discourse/lib/oneboxer.rb

# frozen_string_literal: true

require 'uri'

Dir["#{Rails.root}/lib/onebox/engine/*_onebox.rb"].sort.each { |f| require f }

module Oneboxer
  ONEBOX_CSS_CLASS = "onebox"
  AUDIO_REGEX = /^\.(mp3|og[ga]|opus|wav|m4[abpr]|aac|flac)$/i
  VIDEO_REGEX = /^\.(mov|mp4|webm|m4v|3gp|ogv|avi|mpeg|ogv)$/i

  # keep reloaders happy
  unless defined? Oneboxer::Result
    Result = Struct.new(:doc, :changed) do
      def to_html
        doc.to_html
      end

      def changed?
        changed
      end
    end
  end

  def self.ignore_redirects
    @ignore_redirects ||= ['http://www.dropbox.com', 'http://store.steampowered.com', 'http://vimeo.com', 'https://www.youtube.com', Discourse.base_url]
  end

  def self.amazon_domains
    amazon_suffixes = %w(com com.br ca cn fr de in it co.jp com.mx nl pl sa sg es se com.tr ae co.uk)
    amazon_suffixes.collect { |suffix| "https://www.amazon.#{suffix}" }
  end

  def self.force_get_hosts
    hosts = []
    hosts += SiteSetting.force_get_hosts.split('|').collect { |domain| "https://#{domain}" }
    hosts += SiteSetting.cache_onebox_response_body_domains.split('|').collect { |domain| "https://www.#{domain}" }
    hosts += amazon_domains

    hosts.uniq
  end

  def self.force_custom_user_agent_hosts
    SiteSetting.force_custom_user_agent_hosts.split('|')
  end

  def self.allowed_post_types
    @allowed_post_types ||= [Post.types[:regular], Post.types[:moderator_action]]
  end

  def self.local_handlers
    @local_handlers ||= {}
  end

  def self.register_local_handler(controller, &handler)
    local_handlers[controller] = handler
  end

  def self.preview(url, options = nil)
    options ||= {}
    invalidate(url) if options[:invalidate_oneboxes]
    onebox_raw(url, options)[:preview]
  end

  def self.onebox(url, options = nil)
    options ||= {}
    invalidate(url) if options[:invalidate_oneboxes]
    onebox_raw(url, options)[:onebox]
  end

  def self.cached_onebox(url)
    if c = Discourse.cache.read(onebox_cache_key(url))
      c[:onebox]
    end
  rescue => e
    invalidate(url)
    Rails.logger.warn("invalid cached onebox for #{url} #{e}")
    ""
  end

  def self.cached_preview(url)
    if c = Discourse.cache.read(onebox_cache_key(url))
      c[:preview]
    end
  rescue => e
    invalidate(url)
    Rails.logger.warn("invalid cached preview for #{url} #{e}")
    ""
  end

  def self.invalidate(url)
    Discourse.cache.delete(onebox_cache_key(url))
    Discourse.cache.delete(onebox_failed_cache_key(url))
  end

  def self.cache_response_body?(uri)
    uri = URI.parse(uri) if uri.is_a?(String)

    if SiteSetting.cache_onebox_response_body?
      SiteSetting.cache_onebox_response_body_domains.split("|").any? { |domain| uri.hostname.ends_with?(domain) }
    end
  end

  def self.cache_response_body(uri, response)
    key = redis_cached_response_body_key(uri)
    Discourse.redis.without_namespace.setex(key, 1.minutes.to_i, response)
  end

  def self.cached_response_body_exists?(uri)
    key = redis_cached_response_body_key(uri)
    Discourse.redis.without_namespace.exists(key).to_i > 0
  end

  def self.fetch_cached_response_body(uri)
    key = redis_cached_response_body_key(uri)
    Discourse.redis.without_namespace.get(key)
  end

