package bintree;

import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;

public class BinTreeCAS implements BinTree {

	private static class Node {
		final int value;
		AtomicInteger occ;
		AtomicReference<Node> left, right;

		private Node(int value, int initOcc) {
			this.value = value;
			occ = new AtomicInteger(initOcc);

			left = new AtomicReference<>();
			left.set(null);

			right = new AtomicReference<>();
			right.set(null);
		}
	}

	private final Node root = new Node(0, 0);

	public void insert(int value) {
		Node n = root;
		while (true) {
			int nval = n.value;
			if (value == nval) {
				n.occ.addAndGet(1);
				return;
			} 
			else if (value < nval) {
				if (n.left.compareAndSet(null, new Node(value, 1))) {
					return;
				} else {
					n = n.left.get();
				}
			} 
			else { // value > nval
				if (n.right.compareAndSet(null, new Node(value, 1))) {
					return;
				} else {
					n = n.right.get();
				}
			} 
		}
	}

	public int occurs(int value) {
		Node n = root;
		do {
			int nval = n.value;
			if (value == nval) {
				return n.occ.intValue();
			}
			n = (value < nval) ? n.left.get() : n.right.get();
		} while (n != null);
		// value not found
		return 0;
	}
}