platform: modularize api/gui, add docs-tests-web foundation, and refresh root config

selective-vpn-api/app/dns_settings_handlers_mode.go

@@ -0,0 +1,72 @@
+package app
+
+import (
+	"encoding/json"
+	"io"
+	"net/http"
+	"strings"
+)
+
+// ---------------------------------------------------------------------
+// EN: `handleDNSStatus` is an HTTP handler for dns status.
+// RU: `handleDNSStatus` - HTTP-обработчик для dns status.
+// ---------------------------------------------------------------------
+func handleDNSStatus(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodGet {
+		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+	mode := loadDNSMode()
+	writeJSON(w, http.StatusOK, makeDNSStatusResponse(mode))
+}
+
+// ---------------------------------------------------------------------
+// EN: `handleDNSModeSet` is an HTTP handler for dns mode set.
+// RU: `handleDNSModeSet` - HTTP-обработчик для dns mode set.
+// ---------------------------------------------------------------------
+func handleDNSModeSet(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodPost {
+		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	var req DNSModeRequest
+	if r.Body != nil {
+		defer r.Body.Close()
+		if err := json.NewDecoder(io.LimitReader(r.Body, 1<<20)).Decode(&req); err != nil && err != io.EOF {
+			http.Error(w, "bad json", http.StatusBadRequest)
+			return
+		}
+	}
+
+	mode := loadDNSMode()
+	mode.Mode = normalizeDNSResolverMode(req.Mode, req.ViaSmartDNS)
+	mode.ViaSmartDNS = mode.Mode != DNSModeDirect
+	if strings.TrimSpace(req.SmartDNSAddr) != "" {
+		mode.SmartDNSAddr = req.SmartDNSAddr
+	}
+	if err := saveDNSMode(mode); err != nil {
+		http.Error(w, "write error", http.StatusInternalServerError)
+		return
+	}
+
+	mode = loadDNSMode()
+	writeJSON(w, http.StatusOK, makeDNSStatusResponse(mode))
+}
+
+func makeDNSStatusResponse(mode DNSMode) DNSStatusResponse {
+	rt := smartDNSRuntimeSnapshot()
+	resp := DNSStatusResponse{
+		ViaSmartDNS:    mode.ViaSmartDNS,
+		SmartDNSAddr:   mode.SmartDNSAddr,
+		Mode:           mode.Mode,
+		UnitState:      smartdnsUnitState(),
+		RuntimeNftset:  rt.Enabled,
+		WildcardSource: rt.WildcardSource,
+		RuntimeCfgPath: rt.ConfigPath,
+	}
+	if rt.Message != "" {
+		resp.RuntimeCfgError = rt.Message
+	}
+	return resp
+}