payment.go

package dough

import (
	"errors"
	"regexp"
	"strings"
)

// errors
var (
	ErrCardLength      = errors.New("card length should be > 10")
	ErrACHLength       = errors.New("account length should be > 4")
	ErrUnknownCardType = errors.New("unknown card type")
)

// vars
var (
	amexCardFormatString                = `^3[47][0-9]{13}$`
	visaCardFormatString                = `^4[0-9]{15}$`
	mastercardCardFormatString          = `^(?:5[1-9][0-9]{2}|222[1-9]|22[3-9][0-9]|2[3-6][0-9]{2}|27[01][0-9]|2720)[0-9]{12}$`
	discoverCardFormatString            = `^65[0-9]{14,17}|64[4-9][0-9]{13,16}|6011[0-9]{12,15}|(622(?:12[6-9]|1[3-9][0-9]|[2-8][0-9][0-9]|9[01][0-9]|92[0-5])[0-9]{10,13})$`
	mastroCardFormatString              = `^(?:5[0678]\d\d|6304|6390|67\d\d)\d{8,15}$`
	jcbCardFormatString                 = `^(?:2131|1800|35[0-9]{2})[0-9]{12,15}$`
	dinersClubInternationalFormatString = `^3(?:0[0-5]|[68][0-9])[0-9]{11,16}$`

	AMEXCardFormatRegex     = regexp.MustCompile(amexCardFormatString)
	VISACardFormatRegex     = regexp.MustCompile(visaCardFormatString)
	MasterCardFormatRegex   = regexp.MustCompile(mastercardCardFormatString)
	MastroCardFormatRegex   = regexp.MustCompile(mastroCardFormatString)
	DISCOVERCardFormatRegex = regexp.MustCompile(discoverCardFormatString)
	JCBCardFormatRegex      = regexp.MustCompile(jcbCardFormatString)
	DINERSCardFormatRegex   = regexp.MustCompile(dinersClubInternationalFormatString)
)

// MaskCard takes in a card number and returns firstsix, lastfour, masked
func MaskCard(cardnumber string) (string, string, string, error) {
	length := len(cardnumber)
	if length < 10 {
		return "", "", "", ErrCardLength
	}
	maskLen := length - 10
	firstSix := cardnumber[:6]
	lastFour := cardnumber[length-4:]
	maskedCard := firstSix + strings.Repeat("*", maskLen) + lastFour

	return firstSix, lastFour, maskedCard, nil
}

// MaskACHAccount takes in an account number and returns masked
func MaskACHAccount(accountNumber string) (string, error) {
	length := len(accountNumber)
	if length < 4 {
		return "", ErrACHLength
	}
	maskLen := length - 4
	firstTwo := accountNumber[:2]
	lastTwo := accountNumber[length-2:]
	maskedAccount := firstTwo + strings.Repeat("*", maskLen) + lastTwo

	return maskedAccount, nil
}

// ValidLuhn returns a boolean indicating if the argument was valid according to the Luhn algorithm.
func ValidLuhn(s string) bool {
	var t = [...]int{0, 2, 4, 6, 8, 1, 3, 5, 7, 9}
	odd := len(s) & 1
	var sum int
	for i, c := range s {
		if c < '0' || c > '9' {
			return false
		}
		if i&1 == odd {
			sum += t[c-'0']
		} else {
			sum += int(c - '0')
		}
	}
	return sum%10 == 0
}

// GetCardType Accepts a string containing a credit card number and validates it against some regexes to return the card type.
func GetCardType(cardnum string) (string, error) {
	if AMEXCardFormatRegex.MatchString(cardnum) {
		return "amex", nil
	}

	if VISACardFormatRegex.MatchString(cardnum) {
		return "visa", nil
	}

	if MasterCardFormatRegex.MatchString(cardnum) {
		return "mastercard", nil
	}

	if MastroCardFormatRegex.MatchString(cardnum) {
		return "mastercard", nil
	}

	if DISCOVERCardFormatRegex.MatchString(cardnum) {
		return "discover", nil
	}

	if JCBCardFormatRegex.MatchString(cardnum) {
		return "jcb", nil
	}

	if DINERSCardFormatRegex.MatchString(cardnum) {
		return "diners", nil
	}

	return "", ErrUnknownCardType
}