/*
    * Metis: Java Data Framework
    * Copyright 2012-2026. Tony Washer
    *
    * Licensed under the Apache License, Version 2.0 (the "License"); you may not
    * use this file except in compliance with the License.  You may obtain a copy
    * of the License at
    *
    *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
   * License for the specific language governing permissions and limitations under
   * the License.
   */
  package io.github.tonywasher.joceanus.metis.preference;
  
  import io.github.tonywasher.joceanus.metis.data.MetisDataDifference;
  import io.github.tonywasher.joceanus.metis.exc.MetisDataException;
  import io.github.tonywasher.joceanus.metis.field.MetisFieldItem;
  import io.github.tonywasher.joceanus.metis.field.MetisFieldSet;
  import io.github.tonywasher.joceanus.metis.preference.MetisPreferenceKey.MetisPreferenceId;
  import io.github.tonywasher.joceanus.metis.viewer.MetisViewerEntry;
  import io.github.tonywasher.joceanus.metis.viewer.MetisViewerManager;
  import io.github.tonywasher.joceanus.metis.viewer.MetisViewerStandardEntry;
  import io.github.tonywasher.joceanus.oceanus.base.OceanusException;
  import io.github.tonywasher.joceanus.oceanus.date.OceanusDate;
  import io.github.tonywasher.joceanus.oceanus.event.OceanusEventManager;
  import io.github.tonywasher.joceanus.oceanus.event.OceanusEventRegistrar;
  import io.github.tonywasher.joceanus.oceanus.event.OceanusEventRegistrar.OceanusEventProvider;
  import io.github.tonywasher.joceanus.oceanus.format.OceanusDataFormatter;
  import io.github.tonywasher.joceanus.oceanus.resource.OceanusBundleId;
  
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.LinkedHashMap;
  import java.util.Map;
  import java.util.function.Predicate;
  import java.util.prefs.BackingStoreException;
  import java.util.prefs.Preferences;
  
  /**
   * Wrapper class for java preferences.
   *
   * @author Tony Washer
   */
  public abstract class MetisPreferenceSet
          implements MetisFieldItem, OceanusEventProvider<MetisPreferenceEvent> {
      /**
       * Unknown preference string.
       */
      protected static final String ERROR_UNKNOWN = "Unknown Preference: ";
  
      /**
       * Invalid preference string.
       */
      protected static final String ERROR_INVALID = "Invalid Preference: ";
  
      /**
       * The Event Manager.
       */
      private final OceanusEventManager<MetisPreferenceEvent> theEventManager;
  
      /**
       * Report fields.
       */
      private final MetisFieldSet<MetisPreferenceSet> theFields;
  
      /**
       * The Preference node for this set.
       */
      private final Preferences theHandle;
  
      /**
       * The map of preferences.
       */
      private final Map<String, MetisPreferenceItem> theNameMap;
  
      /**
       * The map of preferences.
       */
      private final Map<MetisPreferenceKey, MetisPreferenceItem> theKeyMap;
  
      /**
       * The list of preferences that have a value on initialisation.
       */
      private final String[] theActive;
  
      /**
       * The name of the preferenceSet.
       */
      private final String theName;
  
      /**
       * The viewer entry.
       */
      private final MetisViewerEntry theViewerEntry;
  
     /**
      * Is this a hidden preferenceSet.
      */
     private boolean isHidden;
 
     /**
      * Constructor.
      *
      * @param pParams the parameters
      * @param pId     the resource id for the set name
      * @throws OceanusException on error
      */
     protected MetisPreferenceSet(final MetisPreferenceParams pParams,
                                  final OceanusBundleId pId) throws OceanusException {
         this(pParams, pId.getValue());
     }
 
     /**
      * Constructor.
      *
      * @param pParams the parameters
      * @param pName   the set name
      * @throws OceanusException on error
      */
     protected MetisPreferenceSet(final MetisPreferenceParams pParams,
                                  final String pName) throws OceanusException {
         /* Store name */
         theName = pName;
 
         /* Allocate the fields */
         theFields = MetisFieldSet.newFieldSet(this);
 
         /* Access the handle */
         theHandle = deriveHandle();
 
         /* Create Event Manager */
         theEventManager = new OceanusEventManager<>();
 
         /* Allocate the preference maps */
         theNameMap = new LinkedHashMap<>();
         theKeyMap = new LinkedHashMap<>();
 
