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# frozen_string_literal: true
class FetchLinkCardService < BaseService
include Redisable
include Lockable
URL_PATTERN = %r{
(#{Twitter::TwitterText::Regex[:valid_url_preceding_chars]}) # $1 preceding chars
( # $2 URL
(https?:\/\/) # $3 Protocol (required)
(#{Twitter::TwitterText::Regex[:valid_domain]}) # $4 Domain(s)
(?::(#{Twitter::TwitterText::Regex[:valid_port_number]}))? # $5 Port number (optional)
(/#{Twitter::TwitterText::Regex[:valid_url_path]}*)? # $6 URL Path and anchor
(\?#{Twitter::TwitterText::Regex[:valid_url_query_chars]}*#{Twitter::TwitterText::Regex[:valid_url_query_ending_chars]})? # $7 Query String
)
}iox
def call(status)
@status = status
@original_url = parse_urls
return if @original_url.nil? || @status.preview_cards.any?
@url = @original_url.to_s
with_lock("fetch:#{@original_url}") do
@card = PreviewCard.find_by(url: @url)
process_url if @card.nil? || @card.updated_at <= 2.weeks.ago || @card.missing_image?
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 #{@original_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|
# We follow redirects, and ideally we want to save the preview card for
# the destination URL and not any link shortener in-between, so here
# we set the URL to the one of the last response in the redirect chain
@url = res.request.uri.to_s
@card = PreviewCard.find_or_initialize_by(url: @url) if @card.url != @url
if res.code == 200 && res.mime_type == 'text/html'
@html_charset = res.charset
@html = res.body_with_limit
else
@html_charset = nil
@html = nil
end
end
end
def attach_card
@status.preview_cards << @card
Rails.cache.delete(@status)
Trends.links.register(@status)
end
def parse_urls
urls = if @status.local?
@status.text.scan(URL_PATTERN).map { |array| Addressable::URI.parse(array[1]).normalize }
else
document = Nokogiri::HTML(@status.text)
links = document.css('a')
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
def mention_link?(anchor)
@status.mentions.any? do |mention|
anchor['href'] == ActivityPub::TagManager.instance.url_for(mention.account)
end
end
def skip_link?(anchor)
# Avoid links for hashtags and mentions (microformats)
anchor['rel']&.include?('tag') || anchor['class']&.match?(/u-url|h-card/) || mention_link?(anchor)
end
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 = Sanitize.fragment(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?
link_details_extractor = LinkDetailsExtractor.new(@url, @html, @html_charset)
@card = PreviewCard.find_or_initialize_by(url: link_details_extractor.canonical_url) if link_details_extractor.canonical_url != @card.url
@card.assign_attributes(link_details_extractor.to_preview_card_attributes)
@card.save_with_optional_image! unless @card.title.blank? && @card.html.blank?
end
end
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