From a0bf2864d243693d79b8a7f1633e54048e8c1fda Mon Sep 17 00:00:00 2001
From: Alfonso Acosta <alfonso@stellar.org>
Date: Tue, 6 Apr 2021 15:39:27 +0200
Subject: [PATCH] Enable SEP23 parsing for MuxedAccounts (with separated
 functions)

---
 xdr/muxed_account.go | 91 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 90 insertions(+), 1 deletion(-)

diff --git a/xdr/muxed_account.go b/xdr/muxed_account.go
index 3a9e7c31fa..2b493f4599 100644
--- a/xdr/muxed_account.go
+++ b/xdr/muxed_account.go
@@ -22,7 +22,7 @@ func MustMuxedAddressPtr(address string) *MuxedAccount {
 }
 
 // SetAddress modifies the receiver, setting it's value to the MuxedAccount form
-// of the provided address.
+// of the provided G-address.
 func (m *MuxedAccount) SetAddress(address string) error {
 	if m == nil {
 		return nil
@@ -47,6 +47,95 @@ func (m *MuxedAccount) SetAddress(address string) error {
 
 }
 
+// SetAddressWithSEP23 modifies the receiver, setting it's value to the MuxedAccount form
+// of the provided strkey G-address or M-address, as described in SEP23.
+func (m *MuxedAccount) SetAddressWithSEP23(address string) error {
+	if m == nil {
+		return nil
+	}
+
+	switch len(address) {
+	case 56:
+		return m.SetAddress(address)
+	case 69:
+		raw, err := strkey.Decode(strkey.VersionByteMuxedAccount, address)
+		if err != nil {
+			return err
+		}
+		if len(raw) != 40 {
+			return errors.New("invalid muxed address")
+		}
+		var muxed MuxedAccountMed25519
+		if err = muxed.Id.UnmarshalBinary(raw[:8]); err != nil {
+			return err
+		}
+		copy(muxed.Ed25519[:], raw[8:])
+		*m, err = NewMuxedAccount(CryptoKeyTypeKeyTypeMuxedEd25519, muxed)
+		return err
+	default:
+		return errors.New("invalid address")
+	}
+
+}
+
+// SEP23AddressToMuxedAccount returns an MuxedAccount for a given address string
+// or SEP23 M-address.
+// If the address is not valid the error returned will not be nil
+func SEP23AddressToMuxedAccount(address string) (MuxedAccount, error) {
+	result := MuxedAccount{}
+	err := result.SetAddressWithSEP23(address)
+
+	return result, err
+}
+
+// Address returns the strkey-encoded form of this MuxedAccount. In particular, it will
+// return an M- strkey representation for CryptoKeyTypeKeyTypeMuxedEd25519 variants of the account
+// (according to SEP23). This method will panic if the MuxedAccount is backed by a public key of an
+// unknown type.
+func (m *MuxedAccount) SEP23Address() string {
+	address, err := m.GetSEP23Address()
+	if err != nil {
+		panic(err)
+	}
+	return address
+}
+
+// GetAddress returns the strkey-encoded form of this MuxedAccount. In particular, it will
+// return an M-strkey representation for CryptoKeyTypeKeyTypeMuxedEd25519 variants of the account
+// (according to SEP23). In addition it will return an error if the MuxedAccount is backed by a
+// public key of an unknown type.
+func (m *MuxedAccount) GetSEP23Address() (string, error) {
+	if m == nil {
+		return "", nil
+	}
+
+	raw := make([]byte, 0, 40)
+	switch m.Type {
+	case CryptoKeyTypeKeyTypeEd25519:
+		ed, ok := m.GetEd25519()
+		if !ok {
+			return "", fmt.Errorf("Could not get Ed25519")
+		}
+		raw = append(raw, ed[:]...)
+		return strkey.Encode(strkey.VersionByteAccountID, raw)
+	case CryptoKeyTypeKeyTypeMuxedEd25519:
+		ed, ok := m.GetMed25519()
+		if !ok {
+			return "", fmt.Errorf("Could not get Med25519")
+		}
+		idBytes, err := ed.Id.MarshalBinary()
+		if err != nil {
+			return "", fmt.Errorf("Could not marshal ID")
+		}
+		raw = append(raw, idBytes...)
+		raw = append(raw, ed.Ed25519[:]...)
+		return strkey.Encode(strkey.VersionByteMuxedAccount, raw)
+	default:
+		return "", fmt.Errorf("Unknown muxed account type: %v", m.Type)
+	}
+
+}
+
 // ToAccountId transforms a MuxedAccount to an AccountId, dropping the
 // memo Id if necessary
 func (m MuxedAccount) ToAccountId() AccountId {