         /* Access the active key names */
         try {
             theActive = theHandle.keys();
         } catch (BackingStoreException e) {
             throw new MetisDataException("Failed to access preferences", e);
         }
 
         /* Create the viewer record */
         theViewerEntry = defineViewerEntry(pParams);
 
         /* Define the preferences */
         definePreferences();
         autoCorrectPreferences();
 
         /* Store any changes */
         storeChanges();
     }
 
     /**
      * Process parameters.
      *
      * @param pParams the parameters
      * @return the viewer entry
      */
     protected MetisViewerEntry defineViewerEntry(final MetisPreferenceParams pParams) {
         /* Create the viewer record */
         final MetisViewerManager myViewer = pParams.getViewerManager();
         final MetisViewerEntry myParent = myViewer.getStandardEntry(MetisViewerStandardEntry.PREFERENCES);
         final MetisViewerEntry myEntry = myViewer.newEntry(myParent, theName);
         myEntry.setObject(this);
         return myEntry;
     }
 
     @Override
     public MetisFieldSetDef getDataFieldSet() {
         return theFields;
     }
 
     @Override
     public String formatObject(final OceanusDataFormatter pFormatter) {
         return theFields.getName();
     }
 
     /**
      * Declare preference.
      *
      * @param pPref the preference to declare
      */
     void declarePreference(final MetisPreferenceItem pPref) {
         /* Create the DataField */
         theFields.declareLocalField(pPref.getPreferenceName(), s -> pPref.getViewerValue());
     }
 
     @Override
     public OceanusEventRegistrar<MetisPreferenceEvent> getEventRegistrar() {
         return theEventManager.getEventRegistrar();
     }
 
     /**
      * Hook to enable preferenceSets to define their preferences.
      *
      * @throws OceanusException on error
      */
     protected abstract void definePreferences() throws OceanusException;
 
     /**
      * Hook to enable preferenceSets to autoCorrect their preferences.
      * <p>
      * This is used both to initialise preferencesSet defaults and to adjust the set when a value
      * changes.
      */
     public abstract void autoCorrectPreferences();
 
     /**
      * Obtain the name of the set.
      *
      * @return the name
      */
     public String getName() {
         return theName;
     }
 
     /**
      * Is this a hidden preferenceSet?
      *
      * @return true/false
      */
     public boolean isHidden() {
         return isHidden;
     }
 
     /**
      * Set this preferenceSet as hidden.
      */
     protected void setHidden() {
         isHidden = true;
     }
 
     /**
      * Obtain the collection of preferences.
      *
      * @return the preferences
      */
     public Collection<MetisPreferenceItem> getPreferences() {
         return theKeyMap.values();
     }
 
     /**
      * Set the focus.
      */
     public void setFocus() {
         theViewerEntry.setFocus();
     }
 
     /**
      * Update the viewer entry.
      */
     public void updateViewerEntry() {
         theViewerEntry.setObject(this);
     }
 
     /**
      * Derive handle for node.
      *
      * @return the class name
      */
     private Preferences deriveHandle() {
         /* Obtain the class name */
         final Class<?> myClass = this.getClass();
         String myName = myClass.getCanonicalName();
 
         /* Obtain the package name */
         final String myPackage = myClass.getPackage().getName();
 
         /* Strip off the package name */
         myName = myName.substring(myPackage.length() + 1);
 
         /* Derive the handle */
         final Preferences myHandle = Preferences.userNodeForPackage(myClass);
         return myHandle.node(myName);
     }
 
     /**
      * Define new String preference.
      *
      * @param pKey the key for the preference
      * @return the preference item
      */
     protected MetisStringPreference defineStringPreference(final MetisPreferenceKey pKey) {
         /* Define the preference */
         final MetisStringPreference myPref = new MetisStringPreference(this, pKey);
 
         /* Add it to the list of preferences */
         definePreference(myPref);
 
         /* Return the preference */
         return myPref;
     }
 
     /**
      * Define new File preference.
      *
      * @param pKey the key for the preference
      * @return the preference item
      */
     protected MetisStringPreference defineFilePreference(final MetisPreferenceKey pKey) {
         /* Define the preference */
         final MetisStringPreference myPref = new MetisStringPreference(this, pKey, MetisPreferenceType.FILE);
 
         /* Add it to the list of preferences */
         definePreference(myPref);
 
