<?php
/**
 * CDbSchema 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/
 */

/**
 * CDbSchema is the base class for retrieving metadata information.
 *
 * @property CDbConnection $dbConnection Database connection. The connection is active.
 * @property array $tables The metadata for all tables in the database.
 * Each array element is an instance of {@link CDbTableSchema} (or its child class).
 * The array keys are table names.
 * @property array $tableNames All table names in the database.
 * @property CDbCommandBuilder $commandBuilder The SQL command builder for this connection.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @version $Id$
 * @package system.db.schema
 * @since 1.0
 */
abstract class CDbSchema extends CComponent
{
	/**
	 * @var array the abstract column types mapped to physical column types.
	 * @since 1.1.6
	 */
	public $columnTypes=array();

	private $_tableNames=array();
	private $_tables=array();
	private $_connection;
	private $_builder;
	private $_cacheExclude=array();

	/**
	 * Loads the metadata for the specified table.
	 * @param string $name table name
	 * @return CDbTableSchema driver dependent table metadata, null if the table does not exist.
	 */
	abstract protected function loadTable($name);

	/**
	 * Constructor.
	 * @param CDbConnection $conn database connection.
	 */
	public function __construct($conn)
	{
		$this->_connection=$conn;
		foreach($conn->schemaCachingExclude as $name)
			$this->_cacheExclude[$name]=true;
	}

	/**
	 * @return CDbConnection database connection. The connection is active.
	 */
	public function getDbConnection()
	{
		return $this->_connection;
	}

	/**
	 * Obtains the metadata for the named table.
	 * @param string $name table name
	 * @param boolean $refresh if we need to refresh schema cache for a table.
	 * Parameter available since 1.1.9
	 * @return CDbTableSchema table metadata. Null if the named table does not exist.
	 */
	public function getTable($name,$refresh=false)
	{
		if($refresh===false && isset($this->_tables[$name]))
			return $this->_tables[$name];
		else
		{
			if($this->_connection->tablePrefix!==null && strpos($name,'{{')!==false)
				$realName=preg_replace('/\{\{(.*?)\}\}/',$this->_connection->tablePrefix.'$1',$name);
			else
				$realName=$name;

			// temporarily disable query caching
			if($this->_connection->queryCachingDuration>0)
			{
				$qcDuration=$this->_connection->queryCachingDuration;
				$this->_connection->queryCachingDuration=0;
			}

			if(!isset($this->_cacheExclude[$name]) && ($duration=$this->_connection->schemaCachingDuration)>0 && $this->_connection->schemaCacheID!==false && ($cache=Yii::app()->getComponent($this->_connection->schemaCacheID))!==null)
			{
				$key='yii:dbschema'.$this->_connection->connectionString.':'.$this->_connection->username.':'.$name;
				$table=$cache->get($key);
				if($refresh===true || $table===false)
				{
					$table=$this->loadTable($realName);
					if($table!==null)
						$cache->set($key,$table,$duration);
				}
				$this->_tables[$name]=$table;
			}
			else
				$this->_tables[$name]=$table=$this->loadTable($realName);

			if(isset($qcDuration))  // re-enable query caching
				$this->_connection->queryCachingDuration=$qcDuration;

			return $table;
		}
	}

	/**
	 * Returns the metadata for all tables in the database.
	 * @param string $schema the schema of the tables. Defaults to empty string, meaning the current or default schema.
	 * @return array the metadata for all tables in the database.
	 * Each array element is an instance of {@link CDbTableSchema} (or its child class).
	 * The array keys are table names.
	 */
	public function getTables($schema='')
	{
		$tables=array();
		foreach($this->getTableNames($schema) as $name)
		{
			if(($table=$this->getTable($name))!==null)
				$tables[$name]=$table;
		}
		return $tables;
	}

	/**
	 * Returns all table names in the database.
	 * @param string $schema the schema of the tables. Defaults to empty string, meaning the current or default schema.
	 * If not empty, the returned table names will be prefixed with the schema name.
	 * @return array all table names in the database.
	 */
	public function getTableNames($schema='')
	{
		if(!isset($this->_tableNames[$schema]))
			$this->_tableNames[$schema]=$this->findTableNames($schema);
		return $this->_tableNames[$schema];
	}

	/**
	 * @return CDbCommandBuilder the SQL command builder for this connection.
	 */
	public function getCommandBuilder()
	{
		if($this->_builder!==null)
			return $this->_builder;
		else
			return $this->_builder=$this->createCommandBuilder();
	}

