# FunctionStateResolver.java

    /*
     * Copyright (c) 2012, Kent Sølvsten.
     *
     * 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.runtime.composite;

    import java.util.List;
    import java.util.Map;
    import org.qi4j.api.association.AssociationDescriptor;
    import org.qi4j.api.entity.EntityReference;
    import org.qi4j.api.property.PropertyDescriptor;
    import org.qi4j.functional.ForEach;
    import org.qi4j.functional.Function;
    import org.qi4j.functional.Iterables;
    import org.qi4j.runtime.association.ManyAssociationModel;
    import org.qi4j.runtime.association.NamedAssociationModel;
    import org.qi4j.runtime.entity.EntityModel;
    import org.qi4j.spi.entity.EntityState;
    import org.qi4j.spi.entity.ManyAssociationState;
    import org.qi4j.spi.entity.NamedAssociationState;

    /**
     * Function based StateResolver.
     */
    public class FunctionStateResolver
        implements StateResolver
    {
        final Function<PropertyDescriptor, Object> propertyFunction;
        final Function<AssociationDescriptor, EntityReference> associationFunction;
        final Function<AssociationDescriptor, Iterable<EntityReference>> manyAssociationFunction;
        final Function<AssociationDescriptor, Map<String, EntityReference>> namedAssociationFunction;

        public FunctionStateResolver( Function<PropertyDescriptor, Object> propertyFunction,
                                      Function<AssociationDescriptor, EntityReference> associationFunction,
                                      Function<AssociationDescriptor, Iterable<EntityReference>> manyAssociationFunction,
                                      Function<AssociationDescriptor, Map<String, EntityReference>> namedAssociationFunction )
        {
            this.propertyFunction = propertyFunction;
            this.associationFunction = associationFunction;
            this.manyAssociationFunction = manyAssociationFunction;
            this.namedAssociationFunction = namedAssociationFunction;
        }

        @Override
        public Object getPropertyState( PropertyDescriptor propertyDescriptor )
        {
            return propertyFunction.map( propertyDescriptor );
        }

        @Override
        public EntityReference getAssociationState( AssociationDescriptor associationDescriptor )
        {
            return associationFunction.map( associationDescriptor );
        }

        @Override
        public List<EntityReference> getManyAssociationState( AssociationDescriptor associationDescriptor )
        {
            return Iterables.toList( manyAssociationFunction.map( associationDescriptor ) );
        }

        @Override
        public Map<String, EntityReference> getNamedAssociationState( AssociationDescriptor associationDescriptor )
        {
            return namedAssociationFunction.map( associationDescriptor );
        }

        public void populateState( EntityModel model, EntityState state )
        {
            for( PropertyDescriptor propDesc : model.state().properties() )
            {
                Object value = getPropertyState( propDesc );
                state.setPropertyValue( propDesc.qualifiedName(), value );
            }
            for( AssociationDescriptor assDesc : model.state().associations() )
            {
                EntityReference ref = getAssociationState( assDesc );
                state.setAssociationValue( assDesc.qualifiedName(), ref );
            }
            for( ManyAssociationModel manyAssDesc : model.state().manyAssociations() )
            {
                ManyAssociationState associationState = state.manyAssociationValueOf( manyAssDesc.qualifiedName() );
                // First clear existing ones
                for( EntityReference ref : associationState )
                {
                    associationState.remove( ref );
                }
                // then add the new ones.
                for( EntityReference ref : getManyAssociationState( manyAssDesc ) )
                {
                    associationState.add( 0, ref );
                }
            }
            for( NamedAssociationModel namedAssDesc : model.state().namedAssociations() )
            {
                NamedAssociationState associationState = state.namedAssociationValueOf( namedAssDesc.qualifiedName() );
                // First clear existing ones
                for( String name : associationState )
                {
                    associationState.remove( name );
                }
                // then add the new ones.
                for( Map.Entry<String, EntityReference> entry : getNamedAssociationState( namedAssDesc ).entrySet() )
                {
                    associationState.put( entry.getKey(), entry.getValue() );
                }
            }
        }
    }