From e3dda0e812606e8d051567c401c139dc392706e1 Mon Sep 17 00:00:00 2001
From: Tatsuyuki Ishi <ishitatsuyuki@gmail.com>
Date: Sat, 7 Jan 2017 07:32:17 +0900
Subject: [PATCH] Telegram: add markdown (#103)

* Add support for markdown (telegram)

Close #98

* Telegram: add more Markdown Render blacklist
---
 bridge/telegram/telegram.go | 66 +++++++++++++++++++++++++++++++++++--
 1 file changed, 63 insertions(+), 3 deletions(-)

diff --git a/bridge/telegram/telegram.go b/bridge/telegram/telegram.go
index db3ab323..b179dd6d 100644
--- a/bridge/telegram/telegram.go
+++ b/bridge/telegram/telegram.go
@@ -1,10 +1,14 @@
 package btelegram
 
 import (
+	"bytes"
+	"html"
+	"strconv"
+
 	"github.com/42wim/matterbridge/bridge/config"
 	log "github.com/Sirupsen/logrus"
 	"github.com/go-telegram-bot-api/telegram-bot-api"
-	"strconv"
+	"github.com/russross/blackfriday"
 )
 
 type Btelegram struct {
@@ -51,13 +55,70 @@ func (b *Btelegram) JoinChannel(channel string) error {
 	return nil
 }
 
+type customHtml struct {
+	blackfriday.Renderer
+}
+
+func (options *customHtml) Paragraph(out *bytes.Buffer, text func() bool) {
+	marker := out.Len()
+
+	if !text() {
+		out.Truncate(marker)
+		return
+	}
+	out.WriteString("\n")
+}
+
+func (options *customHtml) BlockCode(out *bytes.Buffer, text []byte, lang string) {
+	out.WriteString("<pre>")
+
+	out.WriteString(html.EscapeString(string(text)))
+	out.WriteString("</pre>\n")
+}
+
+func (options *customHtml) Header(out *bytes.Buffer, text func() bool, level int, id string) {
+	options.Paragraph(out, text)
+}
+
+func (options *customHtml) HRule(out *bytes.Buffer) {
+	out.WriteByte('\n')
+}
+
+func (options *customHtml) BlockQuote(out *bytes.Buffer, text []byte) {
+	out.WriteString("> ")
+	out.Write(text)
+	out.WriteByte('\n')
+}
+
+func (options *customHtml) List(out *bytes.Buffer, text func() bool, flags int) {
+	options.Paragraph(out, text)
+}
+
+func (options *customHtml) ListItem(out *bytes.Buffer, text []byte, flags int) {
+	out.WriteString("- ")
+	out.Write(text)
+	out.WriteByte('\n')
+}
+
 func (b *Btelegram) Send(msg config.Message) error {
 	flog.Debugf("Receiving %#v", msg)
 	chatid, err := strconv.ParseInt(msg.Channel, 10, 64)
 	if err != nil {
 		return err
 	}
-	m := tgbotapi.NewMessage(chatid, msg.Username + msg.Text)
+
+	parsed := blackfriday.Markdown([]byte(msg.Text),
+		&customHtml{blackfriday.HtmlRenderer(blackfriday.HTML_USE_XHTML|blackfriday.HTML_SKIP_IMAGES, "", "")},
+		blackfriday.EXTENSION_NO_INTRA_EMPHASIS|
+			blackfriday.EXTENSION_FENCED_CODE|
+			blackfriday.EXTENSION_AUTOLINK|
+			blackfriday.EXTENSION_SPACE_HEADERS|
+			blackfriday.EXTENSION_HEADER_IDS|
+			blackfriday.EXTENSION_BACKSLASH_LINE_BREAK|
+			blackfriday.EXTENSION_DEFINITION_LISTS)
+
+	m := tgbotapi.NewMessage(chatid, msg.Username+string(parsed))
+	m.ParseMode = "HTML"
 	_, err = b.c.Send(m)
 	return err
 }
@@ -69,6 +130,5 @@ func (b *Btelegram) handleRecv(updates <-chan tgbotapi.Update) {
 		}
 		flog.Debugf("Sending message from %s on %s to gateway", update.Message.From.UserName, b.Account)
 		b.Remote <- config.Message{Username: update.Message.From.UserName, Text: update.Message.Text, Channel: strconv.FormatInt(update.Message.Chat.ID, 10), Account: b.Account}
-
 	}
 }