  def self.redis_cached_response_body_key(uri)
    "CACHED_RESPONSE_#{uri}"
  end

  # Parse URLs out of HTML, returning the document when finished.
  def self.each_onebox_link(doc, extra_paths: [])
    onebox_links = doc.css("a.#{ONEBOX_CSS_CLASS}", *extra_paths)
    if onebox_links.present?
      onebox_links.each do |link|
        yield(link['href'], link) if link['href'].present?
      end
    end

    doc
  end

  HTML5_BLOCK_ELEMENTS ||= %w{address article aside blockquote canvas center dd div dl dt fieldset figcaption figure footer form h1 h2 h3 h4 h5 h6 header hgroup hr li main nav noscript ol output p pre section table tfoot ul video}

  def self.apply(string_or_doc, extra_paths: nil)
    doc = string_or_doc
    doc = Loofah.fragment(doc) if doc.is_a?(String)
    changed = false

    each_onebox_link(doc, extra_paths: extra_paths) do |url, element|
      onebox, _ = yield(url, element)
      next if onebox.blank?

      parsed_onebox = Loofah.fragment(onebox)
      next if parsed_onebox.children.blank?

      changed = true

      parent = element.parent
      if parent&.node_name&.downcase == "p" &&
        parsed_onebox.children.any? { |child| HTML5_BLOCK_ELEMENTS.include?(child.node_name.downcase) }

        siblings = parent.children
        element_idx = siblings.find_index(element)
        before_idx = first_significant_element_index(siblings, element_idx - 1, -1)
        after_idx = first_significant_element_index(siblings, element_idx + 1, +1)

        if before_idx < 0 && after_idx >= siblings.size
          parent.replace parsed_onebox
        elsif before_idx < 0
          parent.children = siblings[after_idx..siblings.size]
          parent.add_previous_sibling(parsed_onebox)
        elsif after_idx >= siblings.size
          parent.children = siblings[0..before_idx]
          parent.add_next_sibling(parsed_onebox)
        else
          parent_rest = parent.dup

          parent.children = siblings[0..before_idx]
          parent_rest.children = siblings[after_idx..siblings.size]

          parent.add_next_sibling(parent_rest)
          parent.add_next_sibling(parsed_onebox)
        end
      else
        element.replace parsed_onebox
      end
    end

    Result.new(doc, changed)
  end

  def self.first_significant_element_index(elements, index, step)
    while index >= 0 && index < elements.size &&
      (elements[index].node_name.downcase == "br" ||
        (elements[index].node_name.downcase == "text" && elements[index].to_html.strip.blank?))
      index = index + step
    end

    index
  end

  def self.is_previewing?(user_id)
    Discourse.redis.get(preview_key(user_id)) == "1"
  end

  def self.preview_onebox!(user_id)
    Discourse.redis.setex(preview_key(user_id), 1.minute, "1")
  end

  def self.onebox_previewed!(user_id)
    Discourse.redis.del(preview_key(user_id))
  end

  def self.engine(url)
    Onebox::Matcher.new(url, {
      allowed_iframe_regexes: Onebox::Engine.origins_to_regexes(allowed_iframe_origins)
    }).oneboxed
  end

  def self.recently_failed?(url)
    Discourse.cache.read(onebox_failed_cache_key(url)).present?
  end

  def self.cache_failed!(url)
    Discourse.cache.write(onebox_failed_cache_key(url), true, expires_in: 1.hour)
  end

  private

  def self.preview_key(user_id)
    "onebox:preview:#{user_id}"
  end

  def self.blank_onebox
    { preview: "", onebox: "" }
  end

  def self.onebox_cache_key(url)
    "onebox__#{url}"
  end

  def self.onebox_failed_cache_key(url)
    "onebox_failed__#{url}"
  end

  def self.onebox_raw(url, opts = {})
    url = UrlHelper.normalized_encode(url).to_s
    local_onebox(url, opts) || external_onebox(url)
  rescue => e
    # no point warning here, just cause we have an issue oneboxing a url
    # we can later hunt for failed oneboxes by searching logs if needed
    Rails.logger.info("Failed to onebox #{url} #{e} #{e.backtrace}")
    # return a blank hash, so rest of the code works
    blank_onebox
  end

