socketry/rubydns

#!/usr/bin/env ruby
# encoding: utf-8

# Copyright, 2009, 2012, by Samuel G. D. Williams. <http://www.codeotaku.com>
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

require 'rubydns'

require 'cgi'
require 'json'

require 'digest/md5'

require 'async/http/client'
require 'async/dns/extensions/string'
require 'async/http/endpoint'

# Encapsulates the logic for fetching information from Wikipedia.
module Wikipedia
    ENDPOINT = Async::HTTP::Endpoint.parse("https://en.wikipedia.org")
    
    def self.lookup(title, logger: nil)
        client = Async::HTTP::Client.new(ENDPOINT)
        url = self.summary_url(title)
        
        logger&.debug "Making request to #{ENDPOINT} for #{url}."
        response = client.get(url, headers: {"user-agent" => "RubyDNS"})
        logger&.debug "Got response #{response.inspect}."
        
        if response.status == 301
            return lookup(response.headers['location'], logger: logger)
        else
            return self.extract_summary(response.body.read).force_encoding('ASCII-8BIT')
        end
    ensure
        response&.close
        client&.close
    end
    
    def self.summary_url(title)
        "/api/rest_v1/page/summary/#{CGI.escape title}"
    end

    def self.extract_summary(json_text)
        document = JSON.parse(json_text)
        
        return document['extract']
    rescue
        return 'Invalid Article.'
    end
end

# A DNS server that queries Wikipedia and returns summaries for
# specifically crafted queries.
class WikipediaDNS
    Name = Resolv::DNS::Name
    IN = Resolv::DNS::Resource::IN
    
    INTERFACES = [
        [:udp, '::', 5300],
        [:tcp, '::', 5300],
    ]

    def startup
        # Don't buffer output (for debug purposes)
        $stderr.sync = true

        stats = { requested: 0 }

        # Start the RubyDNS server
        RubyDNS.run_server(INTERFACES) do
            on(:start) do
                # Process::Daemon::Privileges.change_user(RUN_AS)
                
                @logger.info "Starting Wikipedia DNS..."
            end

            match(/stats\.wikipedia/, IN::TXT) do |transaction|
                transaction.respond!(*stats.inspect.chunked)
            end

            match(/(.+)\.wikipedia/, IN::TXT) do |transaction, match_data|
                title = match_data[1]
                stats[:requested] += 1
                
                summary = Wikipedia.lookup(title, logger: @logger)
                
                transaction.respond!(*summary.chunked)
            end

            # Default DNS handler
            otherwise do |transaction|
                transaction.fail!(:NXDomain)
            end
        end
    end
end

wikipedia_dns = WikipediaDNS.new
wikipedia_dns.startup