1 files changed, 249 insertions, 0 deletions
diff --git a/app/lib/link_details_extractor.rb b/app/lib/link_details_extractor.rb
new file mode 100644
index 000000000..56ad0717b
--- /dev/null
+++ b/app/lib/link_details_extractor.rb
@@ -0,0 +1,249 @@
+# frozen_string_literal: true
+
+class LinkDetailsExtractor
+  include ActionView::Helpers::TagHelper
+
+  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
+      json['inLanguage']
+    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
+
+    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,
+      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,
+    }
+  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, 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
+    structured_data&.headline || opengraph_tag('og:title') || document.xpath('//title').map(&:content).first
+  end
+
+  def description
+    structured_data&.description || opengraph_tag('og:description') || meta_tag('description')
+  end
+
+  def image
+    valid_url_or_nil(opengraph_tag('og:image'))
+  end
+
+  def canonical_url
+    valid_url_or_nil(opengraph_tag('og:url') || link_tag('canonical'), same_origin_only: true) || @original_url.to_s
+  end
+
+  def provider_name
+    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
+    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
+    valid_locale_or_nil(structured_data&.language || opengraph_tag('og:locale') || document.xpath('//html').map { |element| element['lang'] }.first)
+  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?(/https?:\/\//) ? str : "http://#{str}"
+  end
+
+  def valid_url_or_nil(str, same_origin_only: false)
+    return if str.blank?
+
+    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 valid_locale_or_nil(str)
+    return nil if str.blank?
+
+    code,  = str.split(/_-/) # Strip out the region from e.g. en_US or ja-JA
+    locale = ISO_639.find(code)
+    locale&.alpha2
+  end
+
+  def link_tag(name)
+    document.xpath("//link[@rel=\"#{name}\"]").map { |link| link['href'] }.first
+  end
+
+  def opengraph_tag(name)
+    document.xpath("//meta[@property=\"#{name}\" or @name=\"#{name}\"]").map { |meta| meta['content'] }.first
+  end
+
+  def meta_tag(name)
+    document.xpath("//meta[@name=\"#{name}\"]").map { |meta| meta['content'] }.first
+  end
+
+  def structured_data
+    @structured_data ||= begin
+      json_ld = document.xpath('//script[@type="application/ld+json"]').map(&:content).first
+      json_ld.present? ? StructuredData.new(json_ld) : nil
+    rescue Oj::ParseError
+      nil
+    end
+  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
+end