[NOD-200] Add GetSubNetwork command to JSON-RPC (#314)

* [NOD-200] Implemented the GetSubnetwork JSON-RPC command.

* [NOD-200] Fixed a copy+paste error in a comment.

btcjson/dagsvrcmds.go

@@ -498,6 +498,19 @@ func NewGetRawTransactionCmd(txHash string, verbose *int) *GetRawTransactionCmd
 	}
 }
 
+// GetSubnetworkCmd defines the getSubnetwork JSON-RPC command.
+type GetSubnetworkCmd struct {
+	SubnetworkID string
+}
+
+// NewGetSubnetworkCmd returns a new instance which can be used to issue a
+// getSubnetworkCmd command.
+func NewGetSubnetworkCmd(subnetworkID string) *GetSubnetworkCmd {
+	return &GetSubnetworkCmd{
+		SubnetworkID: subnetworkID,
+	}
+}
+
 // GetTxOutCmd defines the getTxOut JSON-RPC command.
 type GetTxOutCmd struct {
 	TxID           string
@@ -792,6 +805,7 @@ func init() {
 	MustRegisterCmd("getPeerInfo", (*GetPeerInfoCmd)(nil), flags)
 	MustRegisterCmd("getRawMempool", (*GetRawMempoolCmd)(nil), flags)
 	MustRegisterCmd("getRawTransaction", (*GetRawTransactionCmd)(nil), flags)
+	MustRegisterCmd("getSubnetwork", (*GetSubnetworkCmd)(nil), flags)
 	MustRegisterCmd("getTxOut", (*GetTxOutCmd)(nil), flags)
 	MustRegisterCmd("getTxOutProof", (*GetTxOutProofCmd)(nil), flags)
 	MustRegisterCmd("getTxOutSetInfo", (*GetTxOutSetInfoCmd)(nil), flags)

btcjson/dagsvrcmds_test.go

@@ -596,6 +596,19 @@ func TestDAGSvrCmds(t *testing.T) {
 				Verbose: btcjson.Int(1),
 			},
 		},
+		{
+			name: "getSubnetwork",
+			newCmd: func() (interface{}, error) {
+				return btcjson.NewCmd("getSubnetwork", "123")
+			},
+			staticCmd: func() interface{} {
+				return btcjson.NewGetSubnetworkCmd("123")
+			},
+			marshalled: `{"jsonrpc":"1.0","method":"getSubnetwork","params":["123"],"id":1}`,
+			unmarshalled: &btcjson.GetSubnetworkCmd{
+				SubnetworkID: "123",
+			},
+		},
 		{
 			name: "getTxOut",
 			newCmd: func() (interface{}, error) {

btcjson/dagsvrresults.go

@@ -276,6 +276,11 @@ type ScriptPubKeyResult struct {
 	Addresses []string `json:"addresses,omitempty"`
 }
 
+// GetSubnetworkResult models the data from the getSubnetwork command.
+type GetSubnetworkResult struct {
+	GasLimit uint64 `json:"gasLimit"`
+}
+
 // GetTxOutResult models the data from the gettxout command.
 type GetTxOutResult struct {
 	BestBlock     string             `json:"bestBlock"`

btcjson/jsonrpcerr.go

@@ -65,17 +65,18 @@ const (
 // server are most likely to see.  Generally, the codes should match one of the
 // more general errors above.
 const (
-	ErrRPCBlockNotFound     RPCErrorCode = -5
-	ErrRPCBlockCount        RPCErrorCode = -5
-	ErrRPCBestBlockHash     RPCErrorCode = -5
-	ErrRPCDifficulty        RPCErrorCode = -5
-	ErrRPCOutOfRange        RPCErrorCode = -1
-	ErrRPCNoTxInfo          RPCErrorCode = -5
-	ErrRPCNoCFIndex         RPCErrorCode = -5
-	ErrRPCNoNewestBlockInfo RPCErrorCode = -5
-	ErrRPCInvalidTxVout     RPCErrorCode = -5
-	ErrRPCRawTxString       RPCErrorCode = -32602
-	ErrRPCDecodeHexString   RPCErrorCode = -22
+	ErrRPCBlockNotFound      RPCErrorCode = -5
+	ErrRPCBlockCount         RPCErrorCode = -5
+	ErrRPCBestBlockHash      RPCErrorCode = -5
+	ErrRPCDifficulty         RPCErrorCode = -5
+	ErrRPCOutOfRange         RPCErrorCode = -1
+	ErrRPCNoTxInfo           RPCErrorCode = -5
+	ErrRPCNoCFIndex          RPCErrorCode = -5
+	ErrRPCNoNewestBlockInfo  RPCErrorCode = -5
+	ErrRPCInvalidTxVout      RPCErrorCode = -5
+	ErrRPCSubnetworkNotFound RPCErrorCode = -5
+	ErrRPCRawTxString        RPCErrorCode = -32602
+	ErrRPCDecodeHexString    RPCErrorCode = -22
 )
 
 // Errors that are specific to btcd.

