# dependencies
require "net/dns"

# stdlib
require "ipaddr"

# modules
require "reversed/version"

module Reversed
  def self.lookup(ip, timeout: 5, nameservers: nil, fallback: true)
    ip = ip.to_s
    unless ip.empty?
      begin
        # ensure valid ip
        ip = IPAddr.new(ip)
      rescue IPAddr::InvalidAddressError
        raise ArgumentError, "Invalid IP"
      end

      options = {
        retry_number: 3,
        udp_timeout: timeout
      }
      options[:nameservers] = nameservers if nameservers
      begin
        resolver = Net::DNS::Resolver.new(options).search(ip.reverse, Net::DNS::PTR)
        answer = resolver.answer.first
        if !answer && fallback
          answer = resolver.authority.first
        end
        if answer && !answer.value.empty?
          answer.value.split(" ").first[0..-2]
        end
      rescue Net::DNS::Resolver::NoResponseError
        nil
      rescue Errno::EAFNOSUPPORT
        options[:use_tcp] = true
        options[:tcp_timeout] = timeout
        retry
      end
    end
  end
end

# not ideal, but fixes error on timeout with Ruby 3.1+
# (which removed TimeoutError)
# need to define rather than rescue NameError
# to allow for multiple nameservers to be checked
# define here rather than for duration of search method for thread-safety
# apply to all Ruby versions to fix deprecation warnings
Net::DNS::Resolver::TimeoutError = Timeout::Error