  def self.local_onebox(url, opts = {})
    return unless route = Discourse.route_for(url)

    html =
      case route[:controller]
      when "uploads" then local_upload_html(url)
      when "topics"  then local_topic_html(url, route, opts)
      when "users"   then local_user_html(url, route)
      when "list"    then local_category_html(url, route)
      else
        if handler = local_handlers[route[:controller]]
          handler.call(url, route)
        end
      end

    html = html.presence || "<a href='#{URI(url).to_s}'>#{URI(url).to_s}</a>"
    { onebox: html, preview: html }
  end

  def self.local_upload_html(url)
    additional_controls = \
      if SiteSetting.disable_onebox_media_download_controls
        "controlslist='nodownload'"
      else
        ""
      end

    case File.extname(URI(url).path || "")
    when VIDEO_REGEX
      <<~HTML
        <div class="onebox video-onebox">
          <video #{additional_controls} width="100%" height="100%" controls="">
            <source src='#{url}'>
            <a href='#{url}'>#{url}</a>
          </video>
        </div>
      HTML
    when AUDIO_REGEX
      "<audio #{additional_controls} controls><source src='#{url}'><a href='#{url}'>#{url}</a></audio>"
    end
  end

  def self.local_topic(url, route, opts)
    if current_user = User.find_by(id: opts[:user_id])
      if current_category = Category.find_by(id: opts[:category_id])
        return unless Guardian.new(current_user).can_see_category?(current_category)
      end

      if current_topic = Topic.find_by(id: opts[:topic_id])
        return unless Guardian.new(current_user).can_see_topic?(current_topic)
      end
    end

    return unless topic = Topic.find_by(id: route[:id] || route[:topic_id])
    return if topic.private_message?

    if current_category.blank? || current_category.id != topic.category_id
      return unless Guardian.new.can_see_topic?(topic)
    end

    topic
  end

  def self.local_topic_html(url, route, opts)
    return unless topic = local_topic(url, route, opts)

    post_number = route[:post_number].to_i

    post = post_number > 1 ?
      topic.posts.where(post_number: post_number).first :
      topic.ordered_posts.first

    return if !post || post.hidden || !allowed_post_types.include?(post.post_type)

    if post_number > 1 && opts[:topic_id] == topic.id
      excerpt = post.excerpt(SiteSetting.post_onebox_maxlength)
      excerpt.gsub!(/[\r\n]+/, " ")
      excerpt.gsub!("[/quote]", "[quote]") # don't break my quote

      quote = "[quote=\"#{post.user.username}, topic:#{topic.id}, post:#{post.post_number}\"]\n#{excerpt}\n[/quote]"

      PrettyText.cook(quote)
    else
      args = {
        topic_id: topic.id,
        post_number: post.post_number,
        avatar: PrettyText.avatar_img(post.user.avatar_template_url, "tiny"),
        original_url: url,
        title: PrettyText.unescape_emoji(CGI::escapeHTML(topic.title)),
        category_html: CategoryBadge.html_for(topic.category),
        quote: PrettyText.unescape_emoji(post.excerpt(SiteSetting.post_onebox_maxlength)),
      }

      template = template("discourse_topic_onebox")
      Mustache.render(template, args)
    end
  end

  def self.local_user_html(url, route)
    username = route[:username] || ""

    if user = User.find_by(username_lower: username.downcase)

      name = user.name if SiteSetting.enable_names

      args = {
        user_id: user.id,
        username: user.username,
        avatar: PrettyText.avatar_img(user.avatar_template, "extra_large"),
        name: name,
        bio: user.user_profile.bio_excerpt(230),
        location: Onebox::Helpers.sanitize(user.user_profile.location),
        joined: I18n.t('joined'),
        created_at: user.created_at.strftime(I18n.t('datetime_formats.formats.date_only')),
        website: user.user_profile.website,
        website_name: UserSerializer.new(user).website_name,
        original_url: url
      }

