/*
 * ModeShape (http://www.modeshape.org)
 *
 * Licensed 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.modeshape.jcr.txn;

import java.util.concurrent.atomic.AtomicInteger;
import javax.transaction.HeuristicMixedException;
import javax.transaction.HeuristicRollbackException;
import javax.transaction.NotSupportedException;
import javax.transaction.RollbackException;
import javax.transaction.SystemException;
import javax.transaction.TransactionManager;
import org.modeshape.jcr.cache.SessionCache;

/**
 * An implementation of {@link Transactions} that does not even check whether there is a current transaction and instead always
 * attempts to create a transaction within the {@link SessionCache#save()} calls. This is more efficient when the repository can
 * be set up to never use container-managed or user-managed transactions.
 */
public final class NoClientTransactions extends Transactions {

    /**
     * During ws cache initialization (either when the repo starts up of a new ws is created), there can be a case of semantically
     * nested simple transactions, so we need effective make sure that only 1 instance of an active transaction can exist at any
     * given time. We cannot use multiple instance because completion functions are instance-dependent
     */
    protected static final ThreadLocal<NoClientTransaction> ACTIVE_TRANSACTION = new ThreadLocal<NoClientTransaction>();

    /**
     * Creates a new instance passing in the given monitor factory and transaction manager
     * 
     * @param txnMgr a {@link TransactionManager} instance; never null
     */
    public NoClientTransactions( TransactionManager txnMgr ) {
        super(txnMgr);
    }

    @Override
    public synchronized Transaction begin() throws NotSupportedException, SystemException {
        if (ACTIVE_TRANSACTION.get() == null) {
            // Start a transaction ...
            txnMgr.begin();
            if (logger.isTraceEnabled()) {
                logger.trace("Begin transaction {0}", currentTransactionId());
            }
            ACTIVE_TRANSACTION.set(new NoClientTransaction(txnMgr));
        }
        return ACTIVE_TRANSACTION.get().transactionBegin();
    }

    protected class NoClientTransaction extends TraceableSimpleTransaction {
        private final AtomicInteger nestedLevel = new AtomicInteger(0);

        public NoClientTransaction( TransactionManager txnMgr ) {
            super(txnMgr);
        }

        @Override
        public void commit()
            throws RollbackException, HeuristicMixedException, HeuristicRollbackException, SecurityException,
            IllegalStateException, SystemException {
            if (nestedLevel.getAndDecrement() == 1) {
                NoClientTransactions.ACTIVE_TRANSACTION.remove();
                super.commit();
            } else {
                logger.trace("Not committing transaction because it's nested within another transaction. Only the top level transaction should commit");
            }
        }

        @Override
        public void rollback() throws IllegalStateException, SecurityException, SystemException {
            NoClientTransactions.ACTIVE_TRANSACTION.remove();
            super.rollback();
        }

        protected NoClientTransaction transactionBegin() {
            nestedLevel.incrementAndGet();
            return this;
        }
    }
}
