btcd/rpcserver.go

// Copyright (c) 2013-2017 The btcsuite developers
// Copyright (c) 2015-2017 The Decred developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.

package main

import (
	"bytes"
	"crypto/sha256"
	"crypto/subtle"
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"math/big"
	"math/rand"
	"net"
	"net/http"
	"os"
	"strconv"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	"github.com/btcsuite/btcd/blockchain"
	"github.com/btcsuite/btcd/blockchain/indexers"
	"github.com/btcsuite/btcd/btcec"
	"github.com/btcsuite/btcd/btcjson"
	"github.com/btcsuite/btcd/chaincfg"
	"github.com/btcsuite/btcd/chaincfg/chainhash"
	"github.com/btcsuite/btcd/database"
	"github.com/btcsuite/btcd/mempool"
	"github.com/btcsuite/btcd/mining"
	"github.com/btcsuite/btcd/mining/cpuminer"
	"github.com/btcsuite/btcd/peer"
	"github.com/btcsuite/btcd/txscript"
	"github.com/btcsuite/btcd/wire"
	"github.com/btcsuite/btcutil"
	"github.com/btcsuite/websocket"
)

// API version constants
const (
	jsonrpcSemverString = "1.3.0"
	jsonrpcSemverMajor  = 1
	jsonrpcSemverMinor  = 3
	jsonrpcSemverPatch  = 0
)

const (
	// rpcAuthTimeoutSeconds is the number of seconds a connection to the
	// RPC server is allowed to stay open without authenticating before it
	// is closed.
	rpcAuthTimeoutSeconds = 10

	// uint256Size is the number of bytes needed to represent an unsigned
	// 256-bit integer.
	uint256Size = 32

	// gbtNonceRange is two 32-bit big-endian hexadecimal integers which
	// represent the valid ranges of nonces returned by the getblocktemplate
	// RPC.
	gbtNonceRange = "00000000ffffffff"

	// gbtRegenerateSeconds is the number of seconds that must pass before
	// a new template is generated when the previous block hash has not
	// changed and there have been changes to the available transactions
	// in the memory pool.
	gbtRegenerateSeconds = 60

	// maxProtocolVersion is the max protocol version the server supports.
	maxProtocolVersion = 70002
)

var (
	// gbtMutableFields are the manipulations the server allows to be made
	// to block templates generated by the getblocktemplate RPC.  It is
	// declared here to avoid the overhead of creating the slice on every
	// invocation for constant data.
	gbtMutableFields = []string{
		"time", "transactions/add", "prevblock", "coinbase/append",
	}

	// gbtCoinbaseAux describes additional data that miners should include
	// in the coinbase signature script.  It is declared here to avoid the
	// overhead of creating a new object on every invocation for constant
	// data.
	gbtCoinbaseAux = &btcjson.GetBlockTemplateResultAux{
		Flags: hex.EncodeToString(builderScript(txscript.
			NewScriptBuilder().
			AddData([]byte(mining.CoinbaseFlags)))),
	}

	// gbtCapabilities describes additional capabilities returned with a
	// block template generated by the getblocktemplate RPC.    It is
	// declared here to avoid the overhead of creating the slice on every
	// invocation for constant data.
	gbtCapabilities = []string{"proposal"}
)

// Errors
var (
	// ErrRPCUnimplemented is an error returned to RPC clients when the
	// provided command is recognized, but not implemented.
	ErrRPCUnimplemented = &btcjson.RPCError{
		Code:    btcjson.ErrRPCUnimplemented,
		Message: "Command unimplemented",
	}

	// ErrRPCNoWallet is an error returned to RPC clients when the provided
	// command is recognized as a wallet command.
	ErrRPCNoWallet = &btcjson.RPCError{
		Code:    btcjson.ErrRPCNoWallet,
		Message: "This implementation does not implement wallet commands",
	}
)

type commandHandler func(*rpcServer, interface{}, <-chan struct{}) (interface{}, error)

// rpcHandlers maps RPC command strings to appropriate handler functions.
// This is set by init because help references rpcHandlers and thus causes
// a dependency loop.
var rpcHandlers map[string]commandHandler
var rpcHandlersBeforeInit = map[string]commandHandler{
	"addnode":               handleAddNode,
	"createrawtransaction":  handleCreateRawTransaction,
	"debuglevel":            handleDebugLevel,
	"decoderawtransaction":  handleDecodeRawTransaction,
	"decodescript":          handleDecodeScript,
	"estimatefee":           handleEstimateFee,
	"generate":              handleGenerate,
	"getaddednodeinfo":      handleGetAddedNodeInfo,
	"getbestblock":          handleGetBestBlock,
	"getbestblockhash":      handleGetBestBlockHash,
	"getblock":              handleGetBlock,
	"getblockchaininfo":     handleGetBlockChainInfo,
	"getblockcount":         handleGetBlockCount,
	"getblockhash":          handleGetBlockHash,
	"getblockheader":        handleGetBlockHeader,
	"getblocktemplate":      handleGetBlockTemplate,
	"getcfilter":            handleGetCFilter,
	"getcfilterheader":      handleGetCFilterHeader,
	"getconnectioncount":    handleGetConnectionCount,
	"getcurrentnet":         handleGetCurrentNet,
	"getdifficulty":         handleGetDifficulty,
	"getgenerate":           handleGetGenerate,
	"gethashespersec":       handleGetHashesPerSec,
	"getheaders":            handleGetHeaders,
	"getinfo":               handleGetInfo,
	"getmempoolinfo":        handleGetMempoolInfo,
	"getmininginfo":         handleGetMiningInfo,
	"getnettotals":          handleGetNetTotals,
	"getnetworkhashps":      handleGetNetworkHashPS,
	"getpeerinfo":           handleGetPeerInfo,
	"getrawmempool":         handleGetRawMempool,
	"getrawtransaction":     handleGetRawTransaction,
	"gettxout":              handleGetTxOut,
	"help":                  handleHelp,
	"node":                  handleNode,
	"ping":                  handlePing,
	"searchrawtransactions": handleSearchRawTransactions,
	"sendrawtransaction":    handleSendRawTransaction,
	"setgenerate":           handleSetGenerate,
	"stop":                  handleStop,
	"submitblock":           handleSubmitBlock,
	"uptime":                handleUptime,
	"validateaddress":       handleValidateAddress,
	"verifychain":           handleVerifyChain,
	"verifymessage":         handleVerifyMessage,
	"version":               handleVersion,
}

// list of commands that we recognize, but for which btcd has no support because
// it lacks support for wallet functionality. For these commands the user
// should ask a connected instance of btcwallet.
var rpcAskWallet = map[string]struct{}{
	"addmultisigaddress":     {},
	"backupwallet":           {},
	"createencryptedwallet":  {},
	"createmultisig":         {},
	"dumpprivkey":            {},
	"dumpwallet":             {},
	"encryptwallet":          {},
	"getaccount":             {},
	"getaccountaddress":      {},
	"getaddressesbyaccount":  {},
	"getbalance":             {},
	"getnewaddress":          {},
	"getrawchangeaddress":    {},
	"getreceivedbyaccount":   {},
	"getreceivedbyaddress":   {},
	"gettransaction":         {},
	"gettxoutsetinfo":        {},
	"getunconfirmedbalance":  {},
	"getwalletinfo":          {},
	"importprivkey":          {},
	"importwallet":           {},
	"keypoolrefill":          {},
	"listaccounts":           {},
	"listaddressgroupings":   {},
	"listlockunspent":        {},
	"listreceivedbyaccount":  {},
	"listreceivedbyaddress":  {},
	"listsinceblock":         {},
	"listtransactions":       {},
	"listunspent":            {},
	"lockunspent":            {},
	"move":                   {},
	"sendfrom":               {},
	"sendmany":               {},
	"sendtoaddress":          {},
	"setaccount":             {},
	"settxfee":               {},
	"signmessage":            {},
	"signrawtransaction":     {},
	"walletlock":             {},
	"walletpassphrase":       {},
	"walletpassphrasechange": {},
}

// Commands that are currently unimplemented, but should ultimately be.
var rpcUnimplemented = map[string]struct{}{
	"estimatepriority": {},
	"getchaintips":     {},
	"getmempoolentry":  {},
	"getnetworkinfo":   {},
	"getwork":          {},
	"invalidateblock":  {},
	"preciousblock":    {},
	"reconsiderblock":  {},
}

// Commands that are available to a limited user
var rpcLimited = map[string]struct{}{
	// Websockets commands
	"loadtxfilter":          {},
	"notifyblocks":          {},
	"notifynewtransactions": {},
	"notifyreceived":        {},
	"notifyspent":           {},
	"rescan":                {},
	"rescanblocks":          {},
	"session":               {},

	// Websockets AND HTTP/S commands
	"help": {},

	// HTTP/S-only commands
	"createrawtransaction":  {},
	"decoderawtransaction":  {},
	"decodescript":          {},
	"estimatefee":           {},
	"getbestblock":          {},
	"getbestblockhash":      {},
	"getblock":              {},
	"getblockcount":         {},
	"getblockhash":          {},
	"getblockheader":        {},
	"getcfilter":            {},
	"getcfilterheader":      {},
	"getcurrentnet":         {},
	"getdifficulty":         {},
	"getheaders":            {},
	"getinfo":               {},
	"getnettotals":          {},
	"getnetworkhashps":      {},
	"getrawmempool":         {},
	"getrawtransaction":     {},
	"gettxout":              {},
	"searchrawtransactions": {},
	"sendrawtransaction":    {},
	"submitblock":           {},
	"uptime":                {},
	"validateaddress":       {},
	"verifymessage":         {},
	"version":               {},
}

// builderScript is a convenience function which is used for hard-coded scripts
// built with the script builder.   Any errors are converted to a panic since it
// is only, and must only, be used with hard-coded, and therefore, known good,
// scripts.
func builderScript(builder *txscript.ScriptBuilder) []byte {
	script, err := builder.Script()
	if err != nil {
		panic(err)
	}
	return script
}

// internalRPCError is a convenience function to convert an internal error to
// an RPC error with the appropriate code set.  It also logs the error to the
// RPC server subsystem since internal errors really should not occur.  The
// context parameter is only used in the log message and may be empty if it's
// not needed.
func internalRPCError(errStr, context string) *btcjson.RPCError {
	logStr := errStr
	if context != "" {
		logStr = context + ": " + errStr
	}
	rpcsLog.Error(logStr)
	return btcjson.NewRPCError(btcjson.ErrRPCInternal.Code, errStr)
}

// rpcDecodeHexError is a convenience function for returning a nicely formatted
// RPC error which indicates the provided hex string failed to decode.
func rpcDecodeHexError(gotHex string) *btcjson.RPCError {
	return btcjson.NewRPCError(btcjson.ErrRPCDecodeHexString,
		fmt.Sprintf("Argument must be hexadecimal string (not %q)",
			gotHex))
}

// rpcNoTxInfoError is a convenience function for returning a nicely formatted
// RPC error which indicates there is no information available for the provided
// transaction hash.
func rpcNoTxInfoError(txHash *chainhash.Hash) *btcjson.RPCError {
	return btcjson.NewRPCError(btcjson.ErrRPCNoTxInfo,
		fmt.Sprintf("No information available about transaction %v",
			txHash))
}

// gbtWorkState houses state that is used in between multiple RPC invocations to
// getblocktemplate.
type gbtWorkState struct {
	sync.Mutex
	lastTxUpdate  time.Time
	lastGenerated time.Time
	prevHash      *chainhash.Hash
	minTimestamp  time.Time
	template      *mining.BlockTemplate
	notifyMap     map[chainhash.Hash]map[int64]chan struct{}
	timeSource    blockchain.MedianTimeSource
}

// newGbtWorkState returns a new instance of a gbtWorkState with all internal
// fields initialized and ready to use.
func newGbtWorkState(timeSource blockchain.MedianTimeSource) *gbtWorkState {
	return &gbtWorkState{
		notifyMap:  make(map[chainhash.Hash]map[int64]chan struct{}),
		timeSource: timeSource,
	}
}

// handleUnimplemented is the handler for commands that should ultimately be
// supported but are not yet implemented.
func handleUnimplemented(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	return nil, ErrRPCUnimplemented
}

// handleAskWallet is the handler for commands that are recognized as valid, but
// are unable to answer correctly since it involves wallet state.
// These commands will be implemented in btcwallet.
func handleAskWallet(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	return nil, ErrRPCNoWallet
}

// handleAddNode handles addnode commands.
func handleAddNode(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.AddNodeCmd)

	addr := normalizeAddress(c.Addr, s.cfg.ChainParams.DefaultPort)
	var err error
	switch c.SubCmd {
	case "add":
		err = s.cfg.ConnMgr.Connect(addr, true)
	case "remove":
		err = s.cfg.ConnMgr.RemoveByAddr(addr)
	case "onetry":
		err = s.cfg.ConnMgr.Connect(addr, false)
	default:
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCInvalidParameter,
			Message: "invalid subcommand for addnode",
		}
	}

	if err != nil {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCInvalidParameter,
			Message: err.Error(),
		}
	}

	// no data returned unless an error.
	return nil, nil
}

// handleNode handles node commands.
func handleNode(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.NodeCmd)

	var addr string
	var nodeID uint64
	var errN, err error
	params := s.cfg.ChainParams
	switch c.SubCmd {
	case "disconnect":
		// If we have a valid uint disconnect by node id. Otherwise,
		// attempt to disconnect by address, returning an error if a
		// valid IP address is not supplied.
		if nodeID, errN = strconv.ParseUint(c.Target, 10, 32); errN == nil {
			err = s.cfg.ConnMgr.DisconnectByID(int32(nodeID))
		} else {
			if _, _, errP := net.SplitHostPort(c.Target); errP == nil || net.ParseIP(c.Target) != nil {
				addr = normalizeAddress(c.Target, params.DefaultPort)
				err = s.cfg.ConnMgr.DisconnectByAddr(addr)
			} else {
				return nil, &btcjson.RPCError{
					Code:    btcjson.ErrRPCInvalidParameter,
					Message: "invalid address or node ID",
				}
			}
		}
		if err != nil && peerExists(s.cfg.ConnMgr, addr, int32(nodeID)) {

			return nil, &btcjson.RPCError{
				Code:    btcjson.ErrRPCMisc,
				Message: "can't disconnect a permanent peer, use remove",
			}
		}

	case "remove":
		// If we have a valid uint disconnect by node id. Otherwise,
		// attempt to disconnect by address, returning an error if a
		// valid IP address is not supplied.
		if nodeID, errN = strconv.ParseUint(c.Target, 10, 32); errN == nil {
			err = s.cfg.ConnMgr.RemoveByID(int32(nodeID))
		} else {
			if _, _, errP := net.SplitHostPort(c.Target); errP == nil || net.ParseIP(c.Target) != nil {
				addr = normalizeAddress(c.Target, params.DefaultPort)
				err = s.cfg.ConnMgr.RemoveByAddr(addr)
			} else {
				return nil, &btcjson.RPCError{
					Code:    btcjson.ErrRPCInvalidParameter,
					Message: "invalid address or node ID",
				}
			}
		}
		if err != nil && peerExists(s.cfg.ConnMgr, addr, int32(nodeID)) {
			return nil, &btcjson.RPCError{
				Code:    btcjson.ErrRPCMisc,
				Message: "can't remove a temporary peer, use disconnect",
			}
		}

	case "connect":
		addr = normalizeAddress(c.Target, params.DefaultPort)

		// Default to temporary connections.
		subCmd := "temp"
		if c.ConnectSubCmd != nil {
			subCmd = *c.ConnectSubCmd
		}

		switch subCmd {
		case "perm", "temp":
			err = s.cfg.ConnMgr.Connect(addr, subCmd == "perm")
		default:
			return nil, &btcjson.RPCError{
				Code:    btcjson.ErrRPCInvalidParameter,
				Message: "invalid subcommand for node connect",
			}
		}
	default:
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCInvalidParameter,
			Message: "invalid subcommand for node",
		}
	}

	if err != nil {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCInvalidParameter,
			Message: err.Error(),
		}
	}

	// no data returned unless an error.
	return nil, nil
}

// peerExists determines if a certain peer is currently connected given
// information about all currently connected peers. Peer existence is
// determined using either a target address or node id.
func peerExists(connMgr rpcserverConnManager, addr string, nodeID int32) bool {
	for _, p := range connMgr.ConnectedPeers() {
		if p.ToPeer().ID() == nodeID || p.ToPeer().Addr() == addr {
			return true
		}
	}
	return false
}

// messageToHex serializes a message to the wire protocol encoding using the
// latest protocol version and returns a hex-encoded string of the result.
func messageToHex(msg wire.Message) (string, error) {
	var buf bytes.Buffer
	if err := msg.BtcEncode(&buf, maxProtocolVersion, wire.WitnessEncoding); err != nil {
		context := fmt.Sprintf("Failed to encode msg of type %T", msg)
		return "", internalRPCError(err.Error(), context)
	}

	return hex.EncodeToString(buf.Bytes()), nil
}

// handleCreateRawTransaction handles createrawtransaction commands.
func handleCreateRawTransaction(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.CreateRawTransactionCmd)

	// Validate the locktime, if given.
	if c.LockTime != nil &&
		(*c.LockTime < 0 || *c.LockTime > int64(wire.MaxTxInSequenceNum)) {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCInvalidParameter,
			Message: "Locktime out of range",
		}
	}

	// Add all transaction inputs to a new transaction after performing
	// some validity checks.
	mtx := wire.NewMsgTx(wire.TxVersion)
	for _, input := range c.Inputs {
		txHash, err := chainhash.NewHashFromStr(input.Txid)
		if err != nil {
			return nil, rpcDecodeHexError(input.Txid)
		}

		prevOut := wire.NewOutPoint(txHash, input.Vout)
		txIn := wire.NewTxIn(prevOut, []byte{}, nil)
		if c.LockTime != nil && *c.LockTime != 0 {
			txIn.Sequence = wire.MaxTxInSequenceNum - 1
		}
		mtx.AddTxIn(txIn)
	}

