         public void processChange(K key, V oldValue, V newValue) {
-                this.uncommittedOldValues.putIfAbsent(key, oldValue);
+                if(!uncommittedOldValues.containsKey(key)) {
+                        this.uncommittedOldValues.put(key,oldValue);
+                }
         }
 
         @Override
@@ -25,13 +26,13 @@ public class UncommittedDeltaMapStore<K, V> implements UncommittedDeltaStore<K,
                         return null;
                 } else {
                         @SuppressWarnings("unchecked")
-                        MapDelta<K, V>[] deltas = new MapDelta[uncommittedOldValues.size()];
+                        MapDelta<K,V>[] deltas = new MapDelta[uncommittedOldValues.size()];
                         int i = 0;
                         for (Entry<K, V> entry : uncommittedOldValues.entrySet()) {
                                 final K key = entry.getKey();
                                 final V oldValue = entry.getValue();
                                 final V newValue = source.get(key);
-                                deltas[i] = new MapDelta<>(key, oldValue, newValue);
+                                deltas[i++] = new MapDelta<>(key, oldValue, newValue);
                         }
 
                         return deltas;
diff --git a/subprojects/store/src/main/java/tools/refinery/store/map/internal/UncommittedDeltaStore.java b/subprojects/store/src/main/java/tools/refinery/store/map/internal/UncommittedDeltaStore.java
index 37e5817c..7b017c8e 100644
--- a/subprojects/store/src/main/java/tools/refinery/store/map/internal/UncommittedDeltaStore.java
+++ b/subprojects/store/src/main/java/tools/refinery/store/map/internal/UncommittedDeltaStore.java
@@ -7,4 +7,18 @@ public interface UncommittedDeltaStore<K, V> {
 
         MapDelta<K, V>[] extractAndDeleteDeltas();
 
+        default void checkIntegrity() {
+                MapDelta<K, V>[] extractedDeltas = extractDeltas();
+                if(extractedDeltas != null) {
+                        for(var uncommittedOldValue : extractedDeltas) {
+                                if(uncommittedOldValue == null) {
+                                        throw new IllegalArgumentException("Null entry in deltas!");
+                                }
+                                if(uncommittedOldValue.getKey() == null) {
+                                        throw new IllegalStateException("Null key in deltas!");
+                                }
+                        }
+                }
+        }
+
 }
diff --git a/subprojects/store/src/main/java/tools/refinery/store/map/internal/VersionedMapDeltaImpl.java b/subprojects/store/src/main/java/tools/refinery/store/map/internal/VersionedMapDeltaImpl.java
index 6f2996e1..d09e54ba 100644
--- a/subprojects/store/src/main/java/tools/refinery/store/map/internal/VersionedMapDeltaImpl.java
+++ b/subprojects/store/src/main/java/tools/refinery/store/map/internal/VersionedMapDeltaImpl.java
@@ -19,7 +19,7 @@ public class VersionedMapDeltaImpl<K, V> implements VersionedMap<K, V> {
                 this.defaultValue = defaultValue;
 
                 current = new HashMap<>();
-                if(summarizeChanges) {
+                if (summarizeChanges) {
                         this.uncommittedStore = new UncommittedDeltaMapStore<>(this);
                 } else {
                         this.uncommittedStore = new UncommittedDeltaArrayStore<>();
@@ -27,6 +27,11 @@ public class VersionedMapDeltaImpl<K, V> implements VersionedMap<K, V> {
         }
 
         @Override
+        public V getDefaultValue() {
+                return defaultValue;
+        }
+
+        @Override
         public long commit() {
                 MapDelta<K, V>[] deltas = uncommittedStore.extractAndDeleteDeltas();
                 long[] versionContainer = new long[1];
@@ -43,16 +48,18 @@ public class VersionedMapDeltaImpl<K, V> implements VersionedMap<K, V> {
                 }
 
                 // 2. get common ancestor
+                final MapTransaction<K,V> parent;
                 List<MapDelta<K, V>[]> forward = new ArrayList<>();
                 if (this.previous == null) {
-                        this.store.getPath(state, forward);
+                        parent = this.store.getPath(state, forward);
                         this.forward(forward);
                 } else {
                         List<MapDelta<K, V>[]> backward = new ArrayList<>();
-                        this.store.getPath(this.previous.version(), state, backward, forward);
+                        parent = this.store.getPath(this.previous.version(), state, backward, forward);
                         this.backward(backward);
                         this.forward(forward);
                 }
+                this.previous = parent;
         }
 
