"""

Extended JSON encoder for json

"""

import datetime

import functools

import decimal

import json # is re-exported after monkey patching

__all__ = ['json']

def _is_tz_aware(value):

    """

    Determines if a given datetime.time is timezone aware.

    The logic is described in Python's docs:

    http://docs.python.org/library/datetime.html#datetime.tzinfo

    """

    return (value.tzinfo is not None

            and value.tzinfo.utcoffset(value) is not None)

def _obj_dump(obj):

    """

    Custom function for dumping objects to JSON, if obj has __json__ attribute

    or method defined it will be used for serialization

    :param obj:

    """

    if isinstance(obj, complex):

        return [obj.real, obj.imag]

    # See "Date Time String Format" in the ECMA-262 specification.

    # some code borrowed from django 1.4

    elif isinstance(obj, datetime.datetime):

        r = obj.isoformat()

        if obj.microsecond:

            r = r[:23] + r[26:]

        if r.endswith('+00:00'):

            r = r[:-6] + 'Z'

        return r

    elif isinstance(obj, datetime.date):

        return obj.isoformat()

    elif isinstance(obj, decimal.Decimal):

        return str(obj)

    elif isinstance(obj, datetime.time):

        if _is_tz_aware(obj):

            raise ValueError("JSON can't represent timezone-aware times.")

        r = obj.isoformat()

        if obj.microsecond:

            r = r[:12]

        return r

    elif isinstance(obj, set):

        return list(obj)

    elif hasattr(obj, '__json__'):

        if callable(obj.__json__):

            return obj.__json__()

        else:

            return obj.__json__

    else:

        raise NotImplementedError

class ExtendedEncoder(json.JSONEncoder):

    def default(self, obj):

        try:

            return _obj_dump(obj)

        except NotImplementedError:

            pass

        raise TypeError("%r is not JSON serializable" % (obj,))

# monkey-patch and export JSON encoder to use custom encoding method

json.dumps = functools.partial(json.dumps, cls=ExtendedEncoder)

json.dump = functools.partial(json.dump, cls=ExtendedEncoder)