feat(internal): add Thoth client and simple ASN checker

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

internal/thoth/asnchecker.go

@@ -0,0 +1,35 @@
+package thoth
+
+import (
+	"context"
+	"net/http"
+	"time"
+
+	iptoasnv1 "github.com/TecharoHQ/thoth-proto/gen/techaro/thoth/iptoasn/v1"
+)
+
+type ASNChecker struct {
+	iptoasn iptoasnv1.IpToASNServiceClient
+	asns    map[int]struct{}
+	hash    string
+}
+
+func (asnc *ASNChecker) Check(r *http.Request) (bool, error) {
+	ctx, cancel := context.WithTimeout(r.Context(), 50*time.Millisecond)
+	defer cancel()
+
+	ipInfo, err := asnc.iptoasn.Lookup(ctx, &iptoasnv1.LookupRequest{
+		IpAddress: r.Header.Get("X-Real-Ip"),
+	})
+	if err != nil {
+		return false, err
+	}
+
+	_, ok := asnc.asns[int(ipInfo.GetAsNumber())]
+
+	return ok, nil
+}
+
+func (asnc *ASNChecker) Hash() string {
+	return asnc.hash
+}