format: add method to quote string in markdown inline code

format/htmlparser.go

@@ -187,25 +187,6 @@ func (parser *HTMLParser) listToString(node *html.Node, ctx Context) string {
 	return strings.Join(children, "\n")
 }
 
-func LongestSequence(in string, of rune) int {
-	currentSeq := 0
-	maxSeq := 0
-	for _, chr := range in {
-		if chr == of {
-			currentSeq++
-		} else {
-			if currentSeq > maxSeq {
-				maxSeq = currentSeq
-			}
-			currentSeq = 0
-		}
-	}
-	if currentSeq > maxSeq {
-		maxSeq = currentSeq
-	}
-	return maxSeq
-}
-
 func (parser *HTMLParser) basicFormatToString(node *html.Node, ctx Context) string {
 	str := parser.nodeToTagAwareString(node.FirstChild, ctx)
 	switch node.Data {
@@ -232,8 +213,7 @@ func (parser *HTMLParser) basicFormatToString(node *html.Node, ctx Context) stri
 		if parser.MonospaceConverter != nil {
 			return parser.MonospaceConverter(str, ctx)
 		}
-		surround := strings.Repeat("`", LongestSequence(str, '`')+1)
-		return fmt.Sprintf("%s%s%s", surround, str, surround)
+		return SafeMarkdownCode(str)
 	}
 	return str
 }

format/markdown.go

@@ -14,6 +14,7 @@ import (
 	"github.com/yuin/goldmark"
 	"github.com/yuin/goldmark/extension"
 	"github.com/yuin/goldmark/renderer/html"
+	"go.mau.fi/util/exstrings"
 
 	"maunium.net/go/mautrix/event"
 	"maunium.net/go/mautrix/format/mdext"
@@ -49,6 +50,19 @@ func EscapeMarkdown(text string) string {
 	return text
 }
 
+func SafeMarkdownCode(text string) string {
+	text = strings.ReplaceAll(text, "\n", " ")
+	backtickCount := exstrings.LongestSequenceOf(text, '`')
+	if backtickCount == 0 {
+		return fmt.Sprintf("`%s`", text)
+	}
+	quotes := strings.Repeat("`", backtickCount+1)
+	if text[0] == '`' || text[len(text)-1] == '`' {
+		return fmt.Sprintf("%s %s %s", quotes, text, quotes)
+	}
+	return fmt.Sprintf("%s%s%s", quotes, text, quotes)
+}
+
 func RenderMarkdownCustom(text string, renderer goldmark.Markdown) event.MessageEventContent {
 	var buf strings.Builder
 	err := renderer.Convert([]byte(text), &buf)

format/markdown_test.go

@@ -196,3 +196,18 @@ func TestRenderMarkdown_CustomEmoji(t *testing.T) {
 		assert.Equal(t, html, rendered, "with input %q", markdown)
 	}
 }
+
+var codeTests = map[string]string{
+	"meow":      "`meow`",
+	"me`ow":     "``me`ow``",
+	"`me`ow":    "`` `me`ow ``",
+	"me`ow`":    "`` me`ow` ``",
+	"`meow`":    "`` `meow` ``",
+	"`````````": "`````````` ````````` ``````````",
+}
+
+func TestSafeMarkdownCode(t *testing.T) {
+	for input, expected := range codeTests {
+		assert.Equal(t, expected, format.SafeMarkdownCode(input), "with input %q", input)
+	}
+}

go.mod

@@ -18,7 +18,7 @@ require (
 	github.com/tidwall/gjson v1.18.0
 	github.com/tidwall/sjson v1.2.5
 	github.com/yuin/goldmark v1.7.10
-	go.mau.fi/util v0.8.6
+	go.mau.fi/util v0.8.7-0.20250427215252-d2d18a7e463c
 	go.mau.fi/zeroconfig v0.1.3
 	golang.org/x/crypto v0.37.0
 	golang.org/x/exp v0.0.0-20250408133849-7e4ce0ab07d0

go.sum

@@ -53,8 +53,8 @@ github.com/tidwall/sjson v1.2.5 h1:kLy8mja+1c9jlljvWTlSazM7cKDRfJuR/bOJhcY5NcY=
 github.com/tidwall/sjson v1.2.5/go.mod h1:Fvgq9kS/6ociJEDnK0Fk1cpYF4FIW6ZF7LAe+6jwd28=
 github.com/yuin/goldmark v1.7.10 h1:S+LrtBjRmqMac2UdtB6yyCEJm+UILZ2fefI4p7o0QpI=
 github.com/yuin/goldmark v1.7.10/go.mod h1:ip/1k0VRfGynBgxOz0yCqHrbZXhcjxyuS66Brc7iBKg=
-go.mau.fi/util v0.8.6 h1:AEK13rfgtiZJL2YsNK+W4ihhYCuukcRom8WPP/w/L54=
-go.mau.fi/util v0.8.6/go.mod h1:uNB3UTXFbkpp7xL1M/WvQks90B/L4gvbLpbS0603KOE=
+go.mau.fi/util v0.8.7-0.20250427215252-d2d18a7e463c h1:qfJyMZq1pPyuXKoVWwHs6OmR9CzO3pHFRPYT/QpaaaA=
+go.mau.fi/util v0.8.7-0.20250427215252-d2d18a7e463c/go.mod h1:uNB3UTXFbkpp7xL1M/WvQks90B/L4gvbLpbS0603KOE=
 go.mau.fi/zeroconfig v0.1.3 h1:As9wYDKmktjmNZW5i1vn8zvJlmGKHeVxHVIBMXsm4kM=
 go.mau.fi/zeroconfig v0.1.3/go.mod h1:NcSJkf180JT+1IId76PcMuLTNa1CzsFFZ0nBygIQM70=
 golang.org/x/crypto v0.37.0 h1:kJNSjF/Xp7kU0iB2Z+9viTPMW4EqqsrywMXLJOOsXSE=