# OneToManyRelation.java

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

    import javax.annotation.Nullable;
    import java.util.Collection;
    import java.util.Map;
    import java.util.function.BooleanSupplier;
    import java.util.function.Supplier;

    import org.codefilarete.reflection.Accessor;
    import org.codefilarete.reflection.AccessorChain;
    import org.codefilarete.reflection.AccessorChain.ValueInitializerOnNullValue;
    import org.codefilarete.reflection.AccessorDefinition;
    import org.codefilarete.reflection.AccessorDefinitionDefiner;
    import org.codefilarete.reflection.Accessors;
    import org.codefilarete.reflection.Mutator;
    import org.codefilarete.reflection.ReversibleAccessor;
    import org.codefilarete.reflection.ValueAccessPoint;
    import org.codefilarete.reflection.ValueAccessPointMap;
    import org.codefilarete.stalactite.dsl.PolymorphismPolicy;
    import org.codefilarete.stalactite.dsl.entity.EntityMappingConfiguration;
    import org.codefilarete.stalactite.dsl.entity.EntityMappingConfigurationProvider;
    import org.codefilarete.stalactite.dsl.property.CascadeOptions.RelationMode;
    import org.codefilarete.stalactite.sql.ddl.structure.Column;
    import org.codefilarete.stalactite.sql.ddl.structure.Table;
    import org.codefilarete.tool.Reflections;
    import org.danekja.java.util.function.serializable.SerializableBiConsumer;
    import org.danekja.java.util.function.serializable.SerializableFunction;

    /**
     *
     * @param <SRC> the "one" type
     * @param <TRGT> the "many" type
     * @param <TRGTID> identifier type of TRGT
     * @param <S> the "many" collection type
     */
    public class OneToManyRelation<SRC, TRGT, TRGTID, S extends Collection<TRGT>> {

    	/** The method that gives the "many" entities from the "one" entity */
    	private final ReversibleAccessor<SRC, S> collectionAccessor;

    	/** Indicator that says if source persister has table-per-class polymorphism */
    	private final BooleanSupplier sourceTablePerClassPolymorphic;

    	/** Configuration used for "many" side beans persistence */
    	private final EntityMappingConfigurationProvider<TRGT, TRGTID> targetMappingConfiguration;

    	private final MappedByConfiguration<TRGT, SRC> mappedByConfiguration;

    	/**
    	 * Source setter on target for bidirectionality (no consequence on database mapping).
    	 * Useful only for cases of association table because this case doesn't set any reverse information hence such setter can't be deduced.
    	 */
    	@Nullable
    	private SerializableBiConsumer<TRGT, SRC> reverseLink;

    	/** Default relation mode is {@link RelationMode#ALL} */
    	private RelationMode relationMode = RelationMode.ALL;
    	/** Optional provider of collection instance to be used if collection value is null */
    	@Nullable
    	private Supplier<S> collectionFactory;

    	/**
    	 * Indicates that relation must be loaded in same main query (through join) or in some separate query
    	 */
    	private boolean fetchSeparately;

    	@Nullable
    	private Column<?, Integer> indexingColumn;

    	@Nullable
    	private String indexingColumnName;

    	private boolean ordered = false;

    	/**
    	 * Constructor with lazy configuration provider. To be used when target configuration is not defined while source configuration is defined, for
    	 * instance on cycling configuration.
    	 *
    	 * @param collectionAccessor provider of the property to be persisted
    	 * @param sourceTablePerClassPolymorphic must return true if source persister has table-per-class polymorphism
    	 * @param targetMappingConfiguration must return persistence configuration of entities stored in the target collection
    	 */
    	public OneToManyRelation(ReversibleAccessor<SRC, S> collectionAccessor,
    							 BooleanSupplier sourceTablePerClassPolymorphic,
    							 EntityMappingConfigurationProvider<? super TRGT, TRGTID> targetMappingConfiguration) {
    		this.collectionAccessor = collectionAccessor;
    		this.sourceTablePerClassPolymorphic = sourceTablePerClassPolymorphic;
    		this.targetMappingConfiguration = (EntityMappingConfigurationProvider<TRGT, TRGTID>) targetMappingConfiguration;
    		this.mappedByConfiguration = new MappedByConfiguration<>();
    	}

