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 =„    	"""JSON (de)serialization framework.

The framework presented here is somewhat based on `Go's "json" package`_
(especially the ``omitempty`` functionality).

.. _`Go's "json" package`: http://golang.org/pkg/encoding/json/

"""
import abc
import binascii
import logging

import OpenSSL
import six

from josepy import b64, errors, interfaces, util

logger = logging.getLogger(__name__)


class Field(object):
    """JSON object field.

    :class:`Field` is meant to be used together with
    :class:`JSONObjectWithFields`.

    ``encoder`` (``decoder``) is a callable that accepts a single
    parameter, i.e. a value to be encoded (decoded), and returns the
    serialized (deserialized) value. In case of errors it should raise
    :class:`~josepy.errors.SerializationError`
    (:class:`~josepy.errors.DeserializationError`).

    Note, that ``decoder`` should perform partial serialization only.

    :ivar str json_name: Name of the field when encoded to JSON.
    :ivar default: Default value (used when not present in JSON object).
    :ivar bool omitempty: If ``True`` and the field value is empty, then
        it will not be included in the serialized JSON object, and
        ``default`` will be used for deserialization. Otherwise, if ``False``,
        field is considered as required, value will always be included in the
        serialized JSON objected, and it must also be present when
        deserializing.

    """
    __slots__ = ('json_name', 'default', 'omitempty', 'fdec', 'fenc')

    def __init__(self, json_name, default=None, omitempty=False,
                 decoder=None, encoder=None):
        # pylint: disable=too-many-arguments
        self.json_name = json_name
        self.default = default
        self.omitempty = omitempty

        self.fdec = self.default_decoder if decoder is None else decoder
        self.fenc = self.default_encoder if encoder is None else encoder

    @classmethod
    def _empty(cls, value):
        """Is the provided value considered "empty" for this field?

        This is useful for subclasses that might want to override the
        definition of being empty, e.g. for some more exotic data types.

        """
        return not isinstance(value, bool) and not value

    def omit(self, value):
        """Omit the value in output?"""
        return self._empty(value) and self.omitempty

    def _update_params(self, **kwargs):
        current = dict(json_name=self.json_name, default=self.default,
                       omitempty=self.omitempty,
                       decoder=self.fdec, encoder=self.fenc)
        current.update(kwargs)
        return type(self)(**current)  # pylint: disable=star-args

    def decoder(self, fdec):
        """Descriptor to change the decoder on JSON object field."""
        return self._update_params(decoder=fdec)

    def encoder(self, fenc):
        """Descriptor to change the encoder on JSON object field."""
        return self._update_params(encoder=fenc)

    def decode(self, value):
        """Decode a value, optionally with context JSON object."""
        return self.fdec(value)

    def encode(self, value):
        """Encode a value, optionally with context JSON object."""
        return self.fenc(value)

    @classmethod
    def default_decoder(cls, value):
        """Default decoder.

        Recursively deserialize into immutable types (
        :class:`josepy.util.frozendict` instead of
        :func:`dict`, :func:`tuple` instead of :func:`list`).

        """
        # bases cases for different types returned by json.loads
        if isinstance(value, list):
            return tuple(cls.default_decoder(subvalue) for subvalue in value)
        elif isinstance(value, dict):
            return util.frozendict(
                dict((cls.default_decoder(key), cls.default_decoder(value))
                     for key, value in six.iteritems(value)))
        else:  # integer or string
            return value

    @classmethod
    def default_encoder(cls, value):
        """Default (passthrough) encoder."""
        # field.to_partial_json() is n