# OneToManyRelationConfigurer.java

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

    import java.util.Collection;
    import java.util.Set;

    import org.codefilarete.stalactite.dsl.MappingConfigurationException;
    import org.codefilarete.stalactite.dsl.entity.EntityMappingConfiguration;
    import org.codefilarete.stalactite.dsl.naming.AssociationTableNamingStrategy;
    import org.codefilarete.stalactite.dsl.naming.ColumnNamingStrategy;
    import org.codefilarete.stalactite.dsl.naming.ForeignKeyNamingStrategy;
    import org.codefilarete.stalactite.dsl.naming.JoinColumnNamingStrategy;
    import org.codefilarete.stalactite.dsl.naming.TableNamingStrategy;
    import org.codefilarete.stalactite.dsl.property.CascadeOptions.RelationMode;
    import org.codefilarete.stalactite.engine.configurer.AbstractRelationConfigurer;
    import org.codefilarete.stalactite.engine.configurer.EntityMappingConfigurationWithTable;
    import org.codefilarete.stalactite.engine.configurer.builder.PersisterBuilderContext;
    import org.codefilarete.stalactite.engine.runtime.ConfiguredRelationalPersister;
    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.tool.StringAppender;
    import org.codefilarete.tool.collection.Arrays;
    import org.codefilarete.tool.collection.Iterables;

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

    /**
     * @param <SRC> type of input (left/source entities)
     * @param <TRGT> type of output (right/target entities)
     * @param <SRCID> identifier type of source entities
     * @param <TRGTID> identifier type of target entities
     * @author Guillaume Mary
     */
    public class OneToManyRelationConfigurer<SRC, SRCID, TRGT, TRGTID> extends AbstractRelationConfigurer<SRC, SRCID, TRGT, TRGTID> {

    	private final ForeignKeyNamingStrategy foreignKeyNamingStrategy;
    	private final JoinColumnNamingStrategy joinColumnNamingStrategy;
    	private final AssociationTableNamingStrategy associationTableNamingStrategy;
    	private final ColumnNamingStrategy indexColumnNamingStrategy;
    	private final PrimaryKey<?, SRCID> leftPrimaryKey;

    	public OneToManyRelationConfigurer(ConfiguredRelationalPersister<SRC, SRCID> sourcePersister,
    									   Dialect dialect,
    									   ConnectionConfiguration connectionConfiguration,
    									   TableNamingStrategy tableNamingStrategy,
    									   ForeignKeyNamingStrategy foreignKeyNamingStrategy,
    									   JoinColumnNamingStrategy joinColumnNamingStrategy,
    									   AssociationTableNamingStrategy associationTableNamingStrategy,
    									   ColumnNamingStrategy indexColumnNamingStrategy,
    									   PersisterBuilderContext currentBuilderContext) {
    		super(dialect, connectionConfiguration, sourcePersister, tableNamingStrategy, currentBuilderContext);
    		this.foreignKeyNamingStrategy = foreignKeyNamingStrategy;
    		this.joinColumnNamingStrategy = joinColumnNamingStrategy;
    		this.associationTableNamingStrategy = associationTableNamingStrategy;
    		this.indexColumnNamingStrategy = indexColumnNamingStrategy;

    		this.leftPrimaryKey = sourcePersister.getMapping().getTargetTable().getPrimaryKey();
    	}

    	public void configure(OneToManyRelation<SRC, TRGT, TRGTID, ? extends Collection<TRGT>> oneToManyRelation) {

    		RelationMode maintenanceMode = oneToManyRelation.getRelationMode();
    		// selection is always present (else configuration is nonsense !)
    		boolean orphanRemoval = maintenanceMode == RelationMode.ALL_ORPHAN_REMOVAL;
    		boolean writeAuthorized = maintenanceMode != RelationMode.READ_ONLY;
    		String indexingColumnName = oneToManyRelation.getIndexingColumnName();

