from __future__ import annotations

import os
import warnings
from collections.abc import Iterable
from importlib.metadata import entry_points
from typing import TYPE_CHECKING, Final

if TYPE_CHECKING:
    from . import PydanticPluginProtocol


PYDANTIC_ENTRY_POINT_GROUP: Final[str] = 'pydantic'

# cache of plugins
_plugins: dict[str, PydanticPluginProtocol] | None = None
# return no plugins while loading plugins to avoid recursion and errors while importing plugins
# this means that if plugins use pydantic
_loading_plugins: bool = False


def get_plugins() -> Iterable[PydanticPluginProtocol]:
    """Load plugins for Pydantic.

    Plugins are discovered using the `pydantic` entry point group, as documented in
    https://packaging.python.org/en/latest/guides/creating-and-discovering-plugins/#using-package-metadata.
    """
    disabled_plugins = os.getenv('PYDANTIC_DISABLE_PLUGINS')
    global _plugins, _loading_plugins
    if _loading_plugins:
        # this happens when plugins themselves use pydantic, we return no plugins
        return ()
    elif disabled_plugins in ('__all__', '1', 'true'):
        return ()
    elif _plugins is None:
        _plugins = {}
        # set _loading_plugins so any plugins that use pydantic don't themselves use plugins
        _loading_plugins = True
        try:
            for entry_point in entry_points(group=PYDANTIC_ENTRY_POINT_GROUP):
                if entry_point.value in _plugins:
                    continue
                if disabled_plugins is not None and entry_point.name in disabled_plugins.split(','):
                    continue
                try:
                    _plugins[entry_point.value] = entry_point.load()
                except (ImportError, AttributeError) as e:
                    warnings.warn(
                        f'{e.__class__.__name__} while loading the `{entry_point.name}` Pydantic plugin, '
                        f'this plugin will not be installed.\n\n{e!r}',
                        stacklevel=2,
                    )
        finally:
            _loading_plugins = False

    return _plugins.values()