services/friendbot: support funding existing accounts

services/friendbot/init_friendbot.go

@@ -104,6 +104,7 @@ func createMinionAccounts(botAccount internal.Account, botKeypair *keypair.Full,
 				StartingBalance:      newAccountBalance,
 				SubmitTransaction:    internal.SubmitTransaction,
 				CheckSequenceRefresh: internal.CheckSequenceRefresh,
+				CheckAccountExists:   internal.CheckAccountExists,
 				BaseFee:              baseFee,
 			})
 

services/friendbot/internal/friendbot_test.go

@@ -12,13 +12,17 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func TestFriendbot_Pay(t *testing.T) {
+func TestFriendbot_Pay_accountDoesNotExist(t *testing.T) {
 	mockSubmitTransaction := func(minion *Minion, hclient horizonclient.ClientInterface, tx string) (*hProtocol.Transaction, error) {
 		// Instead of submitting the tx, we emulate a success.
 		txSuccess := hProtocol.Transaction{EnvelopeXdr: tx, Successful: true}
 		return &txSuccess, nil
 	}
 
+	mockCheckAccountExists := func(minion *Minion, hclient horizonclient.ClientInterface, destAddress string) (bool, string, error) {
+		return false, "0", nil
+	}
+
 	// Public key: GD25B4QI6KWVDWXDW25CIM7EKR6A6PBSWE2RCNSAC4NJQDQJXZJYMMKR
 	botSeed := "SCWNLYELENPBXN46FHYXETT5LJCYBZD5VUQQVW4KZPHFO2YTQJUWT4D5"
 	botKeypair, err := keypair.Parse(botSeed)
@@ -46,6 +50,7 @@ func TestFriendbot_Pay(t *testing.T) {
 		StartingBalance:      "10000.00",
 		SubmitTransaction:    mockSubmitTransaction,
 		CheckSequenceRefresh: CheckSequenceRefresh,
+		CheckAccountExists:   mockCheckAccountExists,
 		BaseFee:              txnbuild.MinBaseFee,
 	}
 	fb := &Bot{Minions: []Minion{minion}}
@@ -73,3 +78,118 @@ func TestFriendbot_Pay(t *testing.T) {
 	}()
 	wg.Wait()
 }
+
+func TestFriendbot_Pay_accountExists(t *testing.T) {
+	mockSubmitTransaction := func(minion *Minion, hclient horizonclient.ClientInterface, tx string) (*hProtocol.Transaction, error) {
+		// Instead of submitting the tx, we emulate a success.
+		txSuccess := hProtocol.Transaction{EnvelopeXdr: tx, Successful: true}
+		return &txSuccess, nil
+	}
+
+	mockCheckAccountExists := func(minion *Minion, hclient horizonclient.ClientInterface, destAddress string) (bool, string, error) {
+		return true, "0", nil
+	}
+
+	// Public key: GD25B4QI6KWVDWXDW25CIM7EKR6A6PBSWE2RCNSAC4NJQDQJXZJYMMKR
+	botSeed := "SCWNLYELENPBXN46FHYXETT5LJCYBZD5VUQQVW4KZPHFO2YTQJUWT4D5"
+	botKeypair, err := keypair.Parse(botSeed)
+	if !assert.NoError(t, err) {
+		return
+	}
+	botAccount := Account{AccountID: botKeypair.Address()}
+
+	// Public key: GD4AGPPDFFHKK3Z2X4XZDRXX6GZQKP4FMLVQ5T55NDEYGG3GIP7BQUHM
+	minionSeed := "SDTNSEERJPJFUE2LSDNYBFHYGVTPIWY7TU2IOJZQQGLWO2THTGB7NU5A"
+	minionKeypair, err := keypair.Parse(minionSeed)
+	if !assert.NoError(t, err) {
+		return
+	}
+
+	minion := Minion{
+		Account: Account{
+			AccountID: minionKeypair.Address(),
+			Sequence:  1,
+		},
+		Keypair:              minionKeypair.(*keypair.Full),
+		BotAccount:           botAccount,
+		BotKeypair:           botKeypair.(*keypair.Full),
+		Network:              "Test SDF Network ; September 2015",