	// Add all transaction outputs to the transaction after performing
	// some validity checks.
	params := s.cfg.ChainParams
	for encodedAddr, amount := range c.Amounts {
		// Ensure amount is in the valid range for monetary amounts.
		if amount <= 0 || amount > btcutil.MaxSatoshi {
			return nil, &btcjson.RPCError{
				Code:    btcjson.ErrRPCType,
				Message: "Invalid amount",
			}
		}

		// Decode the provided address.
		addr, err := btcutil.DecodeAddress(encodedAddr, params)
		if err != nil {
			return nil, &btcjson.RPCError{
				Code:    btcjson.ErrRPCInvalidAddressOrKey,
				Message: "Invalid address or key: " + err.Error(),
			}
		}

		// Ensure the address is one of the supported types and that
		// the network encoded with the address matches the network the
		// server is currently on.
		switch addr.(type) {
		case *btcutil.AddressPubKeyHash:
		case *btcutil.AddressScriptHash:
		default:
			return nil, &btcjson.RPCError{
				Code:    btcjson.ErrRPCInvalidAddressOrKey,
				Message: "Invalid address or key",
			}
		}
		if !addr.IsForNet(params) {
			return nil, &btcjson.RPCError{
				Code: btcjson.ErrRPCInvalidAddressOrKey,
				Message: "Invalid address: " + encodedAddr +
					" is for the wrong network",
			}
		}

		// Create a new script which pays to the provided address.
		pkScript, err := txscript.PayToAddrScript(addr)
		if err != nil {
			context := "Failed to generate pay-to-address script"
			return nil, internalRPCError(err.Error(), context)
		}

		// Convert the amount to satoshi.
		satoshi, err := btcutil.NewAmount(amount)
		if err != nil {
			context := "Failed to convert amount"
			return nil, internalRPCError(err.Error(), context)
		}

		txOut := wire.NewTxOut(int64(satoshi), pkScript)
		mtx.AddTxOut(txOut)
	}

	// Set the Locktime, if given.
	if c.LockTime != nil {
		mtx.LockTime = uint32(*c.LockTime)
	}

	// Return the serialized and hex-encoded transaction.  Note that this
	// is intentionally not directly returning because the first return
	// value is a string and it would result in returning an empty string to
	// the client instead of nothing (nil) in the case of an error.
	mtxHex, err := messageToHex(mtx)
	if err != nil {
		return nil, err
	}
	return mtxHex, nil
}

// handleDebugLevel handles debuglevel commands.
func handleDebugLevel(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.DebugLevelCmd)

	// Special show command to list supported subsystems.
	if c.LevelSpec == "show" {
		return fmt.Sprintf("Supported subsystems %v",
			supportedSubsystems()), nil
	}

	err := parseAndSetDebugLevels(c.LevelSpec)
	if err != nil {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCInvalidParams.Code,
			Message: err.Error(),
		}
	}

	return "Done.", nil
}

// witnessToHex formats the passed witness stack as a slice of hex-encoded
// strings to be used in a JSON response.
func witnessToHex(witness wire.TxWitness) []string {
	// Ensure nil is returned when there are no entries versus an empty
	// slice so it can properly be omitted as necessary.
	if len(witness) == 0 {
		return nil
	}

	result := make([]string, 0, len(witness))
	for _, wit := range witness {
		result = append(result, hex.EncodeToString(wit))
	}

	return result
}

// createVinList returns a slice of JSON objects for the inputs of the passed
// transaction.
func createVinList(mtx *wire.MsgTx) []btcjson.Vin {
	// Coinbase transactions only have a single txin by definition.
	vinList := make([]btcjson.Vin, len(mtx.TxIn))
	if blockchain.IsCoinBaseTx(mtx) {
		txIn := mtx.TxIn[0]
		vinList[0].Coinbase = hex.EncodeToString(txIn.SignatureScript)
		vinList[0].Sequence = txIn.Sequence
		vinList[0].Witness = witnessToHex(txIn.Witness)
		return vinList
	}

	for i, txIn := range mtx.TxIn {
		// The disassembled string will contain [error] inline
		// if the script doesn't fully parse, so ignore the
		// error here.
		disbuf, _ := txscript.DisasmString(txIn.SignatureScript)

		vinEntry := &vinList[i]
		vinEntry.Txid = txIn.PreviousOutPoint.Hash.String()
		vinEntry.Vout = txIn.PreviousOutPoint.Index
		vinEntry.Sequence = txIn.Sequence
		vinEntry.ScriptSig = &btcjson.ScriptSig{
			Asm: disbuf,
			Hex: hex.EncodeToString(txIn.SignatureScript),
		}

		if mtx.HasWitness() {
			vinEntry.Witness = witnessToHex(txIn.Witness)
		}
	}

	return vinList
}

// createVoutList returns a slice of JSON objects for the outputs of the passed
// transaction.
func createVoutList(mtx *wire.MsgTx, chainParams *chaincfg.Params, filterAddrMap map[string]struct{}) []btcjson.Vout {
	voutList := make([]btcjson.Vout, 0, len(mtx.TxOut))
	for i, v := range mtx.TxOut {
		// The disassembled string will contain [error] inline if the
		// script doesn't fully parse, so ignore the error here.
		disbuf, _ := txscript.DisasmString(v.PkScript)

		// Ignore the error here since an error means the script
		// couldn't parse and there is no additional information about
		// it anyways.
		scriptClass, addrs, reqSigs, _ := txscript.ExtractPkScriptAddrs(
			v.PkScript, chainParams)

		// Encode the addresses while checking if the address passes the
		// filter when needed.
		passesFilter := len(filterAddrMap) == 0
		encodedAddrs := make([]string, len(addrs))
		for j, addr := range addrs {
			encodedAddr := addr.EncodeAddress()
			encodedAddrs[j] = encodedAddr

			// No need to check the map again if the filter already
			// passes.
			if passesFilter {
				continue
			}
			if _, exists := filterAddrMap[encodedAddr]; exists {
				passesFilter = true
			}
		}

		if !passesFilter {
			continue
		}

		var vout btcjson.Vout
		vout.N = uint32(i)
		vout.Value = btcutil.Amount(v.Value).ToBTC()
		vout.ScriptPubKey.Addresses = encodedAddrs
		vout.ScriptPubKey.Asm = disbuf
		vout.ScriptPubKey.Hex = hex.EncodeToString(v.PkScript)
		vout.ScriptPubKey.Type = scriptClass.String()
		vout.ScriptPubKey.ReqSigs = int32(reqSigs)

		voutList = append(voutList, vout)
	}

	return voutList
}

// createTxRawResult converts the passed transaction and associated parameters
// to a raw transaction JSON object.
func createTxRawResult(chainParams *chaincfg.Params, mtx *wire.MsgTx,
	txHash string, blkHeader *wire.BlockHeader, blkHash string,
	blkHeight int32, chainHeight int32) (*btcjson.TxRawResult, error) {

	mtxHex, err := messageToHex(mtx)
	if err != nil {
		return nil, err
	}

	txReply := &btcjson.TxRawResult{
		Hex:      mtxHex,
		Txid:     txHash,
		Hash:     mtx.WitnessHash().String(),
		Size:     int32(mtx.SerializeSize()),
		Vsize:    int32(mempool.GetTxVirtualSize(btcutil.NewTx(mtx))),
		Vin:      createVinList(mtx),
		Vout:     createVoutList(mtx, chainParams, nil),
		Version:  mtx.Version,
		LockTime: mtx.LockTime,
	}

	if blkHeader != nil {
		// This is not a typo, they are identical in bitcoind as well.
		txReply.Time = blkHeader.Timestamp.Unix()
		txReply.Blocktime = blkHeader.Timestamp.Unix()
		txReply.BlockHash = blkHash
		txReply.Confirmations = uint64(1 + chainHeight - blkHeight)
	}

	return txReply, nil
}

// handleDecodeRawTransaction handles decoderawtransaction commands.
func handleDecodeRawTransaction(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.DecodeRawTransactionCmd)

	// Deserialize the transaction.
	hexStr := c.HexTx
	if len(hexStr)%2 != 0 {
		hexStr = "0" + hexStr
	}
	serializedTx, err := hex.DecodeString(hexStr)
	if err != nil {
		return nil, rpcDecodeHexError(hexStr)
	}
	var mtx wire.MsgTx
	err = mtx.Deserialize(bytes.NewReader(serializedTx))
	if err != nil {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCDeserialization,
			Message: "TX decode failed: " + err.Error(),
		}
	}

	// Create and return the result.
	txReply := btcjson.TxRawDecodeResult{
		Txid:     mtx.TxHash().String(),
		Version:  mtx.Version,
		Locktime: mtx.LockTime,
		Vin:      createVinList(&mtx),
		Vout:     createVoutList(&mtx, s.cfg.ChainParams, nil),
	}
	return txReply, nil
}

// handleDecodeScript handles decodescript commands.
func handleDecodeScript(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.DecodeScriptCmd)

	// Convert the hex script to bytes.
	hexStr := c.HexScript
	if len(hexStr)%2 != 0 {
		hexStr = "0" + hexStr
	}
	script, err := hex.DecodeString(hexStr)
	if err != nil {
		return nil, rpcDecodeHexError(hexStr)
	}

	// The disassembled string will contain [error] inline if the script
	// doesn't fully parse, so ignore the error here.
	disbuf, _ := txscript.DisasmString(script)

	// Get information about the script.
	// Ignore the error here since an error means the script couldn't parse
	// and there is no additinal information about it anyways.
	scriptClass, addrs, reqSigs, _ := txscript.ExtractPkScriptAddrs(script,
		s.cfg.ChainParams)
	addresses := make([]string, len(addrs))
	for i, addr := range addrs {
		addresses[i] = addr.EncodeAddress()
	}

	// Convert the script itself to a pay-to-script-hash address.
	p2sh, err := btcutil.NewAddressScriptHash(script, s.cfg.ChainParams)
	if err != nil {
		context := "Failed to convert script to pay-to-script-hash"
		return nil, internalRPCError(err.Error(), context)
	}

	// Generate and return the reply.
	reply := btcjson.DecodeScriptResult{
		Asm:       disbuf,
		ReqSigs:   int32(reqSigs),
		Type:      scriptClass.String(),
		Addresses: addresses,
	}
	if scriptClass != txscript.ScriptHashTy {
		reply.P2sh = p2sh.EncodeAddress()
	}
	return reply, nil
}

// handleEstimateFee handles estimatefee commands.
func handleEstimateFee(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.EstimateFeeCmd)

	if s.cfg.FeeEstimator == nil {
		return nil, errors.New("Fee estimation disabled")
	}

	if c.NumBlocks <= 0 {
		return -1.0, errors.New("Parameter NumBlocks must be positive")
	}

	feeRate, err := s.cfg.FeeEstimator.EstimateFee(uint32(c.NumBlocks))

	if err != nil {
		return -1.0, err
	}

	// Convert to satoshis per kb.
	return float64(feeRate), nil
}

// handleGenerate handles generate commands.
func handleGenerate(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	// Respond with an error if there are no addresses to pay the
	// created blocks to.
	if len(cfg.miningAddrs) == 0 {
		return nil, &btcjson.RPCError{
			Code: btcjson.ErrRPCInternal.Code,
			Message: "No payment addresses specified " +
				"via --miningaddr",
		}
	}

	// Respond with an error if there's virtually 0 chance of mining a block
	// with the CPU.
	if !s.cfg.ChainParams.GenerateSupported {
		return nil, &btcjson.RPCError{
			Code: btcjson.ErrRPCDifficulty,
			Message: fmt.Sprintf("No support for `generate` on "+
				"the current network, %s, as it's unlikely to "+
				"be possible to mine a block with the CPU.",
				s.cfg.ChainParams.Net),
		}
	}

	c := cmd.(*btcjson.GenerateCmd)

	// Respond with an error if the client is requesting 0 blocks to be generated.
	if c.NumBlocks == 0 {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCInternal.Code,
			Message: "Please request a nonzero number of blocks to generate.",
		}
	}

	// Create a reply
	reply := make([]string, c.NumBlocks)

	blockHashes, err := s.cfg.CPUMiner.GenerateNBlocks(c.NumBlocks)
	if err != nil {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCInternal.Code,
			Message: err.Error(),
		}
	}

	// Mine the correct number of blocks, assigning the hex representation of the
	// hash of each one to its place in the reply.
	for i, hash := range blockHashes {
		reply[i] = hash.String()
	}

	return reply, nil
}

// handleGetAddedNodeInfo handles getaddednodeinfo commands.
func handleGetAddedNodeInfo(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.GetAddedNodeInfoCmd)

	// Retrieve a list of persistent (added) peers from the server and
	// filter the list of peers per the specified address (if any).
	peers := s.cfg.ConnMgr.PersistentPeers()
	if c.Node != nil {
		node := *c.Node
		found := false
		for i, peer := range peers {
			if peer.ToPeer().Addr() == node {
				peers = peers[i : i+1]
				found = true
			}
		}
		if !found {
			return nil, &btcjson.RPCError{
				Code:    btcjson.ErrRPCClientNodeNotAdded,
				Message: "Node has not been added",
			}
		}
	}

	// Without the dns flag, the result is just a slice of the addresses as
	// strings.
	if !c.DNS {
		results := make([]string, 0, len(peers))
		for _, peer := range peers {
			results = append(results, peer.ToPeer().Addr())
		}
		return results, nil
	}

	// With the dns flag, the result is an array of JSON objects which
	// include the result of DNS lookups for each peer.
	results := make([]*btcjson.GetAddedNodeInfoResult, 0, len(peers))
	for _, rpcPeer := range peers {
		// Set the "address" of the peer which could be an ip address
		// or a domain name.
		peer := rpcPeer.ToPeer()
		var result btcjson.GetAddedNodeInfoResult
		result.AddedNode = peer.Addr()
		result.Connected = btcjson.Bool(peer.Connected())

		// Split the address into host and port portions so we can do
		// a DNS lookup against the host.  When no port is specified in
		// the address, just use the address as the host.
		host, _, err := net.SplitHostPort(peer.Addr())
		if err != nil {
			host = peer.Addr()
		}

		var ipList []string
		switch {
		case net.ParseIP(host) != nil, strings.HasSuffix(host, ".onion"):
			ipList = make([]string, 1)
			ipList[0] = host
		default:
			// Do a DNS lookup for the address.  If the lookup fails, just
			// use the host.
			ips, err := btcdLookup(host)
			if err != nil {
				ipList = make([]string, 1)
				ipList[0] = host
				break
			}
			ipList = make([]string, 0, len(ips))
			for _, ip := range ips {
				ipList = append(ipList, ip.String())
			}
		}

		// Add the addresses and connection info to the result.
		addrs := make([]btcjson.GetAddedNodeInfoResultAddr, 0, len(ipList))
		for _, ip := range ipList {
			var addr btcjson.GetAddedNodeInfoResultAddr
			addr.Address = ip
			addr.Connected = "false"
			if ip == host && peer.Connected() {
				addr.Connected = directionString(peer.Inbound())
			}
			addrs = append(addrs, addr)
		}
		result.Addresses = &addrs
		results = append(results, &result)
	}
	return results, nil
}

// handleGetBestBlock implements the getbestblock command.
func handleGetBestBlock(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	// All other "get block" commands give either the height, the
	// hash, or both but require the block SHA.  This gets both for
	// the best block.
	best := s.cfg.Chain.BestSnapshot()
	result := &btcjson.GetBestBlockResult{
		Hash:   best.Hash.String(),
		Height: best.Height,
	}
	return result, nil
}

// handleGetBestBlockHash implements the getbestblockhash command.
func handleGetBestBlockHash(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	best := s.cfg.Chain.BestSnapshot()
	return best.Hash.String(), nil
}

// getDifficultyRatio returns the proof-of-work difficulty as a multiple of the
// minimum difficulty using the passed bits field from the header of a block.
func getDifficultyRatio(bits uint32, params *chaincfg.Params) float64 {
	// The minimum difficulty is the max possible proof-of-work limit bits
	// converted back to a number.  Note this is not the same as the proof of
	// work limit directly because the block difficulty is encoded in a block
	// with the compact form which loses precision.
	max := blockchain.CompactToBig(params.PowLimitBits)
	target := blockchain.CompactToBig(bits)

	difficulty := new(big.Rat).SetFrac(max, target)
	outString := difficulty.FloatString(8)
	diff, err := strconv.ParseFloat(outString, 64)
	if err != nil {
		rpcsLog.Errorf("Cannot get difficulty: %v", err)
		return 0
	}
	return diff
}

// handleGetBlock implements the getblock command.
func handleGetBlock(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.GetBlockCmd)

	// Load the raw block bytes from the database.
	hash, err := chainhash.NewHashFromStr(c.Hash)
	if err != nil {
		return nil, rpcDecodeHexError(c.Hash)
	}
	var blkBytes []byte
	err = s.cfg.DB.View(func(dbTx database.Tx) error {
		var err error
		blkBytes, err = dbTx.FetchBlock(hash)
		return err
	})
	if err != nil {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCBlockNotFound,
			Message: "Block not found",
		}
	}

	// When the verbose flag isn't set, simply return the serialized block
	// as a hex-encoded string.
	if c.Verbose != nil && !*c.Verbose {
		return hex.EncodeToString(blkBytes), nil
	}

	// The verbose flag is set, so generate the JSON object and return it.

