module CreditCards
	Types = { 
		13 => {
			/^4/ => 'Visa'
		},
		15 => {
			/^3[47]/ => 'American Express',
			/^2014|^2149/ => 'enRoute',
			/^2131|^1800/ => 'JCB'
		},
		14 => {
			 /^30[0-5]|^3[68]/ => "Diner's Club",
		},
		16 => {
			/^3/ => 'JCB',
			/^4/ => 'Visa',
			/^5[1-5]/ =>'MasterCard',
			/^6011/ => 'Discover'
		}
	}

	def type_for_card(s)
		Types[s.length].each_pair do |r, t|
			return t if r =~ s
		end
		raise ArgumentError, "None found"
	end
end