From 980d8b4003670b1b2f7ac05604f385638e84a196 Mon Sep 17 00:00:00 2001
From: Thomas HUET <thomas.huet@acinq.fr>
Date: Wed, 5 Mar 2025 12:06:30 +0100
Subject: [PATCH] comments

---
 .../main/scala/fr/acinq/eclair/router/Graph.scala    | 12 ++----------
 .../main/scala/fr/acinq/eclair/router/Router.scala   |  4 ----
 .../scala/fr/acinq/eclair/router/GraphSpec.scala     | 10 +++++-----
 3 files changed, 7 insertions(+), 19 deletions(-)

diff --git a/eclair-core/src/main/scala/fr/acinq/eclair/router/Graph.scala b/eclair-core/src/main/scala/fr/acinq/eclair/router/Graph.scala
index 531218fc80..832fc0d11a 100644
--- a/eclair-core/src/main/scala/fr/acinq/eclair/router/Graph.scala
+++ b/eclair-core/src/main/scala/fr/acinq/eclair/router/Graph.scala
@@ -436,6 +436,7 @@ object Graph {
 
   /**
    * Find non-overlapping (no vertices shared) payment paths that support route blinding
+   * This is used to build blinded routes for Bolt12 invoices where `sourceNode` is the first node of the blinded path and `targetNode` is ourself.
    *
    * @param pathsToFind Number of paths to find. We may return fewer paths if we couldn't find more non-overlapping ones.
    */
@@ -457,6 +458,7 @@ object Graph {
         case Some(path) =>
           val weight = pathWeight(sourceNode, path, amount, currentBlockHeight, wr, includeLocalChannelCost = true)
           paths += WeightedPath(path, weight)
+          // Additional paths must keep using the source and target nodes, but shouldn't use any of the same intermediate nodes.
           verticesToIgnore.addAll(path.drop(1).map(_.desc.a))
         case None => return paths.toSeq
       }
@@ -747,16 +749,6 @@ object Graph {
           }
         }
       }
-
-      /**
-       * @return a node that's very central in the graph, to be used as the first node in blinded routes.
-       */
-      def centralNode: PublicKey = {
-        vertices.view.mapValues(v => {
-          // We only consider channels larger than 0.1 BTC and count the number of connected nodes.
-          v.incomingEdges.values.filter(_.capacity > Satoshi(10_000_000)).map(_.desc.a).toSet.size
-        }).maxBy(_._2)._1
-      }
     }
 
     object DirectedGraph {
diff --git a/eclair-core/src/main/scala/fr/acinq/eclair/router/Router.scala b/eclair-core/src/main/scala/fr/acinq/eclair/router/Router.scala
index 93033e9208..e4bfd986ae 100644
--- a/eclair-core/src/main/scala/fr/acinq/eclair/router/Router.scala
+++ b/eclair-core/src/main/scala/fr/acinq/eclair/router/Router.scala
@@ -247,10 +247,6 @@ class Router(val nodeParams: NodeParams, watcher: typed.ActorRef[ZmqWatcher.Comm
     case Event(r: MessageRouteRequest, d) =>
       stay() using RouteCalculation.handleMessageRouteRequest(d, nodeParams.currentBlockHeight, r, nodeParams.routerConf.messageRouteParams)
 
-    case Event(r: GetCentralNode , d) =>
-      r.replyTo ! d.graphWithBalances.graph.centralNode
-      stay()
-
     case Event(GetNodeId(replyTo, shortChannelId, isNode1), d) =>
       replyTo ! d.channels.get(shortChannelId).map(channel => if (isNode1) channel.nodeId1 else channel.nodeId2)
       stay()
diff --git a/eclair-core/src/test/scala/fr/acinq/eclair/router/GraphSpec.scala b/eclair-core/src/test/scala/fr/acinq/eclair/router/GraphSpec.scala
index d6b847f831..c84799c77f 100644
--- a/eclair-core/src/test/scala/fr/acinq/eclair/router/GraphSpec.scala
+++ b/eclair-core/src/test/scala/fr/acinq/eclair/router/GraphSpec.scala
@@ -485,11 +485,11 @@ class GraphSpec extends AnyFunSuite {
 
      +----- B ------+
      |              |
-     A -- C -- D -- H
-     |              |
-     +--- E -- F ---+
-          |         |
-          +--- G ---+
+     A -- C -- D -- H --+
+     |              |   |
+     +--- E -- F ---+   |
+          |             |
+          +--- G -------+
      */
     val graph = DirectedGraph(Seq(
       makeEdge(1L, a, b, 0 msat, 0),