# -*- coding: utf-8 -*-
# Copyright 2009-2020 Joshua Bronson. All Rights Reserved.
#
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.


#==============================================================================
#                    * Welcome to the bidict source code *
#==============================================================================

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#==============================================================================
#← Prev: _orderedbase.py  Current: _frozenordered.py  Next: _orderedbidict.py →
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"""Provide :class:`FrozenOrderedBidict`, an immutable, hashable, ordered bidict."""

import typing as _t

from ._frozenbidict import frozenbidict
from ._orderedbase import OrderedBidictBase
from ._typing import KT, VT


class FrozenOrderedBidict(OrderedBidictBase[KT, VT]):
    """Hashable, immutable, ordered bidict type."""

    __slots__ = ()
    __hash__ = frozenbidict.__hash__

    if _t.TYPE_CHECKING:
        @property
        def inverse(self) -> 'FrozenOrderedBidict[VT, KT]': ...

    # Assume the Python implementation's dict type is ordered (e.g. PyPy or CPython >= 3.6), so we
    # can delegate to `_fwdm` and `_invm` for faster implementations of several methods. Both
    # `_fwdm` and `_invm` will always be initialized with the provided items in the correct order,
    # and since `FrozenOrderedBidict` is immutable, their respective orders can't get out of sync
    # after a mutation.
    def __iter__(self) -> _t.Iterator[KT]:
        """Iterator over the contained keys in insertion order."""
        return self._iter()

    def _iter(self, *, reverse: bool = False) -> _t.Iterator[KT]:
        if reverse:
            return super()._iter(reverse=True)
        return iter(self._fwdm._fwdm)

    def keys(self) -> _t.KeysView[KT]:
        """A set-like object providing a view on the contained keys."""
        return self._fwdm._fwdm.keys()

    def values(self) -> _t.KeysView[VT]:  # type: ignore
        """A set-like object providing a view on the contained values."""
        return self._invm._fwdm.keys()

    # We can't delegate for items because values in `_fwdm` are nodes.


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