/* 
 * esodata - data structures and other things, of varying utility
 * Copyright 2022, Ben Culkin
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *   
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
package bjc.funcdata.bst;

import java.util.Comparator;
import java.util.function.BiFunction;
import java.util.function.Function;
import java.util.function.Predicate;

/**
 * A leaf in a tree.
 *
 * @author ben
 *
 * @param <T>
 *            The data stored in the tree.
 */
public class BinarySearchTreeLeaf<T> implements TreePart<T> {
	/** The data held in this tree leaf */
	protected T data;

	/** Whether this node is soft-deleted or not */
	protected boolean isDeleted;

	/**
	 * Create a new leaf holding the specified data.
	 *
	 * @param element
	 *                The data for the leaf to hold.
	 */
	public BinarySearchTreeLeaf(final T element) {
		data = element;
	}

	@Override
	public void add(final T element, final Comparator<T> comparator) {
		throw new IllegalArgumentException("Can't add to a leaf.");
	}

	@Override
	public <E> E collapse(final Function<T, E> leafTransformer,
			final BiFunction<E, E, E> branchCollapser) {
		if (leafTransformer == null)
			throw new NullPointerException("Transformer must not be null");

		return leafTransformer.apply(data);
	}

	@Override
	public boolean contains(final T element, final Comparator<T> comparator) {
		return this.data.equals(element);
	}

	@Override
	public T data() {
		return data;
	}

	@Override
	public void delete(final T element, final Comparator<T> comparator) {
		if (data.equals(element)) {
			isDeleted = true;
		}
	}

	@Override
	public boolean directedWalk(final DirectedWalkFunction<T> treeWalker) {
		if (treeWalker == null)
			throw new NullPointerException("Tree walker must not be null");

		switch (treeWalker.walk(data)) {
		case SUCCESS:
			return true;
		/* We don't have any children to care about. */
		case FAILURE:
		case LEFT:
		case RIGHT:
		default:
			return false;
		}
	}

	@Override
	public boolean forEach(final TreeLinearizationMethod linearizationMethod,
			final Predicate<T> traversalPredicate) {
		if (traversalPredicate == null)
			throw new NullPointerException("Predicate must not be null");

		return traversalPredicate.test(data);
	}

	@Override
	public String toString() {
		return String.format("BinarySearchTreeLeaf [data='%s', isDeleted=%s]", data,
				isDeleted);
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + (data == null ? 0 : data.hashCode());
		result = prime * result + (isDeleted ? 1231 : 1237);
		return result;
	}

	@Override
	public boolean equals(final Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (!(obj instanceof BinarySearchTreeLeaf<?>))
			return false;

		final BinarySearchTreeLeaf<?> other = (BinarySearchTreeLeaf<?>) obj;

		if (data == null) {
			if (other.data != null)
				return false;
		} else if (!data.equals(other.data))
			return false;
		if (isDeleted != other.isDeleted)
			return false;

		return true;
	}
}