# MapEntityStoreMixin.java

    /*
     * Copyright (c) 2009-2011, Rickard Öberg. All Rights Reserved.
     * Copyright (c) 2009-2013, Niclas Hedhman. All Rights Reserved.
     * Copyright (c) 2014, Paul Merlin. All Rights Reserved.
     *
     * 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.spi.entitystore.helpers;

    import java.io.IOException;
    import java.io.Reader;
    import java.io.Writer;
    import java.util.ArrayList;
    import java.util.HashMap;
    import java.util.LinkedHashMap;
    import java.util.List;
    import java.util.Map;
    import java.util.UUID;
    import org.json.JSONArray;
    import org.json.JSONException;
    import org.json.JSONObject;
    import org.json.JSONTokener;
    import org.json.JSONWriter;
    import org.qi4j.api.association.AssociationDescriptor;
    import org.qi4j.api.common.Optional;
    import org.qi4j.api.common.QualifiedName;
    import org.qi4j.api.entity.EntityDescriptor;
    import org.qi4j.api.entity.EntityReference;
    import org.qi4j.api.injection.scope.Service;
    import org.qi4j.api.injection.scope.Structure;
    import org.qi4j.api.injection.scope.This;
    import org.qi4j.api.injection.scope.Uses;
    import org.qi4j.api.property.PropertyDescriptor;
    import org.qi4j.api.service.ServiceDescriptor;
    import org.qi4j.api.service.qualifier.Tagged;
    import org.qi4j.api.structure.Application;
    import org.qi4j.api.type.ValueType;
    import org.qi4j.api.unitofwork.EntityTypeNotFoundException;
    import org.qi4j.api.usecase.Usecase;
    import org.qi4j.api.value.ValueSerialization;
    import org.qi4j.io.Input;
    import org.qi4j.io.Output;
    import org.qi4j.io.Receiver;
    import org.qi4j.io.Sender;
    import org.qi4j.spi.Qi4jSPI;
    import org.qi4j.spi.entity.EntityState;
    import org.qi4j.spi.entity.EntityStatus;
    import org.qi4j.spi.entitystore.DefaultEntityStoreUnitOfWork;
    import org.qi4j.spi.entitystore.EntityStore;
    import org.qi4j.spi.entitystore.EntityStoreException;
    import org.qi4j.spi.entitystore.EntityStoreSPI;
    import org.qi4j.spi.entitystore.EntityStoreUnitOfWork;
    import org.qi4j.spi.entitystore.ModuleEntityStoreUnitOfWork;
    import org.qi4j.spi.entitystore.StateCommitter;
    import org.qi4j.spi.module.ModelModule;
    import org.qi4j.spi.module.ModuleSpi;

    import static org.qi4j.functional.Iterables.first;
    import static org.qi4j.functional.Iterables.map;

    /**
     * Implementation of EntityStore that works with an implementation of MapEntityStore.
     *
     * <p>Implement {@link MapEntityStore} and add as mixin to the service using this mixin.</p>
     * <p>See {@link org.qi4j.entitystore.memory.MemoryMapEntityStoreMixin} for reference.</p>
     * <p>EntityStores based on this mixin gets support for the <b>Migration</b> extension.</p>
     * <p>MapEntityStore implementations will get their values as JSON.</p>
     */
    public class MapEntityStoreMixin
        implements EntityStore, EntityStoreSPI, StateStore, MapEntityStoreActivation
    {
        @This
        private MapEntityStore mapEntityStore;

        @This
        private EntityStoreSPI entityStoreSpi;

        @Structure
        private Qi4jSPI spi;

        @Structure
        private Application application;

        @Service
        @Tagged( ValueSerialization.Formats.JSON )
        private ValueSerialization valueSerialization;

        @Optional
        @Service
        private Migration migration;

        @Uses
        private ServiceDescriptor descriptor;

        protected String uuid;
        private int count;

