routing: add graph interface

routing/graph.go

@@ -1,4 +1,104 @@
 package routing
 
-// TODO(roasbeef): abstract out graph to interface
-//  * add in-memory version of graph for tests
+import (
+	"github.com/coreos/bbolt"
+	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/lnwire"
+	"github.com/lightningnetwork/lnd/routing/route"
+)
+
+// routingGraph is an abstract interface that provides information about nodes
+// and edges to pathfinding.
+type routingGraph interface {
+	// forEachNodeChannel calls the callback for every channel of the given node.
+	forEachNodeChannel(nodePub route.Vertex,
+		cb func(*channeldb.ChannelEdgeInfo, *channeldb.ChannelEdgePolicy,
+			*channeldb.ChannelEdgePolicy) error) error
+
+	// sourceNode returns the source node of the graph.
+	sourceNode() route.Vertex
+
+	// fetchNodeFeatures returns the features of the given node.
+	fetchNodeFeatures(nodePub route.Vertex) (*lnwire.FeatureVector, error)
+}
+
+// dbRoutingTx is a routingGraph implementation that retrieves from the
+// database.
+type dbRoutingTx struct {
+	graph  *channeldb.ChannelGraph
+	tx     *bbolt.Tx
+	source route.Vertex
+}
+
+// newDbRoutingTx instantiates a new db-connected routing graph. It implictly
+// instantiates a new read transaction.
+func newDbRoutingTx(graph *channeldb.ChannelGraph) (*dbRoutingTx, error) {
+	sourceNode, err := graph.SourceNode()
+	if err != nil {
+		return nil, err
+	}
+
+	tx, err := graph.Database().Begin(false)
+	if err != nil {
+		return nil, err
+	}
+
+	return &dbRoutingTx{
+		graph:  graph,
+		tx:     tx,
+		source: sourceNode.PubKeyBytes,
+	}, nil
+}
+
+// close closes the underlying db transaction.
+func (g *dbRoutingTx) close() error {
+	return g.tx.Rollback()
+}
+
+// forEachNodeChannel calls the callback for every channel of the given node.
+//
+// NOTE: Part of the routingGraph interface.
+func (g *dbRoutingTx) forEachNodeChannel(nodePub route.Vertex,
+	cb func(*channeldb.ChannelEdgeInfo, *channeldb.ChannelEdgePolicy,
+		*channeldb.ChannelEdgePolicy) error) error {
+
+	txCb := func(_ *bbolt.Tx, info *channeldb.ChannelEdgeInfo,
+		p1, p2 *channeldb.ChannelEdgePolicy) error {
+
+		return cb(info, p1, p2)
+	}
+
+	return g.graph.ForEachNodeChannel(g.tx, nodePub[:], txCb)
+}
+
+// sourceNode returns the source node of the graph.
+//
+// NOTE: Part of the routingGraph interface.
+func (g *dbRoutingTx) sourceNode() route.Vertex {
+	return g.source
+}
+
+// fetchNodeFeatures returns the features of the given node. If the node is
+// unknown, assume no additional features are supported.
+//
+// NOTE: Part of the routingGraph interface.
+func (g *dbRoutingTx) fetchNodeFeatures(nodePub route.Vertex) (
+	*lnwire.FeatureVector, error) {
+
+	targetNode, err := g.graph.FetchLightningNode(g.tx, nodePub)
+	switch err {
+
+	// If the node exists and has features, return them directly.
+	case nil:
+		return targetNode.Features, nil
+
+	// If we couldn't find a node announcement, populate a blank feature
+	// vector.
+	case channeldb.ErrGraphNodeNotFound:
+		return lnwire.EmptyFeatureVector(), nil
+
+	// Otherwise bubble the error up.
+	default:
+		return nil, err
+	}
+}