#!/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 'rubydns/extensions/string'

require 'process/daemon'

require 'em-http'
require 'cgi'
require 'nokogiri'
require 'json'

require 'digest/md5'

# You might need to change the user name "daemon". This can be a user name or a user id.
RUN_AS = "daemon"

if RExec.current_user != "root"
	$stderr.puts "Sorry, this command needs to be run as root!"
	exit 1
end

module Wikipedia
	def self.summary_url(title)
		"http://en.wikipedia.org/w/api.php?action=parse&page=#{CGI.escape title}&prop=text&section=0&format=json"
	end
	
	def self.extract_summary(json_text)
		document = JSON::parse(json_text)
		return Nokogiri::HTML(document["parse"]["text"]["*"]).css('p')[0].text
	rescue
		return "Invalid Article."
	end
end

# To use, start the daemon and try:
# dig @localhost fortune CNAME
class WikipediaDNS < Process::Daemon
	@@base_directory = File.dirname(__FILE__)

	Name = Resolv::DNS::Name
	IN = Resolv::DNS::Resource::IN

	def startup
		# Don't buffer output (for debug purposes)
		$stderr.sync = true
		
		cache = {}
		stats = {:requested => 0}
		
		# Start the RubyDNS server
		RubyDNS::run_server do
			on(:start) do
				RExec.change_user(RUN_AS)
				if ARGV.include?("--debug")
					@logger.level = Logger::DEBUG
				else
					@logger.level = Logger::WARN
				end
			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
				
				transaction.defer!
				
				http = EventMachine::HttpRequest.new(Wikipedia.summary_url(title)).get
		
				http.callback do
					summary = Wikipedia.extract_summary(http.response)
					transaction.respond!(*summary.chunked)
				end
				
				http.errback do
					transaction.fail!(:ServFail)
				end
			end
			
			# Default DNS handler
			otherwise do |transaction|
				transaction.fail!(:NXDomain)
			end
		end
	end
end

# RExec daemon runner
WikipediaDNS.daemonize