feat(sub): auto-detect subscription format by User-Agent (Updated) (#5826)

* feat(settings): add subscription format controls

* feat(sub): auto-detect subscription formats

* fix(xray): validate balancer regexes before save

* Revert "fix(xray): validate balancer regexes before save"

This reverts commit 8a208ce71b.

* doc(endpoints): align indent spaces

* doc(settings): improve error message formatting in validateSubUserAgentRegex

- Use NewErrorf with proper formatting instead of NewError with string concatenation
- Add comment explaining the rationale for returning original pattern value
- This preserves the intentional design where empty input is stored as empty
  in the DB and inherited as the runtime default at read time

---------

Co-authored-by: Tomilla <5007859+Tomilla@users.noreply.github.com>
Co-authored-by: Sanaei <ho3ein.sanaei@gmail.com>

internal/web/service/setting.go

@@ -9,6 +9,7 @@ import (
 	"net/http"
 	"os"
 	"reflect"
+	"regexp"
 	"strconv"
 	"strings"
 	"time"
@@ -32,6 +33,13 @@ import (
 //go:embed config.json
 var xrayTemplateConfig string
 
+const (
+	DefaultSubClashUserAgentRegex = `(?i)(clash|mihomo)`
+	DefaultSubJsonUserAgentRegex  = ``
+	DefaultRemarkTemplate         = "{{INBOUND}}-{{EMAIL}}|📊{{TRAFFIC_LEFT}}|⏳{{DAYS_LEFT}}D"
+	maxRegexLength                = 2048
+)
+
 var defaultValueMap = map[string]string{
 	"xrayTemplateConfig": xrayTemplateConfig,
 	"webListen":          "",
@@ -57,7 +65,7 @@ var defaultValueMap = map[string]string{
 	"pageSize":                    "25",
 	"expireDiff":                  "0",
 	"trafficDiff":                 "0",
-	"remarkTemplate":              "{{INBOUND}}-{{EMAIL}}|📊{{TRAFFIC_LEFT}}|⏳{{DAYS_LEFT}}D",
+	"remarkTemplate":              DefaultRemarkTemplate,
 	"timeLocation":                "Local",
 	"tgBotEnable":                 "false",
 	"tgBotToken":                  "",
@@ -73,6 +81,11 @@ var defaultValueMap = map[string]string{
 	"twoFactorToken":              "",
 	"subEnable":                   "true",
 	"subJsonEnable":               "false",
+	"subJsonAutoDetect":           "false",
+	"subJsonAlwaysArray":          "false",
+	"subJsonUserAgentRegex":       "",
+	"subClashAutoDetect":          "false",
+	"subClashUserAgentRegex":      "",
 	"subTitle":                    "",
 	"subSupportUrl":               "",
 	"subProfileUrl":               "",
@@ -707,6 +720,26 @@ func (s *SettingService) GetSubJsonEnable() (bool, error) {
 	return s.getBool("subJsonEnable")
 }
 
+func (s *SettingService) GetSubJsonAutoDetect() (bool, error) {
+	return s.getBool("subJsonAutoDetect")
+}
+
+func (s *SettingService) GetSubJsonAlwaysArray() (bool, error) {
+	return s.getBool("subJsonAlwaysArray")
+}
+
+func (s *SettingService) GetSubJsonUserAgentRegex() (string, error) {
+	return s.getString("subJsonUserAgentRegex")
+}
+
+func (s *SettingService) GetSubClashAutoDetect() (bool, error) {
+	return s.getBool("subClashAutoDetect")
+}
+
+func (s *SettingService) GetSubClashUserAgentRegex() (string, error) {
+	return s.getString("subClashUserAgentRegex")
+}
+
 func (s *SettingService) GetSubTitle() (string, error) {
 	return s.getString("subTitle")
 }
@@ -1119,6 +1152,9 @@ func (s *SettingService) UpdateAllSetting(allSetting *entity.AllSetting, clears
 	if err := validateSettingsURLs(allSetting); err != nil {
 		return err
 	}
+	if err := validateSubUserAgentRegexes(allSetting); err != nil {
+		return err
+	}
 	if err := allSetting.CheckValid(); err != nil {
 		return err
 	}
@@ -1159,6 +1195,48 @@ func (s *SettingService) UpdateAllSetting(allSetting *entity.AllSetting, clears
 	})
 }
 
+func validateSubUserAgentRegexes(allSetting *entity.AllSetting) error {
+	jsonPattern, err := validateSubUserAgentRegex("Xray JSON", allSetting.SubJsonUserAgentRegex, DefaultSubJsonUserAgentRegex)
+	if err != nil {
+		return err
+	}
+	clashPattern, err := validateSubUserAgentRegex("Clash/Mihomo", allSetting.SubClashUserAgentRegex, DefaultSubClashUserAgentRegex)
+	if err != nil {
+		return err
+	}
+	allSetting.SubJsonUserAgentRegex = jsonPattern
+	allSetting.SubClashUserAgentRegex = clashPattern
+	return nil
+}
+
+func validateSubUserAgentRegex(name, pattern, defaultPattern string) (string, error) {
+	pattern = strings.TrimSpace(pattern)
+	effectivePattern := pattern
+	if effectivePattern == "" {
+		effectivePattern = defaultPattern
+	}
+	if len(effectivePattern) > maxRegexLength {
+		return "", common.NewErrorf("%s User-Agent regex must not exceed %d characters", name, maxRegexLength)
+	}
+	if _, err := regexp.Compile(effectivePattern); err != nil {
+		return "", common.NewErrorf("%s User-Agent regex is invalid: %v", name, err)
+	}
+	// Return the original pattern (empty string if cleared) so the caller
+	// can distinguish "user explicitly set empty" from "user set a value".
+	// The empty value is stored in the DB and inherited as runtime default.
+	return pattern, nil
+}
+
+func ValidateRegex(pattern string) error {
+	if len(pattern) > maxRegexLength {
+		return common.NewErrorf("Regular expression must not exceed %d characters", maxRegexLength)
+	}
+	if _, err := regexp.Compile(pattern); err != nil {
+		return common.NewError("Regular expression is invalid:", err)
+	}
+	return nil
+}
+
 func (s *SettingService) preserveRedactedSecrets(allSetting *entity.AllSetting, clears SecretClears) error {
 	if !clears.TgBotToken && strings.TrimSpace(allSetting.TgBotToken) == "" {
 		value, err := s.GetTgBotToken()