/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You 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 org.apache.commons.collections4.bidimap;
  
  import java.util.Collection;
  import java.util.Iterator;
  import java.util.Map;
  import java.util.Objects;
  import java.util.Set;
  import java.util.function.Predicate;
  
  import org.apache.commons.collections4.BidiMap;
  import org.apache.commons.collections4.MapIterator;
  import org.apache.commons.collections4.ResettableIterator;
  import org.apache.commons.collections4.collection.AbstractCollectionDecorator;
  import org.apache.commons.collections4.iterators.AbstractIteratorDecorator;
  import org.apache.commons.collections4.keyvalue.AbstractMapEntryDecorator;
  
  /**
   * Abstract {@link BidiMap} implemented using two maps.
   * <p>
   * An implementation can be written simply by implementing the
   * {@link #createBidiMap(Map, Map, BidiMap)} method.
   * </p>
   *
   * @param <K> the type of the keys in the map
   * @param <V> the type of the values in the map
   * @see DualHashBidiMap
   * @see DualTreeBidiMap
   * @since 3.0
   */
  public abstract class AbstractDualBidiMap<K, V> implements BidiMap<K, V> {
  
      /**
       * Inner class MapIterator.
       *
       * @param <K> the type of the keys.
       * @param <V> the type of the values.
       */
      protected static class BidiMapIterator<K, V> implements MapIterator<K, V>, ResettableIterator<K> {
  
          /** The parent map */
          protected final AbstractDualBidiMap<K, V> parent;
  
          /** The iterator being wrapped */
          protected Iterator<Map.Entry<K, V>> iterator;
  
          /** The last returned entry */
          protected Map.Entry<K, V> last;
  
          /** Whether remove is allowed at present */
          protected boolean canRemove;
  
          /**
           * Constructs a new instance.
           * @param parent  the parent map
           */
          protected BidiMapIterator(final AbstractDualBidiMap<K, V> parent) {
              this.parent = parent;
              this.iterator = parent.normalMap.entrySet().iterator();
          }
  
          @Override
          public K getKey() {
              if (last == null) {
                  throw new IllegalStateException(
                          "Iterator getKey() can only be called after next() and before remove()");
              }
              return last.getKey();
          }
  
          @Override
          public V getValue() {
              if (last == null) {
                  throw new IllegalStateException(
                          "Iterator getValue() can only be called after next() and before remove()");
              }
              return last.getValue();
          }
  
          @Override
          public boolean hasNext() {
              return iterator.hasNext();
          }
  
         @Override
         public K next() {
             last = iterator.next();
             canRemove = true;
             return last.getKey();
         }
 
         @Override
         public void remove() {
             if (!canRemove) {
                 throw new IllegalStateException("Iterator remove() can only be called once after next()");
             }
             // store value as remove may change the entry in the decorator (e.g. TreeMap)
             final V value = last.getValue();
             iterator.remove();
             parent.reverseMap.remove(value);
             last = null;
             canRemove = false;
         }
 
         @Override
         public void reset() {
             iterator = parent.normalMap.entrySet().iterator();
             last = null;
             canRemove = false;
         }
 
         @Override
         public V setValue(final V value) {
             if (last == null) {
                 throw new IllegalStateException(
                         "Iterator setValue() can only be called after next() and before remove()");
             }
             if (parent.reverseMap.containsKey(value) &&
                 parent.reverseMap.get(value) != last.getKey()) {
                 throw new IllegalArgumentException(
                         "Cannot use setValue() when the object being set is already in the map");
             }
             return parent.put(last.getKey(), value);
         }
 
         @Override
         public String toString() {
             if (last != null) {
                 return "MapIterator[" + getKey() + "=" + getValue() + "]";
             }
             return "MapIterator[]";
         }
     }
 
     /**
      * Inner class EntrySet.
      *
      * @param <K> the type of the keys.
      * @param <V> the type of the values.
      */
     protected static class EntrySet<K, V> extends View<K, V, Map.Entry<K, V>> implements Set<Map.Entry<K, V>> {
 
         /** Serialization version */
         private static final long serialVersionUID = 4040410962603292348L;
 
         /**
          * Constructs a new instance.
          *
          * @param parent  the parent BidiMap
          */
         protected EntrySet(final AbstractDualBidiMap<K, V> parent) {
             super(parent.normalMap.entrySet(), parent);
         }
 