        @Override
        public void activateMapEntityStore()
            throws Exception
        {
            uuid = UUID.randomUUID().toString() + "-";
        }

        // EntityStore
        @Override
        public EntityStoreUnitOfWork newUnitOfWork( Usecase usecaseMetaInfo, ModuleSpi module, long currentTime )
        {
            EntityStoreUnitOfWork storeUnitOfWork =
                new DefaultEntityStoreUnitOfWork( entityStoreSpi, newUnitOfWorkId(), usecaseMetaInfo, currentTime );
            storeUnitOfWork = new ModuleEntityStoreUnitOfWork( module, storeUnitOfWork );
            return storeUnitOfWork;
        }

        // EntityStoreSPI
        @Override
        public EntityState newEntityState( EntityStoreUnitOfWork unitOfWork,
                                           ModuleSpi module,
                                           EntityReference identity,
                                           EntityDescriptor entityDescriptor
        )
        {
            return new DefaultEntityState( unitOfWork.currentTime(), identity, entityDescriptor );
        }

        @Override
        public synchronized EntityState entityStateOf( EntityStoreUnitOfWork unitofwork,
                                                       ModuleSpi module,
                                                       EntityReference identity
        )
        {
            Reader in = mapEntityStore.get( identity );
            return readEntityState( module, in );
        }

        @Override
        public StateCommitter applyChanges( final EntityStoreUnitOfWork unitofwork, final Iterable<EntityState> state
        )
            throws EntityStoreException
        {
            return new StateCommitter()
            {
                @Override
                public void commit()
                {
                    try
                    {
                        mapEntityStore.applyChanges( new MapEntityStore.MapChanges()
                        {
                            @Override
                            public void visitMap( MapEntityStore.MapChanger changer )
                                throws IOException
                            {
                                for( EntityState entityState : state )
                                {
                                    DefaultEntityState state = (DefaultEntityState) entityState;
                                    if( state.status().equals( EntityStatus.NEW ) )
                                    {
                                        try (Writer writer = changer.newEntity( state.identity(), state.entityDescriptor() ))
                                        {
                                            writeEntityState( state, writer, unitofwork.identity(), unitofwork.currentTime() );
                                        }
                                    }
                                    else if( state.status().equals( EntityStatus.UPDATED ) )
                                    {
                                        try (Writer writer = changer.updateEntity( state.identity(), state.entityDescriptor() ))
                                        {
                                            writeEntityState( state, writer, unitofwork.identity(), unitofwork.currentTime() );
                                        }
                                    }
                                    else if( state.status().equals( EntityStatus.REMOVED ) )
                                    {
                                        changer.removeEntity( state.identity(), state.entityDescriptor() );
                                    }
                                }
                            }
                        } );
                    }
                    catch( IOException e )
                    {
                        throw new EntityStoreException( e );
                    }
                }

                @Override
                public void cancel()
                {
                }
            };
        }

        @Override
        public Input<EntityState, EntityStoreException> entityStates( final ModuleSpi module )
        {
            return new Input<EntityState, EntityStoreException>()
            {
                @Override
                public <ReceiverThrowableType extends Throwable> void transferTo( Output<? super EntityState, ReceiverThrowableType> output )
                    throws EntityStoreException, ReceiverThrowableType
                {
                    output.receiveFrom( new Sender<EntityState, EntityStoreException>()
                    {
                        @Override
                        public <ReceiverThrowableType extends Throwable> void sendTo( final Receiver<? super EntityState, ReceiverThrowableType> receiver )
                            throws ReceiverThrowableType, EntityStoreException
                        {
                            final List<EntityState> migrated = new ArrayList<>();
                            try
                            {
                                mapEntityStore.entityStates().transferTo( new Output<Reader, ReceiverThrowableType>()
                                {
                                    @Override
                                    public <SenderThrowableType extends Throwable> void receiveFrom( Sender<? extends Reader, SenderThrowableType> sender )
                                        throws ReceiverThrowableType, SenderThrowableType
                                    {
                                        sender.sendTo( new Receiver<Reader, ReceiverThrowableType>()
                                        {
                                            @Override
                                            public void receive( Reader item )
                                                throws ReceiverThrowableType
                                            {
                                                final EntityState entity = readEntityState( module, item );
                                                if( entity.status() == EntityStatus.UPDATED )
                                                {
                                                    migrated.add( entity );

