/**
    * Copyright 2005-2014 The Kuali Foundation
    *
    * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php
    *
   * 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.kuali.rice.krad.data.platform;
  
  import org.apache.commons.lang.StringUtils;
  import org.kuali.rice.core.api.config.property.ConfigContext;
  import org.springframework.beans.factory.InitializingBean;
  import org.springframework.dao.DataAccessException;
  import org.springframework.dao.DataAccessResourceFailureException;
  import org.springframework.dao.IncorrectResultSizeDataAccessException;
  import org.springframework.jdbc.core.ConnectionCallback;
  import org.springframework.jdbc.core.JdbcTemplate;
  import org.springframework.jdbc.support.JdbcUtils;
  import org.springframework.jdbc.support.incrementer.AbstractColumnMaxValueIncrementer;
  import org.springframework.jdbc.support.incrementer.AbstractSequenceMaxValueIncrementer;
  import org.springframework.jdbc.support.incrementer.DataFieldMaxValueIncrementer;
  import org.springframework.jdbc.support.incrementer.OracleSequenceMaxValueIncrementer;
  
  import javax.sql.DataSource;
  import java.sql.Connection;
  import java.sql.ResultSet;
  import java.sql.SQLException;
  import java.sql.Statement;
  import java.util.Collections;
  import java.util.IdentityHashMap;
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  
  /**
   * Factory for obtaining instances of {@link DataFieldMaxValueIncrementer} for a given {@link DataSource} and
   * incrementer name.
   *
   * <p>
   * These incrementers are used for getting generated incrementing values like that provided by a database-level sequence
   * generator.
   * </p>
   *
   * <p>
   * Note that not all database platforms support sequences natively, so incrementers can be returned that emulate
   * sequence-like behavior. The Spring Framework provides incrementer implementations for numerous different database
   * platforms. This classes uses {@link DatabasePlatforms} to determine the platform of the given {@link DataSource}.
   * </p>
   *
   * <p>
   * Note that this class will cache internally any incrementers for a given {@link DataSource} + Incrementer Name
   * combination.
   * </p>
   *
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  public final class MaxValueIncrementerFactory {
  
      private static final String ID_COLUMN_NAME = "ID";
  
      /**
       * Prefix for property names used to identify the classname for a {@link DataFieldMaxValueIncrementer} to use for a
       * given platform.
       *
       * <p>To construct a full property name, concatenate this prefix with the platform name.</p>
       *
       * @see org.kuali.rice.krad.data.platform.MaxValueIncrementerFactory
       */
      public static final String PLATFORM_INCREMENTER_PREFIX = "rice.krad.data.platform.incrementer.";
  
      private static final Map<DataSource, ConcurrentMap<String, DataFieldMaxValueIncrementer>> cache
              = Collections.synchronizedMap(new IdentityHashMap<DataSource, ConcurrentMap<String, DataFieldMaxValueIncrementer>>(8));
  
      /**
       * Either constructs a new incrementer or retrieves a cached instance for the given DataSource and target
       * incrementer name.
       *
       * @param dataSource the {@link DataSource} for which to retrieve the incrementer.
       * @param incrementerName the case-insensitive name of the incrementer to use, this will generally be the name of
       *        the database object which is used to implement the incrementer.
       * @return an incrementer that can be used to generate the next incremented value for the given incrementer against
       *         the specified {@link DataSource}.
       *
       * @throws IllegalArgumentException if dataSource or incrementerName are null or blank.
       */
      public static DataFieldMaxValueIncrementer getIncrementer(DataSource dataSource, String incrementerName) {
          if (dataSource == null) {
              throw new IllegalArgumentException("DataSource must not be null");
          }
          if (StringUtils.isBlank(incrementerName)) {
              throw new IllegalArgumentException("Incrementer name must not be null or blank");
         }
 
         // yes, we want to check if it's there first, then put if absent, for max speed! This is like ConcurrentMap's
         // version of double-checked locking.
         ConcurrentMap<String, DataFieldMaxValueIncrementer> incrementerCache = cache.get(dataSource);
 
         if (incrementerCache == null) {
             cache.put(dataSource,
                     new ConcurrentHashMap<String, DataFieldMaxValueIncrementer>(8, 0.9f, 1));
             if (incrementerCache == null) {
                 incrementerCache = cache.get(dataSource);
             }
         }
 
