From f9bce4835975fb9a5a2e25c6c077f49fa5c2b78f Mon Sep 17 00:00:00 2001
From: Haw Loeung <haw.loeung@canonical.com>
Date: Sun, 17 Sep 2023 15:00:09 +1000
Subject: [PATCH] Optimise regex usage by switching to static initialisation

---
 mm-go-irckit/userbridge.go | 33 +++++++++++++++++++--------------
 1 file changed, 19 insertions(+), 14 deletions(-)

diff --git a/mm-go-irckit/userbridge.go b/mm-go-irckit/userbridge.go
index e1fa2732..730e85ea 100644
--- a/mm-go-irckit/userbridge.go
+++ b/mm-go-irckit/userbridge.go
@@ -1184,26 +1184,31 @@ func (u *User) formatCodeBlockText(text string, prefix string, codeBlockBackTick
 	return text, codeBlockBackTick, codeBlockTilde, lexer
 }
 
-func md2irc(msg string) string {
-	var re *regexp.Regexp
+// Use static initialisation to optimise.
+// Bold      0x02  **   (**text**)
+var boldStartRegExp = regexp.MustCompile(`([\s^]*)(?:(?:\*\*)|(?:\_\_)){1}(\S)`)
+var boldEndRegExp = regexp.MustCompile(`(\S)(?:(?:\*\*)|(?:\_\_)){1}([\s$]*)`)
+
+// Italics   0x1D  _    (_text_)
+var italicsStartRegExp = regexp.MustCompile(`([\s^]*)(?:[\*\_]{1})(\S)`)
+var italicsEndRegExp = regexp.MustCompile(`(\S)(?:_)([\s$]*)`)
 
+// Monospace 0x11  `    (`text`)
+var monospaceStartRegExp = regexp.MustCompile(`([\s^]*)(?:\x60{1})(\S)`)
+var monospaceEndRegExp = regexp.MustCompile(`(\S)(?:\x60{1})([\s$]*)`)
+
+func md2irc(msg string) string {
 	// Bold      0x02  **   (**text**)
-	re = regexp.MustCompile(`([\s^]*)(?:(?:\*\*)|(?:\_\_)){1}(\S)`)
-	msg = re.ReplaceAllString(msg, "$1\x02$2")
-	re = regexp.MustCompile(`(\S)(?:(?:\*\*)|(?:\_\_)){1}([\s$]*)`)
-	msg = re.ReplaceAllString(msg, "$1\x02$2")
+	msg = boldStartRegExp.ReplaceAllString(msg, "$1\x02$2")
+	msg = boldEndRegExp.ReplaceAllString(msg, "$1\x02$2")
 
 	// Italics   0x1D  _    (_text_)
-	re = regexp.MustCompile(`([\s^]*)(?:[\*\_]{1})(\S)`)
-	msg = re.ReplaceAllString(msg, "$1\x1d$2")
-	re = regexp.MustCompile(`(\S)(?:_)([\s$]*)`)
-	msg = re.ReplaceAllString(msg, "$1\x1d$2")
+	msg = italicsStartRegExp.ReplaceAllString(msg, "$1\x1d$2")
+	msg = italicsEndRegExp.ReplaceAllString(msg, "$1\x1d$2")
 
 	// Monospace 0x11  `    (`text`)
-	re = regexp.MustCompile(`([\s^]*)(?:\x60{1})(\S)`)
-	msg = re.ReplaceAllString(msg, "$1\x11$2")
-	re = regexp.MustCompile(`(\S)(?:\x60{1})([\s$]*)`)
-	msg = re.ReplaceAllString(msg, "$1\x11$2")
+	msg = monospaceStartRegExp.ReplaceAllString(msg, "$1\x11$2")
+	msg = monospaceEndRegExp.ReplaceAllString(msg, "$1\x11$2")
 
 	return msg
 }