module Billing
  class EuroAmount
    class Error < StandardError; end

    def self.to_cents(value)
      raw = value.to_s.strip
      raise Error, "Indica l'importo in euro" if raw.blank?

      normalized = raw.gsub(/\s+/, "")
      if normalized.match?(/\A\d{1,3}(\.\d{3})*,\d{1,2}\z/)
        normalized = normalized.gsub(".", "").tr(",", ".")
      elsif normalized.match?(/\A\d+,\d{1,2}\z/)
        normalized = normalized.tr(",", ".")
      elsif normalized.match?(/\A\d{1,3}(,\d{3})*\.\d{1,2}\z/)
        normalized = normalized.gsub(",", "")
      end

      raise Error, "Importo non valido" unless normalized.match?(/\A\d+(\.\d{1,2})?\z/)

      cents = (BigDecimal(normalized) * 100).round
      raise Error, "L'importo deve essere maggiore di zero" unless cents.positive?

      cents.to_i
    end
  end
end