         /* Return the preference */
         return myPref;
     }
 
     /**
      * Define new Directory preference.
      *
      * @param pKey the key for the preference
      * @return the preference item
      */
     protected MetisStringPreference defineDirectoryPreference(final MetisPreferenceKey pKey) {
         /* Define the preference */
         final MetisStringPreference myPref = new MetisStringPreference(this, pKey, MetisPreferenceType.DIRECTORY);
 
         /* Add it to the list of preferences */
         definePreference(myPref);
 
         /* Return the preference */
         return myPref;
     }
 
     /**
      * Define new Colour preference.
      *
      * @param pKey the key for the preference
      * @return the preference item
      */
     protected MetisStringPreference defineColorPreference(final MetisPreferenceKey pKey) {
         /* Define the preference */
         final MetisStringPreference myPref = new MetisStringPreference(this, pKey, MetisPreferenceType.COLOR);
 
         /* Add it to the list of preferences */
         definePreference(myPref);
 
         /* Return the preference */
         return myPref;
     }
 
     /**
      * Define new Integer preference.
      *
      * @param pKey the key for the preference
      * @return the preference item
      */
     protected MetisIntegerPreference defineIntegerPreference(final MetisPreferenceKey pKey) {
         /* Define the preference */
         final MetisIntegerPreference myPref = new MetisIntegerPreference(this, pKey);
 
         /* Add it to the list of preferences */
         definePreference(myPref);
 
         /* Return the preference */
         return myPref;
     }
 
     /**
      * Define new Boolean preference.
      *
      * @param pKey the key for the preference
      * @return the preference item
      */
     protected MetisBooleanPreference defineBooleanPreference(final MetisPreferenceKey pKey) {
         /* Define the preference */
         final MetisBooleanPreference myPref = new MetisBooleanPreference(this, pKey);
 
         /* Add it to the list of preferences */
         definePreference(myPref);
 
         /* Return the preference */
         return myPref;
     }
 
     /**
      * Define new Date preference.
      *
      * @param pKey the key for the preference
      * @return the preference item
      */
     protected MetisDatePreference defineDatePreference(final MetisPreferenceKey pKey) {
         /* Define the preference */
         final MetisDatePreference myPref = new MetisDatePreference(this, pKey);
 
         /* Add it to the list of preferences */
         definePreference(myPref);
 
         /* Return the preference */
         return myPref;
     }
 
     /**
      * Define new Enum preference.
      *
      * @param <E>    the Enum type
      * @param pKey   the key for the preference
      * @param pClazz the Enum class
      * @return the newly created preference
      */
     protected <E extends Enum<E>> MetisEnumPreference<E> defineEnumPreference(final MetisPreferenceKey pKey,
                                                                               final Class<E> pClazz) {
         /* Create the preference */
         final MetisEnumPreference<E> myPref = new MetisEnumPreference<>(this, pKey, pClazz);
 
         /* Add it to the list of preferences */
         definePreference(myPref);
 
         /* Return the preference */
         return myPref;
     }
 
     /**
      * Define a preference for the node.
      *
      * @param pPreference the preference to define
      */
     protected void definePreference(final MetisPreferenceItem pPreference) {
         /* Access the key of the preference */
         final String myName = pPreference.getPreferenceName();
 
         /* Reject if the name is already present */
         if (theNameMap.get(myName) != null) {
             throw new IllegalArgumentException("preference "
                     + myName
                     + " is already defined");
         }
 
         /* Add the preference to the map */
         theNameMap.put(myName, pPreference);
         theKeyMap.put(pPreference.getKey(), pPreference);
     }
 
     /**
      * Obtain preference by key.
      *
      * @param pKey the key of the preference
      * @return the preference
      */
     public MetisPreferenceItem getPreference(final MetisPreferenceKey pKey) {
         return theKeyMap.get(pKey);
     }
 
     /**
      * Obtain preference.
      *
      * @param pName the name of the preference
      * @return the preference
      */
     protected MetisPreferenceItem getPreference(final String pName) {
         return theNameMap.get(pName);
     }
 
     /**
      * Obtain String preference.
      *
      * @param pKey the key of the preference
      * @return the String preference
      */
     public MetisStringPreference getStringPreference(final MetisPreferenceKey pKey) {
         /* Access preference */
         final MetisPreferenceItem myPref = getPreference(pKey);
 
