# JoinTablePolymorphismBuilder.java

    package org.codefilarete.stalactite.engine.configurer.polymorphism;

    import java.util.HashMap;
    import java.util.Map;
    import java.util.Set;

    import org.codefilarete.reflection.ReversibleAccessor;
    import org.codefilarete.reflection.ValueAccessPointMap;
    import org.codefilarete.reflection.ValueAccessPointSet;
    import org.codefilarete.stalactite.dsl.PolymorphismPolicy;
    import org.codefilarete.stalactite.dsl.PolymorphismPolicy.JoinTablePolymorphism;
    import org.codefilarete.stalactite.dsl.subentity.SubEntityMappingConfiguration;
    import org.codefilarete.stalactite.engine.configurer.AbstractIdentification;
    import org.codefilarete.stalactite.engine.configurer.builder.embeddable.EmbeddableMappingBuilder;
    import org.codefilarete.stalactite.engine.configurer.builder.embeddable.EmbeddableMapping;
    import org.codefilarete.stalactite.engine.configurer.NamingConfiguration;
    import org.codefilarete.stalactite.engine.configurer.builder.PersisterBuilderContext;
    import org.codefilarete.stalactite.engine.configurer.builder.IdentifierManagerStep;
    import org.codefilarete.stalactite.engine.configurer.builder.InheritanceMappingStep.Mapping;
    import org.codefilarete.stalactite.engine.configurer.builder.MainPersisterStep;
    import org.codefilarete.stalactite.engine.configurer.builder.PrimaryKeyPropagationStep;
    import org.codefilarete.stalactite.engine.runtime.AbstractPolymorphismPersister;
    import org.codefilarete.stalactite.engine.runtime.ConfiguredRelationalPersister;
    import org.codefilarete.stalactite.engine.runtime.SimpleRelationalEntityPersister;
    import org.codefilarete.stalactite.engine.runtime.jointable.JoinTablePolymorphismPersister;
    import org.codefilarete.stalactite.mapping.DefaultEntityMapping;
    import org.codefilarete.stalactite.sql.ConnectionConfiguration;
    import org.codefilarete.stalactite.sql.Dialect;
    import org.codefilarete.stalactite.sql.ddl.structure.Column;
    import org.codefilarete.stalactite.sql.ddl.structure.PrimaryKey;
    import org.codefilarete.stalactite.sql.ddl.structure.Table;
    import org.codefilarete.stalactite.sql.statement.binder.ColumnBinderRegistry;
    import org.codefilarete.tool.Reflections;
    import org.codefilarete.tool.collection.Arrays;
    import org.codefilarete.tool.exception.NotImplementedException;
    import org.codefilarete.tool.function.Converter;

    import static org.codefilarete.tool.Nullable.nullable;

    /**
     * @author Guillaume Mary
     */
    public class JoinTablePolymorphismBuilder<C, I, T extends Table<T>> extends AbstractPolymorphicPersisterBuilder<C, I, T> {

    	private final JoinTablePolymorphism<C> joinTablePolymorphism;
    	private final PrimaryKey<T, I> mainTablePrimaryKey;

    	public JoinTablePolymorphismBuilder(JoinTablePolymorphism<C> polymorphismPolicy,
    										AbstractIdentification<C, I> identification,
    										ConfiguredRelationalPersister<C, I> mainPersister,
    										ColumnBinderRegistry columnBinderRegistry,
    										NamingConfiguration namingConfiguration,
    										PersisterBuilderContext persisterBuilderContext) {
    		super(polymorphismPolicy, identification, mainPersister, columnBinderRegistry, namingConfiguration, persisterBuilderContext);
    		this.joinTablePolymorphism = polymorphismPolicy;
    		this.mainTablePrimaryKey = (PrimaryKey<T, I>) this.mainPersister.getMapping().getTargetTable().getPrimaryKey();
    	}

    	@Override
    	public AbstractPolymorphismPersister<C, I> build(Dialect dialect, ConnectionConfiguration connectionConfiguration) {
    		Map<Class<C>, ConfiguredRelationalPersister<C, I>> persisterPerSubclass = collectSubClassPersister(dialect, connectionConfiguration);

    		// Note that registering the cascades to sub-persisters must be done BEFORE the creation of the main persister to make it have all
    		// entities joins and let it build a consistent entity graph load; without it, we miss sub-relations when loading main entities
    		registerSubEntitiesRelations(persisterPerSubclass, dialect, connectionConfiguration);

