# CargoFactory.java

    /*
     * Copyright 2011 Marc Grue.
     *
     * 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.sample.dcicargo.sample_b.data.factory;

    import java.util.UUID;
    import org.qi4j.api.common.Optional;
    import org.qi4j.api.constraint.ConstraintViolationException;
    import org.qi4j.api.entity.EntityBuilder;
    import org.qi4j.api.injection.scope.Structure;
    import org.qi4j.api.mixin.Mixins;
    import org.qi4j.api.unitofwork.NoSuchEntityException;
    import org.qi4j.api.unitofwork.UnitOfWork;
    import org.qi4j.api.unitofwork.UnitOfWorkFactory;
    import org.qi4j.api.value.ValueBuilder;
    import org.qi4j.api.value.ValueBuilderFactory;
    import org.qi4j.sample.dcicargo.sample_b.data.factory.exception.CannotCreateCargoException;
    import org.qi4j.sample.dcicargo.sample_b.data.structure.cargo.Cargo;
    import org.qi4j.sample.dcicargo.sample_b.data.structure.cargo.RouteSpecification;
    import org.qi4j.sample.dcicargo.sample_b.data.structure.delivery.Delivery;
    import org.qi4j.sample.dcicargo.sample_b.data.structure.tracking.TrackingId;

    /**
     * Cargo factory
     *
     * If an empty tracking id string is received the factory will create an automated tracking id.
     *
     * Validations of RouteSpecification and Delivery are considered out of this scope.
     */
    @Mixins( CargoFactory.Mixin.class )
    public interface CargoFactory
    {
        Cargo createCargo( RouteSpecification routeSpecification, Delivery delivery, @Optional String id )
            throws CannotCreateCargoException;

        class Mixin
            implements CargoFactory
        {
            @Structure
            UnitOfWorkFactory uowf;

            @Structure
            ValueBuilderFactory vbf;

            public Cargo createCargo( RouteSpecification routeSpecification, Delivery delivery, String id )
                throws ConstraintViolationException, CannotCreateCargoException
            {
                TrackingId trackingId = buildTrackingId( id );

                UnitOfWork uow = uowf.currentUnitOfWork();
                EntityBuilder<Cargo> cargoBuilder = uow.newEntityBuilder( Cargo.class, trackingId.id().get() );
                cargoBuilder.instance().trackingId().set( trackingId );
                cargoBuilder.instance().origin().set( routeSpecification.origin().get() );
                cargoBuilder.instance().routeSpecification().set( routeSpecification );
                cargoBuilder.instance().delivery().set( delivery );

                return cargoBuilder.newInstance();
            }

            private TrackingId buildTrackingId( String id )
                throws CannotCreateCargoException
            {
                if( id == null || id.trim().equals( "" ) )
                {
                    // Build random tracking id
                    final String uuid = UUID.randomUUID().toString().toUpperCase();
                    id = uuid.substring( 0, uuid.indexOf( "-" ) );
                }
                else
                {
                    try
                    {
                        // Verify that tracking id doesn't exist in store
                        uowf.currentUnitOfWork().get( Cargo.class, id );
                        throw new CannotCreateCargoException( "Tracking id '" + id + "' is not unique." );
                    }
                    catch( NoSuchEntityException e )
                    {
                        // Ok: tracking id is unique
                    }
                }

                ValueBuilder<TrackingId> trackingIdBuilder = vbf.newValueBuilder( TrackingId.class );
                trackingIdBuilder.prototype().id().set( id );
                return trackingIdBuilder.newInstance();
            }
        }
    }