# frozen_string_literal: true
module API
  class GoProxy < ::API::Base
    helpers Gitlab::Golang
    helpers ::API::Helpers::PackagesHelpers

    # basic semver, except case encoded (A => !a)
    MODULE_VERSION_REGEX = /v(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)(?:-([-.!a-z0-9]+))?(?:\+([-.!a-z0-9]+))?/.freeze

    MODULE_VERSION_REQUIREMENTS = { module_version: MODULE_VERSION_REGEX }.freeze

    before { require_packages_enabled! }

    helpers do
      def case_decode(str)
        # Converts "github.com/!azure" to "github.com/Azure"
        #
        # From `go help goproxy`:
        #
        # > To avoid problems when serving from case-sensitive file systems,
        # > the <module> and <version> elements are case-encoded, replacing
        # > every uppercase letter with an exclamation mark followed by the
        # > corresponding lower-case letter: github.com/Azure encodes as
        # > github.com/!azure.

        str.gsub(/![[:alpha:]]/) { |s| s[1..].upcase }
      end

      def find_project!(id)
        # based on API::Helpers::Packages::BasicAuthHelpers#authorized_project_find!

        project = find_project(id)

        return project if project && can?(current_user, :read_project, project)

        if current_user
          not_found!('Project')
        else
          unauthorized!
        end
      end

      def find_module
        not_found! unless Feature.enabled?(:go_proxy, user_project)

        module_name = case_decode params[:module_name]
        bad_request!('Module Name') if module_name.blank?

        mod = ::Packages::Go::ModuleFinder.new(user_project, module_name).execute

        not_found! unless mod

        mod
      end

      def find_version
        module_version = case_decode params[:module_version]
        ver = ::Packages::Go::VersionFinder.new(find_module).find(module_version)

        not_found! unless ver&.valid?

        ver

      rescue ArgumentError
        not_found!
      end
    end

    params do
      requires :id, type: String, desc: 'The ID of a project'
      requires :module_name, type: String, desc: 'Module name', coerce_with: ->(val) { CGI.unescape(val) }
    end
    route_setting :authentication, job_token_allowed: true, basic_auth_personal_access_token: true
    resource :projects, requirements: API::NAMESPACE_OR_PROJECT_REQUIREMENTS do
      before do
        authorize_read_package!
      end

      namespace ':id/packages/go/*module_name/@v' do
        desc 'Get all tagged versions for a given Go module' do
          detail 'See `go help goproxy`, GET $GOPROXY/<module>/@v/list. This feature was introduced in GitLab 13.1.'
        end
        get 'list' do
          mod = find_module

          content_type 'text/plain'
          mod.versions.map { |t| t.name }.join("\n")
        end

        desc 'Get information about the given module version' do
          detail 'See `go help goproxy`, GET $GOPROXY/<module>/@v/<version>.info. This feature was introduced in GitLab 13.1.'
          success ::API::Entities::GoModuleVersion
        end
        params do
          requires :module_version, type: String, desc: 'Module version'
        end
        get ':module_version.info', requirements: MODULE_VERSION_REQUIREMENTS do
          ver = find_version

          present ::Packages::Go::ModuleVersionPresenter.new(ver), with: ::API::Entities::GoModuleVersion
        end

        desc 'Get the module file of the given module version' do
          detail 'See `go help goproxy`, GET $GOPROXY/<module>/@v/<version>.mod. This feature was introduced in GitLab 13.1.'
        end
        params do
          requires :module_version, type: String, desc: 'Module version'
        end
        get ':module_version.mod', requirements: MODULE_VERSION_REQUIREMENTS do
          ver = find_version

          content_type 'text/plain'
          ver.gomod
        end

        desc 'Get a zip of the source of the given module version' do
          detail 'See `go help goproxy`, GET $GOPROXY/<module>/@v/<version>.zip. This feature was introduced in GitLab 13.1.'
        end
        params do
          requires :module_version, type: String, desc: 'Module version'
        end
        get ':module_version.zip', requirements: MODULE_VERSION_REQUIREMENTS do
          ver = find_version

          content_type 'application/zip'
          env['api.format'] = :binary
          header['Content-Disposition'] = ActionDispatch::Http::ContentDisposition.format(disposition: 'attachment', filename: ver.name + '.zip')
          header['Content-Transfer-Encoding'] = 'binary'
          status :ok
          body ver.archive.string
        end
      end
    end
  end
end