xdr: Easily created MuxedAccount objects from a G-address and a memo ID.

txnbuild/transaction_test.go

@@ -4371,12 +4371,9 @@ func TestVerifyTxSignatureInvalid(t *testing.T) {
 
 func TestClaimableBalanceIds(t *testing.T) {
 	aKeys := keypair.MustParseFull("SC4REDCJNPFAYW4SMH44KNGO5JRDQ72G4HE6GILRBSICI3M2IUOC7AAL")
-	// TODO: Replace with
-	// xdr.MuxedAccountFromAccountId(aKeys.Address(), uint64(1234)).Address()
-	// once https://github.com/stellar/go/pull/3677 gets in
-	aMuxed := "MDUJNO4HVE4YCQHV7LINPWVDQJFSAPHHUNSTT64YRBCCRZ5UYUXAWAAAAAAAAAAE2IUOE"
-	aMuxedAccount := NewSimpleAccount(aMuxed, int64(5894915628204034))
+	A := "MDUJNO4HVE4YCQHV7LINPWVDQJFSAPHHUNSTT64YRBCCRZ5UYUXAWAAAAAAAAAAE2IUOE"
 	B := "GCACCFMIWJAHUUASSE2WC7V6VVDLYRLSJYZ3DJEXCG523FSHTNII6KOG"
+	aMuxedAccount := NewSimpleAccount(A, int64(5894915628204034))
 
 	// Create the operation and submit it in a transaction.
 	claimableBalanceEntry := CreateClaimableBalance{

xdr/muxed_account.go

@@ -21,6 +21,24 @@ func MustMuxedAddressPtr(address string) *MuxedAccount {
 	return &muxed
 }
 
+func MuxedAccountFromAccountId(gAddress string, id uint64) (MuxedAccount, error) {
+	bytes, err := strkey.Decode(strkey.VersionByteAccountID, gAddress)
+	if err != nil {
+		return MuxedAccount{}, err
+	}
+
+	var publicKey Uint256
+	copy(publicKey[:], bytes)
+
+	return NewMuxedAccount(
+		CryptoKeyTypeKeyTypeMuxedEd25519,
+		MuxedAccountMed25519{
+			Id:      Uint64(id),
+			Ed25519: publicKey,
+		},
+	)
+}
+
 // SetEd25519Address modifies the receiver, setting it's value to the MuxedAccount form
 // of the provided G-address. Unlike SetAddress(), it only supports G-addresses.
 func (m *MuxedAccount) SetEd25519Address(address string) error {
@@ -133,7 +151,30 @@ func (m *MuxedAccount) GetAddress() (string, error) {
 	default:
 		return "", fmt.Errorf("Unknown muxed account type: %v", m.Type)
 	}
+}
+
+// GetId retrieves the underlying memo ID if this is a fully muxed account. It
+// will return an error if the muxed account does not have a memo ID (i.e it's
+// of the key type Ed25519).
+func (m *MuxedAccount) GetId() (uint64, error) {
+	if m == nil {
+		return 0, nil
+	}
 
+	switch m.Type {
+	case CryptoKeyTypeKeyTypeEd25519:
+		return 0, errors.New("muxed account has no ID")
+
+	case CryptoKeyTypeKeyTypeMuxedEd25519:
+		ed, ok := m.GetMed25519()
+		if !ok {
+			return 0, errors.New("could not get Med25519")
+		}
+		return uint64(ed.Id), nil
+
+	default:
+		return 0, fmt.Errorf("Unknown muxed account type: %v", m.Type)
+	}
 }
 
 // ToAccountId transforms a MuxedAccount to an AccountId, dropping the

xdr/muxed_account_test.go

@@ -19,6 +19,8 @@ var _ = Describe("xdr.MuxedAccount#Get/SetAddress()", func() {
 		Expect(err).ShouldNot(HaveOccurred())
 		Expect(unmuxed.Type).To(Equal(CryptoKeyTypeKeyTypeEd25519))
 		Expect(*unmuxed.Ed25519).To(Equal(Uint256{63, 12, 52, 191, 147, 173, 13, 153, 113, 208, 76, 204, 144, 247, 5, 81, 28, 131, 138, 173, 151, 52, 164, 162, 251, 13, 122, 3, 252, 127, 232, 154}))
+		_, err = unmuxed.GetId()
+		Expect(err).Should(HaveOccurred())
 		muxedy := unmuxed.Address()
 		Expect(muxedy).To(Equal("GA7QYNF7SOWQ3GLR2BGMZEHXAVIRZA4KVWLTJJFC7MGXUA74P7UJVSGZ"))
 
@@ -29,17 +31,31 @@ var _ = Describe("xdr.MuxedAccount#Get/SetAddress()", func() {
 		Expect(muxed.Med25519.Id).To(Equal(Uint64(9223372036854775808)))
 		Expect(muxed.Med25519.Ed25519).To(Equal(*unmuxed.Ed25519))
 		muxedy = muxed.Address()
+		id, err := muxed.GetId()
+		Expect(id).To(Equal(uint64(9223372036854775808)))
 		Expect(muxedy).To(Equal("MA7QYNF7SOWQ3GLR2BGMZEHXAVIRZA4KVWLTJJFC7MGXUA74P7UJVAAAAAAAAAAAAAJLK"))
 
 		err = muxed.SetAddress("MA7QYNF7SOWQ3GLR2BGMZEHXAVIRZA4KVWLTJJFC7MGXUA74P7UJUAAAAAAAAAAAACJUQ")
 		Expect(err).ShouldNot(HaveOccurred())
 		Expect(muxed.Type).To(Equal(CryptoKeyTypeKeyTypeMuxedEd25519))
 		Expect(muxed.Med25519.Id).To(Equal(Uint64(0)))
 		Expect(muxed.Med25519.Ed25519).To(Equal(*unmuxed.Ed25519))
+		id, err = muxed.GetId()
+		Expect(id).To(Equal(uint64(0)))
 		muxedy = muxed.Address()
 		Expect(muxedy).To(Equal("MA7QYNF7SOWQ3GLR2BGMZEHXAVIRZA4KVWLTJJFC7MGXUA74P7UJUAAAAAAAAAAAACJUQ"))
 	})
 
+	It("returns a muxed account from an account ID and memo", func() {
+		accountId := "GA7QYNF7SOWQ3GLR2BGMZEHXAVIRZA4KVWLTJJFC7MGXUA74P7UJVSGZ"
+		expectedMuxedId := "MA7QYNF7SOWQ3GLR2BGMZEHXAVIRZA4KVWLTJJFC7MGXUA74P7UJUAAAAAAAAAABUTGI4"
+
+		muxedAccount, err := MuxedAccountFromAccountId(accountId, uint64(420))
+		Expect(err).ShouldNot(HaveOccurred())
+		Expect(muxedAccount.GetAddress()).To(Equal(expectedMuxedId))
+		Expect(muxedAccount.GetId()).To(Equal(uint64(420)))
+	})
+
 	It("returns an error when the strkey is invalid", func() {
 		var muxed MuxedAccount