1 files changed, 64 insertions, 0 deletions
diff --git a/lib/gitlab/verify/batch_verifier.rb b/lib/gitlab/verify/batch_verifier.rb
new file mode 100644
index 00000000000..1ef369a4b67
--- /dev/null
+++ b/lib/gitlab/verify/batch_verifier.rb
@@ -0,0 +1,64 @@
+module Gitlab
+  module Verify
+    class BatchVerifier
+      attr_reader :batch_size, :start, :finish
+
+      def initialize(batch_size:, start: nil, finish: nil)
+        @batch_size = batch_size
+        @start = start
+        @finish = finish
+      end
+
+      # Yields a Range of IDs and a Hash of failed verifications (object => error)
+      def run_batches(&blk)
+        relation.in_batches(of: batch_size, start: start, finish: finish) do |relation| # rubocop: disable Cop/InBatches
+          range = relation.first.id..relation.last.id
+          failures = run_batch(relation)
+
+          yield(range, failures)
+        end
+      end
+
+      def name
+        raise NotImplementedError.new
+      end
+
+      def describe(_object)
+        raise NotImplementedError.new
+      end
+
+      private
+
+      def run_batch(relation)
+        relation.map { |upload| verify(upload) }.compact.to_h
+      end
+
+      def verify(object)
+        expected = expected_checksum(object)
+        actual = actual_checksum(object)
+
+        raise 'Checksum missing' unless expected.present?
+        raise 'Checksum mismatch' unless expected == actual
+
+        nil
+      rescue => err
+        [object, err]
+      end
+
+      # This should return an ActiveRecord::Relation suitable for calling #in_batches on
+      def relation
+        raise NotImplementedError.new
+      end
+
+      # The checksum we expect the object to have
+      def expected_checksum(_object)
+        raise NotImplementedError.new
+      end
+
+      # The freshly-recalculated checksum of the object
+      def actual_checksum(_object)
+        raise NotImplementedError.new
+      end
+    end
+  end
+end