module ActiveMerchant #:nodoc:
  module Billing #:nodoc:
    # The Check object is a plain old Ruby object, similar to CreditCard. It supports validation
    # of necessary attributes such as checkholder's name, routing and account numbers, but it is
    # not backed by any database.
    # 
    # You may use Check in place of CreditCard with any gateway that supports it. Currently, only
    # +BrainTreeGateway+ supports the Check object.
    class Check
      include Validateable
      
      attr_accessor :name, :routing_number, :account_number, :account_holder_type, :account_type
      
      def initialize(args={})
        args = args.with_indifferent_access
        self.name           = args[:name]
        self.routing_number = args[:routing_number]
        self.account_number = args[:account_number]
        self.account_holder_type = args[:account_holder_type]
        self.account_type   = args[:account_type]
      end
      
      def validate
        for attr in [:name, :routing_number, :account_number]
          errors.add(attr, "cannot be empty") if self.send(attr).blank?
        end
        
        errors.add(:routing_number, "is invalid") unless valid_routing_number?
        
        errors.add(:account_holder_type, "must be personal or business") if
            !account_holder_type.blank? && !%w[business personal].include?(account_holder_type.to_s)
        
        errors.add(:account_type, "must be checking or savings") if
            !account_type.blank? && !%w[checking savings].include?(account_type.to_s)
      end
      
      def type
        'check'
      end
      
      # Routing numbers may be validated by calculating a checksum and dividing it by 10. The
      # formula is:
      #   (3(d1 + d4 + d7) + 7(d2 + d5 + d8) + 1(d3 + d6 + d9))mod 10 = 0
      # See http://en.wikipedia.org/wiki/Routing_transit_number#Internal_checksums
      def valid_routing_number?
        d = routing_number.to_s.split('').map(&:to_i).select { |d| (0..9).include?(d) }
        case d.size
          when 9 then
            checksum = ((3 * (d[0] + d[3] + d[6])) +
                        (7 * (d[1] + d[4] + d[7])) +
                             (d[2] + d[5] + d[8])) % 10
            case checksum
              when 0 then true
              else        false
            end
          else false
        end
      end
    end
  end
end