package bjc.utils.funcdata.bst;

import static bjc.utils.funcdata.bst.DirectedWalkFunction.DirectedWalkResult.FAILURE;
import static bjc.utils.funcdata.bst.DirectedWalkFunction.DirectedWalkResult.LEFT;
import static bjc.utils.funcdata.bst.DirectedWalkFunction.DirectedWalkResult.RIGHT;
import static bjc.utils.funcdata.bst.DirectedWalkFunction.DirectedWalkResult.SUCCESS;

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

/**
 * A binary node in a tree.
 * 
 * @author ben
 *
 * @param <T>
 *            The data type stored in the tree.
 */
public class BinarySearchTreeNode<T> extends BinarySearchTreeLeaf<T> {
	/*
	 * The left child of this node
	 */
	private ITreePart<T>	left;

	/*
	 * The right child of this node
	 */
	private ITreePart<T>	right;

	/**
	 * Create a new node with the specified data and children.
	 * 
	 * @param element
	 *            The data to store in this node.
	 * @param lft
	 *            The left child of this node.
	 * @param rght
	 *            The right child of this node.
	 */
	public BinarySearchTreeNode(T element, ITreePart<T> lft,
			ITreePart<T> rght) {
		super(element);
		this.left = lft;
		this.right = rght;
	}

	@Override
	public void add(T element, Comparator<T> comparator) {
		if (comparator == null) {
			throw new NullPointerException("Comparator must not be null");
		}

		switch (comparator.compare(data, element)) {
			case -1:
				if (left == null) {
					left = new BinarySearchTreeNode<>(element, null, null);
				} else {
					left.add(element, comparator);
				}
				break;
			case 0:
				if (isDeleted) {
					isDeleted = false;
				} else {
					throw new IllegalArgumentException("Can't add duplicate values");
				}
				break;
			case 1:
				if (right == null) {
					right = new BinarySearchTreeNode<>(element, null, null);
				} else {
					right.add(element, comparator);
				}
				break;
			default:
				throw new IllegalStateException("Error: Comparator yielded invalid value");
		}
	}

	@Override
	public <E> E collapse(Function<T, E> nodeCollapser, BiFunction<E, E, E> branchCollapser) {
		if (nodeCollapser == null || branchCollapser == null) {
			throw new NullPointerException("Collapser must not be null");
		}

		E collapsedNode = nodeCollapser.apply(data);

		if (left != null) {
			E collapsedLeftBranch = left.collapse(nodeCollapser, branchCollapser);

			if (right != null) {
				E collapsedRightBranch = right.collapse(nodeCollapser, branchCollapser);

				E collapsedBranches = branchCollapser.apply(collapsedLeftBranch, collapsedRightBranch);

				return branchCollapser.apply(collapsedNode, collapsedBranches);
			}

			return branchCollapser.apply(collapsedNode, collapsedLeftBranch);
		}

		if (right != null) {
			E collapsedRightBranch = right.collapse(nodeCollapser, branchCollapser);

			return branchCollapser.apply(collapsedNode, collapsedRightBranch);
		}

		return collapsedNode;
	}

	@Override
	public boolean contains(T element, Comparator<T> comparator) {
		if (comparator == null) {
			throw new NullPointerException("Comparator must not be null");
		}

		return directedWalk(currentElement -> {
			switch (comparator.compare(element, currentElement)) {
				case -1:
					return LEFT;
				case 0:
					return isDeleted ? FAILURE : SUCCESS;
				case 1:
					return RIGHT;
				default:
					return FAILURE;
			}
		});
	}

	@Override
	public void delete(T element, Comparator<T> comparator) {
		if (comparator == null) {
			throw new NullPointerException("Comparator must not be null");
		}

		directedWalk(currentElement -> {
			switch (comparator.compare(data, element)) {
				case -1:
					return left == null ? FAILURE : LEFT;
				case 0:
					isDeleted = true;
					return FAILURE;
				case 1:
					return right == null ? FAILURE : RIGHT;
				default:
					return FAILURE;
			}
		});
	}

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

		switch (treeWalker.walk(data)) {
			case SUCCESS:
				return true;
			case LEFT:
				return left.directedWalk(treeWalker);
			case RIGHT:
				return right.directedWalk(treeWalker);
			case FAILURE:
				return false;
			default:
				return false;
		}
	}

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

		switch (linearizationMethod) {
			case PREORDER:
				return preorderTraverse(linearizationMethod, traversalPredicate);
			case INORDER:
				return inorderTraverse(linearizationMethod, traversalPredicate);
			case POSTORDER:
				return postorderTraverse(linearizationMethod, traversalPredicate);
			default:
				throw new IllegalArgumentException(
						"Passed an incorrect TreeLinearizationMethod "
								+ linearizationMethod + ". WAT");
		}
	}

	private boolean inorderTraverse( TreeLinearizationMethod linearizationMethod, Predicate<T> traversalPredicate) {
		if (!traverseLeftBranch(linearizationMethod, traversalPredicate)) {
			return false;
		}

		if (!traverseElement(traversalPredicate)) {
			return false;
		}

		if (!traverseRightBranch(linearizationMethod, traversalPredicate)) {
			return false;
		}

		return true;
	}

	private boolean postorderTraverse(TreeLinearizationMethod linearizationMethod, Predicate<T> traversalPredicate) {
		if (!traverseLeftBranch(linearizationMethod, traversalPredicate)) {
			return false;
		}

		if (!traverseRightBranch(linearizationMethod, traversalPredicate)) {
			return false;
		}

		if (!traverseElement(traversalPredicate)) {
			return false;
		}

		return true;

	}

	private boolean preorderTraverse(TreeLinearizationMethod linearizationMethod, Predicate<T> traversalPredicate) {
		if (!traverseElement(traversalPredicate)) {
			return false;
		}

		if (!traverseLeftBranch(linearizationMethod, traversalPredicate)) {
			return false;
		}

		if (!traverseRightBranch(linearizationMethod, traversalPredicate)) {
			return false;
		}

		return true;
	}

	private boolean traverseElement(Predicate<T> traversalPredicate) {
		boolean nodeSuccesfullyTraversed;

		if (isDeleted) {
			nodeSuccesfullyTraversed = true;
		} else {
			nodeSuccesfullyTraversed = traversalPredicate.test(data);
		}

		return nodeSuccesfullyTraversed;
	}

	private boolean traverseLeftBranch(TreeLinearizationMethod linearizationMethod, Predicate<T> traversalPredicate) {
		boolean leftSuccesfullyTraversed;

		if (left == null) {
			leftSuccesfullyTraversed = true;
		} else {
			leftSuccesfullyTraversed = left.forEach(linearizationMethod, traversalPredicate);
		}

		return leftSuccesfullyTraversed;
	}

	private boolean traverseRightBranch(TreeLinearizationMethod linearizationMethod, Predicate<T> traversalPredicate) {
		boolean rightSuccesfullyTraversed;

		if (right == null) {
			rightSuccesfullyTraversed = true;
		} else {
			rightSuccesfullyTraversed = right.forEach(linearizationMethod, traversalPredicate);
		}

		return rightSuccesfullyTraversed;
	}
}