from abc import ABC, abstractmethod
import polars as pl


class DataSource(ABC):
    """Base class for all data sources."""

    @property
    @abstractmethod
    def name(self) -> str:
        """Unique identifier for this data source."""
        pass

    @abstractmethod
    def load(self) -> pl.LazyFrame:
        """Load raw data as LazyFrame."""
        pass

    @abstractmethod
    def process(self, postcodes: pl.LazyFrame) -> pl.LazyFrame:
        """Process and join with postcode coordinates."""
        pass