routing+refactor: remove the need to give CachedGraph source node access

In preparation for the next commit.

routing/graph.go

@@ -25,9 +25,8 @@ type Graph interface {
 // CachedGraph is a Graph implementation that retrieves from the
 // database.
 type CachedGraph struct {
-	graph  *channeldb.ChannelGraph
-	tx     kvdb.RTx
-	source route.Vertex
+	graph *channeldb.ChannelGraph
+	tx    kvdb.RTx
 }
 
 // A compile time assertion to make sure CachedGraph implements the Graph
@@ -36,18 +35,15 @@ var _ Graph = (*CachedGraph)(nil)
 
 // NewCachedGraph instantiates a new db-connected routing graph. It implicitly
 // instantiates a new read transaction.
-func NewCachedGraph(sourceNode *channeldb.LightningNode,
-	graph *channeldb.ChannelGraph) (*CachedGraph, error) {
-
+func NewCachedGraph(graph *channeldb.ChannelGraph) (*CachedGraph, error) {
 	tx, err := graph.NewPathFindTx()
 	if err != nil {
 		return nil, err
 	}
 
 	return &CachedGraph{
-		graph:  graph,
-		tx:     tx,
-		source: sourceNode.PubKeyBytes,
+		graph: graph,
+		tx:    tx,
 	}, nil
 }
 
@@ -82,16 +78,16 @@ func (g *CachedGraph) FetchNodeFeatures(nodePub route.Vertex) (
 
 // FetchAmountPairCapacity determines the maximal public capacity between two
 // nodes depending on the amount we try to send.
-func (g *CachedGraph) FetchAmountPairCapacity(nodeFrom, nodeTo route.Vertex,
+func FetchAmountPairCapacity(graph Graph, source, nodeFrom, nodeTo route.Vertex,
 	amount lnwire.MilliSatoshi) (btcutil.Amount, error) {
 
 	// Create unified edges for all incoming connections.
 	//
 	// Note: Inbound fees are not used here because this method is only used
 	// by a deprecated router rpc.
-	u := newNodeEdgeUnifier(g.source, nodeTo, false, nil)
+	u := newNodeEdgeUnifier(source, nodeTo, false, nil)
 
-	err := u.addGraphPolicies(g)
+	err := u.addGraphPolicies(graph)
 	if err != nil {
 		return 0, err
 	}

routing/mock_graph_test.go

@@ -227,31 +227,6 @@ func (m *mockGraph) FetchNodeFeatures(nodePub route.Vertex) (
 	return lnwire.EmptyFeatureVector(), nil
 }
 
-// FetchAmountPairCapacity returns the maximal capacity between nodes in the
-// graph.
-//
-// NOTE: Part of the Graph interface.
-func (m *mockGraph) FetchAmountPairCapacity(nodeFrom, nodeTo route.Vertex,
-	amount lnwire.MilliSatoshi) (btcutil.Amount, error) {
-
-	var capacity btcutil.Amount
-
-	cb := func(channel *channeldb.DirectedChannel) error {
-		if channel.OtherNode == nodeTo {
-			capacity = channel.Capacity
-		}
-
-		return nil
-	}
-
-	err := m.ForEachNodeChannel(nodeFrom, cb)
-	if err != nil {
-		return 0, err
-	}
-
-	return capacity, nil
-}
-
 // htlcResult describes the resolution of an htlc. If failure is nil, the htlc
 // was settled.
 type htlcResult struct {

routing/pathfind_test.go

@@ -3201,7 +3201,7 @@ func dbFindPath(graph *channeldb.ChannelGraph,
 		return nil, err
 	}
 
-	routingGraph, err := NewCachedGraph(sourceNode, graph)
+	routingGraph, err := NewCachedGraph(graph)
 	if err != nil {
 		return nil, err
 	}

routing/payment_session_source.go

@@ -47,7 +47,7 @@ type SessionSource struct {
 // getRoutingGraph returns a routing graph and a clean-up function for
 // pathfinding.
 func (m *SessionSource) getRoutingGraph() (Graph, func(), error) {
-	routingTx, err := NewCachedGraph(m.SourceNode, m.Graph)
+	routingTx, err := NewCachedGraph(m.Graph)
 	if err != nil {
 		return nil, nil, err
 	}

routing/router.go

@@ -517,8 +517,7 @@ func New(cfg Config) (*ChannelRouter, error) {
 	r := &ChannelRouter{
 		cfg: &cfg,
 		cachedGraph: &CachedGraph{
-			graph:  cfg.Graph,
-			source: selfNode.PubKeyBytes,
+			graph: cfg.Graph,
 		},
 		networkUpdates:    make(chan *routingMsg),
 		topologyClients:   &lnutils.SyncMap[uint64, *topologyClient]{},

rpcserver.go

@@ -691,9 +691,7 @@ func (r *rpcServer) addDeps(s *server, macService *macaroons.Service,
 		FetchAmountPairCapacity: func(nodeFrom, nodeTo route.Vertex,
 			amount lnwire.MilliSatoshi) (btcutil.Amount, error) {
 
-			routingGraph, err := routing.NewCachedGraph(
-				selfNode, graph,
-			)
+			routingGraph, err := routing.NewCachedGraph(graph)
 			if err != nil {
 				return 0, err
 			}
@@ -706,8 +704,9 @@ func (r *rpcServer) addDeps(s *server, macService *macaroons.Service,
 				}
 			}()
 
-			return routingGraph.FetchAmountPairCapacity(
-				nodeFrom, nodeTo, amount,
+			return routing.FetchAmountPairCapacity(
+				routingGraph, selfNode.PubKeyBytes, nodeFrom,
+				nodeTo, amount,
 			)
 		},
 		FetchChannelEndpoints: func(chanID uint64) (route.Vertex,