<?php
/**
 * CDbMigration class file.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @link http://www.yiiframework.com/
 * @copyright Copyright &copy; 2008-2011 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */

/**
 * CDbMigration is the base class for representing a database migration.
 *
 * CDbMigration is designed to be used together with the "yiic migrate" command.
 *
 * Each child class of CDbMigration represents an individual database migration which
 * is identified by the child class name.
 *
 * Within each migration, the {@link up} method contains the logic for "upgrading"
 * the database used in an application; while the {@link down} method contains "downgrading"
 * logic. The "yiic migrate" command manages all available migrations in an application.
 *
 * CDbMigration provides a set of convenient methods for manipulating database data and schema.
 * For example, the {@link insert} method can be used to easily insert a row of data into
 * a database table; the {@link createTable} method can be used to create a database table.
 * Compared with the same methods in {@link CDbCommand}, these methods will display extra
 * information showing the method parameters and execution time, which may be useful when
 * applying migrations.
 *
 * @property CDbConnection $dbConnection The currently active database connection.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @version $Id$
 * @package system.db
 * @since 1.1.6
 */
abstract class CDbMigration extends CComponent
{
	private $_db;

	/**
	 * This method contains the logic to be executed when applying this migration.
	 * Child classes may implement this method to provide actual migration logic.
	 * @return boolean
	 */
	public function up()
	{
		$transaction=$this->getDbConnection()->beginTransaction();
		try
		{
			if($this->safeUp()===false)
			{
				$transaction->rollback();
				return false;
			}
			$transaction->commit();
		}
		catch(Exception $e)
		{
			echo "Exception: ".$e->getMessage().' ('.$e->getFile().':'.$e->getLine().")\n";
			echo $e->getTraceAsString()."\n";
			$transaction->rollback();
			return false;
		}
	}

	/**
	 * This method contains the logic to be executed when removing this migration.
	 * The default implementation throws an exception indicating the migration cannot be removed.
	 * Child classes may override this method if the corresponding migrations can be removed.
	 * @return boolean
	 */
	public function down()
	{
		$transaction=$this->getDbConnection()->beginTransaction();
		try
		{
			if($this->safeDown()===false)
			{
				$transaction->rollback();
				return false;
			}
			$transaction->commit();
		}
		catch(Exception $e)
		{
			echo "Exception: ".$e->getMessage().' ('.$e->getFile().':'.$e->getLine().")\n";
			echo $e->getTraceAsString()."\n";
			$transaction->rollback();
			return false;
		}
	}

	/**
	 * This method contains the logic to be executed when applying this migration.
	 * This method differs from {@link up} in that the DB logic implemented here will
	 * be enclosed within a DB transaction.
	 * Child classes may implement this method instead of {@link up} if the DB logic
	 * needs to be within a transaction.
	 * @return boolean
	 * @since 1.1.7
	 */
	public function safeUp()
	{
	}

	/**
	 * This method contains the logic to be executed when removing this migration.
	 * This method differs from {@link down} in that the DB logic implemented here will
	 * be enclosed within a DB transaction.
	 * Child classes may implement this method instead of {@link up} if the DB logic
	 * needs to be within a transaction.
	 * @return boolean
	 * @since 1.1.7
	 */
	public function safeDown()
	{
	}

	/**
	 * Returns the currently active database connection.
	 * By default, the 'db' application component will be returned and activated.
	 * You can call {@link setDbConnection} to switch to a different database connection.
	 * Methods such as {@link insert}, {@link createTable} will use this database connection
	 * to perform DB queries.
	 * @return CDbConnection the currently active database connection
	 */
	public function getDbConnection()
	{
		if($this->_db===null)
		{
			$this->_db=Yii::app()->getComponent('db');
			if(!$this->_db instanceof CDbConnection)
				throw new CException(Yii::t('yii', 'The "db" application component must be configured to be a CDbConnection object.'));
		}
		return $this->_db;
	}

