"""Abstract retriever interface."""

from __future__ import annotations
from abc import ABC, abstractmethod
from dataclasses import dataclass
from typing import List

@dataclass
class Context:
    """A retrieved passage or document."""

    id: str
    text: str
    score: float


class Retriever(ABC):
    """Abstract base class for all retrievers."""

    @abstractmethod
    def retrieve(self, query: str, *, top_k: int = 5) -> List[Context]:
        """Return the top‑k contexts for a query."""
        raise NotImplementedError