/*
 * Copyright (C) 2011 eXo Platform SAS.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.exoplatform.services.database.utils;

import org.exoplatform.commons.utils.SecurityHelper;
import org.exoplatform.services.log.ExoLogger;
import org.exoplatform.services.log.Log;

import java.security.PrivilegedExceptionAction;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import javax.sql.DataSource;

/**
 * This class provides JDBC tools
 * 
 * @author <a href="mailto:nfilotto@exoplatform.com">Nicolas Filotto</a>
 * @version $Id$
 */
/**
 * @author <a href="abazko@exoplatform.com">Anatoliy Bazko</a>
 * @version $Id: JDBCUtils.java 34360 2009-07-22 23:58:59Z tolusha $
 *
 */
public class JDBCUtils
{
   private static final Log LOG = ExoLogger.getLogger("exo.core.component.database.JDBCUtils");

   /**
    * Default SQL delimiter.
    */
   public static final String SQL_DELIMITER = ";";

   /**
    * SQL delimiter comment prefix.
    */
   public static final String SQL_DELIMITER_COMMENT_PREFIX = "/*$DELIMITER:";

   public static final String SQL_DELIMITER_COMMENT_SUFFIX = "*/";

   private JDBCUtils()
   {
   }

   /**
    * Indicates whether or not a given table exists
    * 
    * @param tableName 
    *          the name of the table to check
    * @param con 
    *          the connection to use
    * @return <code>true</code> if it exists, <code>false</code> otherwise
    */
   public static boolean tableExists(String tableName, Connection con)
   {
      Statement stmt = null;
      ResultSet trs = null;
      try
      {
         String dialect = DialectDetecter.detect(con.getMetaData());
         String query;
         if (dialect.startsWith(DialectConstants.DB_DIALECT_MYSQL) || dialect.startsWith(DialectConstants.DB_DIALECT_PGSQL))
         {
            query = "SELECT count(*) from (SELECT 1 FROM " + tableName + " LIMIT 1) T";
         }
         else if (dialect.startsWith(DialectConstants.DB_DIALECT_ORACLE))
         {
            query = "SELECT count(*) from (SELECT 1 FROM " + tableName + " WHERE ROWNUM = 1) T";
         }
         else if (dialect.startsWith(DialectConstants.DB_DIALECT_DB2) || dialect.startsWith(DialectConstants.DB_DIALECT_DERBY)
            || dialect.startsWith(DialectConstants.DB_DIALECT_INGRES))
         {
            query = "SELECT count(*) from (SELECT 1 FROM " + tableName + " FETCH FIRST 1 ROWS ONLY) T";
         }
         else if (dialect.startsWith(DialectConstants.DB_DIALECT_MSSQL))
         {
            query = "SELECT count(*) from (SELECT TOP (1) 1 as C FROM " + tableName + ") T";
         }
         else if (dialect.startsWith(DialectConstants.DB_DIALECT_SYBASE))
         {
            query = "SELECT count(*) from (SELECT TOP 1 1 FROM " + tableName + ") T";
         }
         else
         {
            query = "SELECT count(*) FROM " + tableName;
         }
         stmt = con.createStatement();
         trs = stmt.executeQuery(query);
         return trs.next();
      }
      catch (SQLException e)
      {
         if (LOG.isDebugEnabled())
         {
            LOG.debug("SQLException occurs while checking the table " + tableName, e);
         }
         return false;
      }
      finally
      {
         freeResources(trs, stmt, null);
      }
   }

   /**
    * Retrieves the full message from SQLException. 
    * 
    * @param exception
    *          SQLException which will be parsed
    */
   public static String getFullMessage(SQLException exception)
   {
      StringBuilder errorTrace = new StringBuilder(exception.getMessage());

      SQLException next = exception;
      while (next != null)
      {
         errorTrace.append("; ");
         errorTrace.append(next.getMessage());

         next = next.getNextException();
      }

      Throwable cause = exception.getCause();

      return errorTrace + (cause != null ? " (Cause: " + cause.getMessage() + ")" : "");
   }

   /**
    * Replace whitespace characters with space character.
    */
   public static String cleanWhitespaces(String string)
   {
      if (string != null)
      {
         char[] cc = string.toCharArray();
         for (int ci = cc.length - 1; ci > 0; ci--)
         {
            if (Character.isWhitespace(cc[ci]))
            {
               cc[ci] = ' ';
            }
         }
         return new String(cc);
      }
      return string;
   }

