Module: Magelex::TaxGuess

Defined in:
lib/magelex/tax_guess.rb

Class Method Summary collapse

Class Method Details

.guess(total, tax_amount) ⇒ Object

Guesses the tax category. Question is: how many percent of total is tax_amount.



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# File 'lib/magelex/tax_guess.rb', line 5

def self.guess(total, tax_amount)
  if total == 0 && tax_amount == 0
    return :empty_item
  end
  if total == 0
    raise "TaxGuess: Cannot guess tax of "\
      "#{total}/#{tax_amount} (#{total - total/tax_amount})"
  end

  # net: netto, gro: gross/brutto
  # gro_price = net_price + taxes         ## (1: net_price = gro_price - taxes)
  # gro_price = net_price + net_price * tax_perce
  # tax_perce = (gro_price - net_price) / net_price
  # tax_perce = gro_price / net_price - 1 ## (see 1)
  percentage = total.to_f / (total - tax_amount) - 1

  case percentage
    when -0.01..0.01
      :tax0
    when 0.06..0.09
      :tax7
    when 0.16..0.20
      :tax19
    else
      raise "TaxGuess: Cannot guess tax of "\
        "#{total}/#{tax_amount} (#{total - total/tax_amount}) - #{tax_amount/total if total != 0}"
  end
end