    	private OneToManyRelation(ReversibleAccessor<SRC, S> collectionAccessor,
    							  BooleanSupplier sourceTablePerClassPolymorphic,
    							  EntityMappingConfigurationProvider<? super TRGT, TRGTID> targetMappingConfiguration,
    							  MappedByConfiguration<TRGT, ?> mappedByConfiguration) {
    		this.collectionAccessor = collectionAccessor;
    		this.sourceTablePerClassPolymorphic = sourceTablePerClassPolymorphic;
    		this.targetMappingConfiguration = (EntityMappingConfigurationProvider<TRGT, TRGTID>) targetMappingConfiguration;
    		// Note that this cast is wrong, but left for simplicity: this constructor is used for embedded one-to-many relation, which means that the SRC
    		// type is the one that embed another one which contains the relation. In such configuration, the relation actually points to the embeddable
    		// type, not the one that embeds the relation. This the mappedBy(..) config does the same: it point to the embeddable type, not the SRC type.
    		// But fixing it has a lot of impacts due to the necessity to replace MappedByConfiguration "SRC" type by a generic <?> one with has its own
    		// complexity. I consider all these impacts doesn't worth it and I prefer to force this cast, even wrong.
    		this.mappedByConfiguration = (MappedByConfiguration<TRGT, SRC>) mappedByConfiguration;
    	}

    	public ReversibleAccessor<SRC, S> getCollectionAccessor() {
    		return collectionAccessor;
    	}

    	public boolean isSourceTablePerClassPolymorphic() {
    		return sourceTablePerClassPolymorphic.getAsBoolean();
    	}

    	/** @return the configuration used for "many" side beans persistence */
    	public EntityMappingConfiguration<TRGT, TRGTID> getTargetMappingConfiguration() {
    		return targetMappingConfiguration.getConfiguration();
    	}

    	public boolean isTargetTablePerClassPolymorphic() {
    		return getTargetMappingConfiguration().getPolymorphismPolicy() instanceof PolymorphismPolicy.TablePerClassPolymorphism;
    	}

    	public void setReverseGetter(SerializableFunction<TRGT, ? super SRC> reverseGetter) {
    		this.mappedByConfiguration.setReverseGetter((SerializableFunction<TRGT, SRC>) reverseGetter);
    	}

    	public void setReverseSetter(SerializableBiConsumer<TRGT, ? super SRC> reverseSetter) {
    		this.mappedByConfiguration.setReverseSetter((SerializableBiConsumer<TRGT, SRC>) reverseSetter);
    	}

    	@Nullable
    	public Mutator<TRGT, SRC> giveReverseSetter() {
    		return this.mappedByConfiguration.giveReverseSetter();
    	}

    	@Nullable
    	public <O> Column<Table<?>, O> getReverseColumn() {
    		return (Column<Table<?>, O>) this.mappedByConfiguration.getReverseColumn();
    	}

    	public void setReverseColumn(Column<?, ?> reverseColumn) {
    		this.mappedByConfiguration.setReverseColumn(reverseColumn);
    	}

    	@Nullable
    	public String getReverseColumnName() {
    		return this.mappedByConfiguration.getReverseColumnName();
    	}

    	public void setReverseColumn(@Nullable String reverseColumnName) {
    		this.mappedByConfiguration.setReverseColumnName(reverseColumnName);
    	}

    	@Nullable
    	public String getAssociationTableName() {
    		return this.mappedByConfiguration.getAssociationTableName();
    	}

    	public void setAssociationTableName(@Nullable String tableName) {
    		this.mappedByConfiguration.setAssociationTableName(tableName);
    	}

    	@Nullable
    	public String getSourceJoinColumnName() {
    		return this.mappedByConfiguration.getSourceJoinColumnName();
    	}

    	public void setSourceJoinColumnName(@Nullable String sourceJoinColumnName) {
    		this.mappedByConfiguration.setSourceJoinColumnName(sourceJoinColumnName);
    	}

