class LinkedListNode
  attr_accessor :value, :next_node

  def initialize(value, next_node = nil)
    @value = value
    @next_node = next_node
  end
end

class Stack
  attr_reader :data

  def initialize
    @data = nil
  end

  # Push a value onto the stack
  def push(value)
    @data = LinkedListNode.new(value, @data)
  end

  def pop
    raise 'Stack is empty?' if empty?
    @data = @data.next_node
  end

  def value
    @data.value unless empty?
  end

  def next_node
    @data.next_node unless empty?
  end

  def empty?
    @data.nil?
  end
end

def reverse_list(list)
  reverse_stack = Stack.new

  while list
    reverse_stack.push(list.value)
    list = list.next_node
  end
  reverse_stack
end

def print_values(list_node)
  if list_node
    print "#{list_node.value} --> "
    print_values(list_node.next_node)
  else
    print "nil\n"
  end
end

stack = Stack.new
stack.push(34)
stack.push(99)
stack.push(64)
stack.push(76)

revlist = reverse_list(stack)

print_values(stack)
print_values(revlist)