package edu.brcc.maxfieldj.ch21Lab;

import java.io.PrintStream;
import java.util.EmptyStackException;
import java.util.Scanner;

public class GenericLinkedStack<E>
{
  private class Node
  {
    E value;
    GenericLinkedStack<E>.Node next;

    Node(GenericLinkedStack<E>.Node val)
    {
      this.value = val;
      this.next = n;
    }
  }

  private GenericLinkedStack<E>.Node top = null;

  public boolean empty()
  {
    return this.top == null;
  }

  public void push(E s)
  {
    this.top = new Node(s, this.top);
  }

  public E pop()
  {
    if (empty()) {
      throw new EmptyStackException();
    }
    E retValue = this.top.value;
    this.top = this.top.next;
    return retValue;
  }

  public E peek()
  {
    if (empty()) {
      throw new EmptyStackException();
    }
    return this.top.value;
  }

  public String toString()
  {
    StringBuilder sBuilder = new StringBuilder();
    GenericLinkedStack<E>.Node p = this.top;

    sBuilder.append("[");
    while (p != null)
    {
      sBuilder.append(p.value);
      p = p.next;
      if (p != null) {
        sBuilder.append(" ");
      }
    }
    sBuilder.append("]");
    return sBuilder.toString();
  }

  public static void main(String[] args)
  {
    GenericLinkedStack<String> st = new GenericLinkedStack();
    System.out.println("Pushing: Amy Bob Chuck");
    System.out.println("Contents of Stack:");
    st.push("Amy");
    st.push("Bob");
    st.push("Chuck");
    System.out.println(st);
    String name = (String)st.pop();
    System.out.println("Popped: " + name);
    System.out.println("Contents of Stack:");
    System.out.println(st);



    GenericLinkedStack<Double> nums = new GenericLinkedStack();
    Scanner keyboard = new Scanner(System.in);
    System.out.println("RPN calculator");
    System.out.print(">");
    for (;;)
    {
      String input = keyboard.nextLine();
      double num2;
      double num1;
      try
      {
        double num = Double.parseDouble(input);
        nums.push(Double.valueOf(num));
        System.out.print(nums.peek() + ">");
      }
      catch (Exception e)
      {
        num2 = ((Double)nums.pop()).doubleValue();
        num1 = ((Double)nums.pop()).doubleValue();
        switch (input.charAt(0))
        {
        case '+':
          nums.push(Double.valueOf(num1 + num2));
          System.out.print(nums.peek() + ">");
        }
      }
      continue;

      nums.push(Double.valueOf(num1 - num2));
      System.out.print(nums.peek() + ">");
    }
  }
}