/**
 * An implementation of a stack using an underlying array
 * 
 * @param <K> Generic
 * @author gtowell 
 * Created: Feb 14, 2020
 * Modified: Oct 6, 2020
 * Modified: August 6, 2021
 */
public class ArrayStack<K> implements StackIntf<K> {
    /** The default capacity of the stack */
    private static final int DEFAULT_CAPACITY = 40;
    /** The number of items in the stack */
    private int size;
    /** The array used to hold the stack items */
    private K[] underlyingArray;

    /**
     * Create a stack with the default capacity
     */
    public ArrayStack() {
        this(DEFAULT_CAPACITY);
    }

    /**
     * Create a stack with the given capacity
     * 
     * @param capacity the max number items the stack can hold.
     */
    @SuppressWarnings("unchecked")
    public ArrayStack(int capacity) {
        size = 0;
        underlyingArray = (K[]) new Object[capacity];
    }

    @Override
    public boolean isEmpty() {
        return size == 0;
    }

    @Override
    public K push(K e) {
        // TO BE WRITTEN
        return null;
    }

    @Override
    public K peek() {
        if (size > 0) {
            return underlyingArray[size - 1];
        }
        return null;
    }

    @Override
    public K pop() {
        // TO BE WRITTEN
        return null;
    }

     @Override
    public int size() {
        return size;
    }

    @Override
    public void clear() {
        // TO BE WRITTEN
    }

    public String toString() {
        StringBuffer sb = new StringBuffer();
        sb.append("{ ");
        for (int i = 0; i < size; i++) {
            sb.append(underlyingArray[i]);
            sb.append(" ");
        }
        sb.append("}");
        return sb.toString();
    }

    /**
     * Illustrate stack operations and usage. 
     * 
     * @param args
     */
    public static void main(String[] args) {
        ArrayStack<Integer> stack = new ArrayStack<>();
        stack.push(5);
        System.out.println("Push 5: " + stack);
        stack.push(3);
        stack.push(7);
        stack.push(2);
        System.out.println("Push 3, then 7, then 2: " + stack);
        System.out.println("Size: " + stack.size());
        System.out.println("Pop:" + stack.pop() + " " + stack);
        System.out.println("Empty?: " + stack.isEmpty());
        System.out.println("Pop:" + stack.pop() + " " + stack);
        stack.clear();
        System.out.println("Stack cleared\nEmpty?: " + stack.isEmpty());

    }
}