format systemd status as time deltas from now

llarp/router/router.cpp

@@ -870,10 +870,11 @@ namespace llarp
            << NumberOfConnectedRouters() << "/" << NumberOfConnectedClients() << " | "
            << pathContext().CurrentTransitPaths() << " active paths | "
            << "block " << (m_lokidRpcClient ? m_lokidRpcClient->BlockHeight() : 0) << " | gossip: "
-           << "(next/last) " << _rcGossiper.NextGossipAt() << "/";
+           << "(next/last) " << time_delta<std::chrono::seconds>{_rcGossiper.NextGossipAt()}
+           << " / ";
         if (auto maybe = _rcGossiper.LastGossipAt())
         {
-          ss << *maybe;
+          ss << time_delta<std::chrono::seconds>{*maybe};
         }
         else
         {

llarp/util/time.hpp

@@ -29,4 +29,33 @@ namespace llarp
   std::ostream&
   operator<<(std::ostream& out, const TimePoint_t& t);
 
+  template <typename Time_Duration>
+  struct time_delta
+  {
+    const TimePoint_t at;
+
+    std::ostream&
+    operator()(std::ostream& out) const
+    {
+      const auto dlt = std::chrono::duration_cast<Time_Duration>(TimePoint_t::clock::now() - at);
+      if (dlt > 0s)
+        return out << std::chrono::duration_cast<Duration_t>(dlt) << " ago ";
+      else if (dlt < 0s)
+        return out << "in " << std::chrono::duration_cast<Duration_t>(-dlt);
+      else
+        return out << "now";
+    }
+  };
+
+  inline std::ostream&
+  operator<<(std::ostream& out, const time_delta<std::chrono::seconds>& td)
+  {
+    return td(out);
+  }
+
+  inline std::ostream&
+  operator<<(std::ostream& out, const time_delta<std::chrono::milliseconds>& td)
+  {
+    return td(out);
+  }
 }  // namespace llarp