# TupleQueryExecutor.java

    /*
     * Copyright 2009 Niclas Hedhman.
     *
     * Licensed  under the  Apache License,  Version 2.0  (the "License");
     * you may not use  this file  except in  compliance with the License.
     * You may obtain a copy of the License at
     *
     *   http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed  under the  License is distributed on an "AS IS" BASIS,
     * WITHOUT  WARRANTIES OR CONDITIONS  OF ANY KIND, either  express  or
     * implied.
     *
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */
    package org.qi4j.index.rdf.query;

    import java.util.HashMap;
    import java.util.Map;
    import org.openrdf.model.Value;
    import org.openrdf.model.impl.ValueFactoryImpl;
    import org.openrdf.query.*;
    import org.openrdf.repository.Repository;
    import org.openrdf.repository.RepositoryConnection;
    import org.openrdf.repository.RepositoryException;
    import org.qi4j.api.common.Optional;
    import org.qi4j.api.entity.EntityReference;
    import org.qi4j.api.injection.scope.Service;
    import org.qi4j.api.mixin.Mixins;
    import org.qi4j.spi.query.EntityFinderException;

    @Mixins( TupleQueryExecutor.TupleQueryExecutorMixin.class )
    public interface TupleQueryExecutor
    {
        long performTupleQuery( QueryLanguage language, String query, @Optional Map<String, Object> bindings, @Optional QualifiedIdentityResultCallback callback )
            throws EntityFinderException;

        class TupleQueryExecutorMixin
            implements TupleQueryExecutor
        {
            @Service
            private Repository repository;

            @Override
            public long performTupleQuery( QueryLanguage language, String query, Map<String, Object> bindings, QualifiedIdentityResultCallback callback )
                throws EntityFinderException
            {
                try
                {
                    RepositoryConnection connection = repository.getConnection();
                    TupleQueryResult result = null;
                    try
                    {

                        TupleQuery tupleQuery = connection.prepareTupleQuery( language, query );

                        for (Map.Entry<String, Value> stringValueEntry : getBindings( bindings ).entrySet())
                        {
                            tupleQuery.setBinding(stringValueEntry.getKey(), stringValueEntry.getValue());
                        }

                        tupleQuery.setIncludeInferred( false );
                        result = tupleQuery.evaluate();
                        long row = 0;
                        while( result.hasNext() )
                        {
                            if( handleCallbacks( callback, result, row ) )
                            {
                                break;
                            }
                            row++;
                        }
                        return row;
                    }
                    finally
                    {
                        if( result != null )
                        {
                            result.close();
                        }
                        if( connection != null )
                        {
                            connection.close();
                        }
                    }
                }
                catch( RepositoryException e )
                {
                    throw new EntityFinderException( e );
                }
                catch( MalformedQueryException e )
                {
                    throw new EntityFinderException( e );
                }
                catch( QueryEvaluationException e )
                {
                    throw new EntityFinderException( e );
                }
                catch( Exception e )
                {
                    throw new EntityFinderException( e );
                }
            }

            private boolean handleCallbacks( QualifiedIdentityResultCallback callback, TupleQueryResult result, long row )
                throws Exception
            {
                BindingSet bindingSet = result.next();
                if( callback != null )
                {
                    if( !processRow( row, bindingSet, callback ) )
                    {
                        return true;
                    }
                }
                return false;
            }

            private boolean processRow( long row, BindingSet bindingSet, QualifiedIdentityResultCallback callback )
            {
                final Value identifier = bindingSet.getValue( "identity" );

                //TODO Shall we throw an exception if there is no binding for identifier = query parser is not right
                if( identifier == null )
                {
                    return true;
                }

                final String identity = identifier.stringValue();

                final EntityReference entityReference = new EntityReference( identity );
                return callback.processRow( row, entityReference );
            }

            private Map<String, Value> getBindings(Map<String, Object> variables)
            {
                Map<String, Value> bindings = new HashMap<String, Value>();
                for (Map.Entry<String, Object> stringObjectEntry : variables.entrySet())
                {
                    if (!stringObjectEntry.getValue().getClass().equals(Object.class))
                        bindings.put(stringObjectEntry.getKey(), ValueFactoryImpl.getInstance().createLiteral(stringObjectEntry.getValue().toString()));
                }
                return bindings;
            }
        }
    }