# frozen_string_literal: true

module Truemail
  module Validate
    class Mx < Truemail::Validate::Base
      require 'resolv'

      ERROR = 'target host(s) not found'

      def run
        return false unless Truemail::Validate::Regex.check(result)
        result.domain = result.email[Truemail::RegexConstant::REGEX_DOMAIN_FROM_EMAIL, 1]
        return true if success(mx_lookup)
        add_error(Truemail::Validate::Mx::ERROR)
        false
      end

      private

      def host_extractor_methods
        %i[hosts_from_mx_records? hosts_from_cname_records? host_from_a_record?]
      end

      def mx_lookup
        host_extractor_methods.any? do |method|
          Truemail::Validate::ResolverExecutionWrapper.call { send(method) }
        end
      end

      def fetch_target_hosts(hosts)
        result.mail_servers.push(*hosts)
      end

      def mx_records(domain)
        Resolv::DNS.new.getresources(domain, Resolv::DNS::Resource::IN::MX).sort_by(&:preference).map do |mx_record|
          Resolv.getaddress(mx_record.exchange.to_s)
        end
      end

      def mail_servers_found?
        !result.mail_servers.empty?
      end

      def hosts_from_mx_records?
        fetch_target_hosts(mx_records(result.domain))
        mail_servers_found?
      end

      def hosts_from_cname_records?
        cname_records = Resolv::DNS.new.getresources(result.domain, Resolv::DNS::Resource::IN::CNAME)
        return if cname_records.empty?
        cname_records.each do |cname_record|
          host = Resolv.getaddress(cname_record.name.to_s)
          hostname = Resolv.getname(host)
          found_hosts = mx_records(hostname)
          fetch_target_hosts(found_hosts.empty? ? [host] : found_hosts)
        end
        mail_servers_found?
      end

      def host_from_a_record?
        fetch_target_hosts([Resolv.getaddress(result.domain)])
        mail_servers_found?
      end
    end
  end
end