1 files changed, 94 insertions, 0 deletions
diff --git a/lib/gitlab/markdown/external_issue_reference_filter.rb b/lib/gitlab/markdown/external_issue_reference_filter.rb
new file mode 100644
index 00000000000..87f58b1ae79
--- /dev/null
+++ b/lib/gitlab/markdown/external_issue_reference_filter.rb
@@ -0,0 +1,94 @@
+require 'html/pipeline'
+
+module Gitlab
+  module Markdown
+    # HTML filter that replaces external issue tracker references with links.
+    # References within <pre>, <code>, <a>, and <style> elements are ignored.
+    #
+    # Context options:
+    #   :project (required) - Current project.
+    #   :reference_class    - Custom CSS class added to reference links.
+    #   :only_path          - Generate path-only links.
+    #
+    class ExternalIssueReferenceFilter < HTML::Pipeline::Filter
+      # Public: Find `JIRA-123` issue references in text
+      #
+      #   ExternalIssueReferenceFilter.references_in(text) do |match, issue|
+      #     "<a href=...>##{issue}</a>"
+      #   end
+      #
+      # text - String text to search.
+      #
+      # Yields the String match and the String issue reference.
+      #
+      # Returns a String replaced with the return of the block.
+      def self.references_in(text)
+        text.gsub(ISSUE_PATTERN) do |match|
+          yield match, $~[:issue]
+        end
+      end
+
+      # Pattern used to extract `JIRA-123` issue references from text
+      ISSUE_PATTERN = /(?<issue>([A-Z\-]+-)\d+)/
+
+      # Don't look for references in text nodes that are children of these
+      # elements.
+      IGNORE_PARENTS = %w(pre code a style).to_set
+
+      def call
+        doc.search('text()').each do |node|
+          content = node.to_html
+
+          next if project.nil?
+          next if project.default_issues_tracker?
+          next unless content.match(ISSUE_PATTERN)
+          next if has_ancestor?(node, IGNORE_PARENTS)
+
+          html = issue_link_filter(content)
+
+          next if html == content
+
+          node.replace(html)
+        end
+
+        doc
+      end
+
+      def validate
+        needs :project
+      end
+
+      # Replace `JIRA-123` issue references in text with links to the referenced
+      # issue's details page.
+      #
+      # text - String text to replace references in.
+      #
+      # Returns a String with `JIRA-123` references replaced with links. All
+      # links have `gfm` and `gfm-issue` class names attached for styling.
+      def issue_link_filter(text)
+        project = context[:project]
+
+        self.class.references_in(text) do |match, issue|
+          url = url_for_issue(issue, project, only_path: context[:only_path])
+
+          title = "Issue in #{project.external_issue_tracker.title}"
+          klass = "gfm gfm-issue #{context[:reference_class]}".strip
+
+          %(<a href="#{url}"
+               title="#{title}"
+               class="#{klass}">#{issue}</a>)
+        end
+      end
+
+      # TODO (rspeicher): Duplicates IssueReferenceFilter
+      def project
+        context[:project]
+      end
+
+      # TODO (rspeicher): Duplicates IssueReferenceFilter
+      def url_for_issue(*args)
+        IssuesHelper.url_for_issue(*args)
+      end
+    end
+  end
+end