Fix DMs being marked as with the current user ("me")

Whilst testing various DM paths, @lukebarnard1 found that there were
many failures to add the room as a DM against the correct user. It
turned out most of the failures seen were because the user chosen
was the current user. If the user accepted an invite it would often
be marked as with themselves because we chose the sender of the
join event as the DM user.

This fix makes the DM room setting process the same for both the
inviting client and the invited client. A RoomState.members
event causes the DM room state to be set in the room, regardless
of whether we are currently `joining` (see previous impl.)

The two cases for setting a DM are:
 - this user accepting an invite with is_direct
 - this user inviting someone with is_direct

This should handle all cases for setting DM state.

src/components/structures/RoomView.js

@@ -678,21 +678,40 @@ module.exports = React.createClass({
         // refresh the conf call notification state
         this._updateConfCallNotification();
 
-        // if we are now a member of the room, where we were not before, that
-        // means we have finished joining a room we were previously peeking
-        // into.
-        const me = MatrixClientPeg.get().credentials.userId;
-        if (this.state.joining && this.state.room.hasMembershipState(me, "join")) {
-            // Having just joined a room, check to see if it looks like a DM room, and if so,
-            // mark it as one. This is to work around the fact that some clients don't support
-            // is_direct. We should remove this once they do.
         const me = this.state.room.getMember(MatrixClientPeg.get().credentials.userId);
-            if (Rooms.looksLikeDirectMessageRoom(this.state.room, me)) {
+        if (!me || me.membership !== "join") {
-                // XXX: There's not a whole lot we can really do if this fails: at best
+            return;
-                // perhaps we could try a couple more times, but since it's a temporary
-                // compatability workaround, let's not bother.
-                Rooms.setDMRoom(this.state.room.roomId, me.events.member.getSender()).done();
         }
+
+        // The user may have accepted an invite with is_direct set
+        if (me.events.member.getPrevContent().membership === "invite" &&
+            me.events.member.getPrevContent().is_direct
+        ) {
+            // This is a DM with the sender of the invite event (which we assume
+            // preceded the join event)
+            Rooms.setDMRoom(
+                this.state.room.roomId,
+                me.events.member.getUnsigned().prev_sender,
+            );
+            return;
+        }
+
+        const invitedMembers = this.state.room.getMembersWithMembership("invite");
+        const joinedMembers = this.state.room.getMembersWithMembership("join");
+
+        // There must be one invited member and one joined member
+        if (invitedMembers.length !== 1 || joinedMembers.length !== 1) {
+            return;
+        }
+
+        // The user may have sent an invite with is_direct sent
+        const other = invitedMembers[0];
+        if (other &&
+            other.membership === "invite" &&
+            other.events.member.getContent().is_direct
+        ) {
+            Rooms.setDMRoom(this.state.room.roomId, other.userId);
+            return;
         }
     }, 500),
 
@@ -826,18 +845,6 @@ module.exports = React.createClass({
                 action: 'join_room',
                 opts: { inviteSignUrl: signUrl },
             });
-
-            // if this is an invite and has the 'direct' hint set, mark it as a DM room now.
-            if (this.state.room) {
-                const me = this.state.room.getMember(MatrixClientPeg.get().credentials.userId);
-                if (me && me.membership == 'invite') {
-                    if (me.events.member.getContent().is_direct) {
-                        // The 'direct' hint is there, so declare that this is a DM room for
-                        // whoever invited us.
-                        return Rooms.setDMRoom(this.state.room.roomId, me.events.member.getSender());
-                    }
-                }
-            }
             return Promise.resolve();
         });
     },