"""Abstract interface for file storage implementations."""

from abc import ABC, abstractmethod
from collections.abc import Generator


class BaseStorage(ABC):
    """Interface for file storage."""

    @abstractmethod
    def save(self, filename: str, data: bytes):
        raise NotImplementedError

    @abstractmethod
    def load_once(self, filename: str) -> bytes:
        raise NotImplementedError

    @abstractmethod
    def load_stream(self, filename: str) -> Generator:
        raise NotImplementedError

    @abstractmethod
    def download(self, filename: str, target_filepath: str) -> None:
        raise NotImplementedError

    @abstractmethod
    def exists(self, filename: str) -> bool:
        raise NotImplementedError

    @abstractmethod
    def delete(self, filename: str):
        raise NotImplementedError

    def get_public_url(self, filename: str) -> str | None:
        """
        Return a publicly accessible URL for the given object, or None if the
        backend is not configured to serve content publicly.

        When set, file controllers will 302-redirect signed preview requests to
        this URL after verifying the signature, so that the bytes themselves are
        served by the object store / CDN instead of streamed through Dify's API.
        """
        return None

    def scan(self, path, files=True, directories=False) -> list[str]:
        """
        Scan files and directories in the given path.
        This method is implemented only in some storage backends.
        If a storage backend doesn't support scanning, it will raise NotImplementedError.
        """
        raise NotImplementedError("This storage backend doesn't support scanning")