         @Override
         public Iterator<Map.Entry<K, V>> iterator() {
             return parent.createEntrySetIterator(super.iterator());
         }
 
         @Override
         public boolean remove(final Object obj) {
             if (!(obj instanceof Map.Entry)) {
                 return false;
             }
             final Map.Entry<?, ?> entry = (Map.Entry<?, ?>) obj;
             final Object key = entry.getKey();
             if (parent.containsKey(key)) {
                 final V value = parent.normalMap.get(key);
                 if (Objects.equals(value, entry.getValue())) {
                     parent.normalMap.remove(key);
                     parent.reverseMap.remove(value);
                     return true;
                 }
             }
             return false;
         }
     }
 
     /**
      * Inner class EntrySetIterator.
      *
      * @param <K> the type of the keys.
      * @param <V> the type of the values.
      */
     protected static class EntrySetIterator<K, V> extends AbstractIteratorDecorator<Map.Entry<K, V>> {
 
         /** The parent map */
         protected final AbstractDualBidiMap<K, V> parent;
 
         /** The last returned entry */
         protected Map.Entry<K, V> last;
 
         /** Whether remove is allowed at present */
         protected boolean canRemove;
 
         /**
          * Constructs a new instance.
          * @param iterator  the iterator to decorate
          * @param parent  the parent map
          */
         protected EntrySetIterator(final Iterator<Map.Entry<K, V>> iterator, final AbstractDualBidiMap<K, V> parent) {
             super(iterator);
             this.parent = parent;
         }
 
         @Override
         public Map.Entry<K, V> next() {
             last = new MapEntry<>(super.next(), parent);
             canRemove = true;
             return last;
         }
 
         @Override
         public void remove() {
             if (!canRemove) {
                 throw new IllegalStateException("Iterator remove() can only be called once after next()");
             }
             // store value as remove may change the entry in the decorator (e.g. TreeMap)
             final Object value = last.getValue();
             super.remove();
             parent.reverseMap.remove(value);
             last = null;
             canRemove = false;
         }
     }
 
     /**
      * Inner class KeySet.
      *
      * @param <K> the type of elements maintained by this set
      */
     protected static class KeySet<K> extends View<K, Object, K> implements Set<K> {
 
         /** Serialization version */
         private static final long serialVersionUID = -7107935777385040694L;
 
         /**
          * Constructs a new instance.
          *
          * @param parent  the parent BidiMap
          */
         @SuppressWarnings("unchecked")
         protected KeySet(final AbstractDualBidiMap<K, ?> parent) {
             super(parent.normalMap.keySet(), (AbstractDualBidiMap<K, Object>) parent);
         }
 
         @Override
         public boolean contains(final Object key) {
             return parent.normalMap.containsKey(key);
         }
 
         @Override
         public Iterator<K> iterator() {
             return parent.createKeySetIterator(super.iterator());
         }
 
         @Override
         public boolean remove(final Object key) {
             if (parent.normalMap.containsKey(key)) {
                 final Object value = parent.normalMap.remove(key);
                 parent.reverseMap.remove(value);
                 return true;
             }
             return false;
         }
     }
 
     /**
      * Inner class KeySetIterator.
      *
      * @param <K> the key type.
      */
     protected static class KeySetIterator<K> extends AbstractIteratorDecorator<K> {
 
         /** The parent map */
         protected final AbstractDualBidiMap<K, ?> parent;
 
         /** The last returned key */
         protected K lastKey;
 
         /** Whether remove is allowed at present */
         protected boolean canRemove;
 
         /**
          * Constructs a new instance.
          * @param iterator  the iterator to decorate
          * @param parent  the parent map
          */
         protected KeySetIterator(final Iterator<K> iterator, final AbstractDualBidiMap<K, ?> parent) {
             super(iterator);
             this.parent = parent;
         }
 
         @Override
         public K next() {
             lastKey = super.next();
             canRemove = true;
             return lastKey;
         }
 
         @Override
         public void remove() {
             if (!canRemove) {
                 throw new IllegalStateException("Iterator remove() can only be called once after next()");
             }
             final Object value = parent.normalMap.get(lastKey);
             super.remove();
             parent.reverseMap.remove(value);
             lastKey = null;
             canRemove = false;
         }
     }
 
