class ParamFilter
  ORDER_ATTRIBUTE_MAPPINGS = {
    :bill_city => :billing_city,
    :bill_address1 => :billing_address_line_1,
    :bill_zip => :billing_zip,
    :bill_country => :billing_country,
    :expiry_date => :expiration_date,
    :bill_address2 => :billing_address_line_2,
    :bill_state => :billing_state
  }
  def self.select_item_quantities(params)
    selected = params.select do |key, value|
      key.to_s =~ /^[A-Z]+-\d+$/
    end
    Hash[*selected.flatten]
  end
  
  def self.select_order_attributes(params)
    selected = params.select do |key, value|
      key.to_s =~ /^order\./
    end
    attributes = selected.map do |key, value|
      [key[6..-1].underscore.to_sym, value]
    end
    result_hash = Hash[*attributes.flatten]
    ORDER_ATTRIBUTE_MAPPINGS.each do |old, new|
      result_hash[new] = result_hash.delete(old)
    end
    result_hash
  end
end