"""upath.registry -- registry for file system specific implementations

Retrieve UPath implementations via `get_upath_class`.
Register custom UPath subclasses in one of two ways:

### directly from Python

>>> from upath import UPath
>>> from upath.registry import register_implementation
>>> my_protocol = "myproto"
>>> class MyPath(UPath):
...     pass
>>> register_implementation(my_protocol, MyPath)

### via entry points

```toml
# pyproject.toml
[project.entry-points."universal_pathlib.implementations"]
myproto = "my_module.submodule:MyPath"
```

```ini
# setup.cfg
[options.entry_points]
universal_pathlib.implementations =
    myproto = my_module.submodule:MyPath
```
"""

from __future__ import annotations

import os
import re
import sys
import warnings
from collections import ChainMap
from functools import lru_cache
from importlib import import_module
from importlib.metadata import entry_points
from typing import TYPE_CHECKING
from typing import Iterator
from typing import MutableMapping

from fsspec.core import get_filesystem_class
from fsspec.registry import known_implementations as _fsspec_known_implementations

import upath

__all__ = [
    "get_upath_class",
    "available_implementations",
    "register_implementation",
]


_ENTRY_POINT_GROUP = "universal_pathlib.implementations"


class _Registry(MutableMapping[str, "type[upath.UPath]"]):
    """internal registry for UPath subclasses"""

    known_implementations: dict[str, str] = {
        "abfs": "upath.implementations.cloud.AzurePath",
        "abfss": "upath.implementations.cloud.AzurePath",
        "adl": "upath.implementations.cloud.AzurePath",
        "az": "upath.implementations.cloud.AzurePath",
        "data": "upath.implementations.data.DataPath",
        "file": "upath.implementations.local.FilePath",
        "local": "upath.implementations.local.FilePath",
        "gcs": "upath.implementations.cloud.GCSPath",
        "gs": "upath.implementations.cloud.GCSPath",
        "hdfs": "upath.implementations.hdfs.HDFSPath",
        "http": "upath.implementations.http.HTTPPath",
        "https": "upath.implementations.http.HTTPPath",
        "memory": "upath.implementations.memory.MemoryPath",
        "s3": "upath.implementations.cloud.S3Path",
        "s3a": "upath.implementations.cloud.S3Path",
        "sftp": "upath.implementations.sftp.SFTPPath",
        "ssh": "upath.implementations.sftp.SFTPPath",
        "webdav": "upath.implementations.webdav.WebdavPath",
        "webdav+http": "upath.implementations.webdav.WebdavPath",
        "webdav+https": "upath.implementations.webdav.WebdavPath",
        "github": "upath.implementations.github.GitHubPath",
        "smb": "upath.implementations.smb.SMBPath",
    }

    if TYPE_CHECKING:
        _m: MutableMapping[str, str | type[upath.UPath]]

    def __init__(self) -> None:
        if sys.version_info >= (3, 10):
            eps = entry_points(group=_ENTRY_POINT_GROUP)
        else:
            eps = entry_points().get(_ENTRY_POINT_GROUP, [])
        self._entries = {ep.name: ep for ep in eps}
        self._m = ChainMap({}, self.known_implementations)  # type: ignore

    def __contains__(self, item: object) -> bool:
        return item in set().union(self._m, self._entries)

    def __getitem__(self, item: str) -> type[upath.UPath]:
        fqn: str | type[upath.UPath] | None = self._m.get(item)
        if fqn is None:
            if item in self._entries:
                fqn = self._m[item] = self._entries[item].load()
        if fqn is None:
            raise KeyError(f"{item} not in registry")
        if isinstance(fqn, str):
            module_name, name = fqn.rsplit(".", 1)
            mod = import_module(module_name)
            cls = getattr(mod, name)  # type: ignore
        else:
            cls = fqn
        return cls

    def __setitem__(self, item: str, value: type[upath.UPath] | str) -> None:
        if not (
            (isinstance(value, type) and issubclass(value, upath.UPath))
            or isinstance(value, str)
        ):
            raise ValueError(
                f"expected UPath subclass or FQN-string, got: {type(value).__name__!r}"
            )
        if not item or item in self._m:
            get_upath_class.cache_clear()
        self._m[item] = value

    def __delitem__(self, __v: str) -> None:
        raise NotImplementedError("removal is unsupported")

    def __len__(self) -> int:
        return len(set().union(self._m, self._entries))

    def __iter__(self) -> Iterator[str]:
        return iter(set().union(self._m, self._entries))


_registry = _Registry()


def available_implementations(*, fallback: bool = False) -> list[str]:
    """return a list of protocols for available implementations

    Parameters
    ----------
    fallback:
        If True, also return protocols for fsspec filesystems without
        an implementation in universal_pathlib.
    """
    impl = list(_registry)
    if not fallback:
        return impl
    else:
        return list({*impl, *list(_fsspec_known_implementations)})


def register_implementation(
    protocol: str,
    cls: type[upath.UPath] | str,
    *,
    clobber: bool = False,
) -> None:
    """register a UPath implementation with a protocol

    Parameters
    ----------
    protocol:
        Protocol name to associate with the class
    cls:
        The UPath subclass for the protocol or a str representing the
        full path to an implementation class like package.module.class.
    clobber:
        Whether to overwrite a protocol with the same name; if False,
        will raise instead.
    """
    if not re.match(r"^[a-z][a-z0-9+_.]+$", protocol):
        raise ValueError(f"{protocol!r} is not a valid URI scheme")
    if not clobber and protocol in _registry:
        raise ValueError(f"{protocol!r} is already in registry and clobber is False!")
    _registry[protocol] = cls


@lru_cache
def get_upath_class(
    protocol: str,
    *,
    fallback: bool = True,
) -> type[upath.UPath] | None:
    """Return the upath cls for the given protocol.

    Returns `None` if no matching protocol can be found.

    Parameters
    ----------
    protocol:
        The protocol string
    fallback:
        If fallback is False, don't return UPath instances for fsspec
        filesystems that don't have an implementation registered.
    """
    try:
        return _registry[protocol]
    except KeyError:
        if not protocol:
            if os.name == "nt":
                from upath.implementations.local import WindowsUPath

                return WindowsUPath
            else:
                from upath.implementations.local import PosixUPath

                return PosixUPath
        if not fallback:
            return None
        try:
            _ = get_filesystem_class(protocol)
        except ValueError:
            return None  # this is an unknown protocol
        else:
            warnings.warn(
                f"UPath {protocol!r} filesystem not explicitly implemented."
                " Falling back to default implementation."
                " This filesystem may not be tested.",
                UserWarning,
                stacklevel=2,
            )
            return upath.UPath