package Containers;

import org.jetbrains.annotations.NotNull;

import java.util.Iterator;
import java.util.NoSuchElementException;

public class Stack<Item> implements Iterable<Item> {
    private int size;
    private Node first;

    private class Node{
        private Item item;
        private Node next;
    }

    private class MyIterator implements Iterator<Item> {
        private Node current = first;

        @Override
        public boolean hasNext() {
            return current != null;
        }

        @Override
        public Item next() {
            if (!hasNext()) {
                throw new NoSuchElementException();
            }

            Item item = current.item;
            current = current.next;

            return item;
        }

        @Override
        public void remove() {
            throw new UnsupportedOperationException();
        }
    }

    @NotNull
    public Iterator<Item> iterator() {
        return new MyIterator();
    }

    public Stack() {
        first = null;
        size = 0;
    }

    public int getSize() {
        return size;
    }

    public boolean isEmpty() {
        return first == null;
    }

    public void push(Item item) {
        Node previousItem = first;
        first = new Node();
        first.item = item;
        first.next = previousItem;
        size++;
    }

    public Item pop() {
        if (isEmpty()){
            throw new IndexOutOfBoundsException("Stack is empty");
        }

        Item item = first.item;
        first = first.next;
        size--;

        return item;
    }

    public Item peek() {
        if (isEmpty()){
            throw new IndexOutOfBoundsException("Stack is empty");
        }

        return first.item;
    }

    @Override
    public String toString() {
        StringBuilder builder = new StringBuilder("Stack [");

        for (Item item : this) {
            builder.append(item);
            builder.append(' ');
        }

        builder.append("]\n");
        builder.append("Size: ").append(size);

        return builder.toString();
    }
}