                                                    // Synch back 100 at a time
                                                    if( migrated.size() > 100 )
                                                    {
                                                        try
                                                        {
                                                            synchMigratedEntities( migrated );
                                                        }
                                                        catch( IOException e )
                                                        {
                                                            throw new EntityStoreException( "Synchronization of Migrated Entities failed.", e );
                                                        }
                                                    }
                                                }
                                                receiver.receive( entity );
                                            }
                                        } );

                                        // Synch any remaining migrated entities
                                        if( !migrated.isEmpty() )
                                        {
                                            try
                                            {
                                                synchMigratedEntities( migrated );
                                            }
                                            catch( IOException e )
                                            {
                                                throw new EntityStoreException( "Synchronization of Migrated Entities failed.", e );
                                            }
                                        }
                                    }
                                } );
                            }
                            catch( IOException e )
                            {
                                throw new EntityStoreException( e );
                            }
                        }
                    } );
                }
            };
        }

        private void synchMigratedEntities( final List<EntityState> migratedEntities )
            throws IOException
        {
            mapEntityStore.applyChanges( new MapEntityStore.MapChanges()
            {
                @Override
                public void visitMap( MapEntityStore.MapChanger changer )
                    throws IOException
                {
                    for( EntityState migratedEntity : migratedEntities )
                    {
                        DefaultEntityState state = (DefaultEntityState) migratedEntity;
                        try (Writer writer = changer.updateEntity( state.identity(), state.entityDescriptor() ))
                        {
                            writeEntityState( state, writer, state.version(), state.lastModified() );
                        }
                    }
                }
            } );
            migratedEntities.clear();
        }

        protected String newUnitOfWorkId()
        {
            return uuid + Integer.toHexString( count++ );
        }

        protected void writeEntityState( DefaultEntityState state, Writer writer, String version, long lastModified )
            throws EntityStoreException
        {
            try
            {
                JSONWriter json = new JSONWriter( writer );
                JSONWriter properties = json.object().
                    key( JSONKeys.IDENTITY ).value( state.identity().identity() ).
                    key( JSONKeys.APPLICATION_VERSION ).value( application.version() ).
                    key( JSONKeys.TYPE ).value( first( state.entityDescriptor().types() ).getName() ).
                    key( JSONKeys.VERSION ).value( version ).
                    key( JSONKeys.MODIFIED ).value( lastModified ).
                    key( JSONKeys.PROPERTIES ).object();
                EntityDescriptor entityType = state.entityDescriptor();
                for( PropertyDescriptor persistentProperty : entityType.state().properties() )
                {
                    Object value = state.properties().get( persistentProperty.qualifiedName() );
                    json.key( persistentProperty.qualifiedName().name() );
                    if( value == null || ValueType.isPrimitiveValue( value ) )
                    {
                        json.value( value );
                    }
                    else
                    {
                        String serialized = valueSerialization.serialize( value );
                        if( serialized.startsWith( "{" ) )
                        {
                            json.value( new JSONObject( serialized ) );
                        }
                        else if( serialized.startsWith( "[" ) )
                        {
                            json.value( new JSONArray( serialized ) );
                        }
                        else
                        {
                            json.value( serialized );
                        }
                    }
                }

                JSONWriter associations = properties.endObject().key( JSONKeys.ASSOCIATIONS ).object();
                for( Map.Entry<QualifiedName, EntityReference> stateNameEntityReferenceEntry : state.associations()
                    .entrySet() )
                {
                    EntityReference value = stateNameEntityReferenceEntry.getValue();
                    associations.key( stateNameEntityReferenceEntry.getKey().name() ).
                        value( value != null ? value.identity() : null );
                }

