queues_with_sub_queues.rb

class Queue
  def initialize(max_size: nil)
    @head_node = nil
    @max_size = max_size
  end

  def enqueue(element)
    if last_node
      last_node.next_node = Node.new(element)
    else
      @head_node = Node.new(element)
    end
  end

  def dequeue
    return if head_node.nil?

    node_to_be_dequeued = head_node
    @head_node = head_node.next_node

    node_to_be_dequeued.content
  end

  def last_node
    last_node = @head_node

    while last_node && last_node.next_node
      last_node = last_node.next_node
    end

    last_node
  end

  def first_node
    head_node
  end

  def full?
    if max_size.nil?
      false
    else
      size == max_size
    end
  end

  def empty?(*args)
    size == 0
  end

  def many?
    size > 1
  end

  private

  attr_accessor :head_node, :max_size

  def size
    return 0 if head_node.nil?

    counter = 1
    last = head_node

    while last.next_node
      counter += 1
      last = last.next_node
    end

    counter
  end
end

class QueuesWithSubQueues
  SUB_QUEUES_MAX_SIZE = 5

  def initialize
    @sub_queues = ::Queue.new
    generate_new_sub_queue
  end

  def enqueue(element)
    last = last_sub_queue

    generate_new_sub_queue if last.full?

    last.enqueue(element).content
  end

  def dequeue
    first = first_sub_queue

    dequeued = first.dequeue

    if first.empty? && @sub_queues.many?
      @sub_queues.dequeue
    end

    dequeued
  end

  def sub_queues_count
    counter = 1
    last = @sub_queues.first_node

    while last.next_node
      counter +=1
      last = last.next_node
    end

    counter
  end

  private

  def generate_new_sub_queue
    @sub_queues.enqueue( ::Queue.new(max_size: SUB_QUEUES_MAX_SIZE)  )
  end

  def last_sub_queue
    @sub_queues.last_node.content
  end

  def first_sub_queue
    @sub_queues.first_node.content
  end
end

class Node
  attr_accessor :content, :next_node

  def initialize(content)
    @content = content
  end
end

queue = QueuesWithSubQueues.new
puts "queue.sub_queues_count #{queue.sub_queues_count} "

puts '========='
puts 'Enqueue'
puts queue.enqueue('Alex')
15.times do |n|
  puts queue.enqueue(n)
end
puts "queue.sub_queues_count #{queue.sub_queues_count} "

puts '========='
puts 'Dequeue'
17.times do |n|
  puts queue.dequeue
end
puts "queue.sub_queues_count #{queue.sub_queues_count} "