1 files changed, 46 insertions, 0 deletions
diff --git a/lib/gitlab/utils/link_header_parser.rb b/lib/gitlab/utils/link_header_parser.rb
new file mode 100644
index 00000000000..d98c237baf3
--- /dev/null
+++ b/lib/gitlab/utils/link_header_parser.rb
@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Utils
+    # Parses Link http headers (as defined in https://www.rfc-editor.org/rfc/rfc5988.txt)
+    #
+    # The URI-references with their relation type are extracted and returned as a hash
+    # Example:
+    #
+    # header = '<http://test.org/TheBook/chapter2>; rel="previous", <http://test.org/TheBook/chapter4>; rel="next"'
+    #
+    # Gitlab::Utils::LinkHeaderParser.new(header).parse
+    # {
+    #   previous: {
+    #     uri: #<URI::HTTP http://test.org/TheBook/chapter2>
+    #   },
+    #   next: {
+    #     uri: #<URI::HTTP http://test.org/TheBook/chapter4>
+    #   }
+    # }
+    class LinkHeaderParser
+      REL_PATTERN = %r{rel="(\w+)"}.freeze
+      # to avoid parse really long URIs we limit the amount of characters allowed
+      URI_PATTERN = %r{<(.{1,500})>}.freeze
+
+      def initialize(header)
+        @header = header
+      end
+
+      def parse
+        return {} if @header.blank?
+
+        links = @header.split(',')
+        result = {}
+        links.each do |link|
+          direction = link[REL_PATTERN, 1]&.to_sym
+          uri = link[URI_PATTERN, 1]
+
+          result[direction] = { uri: URI(uri) } if direction && uri
+        end
+
+        result
+      end
+    end
+  end
+end