     /**
      * Inner class MapEntry.
      *
      * @param <K> the type of the keys.
      * @param <V> the type of the values.
      */
     protected static class MapEntry<K, V> extends AbstractMapEntryDecorator<K, V> {
 
         /** The parent map */
         protected final AbstractDualBidiMap<K, V> parent;
 
         /**
          * Constructs a new instance.
          * @param entry  the entry to decorate
          * @param parent  the parent map
          */
         protected MapEntry(final Map.Entry<K, V> entry, final AbstractDualBidiMap<K, V> parent) {
             super(entry);
             this.parent = parent;
         }
 
         @Override
         public V setValue(final V value) {
             final K key = getKey();
             if (parent.reverseMap.containsKey(value) &&
                 parent.reverseMap.get(value) != key) {
                 throw new IllegalArgumentException(
                         "Cannot use setValue() when the object being set is already in the map");
             }
             parent.put(key, value);
             return super.setValue(value);
         }
     }
 
     /**
      * Inner class Values.
      *
      * @param <V> the type of the values.
      */
     protected static class Values<V> extends View<Object, V, V> implements Set<V> {
 
         /** Serialization version */
         private static final long serialVersionUID = 4023777119829639864L;
 
         /**
          * Constructs a new instance.
          *
          * @param parent  the parent BidiMap
          */
         @SuppressWarnings("unchecked")
         protected Values(final AbstractDualBidiMap<?, V> parent) {
             super(parent.normalMap.values(), (AbstractDualBidiMap<Object, V>) parent);
         }
 
         @Override
         public boolean contains(final Object value) {
             return parent.reverseMap.containsKey(value);
         }
 
         @Override
         public Iterator<V> iterator() {
             return parent.createValuesIterator(super.iterator());
         }
 
         @Override
         public boolean remove(final Object value) {
             if (parent.reverseMap.containsKey(value)) {
                 final Object key = parent.reverseMap.remove(value);
                 parent.normalMap.remove(key);
                 return true;
             }
             return false;
         }
     }
 
     /**
      * Inner class ValuesIterator.
      *
      * @param <V> the value type.
      */
     protected static class ValuesIterator<V> extends AbstractIteratorDecorator<V> {
 
         /** The parent map */
         protected final AbstractDualBidiMap<Object, V> parent;
 
         /** The last returned value */
         protected V lastValue;
 
         /** Whether remove is allowed at present */
         protected boolean canRemove;
 
         /**
          * Constructs a new instance.
          * @param iterator  the iterator to decorate
          * @param parent  the parent map
          */
         @SuppressWarnings("unchecked")
         protected ValuesIterator(final Iterator<V> iterator, final AbstractDualBidiMap<?, V> parent) {
             super(iterator);
             this.parent = (AbstractDualBidiMap<Object, V>) parent;
         }
 
         @Override
         public V next() {
             lastValue = super.next();
             canRemove = true;
             return lastValue;
         }
 
         @Override
         public void remove() {
             if (!canRemove) {
                 throw new IllegalStateException("Iterator remove() can only be called once after next()");
             }
             super.remove(); // removes from maps[0]
             parent.reverseMap.remove(lastValue);
             lastValue = null;
             canRemove = false;
         }
     }
 
     /**
      * Inner class View.
      *
      * @param <K> the type of the keys in the map.
      * @param <V> the type of the values in the map.
      * @param <E> the type of the elements in the collection.
      */
     protected abstract static class View<K, V, E> extends AbstractCollectionDecorator<E> {
 
         /** Generated serial version ID. */
         private static final long serialVersionUID = 4621510560119690639L;
 
         /** The parent map */
         protected final AbstractDualBidiMap<K, V> parent;
 
         /**
          * Constructs a new instance.
          *
          * @param coll  the collection view being decorated
          * @param parent  the parent BidiMap
          */
         protected View(final Collection<E> coll, final AbstractDualBidiMap<K, V> parent) {
             super(coll);
             this.parent = parent;
         }
 
         @Override
         public void clear() {
             parent.clear();
         }
 
         @Override
         public boolean equals(final Object object) {
             return object == this || decorated().equals(object);
         }
 
         @Override
         public int hashCode() {
             return decorated().hashCode();
         }
 
         @Override
         public boolean removeAll(final Collection<?> coll) {
             if (parent.isEmpty() || coll.isEmpty()) {
                 return false;
             }
             boolean modified = false;
             for (final Object current : coll) {
                 modified |= remove(current);
             }
             return modified;
         }
 
