/*

 * Copyright (c) 2010, 2011, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/*

 *******************************************************************************

 * Copyright (C) 2009-2010, International Business Machines Corporation and    *

 * others. All Rights Reserved.                                                *

 *******************************************************************************

 */

package sun.util.locale;

import java.lang.ref.ReferenceQueue;

import java.lang.ref.SoftReference;

import java.util.concurrent.ConcurrentHashMap;

import java.util.concurrent.ConcurrentMap;

public abstract class LocaleObjectCache<K, V> {

    private ConcurrentMap<K, CacheEntry<K, V>> map;

    private ReferenceQueue<V> queue = new ReferenceQueue<>();

    public LocaleObjectCache() {

        this(16, 0.75f, 16);

    }

    public LocaleObjectCache(int initialCapacity, float loadFactor, int concurrencyLevel) {

        map = new ConcurrentHashMap<>(initialCapacity, loadFactor, concurrencyLevel);

    }

    public V get(K key) {

        V value = null;

        cleanStaleEntries();

        CacheEntry<K, V> entry = map.get(key);

        if (entry != null) {

            value = entry.get();

        }

        if (value == null) {

            key = normalizeKey(key);

            if (key == null || newVal == null) {

                // subclass must return non-null key/value object

                return null;

            }

            CacheEntry<K, V> newEntry = new CacheEntry<>(key, newVal, queue);

            entry = map.putIfAbsent(key, newEntry);

            if (entry == null) {

                value = newVal;

            } else {

                value = entry.get();

                if (value == null) {

                    map.put(key, newEntry);

                    value = newVal;

                }

            }

        }

        return value;

    }

    protected V put(K key, V value) {

        CacheEntry<K, V> entry = new CacheEntry<>(key, value, queue);

        CacheEntry<K, V> oldEntry = map.put(key, entry);

        return (oldEntry == null) ? null : oldEntry.get();

    }

    @SuppressWarnings("unchecked")

    private void cleanStaleEntries() {

        CacheEntry<K, V> entry;

        while ((entry = (CacheEntry<K, V>)queue.poll()) != null) {

            map.remove(entry.getKey());

        }

    }

    protected abstract V createObject(K key);

    protected K normalizeKey(K key) {

        return key;

    }

    private static class CacheEntry<K, V> extends SoftReference<V> {

        private K key;

        CacheEntry(K key, V value, ReferenceQueue<V> queue) {

            super(value, queue);

            this.key = key;

        }

        K getKey() {

            return key;

        }

    }

}