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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
end
end
attach_card if @card&.persisted?
rescue HTTP::Error, Addressable::URI::InvalidURIError => e
Rails.logger.debug "Error fetching link #{@url}: #{e}"
nil
end
private
def process_url
@card ||= PreviewCard.new(url: @url)
res = Request.new(:head, @url).perform
return if res.code != 405 && (res.code != 200 || res.mime_type != 'text/html')
attempt_oembed || attempt_opengraph
end
def attach_card
@status.preview_cards << @card
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.map { |a| Addressable::URI.parse(a['href']).normalize unless skip_link?(a) }.compact
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 skip_link?(a)
# Avoid links for hashtags and mentions (microformats)
a['rel']&.include?('tag') || a['class']&.include?('u-url')
end
def attempt_oembed
response = OEmbed::Providers.get(@url)
return false unless response.respond_to?(:type)
@card.type = response.type
@card.title = response.respond_to?(:title) ? response.title : ''
@card.author_name = response.respond_to?(:author_name) ? response.author_name : ''
@card.author_url = response.respond_to?(:author_url) ? response.author_url : ''
@card.provider_name = response.respond_to?(:provider_name) ? response.provider_name : ''
@card.provider_url = response.respond_to?(:provider_url) ? response.provider_url : ''
@card.width = 0
@card.height = 0
case @card.type
when 'link'
@card.image = URI.parse(response.thumbnail_url) if response.respond_to?(:thumbnail_url)
when 'photo'
@card.embed_url = response.url
@card.width = response.width.presence || 0
@card.height = response.height.presence || 0
when 'video'
@card.width = response.width.presence || 0
@card.height = response.height.presence || 0
@card.html = Formatter.instance.sanitize(response.html, Sanitize::Config::MASTODON_OEMBED)
when 'rich'
# Most providers rely on <script> tags, which is a no-no
return false
end
@card.save_with_optional_image!
rescue OEmbed::NotFound
false
end
def attempt_opengraph
response = Request.new(:get, @url).perform
return if response.code != 200 || response.mime_type != 'text/html'
html = response.to_s
detector = CharlockHolmes::EncodingDetector.new
detector.strip_tags = true
guess = detector.detect(html, response.charset)
page = Nokogiri::HTML(html, nil, guess&.fetch(:encoding, nil))
if meta_property(page, 'twitter:player')
@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: meta_property(page, 'twitter:player'),
width: @card.width,
height: @card.height,
allowtransparency: 'true',
scrolling: 'no',
frameborder: '0')
else
@card.type = :link
@card.image_remote_url = meta_property(page, 'og:image') if meta_property(page, 'og:image')
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') || ''
return if @card.title.blank? && @card.html.blank?
@card.save_with_optional_image!
end
def meta_property(html, property)
html.at_xpath("//meta[@property=\"#{property}\"]")&.attribute('content')&.value || html.at_xpath("//meta[@name=\"#{property}\"]")&.attribute('content')&.value
end
def lock_options
{ redis: Redis.current, key: "fetch:#{@url}" }
end
end
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