lnrpc/chainrpc: add ChainNotifier subserver registration driver

lnrpc/chainrpc/driver.go

@@ -0,0 +1,71 @@
+// +build chainrpc
+
+package chainrpc
+
+import (
+	"fmt"
+
+	"github.com/lightningnetwork/lnd/lnrpc"
+)
+
+// createNewSubServer is a helper method that will create the new chain notifier
+// sub server given the main config dispatcher method. If we're unable to find
+// the config that is meant for us in the config dispatcher, then we'll exit
+// with an error.
+func createNewSubServer(configRegistry lnrpc.SubServerConfigDispatcher) (
+	lnrpc.SubServer, lnrpc.MacaroonPerms, error) {
+
+	// We'll attempt to look up the config that we expect, according to our
+	// subServerName name. If we can't find this, then we'll exit with an
+	// error, as we're unable to properly initialize ourselves without this
+	// config.
+	chainNotifierServerConf, ok := configRegistry.FetchConfig(subServerName)
+	if !ok {
+		return nil, nil, fmt.Errorf("unable to find config for "+
+			"subserver type %s", subServerName)
+	}
+
+	// Now that we've found an object mapping to our service name, we'll
+	// ensure that it's the type we need.
+	config, ok := chainNotifierServerConf.(*Config)
+	if !ok {
+		return nil, nil, fmt.Errorf("wrong type of config for "+
+			"subserver %s, expected %T got %T", subServerName,
+			&Config{}, chainNotifierServerConf)
+	}
+
+	// Before we try to make the new chain notifier service instance, we'll
+	// perform some sanity checks on the arguments to ensure that they're
+	// usable.
+	switch {
+	// If the macaroon service is set (we should use macaroons), then
+	// ensure that we know where to look for them, or create them if not
+	// found.
+	case config.MacService != nil && config.NetworkDir == "":
+		return nil, nil, fmt.Errorf("NetworkDir must be set to create " +
+			"chainrpc")
+	case config.ChainNotifier == nil:
+		return nil, nil, fmt.Errorf("ChainNotifier must be set to " +
+			"create chainrpc")
+	}
+
+	return New(config)
+}
+
+func init() {
+	subServer := &lnrpc.SubServerDriver{
+		SubServerName: subServerName,
+		New: func(c lnrpc.SubServerConfigDispatcher) (
+			lnrpc.SubServer, lnrpc.MacaroonPerms, error) {
+
+			return createNewSubServer(c)
+		},
+	}
+
+	// If the build tag is active, then we'll register ourselves as a
+	// sub-RPC server within the global lnrpc package namespace.
+	if err := lnrpc.RegisterSubServer(subServer); err != nil {
+		panic(fmt.Sprintf("failed to register subserver driver %s: %v",
+			subServerName, err))
+	}
+}