/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2006, Red Hat Middleware LLC, and individual contributors
 * as indicated by the @author tags. See the copyright.txt file in the
 * distribution for a full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.jboss.tm;

import java.net.InetAddress;
import javax.transaction.xa.Xid;
import java.net.UnknownHostException;

/**
 * XidFactory.java
 *
 *
 * Created: Sat Jun 15 19:01:18 2002
 *
 * @author <a href="mailto:d_jencks@users.sourceforge.net">David Jencks</a>
 * @version
 *
 * @jmx.mbean
 */
public class XidFactory implements XidFactoryMBean
{
   /**
    *  The default value of baseGlobalId is the host name of this host, 
    *  followed by a slash.
    *
    *  This is used for building globally unique transaction identifiers.
    *  It would be safer to use the IP address, but a host name is better
    *  for humans to read and will do for now.
    * This must be set individually if multiple jboss instances are 
    * running on the same machine.
    */
   private String baseGlobalId;

   /**
    *  The next transaction id to use on this host.
    */
   private long globalIdNumber = 0;

   /**
    * The variable <code>pad</code> says whether the byte[] should be their
    * maximum 64 byte length or the minimum.  
    * The max length is required for Oracle..
    */
   private boolean pad = false;

   /**
    * The variable <code>noBranchQualifier</code> is the 1 or 64 byte zero 
    * array used for initial xids.
    */
   private byte[] noBranchQualifier = new byte[1]; // len > 0, per the XA spec

   /**
    * This field stores the byte reprsentation of baseGlobalId
    * to avoid the expensive getBytes() call on this String object
    * when we create a new Xid, which we do VERY often!
    */
   private byte[] baseGlobalIdBytes;
   
   public XidFactory() 
   {
      try
      {
         baseGlobalId = InetAddress.getLocalHost().getHostName();
         // Ensure room for 14 digits of serial no.
         if (baseGlobalId.length() > Xid.MAXGTRIDSIZE - 15)
            baseGlobalId = baseGlobalId.substring(0, Xid.MAXGTRIDSIZE - 15);
         baseGlobalId = baseGlobalId + "/";
      }
      catch (UnknownHostException e)
      {
         baseGlobalId = "localhost/";
      }
      baseGlobalIdBytes = baseGlobalId.getBytes();
   }
   
   /**
    * mbean get-set pair for field BaseGlobalId
    * Get the value of BaseGlobalId
    * @return value of BaseGlobalId
    *
    * @jmx:managed-attribute
    */
   public String getBaseGlobalId()
   {
      return baseGlobalId;
   }
   
   /**
    * Set the value of BaseGlobalId
    * @param BaseGlobalId  Value to assign to BaseGlobalId
    *
    * @jmx:managed-attribute
    */
   public void setBaseGlobalId(final String baseGlobalId)
   {
      this.baseGlobalId = baseGlobalId;
      baseGlobalIdBytes = baseGlobalId.getBytes();
   }
   
   /**
    * mbean get-set pair for field globalIdNumber
    * Get the value of globalIdNumber
    * @return value of globalIdNumber
    *
    * @jmx:managed-attribute
    */
   public synchronized long getGlobalIdNumber()
   {
      return globalIdNumber;
   }
   
   /**
    * Set the value of globalIdNumber
    * @param globalIdNumber  Value to assign to globalIdNumber
    *
    * @jmx:managed-attribute
    */
   public synchronized void setGlobalIdNumber(final long globalIdNumber)
   {
      this.globalIdNumber = globalIdNumber;
   }
   
   /**
    * mbean get-set pair for field pad
    * Get the value of pad
    * @return value of pad
    *
    * @jmx:managed-attribute
    */
   public boolean isPad()
   {
      return pad;
   }
   
   /**
    * Set the value of pad
    * @param pad  Value to assign to pad
    *
    * @jmx:managed-attribute
    */
   public void setPad(boolean pad)
   {
      this.pad = pad;
      if (pad) 
         noBranchQualifier = new byte[Xid.MAXBQUALSIZE];
      else
         noBranchQualifier = new byte[1]; // length > 0, per the XA spec
   }
   
   /**
    * mbean get-set pair for field instance
    * Get the value of instance
    * @return value of instance
    *
    * @jmx:managed-attribute
    */
   public XidFactoryMBean getInstance()
   {
      return this;
   }
   
   /**
    * Describe <code>newXid</code> method here.
    *
    * @return a <code>XidImpl</code> value
    * @jmx.managed-operation
    */
   public XidImpl newXid()
   {
      long localId = getNextId();
      String id = Long.toString(localId);
      int len = pad?Xid.MAXGTRIDSIZE:id.length()+baseGlobalIdBytes.length;
      byte[] globalId = new byte[len];
      System.arraycopy(baseGlobalIdBytes, 0, globalId, 0, baseGlobalIdBytes.length);
      // this method is deprecated, but does exactly what we need in a very fast way
      // the default conversion from String.getBytes() is way too expensive
      id.getBytes(0, id.length(), globalId, baseGlobalIdBytes.length);
      return new XidImpl(globalId, noBranchQualifier, (int)localId, localId);
   }

   /**
    * Describe <code>newBranch</code> method here.
    *
    * @param xid a <code>XidImpl</code> value
    * @param branchIdNum a <code>long</code> value
    * @return a <code>XidImpl</code> value
    * @jmx.managed-operation
    */
   public XidImpl newBranch(XidImpl xid, long branchIdNum)
   {
      String id = Long.toString(branchIdNum);
      int len = pad?Xid.MAXBQUALSIZE:id.length();
      byte[] branchId = new byte[len];
      // this method is deprecated, but does exactly what we need in a very fast way
      // the default conversion from String.getBytes() is way too expensive
      id.getBytes(0, id.length(), branchId, 0);
      return new XidImpl(xid, branchId);
   }


   /**
    * Extracts the local id contained in a global id.
    *
    * @param globalId a global id
    * @return the local id extracted from the global id
    * @jmx:managed-operation
    */
   public long extractLocalIdFrom(byte[] globalId)
   {
      int i, start;
      int len = globalId.length;
      
      for (i = 0; globalId[i++] != (byte)'/'; )
         ;
      start = i;
      while (i < len && globalId[i] != 0)
         i++;
      String globalIdNumber = new String(globalId, 0, start, i - start);
      return Long.parseLong(globalIdNumber);
   }
   

   /**
    * Describe <code>toString</code> method here.
    *
    * @param xid a <code>Xid</code> value
    * @return a <code>String</code> value
    * @jmx.managed-operation
    */
   public String toString(Xid xid)
   {
      if (xid instanceof XidImpl) 
         return XidImpl.toString(xid);
      else
         return xid.toString();
   }

   private synchronized long getNextId()
   {
      return ++globalIdNumber;
   }

}