	/**
	 * Refreshes the schema.
	 * This method resets the loaded table metadata and command builder
	 * so that they can be recreated to reflect the change of schema.
	 */
	public function refresh()
	{
		if(($duration=$this->_connection->schemaCachingDuration)>0 && $this->_connection->schemaCacheID!==false && ($cache=Yii::app()->getComponent($this->_connection->schemaCacheID))!==null)
		{
			foreach(array_keys($this->_tables) as $name)
			{
				if(!isset($this->_cacheExclude[$name]))
				{
					$key='yii:dbschema'.$this->_connection->connectionString.':'.$this->_connection->username.':'.$name;
					$cache->delete($key);
				}
			}
		}
		$this->_tables=array();
		$this->_tableNames=array();
		$this->_builder=null;
	}

	/**
	 * Quotes a table name for use in a query.
	 * If the table name contains schema prefix, the prefix will also be properly quoted.
	 * @param string $name table name
	 * @return string the properly quoted table name
	 * @see quoteSimpleTableName
	 */
	public function quoteTableName($name)
	{
		if(strpos($name,'.')===false)
			return $this->quoteSimpleTableName($name);
		$parts=explode('.',$name);
		foreach($parts as $i=>$part)
			$parts[$i]=$this->quoteSimpleTableName($part);
		return implode('.',$parts);

	}

	/**
	 * Quotes a simple table name for use in a query.
	 * A simple table name does not schema prefix.
	 * @param string $name table name
	 * @return string the properly quoted table name
	 * @since 1.1.6
	 */
	public function quoteSimpleTableName($name)
	{
		return "'".$name."'";
	}

	/**
	 * Quotes a column name for use in a query.
	 * If the column name contains prefix, the prefix will also be properly quoted.
	 * @param string $name column name
	 * @return string the properly quoted column name
	 * @see quoteSimpleColumnName
	 */
	public function quoteColumnName($name)
	{
		if(($pos=strrpos($name,'.'))!==false)
		{
			$prefix=$this->quoteTableName(substr($name,0,$pos)).'.';
			$name=substr($name,$pos+1);
		}
		else
			$prefix='';
		return $prefix . ($name==='*' ? $name : $this->quoteSimpleColumnName($name));
	}

	/**
	 * Quotes a simple column name for use in a query.
	 * A simple column name does not contain prefix.
	 * @param string $name column name
	 * @return string the properly quoted column name
	 * @since 1.1.6
	 */
	public function quoteSimpleColumnName($name)
	{
		return '"'.$name.'"';
	}

	/**
	 * Compares two table names.
	 * The table names can be either quoted or unquoted. This method
	 * will consider both cases.
	 * @param string $name1 table name 1
	 * @param string $name2 table name 2
	 * @return boolean whether the two table names refer to the same table.
	 */
	public function compareTableNames($name1,$name2)
	{
		$name1=str_replace(array('"','`',"'"),'',$name1);
		$name2=str_replace(array('"','`',"'"),'',$name2);
		if(($pos=strrpos($name1,'.'))!==false)
			$name1=substr($name1,$pos+1);
		if(($pos=strrpos($name2,'.'))!==false)
			$name2=substr($name2,$pos+1);
		if($this->_connection->tablePrefix!==null)
		{
			if(strpos($name1,'{')!==false)
				$name1=$this->_connection->tablePrefix.str_replace(array('{','}'),'',$name1);
			if(strpos($name2,'{')!==false)
				$name2=$this->_connection->tablePrefix.str_replace(array('{','}'),'',$name2);
		}
		return $name1===$name2;
	}

	/**
	 * Resets the sequence value of a table's primary key.
	 * The sequence will be reset such that the primary key of the next new row inserted
	 * will have the specified value or 1.
	 * @param CDbTableSchema $table the table schema whose primary key sequence will be reset
	 * @param mixed $value the value for the primary key of the next new row inserted. If this is not set,
	 * the next new row's primary key will have a value 1.
	 * @since 1.1
	 */
	public function resetSequence($table,$value=null)
	{
	}

	/**
	 * Enables or disables integrity check.
	 * @param boolean $check whether to turn on or off the integrity check.
	 * @param string $schema the schema of the tables. Defaults to empty string, meaning the current or default schema.
	 * @since 1.1
	 */
	public function checkIntegrity($check=true,$schema='')
	{
	}

	/**
	 * Creates a command builder for the database.
	 * This method may be overridden by child classes to create a DBMS-specific command builder.
	 * @return CDbCommandBuilder command builder instance
	 */
	protected function createCommandBuilder()
	{
		return new CDbCommandBuilder($this);
	}

