Clear existing IRC event handlers before connecting to new ones

Clear IRC event handlers that we will be registering for the new
connection before registering new handlers. This prevents duplicate
event handlers in the case where we are connecting via a BNC and are
seeing a reconnect. Attempting to clear handlers when none have been set
is a no-op.

Fixes #1564
Co-authored-by: Andreas Vögele <andreas@andreasvoegele.com>

bridge/irc/handlers.go

@@ -122,6 +122,17 @@ func (b *Birc) handleNewConnection(client *girc.Client, event girc.Event) {
 	i := b.i
 	b.Nick = event.Params[0]
 
+	b.Log.Debug("Clearing handlers before adding in case of BNC reconnect")
+	i.Handlers.Clear("PRIVMSG")
+	i.Handlers.Clear("CTCP_ACTION")
+	i.Handlers.Clear(girc.RPL_TOPICWHOTIME)
+	i.Handlers.Clear(girc.NOTICE)
+	i.Handlers.Clear("JOIN")
+	i.Handlers.Clear("PART")
+	i.Handlers.Clear("QUIT")
+	i.Handlers.Clear("KICK")
+	i.Handlers.Clear("INVITE")
+
 	i.Handlers.AddBg("PRIVMSG", b.handlePrivMsg)
 	i.Handlers.AddBg("CTCP_ACTION", b.handlePrivMsg)
 	i.Handlers.Add(girc.RPL_TOPICWHOTIME, b.handleTopicWhoTime)