package com.chamika;

import java.util.Iterator;

/**
 * Created by dinu on 12/13/17.
 */
public class Stack {
    public static void main(String[] args) {
        StackDataStructure<Integer> stackDataStructure = new StackDataStructure();
        stackDataStructure.print();
        stackDataStructure.push(9);
        stackDataStructure.push(7);
        stackDataStructure.push(89);
        stackDataStructure.print();
        stackDataStructure.pop();
        stackDataStructure.print();
        stackDataStructure.pop();
        stackDataStructure.print();
        stackDataStructure.pop();
        stackDataStructure.print();

        StackDataStructure<String> stringstack = new StackDataStructure<>();
        stringstack.push("Amma");
        stringstack.push("Thaththa");
        stringstack.push("Baba");
        stringstack.print();

        System.out.println("Testing Iterable");
        for (StackNode node : stringstack) {
            System.out.println(node.value);
        }

//        StackNode<String> s1 = new StackNode<>();
//        s1.value = "A";
//        StackNode<String> s2 = new StackNode<>();
//        s2.value = "B";
//        StackNode<String> s3 = new StackNode<>();
//        s3.value = "C";
//        s1.next = s2;
//        s2.next = s3;
//        for(String s:s1){
//
//        }

    }
}

class StackDataStructure<T> implements Iterable<StackNode> {
    StackNode<T> tail;
    StackNode<T> head;

    void push(T value) {
        if (head == null) {
            head = new StackNode();
            head.value = value;
            head.next = null;
            tail = head;
            tail.previous = null;
        } else {
            tail.next = new StackNode();
            tail.next.value = value;
            tail.next.previous = tail;
            tail.next.next = null;
            tail = tail.next;
        }
    }

    StackNode pop() {
        if (head == null) {
            return null;
        } else {
            StackNode node = tail;
            if (tail.previous == null) {
                head = null;
                tail = null;
                return node;
            }
            tail = tail.previous;
            tail.next = null;
            return node;
        }
    }

    void print() {
        System.out.println("Printing Stack");
        if (head == null) {
            System.out.println("Stack is Empty");
        } else {
            StackNode node = head;
            while (node != null) {
                System.out.print(node.value + " ");
                node = node.next;
            }
        }
        System.out.println("\nPrinting Stack Finished");
    }

    @Override
    public Iterator<StackNode> iterator() {
        return new StackNodeIterator(head);
    }
}

class StackNode<T> {
    T value;
    StackNode next;
    StackNode previous;

    public StackNode getNext() {
        return next;
    }
}

class StackNodeIterator implements Iterator<StackNode> {

    StackNode next;

    public StackNodeIterator(StackNode next) {
        this.next = next;
    }

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

    @Override
    public StackNode next() {
        StackNode ret = next;
        next = next.next;
        return ret;
    }
}