From 3f005d481d431d1260f70fccba87709b44a0bf6b Mon Sep 17 00:00:00 2001
From: Simon Ser <contact@emersion.fr>
Date: Mon, 15 Mar 2021 23:11:42 +0100
Subject: [PATCH] Properly handle all ISUPPORT negations

---
 upstream.go | 35 ++++++++++++++++++++++-------------
 1 file changed, 22 insertions(+), 13 deletions(-)

diff --git a/upstream.go b/upstream.go
index 640c673..c0c86b8 100644
--- a/upstream.go
+++ b/upstream.go
@@ -634,20 +634,29 @@ func (uc *upstreamConn) handleMessage(msg *irc.Message) error {
 				delete(uc.isupport, parameter)
 			}
 
-			if !negate && hasValue {
-				// TODO: reset to defaults when the token is negated
-				switch parameter {
-				case "CHANMODES":
-					if err := uc.handleChanModes(value); err != nil {
-						return err
-					}
-				case "CHANTYPES":
-					uc.availableChannelTypes = value
-				case "PREFIX":
-					if err := uc.handleMemberships(value); err != nil {
-						return err
-					}
+			var err error
+			switch parameter {
+			case "CHANMODES":
+				if !negate {
+					err = uc.handleChanModes(value)
+				} else {
+					uc.availableChannelModes = stdChannelModes
 				}
+			case "CHANTYPES":
+				if !negate {
+					uc.availableChannelTypes = value
+				} else {
+					uc.availableChannelTypes = stdChannelTypes
+				}
+			case "PREFIX":
+				if !negate {
+					err = uc.handleMemberships(value)
+				} else {
+					uc.availableMemberships = stdMemberships
+				}
+			}
+			if err != nil {
+				return err
 			}
 		}
 	case "BATCH":