From 84419940e329b59e58fc32ce75f67e337a23de41 Mon Sep 17 00:00:00 2001
From: surdeus <surdeus@gmail.com>
Date: Thu, 5 Oct 2023 17:51:24 +0300
Subject: [PATCH] Implemented the escaping function for the Markdown2.

---
 cmd/test/main.go | 18 +++++++++++++++++-
 tg/message.go    | 11 +++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/cmd/test/main.go b/cmd/test/main.go
index 06a8fa0..8cbb01a 100644
--- a/cmd/test/main.go
+++ b/cmd/test/main.go
@@ -38,7 +38,10 @@ func (w *MutateMessageWidget) Serve(c *tg.Context) {
 	}
 	for u := range c.Input() {
 		text := u.Message.Text
-		c.Sendf("%s", w.Mutate(text))
+		_, err := c.Sendf2("%s", w.Mutate(text))
+		if err != nil {
+			c.Sendf("debug: %q", err)
+		}
 	}
 }
 
@@ -132,6 +135,7 @@ WithInitFunc(func(c *tg.Context) {
 					tg.NewKeyboard().Row(
 						tg.NewButton("Upper case").Go("upper-case"),
 						tg.NewButton("Lower case").Go("lower-case"),
+						tg.NewButton("Escape chars").Go("escape"),
 					).Row(
 						backButton,
 					).Reply(),
@@ -162,6 +166,18 @@ WithInitFunc(func(c *tg.Context) {
 				}
 			}),
 		),
+		tg.NewNode(
+			"escape", tg.RenderFunc(func(c *tg.Context) tg.UI {
+				return tg.UI{
+					tg.NewMessage(
+						"Type a string and the bot will escape characters in it",
+					).Reply(
+						backKeyboard.Reply(),
+					),
+					NewMutateMessageWidget(tg.Escape2),
+				}
+			}),
+		),
 	),
 
 	tg.NewNode(
diff --git a/tg/message.go b/tg/message.go
index 4197ecd..5bda431 100644
--- a/tg/message.go
+++ b/tg/message.go
@@ -3,6 +3,7 @@ package tg
 import (
 	tgbotapi "github.com/go-telegram-bot-api/telegram-bot-api/v5"
 	//"strings"
+	re "regexp"
 )
 type Message = tgbotapi.Message
 
@@ -13,6 +14,16 @@ type MessageCompo struct {
 	Text string
 }
 
+var (
+	escapeRe = re.MustCompile(`([_*\[\]()~`+"`"+`>#+-=|{}.!])`)
+)
+
+// Escape special characters in Markdown 2 and return the
+// resulting string.
+func Escape2(str string) string {
+	return string(escapeRe.ReplaceAll([]byte(str), []byte("\\$1")))
+}
+
 func (compo *MessageCompo) SetMessage(msg *Message) {
 	compo.Message = msg
 }