autopilot/agent: use NodeScores to select channel candidates

This commit makes the autopilot agent use the new NodeScores heuristic
API to select channel candiates, instead of the Select API. The result
will be similar, but instead of selecting a set of nodes to open
channels to, we get a score based results which can later be used
together with other heuristics to choose nodes to open channels to.

This commit also makes the existing autopilot agent tests compatible
with the new NodeScores API.

autopilot/agent.go

@@ -1,6 +1,7 @@
 package autopilot
 
 import (
+	"bytes"
 	"fmt"
 	"math/rand"
 	"net"
@@ -578,18 +579,49 @@ func (a *Agent) openChans(availableFunds btcutil.Amount, numChans uint32,
 	)
 	a.pendingMtx.Unlock()
 
-	// If we reach this point, then according to our heuristic we
-	// should modify our channel state to tend towards what it
-	// determines to the optimal state. So we'll call Select to get
-	// a fresh batch of attachment directives, passing in the
-	// amount of funds available for us to use.
-	chanCandidates, err := a.cfg.Heuristic.Select(
-		a.cfg.Self, a.cfg.Graph, availableFunds,
-		numChans, nodesToSkip,
+	// Gather the set of all nodes in the graph, except those we
+	// want to skip.
+	selfPubBytes := a.cfg.Self.SerializeCompressed()
+	nodes := make(map[NodeID]struct{})
+	if err := a.cfg.Graph.ForEachNode(func(node Node) error {
+		nID := NodeID(node.PubKey())
+
+		// If we come across ourselves, them we'll continue in
+		// order to avoid attempting to make a channel with
+		// ourselves.
+		if bytes.Equal(nID[:], selfPubBytes) {
+			return nil
+		}
+
+		// Additionally, if this node is in the blacklist, then
+		// we'll skip it.
+		if _, ok := nodesToSkip[nID]; ok {
+			return nil
+		}
+
+		nodes[nID] = struct{}{}
+		return nil
+	}); err != nil {
+		return fmt.Errorf("unable to get graph nodes: %v", err)
+	}
+
+	// Use the heuristic to calculate a score for each node in the
+	// graph.
+	scores, err := a.cfg.Heuristic.NodeScores(
+		a.cfg.Graph, totalChans, availableFunds, nodes,
 	)
 	if err != nil {
-		return fmt.Errorf("Unable to select candidates for "+
-			"attachment: %v", err)
+		return fmt.Errorf("unable to calculate node scores : %v", err)
+	}
+
+	log.Debugf("Got scores for %d nodes", len(scores))
+
+	// Now use the score to make a weighted choice which
+	// nodes to attempt to open channels to.
+	chanCandidates, err := chooseN(int(numChans), scores)
+	if err != nil {
+		return fmt.Errorf("Unable to make weighted choice: %v",
+			err)
 	}
 
 	if len(chanCandidates) == 0 {
@@ -630,7 +662,7 @@ func (a *Agent) openChans(availableFunds btcutil.Amount, numChans uint32,
 		a.pendingConns[nodeID] = struct{}{}
 
 		a.wg.Add(1)
-		go a.executeDirective(chanCandidate)
+		go a.executeDirective(*chanCandidate)
 	}
 	return nil
 }