class ActionDispatch::RemoteIp::GetIp

def calculate_ip
  client_ip     = @env['HTTP_CLIENT_IP']
  forwarded_ips = ips_from('HTTP_X_FORWARDED_FOR')
  remote_addrs  = ips_from('REMOTE_ADDR')
  check_ip = client_ip && @middleware.check_ip
  if check_ip && !forwarded_ips.include?(client_ip)
    # We don't know which came from the proxy, and which from the user
    raise IpSpoofAttackError, "IP spoofing attack?!" \
      "HTTP_CLIENT_IP=#{@env['HTTP_CLIENT_IP'].inspect}" \
      "HTTP_X_FORWARDED_FOR=#{@env['HTTP_X_FORWARDED_FOR'].inspect}"
  end
  not_proxy = client_ip || forwarded_ips.last || remote_addrs.first
  # Return first REMOTE_ADDR if there are no other options
  not_proxy || ips_from('REMOTE_ADDR', :allow_proxies).first
end

def initialize(env, middleware)
  @env          = env
  @middleware   = middleware
  @calculated_ip = false
end

def ips_from(header, allow_proxies = false)
  ips = @env[header] ? @env[header].strip.split(/[,\s]+/) : []
  allow_proxies ? ips : ips.reject{|ip| ip =~ @middleware.proxies }
end

def to_s
  return @ip if @calculated_ip
  @calculated_ip = true
  @ip = calculate_ip
end