from __future__ import annotations

from abc import ABC, abstractmethod
from enum import Enum
from typing import Generic, TypeVar

E = TypeVar("E", bound=Enum)


class ClassificationError(Exception):
    """Raised when classifying a column's descriptions fails wholesale.

    A whole-batch failure (the AI backend is unreachable, or returns a reply
    that cannot be parsed) raises this. A single description that merely
    cannot be resolved is not an error -- it maps to the enum's UNKNOWN member.
    """


class ColumnClassifier(ABC, Generic[E]):
    """Port: resolves free-text descriptions into a category enum ``E``.

    One classifier handles one landlord-CSV column. Implementations decide
    *how* the mapping is performed (an LLM, a lookup table, a rules engine);
    ``LandlordDescriptionOverridesOrchestrator`` depends only on this interface.
    """

    @abstractmethod
    def classify(self, descriptions: set[str]) -> dict[str, E]:
        """Classify each description into a category enum member.

        Every input description appears as a key in the result. A description
        that cannot be resolved maps to the enum's UNKNOWN member.

        Raises:
            ClassificationError: If the classification call fails wholesale
                (e.g. the backend is unreachable or returns an unparseable
                response).
        """
        ...