/*
------------------------------------
JavaOnTracks          Thibaut Colar
tcolar-jot AT colar DOT net
Artistic Licence 2.0
http://www.javaontracks.net
------------------------------------
 */
package net.jot.persistance;

import net.jot.db.JOTDBField;
import net.jot.logger.JOTLogger;
import net.jot.persistance.query.JOTQueryInterface;
import net.jot.persistance.query.JOTQueryManager;

/**
 * Extend this class to create your own DBUpdater.
 * If you have an existing JOTDB (Using JOTMOdel's) and you need to change some model/tables
 * definition (ie: add fields, rename columns etc ...) you should create a DBUpdater from it and imp,ement upgradeDb()
 * You must define your implementaion in db.properties:
 * Ex:  db.upgrader.class = com.mycomp.mydb.MyUpgrader
 * Then in the upgradeDb() you can handle the upgrade,
 * @author thibautc
 */
public abstract class JOTDBUpgrader {
 // Field type alterations constants.
  public static final int ALTER_TYPE_TINYINT_TO_SMALLINT = 1;
  public static final int ALTER_TYPE_SMALLINT_TO_INT = 2;
  public static final int ALTER_TYPE_INT_TO_BIGINT = 3;
  public static final int ALTER_TYPE_BIGINT_TO_DECIMAL = 4;
  public static final int ALTER_TYPE_INT_TO_FLOATL = 5;
  public static final int ALTER_TYPE_INT_TO_DOUBLE = 6;
  public static final int ALTER_TYPE_DATE_TO_TIMESTAMP = 7;
  public static final int ALTER_TYPE_TIMESTAMP_TO_DATE = 8;
  // Provide "down" alterations ? (ie: BIGINT to TINYINT etc...), not much use and dangerous.

  protected JOTDBUpgrader()
  {
  }

  /**
   * Implement this method to handle a db upgrade.
   * 
   * You can use the other methods provided here to upgrade your tables(ie: addTableColumn etc...)
   * 
   * Make sure to bump the version after each version upgrade : setVersion(x);
   * Note: if the DB is brand new, the version passed will be "1".
   * 
   * @param:version  current Version Of the Db (on file)
   */
  public abstract void upgradeDb(int version) throws Exception;

  /**
   *  return the DBModel Version(code). a.k.a the version we should be at after the upgrade.
   */
  public abstract int getLatestVersion();
  
  /**
         * Add a new Field to a table
         * The field must exists in the table model (JOTModel).
         * @throws java.lang.Exception
         */
  public void addTableColumn(Class modelClass, String fieldName, Object defaultValue) throws Exception
  {
    // skip validation since it would fail anyhow.
    JOTModelMapping mapping=JOTQueryManager.getMapping(modelClass,false,true);
    JOTDBField field=(JOTDBField)mapping.getMappedFields().get(fieldName);
    if(field==null)
      field=(JOTDBField)mapping.getFields().get(fieldName);
    if(field==null)
    {
      throw new Exception("The field named :"+fieldName+" does not exists in the JOTModel: "+mapping.getTableName());
    }
    JOTLogger.log(JOTLogger.CAT_DB, JOTLogger.INFO_LEVEL, this, "Adding column:"+field.getFieldName()+" to Table: " + mapping.getTableName());
    JOTQueryInterface impl=JOTQueryManager.getImplementation(mapping.getQueryClassName());
    impl.alterAddField(mapping, field, defaultValue);
    // if we get here , it went ok, updating the table metadata
    JOTModelMapping.writeMetaFile(mapping);
  }

  /**
         * Removed a field from a table
         * THAT FIELD DATA WILL BE LOST.
         * @throws java.lang.Exception
         */
  /*public void removTableColumn(String tableName, String fieldName) throws Exception
  {
    //TODO
  }*/

  
  /*public void renameTable(String oldName, String newName) throws Exception
  {
    impl.renameTable(oldName, newName);
  }
  */
  /*public void alterFieldName(String oldName, String newName) throws Exception
  {
    impl.alterRenameField(JOTModel model, oldName, newName);
  }*/
  
  /*public void alterFieldType(String fieldName, int alterType) throws Exception
  {
    impl.alterFieldType(JOTModel model, fieldName, alterType);
  }*/

  /*public void alterVarcharLength(String fieldName, int newLength) throws Exception
  {
    impl.alterVarcharLength(JOTModel model, fieldName, newLength);
  }*/
  

}