1 files changed, 58 insertions, 0 deletions
diff --git a/lib/gitlab/diff/custom_diff.rb b/lib/gitlab/diff/custom_diff.rb
new file mode 100644
index 00000000000..3928ece9281
--- /dev/null
+++ b/lib/gitlab/diff/custom_diff.rb
@@ -0,0 +1,58 @@
+# frozen_string_literal: true
+module Gitlab
+  module Diff
+    module CustomDiff
+      class << self
+        def preprocess_before_diff(path, old_blob, new_blob)
+          return unless path.ends_with? '.ipynb'
+
+          transformed_diff(old_blob&.data, new_blob&.data)&.tap do
+            transformed_for_diff(new_blob, old_blob)
+            Gitlab::AppLogger.info({ message: 'IPYNB_DIFF_GENERATED' })
+          end
+        rescue IpynbDiff::InvalidNotebookError => e
+          Gitlab::ErrorTracking.log_exception(e)
+          nil
+        end
+
+        def transformed_diff(before, after)
+          transformed_diff = IpynbDiff.diff(before, after,
+                                            diff_opts: { context: 5, include_diff_info: true },
+                                            transform_options: { cell_decorator: :percent },
+                                            raise_if_invalid_notebook: true)
+          strip_diff_frontmatter(transformed_diff)
+        end
+
+        def transformed_blob_language(blob)
+          'md' if transformed_for_diff?(blob)
+        end
+
+        def transformed_blob_data(blob)
+          if transformed_for_diff?(blob)
+            IpynbDiff.transform(blob.data,
+                                raise_errors: true,
+                                options: { include_metadata: false, cell_decorator: :percent })
+          end
+        end
+
+        def strip_diff_frontmatter(diff_content)
+          diff_content.scan(/.*\n/)[2..]&.join('') if diff_content.present?
+        end
+
+        def blobs_with_transformed_diffs
+          @blobs_with_transformed_diffs ||= {}
+        end
+
+        def transformed_for_diff?(blob)
+          blobs_with_transformed_diffs[blob]
+        end
+
+        def transformed_for_diff(*blobs)
+          blobs.each do |b|
+            blobs_with_transformed_diffs[b] = true if b
+          end
+        end
+      end
+    end
+  end
+end