    	@Nullable
    	public String getTargetJoinColumnName() {
    		return this.mappedByConfiguration.getTargetJoinColumnName();
    	}

    	public void setTargetJoinColumnName(@Nullable String targetJoinColumnName) {
    		this.mappedByConfiguration.setTargetJoinColumnName(targetJoinColumnName);
    	}

    	public Boolean isReverseAsMandatory() {
    		return this.mappedByConfiguration.isMandatory();
    	}

    	public void setReverseAsMandatory(boolean mandatory) {
    		this.mappedByConfiguration.setMandatory(mandatory);
    	}

    	public ValueAccessPointMap<SRC, Column<Table<?>, Object>> getForeignKeyColumnMapping() {
    		return this.mappedByConfiguration.getForeignKeyColumnMapping();
    	}

    	public ValueAccessPointMap<SRC, String> getForeignKeyNameMapping() {
    		return this.mappedByConfiguration.getForeignKeyNameMapping();
    	}

    	@Nullable
    	public SerializableBiConsumer<TRGT, SRC> getReverseLink() {
    		return reverseLink;
    	}

    	public void setReverseLink(SerializableBiConsumer<TRGT, SRC> reverseLink) {
    		this.reverseLink = reverseLink;
    	}

    	public RelationMode getRelationMode() {
    		return relationMode;
    	}

    	public void setRelationMode(RelationMode relationMode) {
    		this.relationMode = relationMode;
    	}

    	/**
    	 * Indicates if relation is owned by target entities table
    	 * @return true if one of {@link #giveReverseSetter()}, {@link #getReverseColumn()} is not null
    	 */
    	public boolean isOwnedByReverseSide() {
    		return this.mappedByConfiguration.isNotEmpty();
    	}

    	@Nullable
    	public Supplier<S> getCollectionFactory() {
    		return collectionFactory;
    	}

    	public void setCollectionFactory(Supplier<S> collectionFactory) {
    		this.collectionFactory = collectionFactory;
    	}

    	public boolean isFetchSeparately() {
    		return fetchSeparately;
    	}

    	public void setFetchSeparately(boolean fetchSeparately) {
    		this.fetchSeparately = fetchSeparately;
    	}

    	public void fetchSeparately() {
    		setFetchSeparately(true);
    	}

    	public void setIndexingColumn(@Nullable Column<?, Integer> indexingColumn) {
    		ordered();
    		this.indexingColumn = indexingColumn;
    	}

    	@Nullable
    	public <T extends Table<T>> Column<T, Integer> getIndexingColumn() {
    		return (Column<T, Integer>) indexingColumn;
    	}

    	public void setIndexingColumnName(String columnName) {
    		ordered();
    		this.indexingColumnName = columnName;
    	}

    	@Nullable
    	public String getIndexingColumnName() {
    		return indexingColumnName;
    	}

    	public boolean isOrdered() {
    		return this.ordered;
    	}

    	public void setOrdered(boolean ordered) {
    		this.ordered = ordered;
    	}

    	public void ordered() {
    		this.ordered = true;
    	}

    	/**
    	 * Clones this object to make one with the given accessor as prefix of current one.
    	 * Made to "slide" current instance with an accessor prefix. Used for embeddable objects with relation to make the relation being accessible
    	 * from the "root" entity.
    	 *
    	 * @param accessor the prefix of the clone to be created
    	 * @param embeddedType the concrete type of the embeddable bean, because accessor may provide an abstraction
    	 * @return a clones of this instance prefixed with the given accessor
    	 * @param <C> the root entity type that owns the embeddable which has this relation
    	 */
    	public <C> OneToManyRelation<C, TRGT, TRGTID, S> embedInto(Accessor<C, SRC> accessor, Class<SRC> embeddedType) {
    		AccessorChain<C, S> shiftedTargetProvider = new AccessorChain<>(accessor, collectionAccessor);
    		shiftedTargetProvider.setNullValueHandler(new ValueInitializerOnNullValue() {
    			@Override
    			protected <T> T newInstance(Accessor<?, T> segmentAccessor, Class<T> valueType) {
    				if (segmentAccessor == accessor) {
    					return (T) Reflections.newInstance(embeddedType);
    				} else if (segmentAccessor == collectionAccessor){
    					if (collectionFactory != null) {
    						return (T) collectionFactory.get();
    					} else {
    						return super.newInstance(segmentAccessor, valueType);
    					}
    				} else {
    					return super.newInstance(segmentAccessor, valueType);
    				}
    			}
    		});
    		MappedByConfiguration<TRGT, C> slidedMappedByConfiguration = this.mappedByConfiguration.embedInto(accessor);

