Implement gettxout rpc.

Use new error type defined in Roasbeef/btcjson@4dc9db809

rpcserver.go

@@ -144,7 +144,7 @@ var rpcHandlersBeforeInit = map[string]commandHandler{
 	"getpeerinfo":          handleGetPeerInfo,
 	"getrawmempool":        handleGetRawMempool,
 	"getrawtransaction":    handleGetRawTransaction,
-	"gettxout":             handleUnimplemented,
+	"gettxout":             handleGetTxOut,
 	"getwork":              handleGetWork,
 	"help":                 handleHelp,
 	"ping":                 handlePing,
@@ -2434,6 +2434,97 @@ func reverseUint32Array(b []byte) {
 	}
 }
 
+// handleGetTxOut handles gettxout commands.
+func handleGetTxOut(s *rpcServer, cmd btcjson.Cmd, closeChan <-chan struct{}) (interface{}, error) {
+	c := cmd.(*btcjson.GetTxOutCmd)
+
+	// Convert the provided transaction hash hex to a ShaHash.
+	txSha, err := btcwire.NewShaHashFromStr(c.Txid)
+	if err != nil {
+		return nil, btcjson.Error{
+			Code: btcjson.ErrInvalidParameter.Code,
+			Message: fmt.Sprintf("argument must be hexadecimal "+
+				"string (not %q)", c.Txid),
+		}
+	}
+
+	// If requested and the tx is available in the mempool try to fetch it from
+	// there, otherwise attempt to fetch from the block database.
+	var mtx *btcwire.MsgTx
+	var bestBlockSha string
+	var confirmations int64
+	if c.IncludeMempool && s.server.txMemPool.HaveTransaction(txSha) {
+		tx, err := s.server.txMemPool.FetchTransaction(txSha)
+		if err != nil {
+			rpcsLog.Errorf("Error fetching tx: %v", err)
+			return nil, btcjson.ErrNoTxInfo
+		}
+		mtx = tx.MsgTx()
+		confirmations = 0
+		bestBlockSha = ""
+	} else {
+		txList, err := s.server.db.FetchTxBySha(txSha)
+		if err != nil || len(txList) == 0 {
+			return nil, btcjson.ErrNoTxInfo
+		}
+
+		lastTx := len(txList) - 1
+		mtx = txList[lastTx].Tx
+		blksha := txList[lastTx].BlkSha
+		txHeight := txList[lastTx].Height
+
+		_, bestHeight, err := s.server.db.NewestSha()
+		if err != nil {
+			rpcsLog.Errorf("Cannot get newest sha: %v", err)
+			return nil, btcjson.ErrBlockNotFound
+		}
+
+		confirmations = 1 + bestHeight - txHeight
+		bestBlockSha = blksha.String()
+	}
+
+	if c.Output < 0 || c.Output > len(mtx.TxOut)-1 {
+		return nil, btcjson.ErrInvalidTxVout
+	}
+
+	if mtx.TxOut[c.Output] == nil {
+		rpcsLog.Errorf("Output index: %d, for txid: %s does not exist.", c.Output, c.Txid)
+		return nil, btcjson.ErrInternal
+	}
+
+	// Disassemble script into single line printable format.
+	// The disassembled string will contain [error] inline if the script
+	// doesn't fully parse, so ignore the error here.
+	script := mtx.TxOut[c.Output].PkScript
+	disbuf, _ := btcscript.DisasmString(script)
+
+	// Get further info about the script.
+	// Ignore the error here since an error means the script couldn't parse
+	// and there is no additional information about it anyways.
+	net := s.server.netParams
+	scriptClass, addrs, reqSigs, _ := btcscript.ExtractPkScriptAddrs(script, net)
+	addresses := make([]string, len(addrs))
+	for i, addr := range addrs {
+		addresses[i] = addr.EncodeAddress()
+	}
+
+	txOutReply := &btcjson.GetTxOutResult{
+		BestBlock:     bestBlockSha,
+		Confirmations: confirmations,
+		Value:         btcutil.Amount(mtx.TxOut[c.Output].Value).ToUnit(btcutil.AmountBTC),
+		Version:       mtx.Version,
+		ScriptPubKey: btcjson.ScriptPubKeyResult{
+			Asm:       disbuf,
+			Hex:       hex.EncodeToString(script),
+			ReqSigs:   int32(reqSigs),
+			Type:      scriptClass.String(),
+			Addresses: addresses,
+		},
+		Coinbase: btcchain.IsCoinBase(btcutil.NewTx(mtx)),
+	}
+	return txOutReply, nil
+}
+
 // handleGetWorkRequest is a helper for handleGetWork which deals with
 // generating and returning work to the caller.
 //