refactor: move lib/policy/config to lib/config

Signed-off-by: Xe Iaso <me@xeiaso.net>

lib/config/asn.go

@@ -0,0 +1,44 @@
+package config
+
+import (
+	"errors"
+	"fmt"
+)
+
+var (
+	ErrPrivateASN = errors.New("bot.ASNs: you have specified a private use ASN")
+)
+
+type ASNs struct {
+	Match []uint32 `json:"match"`
+}
+
+func (a *ASNs) Valid() error {
+	var errs []error
+
+	for _, asn := range a.Match {
+		if isPrivateASN(asn) {
+			errs = append(errs, fmt.Errorf("%w: %d is private (see RFC 6996)", ErrPrivateASN, asn))
+		}
+	}
+
+	if len(errs) != 0 {
+		return fmt.Errorf("bot.ASNs: invalid ASN settings: %w", errors.Join(errs...))
+	}
+
+	return nil
+}
+
+// isPrivateASN checks if an ASN is in the private use area.
+//
+// Based on RFC 6996 and IANA allocations.
+func isPrivateASN(asn uint32) bool {
+	switch {
+	case asn >= 64512 && asn <= 65534:
+		return true
+	case asn >= 4200000000 && asn <= 4294967294:
+		return true
+	default:
+		return false
+	}
+}