#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Simple Bot to reply to Telegram messages
# Copyright (C) 2015 Leandro Toledo de Souza <leandrotoeldodesouza@gmail.com>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see [http://www.gnu.org/licenses/].


import logging
import telegram
from time import sleep

try:
    from urllib.error import URLError
except ImportError:
    from urllib2 import URLError  # python 2


def main():
    # Telegram Bot Authorization Token
    bot = telegram.Bot('TOKEN')

    # get the first pending update_id, this is so we can skip over it in case
    # we get an "Unauthorized" exception.
    try:
        update_id = bot.getUpdates()[0].update_id
    except IndexError:
        update_id = None

    logging.basicConfig(
        format='%(asctime)s - %(name)s - %(levelname)s - %(message)s')

    while True:
        try:
            update_id = echo(bot, update_id)
        except telegram.TelegramError as e:
            # These are network problems with Telegram.
            if e.message in ("Bad Gateway", "Timed out"):
                sleep(1)
            elif e.message == "Unauthorized":
                # The user has removed or blocked the bot.
                update_id += 1
            else:
                raise e
        except URLError as e:
            # These are network problems on our end.
            sleep(1)


def echo(bot, update_id):

    # Request updates after the last update_id
    for update in bot.getUpdates(offset=update_id, timeout=10):
        # chat_id is required to reply to any message
        chat_id = update.message.chat_id
        update_id = update.update_id + 1
        message = update.message.text

        if message:
            # Reply to the message
            bot.sendMessage(chat_id=chat_id,
                            text=message)

    return update_id


if __name__ == '__main__':
    main()