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

selective-vpn-api/app/transport_backends_adapter_systemd_health.go

@@ -0,0 +1,83 @@
+package app
+
+import (
+	"strings"
+)
+
+func (transportSystemdBackend) Health(client TransportClient) transportBackendHealthResult {
+	units, errCode, errMsg := transportSystemdHealthUnits(client)
+	if len(units) == 0 {
+		return transportBackendHealthResult{
+			OK:      false,
+			Code:    errCode,
+			Message: errMsg,
+			Status:  TransportClientDown,
+		}
+	}
+
+	active := 0
+	starting := 0
+	inactive := 0
+	failed := 0
+	unknown := 0
+	issues := make([]string, 0, len(units))
+	for _, unit := range units {
+		stdout, stderr, _, _ := transportRunCommand(transportBackendHealthTimeout, "systemctl", "is-active", unit)
+		state := strings.ToLower(strings.TrimSpace(stdout))
+		switch state {
+		case "active":
+			active++
+		case "activating", "reloading":
+			starting++
+		case "inactive", "deactivating":
+			inactive++
+		case "failed":
+			failed++
+			msg := strings.TrimSpace(stderr)
+			if msg == "" {
+				msg = "systemd unit failed"
+			}
+			issues = append(issues, unit+": "+msg)
+		default:
+			unknown++
+			msg := strings.TrimSpace(stderr)
+			if msg == "" {
+				msg = strings.TrimSpace(stdout)
+			}
+			if msg == "" {
+				msg = "status unknown"
+			}
+			issues = append(issues, unit+": "+msg)
+		}
+	}
+
+	total := len(units)
+	if active == total {
+		res := transportBackendHealthResult{OK: true, Status: TransportClientUp}
+		if latency, _ := transportProbeClientLatency(client); latency > 0 {
+			res.LatencyMS = latency
+		}
+		return res
+	}
+	if active+starting == total {
+		return transportBackendHealthResult{OK: true, Status: TransportClientStarting}
+	}
+	if inactive == total {
+		return transportBackendHealthResult{OK: true, Status: TransportClientDown}
+	}
+	msg := strings.TrimSpace(strings.Join(issues, "; "))
+	if msg == "" {
+		msg = "backend units are not synchronized"
+	}
+	status := TransportClientDegraded
+	if active == 0 && failed == 0 && unknown == 0 {
+		status = TransportClientDown
+	}
+	return transportBackendHealthResult{
+		OK:        false,
+		Code:      "TRANSPORT_BACKEND_HEALTH_FAILED",
+		Message:   msg,
+		Status:    status,
+		Retryable: true,
+	}
+}