/*
 * 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.activemq.artemis.core.paging.cursor.impl;

import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

import org.apache.activemq.artemis.core.paging.PagedMessage;
import org.apache.activemq.artemis.core.paging.cursor.PageCache;
import org.apache.activemq.artemis.core.paging.impl.Page;

/**
 * The caching associated to a single page.
 */
class PageCacheImpl implements PageCache {

   // Constants -----------------------------------------------------

   // Attributes ----------------------------------------------------

   private final ReadWriteLock lock = new ReentrantReadWriteLock();

   private PagedMessage[] messages;

   private final Page page;

   // Static --------------------------------------------------------

   // Constructors --------------------------------------------------

   public PageCacheImpl(final Page page) {
      this.page = page;
   }

   // Public --------------------------------------------------------

   @Override
   public PagedMessage getMessage(final int messageNumber) {
      lock.readLock().lock();
      try {
         if (messageNumber < messages.length) {
            return messages[messageNumber];
         }
         else {
            return null;
         }
      }
      finally {
         lock.readLock().unlock();
      }
   }

   public long getPageId() {
      return page.getPageId();
   }

   public void lock() {
      lock.writeLock().lock();
   }

   public void unlock() {
      lock.writeLock().unlock();
   }

   public void setMessages(final PagedMessage[] messages) {
      this.messages = messages;
   }

   public int getNumberOfMessages() {
      lock.readLock().lock();
      try {
         return messages.length;
      }
      finally {
         lock.readLock().unlock();
      }
   }

   public void close() {
   }

   @Override
   public boolean isLive() {
      return false;
   }

   @Override
   public String toString() {
      return "PageCacheImpl::page=" + page.getPageId() + " numberOfMessages = " + messages.length;
   }

   @Override
   public PagedMessage[] getMessages() {
      return messages;
   }
}