    		JoinTablePolymorphismPersister<C, I> result = new JoinTablePolymorphismPersister<>(
    				mainPersister, persisterPerSubclass, connectionConfiguration.getConnectionProvider(),
    				dialect);

    		return result;
    	}

    	private <D extends C> Map<Class<D>, ConfiguredRelationalPersister<D, I>> collectSubClassPersister(Dialect dialect, ConnectionConfiguration connectionConfiguration) {
    		Map<Class<D>, ConfiguredRelationalPersister<D, I>> persisterPerSubclass = new HashMap<>();

    		for (SubEntityMappingConfiguration<D> subConfiguration : ((Set<SubEntityMappingConfiguration<D>>) (Set) joinTablePolymorphism.getSubClasses())) {
    			ConfiguredRelationalPersister<D, I> subclassPersister = buildSubclassPersister(dialect, connectionConfiguration, subConfiguration);
    			persisterPerSubclass.put(subConfiguration.getEntityType(), subclassPersister);
    		}
    		return persisterPerSubclass;
    	}

    	private <D, SUBT extends Table<SUBT>> ConfiguredRelationalPersister<D, I> buildSubclassPersister(Dialect dialect,
    																									 ConnectionConfiguration connectionConfiguration,
    																									 SubEntityMappingConfiguration<D> subConfiguration) {
    		// first we'll use table of columns defined in embedded override
    		// then the one defined by inheritance
    		// if both are null we'll create a new one
    		Table tableDefinedByInheritanceConfiguration = joinTablePolymorphism.giveTable(subConfiguration);
    		Table tableDefinedByColumnOverride = EmbeddableMappingBuilder.giveTargetTable(subConfiguration.getPropertiesMapping(), tableDefinedByInheritanceConfiguration);

    		SUBT subTable = (SUBT) nullable(tableDefinedByColumnOverride)
    				.elseSet(tableDefinedByInheritanceConfiguration)
    				.getOr(() -> new Table<>(namingConfiguration.getTableNamingStrategy().giveName(subConfiguration.getEntityType())));

    		EmbeddableMappingBuilder<D, SUBT> embeddableMappingBuilder = new EmbeddableMappingBuilder<>(subConfiguration.getPropertiesMapping(), subTable,
    				this.columnBinderRegistry, this.namingConfiguration.getColumnNamingStrategy(), this.namingConfiguration.getIndexNamingStrategy());
    		EmbeddableMapping<D, SUBT> embeddableMapping = embeddableMappingBuilder.build();
    		Map<ReversibleAccessor<D, Object>, Column<SUBT, Object>> subEntityPropertiesMapping = embeddableMapping.getMapping();
    		Map<ReversibleAccessor<D, Object>, Column<SUBT, Object>> subEntityReadonlyPropertiesMapping = embeddableMapping.getReadonlyMapping();
    		ValueAccessPointMap<D, Converter<Object, Object>> subEntityPropertiesConverters = embeddableMapping.getReadConverters();
    		ValueAccessPointMap<D, Converter<Object, Object>> subEntityPropertiesWriteConverters = embeddableMapping.getWriteConverters();
    		addPrimarykey(subTable);
    		addForeignKey(subTable);
    		DefaultEntityMapping<D, I, SUBT> entityMapping = MainPersisterStep.createEntityMapping(
    				false,
    				subTable,
    				subEntityPropertiesMapping,
    				subEntityReadonlyPropertiesMapping,
    				subEntityPropertiesConverters,
    				subEntityPropertiesWriteConverters,
    				new ValueAccessPointSet<>(),    // TODO: implement properties set by constructor feature in joined-tables polymorphism
    				(AbstractIdentification<D, I>) identification,
    				subConfiguration.getPropertiesMapping().getBeanType(),
    				null);

    		// NB: persisters are not registered into PersistenceContext because it may break implicit polymorphism principle (persisters are then
    		// available by PersistenceContext.getPersister(..)) and it is not sure that they are perfect ones (all their features should be tested)
    		return new SimpleRelationalEntityPersister<>(entityMapping, dialect, connectionConfiguration);
    	}

    	@Override
    	protected void assertSubPolymorphismIsSupported(PolymorphismPolicy<? extends C> subPolymorphismPolicy) {
    		// Everything else than joined-tables and single-table is not implemented (meaning table-per-class)
    		// Written as a negative condition to explicitly say what we support
    		if (!(subPolymorphismPolicy instanceof PolymorphismPolicy.JoinTablePolymorphism
    				|| subPolymorphismPolicy instanceof PolymorphismPolicy.SingleTablePolymorphism)) {
    			throw new NotImplementedException("Combining joined-tables polymorphism policy with " + Reflections.toString(subPolymorphismPolicy.getClass()));
    		}
    	}

    	private void addPrimarykey(Table table) {
    		PrimaryKeyPropagationStep.propagatePrimaryKey(this.mainTablePrimaryKey, Arrays.asSet(table));
    	}

    	private void addForeignKey(Table table) {
    		PrimaryKeyPropagationStep.applyForeignKeys(this.mainTablePrimaryKey, this.namingConfiguration.getForeignKeyNamingStrategy(), Arrays.asSet(table));
    	}
    }