      Mustache.render(template("discourse_user_onebox"), args)
    else
      nil
    end
  end

  def self.local_category_html(url, route)
    return unless route[:category_slug_path_with_id]
    category = Category.find_by_slug_path_with_id(route[:category_slug_path_with_id])

    if Guardian.new.can_see_category?(category)
      args = {
        url: category.url,
        name: category.name,
        color: category.color,
        logo_url: category.uploaded_logo&.url,
        description: category.description,
        has_subcategories: category.subcategories.present?,
        subcategories: category.subcategories.collect { |sc| { name: sc.name, color: sc.color, url: sc.url } }
      }

      Mustache.render(template("discourse_category_onebox"), args)
    end
  end

  def self.preserve_fragment_url_hosts
    @preserve_fragment_url_hosts ||= ['http://github.com']
  end

  def self.allowed_iframe_origins
    allowed = SiteSetting.allowed_onebox_iframes.split("|")
    if allowed.include?("*")
      allowed = Onebox::Engine.all_iframe_origins
    end
    allowed += SiteSetting.allowed_iframes.split("|")
  end

  def self.external_onebox(url, available_strategies = nil)
    Discourse.cache.fetch(onebox_cache_key(url), expires_in: 1.day) do
      uri = URI(url)
      available_strategies ||= Oneboxer.ordered_strategies(uri.hostname)
      strategy = available_strategies.shift

      if SiteSetting.block_onebox_on_redirect
        max_redirects = 0
      end
      fd = FinalDestination.new(
        url,
        get_final_destination_options(url, strategy).merge(
          stop_at_blocked_pages: true,
          max_redirects: max_redirects,
          initial_https_redirect_ignore_limit: SiteSetting.block_onebox_on_redirect
        )
      )
      uri = fd.resolve

      return blank_onebox if fd.status == :blocked_page

      if fd.status != :resolved
        args = { link: url }
        if fd.status == :invalid_address
          args[:error_message] = I18n.t("errors.onebox.invalid_address", hostname: fd.hostname)
        elsif (fd.status_code || uri.nil?) && available_strategies.present?
          # Try a different oneboxing strategy, if we have any options left:
          return external_onebox(url, available_strategies)
        elsif fd.status_code
          args[:error_message] = I18n.t("errors.onebox.error_response", status_code: fd.status_code)
        end

        error_box = blank_onebox
        error_box[:preview] = preview_error_onebox(args)
        return error_box
      end

      return blank_onebox if uri.blank?

      onebox_options = {
        max_width: 695,
        sanitize_config: Onebox::SanitizeConfig::DISCOURSE_ONEBOX,
        allowed_iframe_origins: allowed_iframe_origins,
        hostname: GlobalSetting.hostname,
        facebook_app_access_token: SiteSetting.facebook_app_access_token,
        disable_media_download_controls: SiteSetting.disable_onebox_media_download_controls,
        body_cacher: self,
        content_type: fd.content_type
      }

      onebox_options[:cookie] = fd.cookie if fd.cookie

      user_agent_override = SiteSetting.cache_onebox_user_agent if Oneboxer.cache_response_body?(url) && SiteSetting.cache_onebox_user_agent.present?
      onebox_options[:user_agent] = user_agent_override if user_agent_override

      preview_result = Onebox.preview(uri.to_s, onebox_options)
      result = {
        onebox: WordWatcher.censor(preview_result.to_s),
        preview: WordWatcher.censor(preview_result&.placeholder_html.to_s)
      }

