package bjc.utils.funcutils;

import java.util.function.Consumer;
import java.util.function.Function;

import bjc.utils.funcdata.FunctionalList;
import bjc.utils.funcdata.IList;

/**
 * Implements a single group partitioning pass on a list
 *
 * @author ben
 *
 * @param <E>
 *                The type of element in the list being partitioned
 */
final class GroupPartIteration<E> implements Consumer<E> {
	private final IList<IList<E>> returnedList;

	public IList<E>		currentPartition;
	private final IList<E>	rejectedItems;

	private int		numberInCurrentPartition;
	private final int	numberPerPartition;

	private final Function<E, Integer> elementCounter;

	public GroupPartIteration(final IList<IList<E>> returned, final IList<E> rejects, final int nPerPart,
			final Function<E, Integer> eleCount) {
		this.returnedList = returned;
		this.rejectedItems = rejects;
		this.numberPerPartition = nPerPart;
		this.elementCounter = eleCount;

		this.currentPartition = new FunctionalList<>();
		this.numberInCurrentPartition = 0;
	}

	@Override
	public void accept(final E value) {
		final boolean shouldStartPartition = numberInCurrentPartition >= numberPerPartition;

		if (shouldStartPartition) {
			returnedList.add(currentPartition);

			currentPartition = new FunctionalList<>();
			numberInCurrentPartition = 0;
		} else {
			final int currentElementCount = elementCounter.apply(value);

			final boolean shouldReject = numberInCurrentPartition
					+ currentElementCount >= numberPerPartition;

			if (shouldReject) {
				rejectedItems.add(value);
			} else {
				currentPartition.add(value);
				numberInCurrentPartition += currentElementCount;
			}
		}
	}
}