	// Deserialize the block.
	blk, err := btcutil.NewBlockFromBytes(blkBytes)
	if err != nil {
		context := "Failed to deserialize block"
		return nil, internalRPCError(err.Error(), context)
	}

	// Get the block height from chain.
	blockHeight, err := s.cfg.Chain.BlockHeightByHash(hash)
	if err != nil {
		context := "Failed to obtain block height"
		return nil, internalRPCError(err.Error(), context)
	}
	blk.SetHeight(blockHeight)
	best := s.cfg.Chain.BestSnapshot()

	// Get next block hash unless there are none.
	var nextHashString string
	if blockHeight < best.Height {
		nextHash, err := s.cfg.Chain.BlockHashByHeight(blockHeight + 1)
		if err != nil {
			context := "No next block"
			return nil, internalRPCError(err.Error(), context)
		}
		nextHashString = nextHash.String()
	}

	params := s.cfg.ChainParams
	blockHeader := &blk.MsgBlock().Header
	blockReply := btcjson.GetBlockVerboseResult{
		Hash:          c.Hash,
		Version:       blockHeader.Version,
		VersionHex:    fmt.Sprintf("%08x", blockHeader.Version),
		MerkleRoot:    blockHeader.MerkleRoot.String(),
		PreviousHash:  blockHeader.PrevBlock.String(),
		Nonce:         blockHeader.Nonce,
		Time:          blockHeader.Timestamp.Unix(),
		Confirmations: uint64(1 + best.Height - blockHeight),
		Height:        int64(blockHeight),
		Size:          int32(len(blkBytes)),
		StrippedSize:  int32(blk.MsgBlock().SerializeSizeStripped()),
		Weight:        int32(blockchain.GetBlockWeight(blk)),
		Bits:          strconv.FormatInt(int64(blockHeader.Bits), 16),
		Difficulty:    getDifficultyRatio(blockHeader.Bits, params),
		NextHash:      nextHashString,
	}

	if c.VerboseTx == nil || !*c.VerboseTx {
		transactions := blk.Transactions()
		txNames := make([]string, len(transactions))
		for i, tx := range transactions {
			txNames[i] = tx.Hash().String()
		}

		blockReply.Tx = txNames
	} else {
		txns := blk.Transactions()
		rawTxns := make([]btcjson.TxRawResult, len(txns))
		for i, tx := range txns {
			rawTxn, err := createTxRawResult(params, tx.MsgTx(),
				tx.Hash().String(), blockHeader, hash.String(),
				blockHeight, best.Height)
			if err != nil {
				return nil, err
			}
			rawTxns[i] = *rawTxn
		}
		blockReply.RawTx = rawTxns
	}

	return blockReply, nil
}

// softForkStatus converts a ThresholdState state into a human readable string
// corresponding to the particular state.
func softForkStatus(state blockchain.ThresholdState) (string, error) {
	switch state {
	case blockchain.ThresholdDefined:
		return "defined", nil
	case blockchain.ThresholdStarted:
		return "started", nil
	case blockchain.ThresholdLockedIn:
		return "lockedin", nil
	case blockchain.ThresholdActive:
		return "active", nil
	case blockchain.ThresholdFailed:
		return "failed", nil
	default:
		return "", fmt.Errorf("unknown deployment state: %v", state)
	}
}

// handleGetBlockChainInfo implements the getblockchaininfo command.
func handleGetBlockChainInfo(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	// Obtain a snapshot of the current best known blockchain state. We'll
	// populate the response to this call primarily from this snapshot.
	params := s.cfg.ChainParams
	chain := s.cfg.Chain
	chainSnapshot := chain.BestSnapshot()

	chainInfo := &btcjson.GetBlockChainInfoResult{
		Chain:         params.Name,
		Blocks:        chainSnapshot.Height,
		Headers:       chainSnapshot.Height,
		BestBlockHash: chainSnapshot.Hash.String(),
		Difficulty:    getDifficultyRatio(chainSnapshot.Bits, params),
		MedianTime:    chainSnapshot.MedianTime.Unix(),
		Pruned:        false,
		Bip9SoftForks: make(map[string]*btcjson.Bip9SoftForkDescription),
	}

	// Next, populate the response with information describing the current
	// status of soft-forks deployed via the super-majority block
	// signalling mechanism.
	height := chainSnapshot.Height
	chainInfo.SoftForks = []*btcjson.SoftForkDescription{
		{
			ID:      "bip34",
			Version: 2,
			Reject: struct {
				Status bool `json:"status"`
			}{
				Status: height >= params.BIP0034Height,
			},
		},
		{
			ID:      "bip66",
			Version: 3,
			Reject: struct {
				Status bool `json:"status"`
			}{
				Status: height >= params.BIP0066Height,
			},
		},
		{
			ID:      "bip65",
			Version: 4,
			Reject: struct {
				Status bool `json:"status"`
			}{
				Status: height >= params.BIP0065Height,
			},
		},
	}

	// Finally, query the BIP0009 version bits state for all currently
	// defined BIP0009 soft-fork deployments.
	for deployment, deploymentDetails := range params.Deployments {
		// Map the integer deployment ID into a human readable
		// fork-name.
		var forkName string
		switch deployment {
		case chaincfg.DeploymentTestDummy:
			forkName = "dummy"

		case chaincfg.DeploymentCSV:
			forkName = "csv"

		case chaincfg.DeploymentSegwit:
			forkName = "segwit"

		default:
			return nil, &btcjson.RPCError{
				Code: btcjson.ErrRPCInternal.Code,
				Message: fmt.Sprintf("Unknown deployment %v "+
					"detected", deployment),
			}
		}

		// Query the chain for the current status of the deployment as
		// identified by its deployment ID.
		deploymentStatus, err := chain.ThresholdState(uint32(deployment))
		if err != nil {
			context := "Failed to obtain deployment status"
			return nil, internalRPCError(err.Error(), context)
		}

		// Attempt to convert the current deployment status into a
		// human readable string. If the status is unrecognized, then a
		// non-nil error is returned.
		statusString, err := softForkStatus(deploymentStatus)
		if err != nil {
			return nil, &btcjson.RPCError{
				Code: btcjson.ErrRPCInternal.Code,
				Message: fmt.Sprintf("unknown deployment status: %v",
					deploymentStatus),
			}
		}

		// Finally, populate the soft-fork description with all the
		// information gathered above.
		chainInfo.Bip9SoftForks[forkName] = &btcjson.Bip9SoftForkDescription{
			Status:    strings.ToLower(statusString),
			Bit:       deploymentDetails.BitNumber,
			StartTime: int64(deploymentDetails.StartTime),
			Timeout:   int64(deploymentDetails.ExpireTime),
		}
	}

	return chainInfo, nil
}

// handleGetBlockCount implements the getblockcount command.
func handleGetBlockCount(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	best := s.cfg.Chain.BestSnapshot()
	return int64(best.Height), nil
}

// handleGetBlockHash implements the getblockhash command.
func handleGetBlockHash(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.GetBlockHashCmd)
	hash, err := s.cfg.Chain.BlockHashByHeight(int32(c.Index))
	if err != nil {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCOutOfRange,
			Message: "Block number out of range",
		}
	}

	return hash.String(), nil
}

// handleGetBlockHeader implements the getblockheader command.
func handleGetBlockHeader(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.GetBlockHeaderCmd)

	// Fetch the header from chain.
	hash, err := chainhash.NewHashFromStr(c.Hash)
	if err != nil {
		return nil, rpcDecodeHexError(c.Hash)
	}
	blockHeader, err := s.cfg.Chain.HeaderByHash(hash)
	if err != nil {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCBlockNotFound,
			Message: "Block not found",
		}
	}

	// When the verbose flag isn't set, simply return the serialized block
	// header as a hex-encoded string.
	if c.Verbose != nil && !*c.Verbose {
		var headerBuf bytes.Buffer
		err := blockHeader.Serialize(&headerBuf)
		if err != nil {
			context := "Failed to serialize block header"
			return nil, internalRPCError(err.Error(), context)
		}
		return hex.EncodeToString(headerBuf.Bytes()), nil
	}

	// The verbose flag is set, so generate the JSON object and return it.

	// Get the block height from chain.
	blockHeight, err := s.cfg.Chain.BlockHeightByHash(hash)
	if err != nil {
		context := "Failed to obtain block height"
		return nil, internalRPCError(err.Error(), context)
	}
	best := s.cfg.Chain.BestSnapshot()

	// Get next block hash unless there are none.
	var nextHashString string
	if blockHeight < best.Height {
		nextHash, err := s.cfg.Chain.BlockHashByHeight(blockHeight + 1)
		if err != nil {
			context := "No next block"
			return nil, internalRPCError(err.Error(), context)
		}
		nextHashString = nextHash.String()
	}

	params := s.cfg.ChainParams
	blockHeaderReply := btcjson.GetBlockHeaderVerboseResult{
		Hash:          c.Hash,
		Confirmations: uint64(1 + best.Height - blockHeight),
		Height:        blockHeight,
		Version:       blockHeader.Version,
		VersionHex:    fmt.Sprintf("%08x", blockHeader.Version),
		MerkleRoot:    blockHeader.MerkleRoot.String(),
		NextHash:      nextHashString,
		PreviousHash:  blockHeader.PrevBlock.String(),
		Nonce:         uint64(blockHeader.Nonce),
		Time:          blockHeader.Timestamp.Unix(),
		Bits:          strconv.FormatInt(int64(blockHeader.Bits), 16),
		Difficulty:    getDifficultyRatio(blockHeader.Bits, params),
	}
	return blockHeaderReply, nil
}

// encodeTemplateID encodes the passed details into an ID that can be used to
// uniquely identify a block template.
func encodeTemplateID(prevHash *chainhash.Hash, lastGenerated time.Time) string {
	return fmt.Sprintf("%s-%d", prevHash.String(), lastGenerated.Unix())
}

// decodeTemplateID decodes an ID that is used to uniquely identify a block
// template.  This is mainly used as a mechanism to track when to update clients
// that are using long polling for block templates.  The ID consists of the
// previous block hash for the associated template and the time the associated
// template was generated.
func decodeTemplateID(templateID string) (*chainhash.Hash, int64, error) {
	fields := strings.Split(templateID, "-")
	if len(fields) != 2 {
		return nil, 0, errors.New("invalid longpollid format")
	}

	prevHash, err := chainhash.NewHashFromStr(fields[0])
	if err != nil {
		return nil, 0, errors.New("invalid longpollid format")
	}
	lastGenerated, err := strconv.ParseInt(fields[1], 10, 64)
	if err != nil {
		return nil, 0, errors.New("invalid longpollid format")
	}

	return prevHash, lastGenerated, nil
}

// notifyLongPollers notifies any channels that have been registered to be
// notified when block templates are stale.
//
// This function MUST be called with the state locked.
func (state *gbtWorkState) notifyLongPollers(latestHash *chainhash.Hash, lastGenerated time.Time) {
	// Notify anything that is waiting for a block template update from a
	// hash which is not the hash of the tip of the best chain since their
	// work is now invalid.
	for hash, channels := range state.notifyMap {
		if !hash.IsEqual(latestHash) {
			for _, c := range channels {
				close(c)
			}
			delete(state.notifyMap, hash)
		}
	}

	// Return now if the provided last generated timestamp has not been
	// initialized.
	if lastGenerated.IsZero() {
		return
	}

	// Return now if there is nothing registered for updates to the current
	// best block hash.
	channels, ok := state.notifyMap[*latestHash]
	if !ok {
		return
	}

	// Notify anything that is waiting for a block template update from a
	// block template generated before the most recently generated block
	// template.
	lastGeneratedUnix := lastGenerated.Unix()
	for lastGen, c := range channels {
		if lastGen < lastGeneratedUnix {
			close(c)
			delete(channels, lastGen)
		}
	}

	// Remove the entry altogether if there are no more registered
	// channels.
	if len(channels) == 0 {
		delete(state.notifyMap, *latestHash)
	}
}

// NotifyBlockConnected uses the newly-connected block to notify any long poll
// clients with a new block template when their existing block template is
// stale due to the newly connected block.
func (state *gbtWorkState) NotifyBlockConnected(blockHash *chainhash.Hash) {
	go func() {
		state.Lock()
		defer state.Unlock()

		state.notifyLongPollers(blockHash, state.lastTxUpdate)
	}()
}

// NotifyMempoolTx uses the new last updated time for the transaction memory
// pool to notify any long poll clients with a new block template when their
// existing block template is stale due to enough time passing and the contents
// of the memory pool changing.
func (state *gbtWorkState) NotifyMempoolTx(lastUpdated time.Time) {
	go func() {
		state.Lock()
		defer state.Unlock()

		// No need to notify anything if no block templates have been generated
		// yet.
		if state.prevHash == nil || state.lastGenerated.IsZero() {
			return
		}

		if time.Now().After(state.lastGenerated.Add(time.Second *
			gbtRegenerateSeconds)) {

			state.notifyLongPollers(state.prevHash, lastUpdated)
		}
	}()
}

// templateUpdateChan returns a channel that will be closed once the block
// template associated with the passed previous hash and last generated time
// is stale.  The function will return existing channels for duplicate
// parameters which allows multiple clients to wait for the same block template
// without requiring a different channel for each client.
//
// This function MUST be called with the state locked.
func (state *gbtWorkState) templateUpdateChan(prevHash *chainhash.Hash, lastGenerated int64) chan struct{} {
	// Either get the current list of channels waiting for updates about
	// changes to block template for the previous hash or create a new one.
	channels, ok := state.notifyMap[*prevHash]
	if !ok {
		m := make(map[int64]chan struct{})
		state.notifyMap[*prevHash] = m
		channels = m
	}

	// Get the current channel associated with the time the block template
	// was last generated or create a new one.
	c, ok := channels[lastGenerated]
	if !ok {
		c = make(chan struct{})
		channels[lastGenerated] = c
	}

	return c
}

// updateBlockTemplate creates or updates a block template for the work state.
// A new block template will be generated when the current best block has
// changed or the transactions in the memory pool have been updated and it has
// been long enough since the last template was generated.  Otherwise, the
// timestamp for the existing block template is updated (and possibly the
// difficulty on testnet per the consesus rules).  Finally, if the
// useCoinbaseValue flag is false and the existing block template does not
// already contain a valid payment address, the block template will be updated
// with a randomly selected payment address from the list of configured
// addresses.
//
// This function MUST be called with the state locked.
func (state *gbtWorkState) updateBlockTemplate(s *rpcServer, useCoinbaseValue bool) error {
	generator := s.cfg.Generator
	lastTxUpdate := generator.TxSource().LastUpdated()
	if lastTxUpdate.IsZero() {
		lastTxUpdate = time.Now()
	}

	// Generate a new block template when the current best block has
	// changed or the transactions in the memory pool have been updated and
	// it has been at least gbtRegenerateSecond since the last template was
	// generated.
	var msgBlock *wire.MsgBlock
	var targetDifficulty string
	latestHash := &s.cfg.Chain.BestSnapshot().Hash
	template := state.template
	if template == nil || state.prevHash == nil ||
		!state.prevHash.IsEqual(latestHash) ||
		(state.lastTxUpdate != lastTxUpdate &&
			time.Now().After(state.lastGenerated.Add(time.Second*
				gbtRegenerateSeconds))) {

		// Reset the previous best hash the block template was generated
		// against so any errors below cause the next invocation to try
		// again.
		state.prevHash = nil

		// Choose a payment address at random if the caller requests a
		// full coinbase as opposed to only the pertinent details needed
		// to create their own coinbase.
		var payAddr btcutil.Address
		if !useCoinbaseValue {
			payAddr = cfg.miningAddrs[rand.Intn(len(cfg.miningAddrs))]
		}

		// Create a new block template that has a coinbase which anyone
		// can redeem.  This is only acceptable because the returned
		// block template doesn't include the coinbase, so the caller
		// will ultimately create their own coinbase which pays to the
		// appropriate address(es).
		blkTemplate, err := generator.NewBlockTemplate(payAddr)
		if err != nil {
			return internalRPCError("Failed to create new block "+
				"template: "+err.Error(), "")
		}
		template = blkTemplate
		msgBlock = template.Block
		targetDifficulty = fmt.Sprintf("%064x",
			blockchain.CompactToBig(msgBlock.Header.Bits))

		// Get the minimum allowed timestamp for the block based on the
		// median timestamp of the last several blocks per the chain
		// consensus rules.
		best := s.cfg.Chain.BestSnapshot()
		minTimestamp := mining.MinimumMedianTime(best)

		// Update work state to ensure another block template isn't
		// generated until needed.
		state.template = template
		state.lastGenerated = time.Now()
		state.lastTxUpdate = lastTxUpdate
		state.prevHash = latestHash
		state.minTimestamp = minTimestamp

		rpcsLog.Debugf("Generated block template (timestamp %v, "+
			"target %s, merkle root %s)",
			msgBlock.Header.Timestamp, targetDifficulty,
			msgBlock.Header.MerkleRoot)

		// Notify any clients that are long polling about the new
		// template.
		state.notifyLongPollers(latestHash, lastTxUpdate)
	} else {
		// At this point, there is a saved block template and another
		// request for a template was made, but either the available
		// transactions haven't change or it hasn't been long enough to
		// trigger a new block template to be generated.  So, update the
		// existing block template.

