A script to generate an RSS feed for a Letterboxd watchlist.

watchlist2rss.rb

@username = # Enter username as a String
  
# Editing below this line should not be required
  
require 'net/http'
require 'rss'
require 'uri'
  
class Watchlist
  PATTERNS = {
    title: /<meta property="og:title" content="([^"]+)" \/>/,
    desc: /<meta property="og:description" content="([^"]+)" \/>/,
    imdb: /<a href="([^"]+)maindetails" [^>]+ data-track-action="IMDb">/,                                                       poster: /(<div\s(?:[^>]+\s+)*class=["|'](?:[^"|']+\s+)*poster(?:\s+[^"|']+)*["|'](?:\s+[^>]+)*>)/im,
    link: /data\-target\-link="([^"]+)"/
  }
  
  def initialize(username:)
    @username = username
  end
  
  def rss()                                 
    RSS::Maker.make("rss2.0") do |maker|
      maker.channel.title = "Letterboxd Watchlist for @#{@username}"                                                        
      maker.channel.link = "https://letterboxd.com/#{@username}/watchlist/"
      maker.channel.description = "An RSS feed of the movies in the Letterboxd Watchlist for @#{@username}."
      maker.channel.generator = "Ruby #{RUBY_VERSION}-p#{RUBY_PATCHLEVEL}"
      maker.channel.lastBuildDate = Time.now.to_s
      
      movies.each do |movie|
        maker.items.new_item do |item|
          item.title = movie[:title]
          item.link = movie[:imdb_url]
          item.description = movie[:description]
          item.guid.yield_self do |guid|
            guid.permanent_link = false
            guid.content = movie[:imdb_url]
          end
        end
      end
    end
  end
  
  def movies()
    movie_pages.map do |page|
      { title: attr_title(page), 
        description: attr_desc(page), 
        imdb_url: attr_imdb(page) }
    end
  end

  private def attr_title(html)
    first_match html, PATTERNS[:title]
  end

  private def attr_desc(html)
    first_match html, PATTERNS[:desc]
  end

  private def attr_imdb(html)
    first_match html, PATTERNS[:imdb]
  end

  private def first_match(string, pattern)
    result = string.match(pattern)
    raise unless result
    result[1]
  rescue
    msg = "The pattern #{pattern} did not match in the following:\n\n#{string}"
    raise msg
  end
  
  private def movie_pages()
    movie_urls.map { |url| read url }
  end

  private def movie_urls()
    html = read "#{@username}/watchlist/"
    results = html.scan PATTERNS[:poster]
    results.map { |result| first_match(result[0], PATTERNS[:link]) }
  end

  private def read(fragment)
    base_url = 'https://letterboxd.com/'
    Net::HTTP.get(URI.parse(base_url + fragment))
  end
end

rss = Watchlist.new(username: @username).rss
File.write 'feed.xml', rss