/*
 * Copyright (c) 1998-2011 Caucho Technology -- all rights reserved
 *
 * This file is part of Resin(R) Open Source
 *
 * Each copy or derived work must preserve the copyright notice and this
 * notice unmodified.
 *
 * Resin Open Source is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Resin Open Source 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, or any warranty
 * of NON-INFRINGEMENT.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Resin Open Source; if not, write to the
 *
 *   Free Software Foundation, Inc.
 *   59 Temple Place, Suite 330
 *   Boston, MA 02111-1307  USA
 *
 * @author Scott Ferguson
 */

package com.caucho.jms.file;

import java.io.Serializable;
import java.security.MessageDigest;

import javax.jms.Topic;

import com.caucho.jms.queue.AbstractMemoryQueue;
import com.caucho.loader.Environment;
import com.caucho.server.cluster.Server;
import com.caucho.util.Hex;
import com.caucho.vfs.Path;

/**
 * A JMS queue backed by a file-based database.
 *
 * The URL looks like
 * <pre>
 * file:name=my-name;path=file:/var/www/webapps/test/WEB-INF/jms
 * </pre>
 *
 * It is configured as:
 * <pre>
 * <web-app xmlns="http://caucho.com/ns/resin"
 *             xmlns:resin="urn:java:com.caucho.resin">
 *
 *   <resin:FileQueue>
 *     <resin:JndiName>jms/my-name</resin:JndiName>
 *
 *     <resin:name>my-name</resin:name>
 *     <resin:path>WEB-INF/jms</resin:path>
 *   </resin:FileQueue>
 *
 * </web-app>
 * </pre>
 */
public class FileQueueImpl<E extends Serializable>
  extends AbstractMemoryQueue<E,FileQueueEntry<E>>
  implements Topic
{
  private final FileQueueStore _store;

  private byte []_queueIdHash;

  public FileQueueImpl()
  {
    _store = FileQueueStore.create();
  }

  public FileQueueImpl(byte []queueHash)
  {
    this();
    
    setName(Hex.toHex(queueHash, 0, 8));

    _queueIdHash = queueHash;

    init();
  }

  public FileQueueImpl(String name)
  {
    this();
    
    setName(name);

    init();
  }

  FileQueueImpl(Path path, String name, String serverId)
  {
    try {
      path.mkdirs();
    } catch (Exception e) {
    }

    if (serverId == null)
      serverId = "anon";
    
    ClassLoader loader = Thread.currentThread().getContextClassLoader();
    _store = new FileQueueStore(path, serverId, loader);

    setName(name);

    init();
  }

  //
  // Configuration
  //

  /**
   * Backward compatibility
   */
  @Deprecated
  public void setPath(Path path)
  {
  }

  public Path getPath()
  {
    return null;
  }

  /**
   * Backward compatibility
   */
  @Deprecated
  public void setTablePrefix(String prefix)
  {
    
  }

  /**
   * Returns the JMS configuration url.
   */
  public String getUrl()
  {
    return "file:name=" + getName();
  }

  /**
   * Initialize the queue
   */
  public void init()
  {
    try {
      // calculate a unique hash for the queue
      
      if (_queueIdHash == null) {
        MessageDigest digest = MessageDigest.getInstance("SHA-256");

        String env = Environment.getEnvironmentName();

        digest.update(env.getBytes());

        if (Server.getCurrent() != null)
          digest.update(Server.getCurrent().getServerId().getBytes());

        digest.update(getClass().getSimpleName().getBytes());
        digest.update(getName().getBytes());

        _queueIdHash = digest.digest();
      }
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
      
    _store.receiveStart(_queueIdHash, this);
  }
  
  /**
   * Adds the message to the persistent store.  Called if there are no
   * active listeners.
   *
   * @param msgId the queue's unique identifier for the message
   * @param payload the message payload to store
   * @param priority the message priority
   * @param expireTime the expires time
   */
  @Override
  public FileQueueEntry<E> writeEntry(String msgId,
                                      E payload,
                                      int priority,
                                      long expireTime)
  {
    long id = _store.send(_queueIdHash, msgId, payload, priority, expireTime);

    long leaseTimeout = -1;

    FileQueueEntry<E> entry
      = new FileQueueEntry<E>(id, msgId, leaseTimeout,
                              priority, expireTime, payload);

    return entry;
  }

  @Override
  protected void readPayload(FileQueueEntry<E> entry)
  {
    E payload = entry.getPayload();

    if (payload == null) {
      payload = entry.getPayloadRef();

      if (payload == null)
        payload = (E) _store.readMessage(entry.getId());
      
      entry.setPayload(payload);
    }
  }

  @Override
  protected void acknowledge(FileQueueEntry<E> entry)
  {
    _store.delete(entry.getId());
  }

  /**
   * Callback from startup
   */
  protected void addEntry(long id,
                          String msgId,
                          long leaseTimeout,
                          int priority,
                          long expireTime,
                          E payload)
  {
    FileQueueEntry<E> entry
      = new FileQueueEntry<E>(id, msgId, leaseTimeout,
                              priority, expireTime, payload);

    addQueueEntry(entry, expireTime);
  }
  
  /**
   * Statistics
   */
  public int getFileStoreMessageCount()
  {
    return _store.getMessageCount();
  }
}