	/**
	 * Sets the currently active database connection.
	 * The database connection will be used by the methods such as {@link insert}, {@link createTable}.
	 * @param CDbConnection $db the database connection component
	 */
	public function setDbConnection($db)
	{
		$this->_db=$db;
	}

	/**
	 * Executes a SQL statement.
	 * This method executes the specified SQL statement using {@link dbConnection}.
	 * @param string $sql the SQL statement to be executed
	 * @param array $params input parameters (name=>value) for the SQL execution. See {@link CDbCommand::execute} for more details.
	 * @since 1.1.7
	 */
	public function execute($sql, $params=array())
	{
		echo "    > execute SQL: $sql ...";
		$time=microtime(true);
		$this->getDbConnection()->createCommand($sql)->execute($params);
		echo " done (time: ".sprintf('%.3f', microtime(true)-$time)."s)\n";
	}

	/**
	 * Creates and executes an INSERT SQL statement.
	 * The method will properly escape the column names, and bind the values to be inserted.
	 * @param string $table the table that new rows will be inserted into.
	 * @param array $columns the column data (name=>value) to be inserted into the table.
	 */
	public function insert($table, $columns)
	{
		echo "    > insert into $table ...";
		$time=microtime(true);
		$this->getDbConnection()->createCommand()->insert($table, $columns);
		echo " done (time: ".sprintf('%.3f', microtime(true)-$time)."s)\n";
	}

	/**
	 * Creates and executes an UPDATE SQL statement.
	 * The method will properly escape the column names and bind the values to be updated.
	 * @param string $table the table to be updated.
	 * @param array $columns the column data (name=>value) to be updated.
	 * @param mixed $conditions the conditions that will be put in the WHERE part. Please
	 * refer to {@link CDbCommand::where} on how to specify conditions.
	 * @param array $params the parameters to be bound to the query.
	 */
	public function update($table, $columns, $conditions='', $params=array())
	{
		echo "    > update $table ...";
		$time=microtime(true);
		$this->getDbConnection()->createCommand()->update($table, $columns, $conditions, $params);
		echo " done (time: ".sprintf('%.3f', microtime(true)-$time)."s)\n";
	}

	/**
	 * Creates and executes a DELETE SQL statement.
	 * @param string $table the table where the data will be deleted from.
	 * @param mixed $conditions the conditions that will be put in the WHERE part. Please
	 * refer to {@link CDbCommand::where} on how to specify conditions.
	 * @param array $params the parameters to be bound to the query.
	 */
	public function delete($table, $conditions='', $params=array())
	{
		echo "    > delete from $table ...";
		$time=microtime(true);
		$this->getDbConnection()->createCommand()->delete($table, $conditions, $params);
		echo " done (time: ".sprintf('%.3f', microtime(true)-$time)."s)\n";
	}

	/**
	 * Builds and executes a SQL statement for creating a new DB table.
	 *
	 * The columns in the new  table should be specified as name-definition pairs (e.g. 'name'=>'string'),
	 * where name stands for a column name which will be properly quoted by the method, and definition
	 * stands for the column type which can contain an abstract DB type.
	 * The {@link getColumnType} method will be invoked to convert any abstract type into a physical one.
	 *
	 * If a column is specified with definition only (e.g. 'PRIMARY KEY (name, type)'), it will be directly
	 * inserted into the generated SQL.
	 *
	 * @param string $table the name of the table to be created. The name will be properly quoted by the method.
	 * @param array $columns the columns (name=>definition) in the new table.
	 * @param string $options additional SQL fragment that will be appended to the generated SQL.
	 */
	public function createTable($table, $columns, $options=null)
	{
		echo "    > create table $table ...";
		$time=microtime(true);
		$this->getDbConnection()->createCommand()->createTable($table, $columns, $options);
		echo " done (time: ".sprintf('%.3f', microtime(true)-$time)."s)\n";
	}