         /* Reject if not found */
         if (myPref == null) {
             throw new IllegalArgumentException(ERROR_UNKNOWN
                     + pKey);
         }
 
         /* Reject if wrong type */
         if (!(myPref instanceof MetisStringPreference)) {
             throw new IllegalArgumentException(ERROR_INVALID
                     + pKey);
         }
 
         /* Return the preference */
         return (MetisStringPreference) myPref;
     }
 
     /**
      * Obtain String value.
      *
      * @param pKey the key of the preference
      * @return the String value
      */
     public String getStringValue(final MetisPreferenceKey pKey) {
         /* Access preference */
         final MetisStringPreference myPref = getStringPreference(pKey);
 
         /* Return the value */
         return myPref.getValue();
     }
 
     /**
      * Obtain Integer preference.
      *
      * @param pKey the key of the preference
      * @return the Integer preference
      */
     public MetisIntegerPreference getIntegerPreference(final MetisPreferenceKey pKey) {
         /* Access preference */
         final MetisPreferenceItem myPref = getPreference(pKey);
 
         /* Reject if not found */
         if (myPref == null) {
             throw new IllegalArgumentException(ERROR_UNKNOWN
                     + pKey);
         }
 
         /* Reject if wrong type */
         if (!(myPref instanceof MetisPreferenceSet.MetisIntegerPreference)) {
             throw new IllegalArgumentException(ERROR_INVALID
                     + pKey);
         }
 
         /* Return the preference */
         return (MetisIntegerPreference) myPref;
     }
 
     /**
      * Obtain Integer value.
      *
      * @param pKey the key of the preference
      * @return the Integer value
      */
     public Integer getIntegerValue(final MetisPreferenceKey pKey) {
         /* Access preference */
         final MetisIntegerPreference myPref = getIntegerPreference(pKey);
 
         /* Return the value */
         return myPref.getValue();
     }
 
     /**
      * Obtain Boolean preference.
      *
      * @param pKey the key of the preference
      * @return the Boolean preference
      */
     public MetisBooleanPreference getBooleanPreference(final MetisPreferenceKey pKey) {
         /* Access preference */
         final MetisPreferenceItem myPref = getPreference(pKey);
 
         /* Reject if not found */
         if (myPref == null) {
             throw new IllegalArgumentException(ERROR_UNKNOWN
                     + pKey);
         }
 
         /* Reject if wrong type */
         if (!(myPref instanceof MetisBooleanPreference)) {
             throw new IllegalArgumentException(ERROR_INVALID
                     + pKey);
         }
 
         /* Return the preference */
         return (MetisBooleanPreference) myPref;
     }
 
     /**
      * Obtain Boolean value.
      *
      * @param pKey the key of the preference
      * @return the Boolean value
      */
     public Boolean getBooleanValue(final MetisPreferenceKey pKey) {
         /* Access preference */
         final MetisBooleanPreference myPref = getBooleanPreference(pKey);
 
         /* Return the value */
         return myPref.getValue();
     }
 
     /**
      * Obtain Date preference.
      *
      * @param pKey the key of the preference
      * @return the Date preference
      */
     public MetisDatePreference getDatePreference(final MetisPreferenceKey pKey) {
         /* Access preference */
         final MetisPreferenceItem myPref = getPreference(pKey);
 
         /* Reject if not found */
         if (myPref == null) {
             throw new IllegalArgumentException(ERROR_UNKNOWN
                     + pKey);
         }
 
         /* Reject if wrong type */
         if (!(myPref instanceof MetisDatePreference)) {
             throw new IllegalArgumentException(ERROR_INVALID
                     + pKey);
         }
 
         /* Return the preference */
         return (MetisDatePreference) myPref;
     }
 
     /**
      * Obtain Date value.
      *
      * @param pKey the key of the preference
      * @return the Date value
      */
     public OceanusDate getDateValue(final MetisPreferenceKey pKey) {
         /* Access preference */
         final MetisDatePreference myPref = getDatePreference(pKey);
 
         /* Return the value */
         return myPref.getValue();
     }
 
     /**
      * Obtain Enum preference.
      *
      * @param <E>    the EnumType
      * @param pKey   the key of the preference
      * @param pClazz the Enum class
      * @return the Enum preference
      */
     public <E extends Enum<E>> MetisEnumPreference<E> getEnumPreference(final MetisPreferenceKey pKey,
                                                                         final Class<E> pClazz) {
         /* Access preference */
         final MetisPreferenceItem myPref = getPreference(pKey);
 
