autopilot: remove the ForEachChannel method from Node interface

diff --git a/autopilot/graph.go b/autopilot/graph.go
index 68b9647..a2a2e02 100644
--- a/autopilot/graph.go
+++ b/autopilot/graph.go
@@ -10,7 +10,6 @@ import (
 	"github.com/btcsuite/btcd/btcec/v2/ecdsa"
 	"github.com/btcsuite/btcd/btcutil"
 	graphdb "github.com/lightningnetwork/lnd/graph/db"
-	"github.com/lightningnetwork/lnd/graph/db/models"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing/route"
 )
@@ -51,7 +50,6 @@ func ChannelGraphFromDatabase(db GraphSource) ChannelGraph {
 // channeldb.LightningNode. The wrapper method implement the autopilot.Node
 // interface.
 type dbNode struct {
-	tx    graphdb.NodeRTx
 	pub   [33]byte
 	addrs []net.Addr
 }
@@ -77,39 +75,6 @@ func (d *dbNode) Addrs() []net.Addr {
 	return d.addrs
 }
 
-// ForEachChannel is a higher-order function that will be used to iterate
-// through all edges emanating from/to the target node. For each active
-// channel, this function should be called with the populated ChannelEdge that
-// describes the active channel.
-//
-// NOTE: Part of the autopilot.Node interface.
-func (d *dbNode) ForEachChannel(ctx context.Context,
-	cb func(context.Context, ChannelEdge) error) error {
-
-	return d.tx.ForEachChannel(func(ei *models.ChannelEdgeInfo, ep,
-		_ *models.ChannelEdgePolicy) error {
-
-		// Skip channels for which no outgoing edge policy is available.
-		//
-		// TODO(joostjager): Ideally the case where channels have a nil
-		// policy should be supported, as autopilot is not looking at
-		// the policies. For now, it is not easily possible to get a
-		// reference to the other end LightningNode object without
-		// retrieving the policy.
-		if ep == nil {
-			return nil
-		}
-
-		edge := ChannelEdge{
-			ChanID:   lnwire.NewShortChanIDFromInt(ep.ChannelID),
-			Capacity: ei.Capacity,
-			Peer:     ep.ToNode,
-		}
-
-		return cb(ctx, edge)
-	})
-}
-
 // ForEachNode is a higher-order function that should be called once for each
 // connected node within the channel graph. If the passed callback returns an
 // error, then execution should be terminated.
@@ -127,7 +92,6 @@ func (d *databaseChannelGraph) ForEachNode(ctx context.Context,
 		}
 
 		node := &dbNode{
-			tx:    nodeTx,
 			pub:   nodeTx.Node().PubKeyBytes,
 			addrs: nodeTx.Node().Addresses,
 		}
@@ -223,30 +187,6 @@ func (nc dbNodeCached) Addrs() []net.Addr {
 	return []net.Addr{}
 }
 
-// ForEachChannel is a higher-order function that will be used to iterate
-// through all edges emanating from/to the target node. For each active
-// channel, this function should be called with the populated ChannelEdge that
-// describes the active channel.
-//
-// NOTE: Part of the autopilot.Node interface.
-func (nc dbNodeCached) ForEachChannel(ctx context.Context,
-	cb func(context.Context, ChannelEdge) error) error {
-
-	for cid, channel := range nc.channels {
-		edge := ChannelEdge{
-			ChanID:   lnwire.NewShortChanIDFromInt(cid),
-			Capacity: channel.Capacity,
-			Peer:     channel.OtherNode,
-		}
-
-		if err := cb(ctx, edge); err != nil {
-			return err
-		}
-	}
-
-	return nil
-}
-
 // ForEachNode is a higher-order function that should be called once for each
 // connected node within the channel graph. If the passed callback returns an
 // error, then execution should be terminated.
@@ -343,24 +283,6 @@ func (m memNode) Addrs() []net.Addr {
 	return m.addrs
 }
 