	/**
	 * Returns all table names in the database.
	 * This method should be overridden by child classes in order to support this feature
	 * because the default implementation simply throws an exception.
	 * @param string $schema the schema of the tables. Defaults to empty string, meaning the current or default schema.
	 * If not empty, the returned table names will be prefixed with the schema name.
	 * @return array all table names in the database.
	 */
	protected function findTableNames($schema='')
	{
		throw new CDbException(Yii::t('yii','{class} does not support fetching all table names.',
			array('{class}'=>get_class($this))));
	}

	/**
	 * Converts an abstract column type into a physical column type.
	 * The conversion is done using the type map specified in {@link columnTypes}.
	 * These abstract column types are supported (using MySQL as example to explain the corresponding
	 * physical types):
	 * <ul>
	 * <li>pk: an auto-incremental primary key type, will be converted into "int(11) NOT NULL AUTO_INCREMENT PRIMARY KEY"</li>
	 * <li>string: string type, will be converted into "varchar(255)"</li>
	 * <li>text: a long string type, will be converted into "text"</li>
	 * <li>integer: integer type, will be converted into "int(11)"</li>
	 * <li>boolean: boolean type, will be converted into "tinyint(1)"</li>
	 * <li>float: float number type, will be converted into "float"</li>
	 * <li>decimal: decimal number type, will be converted into "decimal"</li>
	 * <li>datetime: datetime type, will be converted into "datetime"</li>
	 * <li>timestamp: timestamp type, will be converted into "timestamp"</li>
	 * <li>time: time type, will be converted into "time"</li>
	 * <li>date: date type, will be converted into "date"</li>
	 * <li>binary: binary data type, will be converted into "blob"</li>
	 * </ul>
	 *
	 * If the abstract type contains two or more parts separated by spaces (e.g. "string NOT NULL"), then only
	 * the first part will be converted, and the rest of the parts will be appended to the conversion result.
	 * For example, 'string NOT NULL' is converted to 'varchar(255) NOT NULL'.
	 * @param string $type abstract column type
	 * @return string physical column type.
	 * @since 1.1.6
	 */
    public function getColumnType($type)
    {
    	if(isset($this->columnTypes[$type]))
    		return $this->columnTypes[$type];
    	else if(($pos=strpos($type,' '))!==false)
    	{
    		$t=substr($type,0,$pos);
    		return (isset($this->columnTypes[$t]) ? $this->columnTypes[$t] : $t).substr($type,$pos);
    	}
    	else
    		return $type;
    }

	/**
	 * Builds 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 $options additional SQL fragment that will be appended to the generated SQL.
	 * @return string the SQL statement for creating a new DB table.
	 * @since 1.1.6
	 */
	public function createTable($table, $columns, $options=null)
	{
		$cols=array();
		foreach($columns as $name=>$type)
		{
			if(is_string($name))
				$cols[]="\t".$this->quoteColumnName($name).' '.$this->getColumnType($type);
			else
				$cols[]="\t".$type;
		}
		$sql="CREATE TABLE ".$this->quoteTableName($table)." (\n".implode(",\n",$cols)."\n)";
		return $options===null ? $sql : $sql.' '.$options;
	}

	/**
	 * Builds 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 $newName the new table name. The name will be properly quoted by the method.
	 * @return string the SQL statement for renaming a DB table.
	 * @since 1.1.6
	 */
	public function renameTable($table, $newName)
	{
		return 'RENAME TABLE ' . $this->quoteTableName($table) . ' TO ' . $this->quoteTableName($newName);
	}

	/**
	 * Builds a SQL statement for dropping a DB table.
	 * @param string $table the table to be dropped. The name will be properly quoted by the method.
	 * @return string the SQL statement for dropping a DB table.
	 * @since 1.1.6
	 */
	public function dropTable($table)
	{
		return "DROP TABLE ".$this->quoteTableName($table);
	}

	/**
	 * Builds a SQL statement for truncating a DB table.
	 * @param string $table the table to be truncated. The name will be properly quoted by the method.
	 * @return string the SQL statement for truncating a DB table.
	 * @since 1.1.6
	 */
	public function truncateTable($table)
	{
		return "TRUNCATE TABLE ".$this->quoteTableName($table);
	}

	/**
	 * Builds 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 $type the column type. The {@link getColumnType} method will be invoked to convert abstract column type (if any)
	 * into the physical one. Anything that is not recognized as abstract type will be kept in the generated SQL.
	 * For example, 'string' will be turned into 'varchar(255)', while 'string not null' will become 'varchar(255) not null'.
	 * @return string the SQL statement for adding a new column.
	 * @since 1.1.6
	 */
	public function addColumn($table, $column, $type)
	{
		return 'ALTER TABLE ' . $this->quoteTableName($table)
			. ' ADD ' . $this->quoteColumnName($column) . ' '
			. $this->getColumnType($type);
	}

