/*
 * JBoss, the OpenSource J2EE webOS
 *
 * Distributable under LGPL license.
 * See terms of license at gnu.org.
 */
package org.jboss.tm;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

import javax.transaction.Status;
import javax.transaction.TransactionManager;
import javax.transaction.Transaction;
import javax.transaction.NotSupportedException;
import javax.transaction.SystemException;
import javax.transaction.RollbackException;
import javax.transaction.HeuristicMixedException;
import javax.transaction.HeuristicRollbackException;
import javax.transaction.InvalidTransactionException;

import org.jboss.logging.Logger;

/**
 * Our TransactionManager implementation.
 *
 * @author <a href="mailto:rickard.oberg@telkel.com">Rickard Öberg</a>
 * @author <a href="mailto:marc.fleury@telkel.com">Marc Fleury</a>
 * @author <a href="mailto:osh@sparre.dk">Ole Husgaard</a>
 * @author <a href="mailto:jason@planet57.com">Jason Dillon</a>
 * @version $Revision: 1.3.2.8 $
 */
public class TxManager
      implements TransactionManager,
      TransactionPropagationContextImporter,
      TransactionPropagationContextFactory
{
   // Constants -----------------------------------------------------

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

   /** Instance logger. */
   private Logger log = Logger.getLogger(this.getClass());

   /** True if trace messages should be logged. */
   private boolean trace = log.isTraceEnabled();

   /**
    *  Default timeout in milliseconds.
    *  Must be >= 1000!
    */
   private long timeOut = 5 * 60 * 1000;

   // The following two fields are ints (not longs) because
   // volatile 64Bit types are broken (i.e. access is not atomic) in most VMs, and we
   // don't want to lock just for a statistic. Additionaly,
   // it will take several years on a highly loaded system to
   // exceed the int range. Note that we might loose an
   // increment every now and then, since the ++ operation is
   // not atomic on volatile data types.
   /** A count of the transactions that have been committed */
   private volatile int commitCount;
   /** A count of the transactions that have been rolled back */
   private volatile int rollbackCount;

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

   /**
    *  The singleton instance.
    */
   private static TxManager singleton = new TxManager();

   /**
    *  Get a reference to the singleton instance.
    */
   public static TxManager getInstance()
   {
      return singleton;
   }

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

   /**
    *  Private constructor for singleton. Use getInstance() to obtain
    *  a reference to the singleton.
    */
   private TxManager()
   {
      //make sure TxCapsule can be used
      TransactionImpl.defaultXidFactory();
   }

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

   /**
    *  Begin a new transaction.
    *  The new transaction will be associated with the calling thread.
    */
   public void begin()
         throws NotSupportedException, SystemException
   {
      ThreadInfo ti = getThreadInfo();
      TransactionImpl current = ti.tx;

      if (current != null)
      {
         if (current.isDone())
            disassociateThread(ti);
         else
            throw new NotSupportedException
                  ("Transaction already active, cannot nest transactions.");
      }

      long timeout = (ti.timeout == 0) ? timeOut : ti.timeout;
      TransactionImpl tx = new TransactionImpl(timeout);
      associateThread(ti, tx);
      globalIdTx.put(tx.getGlobalId(), tx);

      if (trace)
         log.trace("began tx: " + tx);
   }

   /**
    *  Commit the transaction associated with the currently running thread.
    */
   public void commit()
         throws RollbackException,
         HeuristicMixedException,
         HeuristicRollbackException,
         SecurityException,
         IllegalStateException,
         SystemException
   {
      ThreadInfo ti = getThreadInfo();
      TransactionImpl current = ti.tx;

      if (current != null)
      {
         current.commit();
         disassociateThread(ti);
         if (trace)
            log.trace("commited tx: " + current);
      }
      else
         throw new IllegalStateException("No transaction.");
   }

   /**
    *  Return the status of the transaction associated with the currently
    *  running thread, or <code>Status.STATUS_NO_TRANSACTION</code> if no
    *  active transaction is currently associated.
    */
   public int getStatus() throws SystemException
   {
      ThreadInfo ti = getThreadInfo();
      TransactionImpl current = ti.tx;

      if (current != null)
      {
         if (current.isDone())
            disassociateThread(ti);
         else
            return current.getStatus();
      }
      return Status.STATUS_NO_TRANSACTION;
   }

