module Billing
  module Stripe
    module PlanChangeMessages
      module_function

      def flash_notice(result, current_plan: nil)
        plan = Plan[result.plan_slug]
        interval_label = PriceCatalog.label(plan_slug: result.plan_slug, interval: result.interval)

        if result.upgrade?
          amount = format_amount(result.amount_cents, result.currency)
          if amount.present?
            I18n.t("billing.messages.upgrade_completed_with_amount", plan: plan.name, interval: interval_label, amount: amount)
          else
            I18n.t("billing.messages.upgrade_completed_pending_charge", plan: plan.name, interval: interval_label)
          end
        else
          when_label = result.effective_at.present? ? I18n.l(result.effective_at, format: :long) : I18n.t("billing.messages.next_renewal")
          current_name = current_plan&.name || I18n.t("billing.messages.current_plan_generic")
          I18n.t("billing.messages.downgrade_scheduled", plan: plan.name, interval: interval_label, current_name: current_name, when: when_label)
        end
      end

      def button_label(plan:, interval:, kind:)
        price = PriceCatalog.label(plan_slug: plan.slug, interval: interval)
        name = I18n.t("pages.plans.cta_name.#{plan.slug}", default: plan.name)
        if kind == :checkout
          I18n.t("billing.messages.activate_button", plan: name, price: price)
        else
          I18n.t("billing.messages.switch_button", plan: name, price: price)
        end
      end

      def billing_info_lines(subscription: nil)
        lines = [
          I18n.t("billing.messages.upgrade_info_line"),
          I18n.t("billing.messages.downgrade_info_line")
        ]

        if subscription&.plan_change_pending? && subscription.pending_plan.present?
          when_at = subscription.current_period_end
          when_label = when_at.present? ? I18n.l(when_at, format: :long) : I18n.t("billing.messages.next_renewal")
          lines.unshift(
            I18n.t("billing.messages.already_requested_line", plan: subscription.pending_plan.name, when: when_label, current_plan: subscription.plan.name)
          )
        end

        lines
      end

      def format_amount(cents, currency)
        return nil if cents.blank? || cents.to_i <= 0

        unit = currency.to_s.upcase.presence || "EUR"
        amount = cents.to_i / 100.0
        format("%.2f %s", amount, unit == "EUR" ? "€" : unit)
      end
    end
  end
end