         protected void forward(List<MapDelta<K, V>[]> changes) {
@@ -70,14 +77,28 @@ public class VersionedMapDeltaImpl<K, V> implements VersionedMap<K, V> {
         protected void forward(MapDelta<K, V>[] changes) {
                 for (int i = 0; i < changes.length; i++) {
                         final MapDelta<K, V> change = changes[i];
-                        current.put(change.getKey(), change.getNewValue());
+                        K key = change.getKey();
+                        V newValue = change.getNewValue();
+
+                        if(newValue == defaultValue) {
+                                current.remove(key);
+                        } else {
+                                current.put(key,newValue);
+                        }
                 }
         }
 
         protected void backward(MapDelta<K, V>[] changes) {
                 for (int i = changes.length - 1; i >= 0; i--) {
                         final MapDelta<K, V> change = changes[i];
-                        current.put(change.getKey(), change.getOldValue());
+                        K key = change.getKey();
+                        V oldValue = change.oldValue();
+
+                        if(oldValue == defaultValue) {
+                                current.remove(key);
+                        } else {
+                                current.put(key,oldValue);
+                        }
                 }
         }
 
@@ -93,26 +114,46 @@ public class VersionedMapDeltaImpl<K, V> implements VersionedMap<K, V> {
 
         @Override
         public V put(K key, V value) {
-                if (value == defaultValue) {
-                        V res = current.remove(key);
+                final V oldValue;
+                if (Objects.equals(value, defaultValue)) {
+                        final V res = current.remove(key);
                         if (res == null) {
-                                // no changes
-                                return defaultValue;
+                                // no changes: default > default
+                                oldValue = defaultValue;
                         } else {
-                                uncommittedStore.processChange(key, res, value);
-                                return res;
+                                oldValue = res;
                         }
                 } else {
-                        V oldValue = current.put(key, value);
+                        final var mapValue = current.put(key, value);
+                        if (mapValue == null) {
+                                oldValue = defaultValue;
+                        } else {
+                                oldValue = mapValue;
+                        }
+                }
+                if(!Objects.equals(oldValue,value)) {
                         uncommittedStore.processChange(key, oldValue, value);
-                        return oldValue;
                 }
+                return oldValue;
         }
 
         @Override
         public void putAll(Cursor<K, V> cursor) {
-                throw new UnsupportedOperationException();
-
+                if (cursor.getDependingMaps().contains(this)) {
+                        List<K> keys = new ArrayList<>();
+                        List<V> values = new ArrayList<>();
+                        while (cursor.move()) {
+                                keys.add(cursor.getKey());
+                                values.add(cursor.getValue());
+                        }
+                        for (int i = 0; i < keys.size(); i++) {
+                                this.put(keys.get(i), values.get(i));
+                        }
+                } else {
+                        while (cursor.move()) {
+                                this.put(cursor.getKey(), cursor.getValue());
+                        }
+                }
         }
 
         @Override
@@ -156,4 +197,18 @@ public class VersionedMapDeltaImpl<K, V> implements VersionedMap<K, V> {
                         throw new UnsupportedOperationException("Comparing different map implementations is ineffective.");
                 }
         }
+
+        @Override
+        public void checkIntegrity() {
+                this.uncommittedStore.checkIntegrity();
+
+                for (var entry : this.current.entrySet()) {
+                        var value = entry.getValue();
+                        if (value == this.defaultValue) {
+                                throw new IllegalStateException("Default value stored in map!");
+                        } else if (value == null) {
+                                throw new IllegalStateException("null value stored in map!");
+                        }
+                }
+        }
 }
diff --git a/subprojects/store/src/main/java/tools/refinery/store/map/internal/VersionedMapImpl.java b/subprojects/store/src/main/java/tools/refinery/store/map/internal/VersionedMapImpl.java
index 674ffc47..fb359431 100644
--- a/subprojects/store/src/main/java/tools/refinery/store/map/internal/VersionedMapImpl.java
+++ b/subprojects/store/src/main/java/tools/refinery/store/map/internal/VersionedMapImpl.java
@@ -43,6 +43,7 @@ public class VersionedMapImpl<K, V> implements VersionedMap<K, V> {
                 this.root = data;
         }
 
+        @Override
         public V getDefaultValue() {
                 return defaultValue;
         }
@@ -141,6 +142,7 @@ public class VersionedMapImpl<K, V> implements VersionedMap<K, V> {
                 }
         }
 
+        @Override
         public void checkIntegrity() {
                 if (this.root != null) {
                         this.root.checkIntegrity(hashProvider, defaultValue, 0);