/*
 * 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.taglibs.standard.tag.common.sql;

import java.sql.Connection;
import java.sql.SQLException;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspTagException;
import javax.servlet.jsp.tagext.TagSupport;
import javax.servlet.jsp.tagext.TryCatchFinally;
import javax.sql.DataSource;

import org.apache.taglibs.standard.resources.Resources;


/**
 * <p>Tag handler for &lt;Transaction&gt; in JSTL.
 *
 * @author Hans Bergsten
 */

public abstract class TransactionTagSupport extends TagSupport
        implements TryCatchFinally {

    //*********************************************************************
    // Private constants

    private static final String TRANSACTION_READ_COMMITTED
            = "read_committed";
    private static final String TRANSACTION_READ_UNCOMMITTED
            = "read_uncommitted";
    private static final String TRANSACTION_REPEATABLE_READ
            = "repeatable_read";
    private static final String TRANSACTION_SERIALIZABLE
            = "serializable";


    //*********************************************************************
    // Protected state

    protected Object rawDataSource;
    protected boolean dataSourceSpecified;


    //*********************************************************************
    // Private state

    private Connection conn;
    private int isolation;
    private int origIsolation;


    //*********************************************************************
    // Constructor and initialization

    public TransactionTagSupport() {
        super();
        conn = null;
        dataSourceSpecified = false;
        rawDataSource = null;
        isolation = Connection.TRANSACTION_NONE;
    }


    //*********************************************************************
    // Tag logic

    /**
     * Prepares for execution by setting the initial state, such as
     * getting the <code>Connection</code> and preparing it for
     * the transaction.
     */
    @Override
    public int doStartTag() throws JspException {

        if ((rawDataSource == null) && dataSourceSpecified) {
            throw new JspException(
                    Resources.getMessage("SQL_DATASOURCE_NULL"));
        }

        DataSource dataSource = DataSourceUtil.getDataSource(rawDataSource,
                pageContext);

        try {
            conn = dataSource.getConnection();
            origIsolation = conn.getTransactionIsolation();
            if (origIsolation == Connection.TRANSACTION_NONE) {
                throw new JspTagException(
                        Resources.getMessage("TRANSACTION_NO_SUPPORT"));
            }
            if ((isolation != Connection.TRANSACTION_NONE)
                    && (isolation != origIsolation)) {
                conn.setTransactionIsolation(isolation);
            }
            conn.setAutoCommit(false);
        } catch (SQLException e) {
            throw new JspTagException(
                    Resources.getMessage("ERROR_GET_CONNECTION",
                            e.toString()), e);
        }

        return EVAL_BODY_INCLUDE;
    }

    /**
     * Commits the transaction.
     */
    @Override
    public int doEndTag() throws JspException {
        try {
            conn.commit();
        } catch (SQLException e) {
            throw new JspTagException(
                    Resources.getMessage("TRANSACTION_COMMIT_ERROR",
                            e.toString()), e);
        }
        return EVAL_PAGE;
    }

    /**
     * Rollbacks the transaction and rethrows the Throwable.
     */
    public void doCatch(Throwable t) throws Throwable {
        if (conn != null) {
            try {
                conn.rollback();
            } catch (SQLException e) {
                // Ignore to not hide orignal exception
            }
        }
        throw t;
    }

    /**
     * Restores the <code>Connection</code> to its initial state and
     * closes it.
     */
    public void doFinally() {
        if (conn != null) {
            try {
                if ((isolation != Connection.TRANSACTION_NONE)
                        && (isolation != origIsolation)) {
                    conn.setTransactionIsolation(origIsolation);
                }
                conn.setAutoCommit(true);
                conn.close();
            } catch (SQLException e) {
                // Not much we can do
            }
        }
        conn = null;
        isolation = Connection.TRANSACTION_NONE;
    }

    // Releases any resources we may have (or inherit)

    @Override
    public void release() {
        dataSourceSpecified = false;
        rawDataSource = null;
    }


    //*********************************************************************
    // Public utility methods

    /**
     * Setter method for the transaction isolation level.
     */
    public void setIsolation(String iso) throws JspTagException {

        if (TRANSACTION_READ_COMMITTED.equals(iso)) {
            isolation = Connection.TRANSACTION_READ_COMMITTED;
        } else if (TRANSACTION_READ_UNCOMMITTED.equals(iso)) {
            isolation = Connection.TRANSACTION_READ_UNCOMMITTED;
        } else if (TRANSACTION_REPEATABLE_READ.equals(iso)) {
            isolation = Connection.TRANSACTION_REPEATABLE_READ;
        } else if (TRANSACTION_SERIALIZABLE.equals(iso)) {
            isolation = Connection.TRANSACTION_SERIALIZABLE;
        } else {
            throw new JspTagException(
                    Resources.getMessage("TRANSACTION_INVALID_ISOLATION"));
        }
    }

    /**
     * Called by nested parameter elements to get a reference to
     * the Connection.
     */
    public Connection getSharedConnection() {
        return conn;
    }
}
