/*

  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.tomcat.dbcp.dbcp2.managed;

import java.lang.ref.WeakReference;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Objects;

import javax.transaction.RollbackException;
import javax.transaction.Status;
import javax.transaction.Synchronization;
import javax.transaction.SystemException;
import javax.transaction.Transaction;
import javax.transaction.TransactionSynchronizationRegistry;
import javax.transaction.xa.XAResource;

/**
 * TransactionContext represents the association between a single XAConnectionFactory and a Transaction. This context
 * contains a single shared connection which should be used by all ManagedConnections for the XAConnectionFactory, the
 * ability to listen for the transaction completion event, and a method to check the status of the transaction.
 *
 * @since 2.0
 */
public class TransactionContext {
    private final TransactionRegistry transactionRegistry;
    private final WeakReference<Transaction> transactionRef;
    private final TransactionSynchronizationRegistry transactionSynchronizationRegistry;
    private Connection sharedConnection;
    private boolean transactionComplete;

    /**
     * Creates a TransactionContext for the specified Transaction and TransactionRegistry. The TransactionRegistry is
     * used to obtain the XAResource for the shared connection when it is enlisted in the transaction.
     *
     * @param transactionRegistry
     *            the TransactionRegistry used to obtain the XAResource for the shared connection
     * @param transaction
     *            the transaction
     * @param transactionSynchronizationRegistry
     *              The optional TSR to register synchronizations with
     * @since 2.6.0
     */
    public TransactionContext(final TransactionRegistry transactionRegistry, final Transaction transaction,
                              final TransactionSynchronizationRegistry transactionSynchronizationRegistry) {
        Objects.requireNonNull(transactionRegistry, "transactionRegistry is null");
        Objects.requireNonNull(transaction, "transaction is null");
        this.transactionRegistry = transactionRegistry;
        this.transactionRef = new WeakReference<>(transaction);
        this.transactionComplete = false;
        this.transactionSynchronizationRegistry = transactionSynchronizationRegistry;
    }

    /**
     * Provided for backwards compatibility
     *
     * @param transactionRegistry the TransactionRegistry used to obtain the XAResource for the
     * shared connection
     * @param transaction the transaction
     */
    public TransactionContext(final TransactionRegistry transactionRegistry, final Transaction transaction) {
        this (transactionRegistry, transaction, null);
    }

    /**
     * Gets the connection shared by all ManagedConnections in the transaction. Specifically, connection using the same
     * XAConnectionFactory from which the TransactionRegistry was obtained.
     *
     * @return the shared connection for this transaction
     */
    public Connection getSharedConnection() {
        return sharedConnection;
    }

    /**
     * Sets the shared connection for this transaction. The shared connection is enlisted in the transaction.
     *
     * @param sharedConnection
     *            the shared connection
     * @throws SQLException
     *             if a shared connection is already set, if XAResource for the connection could not be found in the
     *             transaction registry, or if there was a problem enlisting the connection in the transaction
     */
    public void setSharedConnection(final Connection sharedConnection) throws SQLException {
        if (this.sharedConnection != null) {
            throw new IllegalStateException("A shared connection is already set");
        }

        // This is the first use of the connection in this transaction, so we must
        // enlist it in the transaction
        final Transaction transaction = getTransaction();
        try {
            final XAResource xaResource = transactionRegistry.getXAResource(sharedConnection);
            if (!transaction.enlistResource(xaResource)) {
                throw new SQLException("Unable to enlist connection in transaction: enlistResource returns 'false'.");
            }
        } catch (final IllegalStateException e) {
            // This can happen if the transaction is already timed out
            throw new SQLException("Unable to enlist connection in the transaction", e);
        } catch (final RollbackException e) {
            // transaction was rolled back... proceed as if there never was a transaction
        } catch (final SystemException e) {
            throw new SQLException("Unable to enlist connection the transaction", e);
        }

        this.sharedConnection = sharedConnection;
    }

    /**
     * Adds a listener for transaction completion events.
     *
     * @param listener
     *            the listener to add
     * @throws SQLException
     *             if a problem occurs adding the listener to the transaction
     */
    public void addTransactionContextListener(final TransactionContextListener listener) throws SQLException {
        try {
            if (!isActive()) {
                final Transaction transaction = this.transactionRef.get();
                listener.afterCompletion(TransactionContext.this,
                        transaction != null && transaction.getStatus() == Status.STATUS_COMMITTED);
                return;
            }
            final Synchronization s = new Synchronization() {
                @Override
                public void beforeCompletion() {
                    // empty
                }

                @Override
                public void afterCompletion(final int status) {
                    listener.afterCompletion(TransactionContext.this, status == Status.STATUS_COMMITTED);
                }
            };
            if (transactionSynchronizationRegistry != null) {
                transactionSynchronizationRegistry.registerInterposedSynchronization(s);
            } else {
                getTransaction().registerSynchronization(s);
            }
        } catch (final RollbackException e) {
            // JTA spec doesn't let us register with a transaction marked rollback only
            // just ignore this and the tx state will be cleared another way.
        } catch (final Exception e) {
            throw new SQLException("Unable to register transaction context listener", e);
        }
    }

    /**
     * True if the transaction is active or marked for rollback only.
     *
     * @return true if the transaction is active or marked for rollback only; false otherwise
     * @throws SQLException
     *             if a problem occurs obtaining the transaction status
     */
    public boolean isActive() throws SQLException {
        try {
            final Transaction transaction = this.transactionRef.get();
            if (transaction == null) {
                return false;
            }
            final int status = transaction.getStatus();
            return status == Status.STATUS_ACTIVE || status == Status.STATUS_MARKED_ROLLBACK;
        } catch (final SystemException e) {
            throw new SQLException("Unable to get transaction status", e);
        }
    }

    private Transaction getTransaction() throws SQLException {
        final Transaction transaction = this.transactionRef.get();
        if (transaction == null) {
            throw new SQLException("Unable to enlist connection because the transaction has been garbage collected");
        }
        return transaction;
    }

    /**
     * Sets the transaction complete flag to true.
     *
     * @since 2.4.0
     */
    public void completeTransaction() {
        this.transactionComplete = true;
    }

    /**
     * Gets the transaction complete flag to true.
     *
     * @return The transaction complete flag.
     *
     * @since 2.4.0
     */
    public boolean isTransactionComplete() {
        return this.transactionComplete;
    }
}
