Monitor channel and join to private channel via link

telethon-channel-joiner.py

import re
from telethon import events, types
from telethon.sync import TelegramClient
from telethon.tl.functions.channels import JoinChannelRequest
from telethon.tl.functions.messages import ImportChatInviteRequest
from telethon.errors.rpcerrorlist import SessionPasswordNeededError


# Replace the values below with your own API credentials
api_id = '12345678'
api_hash = '12345678123456781234567812345678'
phone_number = '+380123456789'
PASS = 'your-account-password-if-enabled'

# Replace with the username or ID of the channel you want to monitor
channel_username = -100

client = TelegramClient('session_name', api_id, api_hash)

client.connect()

if not client.is_user_authorized():
    client.send_code_request(phone_number)
    try:
        client.sign_in(phone_number, input(
            'Enter the code sent to your phone: '))
    except SessionPasswordNeededError as err:
        client.sign_in(password=PASS)


# might need it on first run
# client.get_dialogs()

channel_entity = client.get_entity(channel_username)


@client.on(events.NewMessage(chats=channel_entity))
async def monitor_channel(event):
    print("monitoring...")
    message = event.message
    print(message.message)
    print(message.entities)

    # will not work if the link is in hyperlink
    if '+' in message.message:
        invite_link_regex = r'/\+[^\s]+'
        invite_link = re.findall(
            invite_link_regex, message.message)[0]

        hash_index = invite_link.rfind('/+') + 2
        chat_hash = invite_link[hash_index:]

        print("hash found: ", chat_hash)

        result = await client(ImportChatInviteRequest(chat_hash))
        if isinstance(result, types.ChatInviteImported):
            print('Successfully joined the chat or channel.')
        else:
            print('Failed to join the chat or channel.')
            
    # will work if the link is in hyperlink
    if message.entities:
       # Iterate over the entities to find the hyperlink entity
       for entity in message.entities:
           if isinstance(entity, types.MessageEntityTextUrl):
               # Extract the URL from the hyperlink entity
               invite_link = entity.url
               print('Invite link found:', invite_link)

               # Extract the hash from the invite link
               hash_index = invite_link.rfind('/+') + 2
               chat_hash = invite_link[hash_index:]

               result = await client(ImportChatInviteRequest(chat_hash))

               # sometimes may result in
               # AttributeError: module 'telethon.types' has no attribute 'ChatInviteImported'
               # but it will join
               if isinstance(result, types.ChatInviteImported):
                   print('Successfully joined the chat or channel.')
               else:
                   print('Failed to join the chat or channel.')

               # Exit the loop once the first hyperlink entity is found
               break


client.start()
client.run_until_disconnected()