From 83056c539613ab4059b74c429d1d2840ec1a28c3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ken-H=C3=A5vard=20Lieng?= <kk_998@hotmail.com>
Date: Fri, 16 Dec 2016 23:49:37 +0100
Subject: [PATCH] Prevent panicing when parsing invalid messages

---
 irc/message.go      | 8 +++++++-
 irc/message_test.go | 7 +++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/irc/message.go b/irc/message.go
index 6e0ad59f..dfec47de 100644
--- a/irc/message.go
+++ b/irc/message.go
@@ -19,7 +19,13 @@ func parseMessage(line string) *Message {
 
 	if strings.HasPrefix(line, ":") {
 		cmdStart = strings.Index(line, " ") + 1
-		msg.Prefix = line[1 : cmdStart-1]
+
+		if cmdStart > 0 {
+			msg.Prefix = line[1 : cmdStart-1]
+		} else {
+			// Invalid message
+			return &msg
+		}
 
 		if i := strings.Index(msg.Prefix, "!"); i > 0 {
 			msg.Nick = msg.Prefix[:i]
diff --git a/irc/message_test.go b/irc/message_test.go
index 2d66228a..9ea7b94f 100644
--- a/irc/message_test.go
+++ b/irc/message_test.go
@@ -71,3 +71,10 @@ func TestParseMessage(t *testing.T) {
 		assert.Equal(t, tc.expected, parseMessage(tc.input))
 	}
 }
+
+func TestBadMessagePanic(t *testing.T) {
+	parseMessage(":user\r\n")
+	parseMessage(":\r\n")
+	parseMessage(":")
+	parseMessage("")
+}