+		StartingBalance:      "10000.00",
+		SubmitTransaction:    mockSubmitTransaction,
+		CheckSequenceRefresh: CheckSequenceRefresh,
+		CheckAccountExists:   mockCheckAccountExists,
+		BaseFee:              txnbuild.MinBaseFee,
+	}
+	fb := &Bot{Minions: []Minion{minion}}
+
+	recipientAddress := "GDJIN6W6PLTPKLLM57UW65ZH4BITUXUMYQHIMAZFYXF45PZVAWDBI77Z"
+	txSuccess, err := fb.Pay(recipientAddress)
+	if !assert.NoError(t, err) {
+		return
+	}
+	expectedTxn := "AAAAAgAAAAD4Az3jKU6lbzq/L5HG9/GzBT+FYusOz71oyYMbZkP+GAAAAGQAAAAAAAAAAgAAAAEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAEAAAABAAAAAPXQ8gjyrVHa47a6JDPkVHwPPDKxNRE2QBcamA4JvlOGAAAAAQAAAADShvreeub1LWzv6W93J+BROl6MxA6GAyXFy86/NQWGFAAAAAAAAAAXSHboAAAAAAAAAAACZkP+GAAAAEBAwm/hWuu/ZHHQWRD9oF/cnSwQyTZpHQoTlPlVSFH4g12HR2nbzOI9wC5Z5bt0ueXny4UNFS5QhUvnzdb2FMsDCb5ThgAAAED1HzWPW6lKBxBi6MTSwM/POytPSfL87taiarpTIk5naoqXPLpM0YBBaf5uH8de5Id1KSCP/g8tdeCxvrT053kJ"
+	assert.Equal(t, expectedTxn, txSuccess.EnvelopeXdr)
+
+	// Don't assert on tx values below, since the completion order is unknown.
+	var wg sync.WaitGroup
+	wg.Add(2)
+	go func() {
+		_, err := fb.Pay(recipientAddress)
+		assert.NoError(t, err)
+		wg.Done()
+	}()
+	go func() {
+		_, err := fb.Pay(recipientAddress)
+		assert.NoError(t, err)
+		wg.Done()
+	}()
+	wg.Wait()
+}
+
+func TestFriendbot_Pay_accountExistsAlreadyFunded(t *testing.T) {
+	mockSubmitTransaction := func(minion *Minion, hclient horizonclient.ClientInterface, tx string) (*hProtocol.Transaction, error) {
+		// Instead of submitting the tx, we emulate a success.
+		txSuccess := hProtocol.Transaction{EnvelopeXdr: tx, Successful: true}
+		return &txSuccess, nil
+	}
+
+	mockCheckAccountExists := func(minion *Minion, hclient horizonclient.ClientInterface, destAddress string) (bool, string, error) {
+		return true, "10000.00", nil
+	}
+
+	// Public key: GD25B4QI6KWVDWXDW25CIM7EKR6A6PBSWE2RCNSAC4NJQDQJXZJYMMKR
+	botSeed := "SCWNLYELENPBXN46FHYXETT5LJCYBZD5VUQQVW4KZPHFO2YTQJUWT4D5"
+	botKeypair, err := keypair.Parse(botSeed)
+	if !assert.NoError(t, err) {
+		return
+	}
+	botAccount := Account{AccountID: botKeypair.Address()}
+
+	// Public key: GD4AGPPDFFHKK3Z2X4XZDRXX6GZQKP4FMLVQ5T55NDEYGG3GIP7BQUHM
+	minionSeed := "SDTNSEERJPJFUE2LSDNYBFHYGVTPIWY7TU2IOJZQQGLWO2THTGB7NU5A"
+	minionKeypair, err := keypair.Parse(minionSeed)
+	if !assert.NoError(t, err) {
+		return
+	}
+
+	minion := Minion{
+		Account: Account{
+			AccountID: minionKeypair.Address(),
+			Sequence:  1,
+		},
+		Keypair:              minionKeypair.(*keypair.Full),
+		BotAccount:           botAccount,
+		BotKeypair:           botKeypair.(*keypair.Full),
+		Network:              "Test SDF Network ; September 2015",
+		StartingBalance:      "10000.00",
+		SubmitTransaction:    mockSubmitTransaction,
+		CheckSequenceRefresh: CheckSequenceRefresh,
+		CheckAccountExists:   mockCheckAccountExists,
+		BaseFee:              txnbuild.MinBaseFee,
+	}
+	fb := &Bot{Minions: []Minion{minion}}
+
+	recipientAddress := "GDJIN6W6PLTPKLLM57UW65ZH4BITUXUMYQHIMAZFYXF45PZVAWDBI77Z"
+	_, err = fb.Pay(recipientAddress)
+	assert.ErrorIs(t, err, ErrAccountFunded)
+}