    		OneToManyAssociationConfiguration<SRC, TRGT, SRCID, TRGTID, ?, ?> associationConfiguration = new OneToManyAssociationConfiguration<>(oneToManyRelation,
    				sourcePersister, leftPrimaryKey,
    				foreignKeyNamingStrategy, joinColumnNamingStrategy, indexColumnNamingStrategy, indexingColumnName,
    				orphanRemoval, writeAuthorized);
    		OneToManyConfigurerTemplate<SRC, TRGT, SRCID, TRGTID, ?, ?> configurer;
    		if (oneToManyRelation.isOwnedByReverseSide()) {
    			// case : reverse property is defined through one of the setter, getter or column on the reverse side
    			if (maintenanceMode == RelationMode.ASSOCIATION_ONLY) {
    				throw new MappingConfigurationException(RelationMode.ASSOCIATION_ONLY + " is only relevant with an association table");
    			}
    			configurer = new OneToManyWithMappedAssociationConfigurer<>(associationConfiguration, oneToManyRelation.isFetchSeparately());
    		} else {
    			configurer = new OneToManyWithAssociationTableConfigurer<>(associationConfiguration,
    					oneToManyRelation.isFetchSeparately(),
    					associationTableNamingStrategy,
    					dialect,
    					connectionConfiguration);
    		}

    		EntityMappingConfiguration<TRGT, TRGTID> targetMappingConfiguration = oneToManyRelation.getTargetMappingConfiguration();
    		if (currentBuilderContext.isCycling(targetMappingConfiguration)) {
    			// cycle detected
    			// we had a second phase load because cycle can hardly be supported by simply joining things together because at one time we will
    			// fall into infinite loop (think to SQL generation of a cycling graph ...)
    			Class<TRGT> targetEntityType = targetMappingConfiguration.getEntityType();
    			// adding the relation to an eventually already existing cycle configurer for the entity
    			OneToManyCycleConfigurer<TRGT> cycleSolver = (OneToManyCycleConfigurer<TRGT>)
    					Iterables.find(currentBuilderContext.getBuildLifeCycleListeners(), p -> p instanceof OneToManyCycleConfigurer && ((OneToManyCycleConfigurer<?>) p).getEntityType() == targetEntityType);
    			if (cycleSolver == null) {
    				cycleSolver = new OneToManyCycleConfigurer<>(targetEntityType);
    				currentBuilderContext.addBuildLifeCycleListener(cycleSolver);
    			}
    			String relationName = associationConfiguration.getAccessorDefinition().getName();
    			cycleSolver.addCycleSolver(relationName, configurer);
    		} else {
    			Table targetTable = determineTargetTable(oneToManyRelation);
    			ConfiguredRelationalPersister<TRGT, TRGTID> targetPersister = persisterBuilder.buildOrGiveExisting(new EntityMappingConfigurationWithTable<>(targetMappingConfiguration, targetTable));
    			configurer.configure(targetPersister);
    		}
    	}

    	private Table determineTargetTable(OneToManyRelation<SRC, TRGT, TRGTID, ?> oneToManyRelation) {
    		Table reverseTable = nullable(oneToManyRelation.getReverseColumn()).map(Column::getTable).get();
    		Table indexingTable = nullable(oneToManyRelation.getIndexingColumn()).map(Column::getTable).get();
    		Set<Table> availableTables = Arrays.asHashSet(oneToManyRelation.getTargetMappingConfiguration().getTable(), reverseTable, indexingTable);
    		availableTables.remove(null);
    		if (availableTables.size() > 1) {
    			class TableAppender extends StringAppender {
    				@Override
    				public StringAppender cat(Object o) {
    					if (o instanceof Table) {
    						return super.cat(((Table) o).getName());
    					} else {
    						return super.cat(o);
    					}
    				}
    			}
    			throw new MappingConfigurationException("Different tables used for configuring mapping : " + new TableAppender().ccat(availableTables, ", "));
    		}

    		// NB: even if no table is found in configuration, build(..) will create one
    		Table result = nullable(oneToManyRelation.getTargetMappingConfiguration().getTable()).elseSet(reverseTable).elseSet(indexingTable).get();
    		if (result == null) {
    			result = lookupTableInRegisteredPersisters(oneToManyRelation.getTargetMappingConfiguration().getEntityType());
    		}
    		return result;
    	}
    }