func (s *loaderServer) CreateWallet(ctx context.Context, req *pb.CreateWalletRequest) (
	*pb.CreateWalletResponse, error) {

	defer func() {
		zero.Bytes(req.PrivatePassphrase)
		zero.Bytes(req.Seed)
	}()

	// Use an insecure public passphrase when the request's is empty.
	pubPassphrase := req.PublicPassphrase
	if len(pubPassphrase) == 0 {
		pubPassphrase = []byte(wallet.InsecurePubPassphrase)
	}

	wallet, err := s.loader.CreateNewWallet(pubPassphrase, req.PrivatePassphrase, req.Seed)
	if err != nil {
		return nil, translateError(err)
	}

	s.mu.Lock()
	if s.rpcClient != nil {
		wallet.SynchronizeRPC(s.rpcClient)
	}
	s.mu.Unlock()

	return &pb.CreateWalletResponse{}, nil
}

// lock zeroes the associated clear text private key.
func (a *scriptAddress) lock() {
	// Zero and nil the clear text script associated with this address.
	a.scriptMutex.Lock()
	zero.Bytes(a.scriptCT)
	a.scriptCT = nil
	a.scriptMutex.Unlock()
}

// PrivKey returns the private key for the address.  It can fail if the address
// manager is watching-only or locked, or the address does not have any keys.
//
// This is part of the ManagedPubKeyAddress interface implementation.
func (a *managedAddress) PrivKey() (chainec.PrivateKey, error) {
	// No private keys are available for a watching-only address manager.
	if a.manager.watchingOnly {
		return nil, managerError(ErrWatchingOnly, errWatchingOnly, nil)
	}

	a.manager.mtx.Lock()
	defer a.manager.mtx.Unlock()

	// Account manager must be unlocked to decrypt the private key.
	if a.manager.locked {
		return nil, managerError(ErrLocked, errLocked, nil)
	}

	// Decrypt the key as needed.  Also, make sure it's a copy since the
	// private key stored in memory can be cleared at any time.  Otherwise
	// the returned private key could be invalidated from under the caller.
	privKeyCopy, err := a.unlock(a.manager.cryptoKeyPriv)
	if err != nil {
		return nil, err
	}

	privKey, _ := chainec.Secp256k1.PrivKeyFromBytes(privKeyCopy)
	zero.Bytes(privKeyCopy)
	return privKey, nil
}

// deriveKey fills out the Key field.
func (sk *SecretKey) deriveKey(password *[]byte) error {
	key, err := scrypt.Key(*password, sk.Parameters.Salt[:],
		sk.Parameters.N,
		sk.Parameters.R,
		sk.Parameters.P,
		len(sk.Key))
	if err != nil {
		return err
	}
	copy(sk.Key[:], key)
	zero.Bytes(key)

	// I'm not a fan of forced garbage collections, but scrypt allocates a
	// ton of memory and calling it back to back without a GC cycle in
	// between means you end up needing twice the amount of memory.  For
	// example, if your scrypt parameters are such that you require 1GB and
	// you call it twice in a row, without this you end up allocating 2GB
	// since the first GB probably hasn't been released yet.
	debug.FreeOSMemory()

	// I'm not a fan of forced garbage collections, but scrypt allocates a
	// ton of memory and calling it back to back without a GC cycle in
	// between means you end up needing twice the amount of memory.  For
	// example, if your scrypt parameters are such that you require 1GB and
	// you call it twice in a row, without this you end up allocating 2GB
	// since the first GB probably hasn't been released yet.
	debug.FreeOSMemory()

	return nil
}

func (s *walletServer) NextAccount(ctx context.Context, req *pb.NextAccountRequest) (
	*pb.NextAccountResponse, error) {

	defer zero.Bytes(req.Passphrase)

	if req.AccountName == "" {
		return nil, grpc.Errorf(codes.InvalidArgument, "account name may not be empty")
	}