                JSONWriter manyAssociations = associations.endObject().key( JSONKeys.MANY_ASSOCIATIONS ).object();
                for( Map.Entry<QualifiedName, List<EntityReference>> stateNameListEntry : state.manyAssociations()
                    .entrySet() )
                {
                    JSONWriter assocs = manyAssociations.key( stateNameListEntry.getKey().name() ).array();
                    for( EntityReference entityReference : stateNameListEntry.getValue() )
                    {
                        assocs.value( entityReference.identity() );
                    }
                    assocs.endArray();
                }

                JSONWriter namedAssociations = manyAssociations.endObject().key( JSONKeys.NAMED_ASSOCIATIONS ).object();
                for( Map.Entry<QualifiedName, Map<String, EntityReference>> stateNameMapEntry : state.namedAssociations()
                    .entrySet() )
                {
                    JSONWriter assocs = namedAssociations.key( stateNameMapEntry.getKey().name() ).object();
                    for( Map.Entry<String, EntityReference> namedRef : stateNameMapEntry.getValue().entrySet() )
                    {
                        assocs.key( namedRef.getKey() ).value( namedRef.getValue().identity() );
                    }
                    assocs.endObject();
                }
                namedAssociations.endObject().endObject();
            }
            catch( JSONException e )
            {
                throw new EntityStoreException( "Could not store EntityState", e );
            }
        }

        protected EntityState readEntityState( ModuleSpi module, Reader entityState )
            throws EntityStoreException
        {
            try
            {
                JSONObject jsonObject = new JSONObject( new JSONTokener( entityState ) );
                EntityStatus status = EntityStatus.LOADED;

                String version = jsonObject.getString( JSONKeys.VERSION );
                long modified = jsonObject.getLong( JSONKeys.MODIFIED );
                String identity = jsonObject.getString( JSONKeys.IDENTITY );

                // Check if version is correct
                String currentAppVersion = jsonObject.optString( JSONKeys.APPLICATION_VERSION, "0.0" );
                if( !currentAppVersion.equals( application.version() ) )
                {
                    if( migration != null )
                    {
                        migration.migrate( jsonObject, application.version(), this );
                    }
                    else
                    {
                        // Do nothing - set version to be correct
                        jsonObject.put( JSONKeys.APPLICATION_VERSION, application.version() );
                    }
                    // State changed
                    status = EntityStatus.UPDATED;
                }

                String type = jsonObject.getString( JSONKeys.TYPE );

                EntityDescriptor entityDescriptor = module.entityDescriptor( type );
                if( entityDescriptor == null )
                {
                    throw new EntityTypeNotFoundException( type,
                                                           module.name(),
                                                           map( ModelModule.toStringFunction,
                                                                module.findVisibleEntityTypes()
                                                           ) );
                }

                Map<QualifiedName, Object> properties = new HashMap<>();
                JSONObject props = jsonObject.getJSONObject( JSONKeys.PROPERTIES );
                for( PropertyDescriptor propertyDescriptor : entityDescriptor.state().properties() )
                {
                    Object jsonValue;
                    try
                    {
                        jsonValue = props.get( propertyDescriptor.qualifiedName().name() );
                    }
                    catch( JSONException e )
                    {
                        // Value not found, default it
                        Object initialValue = propertyDescriptor.initialValue( module );
                        properties.put( propertyDescriptor.qualifiedName(), initialValue );
                        status = EntityStatus.UPDATED;
                        continue;
                    }
                    if( JSONObject.NULL.equals( jsonValue ) )
                    {
                        properties.put( propertyDescriptor.qualifiedName(), null );
                    }
                    else
                    {
                        Object value = valueSerialization.deserialize( propertyDescriptor.valueType(), jsonValue.toString() );
                        properties.put( propertyDescriptor.qualifiedName(), value );
                    }
                }

