#
# Copyright (C) 2020 Radim Rehurek <me@radimrehurek.com>
#
# This code is distributed under the terms and conditions
# from the MIT License (MIT).
#
"""Maintains a registry of transport mechanisms.

The main entrypoint is :func:`get_transport`.  See also :file:`EXTENDING.md`.

"""

from __future__ import annotations

import importlib
import logging
from typing import TYPE_CHECKING

import smart_open.local_file

if TYPE_CHECKING:
    from types import ModuleType

logger = logging.getLogger(__name__)

NO_SCHEME = ""

_REGISTRY: dict[str, ModuleType] = {NO_SCHEME: smart_open.local_file}
_ERRORS: dict[str, str] = {}
_MISSING_DEPS_ERROR = """You are trying to use the %(module)s functionality of smart_open
but you do not have the correct %(module)s dependencies installed. Try:

    pip install smart_open[%(module)s]

"""


def register_transport(submodule: str | ModuleType) -> None:
    """Register a submodule as a transport mechanism for ``smart_open``.

    This module **must** have:

        - `SCHEME` attribute (or `SCHEMES`, if the submodule supports multiple schemes)
        - `open` function
        - `open_uri` function
        - `parse_uri' function

    Once registered, you can get the submodule by calling :func:`get_transport`.

    """
    if isinstance(submodule, str):
        module_name = submodule
        try:
            submodule = importlib.import_module(submodule)
        except ImportError:
            return
    else:
        module_name = submodule.__name__
    # Save only the last module name piece
    module_name = module_name.rsplit(".")[-1]

    if hasattr(submodule, "SCHEME"):
        schemes = [submodule.SCHEME]
    elif hasattr(submodule, "SCHEMES"):
        schemes = submodule.SCHEMES
    else:
        msg = f"{submodule!r} does not have a .SCHEME or .SCHEMES attribute"
        raise ValueError(msg)

    for f in ("open", "open_uri", "parse_uri"):
        assert hasattr(submodule, f), f"{submodule!r} is missing {f!r}"  # noqa: S101  # internal precondition; misuse should crash loudly

    for scheme in schemes:
        assert scheme not in _REGISTRY  # noqa: S101  # internal precondition; misuse should crash loudly
        if getattr(submodule, "MISSING_DEPS", False):
            _ERRORS[scheme] = module_name
        else:
            _REGISTRY[scheme] = submodule


def get_transport(scheme: str) -> ModuleType:
    """Get the submodule that handles transport for the specified scheme.

    This submodule must have been previously registered via :func:`register_transport`.

    """
    expected = SUPPORTED_SCHEMES
    readme_url = "https://github.com/piskvorky/smart_open/blob/master/README.md"
    message = (
        "Unable to handle scheme {scheme!r}, expected one of {expected!r}. "
        "Extra dependencies required by {scheme!r} may be missing. "
        "See <{readme_url}> for details.".format(**locals())
    )
    if scheme in _ERRORS:
        raise ImportError(_MISSING_DEPS_ERROR % {"module": _ERRORS[scheme]})
    if scheme in _REGISTRY:
        return _REGISTRY[scheme]
    raise NotImplementedError(message)


register_transport(smart_open.local_file)
register_transport("smart_open.azure")
register_transport("smart_open.ftp")
register_transport("smart_open.gcs")
register_transport("smart_open.hdfs")
register_transport("smart_open.http")
register_transport("smart_open.s3")
register_transport("smart_open.ssh")
register_transport("smart_open.webhdfs")

SUPPORTED_SCHEMES = tuple(sorted(_REGISTRY.keys()))
"""The transport schemes that the local installation of ``smart_open`` supports."""