         /**
          * @since 4.4
          */
         @Override
         public boolean removeIf(final Predicate<? super E> filter) {
             if (parent.isEmpty() || Objects.isNull(filter)) {
                 return false;
             }
             boolean modified = false;
             final Iterator<?> it = iterator();
             while (it.hasNext()) {
                 @SuppressWarnings("unchecked")
                 final E e = (E) it.next();
                 if (filter.test(e)) {
                     it.remove();
                     modified = true;
                 }
             }
             return modified;
         }
 
         /**
          * {@inheritDoc}
          * <p>
          * This implementation iterates over the elements of this bidi map, checking each element in
          * turn to see if it's contained in {@code coll}. If it's not contained, it's removed
          * from this bidi map. As a consequence, it is advised to use a collection type for
          * {@code coll} that provides a fast (e.g. O(1)) implementation of
          * {@link Collection#contains(Object)}.
          */
         @Override
         public boolean retainAll(final Collection<?> coll) {
             if (parent.isEmpty()) {
                 return false;
             }
             if (coll.isEmpty()) {
                 parent.clear();
                 return true;
             }
             boolean modified = false;
             final Iterator<E> it = iterator();
             while (it.hasNext()) {
                 if (!coll.contains(it.next())) {
                     it.remove();
                     modified = true;
                 }
             }
             return modified;
         }
     }
 
     /**
      * Normal delegate map.
      */
     transient Map<K, V> normalMap;
 
     // Map delegation
 
     /**
      * Reverse delegate map.
      */
     transient Map<V, K> reverseMap;
 
     /**
      * Inverse view of this map.
      */
     transient BidiMap<V, K> inverseBidiMap;
 
     /**
      * View of the keys.
      */
     transient Set<K> keySet;
 
     /**
      * View of the values.
      */
     transient Set<V> values;
 
     /**
      * View of the entries.
      */
     transient Set<Map.Entry<K, V>> entrySet;
 
     /**
      * Creates an empty map, initialized by {@code createMap}.
      * <p>
      * This constructor remains in place for deserialization.
      * All other usage is deprecated in favor of
      * {@link #AbstractDualBidiMap(Map, Map)}.
      */
     protected AbstractDualBidiMap() {
     }
 
     /**
      * Creates an empty map using the two maps specified as storage.
      * <p>
      * The two maps must be a matching pair, normal and reverse.
      * They will typically both be empty.
      * <p>
      * Neither map is validated, so nulls may be passed in.
      * If you choose to do this then the subclass constructor must populate
      * the {@code maps[]} instance variable itself.
      *
      * @param normalMap  the normal direction map
      * @param reverseMap  the reverse direction map
      * @since 3.1
      */
     protected AbstractDualBidiMap(final Map<K, V> normalMap, final Map<V, K> reverseMap) {
         this.normalMap = normalMap;
         this.reverseMap = reverseMap;
     }
 
     // BidiMap changes
 
     /**
      * Constructs a map that decorates the specified maps,
      * used by the subclass {@code createBidiMap} implementation.
      *
      * @param normalMap  the normal direction map
      * @param reverseMap  the reverse direction map
      * @param inverseBidiMap  the inverse BidiMap
      */
     protected AbstractDualBidiMap(final Map<K, V> normalMap, final Map<V, K> reverseMap,
                                   final BidiMap<V, K> inverseBidiMap) {
         this.normalMap = normalMap;
         this.reverseMap = reverseMap;
         this.inverseBidiMap = inverseBidiMap;
     }
 
     @Override
     public void clear() {
         normalMap.clear();
         reverseMap.clear();
     }
 
     @Override
     public boolean containsKey(final Object key) {
         return normalMap.containsKey(key);
     }
 
     @Override
     public boolean containsValue(final Object value) {
         return reverseMap.containsKey(value);
     }
 
     /**
      * Creates a new instance of the subclass.
      *
      * @param normalMap  the normal direction map
      * @param reverseMap  the reverse direction map
      * @param inverseMap  this map, which is the inverse in the new map
      * @return the bidi map
      */
     protected abstract BidiMap<V, K> createBidiMap(Map<V, K> normalMap, Map<K, V> reverseMap, BidiMap<K, V> inverseMap);
 
