From e04b001d8bdb3b19db5ab9f510e8a4b5bc92039a Mon Sep 17 00:00:00 2001
From: Nikos Filippakis <me@nfil.dev>
Date: Tue, 16 Jun 2020 19:27:04 +0200
Subject: [PATCH] Use the state store to retrieve room joined users

Signed-off-by: Nikos Filippakis <me@nfil.dev>
---
 clients/bot_client.go  |  6 +-----
 clients/state_store.go | 25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/clients/bot_client.go b/clients/bot_client.go
index 0573e29..6752d2e 100644
--- a/clients/bot_client.go
+++ b/clients/bot_client.go
@@ -75,14 +75,10 @@ func (botClient *BotClient) SendMessageEvent(content interface{}, roomID id.Room
 			return err
 		} else if sess == nil || sess.Expired() || !sess.Shared {
 			// No error but valid, shared session does not exist
-			membs, err := botClient.client.JoinedMembers(roomID)
+			memberIDs, err := botClient.stateStore.GetJoinedMembers(roomID)
 			if err != nil {
 				return err
 			}
-			memberIDs := make([]id.UserID, 0, len(membs.Joined))
-			for member := range membs.Joined {
-				memberIDs = append(memberIDs, member)
-			}
 			// Share group session with room members
 			if err = olmMachine.ShareGroupSession(roomID, memberIDs); err != nil {
 				return err
diff --git a/clients/state_store.go b/clients/state_store.go
index 0be3a21..fa95a74 100644
--- a/clients/state_store.go
+++ b/clients/state_store.go
@@ -1,6 +1,8 @@
 package clients
 
 import (
+	"errors"
+
 	"maunium.net/go/mautrix"
 	"maunium.net/go/mautrix/event"
 	"maunium.net/go/mautrix/id"
@@ -52,3 +54,26 @@ func (ss *NebStateStore) UpdateStateStore(resp *mautrix.RespSync) {
 		}
 	}
 }
+
+// GetJoinedMembers returns a list of members that are currently in a room.
+func (ss *NebStateStore) GetJoinedMembers(roomID id.RoomID) ([]id.UserID, error) {
+	joinedMembers := make([]id.UserID, 0)
+	room := ss.Storer.LoadRoom(roomID)
+	if room == nil {
+		return nil, errors.New("unknown roomID")
+	}
+	memberEvents := room.State[event.StateMember]
+	if memberEvents == nil {
+		return nil, errors.New("no state member events found")
+	}
+	for stateKey, stateEvent := range memberEvents {
+		if stateEvent == nil {
+			continue
+		}
+		stateEvent.Content.ParseRaw(event.StateMember)
+		if stateEvent.Content.AsMember().Membership == event.MembershipJoin {
+			joinedMembers = append(joinedMembers, id.UserID(stateKey))
+		}
+	}
+	return joinedMembers, nil
+}