class Gapic::LruHash


access/creation of the keys.
Linked list based hash maintaining the order of
@private
#

def get key 

def get key
  return nil unless @cache.key? key
  node = @cache[key]
  move_to_top node
  node.value
end

def initialize size = 1 

def initialize size = 1
  raise ArgumentError, "The size of LRU hash can't be < 1" unless size > 1
  @start = nil
  @end = nil
  @size = size
  @cache = {}
end

def insert_at_top node 

def insert_at_top node
  if @start.nil?
    @start = node
    @end = node
  else
    node.next = @start
    @start.prev = node
    @start = node
  end
end

def move_to_top node 

def move_to_top node
  return if node.equal? @start
  if node.equal? @end
    @end = node.prev
    @end.next = nil
  else
    node.prev.next = node.next
    node.next.prev = node.prev
  end
  node.prev = nil
  node.next = @start
  @start.prev = node
  @start = node
end

def put key, value 

def put key, value
  if @cache.key? key
    node = @cache[key]
    node.value = value
    move_to_top node
  else
    remove_tail if @cache.size >= @size
    new_node = Node.new key, value
    insert_at_top new_node
    @cache[key] = new_node
  end
end

def remove_tail 

def remove_tail
  @cache.delete @end.key
  @end = @end.prev
  @end.next = nil if @end
end