"""

Part of the tagit module.
A copy of the license is provided with the project.
Author: Matthias Baumgartner, 2022
"""
# standard imports
from collections import abc
from functools import partial
from inspect import isclass
import typing

# exports
__all__: typing.Sequence[str] = (
    'BuilderBase',
    'InvalidFactoryName',
    )


## code ##

class InvalidFactoryName(KeyError): pass

class BuilderBase(abc.Mapping, abc.Hashable):
    _factories = dict()

    def __getitem__(self, key):
        return self.get(key)

    def __contains__(self, key):
        return key in self._factories

    def __iter__(self):
        return iter(self._factories.keys())

    def __hash__(self):
        return hash(frozenset(self._factories.items()))

    def __len__(self):
        return len(self._factories)

    def __eq__(self, other):
        return type(self) == type(other) and self._factories == other._factories


    def get(self, key):
        if key not in self._factories:
            raise InvalidFactoryName(key)
        return self._factories[key]

    @classmethod
    def keys(self):
        return self._factories.keys()

    @classmethod
    def items(self):
        return self._factories.items()

    @classmethod
    def describe(cls, key):
        if key not in cls._factories:
            raise InvalidFactoryName(key)
        desc = cls._factories[key].__doc__
        return desc if desc is not None else ''

    def prepare(self, key, *args, **kwargs):
        # If building is to be customized, overwrite this function.
        return partial(self[key], *args, **kwargs)

    def build(self, key, *args, **kwargs):
        fu = self.prepare(key, *args, **kwargs)
        return fu()

    def key_from_instance(self, cls):
        for key, clbk in self._factories.items():
            if isclass(clbk) and isinstance(cls, clbk):
                return key
            if not isclass(clbk) and cls == clbk:
                return key
        raise KeyError(type(cls))

## EOF ##