X-Git-Url: http://git.giacomolli.uk/onechat/blobdiff_plain/1379d7d0d0173416237ddf8ebe820743d2cecfa6..de170709599e849c6b409d247b800dc68b0c7ab7:/telegram_markdown.go?ds=inline

diff --git a/telegram_markdown.go b/telegram_markdown.go
index 54bfbcb..16b83f2 100644
--- a/telegram_markdown.go
+++ b/telegram_markdown.go
@@ -68,6 +68,37 @@ func telegramMarkdownEntities(markdown string) (string, []TelegramEntity) {
 	return out.text.String(), out.entities
 }
 
+// telegramEscapeTags puts a backslash before each < of markdown outside inline
+// code and fenced code blocks, so that rich Markdown shows a tag name as text
+// and reads no raw HTML. A < that a backslash already makes plain stays as it
+// is. A code block that does not close runs to the end, as in Markdown.
+func telegramEscapeTags(markdown string) string {
+	var out strings.Builder
+	lines := strings.Split(markdown, "\n")
+	for index := 0; index < len(lines); index++ {
+		if index > 0 {
+			out.WriteString("\n")
+		}
+
+		line := lines[index]
+		_, fence := telegramCodeFence(line)
+		if fence == "" {
+			telegramEscapeLineTags(&out, line)
+			continue
+		}
+
+		end := telegramClosingFence(lines, index, fence)
+		if end < 0 {
+			end = len(lines) - 1
+		}
+
+		out.WriteString(strings.Join(lines[index:end+1], "\n"))
+		index = end
+	}
+
+	return out.String()
+}
+
 // telegramCodeFence returns the language of a line that opens a fenced code
 // block, and the fence. The fence is "" when line does not open a block.
 func telegramCodeFence(line string) (string, string) {
@@ -225,6 +256,39 @@ func telegramHeadingText(line string) string {
 	return rest
 }
 
+// telegramEscapeLineTags writes line to out with a backslash before each < that
+// is outside inline code and not already plain. A run of backticks that opens
+// no inline code stays as text whole, as in Markdown.
+func telegramEscapeLineTags(out *strings.Builder, line string) {
+	for index := 0; index < len(line); {
+		switch line[index] {
+		case '\\':
+			if index+1 < len(line) && strings.IndexByte(telegramMarkdownPunctuation, line[index+1]) >= 0 {
+				out.WriteString(line[index : index+2])
+				index += 2
+
+				continue
+			}
+		case '`':
+			end := index + telegramBackticks(line[index:])
+			span, found := telegramCodeSpan(line, index)
+			if found {
+				end = span.end
+			}
+
+			out.WriteString(line[index:end])
+			index = end
+
+			continue
+		case '<':
+			out.WriteByte('\\')
+		}
+
+		out.WriteByte(line[index])
+		index++
+	}
+}
+
 // telegramMarkSpan returns the inline mark that starts at index of line and
 // closes in line. It returns false when no mark starts there or the mark does
 // not close.