Federated social network node, running on kosmos.social https://kosmos.social
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# frozen_string_literal: true
class FetchLinkCardService < BaseService
URL_PATTERN = %r{
( # $1 URL
(https?:\/\/) # $2 Protocol (required)
(#{Twitter::Regex[:valid_domain]}) # $3 Domain(s)
(?::(#{Twitter::Regex[:valid_port_number]}))? # $4 Port number (optional)
(/#{Twitter::Regex[:valid_url_path]}*)? # $5 URL Path and anchor
(\?#{Twitter::Regex[:valid_url_query_chars]}*#{Twitter::Regex[:valid_url_query_ending_chars]})? # $6 Query String
)
}iox
def call(status)
@status = status
@url = parse_urls
return if @url.nil? || @status.preview_cards.any?
@url = @url.to_s
RedisLock.acquire(lock_options) do |lock|
if lock.acquired?
@card = PreviewCard.find_by(url: @url)
process_url if @card.nil? || @card.updated_at <= 2.weeks.ago || @card.missing_image?
else
raise Mastodon::RaceConditionError
end
end
attach_card if @card&.persisted?
rescue HTTP::Error, OpenSSL::SSL::SSLError, Addressable::URI::InvalidURIError, Mastodon::HostValidationError, Mastodon::LengthValidationError => e
Rails.logger.debug "Error fetching link #{@url}: #{e}"
nil
end
private
def process_url
@card ||= PreviewCard.new(url: @url)
attempt_oembed || attempt_opengraph
end
def html
return @html if defined?(@html)
Request.new(:get, @url).add_headers('Accept' => 'text/html', 'User-Agent' => Mastodon::Version.user_agent + ' Bot').perform do |res|
if res.code == 200 && res.mime_type == 'text/html'
@html = res.body_with_limit
@html_charset = res.charset
else
@html = nil
@html_charset = nil
end
end
end
def attach_card
@status.preview_cards << @card
Rails.cache.delete(@status)
end
def parse_urls
if @status.local?
urls = @status.text.scan(URL_PATTERN).map { |array| Addressable::URI.parse(array[0]).normalize }
else
html = Nokogiri::HTML(@status.text)
links = html.css('a')
urls = links.filter_map { |a| Addressable::URI.parse(a['href']) unless skip_link?(a) }.filter_map(&:normalize)
end
urls.reject { |uri| bad_url?(uri) }.first
end
def bad_url?(uri)
# Avoid local instance URLs and invalid URLs
uri.host.blank? || TagManager.instance.local_url?(uri.to_s) || !%w(http https).include?(uri.scheme)
end
# rubocop:disable Naming/MethodParameterName
def mention_link?(a)
@status.mentions.any? do |mention|
a['href'] == ActivityPub::TagManager.instance.url_for(mention.account)
end
end
def skip_link?(a)
# Avoid links for hashtags and mentions (microformats)
a['rel']&.include?('tag') || a['class']&.match?(/u-url|h-card/) || mention_link?(a)
end
# rubocop:enable Naming/MethodParameterName
def attempt_oembed
service = FetchOEmbedService.new
url_domain = Addressable::URI.parse(@url).normalized_host
cached_endpoint = Rails.cache.read("oembed_endpoint:#{url_domain}")
embed = service.call(@url, cached_endpoint: cached_endpoint) unless cached_endpoint.nil?
embed ||= service.call(@url, html: html) unless html.nil?
return false if embed.nil?
url = Addressable::URI.parse(service.endpoint_url)
@card.type = embed[:type]
@card.title = embed[:title] || ''
@card.author_name = embed[:author_name] || ''
@card.author_url = embed[:author_url].present? ? (url + embed[:author_url]).to_s : ''
@card.provider_name = embed[:provider_name] || ''
@card.provider_url = embed[:provider_url].present? ? (url + embed[:provider_url]).to_s : ''
@card.width = 0
@card.height = 0
case @card.type
when 'link'
@card.image_remote_url = (url + embed[:thumbnail_url]).to_s if embed[:thumbnail_url].present?
when 'photo'
return false if embed[:url].blank?
@card.embed_url = (url + embed[:url]).to_s
@card.image_remote_url = (url + embed[:url]).to_s
@card.width = embed[:width].presence || 0
@card.height = embed[:height].presence || 0
when 'video'
@card.width = embed[:width].presence || 0
@card.height = embed[:height].presence || 0
@card.html = Formatter.instance.sanitize(embed[:html], Sanitize::Config::MASTODON_OEMBED)
@card.image_remote_url = (url + embed[:thumbnail_url]).to_s if embed[:thumbnail_url].present?
when 'rich'
# Most providers rely on <script> tags, which is a no-no
return false
end
@card.save_with_optional_image!
end
def attempt_opengraph
return if html.nil?
detector = CharlockHolmes::EncodingDetector.new
detector.strip_tags = true
guess = detector.detect(@html, @html_charset)
encoding = guess&.fetch(:confidence, 0).to_i > 60 ? guess&.fetch(:encoding, nil) : nil
page = Nokogiri::HTML(@html, nil, encoding)
player_url = meta_property(page, 'twitter:player')
if player_url && !bad_url?(Addressable::URI.parse(player_url))
@card.type = :video
@card.width = meta_property(page, 'twitter:player:width') || 0
@card.height = meta_property(page, 'twitter:player:height') || 0
@card.html = content_tag(:iframe, nil, src: player_url,
width: @card.width,
height: @card.height,
allowtransparency: 'true',
scrolling: 'no',
frameborder: '0')
else
@card.type = :link
end
@card.title = meta_property(page, 'og:title').presence || page.at_xpath('//title')&.content || ''
@card.description = meta_property(page, 'og:description').presence || meta_property(page, 'description') || ''
@card.image_remote_url = (Addressable::URI.parse(@url) + meta_property(page, 'og:image')).to_s if meta_property(page, 'og:image')
return if @card.title.blank? && @card.html.blank?
@card.save_with_optional_image!
end
def meta_property(page, property)
page.at_xpath("//meta[contains(concat(' ', normalize-space(@property), ' '), ' #{property} ')]")&.attribute('content')&.value || page.at_xpath("//meta[@name=\"#{property}\"]")&.attribute('content')&.value
end
def lock_options
{ redis: Redis.current, key: "fetch:#{@url}" }
end
end