from rss import RssReader, FeedItem
from database import Database
from telegram import Notifier


class UpdateManager:
    def __init__(self, database: Database, notifier: Notifier, rss_reader: RssReader) -> None:
        self.database = database
        self.notifier = notifier
        self.rss_reader = rss_reader

    def update(self):
        feeds = self.database.find_feeds()

        for feed_id, feed_url in feeds:
            new_items = self.rss_reader.get_feed(feed_url).items
            old_items = self.database.find_feed_items(feed_id)

            diff = self.__calculate_difference(new_items, old_items)

            if not diff:
                continue

            chat_ids = self.database.find_feed_subscribers(feed_id)
            chat_ids = list(map(lambda x: x[0], chat_ids))
            self.notifier.send_updates(chat_ids, diff)
            self.database.update_feed_items(feed_id, new_items)

    def __calculate_difference(self, new_items: list[FeedItem], old_items: list[tuple]) -> list[FeedItem]:
        if not old_items:
            return new_items
        
        diff = []
        urls = list(map(lambda x: x[1], old_items))

        for item in new_items:
            if item.url not in urls:
                diff.append(item)

        return diff