theseus/app/services/usps/pricing_engine.rb

module USPS
  class PricingEngine
    class << self
      # this will have to be updated when they come out with a new notice 123!
      FCMI_RATE_TABLE = {
        letter: {
          1.0 => {
            ca: 1.70,
            mx: 1.70,
            other: 1.70
          },
          2.0 => {
            ca: 2.00,
            mx: 2.55,
            other: 3.40
          },
          3.0 => {
            ca: 2.70,
            mx: 3.40,
            other: 5.10
          },
          3.5 => {
            ca: 3.40,
            mx: 4.15,
            other: 5.75
          },
        },
        flat: {
          1.0 => {
            ca: 3.15,
            mx: 3.15,
            other: 3.15
          },
          2.0 => {
            ca: 3.65,
            mx: 4.25,
            other: 4.55
          },
          3.0 => {
            ca: 4.15,
            mx: 5.35,
            other: 5.95
          },
          4.0 => {
            ca: 4.65,
            mx: 6.45,
            other: 7.35
          },
          5.0 => {
            ca: 5.15,
            mx: 7.55,
            other: 8.75
          },
          6.0 => {
            ca: 5.65,
            mx: 8.65,
            other: 10.15
          },
          7.0 => {
            ca: 6.15,
            mx: 9.75,
            other: 11.55
          },
          8.0 => {
            ca: 6.65,
            mx: 10.85,
            other: 12.95
          },
          12.0 => {
            ca: 7.60,
            mx: 13.00,
            other: 15.75
          },
          15.994 => {
            ca: 8.55,
            mx: 15.15,
            other: 18.55
          },
        }
      }
      FCMI_NON_MACHINABLE_SURCHARGE = 0.49

      US_LETTER_RATES = {
        1.0 => 0.74,
        2.0 => 1.03,
        3.0 => 1.32,
        3.5 => 1.61
      }

      US_FLAT_RATES = {
        1.0 => 1.63,
        2.0 => 1.90,
        3.0 => 2.17,
        4.0 => 2.44,
        5.0 => 2.72,
        6.0 => 3.00,
        7.0 => 3.28,
        8.0 => 3.56,
        9.0 => 3.84,
        10.0 => 4.14,
        11.0 => 4.44,
        12.0 => 4.74,
        13.0 => 5.04
      }

      US_STAMP_LETTER_RATES = {
        1.0 => 0.74,
        2.0 => 1.03,
        3.0 => 1.32,
        3.5 => 1.61
      }

      US_STAMP_FLAT_RATES = {
        1.0 => 1.63,
        2.0 => 1.90,
        3.0 => 2.17,
        4.0 => 2.44,
        5.0 => 2.72,
        6.0 => 3.00,
        7.0 => 3.28,
        8.0 => 3.56,
        9.0 => 3.84,
        10.0 => 4.14,
        11.0 => 4.44,
        12.0 => 4.74,
        13.0 => 5.04
      }

      def metered_price(processing_category, weight, non_machinable = false)
        type = processing_category.to_sym
        rates = case type
        when :letter
                  US_LETTER_RATES
        when :flat
                  US_FLAT_RATES
        else
                  raise ArgumentError, "type must be :letter or :flat"
        end

        rate = rates.find { |k, v| weight <= k }&.last
        raise ArgumentError, "#{weight} oz is too heavy for a #{type}" unless rate

        if non_machinable
          raise ArgumentError, "only letters can be non-machinable!" unless type == :letter
          rate += FCMI_NON_MACHINABLE_SURCHARGE
        end

        rate
      end

      def domestic_stamp_price(processing_category, weight, non_machinable = false)
        type = processing_category.to_sym
        rates = case type
        when :letter
                  US_STAMP_LETTER_RATES
        when :flat
                  US_STAMP_FLAT_RATES
        else
                  raise ArgumentError, "type must be :letter or :flat"
        end

        rate = rates.find { |k, v| weight <= k }&.last
        raise ArgumentError, "#{weight} oz is too heavy for a #{type}" unless rate

        if non_machinable
          raise ArgumentError, "only letters can be non-machinable!" unless type == :letter
          rate += FCMI_NON_MACHINABLE_SURCHARGE
        end

        rate
      end

      def fcmi_price(processing_category, weight, country, non_machinable = false)
        type = processing_category.to_sym
        rates = FCMI_RATE_TABLE[type]

        raise ArgumentError, "idk the rates for #{type}..." unless rates
        country = case country
        when "CA"
                    :ca
        when "MX"
                    :mx
        else
                    :other
        end

        rate = rates.find { |k, v| weight <= k }&.dig(1)
        raise "#{weight} oz is too heavy for an FCMI #{type}" unless rate
        price = rate[country]
        if non_machinable
          raise ArgumentError, "only letters can be nonmachinable!" unless type == :letter
          price += FCMI_NON_MACHINABLE_SURCHARGE
        end
        price
      end

      def stamp_price(processing_category, weight, country, non_machinable = false)
        if country == "US"
          domestic_stamp_price(processing_category, weight, non_machinable)
        else
          fcmi_price(processing_category, weight, country, non_machinable)
        end
      end
    end
  end
end