Add fresh flag to history

Author: pcastornii

mvvm4fx-core/src/main/java/com/techsenger/mvvm4fx/core/AbstractComponentViewModel.java

@@ -51,25 +51,30 @@ public AbstractComponentViewModel() {
             var policy = getHistoryPolicy();
             if (state.get() == ComponentState.CONSTRUCTED) {
                 logger.debug("History policy on constucting: {}", policy);
-                switch (policy) {
-                    case DATA:
-                        getOrRequestHistory().restoreData(this);
-                        postHistoryRestore();
-                        break;
-                    case APPEARANCE:
-                        getOrRequestHistory().restoreAppearance(this);
-                        postHistoryRestore();
-                        break;
-                    case ALL:
-                        var h = getOrRequestHistory();
-                        h.restoreData(this);
-                        h.restoreAppearance(this);
-                        postHistoryRestore();
-                        break;
-                    case NONE:
-                        break;
-                    default:
-                        throw new AssertionError();
+                ComponentHistory history = null;
+                if (policy != NONE) {
+                    history = getOrRequestHistory();
+                    if (history.isFresh()) {
+                        logFreshHistory();
+                    } else {
+                        switch (policy) {
+                            case DATA:
+                                history.restoreData(this);
+                                postHistoryRestore();
+                                break;
+                            case APPEARANCE:
+                                history.restoreAppearance(this);
+                                postHistoryRestore();
+                                break;
+                            case ALL:
+                                history.restoreData(this);
+                                history.restoreAppearance(this);
+                                postHistoryRestore();
+                            break;
+                            default:
+                                throw new AssertionError();
+                        }
+                    }
                 }
             } else if (state.get() == ComponentState.DEINITIALIZED) {
                 logger.debug("History policy on deinitializing: {}", policy);
@@ -155,4 +160,8 @@ private ComponentHistory getOrRequestHistory() {
         }
         return this.history;
     }
+
+    private void logFreshHistory() {
+        logger.debug("History is fresh. Skipping restoration");
+    }
 }

mvvm4fx-core/src/main/java/com/techsenger/mvvm4fx/core/AbstractHistory.java

@@ -22,6 +22,11 @@
  */
 public abstract class AbstractHistory<T extends AbstractComponentViewModel> implements ComponentHistory<T> {
 
+    private boolean fresh = true;
+
+    public boolean isFresh() {
+        return fresh;
+    }
 
     @Override
     public void postDeserialize() {
@@ -40,7 +45,7 @@ public void restoreData(T viewModel) {
 
     @Override
     public void saveData(T viewModel) {
-
+        this.fresh = false;
     }
 
     @Override
@@ -50,6 +55,6 @@ public void restoreAppearance(T viewModel) {
 
     @Override
     public void saveAppearance(T viewModel) {
-
+        this.fresh = false;
     }
 }

mvvm4fx-core/src/main/java/com/techsenger/mvvm4fx/core/ComponentHistory.java

@@ -42,6 +42,18 @@
  */
 public interface ComponentHistory<T extends ComponentViewModel> extends Serializable {
 
+    /**
+     * Returns whether this history instance is fresh, meaning it was newly created and has not yet been used to
+     * save or restore any component state. A fresh history contains no previously stored data and should not be
+     * passed to a component for restoration.
+     *
+     * <p>Once the component's state has been saved into this history, the flag becomes {@code false}, indicating that
+     * the history now holds valid data that can be used to restore the component's state in future instances.
+     *
+     * @return {@code true} if this history is fresh and has not yet been used, {@code false} otherwise
+     */
+    boolean isFresh();
+
     /**
      * Method called before the component is serialized. This can be used to prepare the object's state
      * before saving it in a binary format.