                Map<QualifiedName, EntityReference> associations = new HashMap<>();
                JSONObject assocs = jsonObject.getJSONObject( JSONKeys.ASSOCIATIONS );
                for( AssociationDescriptor associationType : entityDescriptor.state().associations() )
                {
                    try
                    {
                        Object jsonValue = assocs.get( associationType.qualifiedName().name() );
                        EntityReference value = jsonValue == JSONObject.NULL
                                                ? null
                                                : EntityReference.parseEntityReference( (String) jsonValue );
                        associations.put( associationType.qualifiedName(), value );
                    }
                    catch( JSONException e )
                    {
                        // Association not found, default it to null
                        associations.put( associationType.qualifiedName(), null );
                        status = EntityStatus.UPDATED;
                    }
                }

                JSONObject manyAssocs = jsonObject.getJSONObject( JSONKeys.MANY_ASSOCIATIONS );
                Map<QualifiedName, List<EntityReference>> manyAssociations = new HashMap<>();
                for( AssociationDescriptor manyAssociationType : entityDescriptor.state().manyAssociations() )
                {
                    List<EntityReference> references = new ArrayList<>();
                    try
                    {
                        JSONArray jsonValues = manyAssocs.getJSONArray( manyAssociationType.qualifiedName().name() );
                        for( int i = 0; i < jsonValues.length(); i++ )
                        {
                            Object jsonValue = jsonValues.getString( i );
                            EntityReference value = jsonValue == JSONObject.NULL
                                                    ? null
                                                    : EntityReference.parseEntityReference( (String) jsonValue );
                            references.add( value );
                        }
                        manyAssociations.put( manyAssociationType.qualifiedName(), references );
                    }
                    catch( JSONException e )
                    {
                        // ManyAssociation not found, default to empty one
                        manyAssociations.put( manyAssociationType.qualifiedName(), references );
                    }
                }

                JSONObject namedAssocs = jsonObject.getJSONObject( JSONKeys.NAMED_ASSOCIATIONS );
                Map<QualifiedName, Map<String, EntityReference>> namedAssociations = new HashMap<>();
                for( AssociationDescriptor namedAssociationType : entityDescriptor.state().namedAssociations() )
                {
                    Map<String, EntityReference> references = new LinkedHashMap<>();
                    try
                    {
                        JSONObject jsonValues = namedAssocs.getJSONObject( namedAssociationType.qualifiedName().name() );
                        JSONArray names = jsonValues.names();
                        if( names != null )
                        {
                            for( int idx = 0; idx < names.length(); idx++ )
                            {
                                String name = names.getString( idx );
                                Object value = jsonValues.get( name );
                                EntityReference ref = value == JSONObject.NULL
                                                      ? null
                                                      : EntityReference.parseEntityReference( (String) value );
                                references.put( name, ref );
                            }
                        }
                        namedAssociations.put( namedAssociationType.qualifiedName(), references );
                    }
                    catch( JSONException e )
                    {
                        // NamedAssociation not found, default to empty one
                        namedAssociations.put( namedAssociationType.qualifiedName(), references );
                    }
                }

                return new DefaultEntityState( version,
                                               modified,
                                               EntityReference.parseEntityReference( identity ),
                                               status,
                                               entityDescriptor,
                                               properties,
                                               associations,
                                               manyAssociations,
                                               namedAssociations
                );
            }
            catch( JSONException e )
            {
                throw new EntityStoreException( e );
            }
        }

        @Override
        public JSONObject jsonStateOf( String id )
            throws IOException
        {
            JSONObject jsonObject;
            try (Reader reader = mapEntityStore.get( EntityReference.parseEntityReference( id ) ))
            {
                jsonObject = new JSONObject( new JSONTokener( reader ) );
            }
            catch( JSONException e )
            {
                throw new IOException( e );
            }
            return jsonObject;
        }
    }