add auth lib

credentials/validation.go

@@ -0,0 +1,42 @@
+package credentials
+
+import (
+	"regexp"
+	"strings"
+)
+
+var emailRegex = regexp.MustCompile(`^[A-Za-z0-9._%+\-]+@[A-Za-z0-9.\-]+\.[A-Za-z]{2,}$`)
+var usernameAllowedRegex = regexp.MustCompile(`^[A-Za-z0-9._-]{3,20}$`)
+
+const bcryptMaxPasswordBytes = 72
+
+// At least one letter.
+var passwordLetterRegex = regexp.MustCompile(`[A-Za-z]`)
+
+// At least one number or special symbol (non-letter).
+var passwordNonLetterRegex = regexp.MustCompile(`[^A-Za-z]`)
+
+func IsValidEmail(email string) bool {
+	return emailRegex.MatchString(email)
+}
+
+func IsValidUsername(username string) bool {
+	if !usernameAllowedRegex.MatchString(username) {
+		return false
+	}
+
+	return !strings.Contains(username, "..") &&
+		!strings.Contains(username, "--") &&
+		!strings.Contains(username, "__")
+}
+
+func IsValidPassword(password string) bool {
+	return len(password) >= 12 &&
+		IsPasswordWithinBcryptLimit(password) &&
+		passwordLetterRegex.MatchString(password) &&
+		passwordNonLetterRegex.MatchString(password)
+}
+
+func IsPasswordWithinBcryptLimit(password string) bool {
+	return len([]byte(password)) <= bcryptMaxPasswordBytes
+}