   /**
    * Split string resource with SQL Delimiter. Delimiter can be taken from resource
    * at the begining of the first line. It surrounded with {@link #SQL_DELIMITER_COMMENT_PREFIX}
    * and {@link #SQL_DELIMITER_COMMENT_SUFFIX}. Otherwise the default delimiter will 
    * be used {@link #SQL_DELIMITER}.
    */
   public static String[] splitWithSQLDelimiter(String resource)
   {
      if (resource.startsWith(SQL_DELIMITER_COMMENT_PREFIX))
      {
         try
         {
            String scripts = resource.substring(SQL_DELIMITER_COMMENT_PREFIX.length());

            int endOfDelimIndex = scripts.indexOf(SQL_DELIMITER_COMMENT_SUFFIX);
            String delim = scripts.substring(0, endOfDelimIndex).trim();

            scripts = scripts.substring(endOfDelimIndex + 2).trim();
            return scripts.split(delim);
         }
         catch (IndexOutOfBoundsException e)
         {
            LOG.warn("Error of parse SQL-script file. Invalid DELIMITER configuration. Valid format is '"
               + SQL_DELIMITER_COMMENT_PREFIX + "XXX*/' at begin of the SQL-script file, where XXX - DELIMITER string."
               + " Spaces will be trimed. ", e);
            LOG.info("Using DELIMITER:[" + SQL_DELIMITER + "]");

            return resource.split(SQL_DELIMITER);
         }
      }
      else
      {
         return resource.split(SQL_DELIMITER);
      }
   }

   /**
    * Returns appropriate blob type field for specific database. 
    */
   public static String getAppropriateBlobType(DataSource dataSource) throws SQLException
   {
      String dialect = resolveDialect(dataSource);

      if (dialect.startsWith(DialectConstants.DB_DIALECT_HSQLDB))
      {
         return "VARBINARY(65535)";
      }
      else if (dialect.startsWith(DialectConstants.DB_DIALECT_MYSQL))
      {
         return "LONGBLOB";
      }
      else if (dialect.startsWith(DialectConstants.DB_DIALECT_PGSQL))
      {
         return "bytea";
      }
      else if (dialect.startsWith(DialectConstants.DB_DIALECT_MSSQL))
      {
         return "VARBINARY(MAX)";
      }
      else if (dialect.startsWith(DialectConstants.DB_DIALECT_SYBASE))
      {
         return "IMAGE";
      }
      else if (dialect.startsWith(DialectConstants.DB_DIALECT_INGRES))
      {
         return "long byte";
      }

      return "BLOB";
   }

   /**
    * Returns appropriate timestamp type field for specific database. 
    */
   public static String getAppropriateTimestamp(DataSource dataSource) throws SQLException
   {
      String dialect = resolveDialect(dataSource);

      if (dialect.startsWith(DialectConstants.DB_DIALECT_ORACLE))
      {
         return "NUMBER(19, 0)";
      }
      
      return "BIGINT";
   }

   /**
    * Returns appropriate char type field for specific database. 
    */
   public static String getAppropriateCharType(DataSource dataSource) throws SQLException
   {
      String dialect = resolveDialect(dataSource);

      if (dialect.startsWith(DialectConstants.DB_DIALECT_ORACLE))
      {
         // Oracle suggests the use VARCHAR2 instead of VARCHAR while declaring data type.
         return "VARCHAR2(512)";
      }

      return "VARCHAR(512)";
   }

   /**
    * Returns dialect one of dialect {@link DialectConstants} based on {@link DataSource} name.  
    */
   public static String resolveDialect(final DataSource dataSource) throws SQLException
   {
      Connection jdbcConn = SecurityHelper.doPrivilegedSQLExceptionAction(new PrivilegedExceptionAction<Connection>()
      {
         public Connection run() throws Exception
         {
            return dataSource.getConnection();
         }
      });

      try
      {
         return DialectDetecter.detect(jdbcConn.getMetaData());
      }
      finally
      {
         freeResources(null, null, jdbcConn);
      }
   }

   /**
    * Closes database related resources.
    */
   public static void freeResources(ResultSet resultSet, Statement statement, Connection conn)
   {
      if (resultSet != null)
      {
         try
         {
            resultSet.close();
         }
         catch (SQLException e)
         {
            LOG.error(e.getMessage(), e);
         }
      }

      if (statement != null)
      {
         try
         {
            statement.close();
         }
         catch (SQLException e)
         {
            LOG.error(e.getMessage(), e);
         }
      }

      if (conn != null)
      {
         try
         {
            conn.close();
         }
         catch (SQLException e)
         {
            LOG.error(e.getMessage(), e);
         }
      }
   }

}
