/*

  * 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.commons.transaction.memory;

 import java.util.Collection;

 import java.util.Map;

 import java.util.Set;

 import org.apache.commons.transaction.locking.ReadWriteLockManager;

 import org.apache.commons.transaction.util.LoggerFacade;

 /**

  * Wrapper that adds transactional control to all kinds of maps that implement the {@link Map} interface. By using

  * pessimistic transaction control (blocking locks) this wrapper has better isolation than {@link TransactionalMapWrapper}, but

  * also has less possible concurrency and may even deadlock. A commit, however, will never fail.

  * <br>

  * Start a transaction by calling {@link #startTransaction()}. Then perform the normal actions on the map and

  * finally either call {@link #commitTransaction()} to make your changes permanent or {@link #rollbackTransaction()} to

  * undo them.

  * <br>

  * <em>Caution:</em> Do not modify values retrieved by {@link #get(Object)} as this will circumvent the transactional mechanism.

  * Rather clone the value or copy it in a way you see fit and store it back using {@link #put(Object, Object)}.

  * <br>

  * <em>Note:</em> This wrapper guarantees isolation level <code>SERIALIZABLE</code>.

  * 

  * @version $Id: PessimisticMapWrapper.java 493628 2007-01-07 01:42:48Z joerg $

  * @see TransactionalMapWrapper

  * @see OptimisticMapWrapper

  */

 public class PessimisticMapWrapper extends TransactionalMapWrapper {

     protected static final int READ = 1;

     protected static final int WRITE = 2;

     protected static final Object GLOBAL_LOCK = "GLOBAL";

     protected ReadWriteLockManager lockManager;

 //    protected MultiLevelLock globalLock;

     protected long readTimeOut = 60000; /* FIXME: pass in ctor */

     /**

      * Creates a new pessimistic transactional map wrapper. Temporary maps and sets to store transactional

      * data will be instances of {@link java.util.HashMap} and {@link java.util.HashSet}. 

      * 

      * @param wrapped map to be wrapped

      * @param logger

      *            generic logger used for all kinds of logging

      */

     public PessimisticMapWrapper(Map wrapped, LoggerFacade logger) {

         this(wrapped, new HashMapFactory(), new HashSetFactory(), logger);

     }

     /**

      * Creates a new pessimistic transactional map wrapper. Temporary maps and sets to store transactional

      * data will be created and disposed using {@link MapFactory} and {@link SetFactory}.

      * 

      * @param wrapped map to be wrapped

      * @param mapFactory factory for temporary maps

      * @param setFactory factory for temporary sets

      * @param logger

      *            generic logger used for all kinds of logging

      */

     public PessimisticMapWrapper(Map wrapped, MapFactory mapFactory, SetFactory setFactory, LoggerFacade logger) {

         super(wrapped, mapFactory, setFactory);

         lockManager = new ReadWriteLockManager(logger, readTimeOut);

 //        globalLock = new GenericLock(GLOBAL_LOCK_NAME, WRITE, logger);

     }

     public void startTransaction() {

         if (getActiveTx() != null) {

             throw new IllegalStateException(

                 "Active thread " + Thread.currentThread() + " already associated with a transaction!");

         }

         LockingTxContext context = new LockingTxContext();

         setActiveTx(context);

     }

     public Collection values() {

         assureGlobalReadLock();

         return super.values();

     }

     public Set entrySet() {

         assureGlobalReadLock();

         return super.entrySet();

     }

     public Set keySet() {

         assureGlobalReadLock();

         return super.keySet();

     }

     public Object remove(Object key) {

         // assure we get a write lock before super can get a read lock to avoid lots

         // of deadlocks

         assureWriteLock(key);

         return super.remove(key);

     }

     public Object put(Object key, Object value) {

         // assure we get a write lock before super can get a read lock to avoid lots

         // of deadlocks

         assureWriteLock(key);

         return super.put(key, value);

     }

     protected void assureWriteLock(Object key) {

         LockingTxContext txContext = (LockingTxContext) getActiveTx();

         if (txContext != null) {

             lockManager.writeLock(txContext, key);

             // XXX fake intention lock (prohibits global WRITE)

             lockManager.readLock(txContext, GLOBAL_LOCK); 

         }

     }

     protected void assureGlobalReadLock() {

         LockingTxContext txContext = (LockingTxContext) getActiveTx();

         if (txContext != null) {

             // XXX fake intention lock (prohibits global WRITE)

             lockManager.readLock(txContext, GLOBAL_LOCK); 

         }

     }

     public class LockingTxContext extends TxContext {

         protected Set keys() {

             lockManager.readLock(this, GLOBAL_LOCK); 

             return super.keys();

         }

         protected Object get(Object key) {

             lockManager.readLock(this, key);

             // XXX fake intention lock (prohibits global WRITE)

             lockManager.readLock(this, GLOBAL_LOCK);

             return super.get(key);

         }

         protected void put(Object key, Object value) {

             lockManager.writeLock(this, key);

             // XXX fake intention lock (prohibits global WRITE)

             lockManager.readLock(this, GLOBAL_LOCK);

             super.put(key, value);

         }

         protected void remove(Object key) {

             lockManager.writeLock(this, key);

             // XXX fake intention lock (prohibits global WRITE)

             lockManager.readLock(this, GLOBAL_LOCK);

             super.remove(key);

         }

         protected int size() {

             // XXX this is bad luck, we need a global read lock just for the size :( :( :(

             lockManager.readLock(this, GLOBAL_LOCK);

             return super.size();

         }

         protected void clear() {

             lockManager.writeLock(this, GLOBAL_LOCK);

             super.clear();

         }

         protected void dispose() {

             super.dispose();

             lockManager.releaseAll(this);

         }

         protected void finalize() throws Throwable {

             dispose();

             super.finalize();

         }

     }

 }