wtclient+lnrpc: move LookupTower to Manager

watchtower/wtclient/manager.go

@@ -43,6 +43,10 @@ type TowerClientManager interface {
 	// type.
 	RegisteredTowers(opts ...wtdb.ClientSessionListOption) (
 		map[blob.Type][]*RegisteredTower, error)
+
+	// LookupTower retrieves a registered watchtower through its public key.
+	LookupTower(*btcec.PublicKey, ...wtdb.ClientSessionListOption) (
+		map[blob.Type]*RegisteredTower, error)
 }
 
 // Config provides the TowerClient with access to the resources it requires to
@@ -354,3 +358,29 @@ func (m *Manager) RegisteredTowers(opts ...wtdb.ClientSessionListOption) (
 
 	return resp, nil
 }
+
+// LookupTower retrieves a registered watchtower through its public key.
+func (m *Manager) LookupTower(key *btcec.PublicKey,
+	opts ...wtdb.ClientSessionListOption) (map[blob.Type]*RegisteredTower,
+	error) {
+
+	tower, err := m.cfg.DB.LoadTower(key)
+	if err != nil {
+		return nil, err
+	}
+
+	m.clientsMu.Lock()
+	defer m.clientsMu.Unlock()
+
+	resp := make(map[blob.Type]*RegisteredTower)
+	for _, client := range m.clients {
+		tower, err := client.lookupTower(tower, opts...)
+		if err != nil {
+			return nil, err
+		}
+
+		resp[client.Policy().BlobType] = tower
+	}
+
+	return resp, nil
+}