from __future__ import absolute_import

import sys

from collections import *

from .version_info import PY2

if PY2:
    from UserString import *
    from UserList import *

    if sys.version_info < (2, 7):
        from ordereddict import OrderedDict

if sys.version_info < (3, 3):        
    if PY2:
        try:
            from thread import get_ident
        except ImportError:
            from dummy_thread import get_ident
    else:
        try:
            from _thread import get_ident
        except ImportError:
            from _dummy_thread import get_ident
    
    def _recursive_repr(fillvalue='...'):
        'Decorator to make a repr function return fillvalue for a recursive call'

        def decorating_function(user_function):
            repr_running = set()

            def wrapper(self):
                key = id(self), get_ident()
                if key in repr_running:
                    return fillvalue
                repr_running.add(key)
                try:
                    result = user_function(self)
                finally:
                    repr_running.discard(key)
                return result

            # Can't use functools.wraps() here because of bootstrap issues
            wrapper.__module__ = getattr(user_function, '__module__')
            wrapper.__doc__ = getattr(user_function, '__doc__')
            wrapper.__name__ = getattr(user_function, '__name__')
            wrapper.__annotations__ = getattr(
                user_function, '__annotations__', {})
            return wrapper

        return decorating_function

    class ChainMap(MutableMapping):
        ''' A ChainMap groups multiple dicts (or other mappings) together
        to create a single, updateable view.

        The underlying mappings are stored in a list.  That list is public and can
        accessed or updated using the *maps* attribute.  There is no other state.

        Lookups search the underlying mappings successively until a key is found.
        In contrast, writes, updates, and deletions only operate on the first
        mapping.

        '''

        def __init__(self, *maps):
            '''Initialize a ChainMap by setting *maps* to the given mappings.
            If no mappings are provided, a single empty dictionary is used.

            '''
            self.maps = list(maps) or [{}]          # always at least one map

        def __missing__(self, key):
            raise KeyError(key)

        def __getitem__(self, key):
            for mapping in self.maps:
                try:
                    # can't use 'key in mapping' with defaultdict
                    return mapping[key]
                except KeyError:
                    pass
            # support subclasses that define __missing__
            return self.__missing__(key)

        def get(self, key, default=None):
            return self[key] if key in self else default

        def __len__(self):
            # reuses stored hash values if possible
            return len(set().union(*self.maps))

        def __iter__(self):
            return iter(set().union(*self.maps))

        def __contains__(self, key):
            return any(key in m for m in self.maps)

        def __bool__(self):
            return any(self.maps)

        @_recursive_repr()
        def __repr__(self):
            return '{0.__class__.__name__}({1})'.format(
                self, ', '.join(map(repr, self.maps)))

        @classmethod
        def fromkeys(cls, iterable, *args):
            'Create a ChainMap with a single dict created from the iterable.'
            return cls(dict.fromkeys(iterable, *args))

        def copy(self):
            'New ChainMap or subclass with a new copy of maps[0] and refs to maps[1:]'
            return self.__class__(self.maps[0].copy(), *self.maps[1:])

        __copy__ = copy

        def new_child(self, m=None):                # like Django's Context.push()
            '''
            New ChainMap with a new map followed by all previous maps. If no
            map is provided, an empty dict is used.
            '''
            if m is None:
                m = {}
            return self.__class__(m, *self.maps)

        @property
        def parents(self):                          # like Django's Context.pop()
            'New ChainMap from maps[1:].'
            return self.__class__(*self.maps[1:])

        def __setitem__(self, key, value):
            self.maps[0][key] = value

        def __delitem__(self, key):
            try:
                del self.maps[0][key]
            except KeyError:
                raise KeyError(
                    'Key not found in the first mapping: {!r}'.format(key))

        def popitem(self):
            'Remove and return an item pair from maps[0]. Raise KeyError is maps[0] is empty.'
            try:
                return self.maps[0].popitem()
            except KeyError:
                raise KeyError('No keys found in the first mapping.')

        def pop(self, key, *args):
            'Remove *key* from maps[0] and return its value. Raise KeyError if *key* not in maps[0].'
            try:
                return self.maps[0].pop(key, *args)
            except KeyError:
                raise KeyError(
                    'Key not found in the first mapping: {!r}'.format(key))

        def clear(self):
            'Clear maps[0], leaving maps[1:] intact.'
            self.maps[0].clear()