1 files changed, 87 insertions, 0 deletions
diff --git a/app/presenters/packages/npm/package_presenter.rb b/app/presenters/packages/npm/package_presenter.rb
new file mode 100644
index 00000000000..a3ab10d3913
--- /dev/null
+++ b/app/presenters/packages/npm/package_presenter.rb
@@ -0,0 +1,87 @@
+# frozen_string_literal: true
+
+module Packages
+  module Npm
+    class PackagePresenter
+      include API::Helpers::RelatedResourcesHelpers
+
+      attr_reader :name, :packages
+
+      NPM_VALID_DEPENDENCY_TYPES = %i[dependencies devDependencies bundleDependencies peerDependencies].freeze
+
+      def initialize(name, packages)
+        @name = name
+        @packages = packages
+      end
+
+      def versions
+        package_versions = {}
+
+        packages.each do |package|
+          package_file = package.package_files.last
+
+          next unless package_file
+
+          package_versions[package.version] = build_package_version(package, package_file)
+        end
+
+        package_versions
+      end
+
+      def dist_tags
+        build_package_tags.tap { |t| t["latest"] ||= sorted_versions.last }
+      end
+
+      private
+
+      def build_package_tags
+        Hash[
+          package_tags.map { |tag| [tag.name, tag.package.version] }
+        ]
+      end
+
+      def build_package_version(package, package_file)
+        {
+          name: package.name,
+          version: package.version,
+          dist: {
+            shasum: package_file.file_sha1,
+            tarball: tarball_url(package, package_file)
+          }
+        }.tap do |package_version|
+          package_version.merge!(build_package_dependencies(package))
+        end
+      end
+
+      def tarball_url(package, package_file)
+        expose_url "#{api_v4_projects_path(id: package.project_id)}" \
+          "/packages/npm/#{package.name}" \
+          "/-/#{package_file.file_name}"
+      end
+
+      def build_package_dependencies(package)
+        dependencies = Hash.new { |h, key| h[key] = {} }
+        dependency_links = package.dependency_links
+                                  .with_dependency_type(NPM_VALID_DEPENDENCY_TYPES)
+                                  .includes_dependency
+
+        dependency_links.find_each do |dependency_link|
+          dependency = dependency_link.dependency
+          dependencies[dependency_link.dependency_type][dependency.name] = dependency.version_pattern
+        end
+
+        dependencies
+      end
+
+      def sorted_versions
+        versions = packages.map(&:version).compact
+        VersionSorter.sort(versions)
+      end
+
+      def package_tags
+        Packages::Tag.for_packages(packages)
+                    .preload_package
+      end
+    end
+  end
+end