Refactor: Use struct Int32Range widely (#3867)

https://github.com/XTLS/Xray-core/pull/3867#issuecomment-2412847316

infra/conf/common.go

@@ -246,43 +246,76 @@ func (v *User) Build() *protocol.User {
 
 // Int32Range deserializes from "1-2" or 1, so can deserialize from both int and number.
 // Negative integers can be passed as sentinel values, but do not parse as ranges.
+// Value will be exchanged if From > To, use .Left and .Right to get original value if need.
 type Int32Range struct {
-	From int32
-	To   int32
+	Left  int32
+	Right int32
+	From  int32
+	To    int32
 }
 
 func (v *Int32Range) UnmarshalJSON(data []byte) error {
+	defer v.ensureOrder()
 	var str string
 	var rawint int32
 	if err := json.Unmarshal(data, &str); err == nil {
-		// for number in string format like "114" or "-1"
-		if value, err := strconv.Atoi(str); err == nil {
-			v.From = int32(value)
-			v.To = int32(value)
+		left, right, err := ParseRangeString(str)
+		if err == nil {
+			v.Left, v.Right = int32(left), int32(right)
 			return nil
 		}
-		// for empty "", we treat it as 0
-		if str == "" {
-			v.From = 0
-			v.To = 0
-			return nil
-		}
-		// for range value, like "114-514"
-		pair := strings.SplitN(str, "-", 2)
-		if len(pair) == 2 {
-			from, err := strconv.Atoi(pair[0])
-			to, err2 := strconv.Atoi(pair[1])
-			if err == nil && err2 == nil {
-				v.From = int32(from)
-				v.To = int32(to)
-				return nil
-			}
-		}
 	} else if err := json.Unmarshal(data, &rawint); err == nil {
-		v.From = rawint
-		v.To = rawint
+		v.Left = rawint
+		v.Right = rawint
 		return nil
 	}
 
 	return errors.New("Invalid integer range, expected either string of form \"1-2\" or plain integer.")
 }
+
+// ensureOrder() gives value to .From & .To and make sure .From < .To
+func (r *Int32Range) ensureOrder() {
+	r.From, r.To = r.Left, r.Right
+	if r.From > r.To {
+		r.From, r.To = r.To, r.From
+	}
+}
+
+// "-114-514"   →  ["-114","514"]
+// "-1919--810" →  ["-1919","-810"]
+func splitFromSecondDash(s string) []string {
+	parts := strings.SplitN(s, "-", 3)
+	if len(parts) < 3 {
+		return []string{s}
+	}
+	return []string{parts[0] + "-" + parts[1], parts[2]}
+}
+
+// Parse rang in string. Support negative number.
+// eg: "114-514" "-114-514" "-1919--810" "114514" ""(return 0)
+func ParseRangeString(str string) (int, int, error) {
+	// for number in string format like "114" or "-1"
+	if value, err := strconv.Atoi(str); err == nil {
+		return value, value, nil
+	}
+	// for empty "", we treat it as 0
+	if str == "" {
+		return 0, 0, nil
+	}
+	// for range value, like "114-514"
+	var pair []string
+	// Process sth like "-114-514" "-1919--810"
+	if strings.HasPrefix(str, "-") {
+		pair = splitFromSecondDash(str)
+	} else {
+		pair = strings.SplitN(str, "-", 2)
+	}
+	if len(pair) == 2 {
+		left, err := strconv.Atoi(pair[0])
+		right, err2 := strconv.Atoi(pair[1])
+		if err == nil && err2 == nil {
+			return left, right, nil
+		}
+	}
+	return 0, 0, errors.New("invalid range string: ", str)
+}