	/**
	 * Builds 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 $column the name of the column to be dropped. The name will be properly quoted by the method.
	 * @return string the SQL statement for dropping a DB column.
	 * @since 1.1.6
	 */
	public function dropColumn($table, $column)
	{
		return "ALTER TABLE ".$this->quoteTableName($table)
			." DROP COLUMN ".$this->quoteColumnName($column);
	}

	/**
	 * Builds 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 $newName the new name of the column. The name will be properly quoted by the method.
	 * @return string the SQL statement for renaming a DB column.
	 * @since 1.1.6
	 */
	public function renameColumn($table, $name, $newName)
	{
		return "ALTER TABLE ".$this->quoteTableName($table)
			. " RENAME COLUMN ".$this->quoteColumnName($name)
			. " TO ".$this->quoteColumnName($newName);
	}

	/**
	 * Builds 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 $type the new column type. The {@link getColumnType} method will be invoked to convert abstract column type (if any)
	 * into the physical one. Anything that is not recognized as abstract type will be kept in the generated SQL.
	 * For example, 'string' will be turned into 'varchar(255)', while 'string not null' will become 'varchar(255) not null'.
	 * @return string the SQL statement for changing the definition of a column.
	 * @since 1.1.6
	 */
	public function alterColumn($table, $column, $type)
	{
		return 'ALTER TABLE ' . $this->quoteTableName($table) . ' CHANGE '
			. $this->quoteColumnName($column) . ' '
			. $this->quoteColumnName($column) . ' '
			. $this->getColumnType($type);
	}

	/**
	 * 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 $update the ON UPDATE option. Most DBMS support these options: RESTRICT, CASCADE, NO ACTION, SET DEFAULT, SET NULL
	 * @return string the SQL statement for adding a foreign key constraint to an existing table.
	 * @since 1.1.6
	 */
	public function addForeignKey($name, $table, $columns, $refTable, $refColumns, $delete=null, $update=null)
	{
		$columns=preg_split('/\s*,\s*/',$columns,-1,PREG_SPLIT_NO_EMPTY);
		foreach($columns as $i=>$col)
			$columns[$i]=$this->quoteColumnName($col);
		$refColumns=preg_split('/\s*,\s*/',$refColumns,-1,PREG_SPLIT_NO_EMPTY);
		foreach($refColumns as $i=>$col)
			$refColumns[$i]=$this->quoteColumnName($col);
		$sql='ALTER TABLE '.$this->quoteTableName($table)
			.' ADD CONSTRAINT '.$this->quoteColumnName($name)
			.' FOREIGN KEY ('.implode(', ', $columns).')'
			.' REFERENCES '.$this->quoteTableName($refTable)
			.' ('.implode(', ', $refColumns).')';
		if($delete!==null)
			$sql.=' ON DELETE '.$delete;
		if($update!==null)
			$sql.=' ON UPDATE '.$update;
		return $sql;
	}

	/**
	 * 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 $table the table whose foreign is to be dropped. The name will be properly quoted by the method.
	 * @return string the SQL statement for dropping a foreign key constraint.
	 * @since 1.1.6
	 */
	public function dropForeignKey($name, $table)
	{
		return 'ALTER TABLE '.$this->quoteTableName($table)
			.' DROP CONSTRAINT '.$this->quoteColumnName($name);
	}

	/**
	 * Builds 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. Each column name will be properly quoted by the method, unless a parenthesis is found in the name.
	 * @param boolean $unique whether to add UNIQUE constraint on the created index.
	 * @return string the SQL statement for creating a new index.
	 * @since 1.1.6
	 */
	public function createIndex($name, $table, $column, $unique=false)
	{
		$cols=array();
		$columns=preg_split('/\s*,\s*/',$column,-1,PREG_SPLIT_NO_EMPTY);
		foreach($columns as $col)
		{
			if(strpos($col,'(')!==false)
				$cols[]=$col;
			else
				$cols[]=$this->quoteColumnName($col);
		}
		return ($unique ? 'CREATE UNIQUE INDEX ' : 'CREATE INDEX ')
			. $this->quoteTableName($name).' ON '
			. $this->quoteTableName($table).' ('.implode(', ',$cols).')';
	}

	/**
	 * Builds 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 $table the table whose index is to be dropped. The name will be properly quoted by the method.
	 * @return string the SQL statement for dropping an index.
	 * @since 1.1.6
	 */
	public function dropIndex($name, $table)
	{
		return 'DROP INDEX '.$this->quoteTableName($name).' ON '.$this->quoteTableName($table);
	}
}
