Fail immediately with ERR_BADCHANMASK when clients ignore TARGMAX

No need to send this to the homeserver, this is very likely to be a client
error, so we should show a helpful message instead of the generic error
from the homeserver

Author: progval

lib/irc/handler.ex

@@ -799,21 +799,32 @@ defmodule M51.IrcConn.Handler do
         })
 
       {"JOIN", [channel | _]} ->
-        case M51.MatrixClient.Client.join_room(matrix_client, channel) do
-          {:ok, _room_id} ->
-            # Should we send a JOIN?
-            send_ack.()
+        if String.contains?(channel, ",") do
+          # ERR_BADCHANMASK
+          send_numeric.(
+            "476",
+            [
+              channel,
+              "commas are not allowed in channel names (ISUPPORT MAXTARGETS/TARGMAX not implemented?)"
+            ]
+          )
+        else
+          case M51.MatrixClient.Client.join_room(matrix_client, channel) do
+            {:ok, _room_id} ->
+              # Should we send a JOIN?
+              send_ack.()
 
-          {:error, :already_joined, _room_id} ->
-            send_ack.()
+            {:error, :already_joined, _room_id} ->
+              send_ack.()
 
-          {:error, :banned_or_missing_invite, message} ->
-            # ERR_BANNEDFROMCHAN
-            send_numeric.("474", [channel, "Cannot join channel: " <> message])
+            {:error, :banned_or_missing_invite, message} ->
+              # ERR_BANNEDFROMCHAN
+              send_numeric.("474", [channel, "Cannot join channel: " <> message])
 
-          {:error, :unknown, message} ->
-            # ERR_NOSUCHCHANNEL
-            send_numeric.("403", [channel, "Cannot join channel: " <> message])
+            {:error, :unknown, message} ->
+              # ERR_NOSUCHCHANNEL
+              send_numeric.("403", [channel, "Cannot join channel: " <> message])
+          end
         end
 
       {"JOIN", _} ->

test/irc/handler_test.exs

@@ -429,6 +429,16 @@ defmodule M51.IrcConn.HandlerTest do
     assert_line("@label=abcd ACK\r\n")
   end
 
+  test "joining multiple rooms", %{handler: handler} do
+    do_connection_registration(handler)
+
+    send(handler, cmd("@label=abcd JOIN #room1:example.org,#room2:example.org"))
+
+    assert_line(
+      "@label=abcd :server. 476 foo:example.org #room1:example.org,#room2:example.org :commas are not allowed in channel names (ISUPPORT MAXTARGETS/TARGMAX not implemented?)\r\n"
+    )
+  end
+
   test "ignores TAGMSG", %{handler: handler} do
     do_connection_registration(handler)
 
@@ -946,7 +956,6 @@ defmodule M51.IrcConn.HandlerTest do
 
     assert_line("BATCH :-#{batch_id}\r\n")
 
-
     send(handler, cmd("@label=l1 CHATHISTORY LATEST #chan * 2"))
     {batch_id, line} = assert_open_batch()
     assert line == "@label=l1 BATCH +#{batch_id} :chathistory\r\n"