         /* Reject if not found */
         if (myPref == null) {
             throw new IllegalArgumentException(ERROR_UNKNOWN
                     + pKey);
         }
 
         /* Reject if wrong type */
         if (!(myPref instanceof MetisEnumPreference)) {
             throw new IllegalArgumentException(ERROR_INVALID
                     + pKey);
         }
 
         /* Access as Enum preference */
         @SuppressWarnings("unchecked") final MetisEnumPreference<E> myEnumPref = (MetisEnumPreference<E>) myPref;
         if (!myEnumPref.theClazz.equals(pClazz)) {
             throw new IllegalArgumentException(ERROR_INVALID
                     + pKey);
         }
 
         /* Return the preference */
         return myEnumPref;
     }
 
     /**
      * Obtain Enum value.
      *
      * @param <E>    the EnumType
      * @param pKey   the key of the preference
      * @param pClazz the Enum class
      * @return the Enum value
      */
     public <E extends Enum<E>> E getEnumValue(final MetisPreferenceKey pKey,
                                               final Class<E> pClazz) {
         /* Access preference */
         final MetisEnumPreference<E> myPref = getEnumPreference(pKey, pClazz);
 
         /* Return the value */
         return myPref.getValue();
     }
 
     /**
      * Reset all changes in this preference set.
      */
     public void resetChanges() {
         /* Loop through all the preferences */
         for (MetisPreferenceItem myPref : theKeyMap.values()) {
             /* Reset the changes */
             myPref.resetChanges();
         }
     }
 
     /**
      * Store preference changes.
      *
      * @throws OceanusException on error
      */
     public final void storeChanges() throws OceanusException {
         /* Loop through all the preferences */
         for (MetisPreferenceItem myPref : theKeyMap.values()) {
             /* Store any changes */
             myPref.storePreference();
         }
 
         /* Protect against exceptions */
         try {
             /* Flush the output */
             theHandle.flush();
 
             /* Notify listeners */
             theEventManager.fireEvent(MetisPreferenceEvent.PREFCHANGED);
 
         } catch (BackingStoreException e) {
             throw new MetisDataException("Failed to flush preferences to store", e);
         }
     }
 
     /**
      * Does the preference set have changes.
      *
      * @return true/false
      */
     public boolean hasChanges() {
         /* Loop through all the preferences */
         for (MetisPreferenceItem myPref : theKeyMap.values()) {
             /* Check for changes */
             if (myPref.isChanged()) {
                 return true;
             }
         }
 
         /* Return no changes */
         return false;
     }
 
     /**
      * Check whether a preference exists.
      *
      * @param pKey the key of the preference
      * @return whether the preference already exists
      */
     protected boolean checkExists(final MetisPreferenceKey pKey) {
         /* Obtain the name */
         final String myKeyName = pKey.getName();
 
         /* Loop through all the keys */
         for (String myName : theActive) {
             /* If the name matches return true */
             if (myName.equals(myKeyName)) {
                 return true;
             }
         }
 
         /* return no match */
         return false;
     }
 
     /**
      * Underlying preference item class.
      */
     public abstract static class MetisPreferenceItem {
         /**
          * preferenceSet.
          */
         private final MetisPreferenceSet theSet;
 
         /**
          * preference Key.
          */
         private final MetisPreferenceKey theKey;
 
         /**
          * preference Name.
          */
         private final String theName;
 
         /**
          * Display Name.
          */
         private final String theDisplay;
 
         /**
          * preference Type.
          */
         private final MetisPreferenceId theType;
 
         /**
          * preference Value.
          */
         private Object theValue;
 
         /**
          * New preference Value.
          */
         private Object theNewValue;
 
         /**
          * Is there a change to the preference?
          */
         private boolean isChanged;
 
         /**
          * Is the preference hidden?
          */
         private boolean isHidden;
 
         /**
          * Constructor.
          *
          * @param pSet  the preference Set
          * @param pKey  the key of the preference
          * @param pType the type of the preference
          */
         protected MetisPreferenceItem(final MetisPreferenceSet pSet,
                                       final MetisPreferenceKey pKey,
                                       final MetisPreferenceId pType) {
             /* Store parameters */
             theSet = pSet;
             theKey = pKey;
             theType = pType;
 
