lndclient: add NewBasicClient function

Author: Roasbeef

go.mod

@@ -15,5 +15,5 @@ require (
 	golang.org/x/net v0.0.0-20190313220215-9f648a60d977
 	google.golang.org/genproto v0.0.0-20190307195333-5fe7a883aa19
 	google.golang.org/grpc v1.19.0
-	gopkg.in/macaroon.v2 v2.1.0 // indirect
+	gopkg.in/macaroon.v2 v2.1.0
 )

lndclient/basic_client.go

@@ -0,0 +1,71 @@
+package lndclient
+
+import (
+	"fmt"
+	"io/ioutil"
+	"path/filepath"
+
+	"github.com/lightningnetwork/lnd/lncfg"
+	"github.com/lightningnetwork/lnd/lnrpc"
+	"github.com/lightningnetwork/lnd/macaroons"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials"
+	macaroon "gopkg.in/macaroon.v2"
+)
+
+// NewBasicClient creates a new basic gRPC client to lnd. We call this client
+// "basic" as it uses a global macaroon (by default the admin macaroon) for the
+// entire connection, and falls back to expected defaults if the arguments
+// aren't provided.
+func NewBasicClient(lndHost, tlsPath, macPath, network string) (lnrpc.LightningClient, error) {
+	if tlsPath == "" {
+		tlsPath = defaultTLSCertPath
+	}
+
+	// Load the specified TLS certificate and build transport credentials
+	creds, err := credentials.NewClientTLSFromFile(tlsPath, "")
+	if err != nil {
+		return nil, err
+	}
+
+	// Create a dial options array.
+	opts := []grpc.DialOption{
+		grpc.WithTransportCredentials(creds),
+	}
+
+	if macPath == "" {
+		macPath = filepath.Join(
+			defaultLndDir, defaultDataDir, defaultChainSubDir,
+			"bitcoin", network, defaultAdminMacaroonFilename,
+		)
+	}
+
+	// Load the specified macaroon file.
+	macBytes, err := ioutil.ReadFile(macPath)
+	if err == nil {
+		// Only if file is found
+		mac := &macaroon.Macaroon{}
+		if err = mac.UnmarshalBinary(macBytes); err != nil {
+			return nil, fmt.Errorf("unable to decode macaroon: %v",
+				err)
+		}
+
+		// Now we append the macaroon credentials to the dial options.
+		cred := macaroons.NewMacaroonCredential(mac)
+		opts = append(opts, grpc.WithPerRPCCredentials(cred))
+	}
+
+	// We need to use a custom dialer so we can also connect to unix sockets
+	// and not just TCP addresses.
+	opts = append(
+		opts, grpc.WithDialer(
+			lncfg.ClientAddressDialer(defaultRPCPort),
+		),
+	)
+	conn, err := grpc.Dial(lndHost, opts...)
+	if err != nil {
+		return nil, fmt.Errorf("unable to connect to RPC server: %v", err)
+	}
+
+	return lnrpc.NewLightningClient(conn), nil
+}