From 62f623403fd6bc793f299055f60aa6d44f138a09 Mon Sep 17 00:00:00 2001
From: Haw Loeung <haw.loeung@canonical.com>
Date: Sat, 30 Sep 2023 06:25:02 +1000
Subject: [PATCH] Use static initialisation for regular expressions to optimize
 (#551)

---
 bridge/mattermost/mattermost.go |  5 +++--
 mm-go-irckit/server_commands.go | 15 +++++++++------
 mm-go-irckit/user.go            |  9 ++++++---
 3 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/bridge/mattermost/mattermost.go b/bridge/mattermost/mattermost.go
index 361c3555..a0496644 100644
--- a/bridge/mattermost/mattermost.go
+++ b/bridge/mattermost/mattermost.go
@@ -840,6 +840,8 @@ func (m *Mattermost) addParentMsg(parentID string, msg string, newLen int, uncou
 	return strings.TrimRight(msg, "\n") + replyMessage, nil
 }
 
+var validIRCNickRegExp = regexp.MustCompile("^[a-zA-Z0-9_]*$")
+
 //nolint:funlen,gocognit,gocyclo,cyclop,forcetypeassert
 func (m *Mattermost) handleWsActionPost(rmsg *model.WebSocketEvent) {
 	var data model.Post
@@ -890,8 +892,7 @@ func (m *Mattermost) handleWsActionPost(rmsg *model.WebSocketEvent) {
 	if overrideUsername != "" {
 		logger.Debugf("found override username %s", overrideUsername)
 		// only allow valid irc nicks
-		re := regexp.MustCompile("^[a-zA-Z0-9_]*$")
-		if re.MatchString(overrideUsername) {
+		if validIRCNickRegExp.MatchString(overrideUsername) {
 			ghost.Nick = overrideUsername
 			ghost.Me = false
 		}
diff --git a/mm-go-irckit/server_commands.go b/mm-go-irckit/server_commands.go
index 2f0c69be..c3b30794 100644
--- a/mm-go-irckit/server_commands.go
+++ b/mm-go-irckit/server_commands.go
@@ -460,9 +460,10 @@ func CmdPrivMsg(s Server, u *User, msg *irc.Message) error {
 	return s.EncodeMessage(u, irc.ERR_NOSUCHNICK, msg.Params, "No such nick/channel")
 }
 
+var parseReactionToMsgRegExp = regexp.MustCompile(`^\@\@([0-9a-f]{3}|[0-9a-z]{26})\s+([\-\+]):(\S+):\s*$`)
+
 func parseReactionToMsg(u *User, msg *irc.Message, channelID string) bool {
-	re := regexp.MustCompile(`^\@\@([0-9a-f]{3}|[0-9a-z]{26})\s+([\-\+]):(\S+):\s*$`)
-	matches := re.FindStringSubmatch(msg.Trailing)
+	matches := parseReactionToMsgRegExp.FindStringSubmatch(msg.Trailing)
 	if len(matches) != 4 {
 		return false
 	}
@@ -503,9 +504,10 @@ func parseReactionToMsg(u *User, msg *irc.Message, channelID string) bool {
 	return true
 }
 
+var parseModifyMsgRegExp = regexp.MustCompile(`^s(\/(?:[0-9a-f]{3}|[0-9a-z]{26}|!!)?\/)(.*)`)
+
 func parseModifyMsg(u *User, msg *irc.Message, channelID string) bool {
-	re := regexp.MustCompile(`^s(\/(?:[0-9a-f]{3}|[0-9a-z]{26}|!!)?\/)(.*)`)
-	matches := re.FindStringSubmatch(msg.Trailing)
+	matches := parseModifyMsgRegExp.FindStringSubmatch(msg.Trailing)
 	text := msg.Trailing
 
 	// only two so s/xxx/ which means a delete
@@ -576,9 +578,10 @@ func parseModifyMsg(u *User, msg *irc.Message, channelID string) bool {
 	return true
 }
 
+var parseThreadIDRegExp = regexp.MustCompile(`(?s)^\@\@(?:(!!|[0-9a-f]{3}|[0-9a-z]{26})\s)(.*)`)
+
 func parseThreadID(u *User, msg *irc.Message, channelID string) (string, string) {
-	re := regexp.MustCompile(`(?s)^\@\@(?:(!!|[0-9a-f]{3}|[0-9a-z]{26})\s)(.*)`)
-	matches := re.FindStringSubmatch(msg.Trailing)
+	matches := parseThreadIDRegExp.FindStringSubmatch(msg.Trailing)
 	if len(matches) == 0 {
 		return "", ""
 	}
diff --git a/mm-go-irckit/user.go b/mm-go-irckit/user.go
index 239123b7..cf9eb2fc 100644
--- a/mm-go-irckit/user.go
+++ b/mm-go-irckit/user.go
@@ -153,6 +153,11 @@ func (u *User) Encode(msgs ...*irc.Message) (err error) {
 	return nil
 }
 
+var (
+	replyRegExp  = regexp.MustCompile(`\@\@(?:[0-9a-z]{26}|[0-9a-f]{3}|!!)\s`)
+	modifyRegExp = regexp.MustCompile(`^s/(?:[0-9a-z]{26}|[0-9a-f]{3}|!!)?/`)
+)
+
 // Decode will receive and return a decoded message, or an error.
 // nolint:funlen,gocognit,gocyclo
 func (u *User) Decode() {
@@ -181,9 +186,7 @@ func (u *User) Decode() {
 					// start timer now
 					t.Reset(time.Duration(bufferTimeout) * time.Millisecond)
 				} else {
-					replyRe := regexp.MustCompile(`\@\@(?:[0-9a-z]{26}|[0-9a-f]{3}|!!)\s`)
-					modifyRe := regexp.MustCompile(`^s/(?:[0-9a-z]{26}|[0-9a-f]{3}|!!)?/`)
-					if strings.HasPrefix(msg.Trailing, "\x01ACTION") || replyRe.MatchString(msg.Trailing) || modifyRe.MatchString(msg.Trailing) {
+					if strings.HasPrefix(msg.Trailing, "\x01ACTION") || replyRegExp.MatchString(msg.Trailing) || modifyRegExp.MatchString(msg.Trailing) {
 						// flush buffer
 						logger.Debug("flushing buffer because of /me, replies to threads, and message modifications")
 						u.BufferedMsg.Trailing = strings.TrimSpace(u.BufferedMsg.Trailing)