    		OneToManyRelation<C, TRGT, TRGTID, S> result = new OneToManyRelation<>(shiftedTargetProvider,
    				this::isSourceTablePerClassPolymorphic,
    				this.targetMappingConfiguration,
    				slidedMappedByConfiguration);
    		result.setRelationMode(this.getRelationMode());
    		result.setFetchSeparately(this.isFetchSeparately());
    		result.setIndexingColumnName(this.getIndexingColumnName());
    		result.setOrdered(this.isOrdered());
    		result.setCollectionFactory(this.getCollectionFactory());
    		return result;
    	}

    	private static class MappedByConfiguration<TRGT, SRC> {

    		/** The method that gets the "one" entity from the "many" entities, may be null */
    		protected ReversibleAccessor<TRGT, SRC> reverseGetter;

    		/** The method that sets the "one" entity onto the "many" entities, may be null */
    		protected Mutator<TRGT, SRC> reverseSetter;

    		/**
    		 * The column that stores relation, may be null.
    		 * Its type is undetermined (not forced at SRC) because it can only be a reference, such as an id.
    		 */
    		@Nullable
    		protected Column<Table<?>, Object> reverseColumn;

    		@Nullable
    		protected String reverseColumnName;

    		@Nullable
    		protected String associationTableName;

    		@Nullable
    		protected String sourceJoinColumnName;

    		@Nullable
    		protected String targetJoinColumnName;

    		private Boolean mandatory;

    		protected final ValueAccessPointMap<SRC, Column<Table<?>, Object>> foreignKeyColumnMapping = new ValueAccessPointMap<>();

    		protected final ValueAccessPointMap<SRC, String> foreignKeyNameMapping = new ValueAccessPointMap<>();

    		/**
    		 * Clones this object to create a new one with the given accessor as prefix of current one.
    		 * Made to shift the current instance with an accessor prefix. Used for embeddable objects with relation to make the relation being accessible
    		 * from the "root" entity.
    		 *
    		 * @param accessor the prefix of the clone to be created
    		 * @return a clone of this instance prefixed with the given accessor
    		 * @param <C> the root entity type that owns the embeddable which has this relation
    		 */
    		<C> MappedByConfiguration<TRGT, C> embedInto(Accessor<C, SRC> accessor) {
    			return new ShiftedMappedByConfiguration<>(accessor, this);
    		}

    		public void setReverseGetter(SerializableFunction<TRGT, SRC> reverseGetter) {
    			this.reverseGetter = Accessors.accessor(reverseGetter);
    		}

    		public void setReverseSetter(SerializableBiConsumer<TRGT, SRC> reverseSetter) {
    			this.reverseSetter = Accessors.mutator(reverseSetter);
    		}

    		public Mutator<TRGT, SRC> giveReverseSetter() {
    			if (this.reverseGetter != null) {
    				return this.reverseGetter.toMutator();
    			} else if (this.reverseSetter != null) {
    				return this.reverseSetter;
    			} else {
    				return null;
    			}
    		}

    		@Nullable
    		public String getReverseColumnName() {
    			return reverseColumnName;
    		}

    		public void setReverseColumnName(@Nullable String reverseColumnName) {
    			this.reverseColumnName = reverseColumnName;
    		}

    		@Nullable
    		public String getAssociationTableName() {
    			return associationTableName;
    		}

    		public void setAssociationTableName(@Nullable String associationTableName) {
    			this.associationTableName = associationTableName;
    		}

    		@Nullable
    		public String getSourceJoinColumnName() {
    			return sourceJoinColumnName;
    		}

    		public void setSourceJoinColumnName(@Nullable String sourceJoinColumnName) {
    			this.sourceJoinColumnName = sourceJoinColumnName;
    		}

    		@Nullable
    		public String getTargetJoinColumnName() {
    			return targetJoinColumnName;
    		}

    		public void setTargetJoinColumnName(@Nullable String targetJoinColumnName) {
    			this.targetJoinColumnName = targetJoinColumnName;
    		}