             /* Obtain key details */
             theName = pKey.getName();
             theDisplay = pKey.getDisplay();
 
             /* Create the DataField */
             theSet.declarePreference(this);
         }
 
         /**
          * Obtain viewer value.
          *
          * @return the value
          */
         Object getViewerValue() {
             return isHidden
                     ? null
                     : getValue();
         }
 
         /**
          * Obtain the preferenceSet.
          *
          * @return the set
          */
         protected MetisPreferenceSet getSet() {
             return theSet;
         }
 
         /**
          * Obtain the preference handle.
          *
          * @return the preference handle
          */
         protected Preferences getHandle() {
             return theSet.theHandle;
         }
 
         /**
          * Obtain the key of the preference.
          *
          * @return the key of the preference
          */
         protected MetisPreferenceKey getKey() {
             return theKey;
         }
 
         /**
          * Obtain the name of the preference.
          *
          * @return the name of the preference
          */
         protected String getPreferenceName() {
             return theName;
         }
 
         /**
          * Obtain the display name of the preference.
          *
          * @return the display name of the preference
          */
         public String getDisplay() {
             return theDisplay;
         }
 
         /**
          * Obtain the type of the preference.
          *
          * @return the type of the preference
          */
         public MetisPreferenceId getType() {
             return theType;
         }
 
         /**
          * Obtain the value of the preference.
          *
          * @return the value of the preference
          */
         protected Object getValue() {
             /* Return the active value */
             return isChanged
                     ? theNewValue
                     : theValue;
         }
 
         /**
          * Is the preference available?
          *
          * @return true/false
          */
         public boolean isAvailable() {
             return getValue() != null;
         }
 
         /**
          * Is the preference changed?
          *
          * @return true/false
          */
         public boolean isChanged() {
             return isChanged;
         }
 
         /**
          * Is the preference hidden?
          *
          * @return true/false
          */
         public boolean isHidden() {
             return isHidden;
         }
 
         /**
          * Set hidden.
          *
          * @param pHidden true/false
          */
         public void setHidden(final boolean pHidden) {
             isHidden = pHidden;
         }
 
         /**
          * Set value.
          *
          * @param pValue the value
          */
         protected void setTheValue(final Object pValue) {
             theValue = pValue;
         }
 
         /**
          * Set new value.
          *
          * @param pNewValue the new value
          */
         protected void setNewValue(final Object pNewValue) {
             theNewValue = pNewValue;
             isChanged = !MetisDataDifference.isEqual(theNewValue, theValue);
         }
 
         /**
          * Reset changes.
          */
         private void resetChanges() {
             /* Reset change indicators */
             theNewValue = null;
             isChanged = false;
         }
 
         /**
          * Store preference.
          *
          * @throws OceanusException on error
          */
         private void storePreference() throws OceanusException {
             /* If the preference has changed */
             if (isChanged) {
                 /* If we have a value */
                 if (theNewValue != null) {
                     /* Store the value */
                     storeThePreference(theNewValue);
 
                     /* Note the new value and reset changes */
                     setTheValue(theNewValue);
 
                     /* else no value */
                 } else {
                     /* remove the preference */
                     getHandle().remove(theName);
                 }
 
                 /* reset changes */
                 resetChanges();
             }
         }
 
         /**
          * Store the value of the preference.
          *
          * @param pNewValue the new value to store
          * @throws OceanusException on error
          */
         protected abstract void storeThePreference(Object pNewValue) throws OceanusException;
     }
 
     /**
      * String preference.
      */
     public static class MetisStringPreference
             extends MetisPreferenceItem {
         /**
          * Constructor.
          *
          * @param pSet the preference Set
          * @param pKey the key of the preference
          */
         protected MetisStringPreference(final MetisPreferenceSet pSet,
                                         final MetisPreferenceKey pKey) {
             this(pSet, pKey, MetisPreferenceType.STRING);
         }
 
         /**
          * Constructor.
          *
          * @param pSet  the preference Set
          * @param pKey  the key of the preference
          * @param pType the type of the preference
          */
         private MetisStringPreference(final MetisPreferenceSet pSet,
                                       final MetisPreferenceKey pKey,
                                       final MetisPreferenceType pType) {
             /* Store name */
             super(pSet, pKey, pType);
 
             /* Check whether we have an existing value */
             if (pSet.checkExists(pKey)) {
                 /* Access the value */
                 final String myValue = getHandle().get(getPreferenceName(), null);
 