         // now check if we have a cached incrementer
         DataFieldMaxValueIncrementer incrementer = incrementerCache.get(incrementerName.toUpperCase());
         if (incrementer == null) {
             incrementer = incrementerCache.putIfAbsent(incrementerName.toUpperCase(), createIncrementer(dataSource,
                     incrementerName));
             if (incrementer == null) {
                 incrementer = incrementerCache.get(incrementerName.toUpperCase());
             }
         }
         return incrementer;
 
     }
 
     /**
      * Creates an {@link DataFieldMaxValueIncrementer} from a {@link DataSource}.
      *
      * @param dataSource the {@link DataSource} for which to retrieve the incrementer.
      * @param incrementerName the name of the incrementer.
      * @return an {@link DataFieldMaxValueIncrementer} from a {@link DataSource}.
      */
     private static DataFieldMaxValueIncrementer createIncrementer(DataSource dataSource, String incrementerName) {
         DatabasePlatformInfo platformInfo = DatabasePlatforms.detectPlatform(dataSource);
         DataFieldMaxValueIncrementer incrementer = getCustomizedIncrementer(platformInfo, dataSource,incrementerName,ID_COLUMN_NAME);
         if(incrementer != null){
             return incrementer;
         }
 
         if (DatabasePlatforms.ORACLE.equalsIgnoreCase(platformInfo.getName())) {
             incrementer = new OracleSequenceMaxValueIncrementer(dataSource, incrementerName);
         } else if (DatabasePlatforms.MYSQL.equalsIgnoreCase(platformInfo.getName())) {
             incrementer = new EnhancedMySQLMaxValueIncrementer(dataSource, incrementerName, ID_COLUMN_NAME);
         }
         if (incrementer == null) {
             throw new UnsupportedDatabasePlatformException(platformInfo);
         }
         if (incrementer instanceof InitializingBean) {
             try {
                 ((InitializingBean) incrementer).afterPropertiesSet();
             } catch (Exception e) {
                 throw new DataAccessResourceFailureException(
                         "Failed to initialize max value incrementer for given datasource and incrementer. dataSource="
                                 + dataSource.toString()
                                 + ", incrementerName = "
                                 + incrementerName, e);
             }
         }
         return incrementer;
     }
 
     /**
      * Checks the config file for any references to
      * {@code rice.krad.data.platform.incrementer.(DATASOURCE, ex mysql, oracle).(VERSION optional)}.
      *
      * <p>If matching one found attempts to instantiate it to return back to factory for use.</p>
      *
      * @param platformInfo the {@link DatabasePlatformInfo}.
      * @param dataSource the {@link DataSource} for which to retrieve the incrementer.
      * @param incrementerName the name of the incrementer.
      * @param columnName the name of the column to increment.
      * @return a config set customized incrementer that matches and can be used to generate the next incremented value
      *         for the given incrementer against the specified {@link DataSource}
      * @throws InstantiationError if cannot instantiate passed in class.
      */
     private static DataFieldMaxValueIncrementer getCustomizedIncrementer(DatabasePlatformInfo platformInfo, DataSource dataSource, String incrementerName, String columnName){
         if(platformInfo == null){
             throw new  IllegalArgumentException("DataSource platform must not be null");
         }
         if(ConfigContext.getCurrentContextConfig() == null){
             return null;
         }
         Map<String,String> incrementerPropToIncrementer = ConfigContext.getCurrentContextConfig().
                                 getPropertiesWithPrefix(PLATFORM_INCREMENTER_PREFIX, true);
         String platformNameVersion = platformInfo.getName().toLowerCase() + "." + platformInfo.getMajorVersion();
         String incrementerClassName = "";
 
          if(incrementerPropToIncrementer.containsKey(platformNameVersion)){
             incrementerClassName = incrementerPropToIncrementer.get(platformNameVersion);
          } else if(incrementerPropToIncrementer.containsKey(platformInfo.getName().toLowerCase())){
              incrementerClassName = incrementerPropToIncrementer.get(platformInfo.getName().toLowerCase());
          }
 