		// When the caller requires a full coinbase as opposed to only
		// the pertinent details needed to create their own coinbase,
		// add a payment address to the output of the coinbase of the
		// template if it doesn't already have one.  Since this requires
		// mining addresses to be specified via the config, an error is
		// returned if none have been specified.
		if !useCoinbaseValue && !template.ValidPayAddress {
			// Choose a payment address at random.
			payToAddr := cfg.miningAddrs[rand.Intn(len(cfg.miningAddrs))]

			// Update the block coinbase output of the template to
			// pay to the randomly selected payment address.
			pkScript, err := txscript.PayToAddrScript(payToAddr)
			if err != nil {
				context := "Failed to create pay-to-addr script"
				return internalRPCError(err.Error(), context)
			}
			template.Block.Transactions[0].TxOut[0].PkScript = pkScript
			template.ValidPayAddress = true

			// Update the merkle root.
			block := btcutil.NewBlock(template.Block)
			merkles := blockchain.BuildMerkleTreeStore(block.Transactions(), false)
			template.Block.Header.MerkleRoot = *merkles[len(merkles)-1]
		}

		// Set locals for convenience.
		msgBlock = template.Block
		targetDifficulty = fmt.Sprintf("%064x",
			blockchain.CompactToBig(msgBlock.Header.Bits))

		// Update the time of the block template to the current time
		// while accounting for the median time of the past several
		// blocks per the chain consensus rules.
		generator.UpdateBlockTime(msgBlock)
		msgBlock.Header.Nonce = 0

		rpcsLog.Debugf("Updated block template (timestamp %v, "+
			"target %s)", msgBlock.Header.Timestamp,
			targetDifficulty)
	}

	return nil
}

// blockTemplateResult returns the current block template associated with the
// state as a btcjson.GetBlockTemplateResult that is ready to be encoded to JSON
// and returned to the caller.
//
// This function MUST be called with the state locked.
func (state *gbtWorkState) blockTemplateResult(useCoinbaseValue bool, submitOld *bool) (*btcjson.GetBlockTemplateResult, error) {
	// Ensure the timestamps are still in valid range for the template.
	// This should really only ever happen if the local clock is changed
	// after the template is generated, but it's important to avoid serving
	// invalid block templates.
	template := state.template
	msgBlock := template.Block
	header := &msgBlock.Header
	adjustedTime := state.timeSource.AdjustedTime()
	maxTime := adjustedTime.Add(time.Second * blockchain.MaxTimeOffsetSeconds)
	if header.Timestamp.After(maxTime) {
		return nil, &btcjson.RPCError{
			Code: btcjson.ErrRPCOutOfRange,
			Message: fmt.Sprintf("The template time is after the "+
				"maximum allowed time for a block - template "+
				"time %v, maximum time %v", adjustedTime,
				maxTime),
		}
	}

	// Convert each transaction in the block template to a template result
	// transaction.  The result does not include the coinbase, so notice
	// the adjustments to the various lengths and indices.
	numTx := len(msgBlock.Transactions)
	transactions := make([]btcjson.GetBlockTemplateResultTx, 0, numTx-1)
	txIndex := make(map[chainhash.Hash]int64, numTx)
	for i, tx := range msgBlock.Transactions {
		txHash := tx.TxHash()
		txIndex[txHash] = int64(i)

		// Skip the coinbase transaction.
		if i == 0 {
			continue
		}

		// Create an array of 1-based indices to transactions that come
		// before this one in the transactions list which this one
		// depends on.  This is necessary since the created block must
		// ensure proper ordering of the dependencies.  A map is used
		// before creating the final array to prevent duplicate entries
		// when multiple inputs reference the same transaction.
		dependsMap := make(map[int64]struct{})
		for _, txIn := range tx.TxIn {
			if idx, ok := txIndex[txIn.PreviousOutPoint.Hash]; ok {
				dependsMap[idx] = struct{}{}
			}
		}
		depends := make([]int64, 0, len(dependsMap))
		for idx := range dependsMap {
			depends = append(depends, idx)
		}

		// Serialize the transaction for later conversion to hex.
		txBuf := bytes.NewBuffer(make([]byte, 0, tx.SerializeSize()))
		if err := tx.Serialize(txBuf); err != nil {
			context := "Failed to serialize transaction"
			return nil, internalRPCError(err.Error(), context)
		}

		bTx := btcutil.NewTx(tx)
		resultTx := btcjson.GetBlockTemplateResultTx{
			Data:    hex.EncodeToString(txBuf.Bytes()),
			Hash:    txHash.String(),
			Depends: depends,
			Fee:     template.Fees[i],
			SigOps:  template.SigOpCosts[i],
			Weight:  blockchain.GetTransactionWeight(bTx),
		}
		transactions = append(transactions, resultTx)
	}

	// Generate the block template reply.  Note that following mutations are
	// implied by the included or omission of fields:
	//  Including MinTime -> time/decrement
	//  Omitting CoinbaseTxn -> coinbase, generation
	targetDifficulty := fmt.Sprintf("%064x", blockchain.CompactToBig(header.Bits))
	templateID := encodeTemplateID(state.prevHash, state.lastGenerated)
	reply := btcjson.GetBlockTemplateResult{
		Bits:         strconv.FormatInt(int64(header.Bits), 16),
		CurTime:      header.Timestamp.Unix(),
		Height:       int64(template.Height),
		PreviousHash: header.PrevBlock.String(),
		WeightLimit:  blockchain.MaxBlockWeight,
		SigOpLimit:   blockchain.MaxBlockSigOpsCost,
		SizeLimit:    wire.MaxBlockPayload,
		Transactions: transactions,
		Version:      header.Version,
		LongPollID:   templateID,
		SubmitOld:    submitOld,
		Target:       targetDifficulty,
		MinTime:      state.minTimestamp.Unix(),
		MaxTime:      maxTime.Unix(),
		Mutable:      gbtMutableFields,
		NonceRange:   gbtNonceRange,
		Capabilities: gbtCapabilities,
	}
	// If the generated block template includes transactions with witness
	// data, then include the witness commitment in the GBT result.
	if template.WitnessCommitment != nil {
		reply.DefaultWitnessCommitment = hex.EncodeToString(template.WitnessCommitment)
	}

	if useCoinbaseValue {
		reply.CoinbaseAux = gbtCoinbaseAux
		reply.CoinbaseValue = &msgBlock.Transactions[0].TxOut[0].Value
	} else {
		// Ensure the template has a valid payment address associated
		// with it when a full coinbase is requested.
		if !template.ValidPayAddress {
			return nil, &btcjson.RPCError{
				Code: btcjson.ErrRPCInternal.Code,
				Message: "A coinbase transaction has been " +
					"requested, but the server has not " +
					"been configured with any payment " +
					"addresses via --miningaddr",
			}
		}

		// Serialize the transaction for conversion to hex.
		tx := msgBlock.Transactions[0]
		txBuf := bytes.NewBuffer(make([]byte, 0, tx.SerializeSize()))
		if err := tx.Serialize(txBuf); err != nil {
			context := "Failed to serialize transaction"
			return nil, internalRPCError(err.Error(), context)
		}

		resultTx := btcjson.GetBlockTemplateResultTx{
			Data:    hex.EncodeToString(txBuf.Bytes()),
			Hash:    tx.TxHash().String(),
			Depends: []int64{},
			Fee:     template.Fees[0],
			SigOps:  template.SigOpCosts[0],
		}

		reply.CoinbaseTxn = &resultTx
	}

	return &reply, nil
}

// handleGetBlockTemplateLongPoll is a helper for handleGetBlockTemplateRequest
// which deals with handling long polling for block templates.  When a caller
// sends a request with a long poll ID that was previously returned, a response
// is not sent until the caller should stop working on the previous block
// template in favor of the new one.  In particular, this is the case when the
// old block template is no longer valid due to a solution already being found
// and added to the block chain, or new transactions have shown up and some time
// has passed without finding a solution.
//
// See https://en.bitcoin.it/wiki/BIP_0022 for more details.
func handleGetBlockTemplateLongPoll(s *rpcServer, longPollID string, useCoinbaseValue bool, closeChan <-chan struct{}) (interface{}, error) {
	state := s.gbtWorkState
	state.Lock()
	// The state unlock is intentionally not deferred here since it needs to
	// be manually unlocked before waiting for a notification about block
	// template changes.

	if err := state.updateBlockTemplate(s, useCoinbaseValue); err != nil {
		state.Unlock()
		return nil, err
	}

	// Just return the current block template if the long poll ID provided by
	// the caller is invalid.
	prevHash, lastGenerated, err := decodeTemplateID(longPollID)
	if err != nil {
		result, err := state.blockTemplateResult(useCoinbaseValue, nil)
		if err != nil {
			state.Unlock()
			return nil, err
		}

		state.Unlock()
		return result, nil
	}

	// Return the block template now if the specific block template
	// identified by the long poll ID no longer matches the current block
	// template as this means the provided template is stale.
	prevTemplateHash := &state.template.Block.Header.PrevBlock
	if !prevHash.IsEqual(prevTemplateHash) ||
		lastGenerated != state.lastGenerated.Unix() {

		// Include whether or not it is valid to submit work against the
		// old block template depending on whether or not a solution has
		// already been found and added to the block chain.
		submitOld := prevHash.IsEqual(prevTemplateHash)
		result, err := state.blockTemplateResult(useCoinbaseValue,
			&submitOld)
		if err != nil {
			state.Unlock()
			return nil, err
		}

		state.Unlock()
		return result, nil
	}

	// Register the previous hash and last generated time for notifications
	// Get a channel that will be notified when the template associated with
	// the provided ID is stale and a new block template should be returned to
	// the caller.
	longPollChan := state.templateUpdateChan(prevHash, lastGenerated)
	state.Unlock()

	select {
	// When the client closes before it's time to send a reply, just return
	// now so the goroutine doesn't hang around.
	case <-closeChan:
		return nil, ErrClientQuit

	// Wait until signal received to send the reply.
	case <-longPollChan:
		// Fallthrough
	}

	// Get the lastest block template
	state.Lock()
	defer state.Unlock()

	if err := state.updateBlockTemplate(s, useCoinbaseValue); err != nil {
		return nil, err
	}

	// Include whether or not it is valid to submit work against the old
	// block template depending on whether or not a solution has already
	// been found and added to the block chain.
	submitOld := prevHash.IsEqual(&state.template.Block.Header.PrevBlock)
	result, err := state.blockTemplateResult(useCoinbaseValue, &submitOld)
	if err != nil {
		return nil, err
	}

	return result, nil
}

// handleGetBlockTemplateRequest is a helper for handleGetBlockTemplate which
// deals with generating and returning block templates to the caller.  It
// handles both long poll requests as specified by BIP 0022 as well as regular
// requests.  In addition, it detects the capabilities reported by the caller
// in regards to whether or not it supports creating its own coinbase (the
// coinbasetxn and coinbasevalue capabilities) and modifies the returned block
// template accordingly.
func handleGetBlockTemplateRequest(s *rpcServer, request *btcjson.TemplateRequest, closeChan <-chan struct{}) (interface{}, error) {
	// Extract the relevant passed capabilities and restrict the result to
	// either a coinbase value or a coinbase transaction object depending on
	// the request.  Default to only providing a coinbase value.
	useCoinbaseValue := true
	if request != nil {
		var hasCoinbaseValue, hasCoinbaseTxn bool
		for _, capability := range request.Capabilities {
			switch capability {
			case "coinbasetxn":
				hasCoinbaseTxn = true
			case "coinbasevalue":
				hasCoinbaseValue = true
			}
		}

		if hasCoinbaseTxn && !hasCoinbaseValue {
			useCoinbaseValue = false
		}
	}

	// When a coinbase transaction has been requested, respond with an error
	// if there are no addresses to pay the created block template to.
	if !useCoinbaseValue && len(cfg.miningAddrs) == 0 {
		return nil, &btcjson.RPCError{
			Code: btcjson.ErrRPCInternal.Code,
			Message: "A coinbase transaction has been requested, " +
				"but the server has not been configured with " +
				"any payment addresses via --miningaddr",
		}
	}

	// Return an error if there are no peers connected since there is no
	// way to relay a found block or receive transactions to work on.
	// However, allow this state when running in the regression test or
	// simulation test mode.
	if !(cfg.RegressionTest || cfg.SimNet) &&
		s.cfg.ConnMgr.ConnectedCount() == 0 {

		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCClientNotConnected,
			Message: "Bitcoin is not connected",
		}
	}

	// No point in generating or accepting work before the chain is synced.
	currentHeight := s.cfg.Chain.BestSnapshot().Height
	if currentHeight != 0 && !s.cfg.SyncMgr.IsCurrent() {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCClientInInitialDownload,
			Message: "Bitcoin is downloading blocks...",
		}
	}

	// When a long poll ID was provided, this is a long poll request by the
	// client to be notified when block template referenced by the ID should
	// be replaced with a new one.
	if request != nil && request.LongPollID != "" {
		return handleGetBlockTemplateLongPoll(s, request.LongPollID,
			useCoinbaseValue, closeChan)
	}

	// Protect concurrent access when updating block templates.
	state := s.gbtWorkState
	state.Lock()
	defer state.Unlock()

	// Get and return a block template.  A new block template will be
	// generated when the current best block has changed or the transactions
	// in the memory pool have been updated and it has been at least five
	// seconds since the last template was generated.  Otherwise, the
	// timestamp for the existing block template is updated (and possibly
	// the difficulty on testnet per the consesus rules).
	if err := state.updateBlockTemplate(s, useCoinbaseValue); err != nil {
		return nil, err
	}
	return state.blockTemplateResult(useCoinbaseValue, nil)
}

// chainErrToGBTErrString converts an error returned from btcchain to a string
// which matches the reasons and format described in BIP0022 for rejection
// reasons.
func chainErrToGBTErrString(err error) string {
	// When the passed error is not a RuleError, just return a generic
	// rejected string with the error text.
	ruleErr, ok := err.(blockchain.RuleError)
	if !ok {
		return "rejected: " + err.Error()
	}

	switch ruleErr.ErrorCode {
	case blockchain.ErrDuplicateBlock:
		return "duplicate"
	case blockchain.ErrBlockTooBig:
		return "bad-blk-length"
	case blockchain.ErrBlockWeightTooHigh:
		return "bad-blk-weight"
	case blockchain.ErrBlockVersionTooOld:
		return "bad-version"
	case blockchain.ErrInvalidTime:
		return "bad-time"
	case blockchain.ErrTimeTooOld:
		return "time-too-old"
	case blockchain.ErrTimeTooNew:
		return "time-too-new"
	case blockchain.ErrDifficultyTooLow:
		return "bad-diffbits"
	case blockchain.ErrUnexpectedDifficulty:
		return "bad-diffbits"
	case blockchain.ErrHighHash:
		return "high-hash"
	case blockchain.ErrBadMerkleRoot:
		return "bad-txnmrklroot"
	case blockchain.ErrBadCheckpoint:
		return "bad-checkpoint"
	case blockchain.ErrForkTooOld:
		return "fork-too-old"
	case blockchain.ErrCheckpointTimeTooOld:
		return "checkpoint-time-too-old"
	case blockchain.ErrNoTransactions:
		return "bad-txns-none"
	case blockchain.ErrNoTxInputs:
		return "bad-txns-noinputs"
	case blockchain.ErrNoTxOutputs:
		return "bad-txns-nooutputs"
	case blockchain.ErrTxTooBig:
		return "bad-txns-size"
	case blockchain.ErrBadTxOutValue:
		return "bad-txns-outputvalue"
	case blockchain.ErrDuplicateTxInputs:
		return "bad-txns-dupinputs"
	case blockchain.ErrBadTxInput:
		return "bad-txns-badinput"
	case blockchain.ErrMissingTxOut:
		return "bad-txns-missinginput"
	case blockchain.ErrUnfinalizedTx:
		return "bad-txns-unfinalizedtx"
	case blockchain.ErrDuplicateTx:
		return "bad-txns-duplicate"
	case blockchain.ErrOverwriteTx:
		return "bad-txns-overwrite"
	case blockchain.ErrImmatureSpend:
		return "bad-txns-maturity"
	case blockchain.ErrSpendTooHigh:
		return "bad-txns-highspend"
	case blockchain.ErrBadFees:
		return "bad-txns-fees"
	case blockchain.ErrTooManySigOps:
		return "high-sigops"
	case blockchain.ErrFirstTxNotCoinbase:
		return "bad-txns-nocoinbase"
	case blockchain.ErrMultipleCoinbases:
		return "bad-txns-multicoinbase"
	case blockchain.ErrBadCoinbaseScriptLen:
		return "bad-cb-length"
	case blockchain.ErrBadCoinbaseValue:
		return "bad-cb-value"
	case blockchain.ErrMissingCoinbaseHeight:
		return "bad-cb-height"
	case blockchain.ErrBadCoinbaseHeight:
		return "bad-cb-height"
	case blockchain.ErrScriptMalformed:
		return "bad-script-malformed"
	case blockchain.ErrScriptValidation:
		return "bad-script-validate"
	case blockchain.ErrUnexpectedWitness:
		return "unexpected-witness"
	case blockchain.ErrInvalidWitnessCommitment:
		return "bad-witness-nonce-size"
	case blockchain.ErrWitnessCommitmentMismatch:
		return "bad-witness-merkle-match"
	case blockchain.ErrPreviousBlockUnknown:
		return "prev-blk-not-found"
	case blockchain.ErrInvalidAncestorBlock:
		return "bad-prevblk"
	case blockchain.ErrPrevBlockNotBest:
		return "inconclusive-not-best-prvblk"
	}

	return "rejected: " + err.Error()
}

// handleGetBlockTemplateProposal is a helper for handleGetBlockTemplate which
// deals with block proposals.
//
// See https://en.bitcoin.it/wiki/BIP_0023 for more details.
func handleGetBlockTemplateProposal(s *rpcServer, request *btcjson.TemplateRequest) (interface{}, error) {
	hexData := request.Data
	if hexData == "" {
		return false, &btcjson.RPCError{
			Code: btcjson.ErrRPCType,
			Message: fmt.Sprintf("Data must contain the " +
				"hex-encoded serialized block that is being " +
				"proposed"),
		}
	}

	// Ensure the provided data is sane and deserialize the proposed block.
	if len(hexData)%2 != 0 {
		hexData = "0" + hexData
	}
	dataBytes, err := hex.DecodeString(hexData)
	if err != nil {
		return false, &btcjson.RPCError{
			Code: btcjson.ErrRPCDeserialization,
			Message: fmt.Sprintf("Data must be "+
				"hexadecimal string (not %q)", hexData),
		}
	}
	var msgBlock wire.MsgBlock
	if err := msgBlock.Deserialize(bytes.NewReader(dataBytes)); err != nil {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCDeserialization,
			Message: "Block decode failed: " + err.Error(),
		}
	}
	block := btcutil.NewBlock(&msgBlock)

	// Ensure the block is building from the expected previous block.
	expectedPrevHash := s.cfg.Chain.BestSnapshot().Hash
	prevHash := &block.MsgBlock().Header.PrevBlock
	if !expectedPrevHash.IsEqual(prevHash) {
		return "bad-prevblk", nil
	}

	if err := s.cfg.Chain.CheckConnectBlockTemplate(block); err != nil {
		if _, ok := err.(blockchain.RuleError); !ok {
			errStr := fmt.Sprintf("Failed to process block proposal: %v", err)
			rpcsLog.Error(errStr)
			return nil, &btcjson.RPCError{
				Code:    btcjson.ErrRPCVerify,
				Message: errStr,
			}
		}

		rpcsLog.Infof("Rejected block proposal: %v", err)
		return chainErrToGBTErrString(err), nil
	}

	return nil, nil
}

// handleGetBlockTemplate implements the getblocktemplate command.
//
// See https://en.bitcoin.it/wiki/BIP_0022 and
// https://en.bitcoin.it/wiki/BIP_0023 for more details.
func handleGetBlockTemplate(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.GetBlockTemplateCmd)
	request := c.Request

