Fix IRC invite bug (#177)

Author: Half-Shot

src/IRCBridge.ts

@@ -108,8 +108,22 @@ export class IRCBridge {
         return channel && channel.startsWith(this.config.channelPrefix);
     }
 
+    public async shouldInviteBot(roomId: string) {
+        try {
+            const currentMemberState = await this.mxClient.getRoomStateEvent(roomId, 'm.room.member', this.config.botUserId);
+            return !['join','invite'].includes(currentMemberState.membership);
+        } catch (ex) {
+            // return ex instanceof MatrixError && ex.errcode === "M_NOT_FOUND";
+            // MatrixError requires a newer version of the SDK (https://github.com/matrix-org/conference-bot/pull/163).
+            // Assume the bot isn't in the room.
+            return true;
+        }
+    }
+
     public async plumbChannelToRoom(channel: string, roomId: string) {
-        await this.mxClient.inviteUser(this.config.botUserId, roomId);
+        if (await this.shouldInviteBot(roomId)) {
+            await this.mxClient.inviteUser(this.config.botUserId, roomId);
+        }
         await this.ircClient.join(channel);
         const result = await this.executeCommand(`plumb ${roomId} ${this.config.serverName} ${channel}`);
         const resultText = result.content.body;