class WWW::Mechanize::History

def clear
  @history_index.clear
  super
end

def initialize(max_size = nil)
  @max_size       = max_size
  @history_index  = {}
end

def initialize_copy(orig)
  super
  @history_index = orig.instance_variable_get(:@history_index).dup
end

def pop
  return nil if length == 0
  page = super
  remove_from_index(page)
  page
end

def push(page, uri = nil)
  super(page)
  @history_index[(uri ? uri : page.uri).to_s] = page
  if @max_size && self.length > @max_size
    while self.length > @max_size
      self.shift
    end
  end
  self
end

def remove_from_index(page)
  @history_index.each do |k,v|
    @history_index.delete(k) if v == page
  end
end

def shift
  return nil if length == 0
  page    = self[0]
  self[0] = nil
  super
  remove_from_index(page)
  page
end

def visited?(url)
  ! visited_page(url).nil?
end

def visited_page(url)
  @history_index[(url.respond_to?(:uri) ? url.uri : url).to_s]
end