Added Domain validation (go-ozzo#43)

* Add Subdomain validation

* Added Domain validation
README update

Author: meydjer

README.md

@@ -443,6 +443,8 @@ Below is the whole list of the rules provided by the `is` package:
 * `IP`: validates if a string is a valid IP address (either version 4 or 6)
 * `IPv4`: validates if a string is a valid version 4 IP address
 * `IPv6`: validates if a string is a valid version 6 IP address
+* `Subdomain`: validates if a string is valid subdomain
+* `Domain`: validates if a string is valid domain
 * `DNSName`: validates if a string is valid DNS name
 * `Host`: validates if a string is a valid IP (both v4 and v6) or a valid DNS name
 * `Port`: validates if a string is a valid port number

is/rules.go

@@ -100,6 +100,8 @@ var (
 	IPv6 = validation.NewStringRule(govalidator.IsIPv6, "must be a valid IPv6 address")
 	// Subdomain validates if a string is valid subdomain
 	Subdomain = validation.NewStringRule(isSubdomain, "must be a valid subdomain")
+	// Domain validates if a string is valid domain
+	Domain = validation.NewStringRule(isDomain, "must be a valid domain")
 	// DNSName validates if a string is valid DNS name
 	DNSName = validation.NewStringRule(govalidator.IsDNSName, "must be a valid DNS name")
 	// Host validates if a string is a valid IP (both v4 and v6) or a valid DNS name
@@ -133,9 +135,24 @@ func isDigit(value string) bool {
 }
 
 func isSubdomain(value string) bool {
+	// Subdomain regex source: https://stackoverflow.com/a/7933253
+	reSubdomain := regexp.MustCompile(`^[A-Za-z0-9](?:[A-Za-z0-9\-]{0,61}[A-Za-z0-9])?$`)
 	return reSubdomain.MatchString(value)
 }
 
+func isDomain(value string) bool {
+	if len(value) > 255 {
+		return false
+	}
+
+	// Domain regex source: https://stackoverflow.com/a/7933253
+	// Slightly modified: Removed 255 max length validation since Go regex does not
+	// support lookarounds. More info: https://stackoverflow.com/a/38935027
+	reDomain := regexp.MustCompile(`^(?:[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?\.)+(?:[a-z]{1,63}| xn--[a-z0-9]{1,59})$`)
+
+	return reDomain.MatchString(value)
+}
+
 func isUTFNumeric(value string) bool {
 	for _, c := range value {
 		if unicode.IsNumber(c) == false {

is/rules_test.go

@@ -36,6 +36,7 @@ func TestAll(t *testing.T) {
 		{"IPv6", IPv6, "2001:4860:0:2001::68", "74.125.19.99", "must be a valid IPv6 address"},
 		{"MAC", MAC, "0123.4567.89ab", "74.125.19.99", "must be a valid MAC address"},
 		{"Subdomain", Subdomain, "example-subdomain", "example.com", "must be a valid subdomain"},
+		{"Domain", Domain, "example-domain.com", "localhost", "must be a valid domain"},
 		{"DNSName", DNSName, "example.com", "abc%", "must be a valid DNS name"},
 		{"Host", Host, "example.com", "abc%", "must be a valid IP address or DNS name"},
 		{"Port", Port, "123", "99999", "must be a valid port number"},