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

selective-vpn-api/app/transport_backends.go

@@ -0,0 +1,73 @@
+package app
+
+import (
+	"strings"
+	"time"
+)
+
+const (
+	transportBackendActionTimeout = 20 * time.Second
+	transportBackendHealthTimeout = 5 * time.Second
+	transportBackendProbeTimeout  = 900 * time.Millisecond
+)
+
+var transportSystemdUnitsDir = "/etc/systemd/system"
+
+type transportCommandRunner func(timeout time.Duration, name string, args ...string) (string, string, int, error)
+
+var transportRunCommand transportCommandRunner = runCommandTimeout
+
+type transportBackendActionResult struct {
+	OK        bool
+	Code      string
+	Message   string
+	ExitCode  int
+	Stdout    string
+	Stderr    string
+	Retryable bool
+}
+
+type transportBackendHealthResult struct {
+	OK        bool
+	Code      string
+	Message   string
+	Status    TransportClientStatus
+	LatencyMS int
+	Retryable bool
+}
+
+type transportBackendAdapter interface {
+	ID() string
+	Action(client TransportClient, action string) transportBackendActionResult
+	Health(client TransportClient) transportBackendHealthResult
+	Provision(client TransportClient) transportBackendActionResult
+	Cleanup(client TransportClient) transportBackendActionResult
+}
+
+func selectTransportBackend(client TransportClient) transportBackendAdapter {
+	mode := transportRuntimeMode(client.Config)
+	switch mode {
+	case "exec":
+		// Continue with current runner-based backend selection.
+	case "embedded", "sidecar":
+		return transportUnsupportedRuntimeBackend{mode: mode}
+	default:
+		return transportUnsupportedRuntimeBackend{mode: mode}
+	}
+
+	runner := strings.ToLower(strings.TrimSpace(transportConfigString(client.Config, "runner")))
+	unit := strings.TrimSpace(transportConfigString(client.Config, "unit"))
+	switch runner {
+	case "systemd":
+		return transportSystemdBackend{}
+	case "mock":
+		return transportMockBackend{}
+	case "":
+		if unit != "" {
+			return transportSystemdBackend{}
+		}
+		return transportMockBackend{}
+	default:
+		return transportMockBackend{}
+	}
+}