# KeyMapping.java

    package org.codefilarete.stalactite.sql.ddl.structure;

    import org.codefilarete.stalactite.query.api.Fromable;
    import org.codefilarete.stalactite.query.api.JoinLink;
    import org.codefilarete.tool.collection.KeepOrderMap;
    import org.codefilarete.tool.collection.KeepOrderSet;

    import static org.codefilarete.tool.collection.Iterables.pair;

    /**
     *
     * @param <LEFTTABLE> the left table of the join
     * @param <RIGHTTABLE> the right table of the join
     * @param <ID> the type of the join key
     * @author Guillaume Mary
     */
    public class KeyMapping<LEFTTABLE extends Fromable, RIGHTTABLE extends Fromable, ID> implements Key<LEFTTABLE, ID> {

    	private final Key<LEFTTABLE, ID> sourceKey;

    	private final Key<RIGHTTABLE, ID> referencedKey;

    	private final KeepOrderMap<JoinLink<LEFTTABLE, ?>, JoinLink<RIGHTTABLE, ?>> mapping;

    	public KeyMapping(Key<LEFTTABLE, ID> sourceKey, Key<RIGHTTABLE, ID> referencedKey) {
    		this.sourceKey = sourceKey;
    		this.referencedKey = referencedKey;
    		this.mapping = pair(sourceKey.getColumns(), referencedKey.getColumns(), KeepOrderMap::new);
    	}

    	public Key<LEFTTABLE, ID> getSourceKey() {
    		return sourceKey;
    	}

    	public Key<RIGHTTABLE, ID> getReferencedKey() {
    		return referencedKey;
    	}

    	public <J1 extends JoinLink<LEFTTABLE, ?>, J2 extends JoinLink<RIGHTTABLE, ?>> KeepOrderMap<J1, J2> getMapping() {
    		return (KeepOrderMap<J1, J2>) mapping;
    	}

    	public <J extends JoinLink<LEFTTABLE, ?>> KeepOrderSet<J> getSourceColumns() {
    		return (KeepOrderSet<J>) new KeepOrderSet<>(mapping.keySet());
    	}

    	public <J extends JoinLink<RIGHTTABLE, ?>> KeepOrderSet<J> getReferencedColumns() {
    		return (KeepOrderSet<J>) new KeepOrderSet<>(mapping.values());
    	}

    	@Override
    	public LEFTTABLE getTable() {
    		return sourceKey.getTable();
    	}

    	@Override
    	public <J extends JoinLink<LEFTTABLE, ?>> KeepOrderSet<J> getColumns() {
    		return getSourceColumns();
    	}

    	@Override
    	public boolean isComposed() {
    		return sourceKey.isComposed();
    	}
    }