	// Set the default mode and override it if supplied.
	mode := "template"
	if request != nil && request.Mode != "" {
		mode = request.Mode
	}

	switch mode {
	case "template":
		return handleGetBlockTemplateRequest(s, request, closeChan)
	case "proposal":
		return handleGetBlockTemplateProposal(s, request)
	}

	return nil, &btcjson.RPCError{
		Code:    btcjson.ErrRPCInvalidParameter,
		Message: "Invalid mode",
	}
}

// handleGetCFilter implements the getcfilter command.
func handleGetCFilter(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	if s.cfg.CfIndex == nil {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCNoCFIndex,
			Message: "The CF index must be enabled for this command",
		}
	}

	c := cmd.(*btcjson.GetCFilterCmd)
	hash, err := chainhash.NewHashFromStr(c.Hash)
	if err != nil {
		return nil, rpcDecodeHexError(c.Hash)
	}

	filterBytes, err := s.cfg.CfIndex.FilterByBlockHash(hash, c.FilterType)
	if err != nil {
		rpcsLog.Debugf("Could not find committed filter for %v: %v",
			hash, err)
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCBlockNotFound,
			Message: "Block not found",
		}
	}

	rpcsLog.Debugf("Found committed filter for %v", hash)
	return hex.EncodeToString(filterBytes), nil
}

// handleGetCFilterHeader implements the getcfilterheader command.
func handleGetCFilterHeader(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	if s.cfg.CfIndex == nil {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCNoCFIndex,
			Message: "The CF index must be enabled for this command",
		}
	}

	c := cmd.(*btcjson.GetCFilterHeaderCmd)
	hash, err := chainhash.NewHashFromStr(c.Hash)
	if err != nil {
		return nil, rpcDecodeHexError(c.Hash)
	}

	headerBytes, err := s.cfg.CfIndex.FilterHeaderByBlockHash(hash, c.FilterType)
	if len(headerBytes) > 0 {
		rpcsLog.Debugf("Found header of committed filter for %v", hash)
	} else {
		rpcsLog.Debugf("Could not find header of committed filter for %v: %v",
			hash, err)
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCBlockNotFound,
			Message: "Block not found",
		}
	}

	hash.SetBytes(headerBytes)
	return hash.String(), nil
}

// handleGetConnectionCount implements the getconnectioncount command.
func handleGetConnectionCount(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	return s.cfg.ConnMgr.ConnectedCount(), nil
}

// handleGetCurrentNet implements the getcurrentnet command.
func handleGetCurrentNet(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	return s.cfg.ChainParams.Net, nil
}

// handleGetDifficulty implements the getdifficulty command.
func handleGetDifficulty(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	best := s.cfg.Chain.BestSnapshot()
	return getDifficultyRatio(best.Bits, s.cfg.ChainParams), nil
}

// handleGetGenerate implements the getgenerate command.
func handleGetGenerate(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	return s.cfg.CPUMiner.IsMining(), nil
}

// handleGetHashesPerSec implements the gethashespersec command.
func handleGetHashesPerSec(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	return int64(s.cfg.CPUMiner.HashesPerSecond()), nil
}

// handleGetHeaders implements the getheaders command.
//
// NOTE: This is a btcsuite extension originally ported from
// github.com/decred/dcrd.
func handleGetHeaders(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.GetHeadersCmd)

	// Fetch the requested headers from chain while respecting the provided
	// block locators and stop hash.
	blockLocators := make([]*chainhash.Hash, len(c.BlockLocators))
	for i := range c.BlockLocators {
		blockLocator, err := chainhash.NewHashFromStr(c.BlockLocators[i])
		if err != nil {
			return nil, rpcDecodeHexError(c.BlockLocators[i])
		}
		blockLocators[i] = blockLocator
	}
	var hashStop chainhash.Hash
	if c.HashStop != "" {
		err := chainhash.Decode(&hashStop, c.HashStop)
		if err != nil {
			return nil, rpcDecodeHexError(c.HashStop)
		}
	}
	headers := s.cfg.SyncMgr.LocateHeaders(blockLocators, &hashStop)

	// Return the serialized block headers as hex-encoded strings.
	hexBlockHeaders := make([]string, len(headers))
	var buf bytes.Buffer
	for i, h := range headers {
		err := h.Serialize(&buf)
		if err != nil {
			return nil, internalRPCError(err.Error(),
				"Failed to serialize block header")
		}
		hexBlockHeaders[i] = hex.EncodeToString(buf.Bytes())
		buf.Reset()
	}
	return hexBlockHeaders, nil
}

// handleGetInfo implements the getinfo command. We only return the fields
// that are not related to wallet functionality.
func handleGetInfo(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	best := s.cfg.Chain.BestSnapshot()
	ret := &btcjson.InfoChainResult{
		Version:         int32(1000000*appMajor + 10000*appMinor + 100*appPatch),
		ProtocolVersion: int32(maxProtocolVersion),
		Blocks:          best.Height,
		TimeOffset:      int64(s.cfg.TimeSource.Offset().Seconds()),
		Connections:     s.cfg.ConnMgr.ConnectedCount(),
		Proxy:           cfg.Proxy,
		Difficulty:      getDifficultyRatio(best.Bits, s.cfg.ChainParams),
		TestNet:         cfg.TestNet3,
		RelayFee:        cfg.minRelayTxFee.ToBTC(),
	}

	return ret, nil
}

// handleGetMempoolInfo implements the getmempoolinfo command.
func handleGetMempoolInfo(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	mempoolTxns := s.cfg.TxMemPool.TxDescs()

	var numBytes int64
	for _, txD := range mempoolTxns {
		numBytes += int64(txD.Tx.MsgTx().SerializeSize())
	}

	ret := &btcjson.GetMempoolInfoResult{
		Size:  int64(len(mempoolTxns)),
		Bytes: numBytes,
	}

	return ret, nil
}

// handleGetMiningInfo implements the getmininginfo command. We only return the
// fields that are not related to wallet functionality.
func handleGetMiningInfo(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	// Create a default getnetworkhashps command to use defaults and make
	// use of the existing getnetworkhashps handler.
	gnhpsCmd := btcjson.NewGetNetworkHashPSCmd(nil, nil)
	networkHashesPerSecIface, err := handleGetNetworkHashPS(s, gnhpsCmd,
		closeChan)
	if err != nil {
		return nil, err
	}
	networkHashesPerSec, ok := networkHashesPerSecIface.(int64)
	if !ok {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCInternal.Code,
			Message: "networkHashesPerSec is not an int64",
		}
	}

	best := s.cfg.Chain.BestSnapshot()
	result := btcjson.GetMiningInfoResult{
		Blocks:             int64(best.Height),
		CurrentBlockSize:   best.BlockSize,
		CurrentBlockWeight: best.BlockWeight,
		CurrentBlockTx:     best.NumTxns,
		Difficulty:         getDifficultyRatio(best.Bits, s.cfg.ChainParams),
		Generate:           s.cfg.CPUMiner.IsMining(),
		GenProcLimit:       s.cfg.CPUMiner.NumWorkers(),
		HashesPerSec:       int64(s.cfg.CPUMiner.HashesPerSecond()),
		NetworkHashPS:      networkHashesPerSec,
		PooledTx:           uint64(s.cfg.TxMemPool.Count()),
		TestNet:            cfg.TestNet3,
	}
	return &result, nil
}

// handleGetNetTotals implements the getnettotals command.
func handleGetNetTotals(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	totalBytesRecv, totalBytesSent := s.cfg.ConnMgr.NetTotals()
	reply := &btcjson.GetNetTotalsResult{
		TotalBytesRecv: totalBytesRecv,
		TotalBytesSent: totalBytesSent,
		TimeMillis:     time.Now().UTC().UnixNano() / int64(time.Millisecond),
	}
	return reply, nil
}

// handleGetNetworkHashPS implements the getnetworkhashps command.
func handleGetNetworkHashPS(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	// Note: All valid error return paths should return an int64.
	// Literal zeros are inferred as int, and won't coerce to int64
	// because the return value is an interface{}.

	c := cmd.(*btcjson.GetNetworkHashPSCmd)

	// When the passed height is too high or zero, just return 0 now
	// since we can't reasonably calculate the number of network hashes
	// per second from invalid values.  When it's negative, use the current
	// best block height.
	best := s.cfg.Chain.BestSnapshot()
	endHeight := int32(-1)
	if c.Height != nil {
		endHeight = int32(*c.Height)
	}
	if endHeight > best.Height || endHeight == 0 {
		return int64(0), nil
	}
	if endHeight < 0 {
		endHeight = best.Height
	}

	// Calculate the number of blocks per retarget interval based on the
	// chain parameters.
	blocksPerRetarget := int32(s.cfg.ChainParams.TargetTimespan /
		s.cfg.ChainParams.TargetTimePerBlock)

	// Calculate the starting block height based on the passed number of
	// blocks.  When the passed value is negative, use the last block the
	// difficulty changed as the starting height.  Also make sure the
	// starting height is not before the beginning of the chain.
	numBlocks := int32(120)
	if c.Blocks != nil {
		numBlocks = int32(*c.Blocks)
	}
	var startHeight int32
	if numBlocks <= 0 {
		startHeight = endHeight - ((endHeight % blocksPerRetarget) + 1)
	} else {
		startHeight = endHeight - numBlocks
	}
	if startHeight < 0 {
		startHeight = 0
	}
	rpcsLog.Debugf("Calculating network hashes per second from %d to %d",
		startHeight, endHeight)

	// Find the min and max block timestamps as well as calculate the total
	// amount of work that happened between the start and end blocks.
	var minTimestamp, maxTimestamp time.Time
	totalWork := big.NewInt(0)
	for curHeight := startHeight; curHeight <= endHeight; curHeight++ {
		hash, err := s.cfg.Chain.BlockHashByHeight(curHeight)
		if err != nil {
			context := "Failed to fetch block hash"
			return nil, internalRPCError(err.Error(), context)
		}

		// Fetch the header from chain.
		header, err := s.cfg.Chain.HeaderByHash(hash)
		if err != nil {
			context := "Failed to fetch block header"
			return nil, internalRPCError(err.Error(), context)
		}

		if curHeight == startHeight {
			minTimestamp = header.Timestamp
			maxTimestamp = minTimestamp
		} else {
			totalWork.Add(totalWork, blockchain.CalcWork(header.Bits))

			if minTimestamp.After(header.Timestamp) {
				minTimestamp = header.Timestamp
			}
			if maxTimestamp.Before(header.Timestamp) {
				maxTimestamp = header.Timestamp
			}
		}
	}

	// Calculate the difference in seconds between the min and max block
	// timestamps and avoid division by zero in the case where there is no
	// time difference.
	timeDiff := int64(maxTimestamp.Sub(minTimestamp) / time.Second)
	if timeDiff == 0 {
		return int64(0), nil
	}

	hashesPerSec := new(big.Int).Div(totalWork, big.NewInt(timeDiff))
	return hashesPerSec.Int64(), nil
}

// handleGetPeerInfo implements the getpeerinfo command.
func handleGetPeerInfo(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	peers := s.cfg.ConnMgr.ConnectedPeers()
	syncPeerID := s.cfg.SyncMgr.SyncPeerID()
	infos := make([]*btcjson.GetPeerInfoResult, 0, len(peers))
	for _, p := range peers {
		statsSnap := p.ToPeer().StatsSnapshot()
		info := &btcjson.GetPeerInfoResult{
			ID:             statsSnap.ID,
			Addr:           statsSnap.Addr,
			AddrLocal:      p.ToPeer().LocalAddr().String(),
			Services:       fmt.Sprintf("%08d", uint64(statsSnap.Services)),
			RelayTxes:      !p.IsTxRelayDisabled(),
			LastSend:       statsSnap.LastSend.Unix(),
			LastRecv:       statsSnap.LastRecv.Unix(),
			BytesSent:      statsSnap.BytesSent,
			BytesRecv:      statsSnap.BytesRecv,
			ConnTime:       statsSnap.ConnTime.Unix(),
			PingTime:       float64(statsSnap.LastPingMicros),
			TimeOffset:     statsSnap.TimeOffset,
			Version:        statsSnap.Version,
			SubVer:         statsSnap.UserAgent,
			Inbound:        statsSnap.Inbound,
			StartingHeight: statsSnap.StartingHeight,
			CurrentHeight:  statsSnap.LastBlock,
			BanScore:       int32(p.BanScore()),
			FeeFilter:      p.FeeFilter(),
			SyncNode:       statsSnap.ID == syncPeerID,
		}
		if p.ToPeer().LastPingNonce() != 0 {
			wait := float64(time.Since(statsSnap.LastPingTime).Nanoseconds())
			// We actually want microseconds.
			info.PingWait = wait / 1000
		}
		infos = append(infos, info)
	}
	return infos, nil
}

// handleGetRawMempool implements the getrawmempool command.
func handleGetRawMempool(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.GetRawMempoolCmd)
	mp := s.cfg.TxMemPool

	if c.Verbose != nil && *c.Verbose {
		return mp.RawMempoolVerbose(), nil
	}

	// The response is simply an array of the transaction hashes if the
	// verbose flag is not set.
	descs := mp.TxDescs()
	hashStrings := make([]string, len(descs))
	for i := range hashStrings {
		hashStrings[i] = descs[i].Tx.Hash().String()
	}

	return hashStrings, nil
}

// handleGetRawTransaction implements the getrawtransaction command.
func handleGetRawTransaction(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.GetRawTransactionCmd)

	// Convert the provided transaction hash hex to a Hash.
	txHash, err := chainhash.NewHashFromStr(c.Txid)
	if err != nil {
		return nil, rpcDecodeHexError(c.Txid)
	}

	verbose := false
	if c.Verbose != nil {
		verbose = *c.Verbose != 0
	}

	// Try to fetch the transaction from the memory pool and if that fails,
	// try the block database.
	var mtx *wire.MsgTx
	var blkHash *chainhash.Hash
	var blkHeight int32
	tx, err := s.cfg.TxMemPool.FetchTransaction(txHash)
	if err != nil {
		if s.cfg.TxIndex == nil {
			return nil, &btcjson.RPCError{
				Code: btcjson.ErrRPCNoTxInfo,
				Message: "The transaction index must be " +
					"enabled to query the blockchain " +
					"(specify --txindex)",
			}
		}

		// Look up the location of the transaction.
		blockRegion, err := s.cfg.TxIndex.TxBlockRegion(txHash)
		if err != nil {
			context := "Failed to retrieve transaction location"
			return nil, internalRPCError(err.Error(), context)
		}
		if blockRegion == nil {
			return nil, rpcNoTxInfoError(txHash)
		}

		// Load the raw transaction bytes from the database.
		var txBytes []byte
		err = s.cfg.DB.View(func(dbTx database.Tx) error {
			var err error
			txBytes, err = dbTx.FetchBlockRegion(blockRegion)
			return err
		})
		if err != nil {
			return nil, rpcNoTxInfoError(txHash)
		}

		// When the verbose flag isn't set, simply return the serialized
		// transaction as a hex-encoded string.  This is done here to
		// avoid deserializing it only to reserialize it again later.
		if !verbose {
			return hex.EncodeToString(txBytes), nil
		}

		// Grab the block height.
		blkHash = blockRegion.Hash
		blkHeight, err = s.cfg.Chain.BlockHeightByHash(blkHash)
		if err != nil {
			context := "Failed to retrieve block height"
			return nil, internalRPCError(err.Error(), context)
		}

		// Deserialize the transaction
		var msgTx wire.MsgTx
		err = msgTx.Deserialize(bytes.NewReader(txBytes))
		if err != nil {
			context := "Failed to deserialize transaction"
			return nil, internalRPCError(err.Error(), context)
		}
		mtx = &msgTx
	} else {
		// When the verbose flag isn't set, simply return the
		// network-serialized transaction as a hex-encoded string.
		if !verbose {
			// Note that this is intentionally not directly
			// returning because the first return value is a
			// string and it would result in returning an empty
			// string to the client instead of nothing (nil) in the
			// case of an error.
			mtxHex, err := messageToHex(tx.MsgTx())
			if err != nil {
				return nil, err
			}
			return mtxHex, nil
		}

		mtx = tx.MsgTx()
	}

	// The verbose flag is set, so generate the JSON object and return it.
	var blkHeader *wire.BlockHeader
	var blkHashStr string
	var chainHeight int32
	if blkHash != nil {
		// Fetch the header from chain.
		header, err := s.cfg.Chain.HeaderByHash(blkHash)
		if err != nil {
			context := "Failed to fetch block header"
			return nil, internalRPCError(err.Error(), context)
		}

		blkHeader = &header
		blkHashStr = blkHash.String()
		chainHeight = s.cfg.Chain.BestSnapshot().Height
	}

	rawTxn, err := createTxRawResult(s.cfg.ChainParams, mtx, txHash.String(),
		blkHeader, blkHashStr, blkHeight, chainHeight)
	if err != nil {
		return nil, err
	}
	return *rawTxn, nil
}

// handleGetTxOut handles gettxout commands.
func handleGetTxOut(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.GetTxOutCmd)

