import java.util.Map;
import java.util.function.Function;

public class Pairs<T> {

	public <V> void addMapEntries(Function<T, Map<String, V>> extractor) {
		add(extractor.andThen(Map::entrySet), Map.Entry::getKey, Map.Entry::getValue);
		// add(extractor.andThen((Map<String, V> map) -> map.entrySet()), Map.Entry::getKey, Map.Entry::getValue);
	}
 
	public <E> void add(Function<T, Iterable<E>> elementsExtractor, PairExtractor<E> pairExtractor) {
		add(elementsExtractor, pairExtractor::getName, pairExtractor::getValue);
	} 

	public <E, V> void add(Function<T, Iterable<E>> elementsExtractor, Function<E, String> nameExtractor,
			Function<E, V> valueExtractor) {
	}
	
	interface PairExtractor<E> {
		<N> N getName(E element);
		<V> V getValue(E element);
		static <T> PairExtractor<T> of(Function<T, ?> nameExtractor, Function<T, ?> valueExtractor) {
			return new PairExtractor<>() {

				@Override
				@SuppressWarnings("unchecked")
				public <N> N getName(T instance) {
					return (N) nameExtractor.apply(instance);
				}

				@Override
				@SuppressWarnings("unchecked")
				public <V> V getValue(T instance) {
					return (V) valueExtractor.apply(instance);
				}

			};
		}
	}

}