import sqlite3

from exceptions import DisplayableException


class Database:
    """Implement interaction with the database."""

    def __init__(self, path: str) -> None:
        """Create a database file if not exists."""
        # TODO: think about removing check_same_thread=False
        self.conn = sqlite3.connect(path, check_same_thread=False)
        self.cur = self.conn.cursor()
        self.__init_schema()

    def add_user(self, telegram_id: int) -> int:
        """Add a user's telegram id to the database and return its database id."""
        self.cur.execute('INSERT INTO users (telegram_id) VALUES (?)', [telegram_id])
        self.conn.commit()
        return self.cur.lastrowid

    def find_user(self, telegram_id: int) -> int | None:
        """Get a user's telegram id and return its database id."""
        self.cur.execute('SELECT id FROM users WHERE telegram_id = ?', [telegram_id])
        row = self.cur.fetchone()
        if row is None:
            return None
        return row[0]

    def add_feed(self, url: str) -> int:
        """Add a feed to the database and return its id."""
        self.cur.execute('INSERT INTO feeds (url) VALUES (?)', [url])
        self.conn.commit()
        return self.cur.lastrowid

    def find_feed_by_url(self, url: str) -> int | None:
        """Find feed ID by url."""
        self.cur.execute('SELECT id FROM feeds WHERE url = ?', [url])
        row = self.cur.fetchone()
        if row is None:
            return None
        return row[0]

    def subscribe_user_by_url(self, user_id: int, url: str) -> None:
        """Subscribe user to the feed creating it if does not exist yet."""
        feed_id = self.find_feed_by_url(url)
        if feed_id is None:
            feed_id = self.add_feed(url)

        if self.is_user_subscribed(user_id, feed_id):
            raise DisplayableException('Already subscribed')

        self.subscribe_user(user_id, feed_id)

    def subscribe_user(self, user_id: int, feed_id: int) -> None:
        """Subscribe a user to the feed."""
        self.cur.execute('INSERT INTO subscriptions (user_id, feed_id) VALUES (?, ?)', [user_id, feed_id])
        self.conn.commit()

    def unsubscribe_user_by_url(self, user_id: int, url: str) -> None:
        feed_id = self.find_feed_by_url(url)
        if feed_id is None:
            raise DisplayableException('Feed does not exist')

        if not self.is_user_subscribed(user_id, feed_id):
            raise DisplayableException('Not subscribed')

        self.unsubscribe_user(user_id, feed_id)

        if self.get_feed_subscribers_count(feed_id) == 0:
            # Feed is not used anymore. Removing.
            self.delete_feed(feed_id)

    def unsubscribe_user(self, user_id: int, feed_id: int) -> None:
        """Unsubscribe a user from the feed."""
        self.cur.execute('DELETE FROM subscriptions WHERE feed_id = ? AND user_id = ?', [feed_id, user_id])
        self.conn.commit()

    def is_user_subscribed(self, user_id: int, feed_id: int) -> bool:
        """Check if user subscribed to specific feed."""
        self.cur.execute('SELECT 1 FROM subscriptions WHERE user_id = ? AND feed_id = ?', [user_id, feed_id])
        row = self.cur.fetchone()
        if row is None:
            return False
        return True

    def delete_feed(self, feed_id: int) -> None:
        """Delete a feed."""
        self.cur.execute('DELETE FROM feeds WHERE id = ?', [feed_id])
        self.conn.commit()

    def get_feed_subscribers_count(self, feed_id: int) -> int:
        """Count feed subscribers."""
        self.cur.execute('SELECT COUNT(user_id) FROM subscriptions WHERE feed_id = ?', [feed_id])
        row = self.cur.fetchone()
        if row is None:
            return 0
        return int(row[0])

    def find_feeds(self) -> list:
        """Get a list of feeds."""
        self.cur.execute('SELECT * FROM feeds')
        return self.cur.fetchall()

    def find_user_feeds(self, user_id: int) -> list:
        """Return a list of feeds the user is subscribed to."""
        self.cur.execute('SELECT * FROM feeds WHERE id IN (SELECT feed_id FROM subscriptions WHERE user_id = ?)',
                         [user_id])
        return self.cur.fetchall()

    def find_feed_items(self, feed_id: int) -> list:
        """Get last feed items."""
        self.cur.execute('SELECT * FROM feeds_last_items WHERE feed_id = ?', [feed_id])
        return self.cur.fetchall()

    def update_feed_items(self, feed_id: int, new_items: list) -> None:
        """Replace last feed items with a list items that receive."""
        for i in range(len(new_items)):
            new_items[i] = (feed_id,) + new_items[i]

        self.cur.execute('DELETE FROM feeds_last_items WHERE feed_id = ?', [feed_id])
        self.cur.executemany(
            'INSERT INTO feeds_last_items (feed_id, url, title, description, date) VALUES (?, ?, ?, ?, ?)', new_items)
        self.conn.commit()

    def __init_schema(self):
        # TODO: Move to migrations
        self.cur.execute(
            'CREATE TABLE IF NOT EXISTS users (id INTEGER, telegram_id INTEGER NOT NULL UNIQUE, PRIMARY KEY(id))'
        )
        self.cur.execute('CREATE TABLE IF NOT EXISTS feeds (id INTEGER, url TEXT NOT NULL UNIQUE, PRIMARY KEY(id))')
        self.cur.execute(
            'CREATE TABLE IF NOT EXISTS subscriptions ('
            '   user_id INTEGER,'
            '   feed_id INTEGER,'
            '   UNIQUE (user_id, feed_id),'
            '   FOREIGN KEY(user_id) REFERENCES users(id),'
            '   FOREIGN KEY(feed_id) REFERENCES feeds(id)'
            ')'
        )
        self.cur.execute(
            'CREATE TABLE IF NOT EXISTS feeds_last_items ('
            '   feed_id INTEGER,'
            '   url TEXT NOT NULL UNIQUE,'
            '   title TEXT,'
            '   description TEXT,'
            '   date NUMERIC,'
            '   FOREIGN KEY(feed_id) REFERENCES feeds(id)'
            ')'
        )