/*
 * 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.wicket.util.collections;

import java.io.Serializable;
import java.util.AbstractList;
import java.util.AbstractSet;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;

/**
 * An implementation of the java.util.Map interface which can only hold a single object. This is
 * particularly useful to control memory usage in Wicket because many containers hold only a single
 * component.
 *
 * @author Jonathan Locke
 * @param <K>
 *            Key type
 * @param <V>
 *            Value type
 *
 * @deprecated Please use {@link Map#of(Object, Object)} instead
 */
@Deprecated(forRemoval = true, since = "9.0.0")
public final class MicroMap<K, V> implements Map<K, V>, Serializable
{
        private static final long serialVersionUID = 1L;

        /** The maximum number of entries this map supports. */
        public static final int MAX_ENTRIES = 1;

        /** The one and only key in this tiny map */
        private K key;

        /** The value for the only key in this tiny map */
        private V value;

        /**
         * Constructor
         */
        public MicroMap()
        {
        }

        /**
         * Constructs map with a single key and value pair.
         *
         * @param key
         *            The key
         * @param value
         *            The value
         */
        public MicroMap(final K key, final V value)
        {
                put(key, value);
        }

        /**
         * @return True if this MicroMap is full
         */
        public boolean isFull()
        {
                return size() == MAX_ENTRIES;
        }

        /**
         * @see java.util.Map#size()
         */
        @Override
        public int size()
        {
                return (key != null) ? 1 : 0;
        }

        /**
         * @see java.util.Map#isEmpty()
         */
        @Override
        public boolean isEmpty()
        {
                return size() == 0;
        }

        /**
         * @see java.util.Map#containsKey(java.lang.Object)
         */
        @Override
        public boolean containsKey(final Object key)
        {
                return key.equals(this.key);
        }

        /**
         * @see java.util.Map#containsValue(java.lang.Object)
         */
        @Override
        public boolean containsValue(final Object value)
        {
                return value.equals(this.value);
        }

        /**
         * @see java.util.Map#get(java.lang.Object)
         */
        @Override
        public V get(final Object key)
        {
                if (key.equals(this.key))
                {
                        return value;
                }

                return null;
        }

        /**
         * @see java.util.Map#put(java.lang.Object, java.lang.Object)
         */
        @Override
        public V put(final K key, final V value)
        {
                // Replace?
                if (key.equals(this.key))
                {
                        final V oldValue = this.value;

                        this.value = value;

                        return oldValue;
                }
                else
                {
                        // Is there room for a new entry?
                        if (size() < MAX_ENTRIES)
                        {
                                // Store
                                this.key = key;
                                this.value = value;

                                return null;
                        }
                        else
                        {
                                throw new IllegalStateException("Map full");
                        }
                }
        }

        /**
         * @see java.util.Map#remove(java.lang.Object)
         */
        @Override
        public V remove(final Object key)
        {
                if (key.equals(this.key))
                {
                        final V oldValue = value;

                        this.key = null;
                        value = null;

                        return oldValue;
                }

                return null;
        }

        /**
         * @see java.util.Map#putAll(java.util.Map)
         */
        @Override
        public void putAll(final Map<? extends K, ? extends V> map)
        {
                if (map.size() <= MAX_ENTRIES)
                {
                        final Entry<? extends K, ? extends V> e = map.entrySet().iterator().next();

                        put(e.getKey(), e.getValue());
                }
                else
                {
                        throw new IllegalStateException("Map full.  Cannot add " + map.size() + " entries");
                }
        }

        /**
         * @see java.util.Map#clear()
         */
        @Override
        public void clear()
        {
                key = null;
                value = null;
        }

        /**
         * @see java.util.Map#keySet()
         */
        @Override
        public Set<K> keySet()
        {
                return new AbstractSet<K>()
                {
                        @Override
                        public Iterator<K> iterator()
                        {
                                return new Iterator<K>()
                                {
                                        @Override
                                        public boolean hasNext()
                                        {
                                                return index < MicroMap.this.size();
                                        }

                                        @Override
                                        public K next()
                                        {
                                                if (!hasNext())
                                                {
                                                        throw new NoSuchElementException();
                                                }
                                                index++;

                                                return key;
                                        }

                                        @Override
                                        public void remove()
                                        {
                                                MicroMap.this.clear();
                                        }

                                        int index;
                                };
                        }

                        @Override
                        public int size()
                        {
                                return MicroMap.this.size();
                        }
                };
        }

        /**
         * @see java.util.Map#values()
         */
        @Override
        public Collection<V> values()
        {
                return new AbstractList<V>()
                {
                        @Override
                        public V get(final int index)
                        {
                                if (index > size() - 1)
                                {
                                        throw new IndexOutOfBoundsException();
                                }
                                return value;
                        }

                        @Override
                        public int size()
                        {
                                return MicroMap.this.size();
                        }
                };
        }

        /**
         * @see java.util.Map#entrySet()
         */
        @Override
        public Set<Entry<K, V>> entrySet()
        {
                return new AbstractSet<Entry<K, V>>()
                {
                        @Override
                        public Iterator<Entry<K, V>> iterator()
                        {
                                return new Iterator<Entry<K, V>>()
                                {
                                        @Override
                                        public boolean hasNext()
                                        {
                                                return index < MicroMap.this.size();
                                        }

                                        @Override
                                        public Entry<K, V> next()
                                        {
                                                if (!hasNext())
                                                {
                                                        throw new NoSuchElementException();
                                                }
                                                index++;

                                                return new Map.Entry<K, V>()
                                                {
                                                        @Override
                                                        public K getKey()
                                                        {
                                                                return key;
                                                        }

                                                        @Override
                                                        public V getValue()
                                                        {
                                                                return value;
                                                        }

                                                        @Override
                                                        public V setValue(final V value)
                                                        {
                                                                final V oldValue = MicroMap.this.value;

                                                                MicroMap.this.value = value;

                                                                return oldValue;
                                                        }
                                                };
                                        }

                                        @Override
                                        public void remove()
                                        {
                                                clear();
                                        }

                                        int index = 0;
                                };
                        }

                        @Override
                        public int size()
                        {
                                return MicroMap.this.size();
                        }
                };
        }
}