mastodon/app/services/process_feed_service.rb

class ProcessFeedService < BaseService
  # Create local statuses from an Atom feed
  # @param [String] body Atom feed
  # @param [Account] account Account this feed belongs to
  def call(body, account)
    xml = Nokogiri::XML(body)

    # If we got a full feed, make sure the account's profile is up to date
    unless xml.at_xpath('/xmlns:feed').nil?
      update_remote_profile_service.(xml.at_xpath('/xmlns:feed/xmlns:author'), account)
    end

    # Process entries
    xml.xpath('//xmlns:entry').each do |entry|
      next unless [:note, :comment, :activity].include? object_type(entry)

      status = Status.find_by(uri: activity_id(entry))

      # If we already have a post and the verb is now "delete", we gotta delete it and move on!
      if verb(entry) == :delete
        delete_post!(status)
        next
      end

      next unless status.nil?

      status = Status.new(uri: activity_id(entry), url: activity_link(entry), account: account, text: content(entry), created_at: published(entry), updated_at: updated(entry))

      if verb(entry) == :share
        add_reblog!(entry, status)
      elsif verb(entry) == :post
        if thread_id(entry).nil?
          add_post!(entry, status)
        else
          add_reply!(entry, status)
        end
      end

      # If we added a status, go through accounts it mentions and create respective relations
      unless status.new_record?
        entry.xpath('./xmlns:link[@rel="mentioned"]').each do |mention_link|
          # Here we have to do a reverse lookup of local accounts by their URL!
          # It's not pretty at all! I really wish all these protocols sticked to
          # using acct:username@domain only! It would make things so much easier
          # and tidier

          href = Addressable::URI.parse(mention_link.attribute('href').value)

          if href.host == Rails.configuration.x.local_domain
            mentioned_account = Account.find_local(href.path.gsub('/users/', ''))

            unless mentioned_account.nil?
              mentioned_account.mentions.where(status: status).first_or_create(status: status)
            end
          end
        end


        fan_out_on_write_service.(status)
      end
    end
  end

  private

  def add_post!(_entry, status)
    status.save!
  end

  def add_reblog!(entry, status)
    status.reblog = find_original_status(entry, target_id(entry))

    if status.reblog.nil?
      status.reblog = fetch_remote_status(entry)
    end

    status.save! unless status.reblog.nil?
  end

  def add_reply!(entry, status)
    status.thread = find_original_status(entry, thread_id(entry))
    status.save!
  end

  def delete_post!(status)
    status.destroy!
  end

  def find_original_status(_xml, id)
    return nil if id.nil?

    if local_id?(id)
      Status.find(unique_tag_to_local_id(id, 'Status'))
    else
      Status.find_by(uri: id)
    end
  end

  def fetch_remote_status(xml)
    username = xml.at_xpath('./activity:object/xmlns:author/xmlns:name').content
    url      = xml.at_xpath('./activity:object/xmlns:author/xmlns:uri').content
    domain   = Addressable::URI.parse(url).host
    account  = Account.find_by(username: username, domain: domain)

    if account.nil?
      account = follow_remote_account_service.("#{username}@#{domain}", false)
      return nil if account.nil?
    end

    Status.new(account: account, uri: target_id(xml), text: target_content(xml), url: target_url(xml))
  end

  def published(xml)
    xml.at_xpath('./xmlns:published').content
  end

  def updated(xml)
    xml.at_xpath('./xmlns:updated').content
  end

  def content(xml)
    xml.at_xpath('./xmlns:content').content
  end

  def thread_id(xml)
    xml.at_xpath('./thr:in-reply-to').attribute('ref').value
  rescue
    nil
  end

  def target_id(xml)
    xml.at_xpath('.//activity:object/xmlns:id').content
  rescue
    nil
  end

  def activity_id(xml)
    xml.at_xpath('./xmlns:id').content
  end

  def activity_link(xml)
    xml.at_xpath('./xmlns:link[@rel="alternate"]').attribute('href').value
  rescue
    ''
  end

  def target_content(xml)
    xml.at_xpath('.//activity:object/xmlns:content').content
  end

  def target_url(xml)
    xml.at_xpath('.//activity:object/xmlns:link[@rel="alternate"]').attribute('href').value
  end

  def object_type(xml)
    xml.at_xpath('./activity:object-type').content.gsub('http://activitystrea.ms/schema/1.0/', '').to_sym
  rescue
    :note
  end

  def verb(xml)
    xml.at_xpath('./activity:verb').content.gsub('http://activitystrea.ms/schema/1.0/', '').to_sym
  rescue
    :post
  end

  def follow_remote_account_service
    @follow_remote_account_service ||= FollowRemoteAccountService.new
  end

  def update_remote_profile_service
    @update_remote_profile_service ||= UpdateRemoteProfileService.new
  end

  def fan_out_on_write_service
    @fan_out_on_write_service ||= FanOutOnWriteService.new
  end
end