1 files changed, 109 insertions, 0 deletions
diff --git a/lib/gitlab/dependency_linker/base_linker.rb b/lib/gitlab/dependency_linker/base_linker.rb
new file mode 100644
index 00000000000..5f4027e7e81
--- /dev/null
+++ b/lib/gitlab/dependency_linker/base_linker.rb
@@ -0,0 +1,109 @@
+module Gitlab
+  module DependencyLinker
+    class BaseLinker
+      class_attribute :file_type
+
+      def self.support?(blob_name)
+        Gitlab::FileDetector.type_of(blob_name) == file_type
+      end
+
+      def self.link(*args)
+        new(*args).link
+      end
+
+      attr_accessor :plain_text, :highlighted_text
+
+      def initialize(plain_text, highlighted_text)
+        @plain_text = plain_text
+        @highlighted_text = highlighted_text
+      end
+
+      def link
+        link_dependencies
+
+        highlighted_lines.join.html_safe
+      end
+
+      private
+
+      def package_url(name)
+        raise NotImplementedError
+      end
+
+      def link_dependencies
+        raise NotImplementedError
+      end
+
+      def package_link(name, url = package_url(name))
+        return name unless url
+
+        %{<a href="#{ERB::Util.html_escape_once(url)}" rel="noopener noreferrer" target="_blank">#{ERB::Util.html_escape_once(name)}</a>}
+      end
+
+      # Links package names in a method call or assignment string argument.
+      #
+      # Example:
+      #   link_method_call("gem")
+      #   # Will link `package` in `gem "package"`, `gem("package")` and `gem = "package"`
+      #
+      #   link_method_call("gem", "specific_package")
+      #   # Will link `specific_package` in `gem "specific_package"`
+      #
+      #   link_method_call("github", /[^\/]+\/[^\/]+/)
+      #   # Will link `user/repo` in `github "user/repo"`, but not `github "package"`
+      #
+      #   link_method_call(%w[add_dependency add_development_dependency])
+      #   # Will link `spec.add_dependency "package"` and `spec.add_development_dependency "package"`
+      #
+      #   link_method_call("name")
+      #   # Will link `package` in `self.name = "package"`
+      def link_method_call(method_names, value = nil, &url_proc)
+        value =
+          case value
+          when String
+            Regexp.escape(value)
+          when nil
+            /[^'"]+/
+          else
+            value
+          end
+
+        method_names = Array(method_names).map { |name| Regexp.escape(name) }
+
+        regex = %r{
+          #{Regexp.union(method_names)} # Method name
+          \s*                           # Whitespace
+          [(=]?                         # Opening brace or equals sign
+          \s*                           # Whitespace
+          ['"](?<name>#{value})['"]     # Package name in quotes
+        }x
+
+        link_regex(regex, &url_proc)
+      end
+
+      # Links package names based on regex.
+      #
+      # Example:
+      #   link_regex(/(github:|:github =>)\s*['"](?<name>[^'"]+)['"]/)
+      #   # Will link `user/repo` in `github: "user/repo"` or `:github => "user/repo"`
+      def link_regex(regex)
+        highlighted_lines.map!.with_index do |rich_line, i|
+          marker = StringRegexMarker.new(plain_lines[i], rich_line.html_safe)
+
+          marker.mark(regex, group: :name) do |text, left:, right:|
+            url = block_given? ? yield(text) : package_url(text)
+            package_link(text, url)
+          end
+        end
+      end
+
+      def plain_lines
+        @plain_lines ||= plain_text.lines
+      end
+
+      def highlighted_lines
+        @highlighted_lines ||= highlighted_text.lines
+      end
+    end
+  end
+end