/**
 * Copyright (c) 2002-2011 "Neo Technology,"
 * Network Engine for Objects in Lund AB [http://neotechnology.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
package org.neo4j.index.impl.lucene;

import org.apache.lucene.queryParser.QueryParser.Operator;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Sort;
import org.apache.lucene.search.SortField;
import org.neo4j.graphdb.index.Index;
import org.neo4j.graphdb.index.IndexHits;

/**
 * This class has the extra query configuration to use
 * with {@link Index#query(Object)} and {@link Index#query(String, Object)}.
 * It allows a query to have sorting, default operators, and allows the engine
 * to turn of searching of modifications made inside a transaction,
 * to gain performance.
 */
public class QueryContext
{
    final Object queryOrQueryObject;
    Sort sorting;
    Operator defaultOperator;
    boolean tradeCorrectnessForSpeed;
    int topHits;
    
    public QueryContext( Object queryOrQueryObject )
    {
        this.queryOrQueryObject = queryOrQueryObject;
    }

    /**
     * Returns a QueryContext with sorting added to it.
     *
     * @param sorting The sorting to be used
     * @return A QueryContext with the sorting applied.
     */
    public QueryContext sort( Sort sorting )
    {
        this.sorting = sorting;
        return this;
    }

    /**
     * Returns a QueryContext with sorting added to it.
     *
     * @param key The key to sort on.
     * @param additionalKeys Any additional keys to sort on.
     * @return A QueryContext with sorting added to it.
     */
    public QueryContext sort( String key, String... additionalKeys )
    {
        SortField firstSortField = new SortField( key, SortField.STRING );
        if ( additionalKeys.length == 0 )
        {
            return sort( new Sort( firstSortField ) );
        }
        
        SortField[] sortFields = new SortField[1+additionalKeys.length];
        sortFields[0] = firstSortField;
        for ( int i = 0; i < additionalKeys.length; i++ )
        {
            sortFields[1+i] = new SortField( additionalKeys[i], SortField.STRING );
        }
        return sort( new Sort( sortFields ) );
    }

    /**
     * Lucenes default operator is OR. Using this method, the default operator
     * can be changed for the query.
     *
     * @param defaultOperator The new operator to use.
     * @return A QueryContext with the new default operator applied.
     */
    public QueryContext defaultOperator( Operator defaultOperator )
    {
        this.defaultOperator = defaultOperator;
        return this;
    }

    /**
     * Adding to or removing from an index affects results from query methods
     * inside the same transaction, even before those changes are committed.
     * To let those modifications be visible in query results, some rather heavy
     * operations may have to be done, which can be slow to complete.
     *
     * The default behaviour is that these modifications are visible, but using
     * this method will tell the query to not strive to include the absolutely
     * latest modifications, so that such a performance penalty can be avoided.
     *
     * @return A QueryContext which doesn't necessarily include the latest
     * transaction modifications in the results, but may perform faster.
     */
    public QueryContext tradeCorrectnessForSpeed()
    {
        this.tradeCorrectnessForSpeed = true;
        return this;
    }
    
    /**
     * Makes use of {@link IndexSearcher#search(org.apache.lucene.search.Query, int)},
     * alt {@link IndexSearcher#search(org.apache.lucene.search.Query, org.apache.lucene.search.Filter, int, Sort)}
     * where only the top {@code numberOfTopHits} hits are returned. Default
     * behaviour is to return all hits, although lazily retrieved from lucene all
     * the way up to the {@link IndexHits} iterator.
     * 
     * @param numberOfTopHits the maximum number of top hits to return.
     * @return A {@link QueryContext} with the number of top hits set.
     */
    public QueryContext topDocs( int numberOfTopHits )
    {
        this.topHits = numberOfTopHits;
        return this;
    }
}