Add validate function to return error slice

validate.go

@@ -16,29 +16,7 @@ func Validate(password string, minEntropy float64) error {
 		return nil
 	}
 
-	hasReplace := false
-	hasSep := false
-	hasOtherSpecial := false
-	hasLower := false
-	hasUpper := false
-	hasDigits := false
-
-	for _, c := range password {
-		switch {
-		case strings.ContainsRune(replaceChars, c):
-			hasReplace = true
-		case strings.ContainsRune(sepChars, c):
-			hasSep = true
-		case strings.ContainsRune(otherSpecialChars, c):
-			hasOtherSpecial = true
-		case strings.ContainsRune(lowerChars, c):
-			hasLower = true
-		case strings.ContainsRune(upperChars, c):
-			hasUpper = true
-		case strings.ContainsRune(digitsChars, c):
-			hasDigits = true
-		}
-	}
+	hasReplace, hasSep, hasOtherSpecial, hasLower, hasUpper, hasDigits := getCharacterContainment(password)
 
 	allMessages := []string{}
 
@@ -64,3 +42,72 @@ func Validate(password string, minEntropy float64) error {
 
 	return errors.New("insecure password, try using a longer password")
 }
+
+var (
+	// ErrInsufficientSpecialCharacters is returned when the password does not contain enough variety of special characters.
+	ErrInsufficientSpecialCharacters = errors.New("special characters are not used enough")
+	// ErrNoLowercaseLetters is returned when the password does not contain any lowercase letters.
+	ErrNoLowercaseLetters = errors.New("no lowercase letters are used")
+	// ErrNoUppercaseLetters is returned when the password does not contain any uppercase letters.
+	ErrNoUppercaseLetters = errors.New("no uppercase letters are used")
+	// ErrNoDigits is returned when the password does not contain any digits.
+	ErrNoDigits = errors.New("no digits are used")
+	// ErrShortPassword is returned when the password is too short.
+	ErrShortPassword = errors.New("password is too short")
+)
+
+// ValidateWithErrorSlice is similar to Validate but returns
+// a slice of errors that explain the issues with the password.
+// When the password is strong enough, it returns nil.
+// This function is useful for returning multiple errors separately.
+func ValidateWithErrorSlice(password string, minEntropy float64) []error {
+	entropy := getEntropy(password)
+	if entropy >= minEntropy {
+		return nil
+	}
+
+	hasReplace, hasSep, hasOtherSpecial, hasLower, hasUpper, hasDigits := getCharacterContainment(password)
+
+	errs := []error{}
+
+	if !hasOtherSpecial || !hasSep || !hasReplace {
+		errs = append(errs, ErrInsufficientSpecialCharacters)
+	}
+	if !hasLower {
+		errs = append(errs, ErrNoLowercaseLetters)
+	}
+	if !hasUpper {
+		errs = append(errs, ErrNoUppercaseLetters)
+	}
+	if !hasDigits {
+		errs = append(errs, ErrNoDigits)
+	}
+
+	if len(errs) == 0 {
+		return []error{ErrShortPassword}
+	}
+
+	errs = append(errs, ErrShortPassword)
+	return errs
+}
+
+func getCharacterContainment(password string) (hasReplace, hasSep, hasOtherSpecial, hasLower, hasUpper, hasDigits bool) {
+	for _, c := range password {
+		switch {
+		case strings.ContainsRune(replaceChars, c):
+			hasReplace = true
+		case strings.ContainsRune(sepChars, c):
+			hasSep = true
+		case strings.ContainsRune(otherSpecialChars, c):
+			hasOtherSpecial = true
+		case strings.ContainsRune(lowerChars, c):
+			hasLower = true
+		case strings.ContainsRune(upperChars, c):
+			hasUpper = true
+		case strings.ContainsRune(digitsChars, c):
+			hasDigits = true
+		}
+	}
+
+	return
+}

validate_test.go

@@ -33,3 +33,43 @@ func TestValidate(t *testing.T) {
 		t.Errorf("Wanted %v, got %v", expectedError, err)
 	}
 }
+
+func TestValidateWithErrorSlice(t *testing.T) {
+	errs := ValidateWithErrorSlice("mypass", 50)
+	expectedErrors := []error{ErrInsufficientSpecialCharacters, ErrNoUppercaseLetters, ErrNoDigits, ErrShortPassword}
+	testErrorSlice(t, errs, expectedErrors)
+
+	errs = ValidateWithErrorSlice("MYPASS", 50)
+	expectedErrors = []error{ErrInsufficientSpecialCharacters, ErrNoLowercaseLetters, ErrNoDigits, ErrShortPassword}
+	testErrorSlice(t, errs, expectedErrors)
+
+	errs = ValidateWithErrorSlice("mypassword", 4)
+	if errs != nil {
+		t.Errorf("Errs should be nil")
+	}
+
+	errs = ValidateWithErrorSlice("aGoo0dMi#oFChaR2", 80)
+	if errs != nil {
+		t.Errorf("Errs should be nil")
+	}
+
+	expectedErrors = []error{ErrInsufficientSpecialCharacters, ErrNoLowercaseLetters, ErrNoUppercaseLetters, ErrShortPassword}
+	errs = ValidateWithErrorSlice("123", 60)
+	testErrorSlice(t, errs, expectedErrors)
+}
+
+func testErrorSlice(t *testing.T, errs []error, expectedErrors []error) {
+	t.Helper()
+
+	if len(errs) != len(expectedErrors) {
+		t.Errorf("Wanted %v, got %v", expectedErrors, errs)
+		return
+	}
+
+	for i, err := range errs {
+		expectedError := expectedErrors[i]
+		if err.Error() != expectedError.Error() {
+			t.Errorf("Errs[%d]: Wanted %v, got %v", i, expectedError, err)
+		}
+	}
+}