cli: unify RPC endpoint flags under options package

This makes rpc flags consistent across all commands, previously some commands
used 'endpoint, e' and some 'rpc, r', some had ability to change timeout and
some hadn't. Now 'rpc-endpoint, r' is used everywhere along with 'timeout, t'.

cli/options/options.go

@@ -4,10 +4,22 @@ Package options contains a set of common CLI options and helper functions to use
 package options
 
 import (
+	"context"
+	"errors"
+	"time"
+
 	"github.com/nspcc-dev/neo-go/pkg/config/netmode"
+	"github.com/nspcc-dev/neo-go/pkg/rpc/client"
 	"github.com/urfave/cli"
 )
 
+// DefaultTimeout is the default timeout used for RPC requests.
+const DefaultTimeout = 10 * time.Second
+
+// RPCEndpointFlag is a long flag name for RPC endpoint. It can be used to
+// check for flag presence in the context.
+const RPCEndpointFlag = "rpc-endpoint"
+
 // Network is a set of flags for choosing the network to operate on
 // (privnet/mainnet/testnet).
 var Network = []cli.Flag{
@@ -16,6 +28,20 @@ var Network = []cli.Flag{
 	cli.BoolFlag{Name: "testnet, t"},
 }
 
+// RPC is a set of flags used for RPC connections (endpoint and timeout).
+var RPC = []cli.Flag{
+	cli.StringFlag{
+		Name:  RPCEndpointFlag + ", r",
+		Usage: "RPC node address",
+	},
+	cli.DurationFlag{
+		Name:  "timeout, t",
+		Usage: "Timeout for the operation (10 seconds by default)",
+	},
+}
+
+var errNoEndpoint = errors.New("no RPC endpoint specified, use option '--" + RPCEndpointFlag + "' or '-r'")
+
 // GetNetwork examines Context's flags and returns the appropriate network. It
 // defaults to PrivNet if no flags are given.
 func GetNetwork(ctx *cli.Context) netmode.Magic {
@@ -28,3 +54,25 @@ func GetNetwork(ctx *cli.Context) netmode.Magic {
 	}
 	return net
 }
+
+// GetTimeoutContext returns a context.Context with default of user-set timeout.
+func GetTimeoutContext(ctx *cli.Context) (context.Context, func()) {
+	dur := ctx.Duration("timeout")
+	if dur == 0 {
+		dur = DefaultTimeout
+	}
+	return context.WithTimeout(context.Background(), dur)
+}
+
+// GetRPCClient returns an RPC client instance for the given Context.
+func GetRPCClient(gctx context.Context, ctx *cli.Context) (*client.Client, cli.ExitCoder) {
+	endpoint := ctx.String(RPCEndpointFlag)
+	if len(endpoint) == 0 {
+		return nil, cli.NewExitError(errNoEndpoint, 1)
+	}
+	c, err := client.New(gctx, endpoint, client.Options{})
+	if err != nil {
+		return nil, cli.NewExitError(err, 1)
+	}
+	return c, nil
+}