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callchain / callchain / core.py

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# -*- coding: utf-8 -*-
'''callchain core mixins'''

from threading import local
from operator import setitem

from stuf.six import items
from stuf import frozenstuf
from appspace.keys import AppLookupError, NoAppError
from stuf.utils import getcls, either, lazy, lazybase, exhaustmap


class ResetTypeMixin(object):

    '''`reset` descriptors that subclass `lazybase`'''

    def reset(self):
        '''reset previously accessed `lazybase` attributes'''
        this = vars(self)
        t = lambda x, y: x in this and isinstance(y, lazybase)
        exhaustmap(items(vars(getcls(self))), delattr, t)


class ResetLocalMixin(local):

    '''`reset` descriptors that subclass `lazybase`'''

    def reset(self):
        '''reset previously accessed `lazybase` attributes'''
        this = vars(self)
        t = lambda x, y: x in this and isinstance(y, lazybase)
        exhaustmap(items(vars(getcls(self))), delattr, t)


class CoreMixin(ResetLocalMixin):

    '''core mixin'''

    def __init__(self, root):
        '''
        init

        @param root: root chain
        '''
        super(CoreMixin, self).__init__()
        self._setup(root)

    def __getattr__(self, label):
        try:
            return object.__getattribute__(self, label)
        except AttributeError:
            return self._load(label)

    @either
    def G(self):
        '''external application global settings'''
        return self.M.settings.final if self.M is not None else frozenstuf()

    @either
    def L(self):
        '''local settings'''
        return self._M.localize(self) if self._M is not None else frozenstuf()

    def _setup(self, root):
        '''call chain setup'''

    def _load(self, label):
        '''
        load thing from appspace

        @param label: label of appspaced thing
        '''
        _M = self._M
        try:
            # get appspace thing
            thing = _M.get(label, _M._current)
        except AppLookupError:
            try:
                # verify namespace
                _M.namespace(label)
            except AppLookupError:
                raise NoAppError(label)
            else:
                # temporarily swap current label
                _M._current = label
                return self
        else:
            # set current label back to root label
            _M._current = _M._root
            return thing


class ConfigMixin(CoreMixin):

    '''configuration access mixin'''

    @lazy
    def defaults(self):
        '''default settings by their lonesome'''
        return self.M.settings.defaults if self.M is not None else frozenstuf()

    @lazy
    def required(self):
        '''required settings by their lonesome'''
        return self.M.settings.required if self.M is not None else frozenstuf()

    def _defaults(self):
        '''reset attribute values'''
        this = self.__dict__
        self.exhaustitems(
            vars(self),
            lambda x, y: setitem(this, x.rstrip('_d'), y),
            lambda x: x[0].endswith('_d'),
        )

    def _setdefault(self, key, value):
        '''
        set default value for instance attribute

        @param key: attribute name
        @param value: attribute value
        '''
        self.__dict__[key] = self.__dict__[key + '_d'] = value