temporary tank-finding algorithm

src/adera/Machines/Rocket.cpp

@@ -244,7 +244,25 @@ Machine& SysMachineRocket::instantiate(ActiveEnt ent, PrototypeMachine config,
     DependRes<ShipResourceType> fuel = pkg.get<ShipResourceType>("fuel");
     if (!fuel.empty())
     {
-        ActiveEnt fuelSource = static_cast<ActiveEnt>(13);
+        // TMP: finds the first non-empty fuel tank in the ship
+        // Only works as long as the fuselage is added before the engine
+
+        ActiveEnt foundTank = entt::null;
+        auto find_fuel = [this, &foundTank](ActiveEnt e)
+        {
+            if (auto* fuel = this->m_scene.reg_try_get<MachineContainer>(e);
+                fuel != nullptr && fuel->check_contents().m_quantity > 0)
+            {
+                foundTank = e;
+                return EHierarchyTraverseStatus::Stop;
+            }
+            return EHierarchyTraverseStatus::Continue;
+        };
+        auto const& parent = m_scene.reg_get<ACompHierarchy>(ent);
+        m_scene.hierarchy_traverse(parent.m_parent, find_fuel);
+        // endTMP
+
+        ActiveEnt fuelSource = foundTank;
         MachineRocket::ResourceInput input = {std::move(fuel), 1.0f, fuelSource};
         inputs.push_back(std::move(input));
     }