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

selective-vpn-api/app/resolver/error_policy.go

@@ -0,0 +1,53 @@
+package resolver
+
+import (
+	"os"
+	"strings"
+)
+
+func SmartDNSFallbackForTimeoutEnabled() bool {
+	switch strings.ToLower(strings.TrimSpace(os.Getenv("RESOLVE_SMARTDNS_TIMEOUT_FALLBACK"))) {
+	case "1", "true", "yes", "on":
+		return true
+	case "0", "false", "no", "off":
+		return false
+	default:
+		return false
+	}
+}
+
+func ShouldFallbackToSmartDNS(stats DNSMetrics) bool {
+	if stats.OK > 0 {
+		return false
+	}
+	if stats.NXDomain > 0 {
+		return false
+	}
+	if stats.Timeout > 0 || stats.Temporary > 0 {
+		return true
+	}
+	return stats.Other > 0
+}
+
+func ClassifyHostErrorKind(stats DNSMetrics) (DNSErrorKind, bool) {
+	if stats.Timeout > 0 {
+		return DNSErrorTimeout, true
+	}
+	if stats.Temporary > 0 {
+		return DNSErrorTemporary, true
+	}
+	if stats.Other > 0 {
+		return DNSErrorOther, true
+	}
+	if stats.NXDomain > 0 {
+		return DNSErrorNXDomain, true
+	}
+	return "", false
+}
+
+func ShouldUseStaleOnError(stats DNSMetrics) bool {
+	if stats.OK > 0 {
+		return false
+	}
+	return stats.Timeout > 0 || stats.Temporary > 0 || stats.Other > 0
+}