	// Convert the provided transaction hash hex to a Hash.
	txHash, err := chainhash.NewHashFromStr(c.Txid)
	if err != nil {
		return nil, rpcDecodeHexError(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 bestBlockHash string
	var confirmations int32
	var value int64
	var pkScript []byte
	var isCoinbase bool
	includeMempool := true
	if c.IncludeMempool != nil {
		includeMempool = *c.IncludeMempool
	}
	// TODO: This is racy.  It should attempt to fetch it directly and check
	// the error.
	if includeMempool && s.cfg.TxMemPool.HaveTransaction(txHash) {
		tx, err := s.cfg.TxMemPool.FetchTransaction(txHash)
		if err != nil {
			return nil, rpcNoTxInfoError(txHash)
		}

		mtx := tx.MsgTx()
		if c.Vout > uint32(len(mtx.TxOut)-1) {
			return nil, &btcjson.RPCError{
				Code: btcjson.ErrRPCInvalidTxVout,
				Message: "Output index number (vout) does not " +
					"exist for transaction.",
			}
		}

		txOut := mtx.TxOut[c.Vout]
		if txOut == nil {
			errStr := fmt.Sprintf("Output index: %d for txid: %s "+
				"does not exist", c.Vout, txHash)
			return nil, internalRPCError(errStr, "")
		}

		best := s.cfg.Chain.BestSnapshot()
		bestBlockHash = best.Hash.String()
		confirmations = 0
		value = txOut.Value
		pkScript = txOut.PkScript
		isCoinbase = blockchain.IsCoinBaseTx(mtx)
	} else {
		out := wire.OutPoint{Hash: *txHash, Index: c.Vout}
		entry, err := s.cfg.Chain.FetchUtxoEntry(out)
		if err != nil {
			return nil, rpcNoTxInfoError(txHash)
		}

		// To match the behavior of the reference client, return nil
		// (JSON null) if the transaction output is spent by another
		// transaction already in the main chain.  Mined transactions
		// that are spent by a mempool transaction are not affected by
		// this.
		if entry == nil || entry.IsSpent() {
			return nil, nil
		}

		best := s.cfg.Chain.BestSnapshot()
		bestBlockHash = best.Hash.String()
		confirmations = 1 + best.Height - entry.BlockHeight()
		value = entry.Amount()
		pkScript = entry.PkScript()
		isCoinbase = entry.IsCoinBase()
	}

	// 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.
	disbuf, _ := txscript.DisasmString(pkScript)

	// 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.
	scriptClass, addrs, reqSigs, _ := txscript.ExtractPkScriptAddrs(pkScript,
		s.cfg.ChainParams)
	addresses := make([]string, len(addrs))
	for i, addr := range addrs {
		addresses[i] = addr.EncodeAddress()
	}

	txOutReply := &btcjson.GetTxOutResult{
		BestBlock:     bestBlockHash,
		Confirmations: int64(confirmations),
		Value:         btcutil.Amount(value).ToBTC(),
		ScriptPubKey: btcjson.ScriptPubKeyResult{
			Asm:       disbuf,
			Hex:       hex.EncodeToString(pkScript),
			ReqSigs:   int32(reqSigs),
			Type:      scriptClass.String(),
			Addresses: addresses,
		},
		Coinbase: isCoinbase,
	}
	return txOutReply, nil
}

// handleHelp implements the help command.
func handleHelp(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.HelpCmd)

	// Provide a usage overview of all commands when no specific command
	// was specified.
	var command string
	if c.Command != nil {
		command = *c.Command
	}
	if command == "" {
		usage, err := s.helpCacher.rpcUsage(false)
		if err != nil {
			context := "Failed to generate RPC usage"
			return nil, internalRPCError(err.Error(), context)
		}
		return usage, nil
	}

	// Check that the command asked for is supported and implemented.  Only
	// search the main list of handlers since help should not be provided
	// for commands that are unimplemented or related to wallet
	// functionality.
	if _, ok := rpcHandlers[command]; !ok {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCInvalidParameter,
			Message: "Unknown command: " + command,
		}
	}

	// Get the help for the command.
	help, err := s.helpCacher.rpcMethodHelp(command)
	if err != nil {
		context := "Failed to generate help"
		return nil, internalRPCError(err.Error(), context)
	}
	return help, nil
}

// handlePing implements the ping command.
func handlePing(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	// Ask server to ping \o_
	nonce, err := wire.RandomUint64()
	if err != nil {
		return nil, internalRPCError("Not sending ping - failed to "+
			"generate nonce: "+err.Error(), "")
	}
	s.cfg.ConnMgr.BroadcastMessage(wire.NewMsgPing(nonce))

	return nil, nil
}

// retrievedTx represents a transaction that was either loaded from the
// transaction memory pool or from the database.  When a transaction is loaded
// from the database, it is loaded with the raw serialized bytes while the
// mempool has the fully deserialized structure.  This structure therefore will
// have one of the two fields set depending on where is was retrieved from.
// This is mainly done for efficiency to avoid extra serialization steps when
// possible.
type retrievedTx struct {
	txBytes []byte
	blkHash *chainhash.Hash // Only set when transaction is in a block.
	tx      *btcutil.Tx
}

// fetchInputTxos fetches the outpoints from all transactions referenced by the
// inputs to the passed transaction by checking the transaction mempool first
// then the transaction index for those already mined into blocks.
func fetchInputTxos(s *rpcServer, tx *wire.MsgTx) (map[wire.OutPoint]wire.TxOut, error) {
	mp := s.cfg.TxMemPool
	originOutputs := make(map[wire.OutPoint]wire.TxOut)
	for txInIndex, txIn := range tx.TxIn {
		// Attempt to fetch and use the referenced transaction from the
		// memory pool.
		origin := &txIn.PreviousOutPoint
		originTx, err := mp.FetchTransaction(&origin.Hash)
		if err == nil {
			txOuts := originTx.MsgTx().TxOut
			if origin.Index >= uint32(len(txOuts)) {
				errStr := fmt.Sprintf("unable to find output "+
					"%v referenced from transaction %s:%d",
					origin, tx.TxHash(), txInIndex)
				return nil, internalRPCError(errStr, "")
			}

			originOutputs[*origin] = *txOuts[origin.Index]
			continue
		}

		// Look up the location of the transaction.
		blockRegion, err := s.cfg.TxIndex.TxBlockRegion(&origin.Hash)
		if err != nil {
			context := "Failed to retrieve transaction location"
			return nil, internalRPCError(err.Error(), context)
		}
		if blockRegion == nil {
			return nil, rpcNoTxInfoError(&origin.Hash)
		}

		// Load the raw transaction bytes from the database.
		var txBytes []byte
		err = s.cfg.DB.View(func(dbTx database.Tx) error {
			var err error
			txBytes, err = dbTx.FetchBlockRegion(blockRegion)
			return err
		})
		if err != nil {
			return nil, rpcNoTxInfoError(&origin.Hash)
		}

		// Deserialize the transaction
		var msgTx wire.MsgTx
		err = msgTx.Deserialize(bytes.NewReader(txBytes))
		if err != nil {
			context := "Failed to deserialize transaction"
			return nil, internalRPCError(err.Error(), context)
		}

		// Add the referenced output to the map.
		if origin.Index >= uint32(len(msgTx.TxOut)) {
			errStr := fmt.Sprintf("unable to find output %v "+
				"referenced from transaction %s:%d", origin,
				tx.TxHash(), txInIndex)
			return nil, internalRPCError(errStr, "")
		}
		originOutputs[*origin] = *msgTx.TxOut[origin.Index]
	}

	return originOutputs, nil
}

// createVinListPrevOut returns a slice of JSON objects for the inputs of the
// passed transaction.
func createVinListPrevOut(s *rpcServer, mtx *wire.MsgTx, chainParams *chaincfg.Params, vinExtra bool, filterAddrMap map[string]struct{}) ([]btcjson.VinPrevOut, error) {
	// Coinbase transactions only have a single txin by definition.
	if blockchain.IsCoinBaseTx(mtx) {
		// Only include the transaction if the filter map is empty
		// because a coinbase input has no addresses and so would never
		// match a non-empty filter.
		if len(filterAddrMap) != 0 {
			return nil, nil
		}

		txIn := mtx.TxIn[0]
		vinList := make([]btcjson.VinPrevOut, 1)
		vinList[0].Coinbase = hex.EncodeToString(txIn.SignatureScript)
		vinList[0].Sequence = txIn.Sequence
		return vinList, nil
	}

	// Use a dynamically sized list to accommodate the address filter.
	vinList := make([]btcjson.VinPrevOut, 0, len(mtx.TxIn))

	// Lookup all of the referenced transaction outputs needed to populate
	// the previous output information if requested.
	var originOutputs map[wire.OutPoint]wire.TxOut
	if vinExtra || len(filterAddrMap) > 0 {
		var err error
		originOutputs, err = fetchInputTxos(s, mtx)
		if err != nil {
			return nil, err
		}
	}

	for _, txIn := range mtx.TxIn {
		// The disassembled string will contain [error] inline
		// if the script doesn't fully parse, so ignore the
		// error here.
		disbuf, _ := txscript.DisasmString(txIn.SignatureScript)

		// Create the basic input entry without the additional optional
		// previous output details which will be added later if
		// requested and available.
		prevOut := &txIn.PreviousOutPoint
		vinEntry := btcjson.VinPrevOut{
			Txid:     prevOut.Hash.String(),
			Vout:     prevOut.Index,
			Sequence: txIn.Sequence,
			ScriptSig: &btcjson.ScriptSig{
				Asm: disbuf,
				Hex: hex.EncodeToString(txIn.SignatureScript),
			},
		}

		if len(txIn.Witness) != 0 {
			vinEntry.Witness = witnessToHex(txIn.Witness)
		}

		// Add the entry to the list now if it already passed the filter
		// since the previous output might not be available.
		passesFilter := len(filterAddrMap) == 0
		if passesFilter {
			vinList = append(vinList, vinEntry)
		}

		// Only populate previous output information if requested and
		// available.
		if len(originOutputs) == 0 {
			continue
		}
		originTxOut, ok := originOutputs[*prevOut]
		if !ok {
			continue
		}

		// Ignore the error here since an error means the script
		// couldn't parse and there is no additional information about
		// it anyways.
		_, addrs, _, _ := txscript.ExtractPkScriptAddrs(
			originTxOut.PkScript, chainParams)

		// Encode the addresses while checking if the address passes the
		// filter when needed.
		encodedAddrs := make([]string, len(addrs))
		for j, addr := range addrs {
			encodedAddr := addr.EncodeAddress()
			encodedAddrs[j] = encodedAddr

			// No need to check the map again if the filter already
			// passes.
			if passesFilter {
				continue
			}
			if _, exists := filterAddrMap[encodedAddr]; exists {
				passesFilter = true
			}
		}

		// Ignore the entry if it doesn't pass the filter.
		if !passesFilter {
			continue
		}

		// Add entry to the list if it wasn't already done above.
		if len(filterAddrMap) != 0 {
			vinList = append(vinList, vinEntry)
		}

		// Update the entry with previous output information if
		// requested.
		if vinExtra {
			vinListEntry := &vinList[len(vinList)-1]
			vinListEntry.PrevOut = &btcjson.PrevOut{
				Addresses: encodedAddrs,
				Value:     btcutil.Amount(originTxOut.Value).ToBTC(),
			}
		}
	}

	return vinList, nil
}

// fetchMempoolTxnsForAddress queries the address index for all unconfirmed
// transactions that involve the provided address.  The results will be limited
// by the number to skip and the number requested.
func fetchMempoolTxnsForAddress(s *rpcServer, addr btcutil.Address, numToSkip, numRequested uint32) ([]*btcutil.Tx, uint32) {
	// There are no entries to return when there are less available than the
	// number being skipped.
	mpTxns := s.cfg.AddrIndex.UnconfirmedTxnsForAddress(addr)
	numAvailable := uint32(len(mpTxns))
	if numToSkip > numAvailable {
		return nil, numAvailable
	}

	// Filter the available entries based on the number to skip and number
	// requested.
	rangeEnd := numToSkip + numRequested
	if rangeEnd > numAvailable {
		rangeEnd = numAvailable
	}
	return mpTxns[numToSkip:rangeEnd], numToSkip
}

// handleSearchRawTransactions implements the searchrawtransactions command.
func handleSearchRawTransactions(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	// Respond with an error if the address index is not enabled.
	addrIndex := s.cfg.AddrIndex
	if addrIndex == nil {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCMisc,
			Message: "Address index must be enabled (--addrindex)",
		}
	}

	// Override the flag for including extra previous output information in
	// each input if needed.
	c := cmd.(*btcjson.SearchRawTransactionsCmd)
	vinExtra := false
	if c.VinExtra != nil {
		vinExtra = *c.VinExtra != 0
	}

	// Including the extra previous output information requires the
	// transaction index.  Currently the address index relies on the
	// transaction index, so this check is redundant, but it's better to be
	// safe in case the address index is ever changed to not rely on it.
	if vinExtra && s.cfg.TxIndex == nil {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCMisc,
			Message: "Transaction index must be enabled (--txindex)",
		}
	}

	// Attempt to decode the supplied address.
	params := s.cfg.ChainParams
	addr, err := btcutil.DecodeAddress(c.Address, params)
	if err != nil {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCInvalidAddressOrKey,
			Message: "Invalid address or key: " + err.Error(),
		}
	}

	// Override the default number of requested entries if needed.  Also,
	// just return now if the number of requested entries is zero to avoid
	// extra work.
	numRequested := 100
	if c.Count != nil {
		numRequested = *c.Count
		if numRequested < 0 {
			numRequested = 1
		}
	}
	if numRequested == 0 {
		return nil, nil
	}

	// Override the default number of entries to skip if needed.
	var numToSkip int
	if c.Skip != nil {
		numToSkip = *c.Skip
		if numToSkip < 0 {
			numToSkip = 0
		}
	}

	// Override the reverse flag if needed.
	var reverse bool
	if c.Reverse != nil {
		reverse = *c.Reverse
	}

	// Add transactions from mempool first if client asked for reverse
	// order.  Otherwise, they will be added last (as needed depending on
	// the requested counts).
	//
	// NOTE: This code doesn't sort by dependency.  This might be something
	// to do in the future for the client's convenience, or leave it to the
	// client.
	numSkipped := uint32(0)
	addressTxns := make([]retrievedTx, 0, numRequested)
	if reverse {
		// Transactions in the mempool are not in a block header yet,
		// so the block header field in the retieved transaction struct
		// is left nil.
		mpTxns, mpSkipped := fetchMempoolTxnsForAddress(s, addr,
			uint32(numToSkip), uint32(numRequested))
		numSkipped += mpSkipped
		for _, tx := range mpTxns {
			addressTxns = append(addressTxns, retrievedTx{tx: tx})
		}
	}

	// Fetch transactions from the database in the desired order if more are
	// needed.
	if len(addressTxns) < numRequested {
		err = s.cfg.DB.View(func(dbTx database.Tx) error {
			regions, dbSkipped, err := addrIndex.TxRegionsForAddress(
				dbTx, addr, uint32(numToSkip)-numSkipped,
				uint32(numRequested-len(addressTxns)), reverse)
			if err != nil {
				return err
			}

			// Load the raw transaction bytes from the database.
			serializedTxns, err := dbTx.FetchBlockRegions(regions)
			if err != nil {
				return err
			}

			// Add the transaction and the hash of the block it is
			// contained in to the list.  Note that the transaction
			// is left serialized here since the caller might have
			// requested non-verbose output and hence there would be
			// no point in deserializing it just to reserialize it
			// later.
			for i, serializedTx := range serializedTxns {
				addressTxns = append(addressTxns, retrievedTx{
					txBytes: serializedTx,
					blkHash: regions[i].Hash,
				})
			}
			numSkipped += dbSkipped

			return nil
		})
		if err != nil {
			context := "Failed to load address index entries"
			return nil, internalRPCError(err.Error(), context)
		}

	}

	// Add transactions from mempool last if client did not request reverse
	// order and the number of results is still under the number requested.
	if !reverse && len(addressTxns) < numRequested {
		// Transactions in the mempool are not in a block header yet,
		// so the block header field in the retieved transaction struct
		// is left nil.
		mpTxns, mpSkipped := fetchMempoolTxnsForAddress(s, addr,
			uint32(numToSkip)-numSkipped, uint32(numRequested-
				len(addressTxns)))
		numSkipped += mpSkipped
		for _, tx := range mpTxns {
			addressTxns = append(addressTxns, retrievedTx{tx: tx})
		}
	}

	// Address has never been used if neither source yielded any results.
	if len(addressTxns) == 0 {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCNoTxInfo,
			Message: "No information available about address",
		}
	}

	// Serialize all of the transactions to hex.
	hexTxns := make([]string, len(addressTxns))
	for i := range addressTxns {
		// Simply encode the raw bytes to hex when the retrieved
		// transaction is already in serialized form.
		rtx := &addressTxns[i]
		if rtx.txBytes != nil {
			hexTxns[i] = hex.EncodeToString(rtx.txBytes)
			continue
		}

		// Serialize the transaction first and convert to hex when the
		// retrieved transaction is the deserialized structure.
		hexTxns[i], err = messageToHex(rtx.tx.MsgTx())
		if err != nil {
			return nil, err
		}
	}

	// When not in verbose mode, simply return a list of serialized txns.
	if c.Verbose != nil && *c.Verbose == 0 {
		return hexTxns, nil
	}

	// Normalize the provided filter addresses (if any) to ensure there are
	// no duplicates.
	filterAddrMap := make(map[string]struct{})
	if c.FilterAddrs != nil && len(*c.FilterAddrs) > 0 {
		for _, addr := range *c.FilterAddrs {
			filterAddrMap[addr] = struct{}{}
		}
	}

	// The verbose flag is set, so generate the JSON object and return it.
	best := s.cfg.Chain.BestSnapshot()
	srtList := make([]btcjson.SearchRawTransactionsResult, len(addressTxns))
	for i := range addressTxns {
		// The deserialized transaction is needed, so deserialize the
		// retrieved transaction if it's in serialized form (which will
		// be the case when it was lookup up from the database).
		// Otherwise, use the existing deserialized transaction.
		rtx := &addressTxns[i]
		var mtx *wire.MsgTx
		if rtx.tx == nil {
			// Deserialize the transaction.
			mtx = new(wire.MsgTx)
			err := mtx.Deserialize(bytes.NewReader(rtx.txBytes))
			if err != nil {
				context := "Failed to deserialize transaction"
				return nil, internalRPCError(err.Error(),
					context)
			}
		} else {
			mtx = rtx.tx.MsgTx()
		}

		result := &srtList[i]
		result.Hex = hexTxns[i]
		result.Txid = mtx.TxHash().String()
		result.Vin, err = createVinListPrevOut(s, mtx, params, vinExtra,
			filterAddrMap)
		if err != nil {
			return nil, err
		}
		result.Vout = createVoutList(mtx, params, filterAddrMap)
		result.Version = mtx.Version
		result.LockTime = mtx.LockTime

