1 files changed, 65 insertions, 0 deletions
diff --git a/lib/gitlab/pagination/offset_header_builder.rb b/lib/gitlab/pagination/offset_header_builder.rb
new file mode 100644
index 00000000000..32089e40932
--- /dev/null
+++ b/lib/gitlab/pagination/offset_header_builder.rb
@@ -0,0 +1,65 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Pagination
+    class OffsetHeaderBuilder
+      attr_reader :request_context, :per_page, :page, :next_page, :prev_page, :total, :total_pages
+
+      delegate :params, :header, :request, to: :request_context
+
+      def initialize(request_context:, per_page:, page:, next_page:, prev_page: nil, total:, total_pages:)
+        @request_context = request_context
+        @per_page = per_page
+        @page = page
+        @next_page = next_page
+        @prev_page = prev_page
+        @total = total
+        @total_pages = total_pages
+      end
+
+      def execute(exclude_total_headers: false, data_without_counts: false)
+        header 'X-Per-Page',    per_page.to_s
+        header 'X-Page',        page.to_s
+        header 'X-Next-Page',   next_page.to_s
+        header 'X-Prev-Page',   prev_page.to_s
+        header 'Link',          pagination_links(data_without_counts)
+
+        return if exclude_total_headers || data_without_counts
+
+        header 'X-Total',       total.to_s
+        header 'X-Total-Pages', total_pages.to_s
+      end
+
+      private
+
+      def pagination_links(data_without_counts)
+        [].tap do |links|
+          links << %(<#{page_href(page: prev_page)}>; rel="prev") if prev_page
+          links << %(<#{page_href(page: next_page)}>; rel="next") if next_page
+          links << %(<#{page_href(page: 1)}>; rel="first")
+
+          links << %(<#{page_href(page: total_pages)}>; rel="last") unless data_without_counts
+        end.join(', ')
+      end
+
+      def base_request_uri
+        @base_request_uri ||= URI.parse(request.url).tap do |uri|
+          uri.host = Gitlab.config.gitlab.host
+          uri.port = Gitlab.config.gitlab.port
+        end
+      end
+
+      def build_page_url(query_params:)
+        base_request_uri.tap do |uri|
+          uri.query = query_params
+        end.to_s
+      end
+
+      def page_href(next_page_params = {})
+        query_params = params.merge(**next_page_params, per_page: params[:per_page]).to_query
+
+        build_page_url(query_params: query_params)
+      end
+    end
+  end
+end