1 files changed, 88 insertions, 0 deletions
diff --git a/app/services/packages/nuget/check_duplicates_service.rb b/app/services/packages/nuget/check_duplicates_service.rb
new file mode 100644
index 00000000000..7ad9038d7c1
--- /dev/null
+++ b/app/services/packages/nuget/check_duplicates_service.rb
@@ -0,0 +1,88 @@
+# frozen_string_literal: true
+
+module Packages
+  module Nuget
+    class CheckDuplicatesService < BaseService
+      include Gitlab::Utils::StrongMemoize
+
+      ExtractionError = Class.new(StandardError)
+
+      def execute
+        return ServiceResponse.success if package_settings_allow_duplicates? || !target_package_is_duplicate?
+
+        ServiceResponse.error(
+          message: 'A package with the same name and version already exists',
+          reason: :conflict
+        )
+      rescue ExtractionError => e
+        ServiceResponse.error(message: e.message, reason: :bad_request)
+      end
+
+      private
+
+      def package_settings_allow_duplicates?
+        package_settings.nuget_duplicates_allowed? || package_settings.class.duplicates_allowed?(existing_package)
+      end
+
+      def target_package_is_duplicate?
+        existing_package.name.casecmp(metadata[:package_name]) == 0 &&
+          (existing_package.version.casecmp(metadata[:package_version]) == 0 ||
+            existing_package.normalized_nuget_version&.casecmp(metadata[:package_version]) == 0)
+      end
+
+      def package_settings
+        project.namespace.package_settings
+      end
+      strong_memoize_attr :package_settings
+
+      def existing_package
+        ::Packages::Nuget::PackageFinder
+          .new(
+            current_user,
+            project,
+            package_name: metadata[:package_name],
+            package_version: metadata[:package_version]
+          )
+          .execute
+          .first
+      end
+      strong_memoize_attr :existing_package
+
+      def metadata
+        if remote_package_file?
+          ExtractMetadataContentService
+            .new(nuspec_file_content)
+            .execute
+            .payload
+        else # to cover the case when package file is on disk not in object storage
+          MetadataExtractionService
+            .new(mock_package_file)
+            .execute
+            .payload
+        end
+      end
+      strong_memoize_attr :metadata
+
+      def remote_package_file?
+        params[:remote_url].present?
+      end
+
+      def nuspec_file_content
+        ExtractRemoteMetadataFileService
+          .new(params[:remote_url])
+          .execute
+          .payload
+      rescue ExtractRemoteMetadataFileService::ExtractionError => e
+        raise ExtractionError, e.message
+      end
+
+      def mock_package_file
+        ::Packages::PackageFile.new(
+          params
+            .slice(:file, :file_name)
+            .merge(package: ::Packages::Package.nuget.build)
+        )
+      end
+    end
+  end
+end