		// Transactions grabbed from the mempool aren't yet in a block,
		// so conditionally fetch block details here.  This will be
		// reflected in the final JSON output (mempool won't have
		// confirmations or block information).
		var blkHeader *wire.BlockHeader
		var blkHashStr string
		var blkHeight int32
		if blkHash := rtx.blkHash; blkHash != nil {
			// Fetch the header from chain.
			header, err := s.cfg.Chain.HeaderByHash(blkHash)
			if err != nil {
				return nil, &btcjson.RPCError{
					Code:    btcjson.ErrRPCBlockNotFound,
					Message: "Block not found",
				}
			}

			// Get the block height from chain.
			height, err := s.cfg.Chain.BlockHeightByHash(blkHash)
			if err != nil {
				context := "Failed to obtain block height"
				return nil, internalRPCError(err.Error(), context)
			}

			blkHeader = &header
			blkHashStr = blkHash.String()
			blkHeight = height
		}

		// Add the block information to the result if there is any.
		if blkHeader != nil {
			// This is not a typo, they are identical in Bitcoin
			// Core as well.
			result.Time = blkHeader.Timestamp.Unix()
			result.Blocktime = blkHeader.Timestamp.Unix()
			result.BlockHash = blkHashStr
			result.Confirmations = uint64(1 + best.Height - blkHeight)
		}
	}

	return srtList, nil
}

// handleSendRawTransaction implements the sendrawtransaction command.
func handleSendRawTransaction(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.SendRawTransactionCmd)
	// Deserialize and send off to tx relay
	hexStr := c.HexTx
	if len(hexStr)%2 != 0 {
		hexStr = "0" + hexStr
	}
	serializedTx, err := hex.DecodeString(hexStr)
	if err != nil {
		return nil, rpcDecodeHexError(hexStr)
	}
	var msgTx wire.MsgTx
	err = msgTx.Deserialize(bytes.NewReader(serializedTx))
	if err != nil {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCDeserialization,
			Message: "TX decode failed: " + err.Error(),
		}
	}

	// Use 0 for the tag to represent local node.
	tx := btcutil.NewTx(&msgTx)
	acceptedTxs, err := s.cfg.TxMemPool.ProcessTransaction(tx, false, false, 0)
	if err != nil {
		// When the error is a rule error, it means the transaction was
		// simply rejected as opposed to something actually going wrong,
		// so log it as such.  Otherwise, something really did go wrong,
		// so log it as an actual error.  In both cases, a JSON-RPC
		// error is returned to the client with the deserialization
		// error code (to match bitcoind behavior).
		if _, ok := err.(mempool.RuleError); ok {
			rpcsLog.Debugf("Rejected transaction %v: %v", tx.Hash(),
				err)
		} else {
			rpcsLog.Errorf("Failed to process transaction %v: %v",
				tx.Hash(), err)
		}
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCDeserialization,
			Message: "TX rejected: " + err.Error(),
		}
	}

	// When the transaction was accepted it should be the first item in the
	// returned array of accepted transactions.  The only way this will not
	// be true is if the API for ProcessTransaction changes and this code is
	// not properly updated, but ensure the condition holds as a safeguard.
	//
	// Also, since an error is being returned to the caller, ensure the
	// transaction is removed from the memory pool.
	if len(acceptedTxs) == 0 || !acceptedTxs[0].Tx.Hash().IsEqual(tx.Hash()) {
		s.cfg.TxMemPool.RemoveTransaction(tx, true)

		errStr := fmt.Sprintf("transaction %v is not in accepted list",
			tx.Hash())
		return nil, internalRPCError(errStr, "")
	}

	// Generate and relay inventory vectors for all newly accepted
	// transactions into the memory pool due to the original being
	// accepted.
	s.cfg.ConnMgr.RelayTransactions(acceptedTxs)

	// Notify both websocket and getblocktemplate long poll clients of all
	// newly accepted transactions.
	s.NotifyNewTransactions(acceptedTxs)

	// Keep track of all the sendrawtransaction request txns so that they
	// can be rebroadcast if they don't make their way into a block.
	txD := acceptedTxs[0]
	iv := wire.NewInvVect(wire.InvTypeTx, txD.Tx.Hash())
	s.cfg.ConnMgr.AddRebroadcastInventory(iv, txD)

	return tx.Hash().String(), nil
}

// handleSetGenerate implements the setgenerate command.
func handleSetGenerate(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.SetGenerateCmd)

	// Disable generation regardless of the provided generate flag if the
	// maximum number of threads (goroutines for our purposes) is 0.
	// Otherwise enable or disable it depending on the provided flag.
	generate := c.Generate
	genProcLimit := -1
	if c.GenProcLimit != nil {
		genProcLimit = *c.GenProcLimit
	}
	if genProcLimit == 0 {
		generate = false
	}

	if !generate {
		s.cfg.CPUMiner.Stop()
	} else {
		// Respond with an error if there are no addresses to pay the
		// created blocks to.
		if len(cfg.miningAddrs) == 0 {
			return nil, &btcjson.RPCError{
				Code: btcjson.ErrRPCInternal.Code,
				Message: "No payment addresses specified " +
					"via --miningaddr",
			}
		}

		// It's safe to call start even if it's already started.
		s.cfg.CPUMiner.SetNumWorkers(int32(genProcLimit))
		s.cfg.CPUMiner.Start()
	}
	return nil, nil
}

// handleStop implements the stop command.
func handleStop(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	select {
	case s.requestProcessShutdown <- struct{}{}:
	default:
	}
	return "btcd stopping.", nil
}

// handleSubmitBlock implements the submitblock command.
func handleSubmitBlock(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.SubmitBlockCmd)

	// Deserialize the submitted block.
	hexStr := c.HexBlock
	if len(hexStr)%2 != 0 {
		hexStr = "0" + c.HexBlock
	}
	serializedBlock, err := hex.DecodeString(hexStr)
	if err != nil {
		return nil, rpcDecodeHexError(hexStr)
	}

	block, err := btcutil.NewBlockFromBytes(serializedBlock)
	if err != nil {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCDeserialization,
			Message: "Block decode failed: " + err.Error(),
		}
	}

	// Process this block using the same rules as blocks coming from other
	// nodes.  This will in turn relay it to the network like normal.
	_, err = s.cfg.SyncMgr.SubmitBlock(block, blockchain.BFNone)
	if err != nil {
		return fmt.Sprintf("rejected: %s", err.Error()), nil
	}

	rpcsLog.Infof("Accepted block %s via submitblock", block.Hash())
	return nil, nil
}

// handleUptime implements the uptime command.
func handleUptime(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	return time.Now().Unix() - s.cfg.StartupTime, nil
}

// handleValidateAddress implements the validateaddress command.
func handleValidateAddress(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.ValidateAddressCmd)

	result := btcjson.ValidateAddressChainResult{}
	addr, err := btcutil.DecodeAddress(c.Address, s.cfg.ChainParams)
	if err != nil {
		// Return the default value (false) for IsValid.
		return result, nil
	}

	result.Address = addr.EncodeAddress()
	result.IsValid = true

	return result, nil
}

func verifyChain(s *rpcServer, level, depth int32) error {
	best := s.cfg.Chain.BestSnapshot()
	finishHeight := best.Height - depth
	if finishHeight < 0 {
		finishHeight = 0
	}
	rpcsLog.Infof("Verifying chain for %d blocks at level %d",
		best.Height-finishHeight, level)

	for height := best.Height; height > finishHeight; height-- {
		// Level 0 just looks up the block.
		block, err := s.cfg.Chain.BlockByHeight(height)
		if err != nil {
			rpcsLog.Errorf("Verify is unable to fetch block at "+
				"height %d: %v", height, err)
			return err
		}

		// Level 1 does basic chain sanity checks.
		if level > 0 {
			err := blockchain.CheckBlockSanity(block,
				s.cfg.ChainParams.PowLimit, s.cfg.TimeSource)
			if err != nil {
				rpcsLog.Errorf("Verify is unable to validate "+
					"block at hash %v height %d: %v",
					block.Hash(), height, err)
				return err
			}
		}
	}
	rpcsLog.Infof("Chain verify completed successfully")

	return nil
}

// handleVerifyChain implements the verifychain command.
func handleVerifyChain(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.VerifyChainCmd)

	var checkLevel, checkDepth int32
	if c.CheckLevel != nil {
		checkLevel = *c.CheckLevel
	}
	if c.CheckDepth != nil {
		checkDepth = *c.CheckDepth
	}

	err := verifyChain(s, checkLevel, checkDepth)
	return err == nil, nil
}

// handleVerifyMessage implements the verifymessage command.
func handleVerifyMessage(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	c := cmd.(*btcjson.VerifyMessageCmd)

	// Decode the provided address.
	params := s.cfg.ChainParams
	addr, err := btcutil.DecodeAddress(c.Address, params)
	if err != nil {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCInvalidAddressOrKey,
			Message: "Invalid address or key: " + err.Error(),
		}
	}

	// Only P2PKH addresses are valid for signing.
	if _, ok := addr.(*btcutil.AddressPubKeyHash); !ok {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCType,
			Message: "Address is not a pay-to-pubkey-hash address",
		}
	}

	// Decode base64 signature.
	sig, err := base64.StdEncoding.DecodeString(c.Signature)
	if err != nil {
		return nil, &btcjson.RPCError{
			Code:    btcjson.ErrRPCParse.Code,
			Message: "Malformed base64 encoding: " + err.Error(),
		}
	}

	// Validate the signature - this just shows that it was valid at all.
	// we will compare it with the key next.
	var buf bytes.Buffer
	wire.WriteVarString(&buf, 0, "Bitcoin Signed Message:\n")
	wire.WriteVarString(&buf, 0, c.Message)
	expectedMessageHash := chainhash.DoubleHashB(buf.Bytes())
	pk, wasCompressed, err := btcec.RecoverCompact(btcec.S256(), sig,
		expectedMessageHash)
	if err != nil {
		// Mirror Bitcoin Core behavior, which treats error in
		// RecoverCompact as invalid signature.
		return false, nil
	}

	// Reconstruct the pubkey hash.
	var serializedPK []byte
	if wasCompressed {
		serializedPK = pk.SerializeCompressed()
	} else {
		serializedPK = pk.SerializeUncompressed()
	}
	address, err := btcutil.NewAddressPubKey(serializedPK, params)
	if err != nil {
		// Again mirror Bitcoin Core behavior, which treats error in public key
		// reconstruction as invalid signature.
		return false, nil
	}

	// Return boolean if addresses match.
	return address.EncodeAddress() == c.Address, nil
}

// handleVersion implements the version command.
//
// NOTE: This is a btcsuite extension ported from github.com/decred/dcrd.
func handleVersion(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	result := map[string]btcjson.VersionResult{
		"btcdjsonrpcapi": {
			VersionString: jsonrpcSemverString,
			Major:         jsonrpcSemverMajor,
			Minor:         jsonrpcSemverMinor,
			Patch:         jsonrpcSemverPatch,
		},
	}
	return result, nil
}

// rpcServer provides a concurrent safe RPC server to a chain server.
type rpcServer struct {
	started                int32
	shutdown               int32
	cfg                    rpcserverConfig
	authsha                [sha256.Size]byte
	limitauthsha           [sha256.Size]byte
	ntfnMgr                *wsNotificationManager
	numClients             int32
	statusLines            map[int]string
	statusLock             sync.RWMutex
	wg                     sync.WaitGroup
	gbtWorkState           *gbtWorkState
	helpCacher             *helpCacher
	requestProcessShutdown chan struct{}
	quit                   chan int
}

// httpStatusLine returns a response Status-Line (RFC 2616 Section 6.1)
// for the given request and response status code.  This function was lifted and
// adapted from the standard library HTTP server code since it's not exported.
func (s *rpcServer) httpStatusLine(req *http.Request, code int) string {
	// Fast path:
	key := code
	proto11 := req.ProtoAtLeast(1, 1)
	if !proto11 {
		key = -key
	}
	s.statusLock.RLock()
	line, ok := s.statusLines[key]
	s.statusLock.RUnlock()
	if ok {
		return line
	}

	// Slow path:
	proto := "HTTP/1.0"
	if proto11 {
		proto = "HTTP/1.1"
	}
	codeStr := strconv.Itoa(code)
	text := http.StatusText(code)
	if text != "" {
		line = proto + " " + codeStr + " " + text + "\r\n"
		s.statusLock.Lock()
		s.statusLines[key] = line
		s.statusLock.Unlock()
	} else {
		text = "status code " + codeStr
		line = proto + " " + codeStr + " " + text + "\r\n"
	}

	return line
}

// writeHTTPResponseHeaders writes the necessary response headers prior to
// writing an HTTP body given a request to use for protocol negotiation, headers
// to write, a status code, and a writer.
func (s *rpcServer) writeHTTPResponseHeaders(req *http.Request, headers http.Header, code int, w io.Writer) error {
	_, err := io.WriteString(w, s.httpStatusLine(req, code))
	if err != nil {
		return err
	}

	err = headers.Write(w)
	if err != nil {
		return err
	}

	_, err = io.WriteString(w, "\r\n")
	return err
}

// Stop is used by server.go to stop the rpc listener.
func (s *rpcServer) Stop() error {
	if atomic.AddInt32(&s.shutdown, 1) != 1 {
		rpcsLog.Infof("RPC server is already in the process of shutting down")
		return nil
	}
	rpcsLog.Warnf("RPC server shutting down")
	for _, listener := range s.cfg.Listeners {
		err := listener.Close()
		if err != nil {
			rpcsLog.Errorf("Problem shutting down rpc: %v", err)
			return err
		}
	}
	s.ntfnMgr.Shutdown()
	s.ntfnMgr.WaitForShutdown()
	close(s.quit)
	s.wg.Wait()
	rpcsLog.Infof("RPC server shutdown complete")
	return nil
}

// RequestedProcessShutdown returns a channel that is sent to when an authorized
// RPC client requests the process to shutdown.  If the request can not be read
// immediately, it is dropped.
func (s *rpcServer) RequestedProcessShutdown() <-chan struct{} {
	return s.requestProcessShutdown
}

// NotifyNewTransactions notifies both websocket and getblocktemplate long
// poll clients of the passed transactions.  This function should be called
// whenever new transactions are added to the mempool.
func (s *rpcServer) NotifyNewTransactions(txns []*mempool.TxDesc) {
	for _, txD := range txns {
		// Notify websocket clients about mempool transactions.
		s.ntfnMgr.NotifyMempoolTx(txD.Tx, true)

		// Potentially notify any getblocktemplate long poll clients
		// about stale block templates due to the new transaction.
		s.gbtWorkState.NotifyMempoolTx(s.cfg.TxMemPool.LastUpdated())
	}
}

// limitConnections responds with a 503 service unavailable and returns true if
// adding another client would exceed the maximum allow RPC clients.
//
// This function is safe for concurrent access.
func (s *rpcServer) limitConnections(w http.ResponseWriter, remoteAddr string) bool {
	if int(atomic.LoadInt32(&s.numClients)+1) > cfg.RPCMaxClients {
		rpcsLog.Infof("Max RPC clients exceeded [%d] - "+
			"disconnecting client %s", cfg.RPCMaxClients,
			remoteAddr)
		http.Error(w, "503 Too busy.  Try again later.",
			http.StatusServiceUnavailable)
		return true
	}
	return false
}

// incrementClients adds one to the number of connected RPC clients.  Note
// this only applies to standard clients.  Websocket clients have their own
// limits and are tracked separately.
//
// This function is safe for concurrent access.
func (s *rpcServer) incrementClients() {
	atomic.AddInt32(&s.numClients, 1)
}

// decrementClients subtracts one from the number of connected RPC clients.
// Note this only applies to standard clients.  Websocket clients have their own
// limits and are tracked separately.
//
// This function is safe for concurrent access.
func (s *rpcServer) decrementClients() {
	atomic.AddInt32(&s.numClients, -1)
}

// checkAuth checks the HTTP Basic authentication supplied by a wallet
// or RPC client in the HTTP request r.  If the supplied authentication
// does not match the username and password expected, a non-nil error is
// returned.
//
// This check is time-constant.
//
// The first bool return value signifies auth success (true if successful) and
// the second bool return value specifies whether the user can change the state
// of the server (true) or whether the user is limited (false). The second is
// always false if the first is.
func (s *rpcServer) checkAuth(r *http.Request, require bool) (bool, bool, error) {
	authhdr := r.Header["Authorization"]
	if len(authhdr) <= 0 {
		if require {
			rpcsLog.Warnf("RPC authentication failure from %s",
				r.RemoteAddr)
			return false, false, errors.New("auth failure")
		}

		return false, false, nil
	}

	authsha := sha256.Sum256([]byte(authhdr[0]))

	// Check for limited auth first as in environments with limited users, those
	// are probably expected to have a higher volume of calls
	limitcmp := subtle.ConstantTimeCompare(authsha[:], s.limitauthsha[:])
	if limitcmp == 1 {
		return true, false, nil
	}

	// Check for admin-level auth
	cmp := subtle.ConstantTimeCompare(authsha[:], s.authsha[:])
	if cmp == 1 {
		return true, true, nil
	}

	// Request's auth doesn't match either user
	rpcsLog.Warnf("RPC authentication failure from %s", r.RemoteAddr)
	return false, false, errors.New("auth failure")
}

// parsedRPCCmd represents a JSON-RPC request object that has been parsed into
// a known concrete command along with any error that might have happened while
// parsing it.
type parsedRPCCmd struct {
	id     interface{}
	method string
	cmd    interface{}
	err    *btcjson.RPCError
}