services/friendbot/internal/minion.go

@@ -3,6 +3,7 @@ package internal
 import (
 	"fmt"
 
+	"github.com/stellar/go/amount"
 	"github.com/stellar/go/clients/horizonclient"
 	"github.com/stellar/go/keypair"
 	hProtocol "github.com/stellar/go/protocols/horizon"
@@ -14,6 +15,8 @@ const createAccountAlreadyExistXDR = "AAAAAAAAAGT/////AAAAAQAAAAAAAAAA/////AAAAA
 
 var ErrAccountExists error = errors.New(fmt.Sprintf("createAccountAlreadyExist (%s)", createAccountAlreadyExistXDR))
 
+var ErrAccountFunded error = errors.New("account already funded to starting balance")
+
 // Minion contains a Stellar channel account and Go channels to communicate with friendbot.
 type Minion struct {
 	Account         Account
@@ -28,6 +31,7 @@ type Minion struct {
 	// Mockable functions
 	SubmitTransaction    func(minion *Minion, hclient horizonclient.ClientInterface, tx string) (*hProtocol.Transaction, error)
 	CheckSequenceRefresh func(minion *Minion, hclient horizonclient.ClientInterface) error
+	CheckAccountExists   func(minion *Minion, hclient horizonclient.ClientInterface, destAddress string) (bool, string, error)
 
 	// Uninitialized.
 	forceRefreshSequence bool
@@ -44,14 +48,38 @@ func (minion *Minion) Run(destAddress string, resultChan chan SubmitResult) {
 		}
 		return
 	}
-	txHash, txStr, err := minion.makeTx(destAddress)
+	exists, balance, err := minion.CheckAccountExists(minion, minion.Horizon, destAddress)
+	if err != nil {
+		resultChan <- SubmitResult{
+			maybeTransactionSuccess: nil,
+			maybeErr:                errors.Wrap(err, "checking account exists"),
+		}
+		return
+	}
+	err = minion.checkBalance(balance)
+	if err != nil {
+		resultChan <- SubmitResult{
+			maybeTransactionSuccess: nil,
+			maybeErr:                errors.Wrap(err, "account already funded"),
+		}
+		return
+	}
+	txHash, txStr, err := minion.makeTx(destAddress, exists)
 	if err != nil {
 		resultChan <- SubmitResult{
 			maybeTransactionSuccess: nil,
 			maybeErr:                errors.Wrap(err, "making payment tx"),
 		}
 		return
 	}
+	_, err = minion.Account.IncrementSequenceNumber()
+	if err != nil {
+		resultChan <- SubmitResult{
+			maybeTransactionSuccess: nil,
+			maybeErr:                errors.Wrap(err, "incrementing submitters sequence number"),
+		}
+		return
+	}
 	succ, err := minion.SubmitTransaction(minion, minion.Horizon, txStr)
 	resultChan <- SubmitResult{
 		maybeTransactionSuccess: succ,
@@ -96,6 +124,30 @@ func CheckSequenceRefresh(minion *Minion, hclient horizonclient.ClientInterface)
 	return nil
 }
 
