package adql.query.constraint;
/*
* This file is part of ADQLLibrary.
*
* ADQLLibrary is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* ADQLLibrary is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with ADQLLibrary. If not, see <http://www.gnu.org/licenses/>.
*
* Copyright 2012-2015 - UDS/Centre de Données astronomiques de Strasbourg (CDS),
* Astronomisches Rechen Institute (ARI)
*/
import java.util.NoSuchElementException;
import adql.query.ADQLIterator;
import adql.query.ADQLObject;
import adql.query.ADQLQuery;
import adql.query.TextPosition;
/**
* <p>Represents the predicate EXISTS of SQL and ADQL.</p>
*
* <p>This function returns <i>true</i> if the sub-query given in parameter returns at least one result, else it returns <i>false</i>.</p>
*
* @author Grégory Mantelet (CDS;ARI)
* @version 1.4 (06/2015)
*/
public class Exists implements ADQLConstraint {
/** The sub-query. */
private ADQLQuery subQuery;
/** Position of this {@link Exists} in the given ADQL query string.
* @since 1.4 */
private TextPosition position = null;
/**
* Builds an Exists constraint instance.
*
* @param query Its sub-query.
*/
public Exists(ADQLQuery query){
subQuery = query;
}
/**
* Builds an Exists constraint by copying the given one.
*
* @param toCopy The Exists constraint to copy.
* @throws Exception If there is an error during the copy.
*/
public Exists(Exists toCopy) throws Exception{
subQuery = (ADQLQuery)toCopy.subQuery.getCopy();
position = (toCopy.position == null) ? null : new TextPosition(toCopy.position);
}
/**
* Gets the sub-query of this EXISTS constraint.
*
* @return Its sub-query.
*/
public final ADQLQuery getSubQuery(){
return subQuery;
}
/**
* Replaces the sub-query of this EXISTS constraint by the given one.
*
* @param query Its new sub-query.
* @throws NullPointerException If the given query is <i>null</i>.
*/
public void setSubQuery(ADQLQuery query) throws NullPointerException{
if (query == null)
throw new NullPointerException("Impossible to build an EXISTS constraint with a sub-query NULL !");
else{
subQuery = query;
position = null;
}
}
@Override
public final TextPosition getPosition(){
return position;
}
/**
* Set the position of this {@link Exists} in the given ADQL query string.
*
* @param position New position of this {@link Exists}.
* @since 1.4
*/
public final void setPosition(final TextPosition position){
this.position = position;
}
@Override
public ADQLObject getCopy() throws Exception{
return new Exists(this);
}
@Override
public String getName(){
return "EXISTS";
}
@Override
public ADQLIterator adqlIterator(){
return new ADQLIterator(){
private boolean subQueryGot = (subQuery == null);
@Override
public ADQLObject next(){
if (subQueryGot)
throw new NoSuchElementException();
subQueryGot = true;
return subQuery;
}
@Override
public boolean hasNext(){
return !subQueryGot;
}
@Override
public void replace(ADQLObject replacer) throws UnsupportedOperationException, IllegalStateException{
if (!subQueryGot)
throw new IllegalStateException("replace(ADQLObject) impossible: next() has not yet been called !");
if (replacer == null)
remove();
else if (replacer instanceof ADQLQuery){
subQuery = (ADQLQuery)replacer;
position = null;
}else
throw new UnsupportedOperationException("Impossible to replace an ADQLQuery by a " + replacer.getClass().getName() + " (" + replacer.toADQL() + ") !");
}
@Override
public void remove(){
if (!subQueryGot)
throw new IllegalStateException("remove() impossible: next() has not yet been called !");
else
throw new UnsupportedOperationException("Impossible to remove the sub-query of an EXISTS constraint !");
}
};
}
@Override
public String toADQL(){
return getName() + "(" + subQuery.toADQL() + ")";
}
}