/**
 *
 * Copyright © 2014-2023 Florian Schmaus
 *
 * 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 org.jxmpp.util.cache;

import java.util.Collection;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

/**
 * A cache which expires its values.
 *
 * @param <K> the type of the keys of this cache.
 * @param <V> the type of the values this cache caches.
 */
public class ExpirationCache<K, V> implements Cache<K, V>, Map<K, V>{

        private final LruCache<K, ExpireElement<V>> cache;

        private long defaultExpirationTime;

        /**
         * Construct a new expiration cache.
         *
         * @param maxSize the maximum size.
         * @param defaultExpirationTime the default expiration time in milliseconds.
         */
        public ExpirationCache(int maxSize, long defaultExpirationTime) {
                cache = new LruCache<K, ExpireElement<V>>(maxSize);
                setDefaultExpirationTime(defaultExpirationTime);
        }

        /**
         * Set the default expiration time in milliseconds.
         *
         * @param defaultExpirationTime the default expiration time.
         */
        public final void setDefaultExpirationTime(long defaultExpirationTime) {
                if (defaultExpirationTime <= 0) {
                        throw new IllegalArgumentException();
                }
                this.defaultExpirationTime = defaultExpirationTime;
        }

        @Override
        public V put(K key, V value) {
                return put(key, value, defaultExpirationTime);
        }

        /**
         * Put a value in the cache with the specified expiration time in milliseconds.
         *
         * @param key the key of the value.
         * @param value the value.
         * @param expirationTime the expiration time in milliseconds.
         * @return the previous value or {@code null}.
         */
        public V put(K key, V value, long expirationTime) {
                ExpireElement<V> eOld = cache.put(key, new ExpireElement<V>(value, expirationTime));
                if (eOld == null) {
                        return null;
                }
                return eOld.element;
        }

    @Override
    public V lookup(K key) {
        return get(key);
    }

    @Override
        public V get(Object key) {
                ExpireElement<V> v = cache.get(key);
                if (v == null) {
                        return null;
                }
                if (v.isExpired()) {
                        remove(key);
                        return null;
                }
                return v.element;
        }

        /**
         * Remove a entry with the given key from the cache.
         * 
         * @param key the key of the value to remove.
         * @return the remove value, or {@code null}.
         */
        @Override
        public V remove(Object key) {
                ExpireElement<V> e = cache.remove(key);
                if (e == null) {
                        return null;
                }
                return e.element;
        }

        @Override
        public int getMaxCacheSize() {
                return cache.getMaxCacheSize();
        }

        @Override
        public void setMaxCacheSize(int maxCacheSize) {
                cache.setMaxCacheSize(maxCacheSize);
        }

        private static class ExpireElement<V> {
                private final V element;
                private final long expirationTimestamp;

                private ExpireElement(V element, long expirationTime) {
                        this.element = element;
                        this.expirationTimestamp = System.currentTimeMillis() + expirationTime;
                }

                private boolean isExpired() {
                        return System.currentTimeMillis() > expirationTimestamp;
                }

                @Override
                public int hashCode() {
                        return element.hashCode();
                }

                @Override
                public boolean equals(Object other) {
                        if (!(other instanceof ExpireElement))
                                return false;
                        ExpireElement<?> otherElement = (ExpireElement<?>) other;
                        return element.equals(otherElement.element);
                }
        }

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

        @Override
        public boolean isEmpty() {
                return cache.isEmpty();
        }

        @Override
        public boolean containsKey(Object key) {
                return cache.containsKey(key);
        }

        @Override
        public boolean containsValue(Object value) {
                return cache.containsValue(value);
        }

        @Override
        public void putAll(Map<? extends K, ? extends V> m) {
                for (Entry<? extends K, ? extends V> entry : m.entrySet()) {
                        put(entry.getKey(), entry.getValue());
                }
        }

        @Override
        public void clear() {
                cache.clear();
        }

        @Override
        public Set<K> keySet() {
                return cache.keySet();
        }

        @Override
        public Collection<V> values() {
                Set<V> res = new HashSet<V>();
                for (ExpireElement<V> value : cache.values()) {
                        res.add(value.element);
                }
                return res;
        }

        @Override
        public Set<java.util.Map.Entry<K, V>> entrySet() {
                Set<Entry<K, V>> res = new HashSet<Entry<K, V>>();
                for (Entry<K, ExpireElement<V>> entry : cache.entrySet()) {
                        res.add(new EntryImpl<K, V>(entry.getKey(), entry.getValue().element));
                }
                return res;
        }

        private static class EntryImpl<K, V> implements Entry<K, V> {

                private final K key;
                private V value;

                EntryImpl(K key, V value) {
                        this.key = key;
                        this.value = value;
                }
                @Override
                public K getKey() {
                        return key;
                }

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

                @Override
                public V setValue(V value) {
                        V oldValue = this.value;
                        this.value = value;
                        return oldValue;
                }
        }
}