mail_handler.rb

require "mail"
require "nokogiri"
require "tempfile"
require "fileutils"
require "logger"
require "./server"

logger = Logger.new "mail_handler.log"
mail_string = nil
begin
  mail_string = STDIN.read
  mail = Mail.new mail_string.scrub
  token = Mail::Address.new(mail[:envelope_to].decoded.scrub).local.downcase
  return unless token =~ /\A[a-z0-9]{20,100}\z/
  feed_path = File.expand_path "../public/feeds/#{token}.xml", __FILE__
  return unless File.file? feed_path
  File.open feed_path, "r+" do |feed_file_handler|
    feed_file_handler.flock File::LOCK_EX
    feed = Nokogiri::XML(feed_file_handler.read.scrub) { |config| config.strict.noblanks }
    part = mail.html_part || mail.text_part || mail
    feed.at_css("updated").replace(
      Sinatra::Application.new.helpers.erb(
        :entry,
        layout: false,
        locals: {
          title: mail.subject&.scrub,
          author: mail[:from]&.decoded&.scrub || mail.envelope_from.scrub,
          content_type: part.content_type&.scrub =~ /html/ ? "html" : "text",
          content: part.decoded&.scrub,
        }
      ).scrub
    )
    feed.at_css("entry:last-of-type").remove until feed.to_xml.length <= 500_000
    Tempfile.create do |feed_temp|
      feed_temp.write feed.to_xml.scrub
      FileUtils.mv feed_temp.path, feed_path
    end
  ensure
    feed_file_handler.flock File::LOCK_UN
  end
rescue => e
  logger.fatal [e.message, *e.backtrace, mail_string].join("\n")
  abort
end