//$Id: OracleDialect.java,v 1.17 2005/09/30 20:56:08 steveebersole Exp $
package org.hibernate.dialect;

import java.sql.Types;

import org.hibernate.sql.CaseFragment;
import org.hibernate.sql.DecodeCaseFragment;
import org.hibernate.sql.JoinFragment;
import org.hibernate.sql.OracleJoinFragment;

/**
 * An SQL dialect for Oracle, compatible with Oracle 8.
 * @author Gavin King
 */
public class OracleDialect extends Oracle9Dialect {

	public OracleDialect() {
		super();
		// Oracle8 and previous define only a "DATE" type which
		//      is used to represent all aspects of date/time
		registerColumnType( Types.TIMESTAMP, "date" );
		registerColumnType( Types.CHAR, "char(1)" );
		registerColumnType( Types.VARCHAR, 4000, "varchar2($l)" );
	}

	public JoinFragment createOuterJoinFragment() {
		return new OracleJoinFragment();
	}
	public CaseFragment createCaseFragment() {
		return new DecodeCaseFragment();
	}

	public String getLimitString(String sql, boolean hasOffset) {

		sql = sql.trim();
		boolean isForUpdate = false;
		if ( sql.toLowerCase().endsWith(" for update") ) {
			sql = sql.substring( 0, sql.length()-11 );
			isForUpdate = true;
		}
		
		StringBuffer pagingSelect = new StringBuffer( sql.length()+100 );
		if (hasOffset) {
			pagingSelect.append("select * from ( select row_.*, rownum rownum_ from ( ");
		}
		else {
			pagingSelect.append("select * from ( ");
		}
		pagingSelect.append(sql);
		if (hasOffset) {
			pagingSelect.append(" ) row_ ) where rownum_ <= ? and rownum_ > ?");
		}
		else {
			pagingSelect.append(" ) where rownum <= ?");
		}

		if (isForUpdate) pagingSelect.append(" for update");
		
		return pagingSelect.toString();
	}

	public String getSelectClauseNullString(int sqlType) {
		switch(sqlType) {
			case Types.VARCHAR:
			case Types.CHAR:
				return "to_char(null)";
			case Types.DATE:
			case Types.TIMESTAMP:
			case Types.TIME:
				return "to_date(null)";
			default:
				return "to_number(null)";
		}
	}

	public String getCurrentTimestampSelectString() {
		return "select sysdate from dual";
	}

}
