A Simple Welcome Telegram Bot that gives simple (configurable) welcome messages

a_simple_welcome_bot.py

'''A Simple Welcome Telegram Bot that gives simple (configurable) welcome messages'''
import os
import json

from telegram.ext import Updater, CommandHandler, MessageHandler, BaseFilter
# link to mwt file: https://gist.github.com/jh0ker/56f5b4fb7d015b1b9e4c74d4a91d4568
from mwt import MWT

def read_json(path_json):
    '''Lee el json con los mensajes'''
    with open(path_json, 'r') as f:
        new_dict = json.load(f)
    return new_dict

def save_json(path_json, dict_object):
    '''Salva a disco los mensajes'''
    with open(path_json, 'w') as f:
        json.dump(dict_object, f)

# sacado de 'code-snippers':
# https://github.com/python-telegram-bot/python-telegram-bot/wiki/Code-snippets#get-the-add-group-message
class NewMember(BaseFilter):
      def filter(self, message):
          if not message.new_chat_members:
              return False
          return True

def get_group_message(chat_id):
    '''Si existe devuelve el mensaje, sino el defaut mensaje'''
    chat_id = str(chat_id)
    if chat_id not in msjs.keys():
        msj = defaut_msj
    else:
        msj = msjs[chat_id]
    return msj


def add_group(bot, update):
    chat_id = update.message.chat_id
    msj = get_group_message(chat_id)

    for members in update.message.new_chat_members:
        bot.send_message(update.message.chat_id,
                         text=msj)

# https://github.com/python-telegram-bot/python-telegram-bot/wiki/Code-snippets#cached-telegram-group-administrator-check
@MWT(timeout=60*60)
def get_admin_ids(bot, chat_id):
    """Returns a list of admin IDs for a given chat. Results are cached for 1 hour."""
    return [admin.user.id for admin in bot.get_chat_administrators(chat_id)]

def change_message(bot, update):
    '''Guarda un nuevo mensaje, si tiene los permisos para hacerlo'''
    chat_id = str(update.message.chat_id)
    all_admin = update.message.chat.all_members_are_administrators
    is_a_admin = update.message.from_user.id in get_admin_ids(bot, chat_id)

    if all_admin or is_a_admin:
        update_msj = update.message.text.split(maxsplit=1)[1]
        msjs[chat_id] = update_msj
        save_json(path_json, msjs)
        bot.send_message(chat_id=chat_id, text="Welcome message update")
    else:
        bot.send_message(chat_id=chat_id, text="You need be a admin to change the message")

def print_message(bot, update):
    '''Muestra el mensaje acutal del grupo'''
    chat_id = update.message.chat_id
    msj = get_group_message(chat_id)
    bot.send_message(chat_id=chat_id, text=msj)


def help_message(bot, update):
    '''Muestra una help basica'''
    help_msj = '''Show welcome messages when a user join a group.
Only the group admin could change it.

Usage:
/change_message new_mesage - Change the welcome group message
/print_message - Display the current welcome group message
/help - Display this help message

Example:
/change_message My awesome new welcome message!!'''
    bot.send_message(chat_id=update.message.chat_id, text=help_msj)

with open('secret') as f:
    token = f.readline().strip()

path_json = 'msjs.json'

if os.path.isfile(path_json):
    msjs = read_json(path_json)
else:
    msjs = dict()

defaut_msj = 'Welcome!'

updater = Updater(token=token)
dispatcher = updater.dispatcher

add_group_handle = MessageHandler(callback=add_group, filters=NewMember())
dispatcher.add_handler(add_group_handle)

change_message_handler = CommandHandler('change_message', change_message)
dispatcher.add_handler(change_message_handler)

print_message_handler = CommandHandler('print_message', print_message)
dispatcher.add_handler(print_message_handler)

help_handler = CommandHandler('help', help_message)
dispatcher.add_handler(help_handler)

updater.start_polling()