    		@Nullable
    		public Column<Table<?>, ?> getReverseColumn() {
    			return reverseColumn;
    		}

    		public void setReverseColumn(@Nullable Column<?, ?> reverseColumn) {
    			this.reverseColumn = (Column<Table<?>, Object>) reverseColumn;
    		}

    		public ValueAccessPointMap<SRC, Column<Table<?>, Object>> getForeignKeyColumnMapping() {
    			return foreignKeyColumnMapping;
    		}

    		public ValueAccessPointMap<SRC, String> getForeignKeyNameMapping() {
    			return foreignKeyNameMapping;
    		}

    		public Boolean isMandatory() {
    			return mandatory;
    		}

    		public void setMandatory(boolean mandatory) {
    			this.mandatory = mandatory;
    		}

    		public boolean isNotEmpty() {
    			return reverseSetter != null || reverseGetter != null || reverseColumn != null || reverseColumnName != null
    					|| !foreignKeyColumnMapping.isEmpty() || !foreignKeyNameMapping.isEmpty();
    		}
    	}

    	private static class ShiftedMappedByConfiguration<C, TRGT, SRC> extends MappedByConfiguration<TRGT, C> {

    		private final Mutator<TRGT, C> effectiveReverseMutator;

    		public ShiftedMappedByConfiguration(Accessor<C, SRC> accessor, MappedByConfiguration<TRGT, SRC> mappedByConfiguration) {
    			this.reverseColumn = mappedByConfiguration.reverseColumn;
    			this.reverseColumnName = mappedByConfiguration.reverseColumnName;
    			this.foreignKeyColumnMapping.putAll((Map<? extends ValueAccessPoint<C>, ? extends Column<Table<?>, Object>>) mappedByConfiguration.foreignKeyColumnMapping);
    			this.foreignKeyNameMapping.putAll((Map<? extends ValueAccessPoint<C>, ? extends String>) mappedByConfiguration.foreignKeyNameMapping);
    			// Note that we don't set this.reverseGetter nor this.reverseSetter because it raises generics problem, and we can afford not to store them.

    			// Creates shifted mutator when reverse accessor is present
    			if (mappedByConfiguration.reverseGetter != null || mappedByConfiguration.reverseSetter != null) {
    				Mutator<TRGT, SRC> localReverseSetter;
    				AccessorDefinition reverseDefinition;
    				if (mappedByConfiguration.reverseGetter != null) {
    					localReverseSetter = mappedByConfiguration.reverseGetter.toMutator();
    					reverseDefinition = AccessorDefinition.giveDefinition(mappedByConfiguration.reverseGetter);
    				} else {
    					localReverseSetter = mappedByConfiguration.reverseSetter;
    					reverseDefinition = AccessorDefinition.giveDefinition(mappedByConfiguration.reverseSetter);
    				}
    				AccessorDefinition accessorDefinition = AccessorDefinition.giveDefinition(accessor);
    				this.effectiveReverseMutator = new ShiftedMutator<>(
    						accessor,
    						new AccessorDefinition(accessorDefinition.getDeclaringClass(), accessorDefinition.getName() + "." + reverseDefinition.getName(), reverseDefinition.getMemberType()),
    						localReverseSetter);
    			} else {
    				this.effectiveReverseMutator = null;
    			}
    		}

    		@Override
    		public Mutator<TRGT, C> giveReverseSetter() {
    			return effectiveReverseMutator;
    		}

    		public boolean isNotEmpty() {
    			return effectiveReverseMutator != null || super.isNotEmpty();
    		}

    		private class ShiftedMutator<C> implements Mutator<TRGT, C>, AccessorDefinitionDefiner<TRGT> {
    			private final Accessor<C, SRC> accessor;
    			private final AccessorDefinition accessorDefinition;
    			private final Mutator<TRGT, SRC> reverseSetter;

    			public ShiftedMutator(Accessor<C, SRC> accessor, AccessorDefinition accessorDefinition, Mutator<TRGT, SRC> reverseSetter) {
    				this.accessor = accessor;
    				this.accessorDefinition = accessorDefinition;
    				this.reverseSetter = reverseSetter;
    			}

    			@Override
    			public void set(TRGT trgt, C c) {
    				SRC src = accessor.get(c);
    				reverseSetter.set(trgt, src);
    			}

    			@Override
    			public AccessorDefinition asAccessorDefinition() {
    				return accessorDefinition;
    			}
    		}
    	}
    }