from abc import ABC, abstractmethod
import time
from typing import Optional
import requests
import difflib

ACCOMMODATION_URL = "https://warwick.ac.uk/services/accommodation/students/current/"
def get_accommodation_page() -> Optional[str]:
    r = requests.get(ACCOMMODATION_URL)
    if r is None:
        return None
    else:
        return r.text

def get_difference(page_before: str, page_after: str) -> Optional[list[str]]:
    if page_before == page_after:
        return None
    
    return [*difflib.context_diff(page_before.splitlines(), page_after.splitlines())]

THIRTY_MINUTES = 30 * 60
TIMEOUT = THIRTY_MINUTES
class Sniper(ABC):
    previous_page: str

    def __init__(self):
        self.previous_page = get_accommodation_page()

    def update(self) -> None:
        current_page = get_accommodation_page()
        if get_difference(self.previous_page, current_page):
            self.on_change()
        else:
            self.on_same()
        self.previous_page = current_page

    @abstractmethod
    def on_change(self) -> None:
        pass
    
    def on_same(self) -> None:
        pass

    def loop(self):
        while True:
            time.sleep(TIMEOUT)
            self.update()