-// ForEachChannel is a higher-order function that will be used to iterate
-// through all edges emanating from/to the target node. For each active
-// channel, this function should be called with the populated ChannelEdge that
-// describes the active channel.
-//
-// NOTE: Part of the autopilot.Node interface.
-func (m memNode) ForEachChannel(ctx context.Context,
-	cb func(context.Context, ChannelEdge) error) error {
-
-	for _, channel := range m.chans {
-		if err := cb(ctx, channel); err != nil {
-			return err
-		}
-	}
-
-	return nil
-}
-
 // Median returns the median value in the slice of Amounts.
 func Median(vals []btcutil.Amount) btcutil.Amount {
 	sort.Slice(vals, func(i, j int) bool {
diff --git a/autopilot/interface.go b/autopilot/interface.go
index f35f319..1554b03 100644
--- a/autopilot/interface.go
+++ b/autopilot/interface.go
@@ -31,13 +31,6 @@ type Node interface {
 	// Addrs returns a slice of publicly reachable public TCP addresses
 	// that the peer is known to be listening on.
 	Addrs() []net.Addr
-
-	// ForEachChannel is a higher-order function that will be used to
-	// iterate through all edges emanating from/to the target node. For
-	// each active channel, this function should be called with the
-	// populated ChannelEdge that describes the active channel.
-	ForEachChannel(context.Context, func(context.Context,
-		ChannelEdge) error) error
 }
 
 // LocalChannel is a simple struct which contains relevant details of a
diff --git a/autopilot/prefattach.go b/autopilot/prefattach.go
index e9a9c53..267c13d 100644
--- a/autopilot/prefattach.go
+++ b/autopilot/prefattach.go
@@ -89,26 +89,26 @@ func (p *PrefAttachment) NodeScores(ctx context.Context, g ChannelGraph,
 		allChans  []btcutil.Amount
 		seenChans = make(map[uint64]struct{})
 	)
-	if err := g.ForEachNode(ctx, func(ctx context.Context, n Node) error {
-		err := n.ForEachChannel(ctx, func(_ context.Context,
-			e ChannelEdge) error {
-
-			if _, ok := seenChans[e.ChanID.ToUint64()]; ok {
-				return nil
+	err := g.ForEachNodesChannels(
+		ctx, func(_ context.Context, node Node,
+			channels []*ChannelEdge) error {
+
+			for _, e := range channels {
+				if _, ok := seenChans[e.ChanID.ToUint64()]; ok {
+					continue
+				}
+				seenChans[e.ChanID.ToUint64()] = struct{}{}
+				allChans = append(allChans, e.Capacity)
 			}
-			seenChans[e.ChanID.ToUint64()] = struct{}{}
-			allChans = append(allChans, e.Capacity)
-			return nil
-		})
-		if err != nil {
-			return err
-		}
 
-		return nil
-	}, func() {
-		allChans = nil
-		clear(seenChans)
-	}); err != nil {
+			return nil
+		},
+		func() {
+			allChans = nil
+			clear(seenChans)
+		},
+	)
+	if err != nil {
 		return nil, err
 	}
 
@@ -120,55 +120,59 @@ func (p *PrefAttachment) NodeScores(ctx context.Context, g ChannelGraph,
 	// the graph.
 	var maxChans int
 	nodeChanNum := make(map[NodeID]int)
-	if err := g.ForEachNode(ctx, func(ctx context.Context, n Node) error {
-		var nodeChans int
-		err := n.ForEachChannel(ctx, func(_ context.Context,
-			e ChannelEdge) error {
-
-			// Since connecting to nodes with a lot of small
-			// channels actually worsens our connectivity in the
-			// graph (we will potentially waste time trying to use
-			// these useless channels in path finding), we decrease
-			// the counter for such channels.
-			if e.Capacity <
-				medianChanSize/minMedianChanSizeFraction {
-
-				nodeChans--
-				return nil
+	err = g.ForEachNodesChannels(
+		ctx, func(ctx context.Context, node Node,
+			edges []*ChannelEdge) error {
+
+			var nodeChans int
+			for _, e := range edges {
+				// Since connecting to nodes with a lot of small
+				// channels actually worsens our connectivity in
+				// the graph (we will potentially waste time
+				// trying to use these useless channels in path
+				// finding), we decrease the counter for such
+				// channels.
+				//
+				//nolint:ll
+				if e.Capacity <
+					medianChanSize/minMedianChanSizeFraction {
+
+					nodeChans--
+
+					continue
+				}
+
+				// Larger channels we count.
+				nodeChans++
 			}
 
