import sqlite3

class CartDatabase:
    def __init__(self, db_file):
        """Initialize the CartDatabase with a connection to the SQLite database."""
        self.conn = sqlite3.connect(db_file)

    def add_to_cart(self, user_id, product_id, quantity):
        """Add a product to the user's cart."""
        sql = "INSERT INTO cart (user_id, product_id, quantity) VALUES (?, ?, ?)"
        try:
            c = self.conn.cursor()
            c.execute(sql, (user_id, product_id, quantity))
            self.conn.commit()
            return c.lastrowid
        except sqlite3.Error as e:
            print(e)

    def get_cart_for_user(self, user_id):
        """Retrieve the cart items for a specific user."""
        sql = "SELECT * FROM cart WHERE user_id = ?"
        try:
            c = self.conn.cursor()
            c.execute(sql, (user_id,))
            return c.fetchall()
        except sqlite3.Error as e:
            print(e)
            return []

    def update_cart_item(self, user_id, product_id, quantity):
        """Update the quantity of a specific cart item based on user_id and product_id."""
        sql = "UPDATE cart SET quantity = ? WHERE user_id = ? AND product_id = ?"
        try:
            c = self.conn.cursor()
            c.execute(sql, (quantity, user_id, product_id))
            self.conn.commit()
        except sqlite3.Error as e:
            print(e)

    def remove_from_cart(self, cart_id):
        """Remove a specific item from the cart."""
        sql = "DELETE FROM cart WHERE id = ?"
        try:
            c = self.conn.cursor()
            c.execute(sql, (cart_id,))
            self.conn.commit()
        except sqlite3.Error as e:
            print(e)

    def clear_cart(self, user_id):
        """Clear all items from a user's cart."""
        sql = "DELETE FROM cart WHERE user_id = ?"
        try:
            c = self.conn.cursor()
            c.execute(sql, (user_id,))
            self.conn.commit()
        except sqlite3.Error as e:
            print(e)

    def get_cart_total(self, user_id):
        """Calculate the total cost of all items in a user's cart."""
        sql = "SELECT SUM(products.price * cart.quantity) FROM cart JOIN products ON cart.product_id = products.id WHERE cart.user_id = ?"
        try:
            c = self.conn.cursor()
            c.execute(sql, (user_id,))
            return c.fetchone()[0]
        except sqlite3.Error as e:
            print(e)
            return 0
        
def main():
    database = "db/shop.db"

    cart_db = CartDatabase(database)

    ex_user_id = 1

    # delete all cart items
    cart_db.clear_cart(ex_user_id)

    # user id, product id, quantity
    cart_db.add_to_cart(ex_user_id, 1, 2)
    cart_db.add_to_cart(ex_user_id, 3, 5)

    print(f"Cart items for user {ex_user_id}:", cart_db.get_cart_for_user(ex_user_id))
    print(f"Total cost for user {ex_user_id}:", cart_db.get_cart_total(ex_user_id))

    # user id, product id, quantity
    cart_db.update_cart_item(ex_user_id, 3, 3)
    print(f"Cart items for user {ex_user_id}:", cart_db.get_cart_for_user(ex_user_id))
    print(f"Total cost for user {ex_user_id}:", cart_db.get_cart_total(ex_user_id))

if __name__ == "__main__":
    main()