	/**
	 * Builds and executes a SQL statement for renaming a DB table.
	 * @param string $table the table to be renamed. The name will be properly quoted by the method.
	 * @param string $newName the new table name. The name will be properly quoted by the method.
	 */
	public function renameTable($table, $newName)
	{
		echo "    > rename table $table to $newName ...";
		$time=microtime(true);
		$this->getDbConnection()->createCommand()->renameTable($table, $newName);
		echo " done (time: ".sprintf('%.3f', microtime(true)-$time)."s)\n";
	}

	/**
	 * Builds and executes a SQL statement for dropping a DB table.
	 * @param string $table the table to be dropped. The name will be properly quoted by the method.
	 */
	public function dropTable($table)
	{
		echo "    > drop table $table ...";
		$time=microtime(true);
		$this->getDbConnection()->createCommand()->dropTable($table);
		echo " done (time: ".sprintf('%.3f', microtime(true)-$time)."s)\n";
	}

	/**
	 * Builds and executes a SQL statement for truncating a DB table.
	 * @param string $table the table to be truncated. The name will be properly quoted by the method.
	 */
	public function truncateTable($table)
	{
		echo "    > truncate table $table ...";
		$time=microtime(true);
		$this->getDbConnection()->createCommand()->truncateTable($table);
		echo " done (time: ".sprintf('%.3f', microtime(true)-$time)."s)\n";
	}

	/**
	 * Builds and executes a SQL statement for adding a new DB column.
	 * @param string $table the table that the new column will be added to. The table name will be properly quoted by the method.
	 * @param string $column the name of the new column. The name will be properly quoted by the method.
	 * @param string $type the column type. The {@link getColumnType} method will be invoked to convert abstract column type (if any)
	 * into the physical one. Anything that is not recognized as abstract type will be kept in the generated SQL.
	 * For example, 'string' will be turned into 'varchar(255)', while 'string not null' will become 'varchar(255) not null'.
	 */
	public function addColumn($table, $column, $type)
	{
		echo "    > add column $column $type to table $table ...";
		$time=microtime(true);
		$this->getDbConnection()->createCommand()->addColumn($table, $column, $type);
		echo " done (time: ".sprintf('%.3f', microtime(true)-$time)."s)\n";
	}

	/**
	 * Builds and executes a SQL statement for dropping a DB column.
	 * @param string $table the table whose column is to be dropped. The name will be properly quoted by the method.
	 * @param string $column the name of the column to be dropped. The name will be properly quoted by the method.
	 */
	public function dropColumn($table, $column)
	{
		echo "    > drop column $column from table $table ...";
		$time=microtime(true);
		$this->getDbConnection()->createCommand()->dropColumn($table, $column);
		echo " done (time: ".sprintf('%.3f', microtime(true)-$time)."s)\n";
	}

	/**
	 * Builds and executes a SQL statement for renaming a column.
	 * @param string $table the table whose column is to be renamed. The name will be properly quoted by the method.
	 * @param string $name the old name of the column. The name will be properly quoted by the method.
	 * @param string $newName the new name of the column. The name will be properly quoted by the method.
	 */
	public function renameColumn($table, $name, $newName)
	{
		echo "    > rename column $name in table $table to $newName ...";
		$time=microtime(true);
		$this->getDbConnection()->createCommand()->renameColumn($table, $name, $newName);
		echo " done (time: ".sprintf('%.3f', microtime(true)-$time)."s)\n";
	}

	/**
	 * Builds and executes a SQL statement for changing the definition of a column.
	 * @param string $table the table whose column is to be changed. The table name will be properly quoted by the method.
	 * @param string $column the name of the column to be changed. The name will be properly quoted by the method.
	 * @param string $type the new column type. The {@link getColumnType} method will be invoked to convert abstract column type (if any)
	 * into the physical one. Anything that is not recognized as abstract type will be kept in the generated SQL.
	 * For example, 'string' will be turned into 'varchar(255)', while 'string not null' will become 'varchar(255) not null'.
	 */
	public function alterColumn($table, $column, $type)
	{
		echo "    > alter column $column in table $table to $type ...";
		$time=microtime(true);
		$this->getDbConnection()->createCommand()->alterColumn($table, $column, $type);
		echo " done (time: ".sprintf('%.3f', microtime(true)-$time)."s)\n";
	}

