Email checker is added. Fixes #28 (#63)

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.
+- [email](doc/checkers/email.md) checks if the given string is an email address.
 - [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.

checker.go

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

doc/checkers/email.md

@@ -0,0 +1,28 @@
+# Email Checker
+
+The ```email``` checker checks if the given string is an email address. If the given string is not a valid email address, the checker will return the ```NOT_EMAIL``` result. Here is an example:
+
+```golang
+type User struct {
+  Email string `checkers:"email"`
+}
+
+user := &User{
+  Email: "[email protected]",
+}
+
+_, valid := Check(user)
+if !valid {
+  // Send the mistakes back to the user
+}
+```
+
+In your custom checkers, you can call the ```ascii``` checker function ```IsAscii``` to validate the user input. Here is an example:
+
+```golang
+result := IsEmail("[email protected]")
+
+if result != ResultValid {
+  // Send the mistakes back to the user
+}
+```

email.go

@@ -0,0 +1,114 @@
+package checker
+
+import (
+	"reflect"
+	"regexp"
+	"strings"
+)
+
+// CheckerEmail is the name of the checker.
+const CheckerEmail = "email"
+
+// ResultNotFqdn indicates that the given string is not a valid email.
+const ResultNotEmail = "NOT_EMAIL"
+
+// ipV6Prefix is the IPv6 prefix for the domain.
+const ipV6Prefix = "[IPv6:"
+
+// notQuotedChars is the valid not quoted characters.
+var notQuotedChars = regexp.MustCompile("[a-zA-Z0-9!#$%&'*+-/=?^_`{|}~]")
+
+// IsEmail checks if the given string is an email address.
+func IsEmail(email string) Result {
+	atIndex := strings.LastIndex(email, "@")
+	if atIndex == -1 || atIndex == len(email)-1 {
+		return ResultNotEmail
+	}
+
+	domain := email[atIndex+1:]
+	if isValidEmailDomain(domain) != ResultValid {
+		return ResultNotEmail
+	}
+
+	user := email[:atIndex]
+
+	// Cannot be empty user
+	if len(user) == 0 || len(user) > 64 {
+		return ResultNotEmail
+	}
+
+	// Cannot start or end with dot
+	if user[0] == '.' || user[len(user)-1] == '.' {
+		return ResultNotEmail
+	}
+
+	quoted := false
+	start := true
+	prev := ' '
+
+	for _, c := range user {
+		// Cannot have a double dot unless quoted
+		if !quoted && c == '.' && prev == '.' {
+			return ResultNotEmail
+		}
+
+		if start {
+			start = false
+
+			if c == '"' {
+				quoted = true
+				prev = c
+				continue
+			}
+		}
+
+		if !quoted {
+			if c == '.' {
+				start = true
+			} else if !notQuotedChars.MatchString(string(c)) {
+				return ResultNotEmail
+			}
+		} else {
+			if c == '"' && prev != '\\' {
+				quoted = false
+			}
+		}
+
+		prev = c
+	}
+
+	return ResultValid
+}
+
+// makeEmail makes a checker function for the email checker.
+func makeEmail(_ string) CheckFunc {
+	return checkEmail
+}
+
+// checkEmail checks if the given string is an email address.
+func checkEmail(value, _ reflect.Value) Result {
+	if value.Kind() != reflect.String {
+		panic("string expected")
+	}
+
+	return IsEmail(value.String())
+}
+
+// isValidEmailDomain checks if the email domain is a IPv4 or IPv6 address, or a FQDN.
+func isValidEmailDomain(domain string) Result {
+	if len(domain) > 255 {
+		return ResultNotEmail
+	}
+
+	if domain[0] == '[' {
+		if strings.HasPrefix(domain, ipV6Prefix) {
+			// postmaster@[IPv6:2001:0db8:85a3:0000:0000:8a2e:0370:7334]
+			return IsIpV6(domain[len(ipV6Prefix) : len(domain)-1])
+		}
+
+		// postmaster@[123.123.123.123]
+		return IsIpV4(domain[1 : len(domain)-1])
+	}
+
+	return IsFqdn(domain)
+}

email_test.go

@@ -0,0 +1,83 @@
+package checker
+
+import "testing"
+
+func TestCheckEmailNonString(t *testing.T) {
+	defer FailIfNoPanic(t)
+
+	type User struct {
+		Email int `checkers:"email"`
+	}
+
+	user := &User{}
+
+	Check(user)
+}
+
+func TestCheckEmailValid(t *testing.T) {
+	type User struct {
+		Email string `checkers:"email"`
+	}
+
+	user := &User{
+		Email: "[email protected]",
+	}
+
+	_, valid := Check(user)
+	if !valid {
+		t.Fail()
+	}
+}
+
+func TestIsEmailValid(t *testing.T) {
+	validEmails := []string{
+		"[email protected]",
+		"[email protected]",
+		"[email protected]",
+		"[email protected]",
+		"[email protected]",
+		"[email protected]",
+		"[email protected]",
+		"[email protected]",
+		"test/[email protected]",
+		"[email protected]",
+		"\" \"@example.org",
+		"\"john..doe\"@example.org",
+		"[email protected]",
+		"\"very.(),:;<>[]\\\".VERY.\\\"very@\\\\ \\\"very\\\".unusual\"@strange.example.com",
+		"user%[email protected]",
+		"[email protected]",
+		"postmaster@[123.123.123.123]",
+		"postmaster@[IPv6:2001:0db8:85a3:0000:0000:8a2e:0370:7334]",
+	}
+
+	for _, email := range validEmails {
+		if IsEmail(email) != ResultValid {
+			t.Fatal(email)
+		}
+	}
+}
+
+func TestIsEmailInvalid(t *testing.T) {
+	validEmails := []string{
+		"Abc.example.com",
+		"A@b@[email protected]",
+		"a\"b(c)d,e:f;g<h>i[j\\k][email protected]",
+		"just\"not\"[email protected]",
+		"this is\"not\\[email protected]",
+		"this\\ still\\\"not\\\\[email protected]",
+		"1234567890123456789012345678901234567890123456789012345678901234+x@example.com",
+		"i_like_underscore@but_its_not_allowed_in_this_part.example.com",
+		"QA[icon]CHOCOLATE[icon]@test.com",
+		"[email protected]",
+		"[email protected]",
+		"[email protected]",
+		"user@domaincannotbemorethan255charactersdomaincannotbemorethan255charactersdomaincannotbemorethan255charactersdomaincannotbemorethan255charactersdomaincannotbemorethan255charactersdomaincannotbemorethan255charactersdomaincannotbemorethan255charactersdomaincannotbemorethan255characters.com",
+	}
+
+	for _, email := range validEmails {
+		if IsEmail(email) == ResultValid {
+			t.Fatal(email)
+		}
+	}
+}

fqdn.go

@@ -9,7 +9,7 @@ import (
 // CheckerFqdn is the name of the checker.
 const CheckerFqdn = "fqdn"
 
-// ResultNotFqdn indicates that the given string contains non-ASCII characters.
+// ResultNotFqdn indicates that the given string is not a valid FQDN.
 const ResultNotFqdn = "NOT_FQDN"
 
 // Valid characters excluding full-width characters.
@@ -56,7 +56,7 @@ func IsFqdn(domain string) Result {
 	return ResultValid
 }
 
-// makeFqdn makes a checker function for the ascii checker.
+// makeFqdn makes a checker function for the fqdn checker.
 func makeFqdn(_ string) CheckFunc {
 	return checkFqdn
 }