Add latest changes from gitlab-org/gitlab@master

3 files changed, 91 insertions, 13 deletions

diff --git a/lib/gitlab/diff/file_collection/merge_request_diff.rb b/lib/gitlab/diff/file_collection/merge_request_diff.rb
index e29bf75f341..c4288ca6408 100644
--- a/lib/gitlab/diff/file_collection/merge_request_diff.rb
+++ b/lib/gitlab/diff/file_collection/merge_request_diff.rb
@@ -3,19 +3,7 @@
 module Gitlab
   module Diff
     module FileCollection
-      class MergeRequestDiff < Base
-        extend ::Gitlab::Utils::Override
-
-        def initialize(merge_request_diff, diff_options:)
-          @merge_request_diff = merge_request_diff
-
-          super(merge_request_diff,
-            project: merge_request_diff.project,
-            diff_options: diff_options,
-            diff_refs: merge_request_diff.diff_refs,
-            fallback_diff_refs: merge_request_diff.fallback_diff_refs)
-        end
-
+      class MergeRequestDiff < MergeRequestDiffBase
         def diff_files
           diff_files = super
 
diff --git a/lib/gitlab/diff/file_collection/merge_request_diff_base.rb b/lib/gitlab/diff/file_collection/merge_request_diff_base.rb
new file mode 100644
index 00000000000..a747a6ed475
--- /dev/null
+++ b/lib/gitlab/diff/file_collection/merge_request_diff_base.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Diff
+    module FileCollection
+      class MergeRequestDiffBase < Base
+        extend ::Gitlab::Utils::Override
+
+        def initialize(merge_request_diff, diff_options:)
+          @merge_request_diff = merge_request_diff
+
+          super(merge_request_diff,
+            project: merge_request_diff.project,
+            diff_options: diff_options,
+            diff_refs: merge_request_diff.diff_refs,
+            fallback_diff_refs: merge_request_diff.fallback_diff_refs)
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/diff/file_collection/merge_request_diff_batch.rb b/lib/gitlab/diff/file_collection/merge_request_diff_batch.rb
new file mode 100644
index 00000000000..c6d1e0b93a7
--- /dev/null
+++ b/lib/gitlab/diff/file_collection/merge_request_diff_batch.rb
@@ -0,0 +1,69 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Diff
+    module FileCollection
+      # Builds a paginated diff file collection and collects pagination
+      # metadata.
+      #
+      # It doesn't handle caching yet as we're not prepared to write/read
+      # separate file keys (https://gitlab.com/gitlab-org/gitlab/issues/30550).
+      #
+      class MergeRequestDiffBatch < MergeRequestDiffBase
+        DEFAULT_BATCH_PAGE = 1
+        DEFAULT_BATCH_SIZE = 20
+
+        attr_reader :pagination_data
+
+        def initialize(merge_request_diff, batch_page, batch_size, diff_options:)
+          super(merge_request_diff, diff_options: diff_options)
+
+          batch_page ||= DEFAULT_BATCH_PAGE
+          batch_size ||= DEFAULT_BATCH_SIZE
+
+          @paginated_collection = relation.page(batch_page).per(batch_size)
+          @pagination_data = {
+            current_page: @paginated_collection.current_page,
+            next_page: @paginated_collection.next_page,
+            total_pages: @paginated_collection.total_pages
+          }
+        end
+
+        override :diffs
+        def diffs
+          strong_memoize(:diffs) do
+            @merge_request_diff.opening_external_diff do
+              # Avoiding any extra queries.
+              collection = @paginated_collection.to_a
+
+              # The offset collection and calculation is required so that we
+              # know how much has been loaded in previous batches, collapsing
+              # the current paginated set accordingly (collection limit calculation).
+              # See: https://docs.gitlab.com/ee/development/diffs.html#diff-collection-limits
+              #
+              offset_index = collection.first&.index
+              options = diff_options.dup
+
+              collection =
+                if offset_index && offset_index > 0
+                  offset_collection = relation.limit(offset_index) # rubocop:disable CodeReuse/ActiveRecord
+                  options[:offset_index] = offset_index
+                  offset_collection + collection
+                else
+                  collection
+                end
+
+              Gitlab::Git::DiffCollection.new(collection.map(&:to_hash), options)
+            end
+          end
+        end
+
+        private
+
+        def relation
+          @merge_request_diff.merge_request_diff_files
+        end
+      end
+    end
+  end
+end