/*
  Copyright (c) 2010, 2018, Oracle and/or its affiliates. All rights reserved.

  The MySQL Connector/J is licensed under the terms of the GPLv2
  <http://www.gnu.org/licenses/old-licenses/gpl-2.0.html>, like most MySQL Connectors.
  There are special exceptions to the terms and conditions of the GPLv2 as it is applied to
  this software, see the FOSS License Exception
  <http://www.mysql.com/about/legal/licensing/foss-exception.html>.

  This program is free software; you can redistribute it and/or modify it under the terms
  of the GNU General Public License as published by the Free Software Foundation; version 2
  of the License.

  This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
  without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  See the GNU General Public License for more details.

  You should have received a copy of the GNU General Public License along with this
  program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth
  Floor, Boston, MA 02110-1301  USA

 */

package com.mysql.jdbc;

import java.sql.SQLException;
import java.util.Properties;

public class LoadBalancedAutoCommitInterceptor implements StatementInterceptorV2 {
    private int matchingAfterStatementCount = 0;
    private int matchingAfterStatementThreshold = 0;
    private String matchingAfterStatementRegex;
    private ConnectionImpl conn;
    private LoadBalancedConnectionProxy proxy = null;

    private boolean countStatements = false;

    public void destroy() {
        // do nothing here
    }

    /*
     * (non-Javadoc)
     * 
     * @see com.mysql.jdbc.StatementInterceptorV2#executeTopLevelOnly()
     */
    public boolean executeTopLevelOnly() {
        // always return false
        return false;
    }

    public void init(Connection connection, Properties props) throws SQLException {
        this.conn = (ConnectionImpl) connection;

        String autoCommitSwapThresholdAsString = props.getProperty("loadBalanceAutoCommitStatementThreshold", "0");
        try {
            this.matchingAfterStatementThreshold = Integer.parseInt(autoCommitSwapThresholdAsString);
        } catch (NumberFormatException nfe) {
            // nothing here, being handled in LoadBalancedConnectionProxy.
        }
        String autoCommitSwapRegex = props.getProperty("loadBalanceAutoCommitStatementRegex", "");
        if ("".equals(autoCommitSwapRegex)) {
            return;
        }
        this.matchingAfterStatementRegex = autoCommitSwapRegex;

    }

    /*
     * (non-Javadoc)
     * 
     * @see com.mysql.jdbc.StatementInterceptorV2#postProcess(java.lang.String, com.mysql.jdbc.Statement, com.mysql.jdbc.ResultSetInternalMethods,
     * com.mysql.jdbc.Connection, int, boolean, boolean, java.sql.SQLException)
     */
    public ResultSetInternalMethods postProcess(String sql, Statement interceptedStatement, ResultSetInternalMethods originalResultSet, Connection connection,
            int warningCount, boolean noIndexUsed, boolean noGoodIndexUsed, SQLException statementException) throws SQLException {

        // Don't count SETs neither SHOWs. Those are mostly used internally and must not trigger a connection switch.
        if (!this.countStatements || StringUtils.startsWithIgnoreCase(sql, "SET") || StringUtils.startsWithIgnoreCase(sql, "SHOW")) {
            return originalResultSet;
        }

        // Don't care if auto-commit is not enabled.
        if (!this.conn.getAutoCommit()) {
            this.matchingAfterStatementCount = 0;
            return originalResultSet;
        }

        if (this.proxy == null && this.conn.isProxySet()) {
            MySQLConnection lcl_proxy = this.conn.getMultiHostSafeProxy();
            while (lcl_proxy != null && !(lcl_proxy instanceof LoadBalancedMySQLConnection)) {
                lcl_proxy = lcl_proxy.getMultiHostSafeProxy();
            }
            if (lcl_proxy != null) {
                this.proxy = ((LoadBalancedMySQLConnection) lcl_proxy).getThisAsProxy();
            }

        }

        // Connection is not ready to rebalance yet.
        if (this.proxy == null) {
            return originalResultSet;
        }

        // Increment the match count if no regex specified, or if matches.
        if (this.matchingAfterStatementRegex == null || sql.matches(this.matchingAfterStatementRegex)) {
            this.matchingAfterStatementCount++;
        }

        // Trigger rebalance if count exceeds threshold.
        if (this.matchingAfterStatementCount >= this.matchingAfterStatementThreshold) {
            this.matchingAfterStatementCount = 0;
            try {
                this.proxy.pickNewConnection();
            } catch (SQLException e) {
                // eat this exception, the auto-commit statement completed, but we could not rebalance for some reason.  User may get exception when using
                // connection next.
            }
        }

        return originalResultSet;
    }

    public ResultSetInternalMethods preProcess(String sql, Statement interceptedStatement, Connection connection) throws SQLException {
        // we do nothing before execution, it's unsafe to swap servers at this point.
        return null;
    }

    void pauseCounters() {
        this.countStatements = false;
    }

    void resumeCounters() {
        this.countStatements = true;
    }
}