openfoodnetwork/app/serializers/api/admin/line_item_serializer.rb

class Api::Admin::LineItemSerializer < ActiveModel::Serializer
  attributes :id, :quantity, :max_quantity, :price, :supplier, :final_weight_volume,
             :units_product, :units_variant

  has_one :order, serializer: Api::Admin::IdSerializer

  def supplier
    { id: object.product.supplier_id }
  end

  def units_product
    Api::Admin::UnitsProductSerializer.new(object.product).serializable_hash
  end

  def units_variant
    Api::Admin::UnitsVariantSerializer.new(object.variant).serializable_hash
  end

  def final_weight_volume
    object.final_weight_volume.to_f
  end

  def max_quantity
    return object.quantity unless object.max_quantity.present? &&
                                  object.max_quantity > object.quantity
    object.max_quantity
  end
end