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# encoding=utf-8
import json
import warnings

from django.core.serializers.json import DjangoJSONEncoder
from django.db import models
from django.db.models.query import QuerySet
from django.utils import six
from django.utils.deprecation import RemovedInDjango19Warning
from django.utils.encoding import force_text, is_protected_type


def serialize(obj):
    '''
    返回字典类型
    :param format:
    :param obj:
    :return:
    '''
    if isinstance(obj, QuerySet):
        return json.loads(djserialize('json', obj))
    if isinstance(obj, models.Model):
        return json.loads(djserialize('json', [obj])[1:-1])
    if hasattr(obj, 'isoformat'):
        return obj.isoformat()
    return obj


def djserialize(format, queryset, **options):
    """
    Serialize a queryset (or any iterator that returns database objects) using
    a certain serializer.
    """
    s = JsonSerializer()
    s.serialize(queryset, **options)
    return s.getvalue()


class Serializer(object):
    """
    django.core.serializers 里面的serialize类不能序列化父类的属性,所以拷贝过来改了改
    Abstract serializer base class.
    """

    # Indicates if the implemented serializer is only available for
    # internal Django use.
    internal_use_only = False

    def serialize(self, queryset, **options):
        """
        Serialize a queryset.
        """
        self.options = options

        self.stream = options.pop("stream", six.StringIO())
        self.selected_fields = options.pop("fields", None)
        self.use_natural_keys = options.pop("use_natural_keys", False)
        if self.use_natural_keys:
            warnings.warn("``use_natural_keys`` is deprecated; use ``use_natural_foreign_keys`` instead.",
                          RemovedInDjango19Warning)
        self.use_natural_foreign_keys = options.pop('use_natural_foreign_keys', False) or self.use_natural_keys
        self.use_natural_primary_keys = options.pop('use_natural_primary_keys', False)

        self.start_serialization()
        self.first = True
        for obj in queryset:
            self.start_object(obj)
            # Use the concrete parent class' _meta instead of the object's _meta
            # This is to avoid local_fields problems for proxy models. Refs #17717.
            concrete_model = obj._meta.concrete_model
            for field in concrete_model._meta.fields:
                # django 中是local_fields,不能显示父类内容
                if field.serialize:
                    if field.rel is None:
                        if self.selected_fields is None or field.attname in self.selected_fields:
                            self.handle_field(obj, field)
                    else:
                        if self.selected_fields is None or field.attname[:-3] in self.selected_fields:
                            self.handle_fk_field(obj, field)
            for field in concrete_model._meta.many_to_many:
                if field.serialize:
                    if self.selected_fields is None or field.attname in self.selected_fields:
                        self.handle_m2m_field(obj, field)
            self.end_object(obj)
            if self.first:
                self.first = False
        self.end_serialization()
        return self.getvalue()

    def start_serialization(self):
        """
        Called when serializing of the queryset starts.
        """
        raise NotImplementedError('subclasses of Serializer must provide a start_serialization() method')

    def end_serialization(self):
        """
        Called when serializing of the queryset ends.
        """
        pass

    def start_object(self, obj):
        """
        Called when serializing of an object starts.
        """
        raise NotImplementedError('subclasses of Serializer must provide a start_object() method')

    def end_object(self, obj):
        """
        Called when serializing of an object ends.
        """
        pass

    def handle_field(self, obj, field):
        """
        Called to handle each individual (non-relational) field on an object.
        """
        raise NotImplementedError('subclasses of Serializer must provide an handle_field() method')

    def handle_fk_field(self, obj, field):
        """
        Called to handle a ForeignKey field.
        """
        raise NotImplementedError('subclasses of Serializer must provide an handle_fk_field() method')

    def handle_m2m_field(self, obj, field):
        """
        Called to handle a ManyToManyField.
        """
        raise NotImplementedError('subclasses of Serializer must provide an handle_m2m_field() method')

    def getvalue(self):
        """
        Return the fully serialized queryset (or None if the output stream is
        not seekable).
        """
        if callable(getattr(self.stream, 'getvalue', None)):
            return self.stream.getvalue()


class PySerializer(Serializer):
    """
    Serializes a QuerySet to basic Python objects.
    """

    internal_use_only = True

    def start_serialization(self):
        self._current = None
        self.objects = []

    def end_serialization(self):
        pass

    def start_object(self, obj):
        self._current = {}

    def end_object(self, obj):
        self.objects.append(self.get_dump_object(obj))
        self._current = None

    def get_dump_object(self, obj):
        data = {
            "model": force_text(obj._meta),
            "fields": self._current,
        }
        if not self.use_natural_primary_keys or not hasattr(obj, 'natural_key'):
            data["pk"] = force_text(obj._get_pk_val(), strings_only=True)

        return data

    def handle_field(self, obj, field):
        value = field._get_val_from_obj(obj)
        # Protected types (i.e., primitives like None, numbers, dates,
        # and Decimals) are passed through as is. All other values are
        # converted to string first.
        if is_protected_type(value):
            self._current[field.name] = value
        else:
            self._current[field.name] = field.value_to_string(obj)

    def handle_fk_field(self, obj, field):
        if self.use_natural_foreign_keys and hasattr(field.rel.to, 'natural_key'):
            related = getattr(obj, field.name)
            if related:
                value = related.natural_key()
            else:
                value = None
        else:
            value = getattr(obj, field.get_attname())
            if not is_protected_type(value):
                value = field.value_to_string(obj)
        self._current[field.name] = value

    def handle_m2m_field(self, obj, field):
        if field.rel.through._meta.auto_created:
            if self.use_natural_foreign_keys and hasattr(field.rel.to, 'natural_key'):
                m2m_value = lambda value: value.natural_key()
            else:
                m2m_value = lambda value: force_text(value._get_pk_val(), strings_only=True)
            self._current[field.name] = [m2m_value(related)
                                         for related in getattr(obj, field.name).iterator()]

    def getvalue(self):
        return self.objects


class JsonSerializer(PySerializer):
    """
    Convert a queryset to JSON.
    """
    internal_use_only = False

    def _init_options(self):
        if json.__version__.split('.') >= ['2', '1', '3']:
            # Use JS strings to represent Python Decimal instances (ticket #16850)
            self.options.update({'use_decimal': False})
        self._current = None
        self.json_kwargs = self.options.copy()
        self.json_kwargs.pop('stream', None)
        self.json_kwargs.pop('fields', None)
        if self.options.get('indent'):
            # Prevent trailing spaces
            self.json_kwargs['separators'] = (',', ': ')

    def start_serialization(self):
        self._init_options()
        self.stream.write("[")

    def end_serialization(self):
        if self.options.get("indent"):
            self.stream.write("\n")
        self.stream.write("]")
        if self.options.get("indent"):
            self.stream.write("\n")

    def end_object(self, obj):
        # self._current has the field data
        indent = self.options.get("indent")
        if not self.first:
            self.stream.write(",")
            if not indent:
                self.stream.write(" ")
        if indent:
            self.stream.write("\n")
        json.dump(self.get_dump_object(obj), self.stream,
                  cls=DjangoJSONEncoder, **self.json_kwargs)
        self._current = None

    def getvalue(self):
        # Grand-parent super
        return super(PySerializer, self).getvalue()