	/**
	 * Builds a SQL statement for adding a foreign key constraint to an existing table.
	 * The method will properly quote the table and column names.
	 * @param string $name the name of the foreign key constraint.
	 * @param string $table the table that the foreign key constraint will be added to.
	 * @param string $columns the name of the column to that the constraint will be added on. If there are multiple columns, separate them with commas.
	 * @param string $refTable the table that the foreign key references to.
	 * @param string $refColumns the name of the column that the foreign key references to. If there are multiple columns, separate them with commas.
	 * @param string $delete the ON DELETE option. Most DBMS support these options: RESTRICT, CASCADE, NO ACTION, SET DEFAULT, SET NULL
	 * @param string $update the ON UPDATE option. Most DBMS support these options: RESTRICT, CASCADE, NO ACTION, SET DEFAULT, SET NULL
	 */
	public function addForeignKey($name, $table, $columns, $refTable, $refColumns, $delete=null, $update=null)
	{
		echo "    > add foreign key $name: $table ($columns) references $refTable ($refColumns) ...";
		$time=microtime(true);
		$this->getDbConnection()->createCommand()->addForeignKey($name, $table, $columns, $refTable, $refColumns, $delete, $update);
		echo " done (time: ".sprintf('%.3f', microtime(true)-$time)."s)\n";
	}

	/**
	 * Builds a SQL statement for dropping a foreign key constraint.
	 * @param string $name the name of the foreign key constraint to be dropped. The name will be properly quoted by the method.
	 * @param string $table the table whose foreign is to be dropped. The name will be properly quoted by the method.
	 */
	public function dropForeignKey($name, $table)
	{
		echo "    > drop foreign key $name from table $table ...";
		$time=microtime(true);
		$this->getDbConnection()->createCommand()->dropForeignKey($name, $table);
		echo " done (time: ".sprintf('%.3f', microtime(true)-$time)."s)\n";
	}

	/**
	 * Builds and executes a SQL statement for creating a new index.
	 * @param string $name the name of the index. The name will be properly quoted by the method.
	 * @param string $table the table that the new index will be created for. The table name will be properly quoted by the method.
	 * @param string $column the column(s) that should be included in the index. If there are multiple columns, please separate them
	 * by commas. The column names will be properly quoted by the method.
	 * @param boolean $unique whether to add UNIQUE constraint on the created index.
	 */
	public function createIndex($name, $table, $column, $unique=false)
	{
		echo "    > create".($unique ? ' unique':'')." index $name on $table ($column) ...";
		$time=microtime(true);
		$this->getDbConnection()->createCommand()->createIndex($name, $table, $column, $unique);
		echo " done (time: ".sprintf('%.3f', microtime(true)-$time)."s)\n";
	}

	/**
	 * Builds and executes a SQL statement for dropping an index.
	 * @param string $name the name of the index to be dropped. The name will be properly quoted by the method.
	 * @param string $table the table whose index is to be dropped. The name will be properly quoted by the method.
	 */
	public function dropIndex($name, $table)
	{
		echo "    > drop index $name ...";
		$time=microtime(true);
		$this->getDbConnection()->createCommand()->dropIndex($name, $table);
		echo " done (time: ".sprintf('%.3f', microtime(true)-$time)."s)\n";
	}

	/**
	 * Refreshed schema cache for a table
	 * @param string $table name of the table to refresh
	 * @since 1.1.9
	 */
	public function refreshTableSchema($table)
	{
		echo "    > refresh table $table schema cache ...";
		$time=microtime(true);
		$this->getDbConnection()->getSchema()->getTable($table,true);
		echo " done (time: ".sprintf('%.3f', microtime(true)-$time)."s)\n";
	}
}