	lock := make(chan time.Time, 1)
	defer func() {
		lock <- time.Time{} // send matters, not the value
	}()
	err := s.wallet.Unlock(req.Passphrase, lock)
	if err != nil {
		return nil, translateError(err)
	}

	account, err := s.wallet.NextAccount(req.AccountName)
	if err != nil {
		return nil, translateError(err)
	}

	return &pb.NextAccountResponse{AccountNumber: account}, nil
}

func (s *walletServer) ImportScript(ctx context.Context,
	req *pb.ImportScriptRequest) (*pb.ImportScriptResponse, error) {

	defer zero.Bytes(req.Passphrase)

	lock := make(chan time.Time, 1)
	defer func() {
		lock <- time.Time{} // send matters, not the value
	}()
	err := s.wallet.Unlock(req.Passphrase, lock)
	if err != nil {
		return nil, translateError(err)
	}

	if req.ScanFrom < 0 {
		return nil, grpc.Errorf(codes.InvalidArgument,
			"Attempted to scan from a negative block height")
	}

	if req.ScanFrom > 0 && req.Rescan == true {
		return nil, grpc.Errorf(codes.InvalidArgument,
			"Passed a rescan height without rescan set")
	}

	err = s.wallet.ImportScript(req.Script, req.Rescan, req.ScanFrom)
	if err != nil {
		return nil, translateError(err)
	}

	return &pb.ImportScriptResponse{}, nil
}

func (s *walletServer) ImportPrivateKey(ctx context.Context, req *pb.ImportPrivateKeyRequest) (
	*pb.ImportPrivateKeyResponse, error) {

	defer zero.Bytes(req.Passphrase)

	wif, err := dcrutil.DecodeWIF(req.PrivateKeyWif)
	if err != nil {
		return nil, grpc.Errorf(codes.InvalidArgument,
			"Invalid WIF-encoded private key: %v", err)
	}

	lock := make(chan time.Time, 1)
	defer func() {
		lock <- time.Time{} // send matters, not the value
	}()
	err = s.wallet.Unlock(req.Passphrase, lock)
	if err != nil {
		return nil, translateError(err)
	}

	// At the moment, only the special-cased import account can be used to
	// import keys.
	if req.Account != waddrmgr.ImportedAddrAccount {
		return nil, grpc.Errorf(codes.InvalidArgument,
			"Only the imported account accepts private key imports")
	}

	if req.ScanFrom < 0 {
		return nil, grpc.Errorf(codes.InvalidArgument,
			"Attempted to scan from a negative block height")
	}

	if req.ScanFrom > 0 && req.Rescan == true {
		return nil, grpc.Errorf(codes.InvalidArgument,
			"Passed a rescan height without rescan set")
	}

	chainClient := s.wallet.ChainClient()
	if req.Rescan && chainClient == nil {
		return nil, grpc.Errorf(codes.FailedPrecondition,
			"Cannot rescan without an associated consensus server RPC client")
	}

	_, err = s.wallet.ImportPrivateKey(wif)
	if err != nil {
		return nil, translateError(err)
	}

	if req.Rescan {
		s.wallet.RescanFromHeight(chainClient, req.ScanFrom)
	}

	return &pb.ImportPrivateKeyResponse{}, nil
}

func (s *walletServer) ChangePassphrase(ctx context.Context, req *pb.ChangePassphraseRequest) (
	*pb.ChangePassphraseResponse, error) {

	defer func() {
		zero.Bytes(req.OldPassphrase)
		zero.Bytes(req.NewPassphrase)
	}()

	var err error
	switch req.Key {
	case pb.ChangePassphraseRequest_PRIVATE:
		err = s.wallet.ChangePrivatePassphrase(req.OldPassphrase, req.NewPassphrase)
	case pb.ChangePassphraseRequest_PUBLIC:
		err = s.wallet.ChangePublicPassphrase(req.OldPassphrase, req.NewPassphrase)
	default:
		return nil, grpc.Errorf(codes.InvalidArgument, "Unknown key type (%d)", req.Key)
	}
	if err != nil {
		return nil, translateError(err)
	}
	return &pb.ChangePassphraseResponse{}, nil
}