+// CheckAccountExists checks if the specified address exists as a Stellar account.
+// And returns the current native balance of the account also.
+// This should also be passed to the minion.
+func CheckAccountExists(minion *Minion, hclient horizonclient.ClientInterface, address string) (bool, string, error) {
+	accountRequest := horizonclient.AccountRequest{AccountID: address}
+	accountDetails, err := hclient.AccountDetail(accountRequest)
+	switch e := err.(type) {
+	case nil:
+		balance := "0"
+		for _, b := range accountDetails.Balances {
+			if b.Type == "native" {
+				balance = b.Balance
+				break
+			}
+		}
+		return true, balance, nil
+	case *horizonclient.Error:
+		if e.Response.StatusCode == 404 {
+			return false, "0", nil
+		}
+	}
+	return false, "0", err
+}
+
 func (minion *Minion) checkHandleBadSequence(err *horizonclient.Error) {
 	resCode, e := err.ResultCodes()
 	isTxBadSeqCode := e == nil && resCode.TransactionCode == "tx_bad_seq"
@@ -105,7 +157,30 @@ func (minion *Minion) checkHandleBadSequence(err *horizonclient.Error) {
 	minion.forceRefreshSequence = true
 }
 
-func (minion *Minion) makeTx(destAddress string) ([32]byte, string, error) {
+func (minion *Minion) checkBalance(balance string) error {
+	bal, err := amount.ParseInt64(balance)
+	if err != nil {
+		return errors.Wrap(err, "cannot parse account balance")
+	}
+	starting, err := amount.ParseInt64(minion.StartingBalance)
+	if err != nil {
+		return errors.Wrap(err, "cannot parse starting balance")
+	}
+	if bal >= starting {
+		return ErrAccountFunded
+	}
+	return nil
+}
+
+func (minion *Minion) makeTx(destAddress string, exists bool) ([32]byte, string, error) {
+	if exists {
+		return minion.makePaymentTx(destAddress)
+	} else {
+		return minion.makeCreateTx(destAddress)
+	}
+}
+
+func (minion *Minion) makeCreateTx(destAddress string) ([32]byte, string, error) {
 	createAccountOp := txnbuild.CreateAccount{
 		Destination:   destAddress,
 		SourceAccount: minion.BotAccount.GetAccountID(),
@@ -138,11 +213,43 @@ func (minion *Minion) makeTx(destAddress string) ([32]byte, string, error) {
 	if err != nil {
 		return [32]byte{}, "", errors.Wrap(err, "unable to hash")
 	}
+	return txh, txe, err
+}
 
-	// Increment the in-memory sequence number, since the tx will be submitted.
-	_, err = minion.Account.IncrementSequenceNumber()
+func (minion *Minion) makePaymentTx(destAddress string) ([32]byte, string, error) {
+	paymentOp := txnbuild.Payment{
+		SourceAccount: minion.BotAccount.GetAccountID(),
+		Destination:   destAddress,
+		Asset:         txnbuild.NativeAsset{},
+		Amount:        minion.StartingBalance,
+	}
+	tx, err := txnbuild.NewTransaction(
+		txnbuild.TransactionParams{
+			SourceAccount:        minion.Account,
+			IncrementSequenceNum: true,
+			Operations:           []txnbuild.Operation{&paymentOp},
+			BaseFee:              minion.BaseFee,
+			Preconditions:        txnbuild.Preconditions{TimeBounds: txnbuild.NewInfiniteTimeout()},
+		},
+	)
 	if err != nil {
-		return [32]byte{}, "", errors.Wrap(err, "incrementing minion seq")
+		return [32]byte{}, "", errors.Wrap(err, "unable to build tx")
 	}
+
+	tx, err = tx.Sign(minion.Network, minion.Keypair, minion.BotKeypair)
+	if err != nil {
+		return [32]byte{}, "", errors.Wrap(err, "unable to sign tx")
+	}
+
+	txe, err := tx.Base64()
+	if err != nil {
+		return [32]byte{}, "", errors.Wrap(err, "unable to serialize")
+	}
+
+	txh, err := tx.Hash(minion.Network)
+	if err != nil {
+		return [32]byte{}, "", errors.Wrap(err, "unable to hash")
+	}
+
 	return txh, txe, err
 }