rpcclient/dag.go

@@ -594,6 +594,41 @@ func (c *Client) EstimateFee(numBlocks int64) (float64, error) {
 	return c.EstimateFeeAsync(numBlocks).Receive()
 }
 
+// FutureGetSubnetworkResult is a future promise to deliver the result of a
+// GetSubnetworkAsync RPC invocation (or an applicable error).
+type FutureGetSubnetworkResult chan *response
+
+func (r FutureGetSubnetworkResult) Receive() (*btcjson.GetSubnetworkResult, error) {
+	res, err := receiveFuture(r)
+	if err != nil {
+		return nil, err
+	}
+
+	// Unmarshal result as a getSubnetwork result object.
+	var getSubnetworkResult *btcjson.GetSubnetworkResult
+	err = json.Unmarshal(res, &getSubnetworkResult)
+	if err != nil {
+		return nil, err
+	}
+
+	return getSubnetworkResult, nil
+}
+
+// GetSubnetworkAsync returns an instance of a type that can be used to get the result
+// of the RPC at some future time by invoking the Receive function on the
+// returned instance.
+//
+// See GetSubnetwork for the blocking version and more details.
+func (c *Client) GetSubnetworkAsync(subnetworkID string) FutureGetSubnetworkResult {
+	cmd := btcjson.NewGetSubnetworkCmd(subnetworkID)
+	return c.sendCmd(cmd)
+}
+
+// GetSubnetwork provides information about a subnetwork given its ID.
+func (c *Client) GetSubnetwork(subnetworkID string) (*btcjson.GetSubnetworkResult, error) {
+	return c.GetSubnetworkAsync(subnetworkID).Receive()
+}
+
 // FutureGetTxOutResult is a future promise to deliver the result of a
 // GetTxOutAsync RPC invocation (or an applicable error).
 type FutureGetTxOutResult chan *response

server/rpc/rpcserver.go

@@ -171,6 +171,7 @@ var rpcHandlersBeforeInit = map[string]commandHandler{
 	"getPeerInfo":           handleGetPeerInfo,
 	"getRawMempool":         handleGetRawMempool,
 	"getRawTransaction":     handleGetRawTransaction,
+	"getSubnetwork":         handleGetSubnetwork,
 	"getTxOut":              handleGetTxOut,
 	"help":                  handleHelp,
 	"node":                  handleNode,
@@ -2665,6 +2666,29 @@ func handleGetRawTransaction(s *Server, cmd interface{}, closeChan <-chan struct
 	return *rawTxn, nil
 }
 
+// handleGetSubnetwork handles the getSubnetwork command.
+func handleGetSubnetwork(s *Server, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
+	c := cmd.(*btcjson.GetSubnetworkCmd)
+
+	subnetworkID, err := subnetworkid.NewFromStr(c.SubnetworkID)
+	if err != nil {
+		return nil, rpcDecodeHexError(c.SubnetworkID)
+	}
+
+	gasLimit, err := s.cfg.DAG.SubnetworkStore.GasLimit(subnetworkID)
+	if err != nil {
+		return nil, &btcjson.RPCError{
+			Code:    btcjson.ErrRPCSubnetworkNotFound,
+			Message: "Subnetwork not found.",
+		}
+	}
+
+	subnetworkReply := &btcjson.GetSubnetworkResult{
+		GasLimit: gasLimit,
+	}
+	return subnetworkReply, nil
+}
+
 // handleGetTxOut handles getTxOut commands.
 func handleGetTxOut(s *Server, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
 	c := cmd.(*btcjson.GetTxOutCmd)

server/rpc/rpcserverhelp.go

@@ -507,6 +507,13 @@ var helpDescsEnUS = map[string]string{
 	"getRawTransaction--condition1": "verbose=true",
 	"getRawTransaction--result0":    "Hex-encoded bytes of the serialized transaction",
 
+	// GetSubnetworkCmd help.
+	"getSubnetwork--synopsis":    "Returns information about a subnetwork given its ID.",
+	"getSubnetwork-subnetworkId": "The ID of the subnetwork",
+
+	// GetSubnetworkResult help.
+	"getSubnetworkResult-gasLimit": "The gas limit of the subnetwork",
+
 	// GetTxOutResult help.
 	"getTxOutResult-bestBlock":     "The block hash that contains the transaction output",
 	"getTxOutResult-confirmations": "The number of confirmations (Will be 'null' if txindex is not disabled)",
@@ -698,6 +705,7 @@ var rpcResultTypes = map[string][]interface{}{
 	"getPeerInfo":           {(*[]btcjson.GetPeerInfoResult)(nil)},
 	"getRawMempool":         {(*[]string)(nil), (*btcjson.GetRawMempoolVerboseResult)(nil)},
 	"getRawTransaction":     {(*string)(nil), (*btcjson.TxRawResult)(nil)},
+	"getSubnetwork":         {(*btcjson.GetSubnetworkResult)(nil)},
 	"getTxOut":              {(*btcjson.GetTxOutResult)(nil)},
 	"node":                  nil,
 	"help":                  {(*string)(nil), (*string)(nil)},