                 /* Set as initial value */
                 setTheValue(myValue);
             }
         }
 
         @Override
         public String getValue() {
             return (String) super.getValue();
         }
 
         /**
          * Set value.
          *
          * @param pNewValue the new value
          */
         public void setValue(final String pNewValue) {
             setNewValue(pNewValue);
         }
 
         @Override
         protected void storeThePreference(final Object pNewValue) {
             getHandle().put(getPreferenceName(), (String) pNewValue);
         }
     }
 
     /**
      * Integer preference.
      */
     public static class MetisIntegerPreference
             extends MetisPreferenceItem {
         /**
          * The minimum value.
          */
         private Integer theMinimum;
 
         /**
          * The maximum value.
          */
         private Integer theMaximum;
 
         /**
          * Constructor.
          *
          * @param pSet the preference Set
          * @param pKey the key of the preference
          */
         protected MetisIntegerPreference(final MetisPreferenceSet pSet,
                                          final MetisPreferenceKey pKey) {
             /* Store name */
             super(pSet, pKey, MetisPreferenceType.INTEGER);
 
             /* Check whether we have an existing value */
             if (pSet.checkExists(pKey)) {
                 /* Access the value */
                 final int myValue = getHandle().getInt(getPreferenceName(), -1);
 
                 /* Set as initial value */
                 setTheValue(myValue);
             }
         }
 
         @Override
         public Integer getValue() {
             return (Integer) super.getValue();
         }
 
         /**
          * Obtain the minimum value.
          *
          * @return the minimum
          */
         public Integer getMinimum() {
             return theMinimum;
         }
 
         /**
          * Obtain the maximum value.
          *
          * @return the maximum
          */
         public Integer getMaximum() {
             return theMaximum;
         }
 
         /**
          * Set value.
          *
          * @param pNewValue the new value
          */
         public void setValue(final Integer pNewValue) {
             setNewValue(pNewValue);
         }
 
         /**
          * Set range.
          *
          * @param pMinimum the minimum value
          * @param pMaximum the maximum value
          */
         public void setRange(final Integer pMinimum,
                              final Integer pMaximum) {
             theMinimum = pMinimum;
             theMaximum = pMaximum;
         }
 
         /**
          * Validate the range.
          *
          * @return true/false
          */
         public boolean validate() {
             if (isAvailable()) {
                 final Integer myValue = getValue();
                 if ((theMinimum != null)
                         && theMinimum > myValue) {
                     return false;
                 }
                 if ((theMaximum != null)
                         && theMaximum < myValue) {
                     return false;
                 }
             }
             return true;
         }
 
         @Override
         protected void storeThePreference(final Object pNewValue) {
             getHandle().putInt(getPreferenceName(), (Integer) pNewValue);
         }
     }
 
     /**
      * Boolean preference.
      */
     public static class MetisBooleanPreference
             extends MetisPreferenceItem {
         /**
          * Constructor.
          *
          * @param pSet the preference Set
          * @param pKey the key of the preference
          */
         protected MetisBooleanPreference(final MetisPreferenceSet pSet,
                                          final MetisPreferenceKey pKey) {
             /* Store name */
             super(pSet, pKey, MetisPreferenceType.BOOLEAN);
 
             /* Check whether we have an existing value */
             if (pSet.checkExists(pKey)) {
                 /* Access the value */
                 final boolean myValue = getHandle().getBoolean(getPreferenceName(), false);
 
                 /* Set as initial value */
                 setTheValue(myValue
                         ? Boolean.TRUE
                         : Boolean.FALSE);
             }
         }
 
         @Override
         public Boolean getValue() {
             return (Boolean) super.getValue();
         }
 
         /**
          * Set value.
          *
          * @param pNewValue the new value
          */
         public void setValue(final Boolean pNewValue) {
             Boolean myNewValue = pNewValue;
 
             /* Take a copy if not null */
             if (myNewValue != null) {
                 myNewValue = myNewValue
                         ? Boolean.TRUE
                         : Boolean.FALSE;
             }
 
             /* Set the new value */
             setNewValue(myNewValue);
         }
 
         @Override
         protected void storeThePreference(final Object pNewValue) {
             getHandle().putBoolean(getPreferenceName(), (Boolean) pNewValue);
         }
     }
 
