/*******************************************************************************
 * ============LICENSE_START====================================================
 * * org.onap.aaf
 * * ===========================================================================
 * * Copyright © 2017 AT&T Intellectual Property. All rights reserved.
 * * ===========================================================================
 * * Licensed under the Apache License, Version 2.0 (the "License");
 * * you may not use this file except in compliance with the License.
 * * You may obtain a copy of the License at
 * * 
 *  *      http://www.apache.org/licenses/LICENSE-2.0
 * * 
 *  * Unless required by applicable law or agreed to in writing, software
 * * distributed under the License is distributed on an "AS IS" BASIS,
 * * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * * See the License for the specific language governing permissions and
 * * limitations under the License.
 * * ============LICENSE_END====================================================
 * *
 * * ECOMP is a trademark and service mark of AT&T Intellectual Property.
 * *
 ******************************************************************************/
package org.onap.aaf.rosetta;


/**
 * A Ladder is a Stack like Storage Class, but where you can ascend and descend while
 * the elements exists.
 * 
 * Like an extension ladder, you can make taller as you go
 * 
 *
 */
public class Ladder<T> {
	public static final int DEFAULT_INIT_SIZE=8;
	private final int init_size;
	private int rung; // as in ladder
	private Object[] struts;

	public Ladder() {
		rung=0;
		init_size = DEFAULT_INIT_SIZE;
		struts=new Object[init_size];
	}

	public Ladder(int initSize) {
		rung=0;
		init_size = initSize;
		struts=new Object[init_size];
	}

	public void bottom() {
		rung = 0;
	}
	
	public void top() {
		rung = struts.length-1;
		while(rung>0 && struts[rung]==null)--rung;
	}
	
	public int howHigh() {
		return rung;
	}
	
	public void jumpTo(int rung) {
		if(rung>=struts.length) {
			Object[] temp = new Object[init_size*((rung/init_size)+1)];
			System.arraycopy(struts, 0, temp, 0, struts.length);
			struts = temp;
		}
		this.rung = rung;
	}
	
	public int height() {
		return struts.length;
	}
	
	public void cutTo(int rungs) {
		Object[] temp = new Object[rungs];
		System.arraycopy(struts, 0, temp, 0, Math.min(rungs, struts.length));
		struts = temp;
	}
	
	public void ascend() {
		++rung;
		if(rung>=struts.length) {
			Object[] temp = new Object[struts.length+init_size];
			System.arraycopy(struts, 0, temp, 0, struts.length);
			struts = temp;
		}
	}
	
	public void descend() {
		--rung;
	}
	
	@SuppressWarnings("unchecked")
	public T peek() {
		return (T)struts[rung];
	}
	
	public void push(T t) {
		struts[rung]=t;
	}
	
	@SuppressWarnings("unchecked")
	public T pop() {
		T t = (T)struts[rung];
		struts[rung]=null;
		return t;
	}

}