// standardCmdResult checks that a parsed command is a standard Bitcoin JSON-RPC
// command and runs the appropriate handler to reply to the command.  Any
// commands which are not recognized or not implemented will return an error
// suitable for use in replies.
func (s *rpcServer) standardCmdResult(cmd *parsedRPCCmd, closeChan <-chan struct{}) (interface{}, error) {
	handler, ok := rpcHandlers[cmd.method]
	if ok {
		goto handled
	}
	_, ok = rpcAskWallet[cmd.method]
	if ok {
		handler = handleAskWallet
		goto handled
	}
	_, ok = rpcUnimplemented[cmd.method]
	if ok {
		handler = handleUnimplemented
		goto handled
	}
	return nil, btcjson.ErrRPCMethodNotFound
handled:

	return handler(s, cmd.cmd, closeChan)
}

// parseCmd parses a JSON-RPC request object into known concrete command.  The
// err field of the returned parsedRPCCmd struct will contain an RPC error that
// is suitable for use in replies if the command is invalid in some way such as
// an unregistered command or invalid parameters.
func parseCmd(request *btcjson.Request) *parsedRPCCmd {
	var parsedCmd parsedRPCCmd
	parsedCmd.id = request.ID
	parsedCmd.method = request.Method

	cmd, err := btcjson.UnmarshalCmd(request)
	if err != nil {
		// When the error is because the method is not registered,
		// produce a method not found RPC error.
		if jerr, ok := err.(btcjson.Error); ok &&
			jerr.ErrorCode == btcjson.ErrUnregisteredMethod {

			parsedCmd.err = btcjson.ErrRPCMethodNotFound
			return &parsedCmd
		}

		// Otherwise, some type of invalid parameters is the
		// cause, so produce the equivalent RPC error.
		parsedCmd.err = btcjson.NewRPCError(
			btcjson.ErrRPCInvalidParams.Code, err.Error())
		return &parsedCmd
	}

	parsedCmd.cmd = cmd
	return &parsedCmd
}

// createMarshalledReply returns a new marshalled JSON-RPC response given the
// passed parameters.  It will automatically convert errors that are not of
// the type *btcjson.RPCError to the appropriate type as needed.
func createMarshalledReply(id, result interface{}, replyErr error) ([]byte, error) {
	var jsonErr *btcjson.RPCError
	if replyErr != nil {
		if jErr, ok := replyErr.(*btcjson.RPCError); ok {
			jsonErr = jErr
		} else {
			jsonErr = internalRPCError(replyErr.Error(), "")
		}
	}

	return btcjson.MarshalResponse(id, result, jsonErr)
}

// jsonRPCRead handles reading and responding to RPC messages.
func (s *rpcServer) jsonRPCRead(w http.ResponseWriter, r *http.Request, isAdmin bool) {
	if atomic.LoadInt32(&s.shutdown) != 0 {
		return
	}

	// Read and close the JSON-RPC request body from the caller.
	body, err := ioutil.ReadAll(r.Body)
	r.Body.Close()
	if err != nil {
		errCode := http.StatusBadRequest
		http.Error(w, fmt.Sprintf("%d error reading JSON message: %v",
			errCode, err), errCode)
		return
	}

	// Unfortunately, the http server doesn't provide the ability to
	// change the read deadline for the new connection and having one breaks
	// long polling.  However, not having a read deadline on the initial
	// connection would mean clients can connect and idle forever.  Thus,
	// hijack the connecton from the HTTP server, clear the read deadline,
	// and handle writing the response manually.
	hj, ok := w.(http.Hijacker)
	if !ok {
		errMsg := "webserver doesn't support hijacking"
		rpcsLog.Warnf(errMsg)
		errCode := http.StatusInternalServerError
		http.Error(w, strconv.Itoa(errCode)+" "+errMsg, errCode)
		return
	}
	conn, buf, err := hj.Hijack()
	if err != nil {
		rpcsLog.Warnf("Failed to hijack HTTP connection: %v", err)
		errCode := http.StatusInternalServerError
		http.Error(w, strconv.Itoa(errCode)+" "+err.Error(), errCode)
		return
	}
	defer conn.Close()
	defer buf.Flush()
	conn.SetReadDeadline(timeZeroVal)

	// Attempt to parse the raw body into a JSON-RPC request.
	var responseID interface{}
	var jsonErr error
	var result interface{}
	var request btcjson.Request
	if err := json.Unmarshal(body, &request); err != nil {
		jsonErr = &btcjson.RPCError{
			Code:    btcjson.ErrRPCParse.Code,
			Message: "Failed to parse request: " + err.Error(),
		}
	}
	if jsonErr == nil {
		// The JSON-RPC 1.0 spec defines that notifications must have their "id"
		// set to null and states that notifications do not have a response.
		//
		// A JSON-RPC 2.0 notification is a request with "json-rpc":"2.0", and
		// without an "id" member. The specification states that notifications
		// must not be responded to. JSON-RPC 2.0 permits the null value as a
		// valid request id, therefore such requests are not notifications.
		//
		// Bitcoin Core serves requests with "id":null or even an absent "id",
		// and responds to such requests with "id":null in the response.
		//
		// Btcd does not respond to any request without and "id" or "id":null,
		// regardless the indicated JSON-RPC protocol version unless RPC quirks
		// are enabled. With RPC quirks enabled, such requests will be responded
		// to if the reqeust does not indicate JSON-RPC version.
		//
		// RPC quirks can be enabled by the user to avoid compatibility issues
		// with software relying on Core's behavior.
		if request.ID == nil && !(cfg.RPCQuirks && request.Jsonrpc == "") {
			return
		}

		// The parse was at least successful enough to have an ID so
		// set it for the response.
		responseID = request.ID

		// Setup a close notifier.  Since the connection is hijacked,
		// the CloseNotifer on the ResponseWriter is not available.
		closeChan := make(chan struct{}, 1)
		go func() {
			_, err := conn.Read(make([]byte, 1))
			if err != nil {
				close(closeChan)
			}
		}()

		// Check if the user is limited and set error if method unauthorized
		if !isAdmin {
			if _, ok := rpcLimited[request.Method]; !ok {
				jsonErr = &btcjson.RPCError{
					Code:    btcjson.ErrRPCInvalidParams.Code,
					Message: "limited user not authorized for this method",
				}
			}
		}

		if jsonErr == nil {
			// Attempt to parse the JSON-RPC request into a known concrete
			// command.
			parsedCmd := parseCmd(&request)
			if parsedCmd.err != nil {
				jsonErr = parsedCmd.err
			} else {
				result, jsonErr = s.standardCmdResult(parsedCmd, closeChan)
			}
		}
	}

	// Marshal the response.
	msg, err := createMarshalledReply(responseID, result, jsonErr)
	if err != nil {
		rpcsLog.Errorf("Failed to marshal reply: %v", err)
		return
	}

	// Write the response.
	err = s.writeHTTPResponseHeaders(r, w.Header(), http.StatusOK, buf)
	if err != nil {
		rpcsLog.Error(err)
		return
	}
	if _, err := buf.Write(msg); err != nil {
		rpcsLog.Errorf("Failed to write marshalled reply: %v", err)
	}

	// Terminate with newline to maintain compatibility with Bitcoin Core.
	if err := buf.WriteByte('\n'); err != nil {
		rpcsLog.Errorf("Failed to append terminating newline to reply: %v", err)
	}
}

// jsonAuthFail sends a message back to the client if the http auth is rejected.
func jsonAuthFail(w http.ResponseWriter) {
	w.Header().Add("WWW-Authenticate", `Basic realm="btcd RPC"`)
	http.Error(w, "401 Unauthorized.", http.StatusUnauthorized)
}

// Start is used by server.go to start the rpc listener.
func (s *rpcServer) Start() {
	if atomic.AddInt32(&s.started, 1) != 1 {
		return
	}

	rpcsLog.Trace("Starting RPC server")
	rpcServeMux := http.NewServeMux()
	httpServer := &http.Server{
		Handler: rpcServeMux,

		// Timeout connections which don't complete the initial
		// handshake within the allowed timeframe.
		ReadTimeout: time.Second * rpcAuthTimeoutSeconds,
	}
	rpcServeMux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Connection", "close")
		w.Header().Set("Content-Type", "application/json")
		r.Close = true

		// Limit the number of connections to max allowed.
		if s.limitConnections(w, r.RemoteAddr) {
			return
		}

		// Keep track of the number of connected clients.
		s.incrementClients()
		defer s.decrementClients()
		_, isAdmin, err := s.checkAuth(r, true)
		if err != nil {
			jsonAuthFail(w)
			return
		}

		// Read and respond to the request.
		s.jsonRPCRead(w, r, isAdmin)
	})

	// Websocket endpoint.
	rpcServeMux.HandleFunc("/ws", func(w http.ResponseWriter, r *http.Request) {
		authenticated, isAdmin, err := s.checkAuth(r, false)
		if err != nil {
			jsonAuthFail(w)
			return
		}

		// Attempt to upgrade the connection to a websocket connection
		// using the default size for read/write buffers.
		ws, err := websocket.Upgrade(w, r, nil, 0, 0)
		if err != nil {
			if _, ok := err.(websocket.HandshakeError); !ok {
				rpcsLog.Errorf("Unexpected websocket error: %v",
					err)
			}
			http.Error(w, "400 Bad Request.", http.StatusBadRequest)
			return
		}
		s.WebsocketHandler(ws, r.RemoteAddr, authenticated, isAdmin)
	})

	for _, listener := range s.cfg.Listeners {
		s.wg.Add(1)
		go func(listener net.Listener) {
			rpcsLog.Infof("RPC server listening on %s", listener.Addr())
			httpServer.Serve(listener)
			rpcsLog.Tracef("RPC listener done for %s", listener.Addr())
			s.wg.Done()
		}(listener)
	}

	s.ntfnMgr.Start()
}

// genCertPair generates a key/cert pair to the paths provided.
func genCertPair(certFile, keyFile string) error {
	rpcsLog.Infof("Generating TLS certificates...")

	org := "btcd autogenerated cert"
	validUntil := time.Now().Add(10 * 365 * 24 * time.Hour)
	cert, key, err := btcutil.NewTLSCertPair(org, validUntil, nil)
	if err != nil {
		return err
	}

	// Write cert and key files.
	if err = ioutil.WriteFile(certFile, cert, 0666); err != nil {
		return err
	}
	if err = ioutil.WriteFile(keyFile, key, 0600); err != nil {
		os.Remove(certFile)
		return err
	}

	rpcsLog.Infof("Done generating TLS certificates")
	return nil
}

// rpcserverPeer represents a peer for use with the RPC server.
//
// The interface contract requires that all of these methods are safe for
// concurrent access.
type rpcserverPeer interface {
	// ToPeer returns the underlying peer instance.
	ToPeer() *peer.Peer

	// IsTxRelayDisabled returns whether or not the peer has disabled
	// transaction relay.
	IsTxRelayDisabled() bool

	// BanScore returns the current integer value that represents how close
	// the peer is to being banned.
	BanScore() uint32

	// FeeFilter returns the requested current minimum fee rate for which
	// transactions should be announced.
	FeeFilter() int64
}

// rpcserverConnManager represents a connection manager for use with the RPC
// server.
//
// The interface contract requires that all of these methods are safe for
// concurrent access.
type rpcserverConnManager interface {
	// Connect adds the provided address as a new outbound peer.  The
	// permanent flag indicates whether or not to make the peer persistent
	// and reconnect if the connection is lost.  Attempting to connect to an
	// already existing peer will return an error.
	Connect(addr string, permanent bool) error

	// RemoveByID removes the peer associated with the provided id from the
	// list of persistent peers.  Attempting to remove an id that does not
	// exist will return an error.
	RemoveByID(id int32) error

	// RemoveByAddr removes the peer associated with the provided address
	// from the list of persistent peers.  Attempting to remove an address
	// that does not exist will return an error.
	RemoveByAddr(addr string) error

	// DisconnectByID disconnects the peer associated with the provided id.
	// This applies to both inbound and outbound peers.  Attempting to
	// remove an id that does not exist will return an error.
	DisconnectByID(id int32) error

	// DisconnectByAddr disconnects the peer associated with the provided
	// address.  This applies to both inbound and outbound peers.
	// Attempting to remove an address that does not exist will return an
	// error.
	DisconnectByAddr(addr string) error

	// ConnectedCount returns the number of currently connected peers.
	ConnectedCount() int32

	// NetTotals returns the sum of all bytes received and sent across the
	// network for all peers.
	NetTotals() (uint64, uint64)

	// ConnectedPeers returns an array consisting of all connected peers.
	ConnectedPeers() []rpcserverPeer

	// PersistentPeers returns an array consisting of all the persistent
	// peers.
	PersistentPeers() []rpcserverPeer

	// BroadcastMessage sends the provided message to all currently
	// connected peers.
	BroadcastMessage(msg wire.Message)

	// AddRebroadcastInventory adds the provided inventory to the list of
	// inventories to be rebroadcast at random intervals until they show up
	// in a block.
	AddRebroadcastInventory(iv *wire.InvVect, data interface{})

	// RelayTransactions generates and relays inventory vectors for all of
	// the passed transactions to all connected peers.
	RelayTransactions(txns []*mempool.TxDesc)
}

// rpcserverSyncManager represents a sync manager for use with the RPC server.
//
// The interface contract requires that all of these methods are safe for
// concurrent access.
type rpcserverSyncManager interface {
	// IsCurrent returns whether or not the sync manager believes the chain
	// is current as compared to the rest of the network.
	IsCurrent() bool

	// SubmitBlock submits the provided block to the network after
	// processing it locally.
	SubmitBlock(block *btcutil.Block, flags blockchain.BehaviorFlags) (bool, error)

	// Pause pauses the sync manager until the returned channel is closed.
	Pause() chan<- struct{}

	// SyncPeerID returns the ID of the peer that is currently the peer being
	// used to sync from or 0 if there is none.
	SyncPeerID() int32

	// LocateHeaders returns the headers of the blocks after the first known
	// block in the provided locators until the provided stop hash or the
	// current tip is reached, up to a max of wire.MaxBlockHeadersPerMsg
	// hashes.
	LocateHeaders(locators []*chainhash.Hash, hashStop *chainhash.Hash) []wire.BlockHeader
}

// rpcserverConfig is a descriptor containing the RPC server configuration.
type rpcserverConfig struct {
	// Listeners defines a slice of listeners for which the RPC server will
	// take ownership of and accept connections.  Since the RPC server takes
	// ownership of these listeners, they will be closed when the RPC server
	// is stopped.
	Listeners []net.Listener

	// StartupTime is the unix timestamp for when the server that is hosting
	// the RPC server started.
	StartupTime int64

	// ConnMgr defines the connection manager for the RPC server to use.  It
	// provides the RPC server with a means to do things such as add,
	// remove, connect, disconnect, and query peers as well as other
	// connection-related data and tasks.
	ConnMgr rpcserverConnManager

	// SyncMgr defines the sync manager for the RPC server to use.
	SyncMgr rpcserverSyncManager

	// These fields allow the RPC server to interface with the local block
	// chain data and state.
	TimeSource  blockchain.MedianTimeSource
	Chain       *blockchain.BlockChain
	ChainParams *chaincfg.Params
	DB          database.DB

	// TxMemPool defines the transaction memory pool to interact with.
	TxMemPool *mempool.TxPool

	// These fields allow the RPC server to interface with mining.
	//
	// Generator produces block templates and the CPUMiner solves them using
	// the CPU.  CPU mining is typically only useful for test purposes when
	// doing regression or simulation testing.
	Generator *mining.BlkTmplGenerator
	CPUMiner  *cpuminer.CPUMiner

	// These fields define any optional indexes the RPC server can make use
	// of to provide additional data when queried.
	TxIndex   *indexers.TxIndex
	AddrIndex *indexers.AddrIndex
	CfIndex   *indexers.CfIndex

	// The fee estimator keeps track of how long transactions are left in
	// the mempool before they are mined into blocks.
	FeeEstimator *mempool.FeeEstimator
}

// newRPCServer returns a new instance of the rpcServer struct.
func newRPCServer(config *rpcserverConfig) (*rpcServer, error) {
	rpc := rpcServer{
		cfg:                    *config,
		statusLines:            make(map[int]string),
		gbtWorkState:           newGbtWorkState(config.TimeSource),
		helpCacher:             newHelpCacher(),
		requestProcessShutdown: make(chan struct{}),
		quit: make(chan int),
	}
	if cfg.RPCUser != "" && cfg.RPCPass != "" {
		login := cfg.RPCUser + ":" + cfg.RPCPass
		auth := "Basic " + base64.StdEncoding.EncodeToString([]byte(login))
		rpc.authsha = sha256.Sum256([]byte(auth))
	}
	if cfg.RPCLimitUser != "" && cfg.RPCLimitPass != "" {
		login := cfg.RPCLimitUser + ":" + cfg.RPCLimitPass
		auth := "Basic " + base64.StdEncoding.EncodeToString([]byte(login))
		rpc.limitauthsha = sha256.Sum256([]byte(auth))
	}
	rpc.ntfnMgr = newWsNotificationManager(&rpc)
	rpc.cfg.Chain.Subscribe(rpc.handleBlockchainNotification)

	return &rpc, nil
}

// Callback for notifications from blockchain.  It notifies clients that are
// long polling for changes or subscribed to websockets notifications.
func (s *rpcServer) handleBlockchainNotification(notification *blockchain.Notification) {
	switch notification.Type {
	case blockchain.NTBlockAccepted:
		block, ok := notification.Data.(*btcutil.Block)
		if !ok {
			rpcsLog.Warnf("Chain accepted notification is not a block.")
			break
		}

		// Allow any clients performing long polling via the
		// getblocktemplate RPC to be notified when the new block causes
		// their old block template to become stale.
		s.gbtWorkState.NotifyBlockConnected(block.Hash())

	case blockchain.NTBlockConnected:
		block, ok := notification.Data.(*btcutil.Block)
		if !ok {
			rpcsLog.Warnf("Chain connected notification is not a block.")
			break
		}

		// Notify registered websocket clients of incoming block.
		s.ntfnMgr.NotifyBlockConnected(block)

	case blockchain.NTBlockDisconnected:
		block, ok := notification.Data.(*btcutil.Block)
		if !ok {
			rpcsLog.Warnf("Chain disconnected notification is not a block.")
			break
		}

		// Notify registered websocket clients.
		s.ntfnMgr.NotifyBlockDisconnected(block)
	}
}

func init() {
	rpcHandlers = rpcHandlersBeforeInit
	rand.Seed(time.Now().UnixNano())
}