         if(StringUtils.isNotBlank(incrementerClassName)){
             try {
                 Class incrementerClass = Class.forName(incrementerClassName);
                 if(AbstractSequenceMaxValueIncrementer.class.isAssignableFrom(incrementerClass)){
                     AbstractSequenceMaxValueIncrementer abstractSequenceMaxValueIncrementer = (AbstractSequenceMaxValueIncrementer)incrementerClass.newInstance();
                     abstractSequenceMaxValueIncrementer.setDataSource(dataSource);
                     abstractSequenceMaxValueIncrementer.setIncrementerName(incrementerName);
                     return abstractSequenceMaxValueIncrementer;
 
                 } else if(AbstractColumnMaxValueIncrementer.class.isAssignableFrom(incrementerClass)){
                     AbstractColumnMaxValueIncrementer abstractColumnMaxValueIncrementer = (AbstractColumnMaxValueIncrementer)incrementerClass.newInstance();
                     abstractColumnMaxValueIncrementer.setDataSource(dataSource);
                     abstractColumnMaxValueIncrementer.setIncrementerName(incrementerName);
                     abstractColumnMaxValueIncrementer.setColumnName(columnName);
                     return abstractColumnMaxValueIncrementer;
                 } else {
                     throw new InstantiationError("Cannot create incrementer class "+incrementerClassName +" it has to extend "
                             + "AbstractSequenceMaxValueIncrementer or AbstractColumnMaxValueIncrementer");
                 }
             } catch (Exception e){
                 throw new InstantiationError("Could not instantiate custom incrementer "+incrementerClassName);
             }
         }
         return null;
     }
 
     /**
      * Defines an incrementer for MySQL.
      *
      * <p>
      * Since MySQL does not have any sense of a sequence, this class uses the concept of a sequence table, which is a
      * regular table that has an auto increment feature on it and is used only for that sequence.  When null values are
      * inserted into the table, the auto increment feature will insert the next value into that field, and then the
      * database will be queried for the last insert ID to get the next sequence value.
      * </p>
      */
     static final class EnhancedMySQLMaxValueIncrementer extends AbstractColumnMaxValueIncrementer {
 
         private JdbcTemplate template;
 
         /**
          * Creates an incrementer for MySQL.
          */
         private EnhancedMySQLMaxValueIncrementer() {}
 
         /**
          * Creates an incrementer for MySQL.
          *
          * @param dataSource the {@link DataSource} for which to retrieve the incrementer.
          * @param incrementerName the name of the incrementer.
          * @param columnName the name of the column to increment.
          */
         private EnhancedMySQLMaxValueIncrementer(DataSource dataSource, String incrementerName, String columnName) {
             super(dataSource, incrementerName, columnName);
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public synchronized void afterPropertiesSet() {
             super.afterPropertiesSet();
             template = new JdbcTemplate(getDataSource());
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         protected synchronized long getNextKey() throws DataAccessException {
             return template.execute(new ConnectionCallback<Long>() {
                 @Override
                 public Long doInConnection(Connection con) throws SQLException, DataAccessException {
                     Statement statement = null;
                     ResultSet resultSet = null;
                     try {
                         statement = con.createStatement();
                         String sql = "INSERT INTO " + getIncrementerName() + " VALUES (NULL)";
                         statement.executeUpdate(sql);
                         sql = "SELECT LAST_INSERT_ID()";
                         resultSet = statement.executeQuery(sql);
                         if (resultSet != null) {
                             resultSet.first();
                             return resultSet.getLong(1);
                         } else {
                             throw new IncorrectResultSizeDataAccessException("Failed to get last_insert_id() for sequence incrementer table '" + getIncrementerName() + "'", 1);
                         }
                     } finally {
                         JdbcUtils.closeResultSet(resultSet);
                         JdbcUtils.closeStatement(statement);
                     }
                 }
             }).longValue();
         }
     }
 
     /**
      * No-op constructor for final class.
      */
     private MaxValueIncrementerFactory() {}
 
 }