FQDN checker is added. Fixes #61 (#62)

* FQDN checker is added. Fixes #61

* Cover coverage, added test.

README.md

@@ -74,6 +74,7 @@ This package currently provides the following checkers:
 - [ascii](doc/checkers/ascii.md) checks if the given string consists of only ASCII characters.
 - [cidr](doc/checkers/cidr.md) checker checks if the value is a valid CIDR notation IP address and prefix length.
 - [digits](doc/checkers/digits.md) checks if the given string consists of only digit characters.
+- [fqdn](doc/checkers/fqdn.md) checks if the given string is a fully qualified domain name.
 - [ip](doc/checkers/ip.md) checks if the given value is an IP address.
 - [ipv4](doc/checkers/ipv4.md) checks if the given value is an IPv4 address.
 - [ipv6](doc/checkers/ipv6.md) checks if the given value is an IPv6 address.

checker.go

@@ -35,6 +35,7 @@ var makers = map[string]MakeFunc{
 	CheckerAscii:        makeAscii,
 	CheckerCidr:         makeCidr,
 	CheckerDigits:       makeDigits,
+	CheckerFqdn:         makeFqdn,
 	CheckerIp:           makeIp,
 	CheckerIpV4:         makeIpV4,
 	CheckerIpV6:         makeIpV6,

doc/checkers/fqdn.md

@@ -0,0 +1,28 @@
+# FQDN Checker
+
+The Full Qualified Domain Name (FQDN) is the complete domain name for a computer or host on the internet. The ```fqdn``` checker checks if the given string consists of a FQDN. If the string is not a valid FQDN, the checker will return the ```NOT_FQDN``` result. Here is an example:
+
+```golang
+type Request struct {
+  Domain string `checkers:"fqdn"`
+}
+
+request := &Request{
+  Domain: "zdo.com",
+}
+
+_, valid := Check(request)
+if !valid {
+  // Send the mistakes back to the user
+}
+```
+
+In your custom checkers, you can call the ```fqdn``` checker function ```IsFqdn``` to validate the user input. Here is an example:
+
+```golang
+result := IsFqdn("zdo.com")
+
+if result != ResultValid {
+  // Send the mistakes back to the user
+}
+```

fqdn.go

@@ -0,0 +1,71 @@
+package checker
+
+import (
+	"reflect"
+	"regexp"
+	"strings"
+)
+
+// CheckerFqdn is the name of the checker.
+const CheckerFqdn = "fqdn"
+
+// ResultNotFqdn indicates that the given string contains non-ASCII characters.
+const ResultNotFqdn = "NOT_FQDN"
+
+// Valid characters excluding full-width characters.
+var fqdnValidChars = regexp.MustCompile("^[a-z0-9\u00a1-\uff00\uff06-\uffff-]+$")
+
+// IsFqdn checks if the given string is a fully qualified domain name.
+func IsFqdn(domain string) Result {
+	parts := strings.Split(domain, ".")
+
+	// Require TLD
+	if len(parts) < 2 {
+		return ResultNotFqdn
+	}
+
+	tld := parts[len(parts)-1]
+
+	// Should be all numeric TLD
+	if IsDigits(tld) == ResultValid {
+		return ResultNotFqdn
+	}
+
+	// Short TLD
+	if len(tld) < 2 {
+		return ResultNotFqdn
+	}
+
+	for _, part := range parts {
+		// Cannot be more than 63 characters
+		if len(part) > 63 {
+			return ResultNotFqdn
+		}
+
+		// Check for valid characters
+		if !fqdnValidChars.MatchString(part) {
+			return ResultNotFqdn
+		}
+
+		// Should not start or end with a hyphen (-) character.
+		if part[0] == '-' || part[len(part)-1] == '-' {
+			return ResultNotFqdn
+		}
+	}
+
+	return ResultValid
+}
+
+// makeFqdn makes a checker function for the ascii checker.
+func makeFqdn(_ string) CheckFunc {
+	return checkFqdn
+}
+
+// checkFqdn checks if the given string is a fully qualified domain name.
+func checkFqdn(value, _ reflect.Value) Result {
+	if value.Kind() != reflect.String {
+		panic("string expected")
+	}
+
+	return IsFqdn(value.String())
+}

fqdn_test.go

@@ -0,0 +1,84 @@
+package checker
+
+import "testing"
+
+func TestCheckFdqnWithoutTld(t *testing.T) {
+	if IsFqdn("abcd") != ResultNotFqdn {
+		t.Fail()
+	}
+}
+
+func TestCheckFdqnShortTld(t *testing.T) {
+	if IsFqdn("abcd.c") != ResultNotFqdn {
+		t.Fail()
+	}
+}
+
+func TestCheckFdqnNumericTld(t *testing.T) {
+	if IsFqdn("abcd.1234") != ResultNotFqdn {
+		t.Fail()
+	}
+}
+
+func TestCheckFdqnLong(t *testing.T) {
+	if IsFqdn("abcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcd.com") != ResultNotFqdn {
+		t.Fail()
+	}
+}
+
+func TestCheckFdqnInvalidCharacters(t *testing.T) {
+	if IsFqdn("ab_cd.com") != ResultNotFqdn {
+		t.Fail()
+	}
+}
+
+func TestCheckFdqnStaringWithHyphen(t *testing.T) {
+	if IsFqdn("-abcd.com") != ResultNotFqdn {
+		t.Fail()
+	}
+}
+
+func TestCheckFdqnStaringEndingWithHyphen(t *testing.T) {
+	if IsFqdn("abcd-.com") != ResultNotFqdn {
+		t.Fail()
+	}
+}
+
+func TestCheckFdqnStartingWithDot(t *testing.T) {
+	if IsFqdn(".abcd.com") != ResultNotFqdn {
+		t.Fail()
+	}
+}
+
+func TestCheckFdqnEndingWithDot(t *testing.T) {
+	if IsFqdn("abcd.com.") != ResultNotFqdn {
+		t.Fail()
+	}
+}
+
+func TestCheckFqdnNonString(t *testing.T) {
+	defer FailIfNoPanic(t)
+
+	type Request struct {
+		Domain int `checkers:"fqdn"`
+	}
+
+	request := &Request{}
+
+	Check(request)
+}
+
+func TestCheckFqdnValid(t *testing.T) {
+	type Request struct {
+		Domain string `checkers:"fqdn"`
+	}
+
+	request := &Request{
+		Domain: "zdo.com",
+	}
+
+	_, valid := Check(request)
+	if !valid {
+		t.Fail()
+	}
+}