import os
import tempfile
from contextlib import contextmanager
from pathlib import Path
from typing import Generator, Union
from urllib.request import urlopen

from .base import BaseStorageBackend


class HTTPBackend(BaseStorageBackend):
    """HTTP and HTTPS storage bachend."""

    def get(self, filepath: str) -> bytes:
        """Read bytes from a given ``filepath``.

        Args:
            filepath (str): Path to read data.

        Returns:
            bytes: Expected bytes object.

        Examples:
            >>> backend = HTTPBackend()
            >>> backend.get('http://path/of/file')
            b'hello world'
        """
        return urlopen(filepath).read()

    def get_text(self, filepath, encoding='utf-8') -> str:
        """Read text from a given ``filepath``.

        Args:
            filepath (str): Path to read data.
            encoding (str): The encoding format used to open the ``filepath``.
                Defaults to 'utf-8'.

        Returns:
            str: Expected text reading from ``filepath``.

        Examples:
            >>> backend = HTTPBackend()
            >>> backend.get_text('http://path/of/file')
            'hello world'
        """
        return urlopen(filepath).read().decode(encoding)

    @contextmanager
    def get_local_path(
            self, filepath: str) -> Generator[Union[str, Path], None, None]:
        """Download a file from ``filepath`` to a local temporary directory,
        and return the temporary path.

        ``get_local_path`` is decorated by :meth:`contxtlib.contextmanager`. It
        can be called with ``with`` statement, and when exists from the
        ``with`` statement, the temporary path will be released.

        Args:
            filepath (str): Download a file from ``filepath``.

        Yields:
            Iterable[str]: Only yield one temporary path.

        Examples:
            >>> backend = HTTPBackend()
            >>> # After existing from the ``with`` clause,
            >>> # the path will be removed
            >>> with backend.get_local_path('http://path/of/file') as path:
            ...     # do something here
        """
        try:
            f = tempfile.NamedTemporaryFile(delete=False)
            f.write(self.get(filepath))
            f.close()
            yield f.name
        finally:
            os.remove(f.name)