-			// Larger channels we count.
-			nodeChans++
-			return nil
-		})
-		if err != nil {
-			return err
-		}
-
-		// We keep track of the highest-degree node we've seen, as this
-		// will be given the max score.
-		if nodeChans > maxChans {
-			maxChans = nodeChans
-		}
+			// We keep track of the highest-degree node we've seen,
+			// as this will be given the max score.
+			if nodeChans > maxChans {
+				maxChans = nodeChans
+			}
 
-		// If this node is not among our nodes to score, we can return
-		// early.
-		nID := NodeID(n.PubKey())
-		if _, ok := nodes[nID]; !ok {
-			log.Tracef("Node %x not among nodes to score, "+
-				"ignoring", nID[:])
-			return nil
-		}
+			// If this node is not among our nodes to score, we can
+			// return early.
+			nID := NodeID(node.PubKey())
+			if _, ok := nodes[nID]; !ok {
+				log.Tracef("Node %x not among nodes to score, "+
+					"ignoring", nID[:])
+				return nil
+			}
 
-		// Otherwise we'll record the number of channels.
-		nodeChanNum[nID] = nodeChans
-		log.Tracef("Counted %v channels for node %x", nodeChans, nID[:])
+			// Otherwise we'll record the number of channels.
+			nodeChanNum[nID] = nodeChans
+			log.Tracef("Counted %v channels for node %x", nodeChans,
+				nID[:])
 
-		return nil
-	}, func() {
-		maxChans = 0
-		clear(nodeChanNum)
-	}); err != nil {
+			return nil
+		}, func() {
+			maxChans = 0
+			clear(nodeChanNum)
+		},
+	)
+	if err != nil {
 		return nil, err
 	}
 
diff --git a/autopilot/prefattach_test.go b/autopilot/prefattach_test.go
index a9f67f7..f0f3513 100644
--- a/autopilot/prefattach_test.go
+++ b/autopilot/prefattach_test.go
@@ -242,25 +242,23 @@ func TestPrefAttachmentSelectGreedyAllocation(t *testing.T) {
 			numNodes := 0
 			twoChans := false
 			nodes := make(map[NodeID]struct{})
-			err = graph.ForEachNode(
-				ctx, func(ctx context.Context, n Node) error {
+			err = graph.ForEachNodesChannels(
+				ctx, func(_ context.Context, node Node,
+					edges []*ChannelEdge) error {
+
 					numNodes++
-					nodes[n.PubKey()] = struct{}{}
+					nodes[node.PubKey()] = struct{}{}
 					numChans := 0
-					err := n.ForEachChannel(ctx,
-						func(_ context.Context, c ChannelEdge) error { //nolint:ll
-							numChans++
-							return nil
-						},
-					)
-					if err != nil {
-						return err
+
+					for range edges {
+						numChans++
 					}
 
 					twoChans = twoChans || (numChans == 2)
 
 					return nil
-				}, func() {
+				},
+				func() {
 					numNodes = 0
 					twoChans = false
 					clear(nodes)
diff --git a/autopilot/simple_graph.go b/autopilot/simple_graph.go
index 32c4559..44f5149 100644
--- a/autopilot/simple_graph.go
+++ b/autopilot/simple_graph.go
@@ -50,20 +50,17 @@ func NewSimpleGraph(ctx context.Context, g ChannelGraph) (*SimpleGraph, error) {
 
 	// Iterate over each node and each channel and update the adj and the
 	// node index.
-	err := g.ForEachNode(ctx, func(ctx context.Context, node Node) error {
-		u := getNodeIndex(node.PubKey())
-
-		return node.ForEachChannel(
-			ctx, func(_ context.Context,
-				edge ChannelEdge) error {
+	err := g.ForEachNodesChannels(ctx, func(_ context.Context,
+		node Node, channels []*ChannelEdge) error {
 
-				v := getNodeIndex(edge.Peer)
+		u := getNodeIndex(node.PubKey())
 
-				adj[u] = append(adj[u], v)
+		for _, edge := range channels {
+			v := getNodeIndex(edge.Peer)
+			adj[u] = append(adj[u], v)
+		}
 
-				return nil
-			},
-		)
+		return nil
 	}, func() {
 		clear(adj)
 		clear(nodes)