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Perf/precompile regex v2 #793

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41 changes: 27 additions & 14 deletions pkg/channels/telegram/telegram.go
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Original file line number Diff line number Diff line change
Expand Up @@ -511,6 +511,22 @@ func parseChatID(chatIDStr string) (int64, error) {
return id, err
}

// Pre-compiled regex patterns for markdownToTelegramHTML.
// Compiled once at package init, reused across all calls (regexp is goroutine-safe).
// This eliminates ~20 KB of heap allocation per outbound message.
var (
reHeader = regexp.MustCompile(`^#{1,6}\s+(.+)$`)
reBlockquote = regexp.MustCompile(`^>\s*(.*)$`)
reLink = regexp.MustCompile(`\[([^\]]+)\]\(([^)]+)\)`)
reBold = regexp.MustCompile(`\*\*(.+?)\*\*`)
reBoldAlt = regexp.MustCompile(`__(.+?)__`)
reItalic = regexp.MustCompile(`_([^_]+)_`)
reStrike = regexp.MustCompile(`~~(.+?)~~`)
reListItem = regexp.MustCompile(`^[-*]\s+`)
reCodeBlock = regexp.MustCompile("```[\\w]*\\n?([\\s\\S]*?)```")
reInlineCode = regexp.MustCompile("`([^`]+)`")
)

func markdownToTelegramHTML(text string) string {
if text == "" {
return ""
Expand All @@ -522,19 +538,18 @@ func markdownToTelegramHTML(text string) string {
inlineCodes := extractInlineCodes(text)
text = inlineCodes.text

text = regexp.MustCompile(`^#{1,6}\s+(.+)$`).ReplaceAllString(text, "$1")
text = reHeader.ReplaceAllString(text, "$1")

text = regexp.MustCompile(`^>\s*(.*)$`).ReplaceAllString(text, "$1")
text = reBlockquote.ReplaceAllString(text, "$1")

text = escapeHTML(text)

text = regexp.MustCompile(`\[([^\]]+)\]\(([^)]+)\)`).ReplaceAllString(text, `<a href="$2">$1</a>`)
text = reLink.ReplaceAllString(text, `<a href="$2">$1</a>`)

text = regexp.MustCompile(`\*\*(.+?)\*\*`).ReplaceAllString(text, "<b>$1</b>")
text = reBold.ReplaceAllString(text, "<b>$1</b>")

text = regexp.MustCompile(`__(.+?)__`).ReplaceAllString(text, "<b>$1</b>")
text = reBoldAlt.ReplaceAllString(text, "<b>$1</b>")

reItalic := regexp.MustCompile(`_([^_]+)_`)
text = reItalic.ReplaceAllStringFunc(text, func(s string) string {
match := reItalic.FindStringSubmatch(s)
if len(match) < 2 {
Expand All @@ -543,9 +558,9 @@ func markdownToTelegramHTML(text string) string {
return "<i>" + match[1] + "</i>"
})

text = regexp.MustCompile(`~~(.+?)~~`).ReplaceAllString(text, "<s>$1</s>")
text = reStrike.ReplaceAllString(text, "<s>$1</s>")

text = regexp.MustCompile(`^[-*]\s+`).ReplaceAllString(text, "• ")
text = reListItem.ReplaceAllString(text, "• ")

for i, code := range inlineCodes.codes {
escaped := escapeHTML(code)
Expand All @@ -570,16 +585,15 @@ type codeBlockMatch struct {
}

func extractCodeBlocks(text string) codeBlockMatch {
re := regexp.MustCompile("```[\\w]*\\n?([\\s\\S]*?)```")
matches := re.FindAllStringSubmatch(text, -1)
matches := reCodeBlock.FindAllStringSubmatch(text, -1)

codes := make([]string, 0, len(matches))
for _, match := range matches {
codes = append(codes, match[1])
}

i := 0
text = re.ReplaceAllStringFunc(text, func(m string) string {
text = reCodeBlock.ReplaceAllStringFunc(text, func(m string) string {
placeholder := fmt.Sprintf("\x00CB%d\x00", i)
i++
return placeholder
Expand All @@ -594,16 +608,15 @@ type inlineCodeMatch struct {
}

func extractInlineCodes(text string) inlineCodeMatch {
re := regexp.MustCompile("`([^`]+)`")
matches := re.FindAllStringSubmatch(text, -1)
matches := reInlineCode.FindAllStringSubmatch(text, -1)

codes := make([]string, 0, len(matches))
for _, match := range matches {
codes = append(codes, match[1])
}

i := 0
text = re.ReplaceAllStringFunc(text, func(m string) string {
text = reInlineCode.ReplaceAllStringFunc(text, func(m string) string {
placeholder := fmt.Sprintf("\x00IC%d\x00", i)
i++
return placeholder
Expand Down