mastodon/app/lib/link_details_extractor.rb

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# frozen_string_literal: true
class LinkDetailsExtractor
include ActionView::Helpers::TagHelper
include LanguagesHelper
# Some publications wrap their JSON-LD data in their <script> tags
# in commented-out CDATA blocks, they need to be removed before
# attempting to parse JSON
CDATA_JUNK_PATTERN = %r{^\s*(
(/\*\s*<!\[CDATA\[\s*\*/) # Block comment style opening
|
(//\s*<!\[CDATA\[) # Single-line comment style opening
|
(/\*\s*\]\]>\s*\*/) # Block comment style closing
|
(//\s*\]\]>) # Single-line comment style closing
)\s*$}x
class StructuredData
SUPPORTED_TYPES = %w(
NewsArticle
WebPage
).freeze
def initialize(data)
@data = data
end
def headline
json['headline']
end
def description
json['description']
end
def language
lang = json['inLanguage']
lang = lang.first if lang.is_a?(Array)
lang.is_a?(Hash) ? (lang['alternateName'] || lang['name']) : lang
end
def type
json['@type']
end
def image
obj = first_of_value(json['image'])
return obj['url'] if obj.is_a?(Hash)
obj
end
def date_published
json['datePublished']
end
def date_modified
json['dateModified']
end
def author_name
author['name']
end
def author_url
author['url']
end
def publisher_name
publisher['name']
end
def publisher_logo
publisher.dig('logo', 'url')
end
def valid?
json.present?
end
private
def author
first_of_value(json['author']) || {}
end
def publisher
first_of_value(json['publisher']) || {}
end
def first_of_value(arr)
arr.is_a?(Array) ? arr.first : arr
end
def root_array(root)
root.is_a?(Array) ? root : [root]
end
def json
@json ||= root_array(Oj.load(@data)).find { |obj| SUPPORTED_TYPES.include?(obj['@type']) } || {}
end
end
def initialize(original_url, html, html_charset)
@original_url = Addressable::URI.parse(original_url)
@html = html
@html_charset = html_charset
end
def to_preview_card_attributes
{
title: title || '',
description: description || '',
image_remote_url: image,
image_description: image_alt || '',
type: type,
link_type: link_type,
width: width || 0,
height: height || 0,
html: html || '',
provider_name: provider_name || '',
provider_url: provider_url || '',
author_name: author_name || '',
author_url: author_url || '',
embed_url: embed_url || '',
language: language,
published_at: published_at.presence,
}
end
def type
player_url.present? ? :video : :link
end
def link_type
if structured_data&.type == 'NewsArticle' || opengraph_tag('og:type') == 'article'
:article
else
:unknown
end
end
def html
player_url.present? ? content_tag(:iframe, nil, src: player_url, width: width, height: height, allowfullscreen: 'true', allowtransparency: 'true', scrolling: 'no', frameborder: '0') : nil
end
def width
opengraph_tag('twitter:player:width')
end
def height
opengraph_tag('twitter:player:height')
end
def title
html_entities.decode(structured_data&.headline || opengraph_tag('og:title') || document.xpath('//title').map(&:content).first)
end
def description
html_entities.decode(structured_data&.description || opengraph_tag('og:description') || meta_tag('description'))
end
def published_at
structured_data&.date_published || opengraph_tag('article:published_time')
end
def image
valid_url_or_nil(opengraph_tag('og:image'))
end
def image_alt
opengraph_tag('og:image:alt')
end
def canonical_url
valid_url_or_nil(link_tag('canonical') || opengraph_tag('og:url'), same_origin_only: true) || @original_url.to_s
end
def provider_name
html_entities.decode(structured_data&.publisher_name || opengraph_tag('og:site_name'))
end
def provider_url
valid_url_or_nil(host_to_url(opengraph_tag('og:site')))
end
def author_name
html_entities.decode(structured_data&.author_name || opengraph_tag('og:author') || opengraph_tag('og:author:username'))
end
def author_url
structured_data&.author_url
end
def embed_url
valid_url_or_nil(opengraph_tag('twitter:player:stream'))
end
def language
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valid_locale_or_nil(structured_data&.language || opengraph_tag('og:locale') || document.xpath('//html').pick('lang'))
end
def icon
valid_url_or_nil(structured_data&.publisher_icon || link_tag('apple-touch-icon') || link_tag('shortcut icon'))
end
private
def player_url
valid_url_or_nil(opengraph_tag('twitter:player'))
end
def host_to_url(str)
return if str.blank?
str.start_with?(%r{https?://}) ? str : "http://#{str}"
end
def valid_url_or_nil(str, same_origin_only: false)
return if str.blank? || str == 'null'
url = @original_url + Addressable::URI.parse(str)
return if url.host.blank? || !%w(http https).include?(url.scheme) || (same_origin_only && url.host != @original_url.host)
url.to_s
rescue Addressable::URI::InvalidURIError
nil
end
def link_tag(name)
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document.xpath("//link[@rel=\"#{name}\"]").pick('href')
end
def opengraph_tag(name)
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document.xpath("//meta[@property=\"#{name}\" or @name=\"#{name}\"]").pick('content')
end
def meta_tag(name)
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document.xpath("//meta[@name=\"#{name}\"]").pick('content')
end
def structured_data
# Some publications have more than one JSON-LD definition on the page,
# and some of those definitions aren't valid JSON either, so we have
# to loop through here until we find something that is the right type
# and doesn't break
@structured_data ||= document.xpath('//script[@type="application/ld+json"]').filter_map do |element|
json_ld = element.content&.gsub(CDATA_JUNK_PATTERN, '')
next if json_ld.blank?
structured_data = StructuredData.new(html_entities.decode(json_ld))
next unless structured_data.valid?
structured_data
rescue Oj::ParseError, EncodingError
Rails.logger.debug { "Invalid JSON-LD in #{@original_url}" }
next
end.first
end
def document
@document ||= Nokogiri::HTML(@html, nil, encoding)
end
def encoding
@encoding ||= begin
guess = detector.detect(@html, @html_charset)
guess&.fetch(:confidence, 0).to_i > 60 ? guess&.fetch(:encoding, nil) : nil
end
end
def detector
@detector ||= CharlockHolmes::EncodingDetector.new.tap do |detector|
detector.strip_tags = true
end
end
def html_entities
@html_entities ||= HTMLEntities.new
end
end