[mle] add RouterTable::LogRouteTable() (#8189)

This commit updates the logging format of the route table. It adds
`LogRouteTable()` method in `RouterTable`.

src/core/thread/mle_router.cpp

@@ -1602,24 +1602,11 @@ void MleRouter::UpdateRoutes(const RouteTlv &aRoute, uint8_t aRouterId)
         ResetAdvertiseInterval();
     }
 
-#if OT_SHOULD_LOG_AT(OT_LOG_LEVEL_INFO)
-
-    VerifyOrExit(changed);
-    LogInfo("Route table updated");
-
-    for (Router &router : Get<RouterTable>().Iterate())
+    if (changed)
     {
-        LogInfo("    %04x -> %04x, cost:%d %d, lqin:%d, lqout:%d, link:%s", router.GetRloc16(),
-                (router.GetNextHop() == kInvalidRouterId) ? 0xffff : Rloc16FromRouterId(router.GetNextHop()),
-                router.GetCost(), mRouterTable.GetLinkCost(router), router.GetLinkQualityIn(),
-                router.GetLinkQualityOut(),
-                router.GetRloc16() == GetRloc16() ? "device" : ToYesNo(router.IsStateValid()));
+        Get<RouterTable>().LogRouteTable();
     }
 
-#else
-    OT_UNUSED_VARIABLE(changed);
-#endif
-
 exit:
     return;
 }

src/core/thread/router_table.cpp

@@ -550,6 +550,47 @@ exit:
 }
 #endif
 
+#if OT_SHOULD_LOG_AT(OT_LOG_LEVEL_INFO)
+void RouterTable::LogRouteTable(void)
+{
+    static constexpr uint16_t kStringSize = 128;
+
+    LogInfo("Route table");
+
+    for (Router &router : Iterate())
+    {
+        String<kStringSize> string;
+
+        string.Append("    %2d 0x%04x", router.GetRouterId(), router.GetRloc16());
+
+        if (router.GetRloc16() == Get<Mle::Mle>().GetRloc16())
+        {
+            string.Append(" - me");
+        }
+        else
+        {
+            if (router.IsStateValid())
+            {
+                string.Append(" - nbr{lq[i/o]:%d/%d cost:%d}", router.GetLinkQualityIn(), router.GetLinkQualityOut(),
+                              GetLinkCost(router));
+            }
+
+            if (router.GetNextHop() != Mle::kInvalidRouterId)
+            {
+                string.Append(" - nexthop{%d cost:%d}", router.GetNextHop(), router.GetCost());
+            }
+        }
+
+        if (router.GetRouterId() == Get<Mle::Mle>().GetLeaderId())
+        {
+            string.Append(" - leader");
+        }
+
+        LogInfo("%s", string.AsCString());
+    }
+}
+#endif
+
 } // namespace ot
 
 #endif // OPENTHREAD_FTD

src/core/thread/router_table.hpp

@@ -344,6 +344,16 @@ public:
     Error SetRouterIdRange(uint8_t aMinRouterId, uint8_t aMaxRouterId);
 #endif
 
+#if OT_SHOULD_LOG_AT(OT_LOG_LEVEL_INFO)
+    /**
+     * This method logs the route table.
+     *
+     */
+    void LogRouteTable(void);
+#else
+    void LogRouteTable(void) {}
+#endif
+
 private:
     class IteratorBuilder : public InstanceLocator
     {