services/friendbot/internal/minion_test.go

@@ -24,6 +24,10 @@ func TestMinion_NoChannelErrors(t *testing.T) {
 		return errors.New("could not refresh sequence")
 	}
 
+	mockCheckAccountExists := func(minion *Minion, hclient horizonclient.ClientInterface, destAddress string) (bool, string, error) {
+		return false, "0", nil
+	}
+
 	// Public key: GD25B4QI6KWVDWXDW25CIM7EKR6A6PBSWE2RCNSAC4NJQDQJXZJYMMKR
 	botSeed := "SCWNLYELENPBXN46FHYXETT5LJCYBZD5VUQQVW4KZPHFO2YTQJUWT4D5"
 	botKeypair, err := keypair.Parse(botSeed)
@@ -51,6 +55,7 @@ func TestMinion_NoChannelErrors(t *testing.T) {
 		StartingBalance:      "10000.00",
 		SubmitTransaction:    mockSubmitTransaction,
 		CheckSequenceRefresh: mockCheckSequenceRefresh,
+		CheckAccountExists:   mockCheckAccountExists,
 		BaseFee:              txnbuild.MinBaseFee,
 	}
 	fb := &Bot{Minions: []Minion{minion}}
@@ -89,6 +94,10 @@ func TestMinion_CorrectNumberOfTxSubmissions(t *testing.T) {
 		return nil
 	}
 
+	mockCheckAccountExists := func(minion *Minion, hclient horizonclient.ClientInterface, destAddress string) (bool, string, error) {
+		return false, "0", nil
+	}
+
 	// Public key: GD25B4QI6KWVDWXDW25CIM7EKR6A6PBSWE2RCNSAC4NJQDQJXZJYMMKR
 	botSeed := "SCWNLYELENPBXN46FHYXETT5LJCYBZD5VUQQVW4KZPHFO2YTQJUWT4D5"
 	botKeypair, err := keypair.Parse(botSeed)
@@ -116,6 +125,7 @@ func TestMinion_CorrectNumberOfTxSubmissions(t *testing.T) {
 		StartingBalance:      "10000.00",
 		SubmitTransaction:    mockSubmitTransaction,
 		CheckSequenceRefresh: mockCheckSequenceRefresh,
+		CheckAccountExists:   mockCheckAccountExists,
 		BaseFee:              txnbuild.MinBaseFee,
 	}
 	fb := &Bot{Minions: []Minion{minion}}

services/friendbot/main.go

@@ -34,7 +34,6 @@ type Config struct {
 }
 
 func main() {
-
 	rootCmd := &cobra.Command{
 		Use:   "friendbot",
 		Short: "friendbot for the Stellar Test Network",
@@ -114,4 +113,8 @@ func registerProblems() {
 	accountExistsProblem := problem.BadRequest
 	accountExistsProblem.Detail = internal.ErrAccountExists.Error()
 	problem.RegisterError(internal.ErrAccountExists, accountExistsProblem)
+
+	accountFundedProblem := problem.BadRequest
+	accountFundedProblem.Detail = internal.ErrAccountFunded.Error()
+	problem.RegisterError(internal.ErrAccountFunded, accountFundedProblem)
 }