      # NOTE: Call preview_result.errors after calling placeholder_html
      if preview_result.errors.any?
        error_keys = preview_result.errors.keys
        skip_if_only_error = [:image]
        unless error_keys.length == 1 && skip_if_only_error.include?(error_keys.first)
          missing_attributes = error_keys.map(&:to_s).sort.join(I18n.t("word_connector.comma"))
          error_message = I18n.t("errors.onebox.missing_data", missing_attributes: missing_attributes, count: error_keys.size)
          args = preview_result.verified_data.merge(error_message: error_message)

          if result[:preview].blank?
            result[:preview] = preview_error_onebox(args)
          else
            doc = Nokogiri::HTML5::fragment(result[:preview])
            aside = doc.at('aside')

            if aside
              # Add an error message to the preview that was returned
              error_fragment = preview_error_onebox_fragment(args)
              aside.add_child(error_fragment)
              result[:preview] = doc.to_html
            end
          end
        end
      end

      Oneboxer.cache_preferred_strategy(uri.hostname, strategy)

      result
    end
  end

  def self.preview_error_onebox(args, is_fragment = false)
    args[:title] ||= args[:link] if args[:link]
    args[:error_message] = PrettyText.unescape_emoji(args[:error_message]) if args[:error_message]

    template_name = is_fragment ? "preview_error_fragment_onebox" : "preview_error_onebox"
    Mustache.render(template(template_name), args)
  end

  def self.preview_error_onebox_fragment(args)
    preview_error_onebox(args, true)
  end

  def self.template(template_name)
    @template_cache ||= {}
    @template_cache[template_name] ||= begin
      full_path = "#{Rails.root}/lib/onebox/templates/#{template_name}.mustache"
      File.read(full_path)
    end
  end

  def self.ordered_strategies(hostname)
    all = strategies.keys
    preferred = Oneboxer.preferred_strategy(hostname)

    all.insert(0, all.delete(preferred)) if all.include?(preferred)

    all
  end

  def self.strategies
    {
      default: {}, # don't override anything by default
      force_get_and_ua: {
        force_get_host: true,
        force_custom_user_agent_host: true,
      },
    }
  end

  def self.cache_preferred_strategy(hostname, strategy)
    return if strategy == :default

    key = redis_oneboxer_strategy_key(hostname)
    Discourse.redis.without_namespace.setex(key, 2.weeks.to_i, strategy.to_s)
  end

  def self.clear_preferred_strategy!(hostname)
    key = redis_oneboxer_strategy_key(hostname)
    Discourse.redis.without_namespace.del(key)
  end

  def self.preferred_strategy(hostname)
    key = redis_oneboxer_strategy_key(hostname)
    Discourse.redis.without_namespace.get(key)&.to_sym
  end

  def self.redis_oneboxer_strategy_key(hostname)
    "ONEBOXER_STRATEGY_#{hostname}"
  end

  def self.get_final_destination_options(url, strategy = nil)
    fd_options = {
      ignore_redirects: ignore_redirects,
      force_get_hosts: force_get_hosts,
      force_custom_user_agent_hosts: force_custom_user_agent_hosts,
      preserve_fragment_url_hosts: preserve_fragment_url_hosts,
      timeout: 5
    }

    uri = URI(url)

    if strategy.blank?
      strategy = Oneboxer.ordered_strategies(uri.hostname).shift
    end

    if strategy && Oneboxer.strategies[strategy][:force_get_host]
      fd_options[:force_get_hosts] = ["https://#{uri.hostname}"]
    end
    if strategy && Oneboxer.strategies[strategy][:force_custom_user_agent_host]
      fd_options[:force_custom_user_agent_hosts] = ["https://#{uri.hostname}"]
    end

    user_agent_override = SiteSetting.cache_onebox_user_agent if Oneboxer.cache_response_body?(url) && SiteSetting.cache_onebox_user_agent.present?
    fd_options[:default_user_agent] = user_agent_override if user_agent_override

    fd_options
  end
end