1 files changed, 152 insertions, 0 deletions
diff --git a/lib/banzai/filter/commit_trailers_filter.rb b/lib/banzai/filter/commit_trailers_filter.rb
new file mode 100644
index 00000000000..ef16df1f3ae
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+++ b/lib/banzai/filter/commit_trailers_filter.rb
@@ -0,0 +1,152 @@
+module Banzai
+  module Filter
+    # HTML filter that replaces users' names and emails in commit trailers
+    # with links to their GitLab accounts or mailto links to their mentioned
+    # emails.
+    #
+    # Commit trailers are special labels in the form of `*-by:` and fall on a
+    # single line, ex:
+    #
+    #   Reported-By: John S. Doe <john.doe@foo.bar>
+    #
+    # More info about this can be found here:
+    # * https://git.wiki.kernel.org/index.php/CommitMessageConventions
+    class CommitTrailersFilter < HTML::Pipeline::Filter
+      include ActionView::Helpers::TagHelper
+      include ApplicationHelper
+      include AvatarsHelper
+
+      TRAILER_REGEXP = /(?<label>[[:alpha:]-]+-by:)/i.freeze
+      AUTHOR_REGEXP = /(?<author_name>.+)/.freeze
+      # Devise.email_regexp wouldn't work here since its designed to match
+      # against strings that only contains email addresses; the \A and \z
+      # around the expression will only match if the string being matched
+      # contains just the email nothing else.
+      MAIL_REGEXP = /&lt;(?<author_email>[^@\s]+@[^@\s]+)&gt;/.freeze
+      FILTER_REGEXP = /(?<trailer>^\s*#{TRAILER_REGEXP}\s*#{AUTHOR_REGEXP}\s+#{MAIL_REGEXP}$)/mi.freeze
+
+      def call
+        doc.xpath('descendant-or-self::text()').each do |node|
+          content = node.to_html
+
+          next unless content.match(FILTER_REGEXP)
+
+          html = trailer_filter(content)
+
+          next if html == content
+
+          node.replace(html)
+        end
+
+        doc
+      end
+
+      private
+
+      # Replace trailer lines with links to GitLab users or mailto links to
+      # non GitLab users.
+      #
+      # text - String text to replace trailers in.
+      #
+      # Returns a String with all trailer lines replaced with links to GitLab
+      # users and mailto links to non GitLab users. All links have `data-trailer`
+      # and `data-user` attributes attached.
+      def trailer_filter(text)
+        text.gsub(FILTER_REGEXP) do |author_match|
+          label = $~[:label]
+          "#{label} #{parse_user($~[:author_name], $~[:author_email], label)}"
+        end
+      end
+
+      # Find a GitLab user using the supplied email and generate
+      # a valid link to them, otherwise, generate a mailto link.
+      #
+      # name - String name used in the commit message for the user
+      # email - String email used in the commit message for the user
+      # trailer - String trailer used in the commit message
+      #
+      # Returns a String with a link to the user.
+      def parse_user(name, email, trailer)
+        link_to_user User.find_by_any_email(email),
+          name: name,
+          email: email,
+          trailer: trailer
+      end
+
+      def urls
+        Gitlab::Routing.url_helpers
+      end
+
+      def link_to_user(user, name:, email:, trailer:)
+        wrapper = link_wrapper(data: {
+          trailer: trailer,
+          user: user.try(:id)
+        })
+
+        avatar = user_avatar_without_link(
+          user: user,
+          user_email: email,
+          css_class: 'avatar-inline',
+          has_tooltip: false
+        )
+
+        link_href = user.nil? ? "mailto:#{email}" : urls.user_url(user)
+
+        avatar_link = link_tag(
+          link_href,
+          content: avatar,
+          title: email
+        )
+
+        name_link = link_tag(
+          link_href,
+          content: name,
+          title: email
+        )
+
+        email_link = link_tag(
+          "mailto:#{email}",
+          content: email,
+          title: email
+        )
+
+        wrapper << "#{avatar_link}#{name_link} <#{email_link}>"
+      end
+
+      def link_wrapper(data: {})
+        data_attributes = data_attributes_from_hash(data)
+
+        doc.document.create_element(
+          'span',
+          data_attributes
+        )
+      end
+
+      def link_tag(url, title: "", content: "", data: {})
+        data_attributes = data_attributes_from_hash(data)
+
+        attributes = data_attributes.merge(
+          href: url,
+          title: title
+        )
+
+        link = doc.document.create_element('a', attributes)
+
+        if content.html_safe?
+          link << content
+        else
+          link.content = content # make sure we escape content using nokogiri's #content=
+        end
+
+        link
+      end
+
+      def data_attributes_from_hash(data = {})
+        data.reject! {|_, value| value.nil?}
+        data.map do |key, value|
+          [%(data-#{key.to_s.dasherize}), value]
+        end.to_h
+      end
+    end
+  end
+end