module Returnly
  module Refund
    class AmountCalculator
      attr_accessor :refund

      def initialize(refund)
        self.refund = refund
      end

      def return_item_refund_amount(return_item)
        (item_price(return_item) * item_price_percentage / 100).round(2, :down)
      end

      protected

      def total_single_items_price
        refund.line_items.inject(0.0.to_d) do |amount, line_item_hash|
          line_item = Spree::LineItem.find(line_item_hash['order_line_item_id'])
          amount += (line_item_price(line_item) * line_item_hash['units'].to_d).round(2, :down)
          amount
        end.round(2, :down)
      end

      def line_item_price(line_item)
        (line_item.price + line_item_tax_price(line_item) + line_item_discount_price(line_item)).round(2, :down)
      end

      def item_price_percentage
        [(available_amount * 100 / total_single_items_price).round(2, :down), 100.0.to_d].min
      end

      def item_price(return_item)
        line_item_price(return_item.inventory_unit.line_item)
      end

      def line_item_tax_price(line_item)
        (line_item.adjustments.tax.sum(&:amount).to_d.round(2, :down) / line_item.quantity).round(2, :down)
      end

      def line_item_discount_price(line_item)
        discounter_calculator.calculate(
          [
            {
              order_line_item_id: line_item.id,
              units: 1
            }
          ]
        )
      end

      def line_items_price
        refund.order.line_items.sum(&:price).round(2, :down)
      end

      def available_amount
        refund.product_available_amount.round(2, :down)
      end

      def discounter_calculator
        @discounter_calculator ||= Returnly::DiscountCalculator.new(refund.order)
      end
    end
  end
end