From b66c2627dc085a21c3968cc9f306b10d92cde76d Mon Sep 17 00:00:00 2001
From: Sam Wedgwood <sam@wedgwood.dev>
Date: Tue, 1 Aug 2023 11:27:56 +0100
Subject: [PATCH] use pointers for querying sender ID

---
 performinvite.go      |  4 ++--
 performinvite_test.go |  5 +++--
 spec/senderid.go      | 13 ++++++++++++-
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/performinvite.go b/performinvite.go
index 6b4c3168..7f591a29 100644
--- a/performinvite.go
+++ b/performinvite.go
@@ -96,8 +96,8 @@ func PerformInvite(ctx context.Context, input PerformInviteInput, fedClient Fede
 		return nil, err
 	}
 
-	if invitedSenderID != "" {
-		err = abortIfAlreadyJoined(ctx, input.RoomID, invitedSenderID, input.MembershipQuerier)
+	if invitedSenderID != nil {
+		err = abortIfAlreadyJoined(ctx, input.RoomID, *invitedSenderID, input.MembershipQuerier)
 		if err != nil {
 			return nil, err
 		}
diff --git a/performinvite_test.go b/performinvite_test.go
index 35a8d937..f663da0f 100644
--- a/performinvite_test.go
+++ b/performinvite_test.go
@@ -13,8 +13,9 @@ import (
 	"golang.org/x/crypto/ed25519"
 )
 
-func SenderIDForUserTest(roomID spec.RoomID, userID spec.UserID) (spec.SenderID, error) {
-	return spec.SenderID(userID.String()), nil
+func SenderIDForUserTest(roomID spec.RoomID, userID spec.UserID) (*spec.SenderID, error) {
+	senderID := spec.SenderID(userID.String())
+	return &senderID, nil
 }
 
 func CreateSenderID(ctx context.Context, userID spec.UserID, roomID spec.RoomID, roomVersion string) (spec.SenderID, ed25519.PrivateKey, error) {
diff --git a/spec/senderid.go b/spec/senderid.go
index 44954c15..76622faf 100644
--- a/spec/senderid.go
+++ b/spec/senderid.go
@@ -23,7 +23,7 @@ import (
 type SenderID string
 
 type UserIDForSender func(roomID RoomID, senderID SenderID) (*UserID, error)
-type SenderIDForUser func(roomID RoomID, userID UserID) (SenderID, error)
+type SenderIDForUser func(roomID RoomID, userID UserID) (*SenderID, error)
 
 // CreateSenderID is a function used to create the pseudoID private key.
 type CreateSenderID func(ctx context.Context, userID UserID, roomID RoomID, roomVersion string) (SenderID, ed25519.PrivateKey, error)
@@ -42,3 +42,14 @@ func (s SenderID) RawBytes() (res Base64Bytes, err error) {
 	}
 	return res, nil
 }
+
+func (s SenderID) IsUserID() bool {
+	// Key is base64, @ is not a valid base64 char
+	// So if string starts with @, then this sender ID must
+	// be a user ID
+	return string(s)[0] == '@'
+}
+
+func (s SenderID) IsPseudoID() bool {
+	return !s.IsUserID()
+}