"""

YAML serializer.

Requires PyYaml (http://pyyaml.org/), but that's checked for in __init__.

"""

from StringIO import StringIO

import decimal

import yaml

from django.db import models

from django.core.serializers.python import Serializer as PythonSerializer

from django.core.serializers.python import Deserializer as PythonDeserializer

class DjangoSafeDumper(yaml.SafeDumper):

    def represent_decimal(self, data):

        return self.represent_scalar('tag:yaml.org,2002:str', str(data))

DjangoSafeDumper.add_representer(decimal.Decimal, DjangoSafeDumper.represent_decimal)

class Serializer(PythonSerializer):

    """

    Convert a queryset to YAML.

    """

    internal_use_only = False

    def handle_field(self, obj, field):

        # A nasty special case: base YAML doesn't support serialization of time

        # types (as opposed to dates or datetimes, which it does support). Since

        # we want to use the "safe" serializer for better interoperability, we

        # need to do something with those pesky times. Converting 'em to strings

        # isn't perfect, but it's better than a "!!python/time" type which would

        # halt deserialization under any other language.

        if isinstance(field, models.TimeField) and getattr(obj, field.name) is not None:

            self._current[field.name] = str(getattr(obj, field.name))

        else:

            super(Serializer, self).handle_field(obj, field)

    def end_serialization(self):

        self.options.pop('stream', None)

        self.options.pop('fields', None)

        self.options.pop('use_natural_keys', None)

        yaml.dump(self.objects, self.stream, Dumper=DjangoSafeDumper, **self.options)

    def getvalue(self):

        return self.stream.getvalue()

def Deserializer(stream_or_string, **options):

    """

    Deserialize a stream or string of YAML data.

    """

    if isinstance(stream_or_string, basestring):

        stream = StringIO(stream_or_string)

    else:

        stream = stream_or_string

    for obj in PythonDeserializer(yaml.load(stream), **options):

        yield obj