import copy
from datetime import date, datetime
from importlib import import_module

import django
from django.conf import settings
from django.core.exceptions import FieldError
from django.db.models import fields
from django.utils import dateparse, timezone

try:
    from functools import partialmethod
except ImportError:
    # python 2.7, so we are on django 1.11
    from django.utils.functional import curry as partialmethod


def JSONField(*args, **kwargs):
    """
    Returns json field implementation depends on the
    default db connection type or `db_vendor` keyword argument
    """
    db_vendor = kwargs.pop('db_vendor', None)
    if db_vendor is None:
        backend = import_module('{}.base'.format(settings.DATABASES['default']['ENGINE']).replace('_psycopg2', ''))
        db_vendor = backend.DatabaseWrapper.vendor

    try:
        from django.db.models import JSONField as DJ_JSONField
        return DJ_JSONField(*args, **kwargs)
    except ImportError:
        pass
        
    if db_vendor == 'postgresql':
        from django.contrib.postgres.fields import JSONField as PG_JSONField
        return PG_JSONField(*args, **kwargs)
    elif db_vendor == 'mysql':
        try:
            from django_mysql.models import JSONField as MY_JSONField
        except ImportError:
            raise ImportError("django-mysql isn't installed")
        else:
            return MY_JSONField(*args, **kwargs)
    elif db_vendor == 'oracle':
        try:
            from oracle_json_field.fields import JSONField as OR_JSONField
        except ImportError:
            raise ImportError("oracle-json-field isn't installed")
        else:
            return OR_JSONField(*args, **kwargs)
    else:
        if django.VERSION >= (3, 0):
            # Quick six for django-annoying
            import six
            from django import utils
            utils.six = six

        try:
            from annoying.fields import JSONField as DEFAULT_JSONField
        except ImportError:
            raise ImportError("django-annoying isn't installed")
        else:
            return DEFAULT_JSONField(*args, **kwargs)


class JSONFieldDescriptor(object):
    def __init__(self, field):
        self.field = field

    def __get__(self, instance, cls=None):
        if instance is None:
            return self
        json_value = getattr(instance, self.field.json_field_name)
        if isinstance(json_value, dict):
            value = json_value.get(self.field.attname, None)
            if hasattr(self.field, 'from_json'):
                value = self.field.from_json(value)
            return value
        return None

    def __set__(self, instance, value):
        json_value = getattr(instance, self.field.json_field_name)
        if json_value:
            assert isinstance(json_value, dict)
        else:
            json_value = {}

        if hasattr(self.field, 'to_json'):
            value = self.field.to_json(value)

        if not value and self.field.blank and not self.field.null:
            try:
                del json_value[self.field.attname]
            except KeyError:
                pass
        else:
            json_value[self.field.attname] = value

        setattr(instance, self.field.json_field_name, json_value)


class JSONFieldMixin(object):
    """
    Override django.db.model.fields.Field.contribute_to_class
    to make a field always private, and register custom access descriptor
    """
    def __init__(self, *args, **kwargs):
        self.json_field_name = kwargs.pop('json_field_name', 'data')
        super(JSONFieldMixin, self).__init__(*args, **kwargs)

    def contribute_to_class(self, cls, name, private_only=False):
        self.set_attributes_from_name(name)
        self.model = cls
        self.concrete = False
        self.column = self.json_field_name
        cls._meta.add_field(self, private=True)

        if not getattr(cls, self.attname, None):
            descriptor = JSONFieldDescriptor(self)
            setattr(cls, self.attname, descriptor)

        if self.choices is not None:
            setattr(cls, 'get_%s_display' % self.name,
                    partialmethod(cls._get_FIELD_display, field=self))

    def get_lookup(self, lookup_name):
        # Always return None, to make get_transform been called
        return None

    def get_transform(self, name):
        class TransformFactoryWrapper:
            def __init__(self, json_field, transform, original_lookup):
                self.json_field = json_field
                self.transform = transform
                self.original_lookup = original_lookup

            def __call__(self, lhs, **kwargs):
                lhs = copy.copy(lhs)
                lhs.target = self.json_field
                lhs.output_field = self.json_field
                transform = self.transform(lhs, **kwargs)
                transform._original_get_lookup = transform.get_lookup
                transform.get_lookup = lambda name: transform._original_get_lookup(self.original_lookup)
                return transform

        json_field = self.model._meta.get_field(self.json_field_name)
        transform = json_field.get_transform(self.name)
        if transform is None:
            raise FieldError(
                "JSONField '%s' has no support for key '%s' %s lookup" %
                (self.json_field_name, self.name, name)
            )

        return TransformFactoryWrapper(json_field, transform, name)

    def convert_json_value(self, value, expression, connection):
        if isinstance(value, str):
            import json
            return json.loads(value)[self.name]
        return value

    def get_db_converters(self, connection):
        converters = super().get_db_converters(connection)
        converters += [self.convert_json_value]
        return converters


class BooleanField(JSONFieldMixin, fields.BooleanField):
    def __init__(self, *args, **kwargs):
        super(BooleanField, self).__init__(*args, **kwargs)
        if django.VERSION < (2, ):
            self.blank = False


class CharField(JSONFieldMixin, fields.CharField):
    pass


class DateField(JSONFieldMixin, fields.DateField):
    def to_json(self, value):
        if value:
            assert isinstance(value, (datetime, date))
            return value.strftime('%Y-%m-%d')

    def from_json(self, value):
        if value is not None:
            return dateparse.parse_date(value)


class DateTimeField(JSONFieldMixin, fields.DateTimeField):
    def to_json(self, value):
        if value:
            if not timezone.is_aware(value):
                value = timezone.make_aware(value)
            return value.isoformat()

    def from_json(self, value):
        if value:
            return dateparse.parse_datetime(value)


class DecimalField(JSONFieldMixin, fields.DecimalField):
    pass


class EmailField(JSONFieldMixin, fields.EmailField):
    pass


class FloatField(JSONFieldMixin, fields.FloatField):
    pass


class IntegerField(JSONFieldMixin, fields.IntegerField):
    pass


class IPAddressField(JSONFieldMixin, fields.IPAddressField):
    pass


class GenericIPAddressField(JSONFieldMixin, fields.GenericIPAddressField):
    pass


class NullBooleanField(JSONFieldMixin, fields.NullBooleanField):
    pass


class TextField(JSONFieldMixin, fields.TextField):
    pass


class TimeField(JSONFieldMixin, fields.TimeField):
    def to_json(self, value):
        if value:
            if not timezone.is_aware(value):
                value = timezone.make_aware(value)
            return value.isoformat()

    def from_json(self, value):
        if value:
            return dateparse.parse_time(value)


class URLField(JSONFieldMixin, fields.URLField):
    pass