from tqdm.auto import tqdm

from abc import ABC, abstractmethod
from typing import Dict, Any


class Explainer(ABC):
    def __init__(self, model, recommendations, data):
        self.model = model
        self.recommendations = recommendations
        self.dataset = data.dataset
        self.num_items = data.num_item
        self.num_users = data.num_user
        self.users = self.dataset.groupby(by="userId")

    def explain_recommendations(self):
        explanations = []

        with tqdm(
            total=self.recommendations.shape[0], desc="Computing explanations: "
        ) as pbar:
            for _, row in self.recommendations.iterrows():
                explanations.append(
                    self.explain_recommendation_to_user(
                        int(row.userId), int(row.itemId)
                    )
                )
                pbar.update()

        self.recommendations["explanations"] = explanations
        return self.recommendations

    def get_user_items(self, user_id):
        """
        Items Ids rated by a user.
        :param user_id: the user
        :return: list
        """
        return self.users.get_group(user_id).itemId.values

    @abstractmethod
    def explain_recommendation_to_user(
        self, user_id: int, item_id: int
    ) -> Dict[str, Any]:
        """
        Generates an explanation for a single user-item recommendation.
        This method must be implemented by any subclass.
        """
        raise NotImplementedError