added Unique validator

Author: tomi77

README.md

@@ -112,3 +112,11 @@ Check if password starts with one of letter.
 ~~~go
 passwordValidator := validator.New(validator.StartsWith("abcdefghijklmnopqrstuvwxyz", nil))
 ~~~
+
+### Unique
+
+Check if password contains only unique chars.
+
+~~~go
+passwordValidator := validator.New(validator.Unique(nil))
+~~~

TODO.md

@@ -1,2 +1 @@
-* Unique
 * NotSequential

unique.go

@@ -0,0 +1,24 @@
+package validator
+
+import (
+	"errors"
+	"strings"
+)
+
+// Unique returns ValidateFunc that validate whether the password has only unique chars
+func Unique(customError error) ValidateFunc {
+	return ValidateFunc(func(password string) error {
+		runes := []rune(password)
+		for idx := range runes {
+			if strings.LastIndexFunc(password, func(r rune) bool {
+				return r == runes[idx]
+			}) != idx {
+				if customError != nil {
+					return customError
+				}
+				return errors.New("the password must contains unique chars")
+			}
+		}
+		return nil
+	})
+}

unique_test.go

@@ -0,0 +1,25 @@
+package validator
+
+import (
+	"errors"
+	"fmt"
+)
+
+func ExampleUnique() {
+	passwordValidator := Unique(nil)
+	fmt.Println(passwordValidator("bui87j"))
+	fmt.Println(passwordValidator("qwerte"))
+	// Output:
+	// <nil>
+	// the password must contains unique chars
+}
+
+func ExampleUnique_customError() {
+	err := errors.New("custom error message")
+	passwordValidator := Unique(err)
+	fmt.Println(passwordValidator("bui87j"))
+	fmt.Println(passwordValidator("qwerte"))
+	// Output:
+	// <nil>
+	// custom error message
+}