Code smells/refactored to remove broken hierarchy code smell, long method ,decompose conditional and introduce explaining variable (#1120)

* Refactor(Pull-up method):Pull-up toStringValue to StringFilter for hierarchy enhancement

* Extract StringFilterHelper for modularity

* Add applyOnString to StringFilter for polymorphism

* Refactor MigrationManager.doMigrate() with Extract Method, Decompose Conditional, and Introduce Explaining Variable

Author: DhRuva-1509

nitrite/src/main/java/org/dizitart/no2/filters/StringFilter.java

@@ -23,6 +23,8 @@
  * @since 1.0
  */
 public abstract class StringFilter extends ComparableFilter {
+    private final StringFilterHelper helper = new StringFilterHelper();
+
     /**
      * Instantiates a new String filter.
      *
@@ -41,4 +43,15 @@ protected StringFilter(String field, String value) {
     public String getStringValue() {
         return (String) getValue();
     }
+
+    /**
+     * Converts an object to a string safely.
+     * @param obj the object to convert
+     * @return the string representation, or empty if null
+     */
+    protected String toStringValue(Object obj) {
+        return helper.toStringValue(obj);
+    }
+
+    public abstract boolean applyOnString(String value);
 }

nitrite/src/main/java/org/dizitart/no2/filters/StringFilterHelper.java

@@ -0,0 +1,7 @@
+package org.dizitart.no2.filters;
+
+public class StringFilterHelper {
+    public String toStringValue(Object obj) {
+        return obj != null ? obj.toString() : "";
+    }
+}

nitrite/src/main/java/org/dizitart/no2/filters/TextFilter.java

@@ -48,24 +48,34 @@ public class TextFilter extends StringFilter {
         super(field, value);
     }
 
+    @Override
+    public boolean applyOnString(String value) {
+        String searchString = (String) this.getValue();
+        if (searchString.startsWith("*") || searchString.endsWith("*")) {
+            searchString = searchString.replace("*", "");
+        }
+        return value.toLowerCase().contains(searchString.toLowerCase());
+    }
+
+    /**
+     * Applies this filter to a document, checking if the specified field contains the search string.
+     *
+     * @param element the document pair to filter
+     * @return true if the field value contains the search string (case-insensitive), false otherwise
+     * @throws FilterException if the field is not a string
+     */
     @Override
     public boolean apply(Pair<NitriteId, Document> element) {
         notNull(getField(), "field cannot be null");
         notNull(getStringValue(), "search term cannot be null");
-        String searchString = getStringValue();
         Object docValue = element.getSecond().get(getField());
 
         if (!(docValue instanceof String)) {
             throw new FilterException("Text filter can not be applied on non string field " + getField());
         }
 
         String docString = (String) docValue;
-
-        if (searchString.startsWith("*") || searchString.endsWith("*")) {
-            searchString = searchString.replace("*", "");
-        }
-
-        return docString.toLowerCase().contains(searchString.toLowerCase());
+        return applyOnString(docString);
     }
 
     @Override
@@ -194,4 +204,5 @@ private LinkedHashSet<NitriteId> sortedIdsByScore(Map<NitriteId, Integer> unsort
     public List<?> applyOnIndex(IndexMap indexMap) {
         return null;
     }
+
 }

nitrite/src/main/java/org/dizitart/no2/migration/MigrationManager.java

@@ -48,29 +48,37 @@ public MigrationManager(Nitrite nitrite) {
      */
     public void doMigrate() {
         if (isMigrationNeeded()) {
-            Integer existingVersion = storeMetadata.getSchemaVersion();
-            Integer incomingVersion = nitriteConfig.getSchemaVersion();
-
-            Queue<Migration> migrationPath = findMigrationPath(existingVersion, incomingVersion);
-            if (migrationPath == null || migrationPath.isEmpty()) {
-                // close the database
-                try {
-                    database.close();
-                } catch (Exception e) {
-                    throw new NitriteIOException("Failed to close the database", e);
-                }
+            Integer currentVersion = storeMetadata.getSchemaVersion();
+            Integer targetVersion = nitriteConfig.getSchemaVersion();
+
+            Queue<Migration> migrationPath = findMigrationPath(currentVersion, targetVersion);
+            boolean hasValidPath = migrationPath != null && !migrationPath.isEmpty();
 
-                throw new MigrationException("Schema version mismatch, no migration path found from version "
-                    + storeMetadata.getSchemaVersion() + " to " + nitriteConfig.getSchemaVersion());
+            if (!hasValidPath) {
+                closeDatabaseAndThrowException( currentVersion, targetVersion);
             }
+            executeMigrationPath(migrationPath);
+        }
+    }
 
-            int length = migrationPath.size();
-            for (int i = 0; i < length; i++) {
-                Migration migration = migrationPath.poll();
-                if (migration != null) {
-                    Queue<MigrationStep> migrationSteps = migration.steps();
-                    executeMigrationSteps(migrationSteps);
-                }
+    private void closeDatabaseAndThrowException(Integer currentVersion, Integer targetVersion) {
+        // close the database
+        try {
+            database.close();
+        } catch (Exception e) {
+            throw new NitriteIOException("Failed to close the database", e);
+        }
+        throw new MigrationException("Schema version mismatch, no migration path found from version "
+            + currentVersion + " to " + targetVersion);
+    }
+
+    private void executeMigrationPath(Queue<Migration> migrationPath) {
+        int pathLength = migrationPath.size();
+        for (int i = 0; i < pathLength; i++) {
+            Migration migration = migrationPath.poll();
+            if (migration != null) {
+                Queue<MigrationStep> migrationSteps = migration.steps();
+                executeMigrationSteps(migrationSteps);
             }
         }
     }