# frozen_string_literal: true

require "format"

class SpamProtection
  IP_RBLS = ["opm.blitzed.us", "bsb.empty.us"].freeze
  HOST_RBLS = ["multi.surbl.org", "bsb.empty.us"].freeze
  SECOND_LEVEL = %w(co com net org gov).freeze

  attr_accessor :this_blog

  def initialize(a_blog)
    self.this_blog = a_blog
  end

  def is_spam?(string)
    return false unless this_blog.sp_global
    return false if string.blank?

    reason = catch(:hit) do
      case string
      when Format::IP_ADDRESS then scan_ip(string)
      when Format::HTTP_URI then scan_uris([string])
      else scan_text(string)
      end
    end

    if reason
      logger.info("[SP] Hit: #{reason}")
      true
    end
  end

  protected

  def scan_ip(ip_address)
    logger.info("[SP] Scanning IP #{ip_address}")
    query_rbls(IP_RBLS, ip_address.split(".").reverse.join("."))
  end

  def scan_text(string)
    # FIXME: Unify HTTP URI matchers
    uri_list = string.scan(%r{(http://[^\s"]+)}m).flatten

    check_uri_count(uri_list)
    scan_uris(uri_list)

    false
  end

  def check_uri_count(uris)
    limit = this_blog.sp_url_limit
    return if limit.to_i.zero?

    throw :hit, "Hard URL Limit hit: #{uris.size} > #{limit}" if uris.size > limit
  end

  def scan_uris(uris = [])
    uris.each do |uri|
      host = begin
               URI.parse(uri).host
             rescue URI::InvalidURIError
               next
             end
      return scan_ip(host) if Format::IP_ADDRESS.match?(host)

      host_parts = host.split(".").reverse
      domain = []

      # Check for two level TLD
      (SECOND_LEVEL.include?(host_parts[1]) ? 3 : 2).times do
        domain.unshift(host_parts.shift)
      end

      logger.info("[SP] Scanning domain #{domain.join(".")}")
      query_rbls(HOST_RBLS, host, domain.join("."))
      logger.info("[SP] Finished domain scan #{domain.join(".")}")
      return false
    end
  end

  def query_rbls(rbls, *subdomains)
    rbls.each do |rbl|
      subdomains.uniq.each do |d|
        begin
          response = IPSocket.getaddress([d, rbl].join("."))
          if /^127\.0\.0\./.match?(response)
            throw :hit,
                  "#{rbl} positively resolved subdomain #{d} => #{response}"
          end
        rescue SocketError
          # NXDOMAIN response => negative:  d is not in RBL
          next
        end
      end
    end
    false
  end

  def logger
    @logger ||= ::Rails.logger || Logger.new(STDOUT)
  end
end