rfq: make SellOrder.Peer field an Option type

Currently, the `SellOrder.Peer` field must be specified, but in the
future, the negotiator should be able to select the optimal peer
automatically. This commit updates the interface to support this future
functionality by making `SellOrder.Peer` an Option type. Note that this
field was already a pointer.

Author: ffranr

rfq/manager.go

@@ -763,7 +763,7 @@ type SellOrder struct {
 
 	// Peer is the peer that the buy order is intended for. This field is
 	// optional.
-	Peer *route.Vertex
+	Peer fn.Option[route.Vertex]
 }
 
 // UpsertAssetSellOrder upserts an asset sell order for management.
@@ -772,7 +772,7 @@ func (m *Manager) UpsertAssetSellOrder(order SellOrder) error {
 	//
 	// TODO(ffranr): Add support for peerless sell orders. The negotiator
 	//  should be able to determine the optimal peer.
-	if order.Peer == nil {
+	if order.Peer.IsNone() {
 		return fmt.Errorf("sell order peer must be specified")
 	}
 

rfq/negotiator.go

@@ -467,6 +467,15 @@ func (n *Negotiator) HandleOutgoingSellOrder(order SellOrder) {
 	go func() {
 		defer n.Wg.Done()
 
+		// Unwrap the peer from the order. For now, we can assume that
+		// the peer is always specified.
+		peer, err := order.Peer.UnwrapOrErr(
+			fmt.Errorf("buy order peer must be specified"),
+		)
+		if err != nil {
+			n.cfg.ErrChan <- err
+		}
+
 		// We calculate a proposed ask price for our peer's
 		// consideration. If a price oracle is not specified we will
 		// skip this step.
@@ -475,7 +484,7 @@ func (n *Negotiator) HandleOutgoingSellOrder(order SellOrder) {
 		if n.cfg.PriceOracle != nil && order.AssetSpecifier.IsSome() {
 			// Query the price oracle for an asking price.
 			assetRate, err := n.queryAskFromPriceOracle(
-				order.Peer, order.AssetSpecifier,
+				&peer, order.AssetSpecifier,
 				fn.None[uint64](),
 				fn.Some(order.PaymentMaxAmt),
 				fn.None[rfqmsg.AssetRate](),
@@ -491,7 +500,7 @@ func (n *Negotiator) HandleOutgoingSellOrder(order SellOrder) {
 		}
 
 		request, err := rfqmsg.NewSellRequest(
-			*order.Peer, order.AssetSpecifier, order.PaymentMaxAmt,
+			peer, order.AssetSpecifier, order.PaymentMaxAmt,
 			assetRateHint,
 		)
 		if err != nil {

rpcserver.go

@@ -6403,15 +6403,15 @@ func unmarshalAssetSellOrder(
 	}
 
 	// Unmarshal the peer if specified.
-	var peer *route.Vertex
+	var peer fn.Option[route.Vertex]
 	if len(req.PeerPubKey) > 0 {
 		pv, err := route.NewVertexFromBytes(req.PeerPubKey)
 		if err != nil {
 			return nil, fmt.Errorf("error unmarshalling peer "+
 				"route vertex: %w", err)
 		}
 
-		peer = &pv
+		peer = fn.Some(pv)
 	}
 
 	// Construct an asset specifier from the asset ID and/or group key.
@@ -6447,12 +6447,13 @@ func (r *rpcServer) AddAssetSellOrder(_ context.Context,
 			err)
 	}
 
-	var peer string
-	if sellOrder.Peer != nil {
-		peer = sellOrder.Peer.String()
-	}
+	// Extract peer identifier as a string for logging.
+	peerStr := fn.MapOptionZ(sellOrder.Peer, func(p route.Vertex) string {
+		return p.String()
+	})
+
 	rpcsLog.Debugf("[AddAssetSellOrder]: upserting sell order "+
-		"(dest_peer=%s)", peer)
+		"(dest_peer=%s)", peerStr)
 
 	// Register an event listener before actually inserting the order, so we
 	// definitely don't miss any responses.
@@ -6494,7 +6495,7 @@ func (r *rpcServer) AddAssetSellOrder(_ context.Context,
 
 		case <-timeout:
 			return nil, fmt.Errorf("timeout waiting for response "+
-				"from peer %x", sellOrder.Peer[:])
+				"from peer %s", peerStr)
 		}
 	}
 }