package org.basex.query.expr;
import org.basex.query.QueryContext;
import org.basex.query.QueryException;
import org.basex.query.item.Item;
import org.basex.query.item.ANode;
import org.basex.query.iter.Iter;
import org.basex.query.iter.NodeCache;
import org.basex.query.iter.NodeIter;
import org.basex.util.InputInfo;
/**
* Intersect expression.
*
* @author BaseX Team 2005-12, BSD License
* @author Christian Gruen
*/
public final class InterSect extends Set {
/**
* Constructor.
* @param ii input info
* @param l expression list
*/
public InterSect(final InputInfo ii, final Expr[] l) {
super(ii, l);
}
@Override
public Expr comp(final QueryContext ctx) throws QueryException {
super.comp(ctx);
return oneIsEmpty() ? optPre(null, ctx) : this;
}
@Override
protected NodeCache eval(final Iter[] iter) throws QueryException {
NodeCache nc = new NodeCache();
for(Item it; (it = iter[0].next()) != null;) nc.add(checkNode(it));
final boolean db = nc.dbnodes();
for(int e = 1; e != expr.length && nc.size() != 0; ++e) {
final NodeCache nt = new NodeCache().random();
final Iter ir = iter[e];
for(Item it; (it = ir.next()) != null;) {
final ANode n = checkNode(it);
final int i = nc.indexOf(n, db);
if(i != -1) nt.add(n);
}
nc = nt;
}
return nc;
}
@Override
protected NodeIter iter(final Iter[] iter) {
return new SetIter(iter) {
@Override
public ANode next() throws QueryException {
if(item == null) item = new ANode[iter.length];
for(int i = 0; i != iter.length; ++i) if(!next(i)) return null;
for(int i = 1; i != item.length;) {
final int d = item[0].diff(item[i]);
if(d > 0) {
if(!next(i)) return null;
} else if(d < 0) {
if(!next(0)) return null;
i = 1;
} else {
++i;
}
}
return item[0];
}
};
}
}