from telegram import Update, Bot
from telegram.ext import Updater, CommandHandler, CallbackContext
from bs4 import BeautifulSoup
import requests
import time
import difflib
import threading

# Parameters
TOKEN = 'your-bot-token'  # Telegram bot token
CHAT_ID = 'your-chat-id'  # Telegram chat id
MAX_TRACKED_SITES = 5  # Maximum number of sites a user can track
MIN_TRACKING_INTERVAL = 30  # Minimum tracking interval (minutes)

active_threads = {}  # Dictionary to store tracked websites and threads

def start(update: Update, context: CallbackContext) -> None:
    context.bot.send_message(chat_id=update.effective_chat.id, text="Hello! You can track websites using the /track command. Example: /track www.google.com 60")

def track_website_changes(update: Update, context: CallbackContext, url, interval) -> None:
    old_content = fetch_website_content(url)

    while True:
        time.sleep(interval * 60)  # convert minutes to seconds
        new_content = fetch_website_content(url)

        if url not in active_threads[update.effective_chat.id]:  # If cancel command is received, stop this thread
            return

        if new_content != old_content:
            # Check if the content matches with the previous fetch
            changes = difflib.ndiff(old_content.splitlines(keepends=True),
                                     new_content.splitlines(keepends=True))

            changes_report = list(changes)
            message = '\n'.join(changes_report)
            # Messages longer than 4096 characters are not accepted by Telegram.
            if len(message) > 4096:
                message = message[:4095]
            context.bot.send_message(chat_id=update.effective_chat.id, text=message)
            old_content = new_content

def fetch_website_content(url):
    response = requests.get(url)
    soup = BeautifulSoup(response.text, 'html.parser')
    return soup.prettify()

def track(update: Update, context: CallbackContext):
    url = context.args[0]
    interval = int(context.args[1])

    if interval < MIN_TRACKING_INTERVAL:
        context.bot.send_message(chat_id=update.effective_chat.id, text=f"The tracking interval must be at least {MIN_TRACKING_INTERVAL} minutes.")
        return
    
    if update.effective_chat.id not in active_threads:
        active_threads[update.effective_chat.id] = {}
    
    if url in active_threads[update.effective_chat.id]:  # If the website is already being tracked, don't start a new thread
        context.bot.send_message(chat_id=update.effective_chat.id, text="This website is already being tracked.")
        return

    if len(active_threads[update.effective_chat.id]) >= MAX_TRACKED_SITES:
        context.bot.send_message(chat_id=update.effective_chat.id, text=f"You can track up to {MAX_TRACKED_SITES} websites.")
        return

    thread = threading.Thread(target=track_website_changes, args=(update, context, url, interval))
    active_threads[update.effective_chat.id][url] = thread
    thread.start()

def list_tracked_websites(update: Update, context: CallbackContext):
    if update.effective_chat.id not in active_threads or not active_threads[update.effective_chat.id]:
        context.bot.send_message(chat_id=update.effective_chat.id, text="No websites are being tracked.")
        return
    
    message = "Tracked websites:\n" + "\n".join(active_threads[update.effective_chat.id].keys())
    context.bot.send_message(chat_id=update.effective_chat.id, text=message)

def cancel_tracking(update: Update, context: CallbackContext):
    url = context.args[0]
    
    if update.effective_chat.id not in active_threads or url not in active_threads[update.effective_chat.id]:
        context.bot.send_message(chat_id=update.effective_chat.id, text="This website is not being tracked.")
        return

    del active_threads[update.effective_chat.id][url]  # Remove the tracked website and thread from the dictionary
    context.bot.send_message(chat_id=update.effective_chat.id, text="Tracking for the website has been canceled.")

def help_message(update: Update, context: CallbackContext):
    help_text = """
/track www.example.com 60: Tracks the website at www.example.com with an interval of 60 minutes. Sends a notification when a change is detected. The tracking interval must be at least 30 minutes.
/list: Returns a list of actively tracked websites.
/cancel www.example.com: Stops tracking the website at www.example.com.
"""
    context.bot.send_message(chat_id=update.effective_chat.id, text=help_text)

updater = Updater(token=TOKEN, use_context=True)
dispatcher = updater.dispatcher

start_handler = CommandHandler('start', start)
track_handler = CommandHandler('track', track)
list_handler = CommandHandler('list', list_tracked_websites)
cancel_handler = CommandHandler('cancel', cancel_tracking)
help_handler = CommandHandler('help', help_message)

dispatcher.add_handler(start_handler)
dispatcher.add_handler(track_handler)
dispatcher.add_handler(list_handler)
dispatcher.add_handler(cancel_handler)
dispatcher.add_handler(help_handler)

updater.start_polling()