package sqlancer.transformations;

import java.util.List;

import net.sf.jsqlparser.expression.Expression;

import net.sf.jsqlparser.statement.select.Distinct;

import net.sf.jsqlparser.statement.select.GroupByElement;

import net.sf.jsqlparser.statement.select.Limit;

import net.sf.jsqlparser.statement.select.Offset;

import net.sf.jsqlparser.statement.select.PlainSelect;

import net.sf.jsqlparser.statement.select.Select;

import net.sf.jsqlparser.statement.select.SubSelect;

import net.sf.jsqlparser.statement.select.WithItem;

import net.sf.jsqlparser.util.deparser.ExpressionDeParser;

import net.sf.jsqlparser.util.deparser.SelectDeParser;

/**

* remove clauses of a select, such as join, where, group by, distinct, offset, limit.

*

* e.g. select * from t where a = b offset 1 limit 1 -> select * from t;

*/

public class RemoveClausesOfSelect extends JSQLParserBasedTransformation {

private final SelectDeParser remover = new SelectDeParser() {

@Override

public void visit(PlainSelect plainSelect) {

handleSelect(plainSelect);

super.visit(plainSelect);

}

};

public RemoveClausesOfSelect() {

super("remove clauses of select");

}

@Override

public boolean init(String original) {

boolean baseSuc = super.init(original);

if (!baseSuc) {

return false;

}

this.remover.setExpressionVisitor(new ExpressionDeParser(remover, new StringBuilder()));

return true;

}

@Override

public void apply() {

super.apply();

if (statement instanceof Select) {

Select select = (Select) statement;

select.getSelectBody().accept(remover);

List<WithItem> withItemsList = select.getWithItemsList();

if (withItemsList == null) {

return;

}

tryRemoveElms(select, withItemsList, Select::setWithItemsList);

for (WithItem withItem : withItemsList) {

SubSelect subSelect = withItem.getSubSelect();

if (subSelect == null) {

return;

}

if (subSelect.getSelectBody() != null) {

subSelect.getSelectBody().accept(remover);

}

}

}

}

private void handleSelect(PlainSelect plainSelect) {

Expression where = plainSelect.getWhere();

if (where != null) {

tryRemove(plainSelect, where, PlainSelect::setWhere);

}

GroupByElement groupByElement = plainSelect.getGroupBy();

if (groupByElement != null) {

tryRemove(plainSelect, groupByElement, PlainSelect::setGroupByElement);

}

Distinct distinct = plainSelect.getDistinct();

if (distinct != null) {

tryRemove(plainSelect, distinct, PlainSelect::setDistinct);

}

Offset offset = plainSelect.getOffset();

if (offset != null) {

tryRemove(plainSelect, offset, PlainSelect::setOffset);

}

Limit limit = plainSelect.getLimit();

if (offset != null) {

tryRemove(plainSelect, limit, PlainSelect::setLimit);

}

}

}