     /**
      * Date preference.
      */
     public static class MetisDatePreference
             extends MetisPreferenceItem {
         /**
          * Constructor.
          *
          * @param pSet the preference Set
          * @param pKey the key of the preference
          */
         protected MetisDatePreference(final MetisPreferenceSet pSet,
                                       final MetisPreferenceKey pKey) {
             /* Store name */
             super(pSet, pKey, MetisPreferenceType.DATE);
 
             /* Check whether we have an existing value */
             if (pSet.checkExists(pKey)) {
                 /* Access the value */
                 final String myValue = getHandle().get(getPreferenceName(), null);
 
                 /* Parse the Date */
                 final OceanusDate myDate = new OceanusDate(myValue);
 
                 /* Set as initial value */
                 setTheValue(myDate);
             }
         }
 
         @Override
         public OceanusDate getValue() {
             return (OceanusDate) super.getValue();
         }
 
         /**
          * Set value.
          *
          * @param pNewValue the new value
          */
         public void setValue(final OceanusDate pNewValue) {
             OceanusDate myNewValue = pNewValue;
 
             /* Take a copy if not null */
             if (myNewValue != null) {
                 myNewValue = new OceanusDate(myNewValue);
             }
 
             /* Set the new value */
             setNewValue(myNewValue);
         }
 
         @Override
         protected void storeThePreference(final Object pNewValue) {
             getHandle().put(getPreferenceName(), ((OceanusDate) pNewValue).toString());
         }
     }
 
     /**
      * Enum preference.
      *
      * @param <E> the Enum type
      */
     public static class MetisEnumPreference<E extends Enum<E>>
             extends MetisPreferenceItem {
         /**
          * The enum class.
          */
         private final Class<E> theClazz;
 
         /**
          * The enum values.
          */
         private final E[] theValues;
 
         /**
          * The filter.
          */
         private Predicate<E> theFilter;
 
         /**
          * Constructor.
          *
          * @param pSet   the preference Set
          * @param pKey   the key of the preference
          * @param pClazz the class of the preference
          */
         public MetisEnumPreference(final MetisPreferenceSet pSet,
                                    final MetisPreferenceKey pKey,
                                    final Class<E> pClazz) {
             /* Store name */
             super(pSet, pKey, MetisPreferenceType.ENUM);
 
             /* Store the class */
             theClazz = pClazz;
             theValues = theClazz.getEnumConstants();
 
             /* Set null filter */
             setFilter(null);
 
             /* Check whether we have an existing value */
             if (pSet.checkExists(pKey)) {
                 /* Access the value */
                 final String myValue = getHandle().get(getPreferenceName(), null);
 
                 /* Set the value */
                 final E myEnum = findValue(myValue);
                 setTheValue(myEnum);
             }
         }
 
         @Override
         public E getValue() {
             return theClazz.cast(super.getValue());
         }
 
         /**
          * Obtain the values of the preference.
          *
          * @return the values of the preference
          */
         public E[] getValues() {
             return Arrays.copyOf(theValues, theValues.length);
         }
 
         /**
          * Obtain the filter.
          *
          * @return the filter
          */
         public Predicate<E> getFilter() {
             return theFilter;
         }
 
         /**
          * Set value.
          *
          * @param pNewValue the new value
          * @return the Enum value
          */
         private E findValue(final String pNewValue) {
             /* Loop through the Enum constants */
             for (E myEnum : theValues) {
                 /* If we match */
                 if (pNewValue.equals(myEnum.name())) {
                     /* Return the value */
                     return myEnum;
                 }
             }
 
             /* Return invalid value */
             return null;
         }
 
         /**
          * Set value.
          *
          * @param pNewValue the new value
          */
         public final void setValue(final String pNewValue) {
             /* Convert to enum and set */
             final E myEnum = findValue(pNewValue);
             setNewValue(myEnum);
         }
 
         /**
          * Set value.
          *
          * @param pNewValue the new value
          */
         public void setValue(final E pNewValue) {
             setNewValue(pNewValue);
         }
 
         /**
          * Set filter.
          *
          * @param pFilter the new filter
          */
         public void setFilter(final Predicate<E> pFilter) {
             theFilter = theFilter == null
                     ? p -> true
                     : pFilter;
         }
 
         @Override
         protected void storeThePreference(final Object pNewValue) {
             getHandle().put(getPreferenceName(), theClazz.cast(pNewValue).name());
         }
     }
 }