feat: Use Telegram HTML Parsemode (#8731)

- this ensures that the markdown formatted messages from the Chatwoot dashboard will render consistently in telegram UI for the supported types like bold, italics, links etc

app/models/channel/telegram.rb

@@ -149,24 +149,32 @@ class Channel::Telegram < ApplicationRecord
                   })
   end
 
-  def convert_markdown_to_telegram(text)
-    ## supported characters : https://core.telegram.org/bots/api#markdown-style
-    ## To implement MarkdownV2, we will need to do a lot of escaping
+  def convert_markdown_to_telegram_html(text)
+    # ref: https://core.telegram.org/bots/api#html-style
 
-    # Convert bold - double asterisks to single asterisk in Telegram
-    # Chatwoot uses double asterisks for bold, while telegram used single asterisk
-    text.gsub!(/\*\*(.*?)\*\*/, '*\1*')
-    text
+    # escape html tags in text. We are subbing \n to <br> since commonmark will strip exta '\n'
+    text = CGI.escapeHTML(text.gsub("\n", '<br>'))
+
+    # convert markdown to html
+    html = CommonMarker.render_html(text).strip
+
+    # remove all html tags except b, strong, i, em, u, ins, s, strike, del, a, code, pre, blockquote
+    stripped_html = Rails::HTML5::SafeListSanitizer.new.sanitize(html, tags: %w[b strong i em u ins s strike del a code pre blockquote],
+                                                                       attributes: %w[href])
+
+    # converted escaped br tags to \n
+    stripped_html.gsub('&lt;br&gt;', "\n")
   end
 
   def message_request(chat_id, text, reply_markup = nil, reply_to_message_id = nil)
-    text_to_md = convert_markdown_to_telegram(text)
+    text_payload = convert_markdown_to_telegram_html(text)
+
     HTTParty.post("#{telegram_api_url}/sendMessage",
                   body: {
                     chat_id: chat_id,
-                    text: text_to_md,
+                    text: text_payload,
                     reply_markup: reply_markup,
-                    parse_mode: 'Markdown',
+                    parse_mode: 'HTML',
                     reply_to_message_id: reply_to_message_id
                   })
   end

spec/models/channel/telegram_spec.rb

@@ -3,6 +3,58 @@ require 'rails_helper'
 RSpec.describe Channel::Telegram do
   let(:telegram_channel) { create(:channel_telegram) }
 
+  describe '#convert_markdown_to_telegram_html' do
+    subject { telegram_channel.send(:convert_markdown_to_telegram_html, text) }
+
+    context 'when text contains multiple newline characters' do
+      let(:text) { "Line one\nLine two\n\nLine four" }
+
+      it 'preserves multiple newline characters' do
+        expect(subject).to eq("Line one\nLine two\n\nLine four")
+      end
+    end
+
+    context 'when text contains broken markdown' do
+      let(:text) { 'This is a **broken markdown with <b>HTML</b> tags.' }
+
+      it 'does not break and properly converts to Telegram HTML format and escapes html tags' do
+        expect(subject).to eq('This is a **broken markdown with &lt;b&gt;HTML&lt;/b&gt; tags.')
+      end
+    end
+
+    context 'when text contains markdown and HTML elements' do
+      let(:text) { "Hello *world*! This is <b>bold</b> and this is <i>italic</i>.\nThis is a new line." }
+
+      it 'converts markdown to Telegram HTML format and escapes other html' do
+        expect(subject).to eq("Hello <em>world</em>! This is &lt;b&gt;bold&lt;/b&gt; and this is &lt;i&gt;italic&lt;/i&gt;.\nThis is a new line.")
+      end
+    end
+
+    context 'when text contains unsupported HTML tags' do
+      let(:text) { 'This is a <span>test</span> with unsupported tags.' }
+
+      it 'removes unsupported HTML tags' do
+        expect(subject).to eq('This is a &lt;span&gt;test&lt;/span&gt; with unsupported tags.')
+      end
+    end
+
+    context 'when text contains special characters' do
+      let(:text) { 'Special characters: & < >' }
+
+      it 'escapes special characters' do
+        expect(subject).to eq('Special characters: &amp; &lt; &gt;')
+      end
+    end
+
+    context 'when text contains markdown links' do
+      let(:text) { 'Check this [link](http://example.com) out!' }
+
+      it 'converts markdown links to Telegram HTML format' do
+        expect(subject).to eq('Check this <a href="http://example.com">link</a> out!')
+      end
+    end
+  end
+
   context 'when a valid message and empty attachments' do
     it 'send message' do
       message = create(:message, message_type: :outgoing, content: 'test',
@@ -10,7 +62,7 @@ RSpec.describe Channel::Telegram do
 
       stub_request(:post, "https://api.telegram.org/bot#{telegram_channel.bot_token}/sendMessage")
         .with(
-          body: 'chat_id=123&text=test&reply_markup=&parse_mode=Markdown&reply_to_message_id='
+          body: 'chat_id=123&text=test&reply_markup=&parse_mode=HTML&reply_to_message_id='
         )
         .to_return(
           status: 200,
@@ -21,13 +73,15 @@ RSpec.describe Channel::Telegram do
       expect(telegram_channel.send_message_on_telegram(message)).to eq('telegram_123')
     end
 
-    it 'send message with markdown converted to telegram markdown' do
+    it 'send message with markdown converted to telegram HTML' do
       message = create(:message, message_type: :outgoing, content: '**test** *test* ~test~',
                                  conversation: create(:conversation, inbox: telegram_channel.inbox, additional_attributes: { 'chat_id' => '123' }))
 
       stub_request(:post, "https://api.telegram.org/bot#{telegram_channel.bot_token}/sendMessage")
         .with(
-          body: "chat_id=123&text=#{ERB::Util.url_encode('*test* *test* ~test~')}&reply_markup=&parse_mode=Markdown&reply_to_message_id="
+          body: "chat_id=123&text=#{
+            ERB::Util.url_encode('<strong>test</strong> <em>test</em> ~test~')
+          }&reply_markup=&parse_mode=HTML&reply_to_message_id="
         )
         .to_return(
           status: 200,
@@ -49,7 +103,7 @@ RSpec.describe Channel::Telegram do
         .with(
           body: 'chat_id=123&text=test' \
                 '&reply_markup=%7B%22one_time_keyboard%22%3Atrue%2C%22inline_keyboard%22%3A%5B%5B%7B%22text%22%3A%22test%22%2C%22' \
-                'callback_data%22%3A%22test%22%7D%5D%5D%7D&parse_mode=Markdown&reply_to_message_id='
+                'callback_data%22%3A%22test%22%7D%5D%5D%7D&parse_mode=HTML&reply_to_message_id='
         )
         .to_return(
           status: 200,
@@ -66,7 +120,7 @@ RSpec.describe Channel::Telegram do
 
       stub_request(:post, "https://api.telegram.org/bot#{telegram_channel.bot_token}/sendMessage")
         .with(
-          body: 'chat_id=123&text=test&reply_markup=&parse_mode=Markdown&reply_to_message_id='
+          body: 'chat_id=123&text=test&reply_markup=&parse_mode=HTML&reply_to_message_id='
         )
         .to_return(
           status: 403,