Turn a Mastodon permalink URL into a one-line plain text status

mastodon-parser.rb

require 'nokogiri'
require 'open-uri'
require 'upmark'
require 'cgi'
require 'uri'

class TootReader
  ACTIVITY_NAMESPACE = 'http://activitystrea.ms/spec/1.0/'.freeze
  COMMENT_TYPE = 'http://activitystrea.ms/schema/1.0/comment'.freeze

  def initialize(url)
    @url = url
  end

  def call
    # Just call all these things so that if any of them goes wrong, we get a
    # specific error. This is a bad pattern.

    html_doc
    atom_href
    atom_doc
    atom_type

    @toot = read_toot
    formatted_toot
  end

  def self.call(*args)
    new(*args).call
  end

  private

  attr_reader :url, :toot

  def html_doc
    @html_doc ||= Nokogiri::HTML open(url).read
  rescue => e
    raise "Could not open URL (#{e.class})"
  end

  def atom_href
    @atom_href ||=
      html_doc
      .css('link[rel="alternate"][type="application/atom+xml"]')
      .first['href']
  rescue => e
    raise "Could not find a related Atom document (#{e.class})"
  end

  def atom_doc
    @atom_doc ||= Nokogiri::XML open(atom_href).read
  rescue => e
    raise "Could not load related Atom document (#{e.class})"
  end

  def atom_type
    @atom_type ||=
      atom_doc
      .css('entry')
      .xpath \
        'activity:object-type',
        'activity' => ACTIVITY_NAMESPACE
  rescue => e
    raise "Could not find activity:object-type in Atom document (#{e.class})"
  end

  def read_toot
    unless atom_type && atom_type.text == COMMENT_TYPE
      raise "Related Atom document is an unrecognized type (#{e.class})"
    end

    username = atom_doc.css('author name').text
    author_uri = atom_doc.css('author uri').text
    content = atom_doc.css('entry > content').first.text

    {
      username: username,
      author_uri: author_uri,
      content: content
    }
  end

  def formatted_toot
    full_username = "#{toot[:username]}@#{URI.parse(toot[:author_uri]).host}"
    "#{full_username}: #{CGI.unescapeHTML(Upmark.convert(toot[:content]))}"
  rescue => e
    raise "Could not format toot (#{e.class})"
  end
end

# ruby mastodon-parser.rb https://mastodon.social/@Gargron/3274547

begin
  puts TootReader.call(ARGV.first)
rescue => e
  puts e.message
  exit(1)
end