func (s *loaderServer) StartConsensusRpc(ctx context.Context, req *pb.StartConsensusRpcRequest) (
	*pb.StartConsensusRpcResponse, error) {

	defer zero.Bytes(req.Password)

	defer s.mu.Unlock()
	s.mu.Lock()

	if s.rpcClient != nil {
		return nil, grpc.Errorf(codes.FailedPrecondition, "RPC client already created")
	}

	networkAddress, err := cfgutil.NormalizeAddress(req.NetworkAddress,
		s.activeNet.RPCClientPort)
	if err != nil {
		return nil, grpc.Errorf(codes.InvalidArgument,
			"Network address is ill-formed: %v", err)
	}

	// Error if the wallet is already syncing with the network.
	wallet, walletLoaded := s.loader.LoadedWallet()
	if walletLoaded && wallet.SynchronizingToNetwork() {
		return nil, grpc.Errorf(codes.FailedPrecondition,
			"wallet is loaded and already synchronizing")
	}

	rpcClient, err := chain.NewRPCClient(s.activeNet.Params, networkAddress, req.Username,
		string(req.Password), req.Certificate, len(req.Certificate) == 0, 1)
	if err != nil {
		return nil, translateError(err)
	}

	err = rpcClient.Start()
	if err != nil {
		if err == dcrrpcclient.ErrInvalidAuth {
			return nil, grpc.Errorf(codes.InvalidArgument,
				"Invalid RPC credentials: %v", err)
		}
		return nil, grpc.Errorf(codes.NotFound,
			"Connection to RPC server failed: %v", err)
	}

	s.rpcClient = rpcClient

	if walletLoaded {
		wallet.SynchronizeRPC(rpcClient)
	}

	return &pb.StartConsensusRpcResponse{}, nil
}

// decryptExtendedKey uses Manager.Decrypt() to decrypt the encrypted byte slice and return
// an extended (public or private) key representing it.
//
// This method must be called with the Pool's manager unlocked.
func (p *Pool) decryptExtendedKey(keyType waddrmgr.CryptoKeyType, encrypted []byte) (*hdkeychain.ExtendedKey, error) {
	decrypted, err := p.manager.Decrypt(keyType, encrypted)
	if err != nil {
		str := fmt.Sprintf("cannot decrypt key %v", encrypted)
		return nil, newError(ErrCrypto, str, err)
	}
	result, err := hdkeychain.NewKeyFromString(string(decrypted))
	zero.Bytes(decrypted)
	if err != nil {
		str := fmt.Sprintf("cannot get key from string %v", decrypted)
		return nil, newError(ErrKeyChain, str, err)
	}
	return result, nil
}

// BUGS:
// - InputIndexes request field is ignored.
func (s *walletServer) SignTransaction(ctx context.Context, req *pb.SignTransactionRequest) (
	*pb.SignTransactionResponse, error) {

	defer zero.Bytes(req.Passphrase)

	var tx wire.MsgTx
	err := tx.Deserialize(bytes.NewReader(req.SerializedTransaction))
	if err != nil {
		return nil, grpc.Errorf(codes.InvalidArgument,
			"Bytes do not represent a valid raw transaction: %v", err)
	}

	lock := make(chan time.Time, 1)
	defer func() {
		lock <- time.Time{} // send matters, not the value
	}()
	err = s.wallet.Unlock(req.Passphrase, lock)
	if err != nil {
		return nil, translateError(err)
	}

	invalidSigs, err := s.wallet.SignTransaction(&tx, txscript.SigHashAll, nil, nil, nil)
	if err != nil {
		return nil, translateError(err)
	}

	invalidInputIndexes := make([]uint32, len(invalidSigs))
	for i, e := range invalidSigs {
		invalidInputIndexes[i] = e.InputIndex
	}

