# IntermediaryRelationJoin.java

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

    import org.codefilarete.stalactite.engine.runtime.AssociationTable;
    import org.codefilarete.stalactite.sql.ddl.structure.Key;
    import org.codefilarete.stalactite.sql.ddl.structure.KeyMapping;
    import org.codefilarete.stalactite.sql.ddl.structure.Table;

    public class IntermediaryRelationJoin<
    		LEFTTABLE extends Table<LEFTTABLE>,
    		RIGHTTABLE extends Table<RIGHTTABLE>,
    		ASSOCIATIONTABLE extends AssociationTable<ASSOCIATIONTABLE, LEFTTABLE, RIGHTTABLE, LEFTJOINTYPE, RIGHTJOINTYPE>,
    		LEFTJOINTYPE,
    		RIGHTJOINTYPE
    		> implements RelationJoin {

    	private final KeyMapping<LEFTTABLE, ASSOCIATIONTABLE, LEFTJOINTYPE> leftKeyMapping;

    	private final KeyMapping<ASSOCIATIONTABLE, RIGHTTABLE, RIGHTJOINTYPE> rightKeyMapping;

    	/**
    	 * Constructor that takes an {@link AssociationTable} as argument.
    	 * A local type parameter {@code INTERMEDIARYTABLE} is introduced to satisfy both the {@code SELF}-referential
    	 * bound of {@link AssociationTable} and the {@code ASSOCIATIONTABLE} type parameter of this class.
    	 * The unchecked cast is safe because {@code INTERMEDIARYTABLE} is structurally the same table.
    	 */
    	public IntermediaryRelationJoin(ASSOCIATIONTABLE associationTable) {
    		this(associationTable.getOneSideKey(),
    				associationTable.getOneSideForeignKey(),
    				associationTable.getManySideForeignKey(),
    				associationTable.getManySideKey());
    	}

    	public IntermediaryRelationJoin(Key<LEFTTABLE, LEFTJOINTYPE> leftKey,
    									Key<ASSOCIATIONTABLE, LEFTJOINTYPE> leftAssociationKey,
    									Key<ASSOCIATIONTABLE, RIGHTJOINTYPE> rightAssociationKey,
    									Key<RIGHTTABLE, RIGHTJOINTYPE> rightKey) {
    		this.leftKeyMapping = new KeyMapping<>(leftKey, leftAssociationKey);
    		this.rightKeyMapping = new KeyMapping<>(rightAssociationKey, rightKey);
    	}

    	public Key<LEFTTABLE, LEFTJOINTYPE> getLeftKey() {
    		return leftKeyMapping.getSourceKey();
    	}

    	public Key<ASSOCIATIONTABLE, LEFTJOINTYPE> getLeftAssociationKey() {
    		return leftKeyMapping.getReferencedKey();
    	}

    	public Key<ASSOCIATIONTABLE, RIGHTJOINTYPE> getRightAssociationKey() {
    		return rightKeyMapping.getSourceKey();
    	}

    	public Key<RIGHTTABLE, RIGHTJOINTYPE> getRightKey() {
    		return rightKeyMapping.getReferencedKey();
    	}

    	public ASSOCIATIONTABLE getJoinTable() {
    		return leftKeyMapping.getReferencedKey().getTable();
    	}
    }