package it.unimi.dsi.mg4j.query.nodes;
import java.util.Arrays;
import it.unimi.dsi.fastutil.objects.ObjectOpenHashSet;
import it.unimi.dsi.mg4j.index.MultiTermIndexIterator;
import it.unimi.dsi.mg4j.search.DocumentIterator;
import it.unimi.dsi.lang.MutableString;
/*
* MG4J: Managing Gigabytes for Java
*
* Copyright (C) 2007-2010 Sebastiano Vigna
*
* This library 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.
*
* This library 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 this program; if not, see <http://www.gnu.org/licenses/>.
*
*/
/** A node representing a virtual term obtained by merging the occurrences of the given (possibly weighted) terms.
*
* <p>This node is mainly useful when performing query expansion. The {@link QueryBuilderVisitor}
* used to generate {@linkplain DocumentIterator document iterators} can decide which
* policy to use for setting the frequency and the name of the virtual term.
*
* @author Sebastiano Vigna
* @see MultiTermIndexIterator
*/
public class MultiTerm extends Composite {
/** Creates a new multi-term node.
*
* @param query a vector of nodes representing distinct terms; they must be either instances
* of {@link Term}, or instances of {@link Weight} containing instances of {@link Term}.
* @throws IllegalArgumentException if some term appears twice in <code>query</code>, or if
* the specification is not followed.
*/
public MultiTerm( final Query... query ) {
super( query );
final ObjectOpenHashSet<MutableString> s = new ObjectOpenHashSet<MutableString>( query.length );
for( Query q : query ) {
if ( ! ( q instanceof Term ) && ! ( ( q instanceof Weight ) && ( ((Weight)q).query instanceof Term ) ) ) throw new IllegalArgumentException();
s.add( new MutableString( q instanceof Term ? ((Term)q).term : ((Term)((Weight)q).query ).term ) );
}
if ( s.size() != query.length ) throw new IllegalArgumentException( "Multiterm nodes require distinct terms" );
}
public String toString() {
return super.toString( "MULTITERM(", ")", ", " );
}
public <T> T accept( final QueryBuilderVisitor<T> visitor ) throws QueryBuilderVisitorException {
if ( ! visitor.visitPre( this ) ) return null;
final T[] result = visitor.newArray( query.length );
for( int i = 0; i < query.length; i++ ) if ( ( result[ i ] = query[ i ].accept( visitor ) ) == null ) return null;
return visitor.visitPost( this, result );
}
public boolean equals( final Object o ) {
if ( ! ( o instanceof MultiTerm ) ) return false;
return Arrays.equals( query, ((MultiTerm)o).query );
}
public int hashCode() {
return Arrays.hashCode( query ) ^ getClass().hashCode();
}
}