Ruby class to check URL validity

url_checker.rb

require "ipaddr"
require "resolv"
require "uri"

class UrlChecker
  SCHEME_REGEX = Regexp.new(/\Ahttps?/)
  HOST_REGEX = Regexp.new(/.+\..+/)
  IPV4_REGEX = Regexp.new(/(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)(\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}/)
  IPV6_REGEX = Regexp.new(/(([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]))/)
  PRIVATE_RANGES = %w[127.0.0.0/8 192.168.0.0/16 172.16.0.0/12 10.0.0.0/8 100.64.0.0/10 fc00::/7 169.254.169.254].map { |r| IPAddr.new(r) }

  def initialize(url)
    @url = url
  end

  def uri
    @uri ||= URI.parse(@url)
  end

  def is_ip?
    return @is_ip unless @is_ip.nil?
    @is_ip = uri.host.match?(IPV4_REGEX) || uri.host.match?(IPV6_REGEX)
  end

  def valid?
    return false unless uri.scheme&.match?(SCHEME_REGEX)
    return false unless uri.host&.match?(HOST_REGEX) || uri.host&.match?(IPV6_REGEX)

    if is_ip?
      ip = IPAddr.new(uri.host)
      return false if PRIVATE_RANGES.any? { |r| r.include?(ip) }
    end

    true
  rescue URI::InvalidURIError
    false
  end

  def resolves?
    return false unless valid?

    ip = if is_ip?
      IPAddr.new(uri.host)
    else
      IPAddr.new(Resolv.getaddress(uri.host))
    end

    PRIVATE_RANGES.none? { |r| r.include?(ip) }
  rescue Resolv::ResolvError
    false
  end
end

The goal with this class is to check that a given URL won't be inaccessible for public requests... that is, it rejects URLs like http://localhost, http://192.168.1.1, etc. It does not verify that a URL is reachable.