data_structures_rb/lib/singly_linked_list.rb

# -*- coding: utf-8 -*-
# -*- frozen_string_literal: true -*-
require_relative "single_link_node"

class SinglyLinkedList
  attr_reader :head

  def initialize value
    @head = new_node value
  end

  def tail
    node = head
    node = node.next until last_node?(node)
    node
  end

  def append value
    tail.next = new_node value
  end

  def prepend value
    new_head = new_node value, head
    self.head = new_head
  end

  def delete value
    return remove_head if head.value == value
    remove_node_with_value value
  end

  def size
    node = head
    count = 1

    until last_node? node
      count += 1
      node = node.next
    end

    count
  end

  private

  attr_writer :head

  def new_node value, next_reference=nil
    SingleLinkNode.new value, next_reference
  end

  def last_node? node
    node.next.nil?
  end

  def remove_head
    old_head_value = head.value
    self.head = head.next
    old_head_value
  end

  def remove_node_with_value value
    node = head
    node = node.next until node.next.value == value
    removed_value = node.next.value

    node.next = node.next.next
    removed_value
  end
end