1 files changed, 44 insertions, 0 deletions
diff --git a/app/services/solidus_subscriptions/line_item_builder.rb b/app/services/solidus_subscriptions/line_item_builder.rb
new file mode 100644
index 0000000..b288629
--- /dev/null
+++ b/app/services/solidus_subscriptions/line_item_builder.rb
@@ -0,0 +1,44 @@
+# This class is responsible for taking SubscriptionLineItems and building
+# them into Spree::LineItems which can be added to an order
+module SolidusSubscriptions
+  class LineItemBuilder
+    attr_reader :subscription_line_items
+
+    # Get a new instance of a LineItemBuilder
+    #
+    # @param subscription_line_items[Array<SolidusSubscriptions::LineItem>] The
+    #   subscription line item to be converted into a Spree::LineItem
+    #
+    # @return [SolidusSubscriptions::LineItemBuilder]
+    def initialize(subscription_line_items)
+      @subscription_line_items = subscription_line_items
+    end
+
+    # Get a new (unpersisted) Spree::LineItem which matches the details of
+    # :subscription_line_item
+    #
+    # @return [Array<Spree::LineItem>]
+    def spree_line_items
+      line_items = subscription_line_items.map do |subscription_line_item|
+        variant = subscribables.fetch(subscription_line_item.subscribable_id)
+
+        raise UnsubscribableError.new(variant) unless variant.subscribable?
+        next unless variant.can_supply?(subscription_line_item.quantity)
+
+        ::Spree::LineItem.new(variant: variant, quantity: subscription_line_item.quantity)
+      end
+
+      # Either all line items for an installment are fulfilled or none are
+      line_items.all? ? line_items : []
+    end
+
+    private
+
+    def subscribables
+      return @subscribables if @subscribables
+
+      ids = subscription_line_items.map(&:subscribable_id)
+      @subscribables ||= ::Spree::Variant.find(ids).index_by(&:id)
+    end
+  end
+end