   /**
    *  Return the transaction currently associated with the invoking thread,
    *  or <code>null</code> if no active transaction is currently associated.
    */
   public Transaction getTransaction() throws SystemException
   {
      ThreadInfo ti = getThreadInfo();
      TransactionImpl current = ti.tx;

      if (current != null && current.isDone())
      {
         current = null;
         disassociateThread(ti);
      }

      return current;
   }

   /**
    *  Resume a transaction.
    *
    *  Note: This will not enlist any resources involved in this
    *  transaction. According to JTA1.0.1 specification section 3.2.3,
    *  that is the responsibility of the application server.
    */
   public void resume(Transaction transaction)
         throws InvalidTransactionException,
         IllegalStateException,
         SystemException
   {
      if (transaction != null && !(transaction instanceof TransactionImpl))
         throw new RuntimeException("Not a TransactionImpl, but a " +
               transaction.getClass().getName());

      ThreadInfo ti = getThreadInfo();
      TransactionImpl current = ti.tx;

      if (current != null)
      {
         if (current.isDone())
            current = ti.tx = null;
         else
            throw new IllegalStateException("Already associated with a tx");
      }

      if (current != transaction)
      {
         associateThread(ti, (TransactionImpl)transaction);
      }

      if (trace)
         log.trace("resumed tx: " + ti.tx);
   }

   /**
    *  Suspend the transaction currently associated with the current
    *  thread, and return it.
    *
    *  Note: This will not delist any resources involved in this
    *  transaction. According to JTA1.0.1 specification section 3.2.3,
    *  that is the responsibility of the application server.
    */
   public Transaction suspend() throws SystemException
   {
      ThreadInfo ti = getThreadInfo();
      TransactionImpl current = ti.tx;

      if (current != null)
      {
         ti.tx = null;

         if (trace)
            log.trace("suspended tx: " + current);

         if (current.isDone())
            current = null;
      }

      return current;
   }

   /**
    *  Roll back the transaction associated with the currently running thread.
    */
   public void rollback()
         throws IllegalStateException, SecurityException, SystemException
   {
      ThreadInfo ti = getThreadInfo();
      TransactionImpl current = ti.tx;

      if (current != null)
      {
         if (!current.isDone())
         {
            current.rollback();

            if (trace)
               log.trace("rolled back tx: " + current);
            return;
         }
         disassociateThread(ti);
      }
      throw new IllegalStateException("No transaction.");
   }

   /**
    *  Mark the transaction associated with the currently running thread
    *  so that the only possible outcome is a rollback.
    */
   public void setRollbackOnly()
         throws IllegalStateException, SystemException
   {
      ThreadInfo ti = getThreadInfo();
      TransactionImpl current = ti.tx;

      if (current != null)
      {
         if (!current.isDone())
         {
            current.setRollbackOnly();

            if (trace)
               log.trace("tx marked for rollback only: " + current);
            return;
         }
         ti.tx = null;
      }
      throw new IllegalStateException("No transaction.");
   }

   /**
    *  Set the transaction timeout for new transactions started by the
    *  calling thread.
    */
   public void setTransactionTimeout(int seconds)
         throws SystemException
   {
      getThreadInfo().timeout = 1000 * seconds;

      if (trace)
         log.trace("tx timeout is now: " + seconds + "s");
   }

   /**
    *  Set the default transaction timeout for new transactions.
    *  This default value is used if <code>setTransactionTimeout()</code>
    *  was never called, or if it was called with a value of <code>0</code>.
    */
   public void setDefaultTransactionTimeout(int seconds)
   {
      timeOut = 1000L * seconds;

      if (trace)
         log.trace("default tx timeout is now: " + seconds + "s");
   }

   /**
    *  Get the default transaction timeout.
    *
    *  @return Default transaction timeout in seconds.
    */
   public int getDefaultTransactionTimeout()
   {
      return (int) (timeOut / 1000);
   }

   /**
    *  The following 2 methods are here to provide association and
    *  disassociation of the thread.
    */
   public Transaction disassociateThread()
   {
      return disassociateThread(getThreadInfo());
   }

   private Transaction disassociateThread(ThreadInfo ti) {
      TransactionImpl current = ti.tx;
      ti.tx=null;
      current.disassociateCurrentThread();
      return current;
   }   

   public void associateThread(Transaction transaction)
   {
      if (transaction != null && !(transaction instanceof TransactionImpl))
         throw new RuntimeException("Not a TransactionImpl, but a " +
               transaction.getClass().getName());

