class BasicLinkedList

# File lib/basic_linked_list.rb, line 5
def initialize
  @head = nil
end

# File lib/basic_linked_list.rb, line 9
def append(element)
  new_node = Node.new(element)
  @head.nil? ? (@head = new_node) : (last_node.next_node = new_node)
  new_node.data
end

# File lib/basic_linked_list.rb, line 22
def count(node = @head, counter = 0)
  return counter if node.nil?
  counter += 1
  return counter if node.next_node.nil?
  node = node.next_node
  count(node, counter)
end

# File lib/basic_linked_list.rb, line 57
def find(start_position, num_of_elements)
  start_node = @head
  start_position.times do
    return "Error: start position outside linkedlist" if start_node.next_node.nil?
    start_node = start_node.next_node
  end
  return "" if num_of_elements == 0
  
  str = start_node.data.to_s
  return str if start_node.next_node.nil?

  node = start_node.next_node
  (num_of_elements - 1).times do
    str << " " + node.data
    return str if node.next_node.nil?
    node = node.next_node
  end
  str
end

# File lib/basic_linked_list.rb, line 88
def includes?(element)
  node = @head
  until node.next_node.nil?
    return true if node.data == element
    node = node.next_node
  end
  false
end

# File lib/basic_linked_list.rb, line 45
def insert(position, element)
  return prepend(element) if position == 0
  new_node = Node.new(element)
  node_before_insertion = @head
  (position - 1).times do
    node_before_insertion = node_before_insertion.next_node
  end
  new_node.next_node = node_before_insertion.next_node
  node_before_insertion.next_node = new_node
  new_node.data
end

# File lib/basic_linked_list.rb, line 15
def last_node(node = @head)
  return node if node.nil? 
  return node if node.next_node.nil?
  node = node.next_node
  last_node(node)
end

# File lib/basic_linked_list.rb, line 77
def pop
  node = @head
  previous_node = nil
  until node.next_node.nil? do
    previous_node = node
    node = node.next_node
  end
  previous_node.next_node = nil
  node.data
end

# File lib/basic_linked_list.rb, line 38
def prepend(element)
  new_head = Node.new(element)
  new_head.next_node = @head
  @head = new_head
  @head.data
end

# File lib/basic_linked_list.rb, line 30
def to_string(node = @head, str = "")
  return str if node.nil?
  node == @head ? (str << node.data.to_s) : (str << " " + node.data.to_s)
  return str if node.next_node.nil?
  node = node.next_node
  to_string(node,str)
end