     /**
      * Creates an entry set iterator.
      * Subclasses can override this to return iterators with different properties.
      *
      * @param iterator  the iterator to decorate
      * @return the entrySet iterator
      */
     protected Iterator<Map.Entry<K, V>> createEntrySetIterator(final Iterator<Map.Entry<K, V>> iterator) {
         return new EntrySetIterator<>(iterator, this);
     }
 
     /**
      * Creates a key set iterator.
      * Subclasses can override this to return iterators with different properties.
      *
      * @param iterator  the iterator to decorate
      * @return the keySet iterator
      */
     protected Iterator<K> createKeySetIterator(final Iterator<K> iterator) {
         return new KeySetIterator<>(iterator, this);
     }
 
     /**
      * Creates a values iterator.
      * Subclasses can override this to return iterators with different properties.
      *
      * @param iterator  the iterator to decorate
      * @return the values iterator
      */
     protected Iterator<V> createValuesIterator(final Iterator<V> iterator) {
         return new ValuesIterator<>(iterator, this);
     }
 
     /**
      * Gets an entrySet view of the map.
      * Changes made on the set are reflected in the map.
      * The set supports remove and clear but not add.
      * <p>
      * The Map Entry setValue() method only allow a new value to be set.
      * If the value being set is already in the map, an IllegalArgumentException
      * is thrown (as setValue cannot change the size of the map).
      * </p>
      *
      * @return the entrySet view
      */
     @Override
     public Set<Map.Entry<K, V>> entrySet() {
         if (entrySet == null) {
             entrySet = new EntrySet<>(this);
         }
         return entrySet;
     }
 
     @Override
     public boolean equals(final Object obj) {
         return normalMap.equals(obj);
     }
 
     @Override
     public V get(final Object key) {
         return normalMap.get(key);
     }
 
     @Override
     public K getKey(final Object value) {
         return reverseMap.get(value);
     }
 
     @Override
     public int hashCode() {
         return normalMap.hashCode();
     }
 
     @Override
     public BidiMap<V, K> inverseBidiMap() {
         if (inverseBidiMap == null) {
             inverseBidiMap = createBidiMap(reverseMap, normalMap, this);
         }
         return inverseBidiMap;
     }
 
     @Override
     public boolean isEmpty() {
         return normalMap.isEmpty();
     }
 
     // Map views
     /**
      * Gets a keySet view of the map.
      * Changes made on the view are reflected in the map.
      * The set supports remove and clear but not add.
      *
      * @return the keySet view
      */
     @Override
     public Set<K> keySet() {
         if (keySet == null) {
             keySet = new KeySet<>(this);
         }
         return keySet;
     }
 
     // BidiMap
     /**
      * Obtains a {@code MapIterator} over the map.
      * The iterator implements {@link BidiMapIterator}.
      * This implementation relies on the entrySet iterator.
      *
      * @return a map iterator
      */
     @Override
     public MapIterator<K, V> mapIterator() {
         return new BidiMapIterator<>(this);
     }
 
     @Override
     public V put(final K key, final V value) {
         if (normalMap.containsKey(key)) {
             reverseMap.remove(normalMap.get(key));
         }
         if (reverseMap.containsKey(value)) {
             normalMap.remove(reverseMap.get(value));
         }
         final V obj = normalMap.put(key, value);
         reverseMap.put(value, key);
         return obj;
     }
 
     @Override
     public void putAll(final Map<? extends K, ? extends V> map) {
         for (final Map.Entry<? extends K, ? extends V> entry : map.entrySet()) {
             put(entry.getKey(), entry.getValue());
         }
     }
 
     @Override
     public V remove(final Object key) {
         V value = null;
         if (normalMap.containsKey(key)) {
             value = normalMap.remove(key);
             reverseMap.remove(value);
         }
         return value;
     }
 
     @Override
     public K removeValue(final Object value) {
         K key = null;
         if (reverseMap.containsKey(value)) {
             key = reverseMap.remove(value);
             normalMap.remove(key);
         }
         return key;
     }
 
     @Override
     public int size() {
         return normalMap.size();
     }
 
     @Override
     public String toString() {
         return normalMap.toString();
     }
 
     /**
      * Gets a values view of the map.
      * Changes made on the view are reflected in the map.
      * The set supports remove and clear but not add.
      *
      * @return the values view
      */
     @Override
     public Set<V> values() {
         if (values == null) {
             values = new Values<>(this);
         }
         return values;
     }
 
 }