      // Associate with the thread
      TransactionImpl transactionImpl = (TransactionImpl) transaction;
      ThreadInfo ti = getThreadInfo();
      ti.tx = transactionImpl;
      transactionImpl.associateCurrentThread();
   }

   private void associateThread(ThreadInfo ti, TransactionImpl transaction)
   {
      // Associate with the thread
      ti.tx = transaction;
      transaction.associateCurrentThread();
   }

   // Implements TransactionPropagationContextImporter ---------------

   /**
    *  Import a transaction propagation context into this TM.
    *  The TPC is loosely typed, as we may (at a later time) want to
    *  import TPCs that come from other transaction domains without
    *  offloading the conversion to the client.
    *
    *  @param tpc The transaction propagation context that we want to
    *             import into this TM. Currently this is an instance
    *             of GlobalId. At some later time this may be an instance
    *             of a transaction propagation context from another
    *             transaction domain like
    *             org.omg.CosTransactions.PropagationContext.
    *
    *  @return A transaction representing this transaction propagation
    *          context, or null if this TPC cannot be imported.
    */
   public Transaction importTransactionPropagationContext(Object tpc)
   {
      if (tpc instanceof GlobalId)
      {
         GlobalId id = (GlobalId) tpc;
         return (Transaction) globalIdTx.get(id);
      }

      log.warn("Cannot import transaction propagation context: " + tpc);
      return null;
   }


   // Implements TransactionPropagationContextFactory ---------------

   /**
    *  Return a TPC for the current transaction.
    */
   public Object getTransactionPropagationContext()
   {
      return getTransactionPropagationContext(getThreadInfo().tx);
   }

   /**
    *  Return a TPC for the argument transaction.
    */
   public Object getTransactionPropagationContext(Transaction tx)
   {
      // If no transaction or unknown transaction class, return null.
      if (tx == null)
         return null;
      if (!(tx instanceof TransactionImpl))
      {
         log.warn("Cannot export transaction propagation context: " + tx);
         return null;
      }

      return ((TransactionImpl) tx).getGlobalId();
   }

   /**
    * Return the number of active transactions
    */
   public int getTransactionCount()
   {
      return globalIdTx.size();
   }
   /** A count of the transactions that have been committed */
   public long getCommitCount()
   {
      return commitCount;
   }
   /** A count of the transactions that have been rolled back */
   public long getRollbackCount()
   {
      return rollbackCount;
   }

   // Package protected ---------------------------------------------

   /**
    *  Release the given TransactionImpl.
    */
   void releaseTransactionImpl(TransactionImpl tx)
   {
      globalIdTx.remove(tx.getGlobalId());
   }

   /**
    * Increment the commit count
    */
   void incCommitCount()
   {
      ++commitCount;
   }

   /**
    * Increment the rollback count
    */
   void incRollbackCount()
   {
      ++rollbackCount;
   }

   // Protected -----------------------------------------------------

   // Private -------------------------------------------------------

   /**
    *  This keeps track of the thread association with transactions
    *  and timeout values.
    *  In some cases terminated transactions may not be cleared here.
    */
   private ThreadLocal threadTx = new ThreadLocal();

   /**
    *  This map contains the active transactions as values.
    *  The keys are the <code>GlobalId</code>s of the transactions.
    */
   private Map globalIdTx = Collections.synchronizedMap(new HashMap());


   /**
    *  Return the ThreadInfo for the calling thread, and create if not
    *  found.
    */
   private ThreadInfo getThreadInfo()
   {
      ThreadInfo ret = (ThreadInfo) threadTx.get();

      if (ret == null)
      {
         ret = new ThreadInfo();
         ret.timeout = timeOut;
         threadTx.set(ret);
      }

      return ret;
   }


   // Inner classes -------------------------------------------------

   /**
    *  A simple aggregate of a thread-associated timeout value
    *  and a thread-associated transaction.
    */
   static class ThreadInfo
   {
      long timeout;
      TransactionImpl tx;
   }
}