/*
* Copyright Aduna (http://www.aduna-software.com/) (c) 2008.
*
* Licensed under the Aduna BSD-style license.
*/
package org.openrdf.sail.rdbms.algebra.factories;
import static org.openrdf.sail.rdbms.algebra.base.SqlExprSupport.coalesce;
import static org.openrdf.sail.rdbms.algebra.base.SqlExprSupport.isNotNull;
import static org.openrdf.sail.rdbms.algebra.base.SqlExprSupport.sqlNull;
import static org.openrdf.sail.rdbms.algebra.base.SqlExprSupport.str;
import static org.openrdf.sail.rdbms.algebra.base.SqlExprSupport.text;
import static org.openrdf.sail.rdbms.algebra.base.SqlExprSupport.unsupported;
import org.openrdf.model.Literal;
import org.openrdf.model.Value;
import org.openrdf.query.algebra.Datatype;
import org.openrdf.query.algebra.Lang;
import org.openrdf.query.algebra.MathExpr;
import org.openrdf.query.algebra.QueryModelNode;
import org.openrdf.query.algebra.Str;
import org.openrdf.query.algebra.ValueConstant;
import org.openrdf.query.algebra.ValueExpr;
import org.openrdf.query.algebra.Var;
import org.openrdf.query.algebra.helpers.QueryModelVisitorBase;
import org.openrdf.sail.rdbms.algebra.LabelColumn;
import org.openrdf.sail.rdbms.algebra.LongLabelColumn;
import org.openrdf.sail.rdbms.algebra.SqlCase;
import org.openrdf.sail.rdbms.algebra.SqlNull;
import org.openrdf.sail.rdbms.algebra.base.SqlExpr;
import org.openrdf.sail.rdbms.exceptions.UnsupportedRdbmsOperatorException;
/**
* Creates a SQl expression of a literal label.
*
* @author James Leigh
*/
public class LabelExprFactory extends QueryModelVisitorBase<UnsupportedRdbmsOperatorException> {
protected SqlExpr result;
private SqlExprFactory sql;
public void setSqlExprFactory(SqlExprFactory sql) {
this.sql = sql;
}
public SqlExpr createLabelExpr(ValueExpr expr)
throws UnsupportedRdbmsOperatorException
{
result = null;
if (expr == null) {
return new SqlNull();
}
expr.visit(this);
if (result == null) {
return new SqlNull();
}
return result;
}
@Override
public void meet(Datatype node)
throws UnsupportedRdbmsOperatorException
{
result = sqlNull();
}
@Override
public void meet(Lang node)
throws UnsupportedRdbmsOperatorException
{
SqlCase sqlCase = new SqlCase();
sqlCase.when(isNotNull(lang(node.getArg())), lang(node.getArg()));
sqlCase.when(isNotNull(createLabelExpr(node.getArg())), str(""));
result = sqlCase;
}
@Override
public void meet(MathExpr node)
throws UnsupportedRdbmsOperatorException
{
result = text(num(node));
}
@Override
public void meet(Str str)
throws UnsupportedRdbmsOperatorException
{
ValueExpr arg = str.getArg();
result = coalesce(uri(arg), createLabelExpr(arg));
}
@Override
public void meet(ValueConstant vc) {
result = valueOf(vc.getValue());
}
@Override
public void meet(Var var) {
if (var.getValue() == null) {
result = coalesce(new LabelColumn(var), new LongLabelColumn(var));
}
else {
result = valueOf(var.getValue());
}
}
@Override
protected void meetNode(QueryModelNode arg)
throws UnsupportedRdbmsOperatorException
{
throw unsupported(arg);
}
private SqlExpr lang(ValueExpr arg)
throws UnsupportedRdbmsOperatorException
{
return sql.createLanguageExpr(arg);
}
private SqlExpr uri(ValueExpr arg)
throws UnsupportedRdbmsOperatorException
{
return sql.createUriExpr(arg);
}
private SqlExpr num(ValueExpr arg)
throws UnsupportedRdbmsOperatorException
{
return sql.createNumericExpr(arg);
}
private SqlExpr valueOf(Value value) {
if (value instanceof Literal) {
return str(((Literal)value).getLabel());
}
return sqlNull();
}
}