	var serializedTransaction bytes.Buffer
	serializedTransaction.Grow(tx.SerializeSize())
	err = tx.Serialize(&serializedTransaction)
	if err != nil {
		return nil, translateError(err)
	}

	resp := &pb.SignTransactionResponse{
		Transaction:          serializedTransaction.Bytes(),
		UnsignedInputIndexes: invalidInputIndexes,
	}
	return resp, nil
}

func (s *loaderServer) DiscoverAddresses(ctx context.Context, req *pb.DiscoverAddressesRequest) (
	*pb.DiscoverAddressesResponse, error) {

	wallet, ok := s.loader.LoadedWallet()
	if !ok {
		return nil, grpc.Errorf(codes.FailedPrecondition, "wallet has not been loaded")
	}

	s.mu.Lock()
	chainClient := s.rpcClient
	s.mu.Unlock()
	if chainClient == nil {
		return nil, grpc.Errorf(codes.FailedPrecondition, "consensus server RPC client has not been loaded")
	}

	if req.DiscoverAccounts && len(req.PrivatePassphrase) == 0 {
		return nil, grpc.Errorf(codes.InvalidArgument, "private passphrase is required for discovering accounts")
	}

	if req.DiscoverAccounts {
		lock := make(chan time.Time, 1)
		defer func() {
			lock <- time.Time{}
			zero.Bytes(req.PrivatePassphrase)
		}()
		err := wallet.Unlock(req.PrivatePassphrase, lock)
		if err != nil {
			return nil, translateError(err)
		}
	}

	err := wallet.DiscoverActiveAddresses(chainClient, req.DiscoverAccounts)
	if err != nil {
		return nil, translateError(err)
	}

	return &pb.DiscoverAddressesResponse{}, nil
}

// startPromptPass prompts the user for a password to unlock their wallet in
// the event that it was restored from seed or --promptpass flag is set.
func startPromptPass(w *wallet.Wallet) {
	promptPass := cfg.PromptPass

	// Watching only wallets never require a password.
	if w.Manager.WatchingOnly() {
		return
	}

	// The wallet is totally desynced, so we need to resync accounts.
	// Prompt for the password. Then, set the flag it wallet so it
	// knows which address functions to call when resyncing.
	needSync := w.NeedsAccountsSync()
	if needSync {
		promptPass = true
	}
	if !promptPass {
		return
	}
	w.SetInitiallyUnlocked(true)
	backendLog.Flush()
	fmt.Println("*** ATTENTION ***")
	fmt.Println("Since this is your first time running we need to sync accounts. Please enter")
	fmt.Println("the private wallet passphrase. This will complete syncing of the wallet")
	fmt.Println("accounts and then leave your wallet unlocked. You may relock wallet after by")
	fmt.Println("calling 'walletlock' through the RPC.")
	fmt.Println("*****************")

	// We need to rescan accounts for the initial sync. Unlock the
	// wallet after prompting for the passphrase. The special case
	// of a --createtemp simnet wallet is handled by first
	// attempting to automatically open it with the default
	// passphrase. The wallet should also request to be unlocked
	// if stake mining is currently on, so users with this flag
	// are prompted here as well.
	for {
		if w.ChainParams() == &chaincfg.SimNetParams {
			var unlockAfter <-chan time.Time
			err := w.Unlock(wallet.SimulationPassphrase, unlockAfter)
			if err == nil {
				// Unlock success with the default password.
				return
			}
		}
		if promptPass {
			backendLog.Flush()
			reader := bufio.NewReader(os.Stdin)
			passphrase, err := prompt.PassPrompt(reader, "Enter private passphrase", false)
			if err != nil {
				fmt.Println("Failed to input password. Please try again.")
				continue
			}
			defer zero.Bytes(passphrase)

			var unlockAfter <-chan time.Time
			err = w.Unlock(passphrase, unlockAfter)
			if err != nil {
				fmt.Println("Incorrect password entered. Please " +
					"try again.")
				continue
			}

			break
		}
	}
}