spree-contrib/spree_drop_ship

module Dropship
  module Spree
    module ProductDecorator
      def self.prepended(base)
        base.has_many :suppliers, through: :master
      end

      def add_supplier!(supplier_or_id)
        supplier = supplier_or_id.is_a?(::Spree::Supplier) ? supplier_or_id : ::Spree::Supplier.find(supplier_or_id)
        populate_for_supplier! supplier if supplier
      end

      def add_suppliers!(supplier_ids)
        ::Spree::Supplier.where(id: supplier_ids).find_each do |supplier|
          populate_for_supplier! supplier
        end
      end

      # Returns true if the product has a drop shipping supplier.
      def supplier?
        suppliers.present?
      end

      private

      def populate_for_supplier!(supplier)
        variants_including_master.each do |variant|
          unless variant.suppliers.pluck(:id).include?(supplier.id)
            variant.suppliers << supplier
            supplier.stock_locations.each { |location| location.propagate_variant(variant) }
          end
        end
      end
    end
  end
end

Spree::Product.prepend Dropship::Spree::ProductDecorator