"""Module to handle features that are not implemented yet."""


_IGNORED_FEATURES = {
    'collation': False,
    'session': False,
}


def _ensure_ignorable_feature(feature):
    if feature not in _IGNORED_FEATURES:
        raise KeyError(
            '%s is not an error that can be ignored: maybe it has been implemented in Mongomock. '
            'Here is the list of features that can be ignored: %s' % (
                feature, _IGNORED_FEATURES.keys()))


def ignore_feature(feature):
    """Ignore a feature instead of raising a NotImplementedError."""
    _ensure_ignorable_feature(feature)
    _IGNORED_FEATURES[feature] = True


def warn_on_feature(feature):
    """Rasie a NotImplementedError the next times a feature is used."""
    _ensure_ignorable_feature(feature)
    _IGNORED_FEATURES[feature] = False


def raise_for_feature(feature, reason):
    _ensure_ignorable_feature(feature)
    if _IGNORED_FEATURES[feature]:
        return False
    raise NotImplementedError(reason)