fix: preserve live Nginx entry when saved draft differs

backend/internal/nginxgateway/gateway.go

@@ -12,6 +12,8 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"regexp"
+	"strconv"
 	"strings"
 	"sync/atomic"
 	"time"
@@ -32,6 +34,45 @@ const (
 
 var running atomic.Bool
 
+var managedDomain = regexp.MustCompile(`(?m)^\s*server_name ([a-z0-9.-]+);$`)
+var managedHTTPPort = regexp.MustCompile(`(?m)^\s*listen ([0-9]+) default_server;$`)
+var managedHTTPSPort = regexp.MustCompile(`(?m)^\s*listen ([0-9]+) ssl default_server;$`)
+
+// ManagedEntry reads the actual public address from this application's Nginx
+// site. It does not trust a persisted draft when the two differ.
+func ManagedEntry() (nginxconfig.RenderOptions, error) {
+	data, err := os.ReadFile(sitePath)
+	if err != nil {
+		return nginxconfig.RenderOptions{}, err
+	}
+	return parseManagedEntry(string(data))
+}
+
+func parseManagedEntry(body string) (nginxconfig.RenderOptions, error) {
+	scheme := "http"
+	portPattern := managedHTTPPort
+	if strings.Contains(body, "# Add only after the certificate exists.") {
+		scheme, portPattern = "https", managedHTTPSPort
+	} else if !strings.Contains(body, "# Plain HTTP public entry") {
+		return nginxconfig.RenderOptions{}, errors.New("站点不是 opsx-vpn 托管配置")
+	}
+	domains := managedDomain.FindAllStringSubmatch(body, -1)
+	ports := portPattern.FindStringSubmatch(body)
+	if len(domains) == 0 || len(ports) != 2 || !tlsservice.ValidDomain(domains[0][1]) {
+		return nginxconfig.RenderOptions{}, errors.New("无法识别托管站点的公网地址")
+	}
+	for _, match := range domains[1:] {
+		if match[1] != domains[0][1] {
+			return nginxconfig.RenderOptions{}, errors.New("托管站点包含多个不同域名")
+		}
+	}
+	port, err := strconv.Atoi(ports[1])
+	if err != nil || port < 1 || port > 65535 {
+		return nginxconfig.RenderOptions{}, errors.New("托管站点端口无效")
+	}
+	return nginxconfig.RenderOptions{Domain: domains[0][1], Scheme: scheme, Port: port}, nil
+}
+
 func Begin() bool   { return running.CompareAndSwap(false, true) }
 func End()          { running.Store(false) }
 func Running() bool { return running.Load() }