from __future__ import unicode_literals

import copy
import inspect
import warnings
from itertools import chain

from django.apps import apps
from django.conf import settings
from django.core import checks
from django.core.exceptions import (
    NON_FIELD_ERRORS, FieldDoesNotExist, FieldError, MultipleObjectsReturned,
    ObjectDoesNotExist, ValidationError,
)
from django.db import (
    DEFAULT_DB_ALIAS, DJANGO_VERSION_PICKLE_KEY, DatabaseError, connections,
    router, transaction,
)
from django.db.models import signals
from django.db.models.constants import LOOKUP_SEP
from django.db.models.deletion import CASCADE, Collector
from django.db.models.fields import AutoField
from django.db.models.fields.related import (
    ForeignObjectRel, ManyToOneRel, OneToOneField, lazy_related_operation,
    resolve_relation,
)
from django.db.models.manager import ensure_default_manager
from django.db.models.options import Options
from django.db.models.query import Q
from django.db.models.query_utils import (
    DeferredAttribute, deferred_class_factory,
)
from django.db.models.utils import make_model_tuple
from django.utils import six
from django.utils.encoding import force_str, force_text
from django.utils.functional import curry
from django.utils.six.moves import zip
from django.utils.text import capfirst, get_text_list
from django.utils.translation import ugettext_lazy as _
from django.utils.version import get_version


def subclass_exception(name, parents, module, attached_to=None):
    """
    Create exception subclass. Used by ModelBase below.

    If 'attached_to' is supplied, the exception will be created in a way that
    allows it to be pickled, assuming the returned exception class will be added
    as an attribute to the 'attached_to' class.
    """
    class_dict = {'__module__': module}
    if attached_to is not None:
        def __reduce__(self):
            # Exceptions are special - they've got state that isn't
            # in self.__dict__. We assume it is all in self.args.
            return (unpickle_inner_exception, (attached_to, name), self.args)

        def __setstate__(self, args):
            self.args = args

        class_dict['__reduce__'] = __reduce__
        class_dict['__setstate__'] = __setstate__

    return type(name, parents, class_dict)


class ModelBase(type):
    """
    Metaclass for all models.
    """
    def __new__(cls, name, bases, attrs):
        super_new = super(ModelBase, cls).__new__

        # Also ensure initialization is only performed for subclasses of Model
        # (excluding Model class itself).
        parents = [b for b in bases if isinstance(b, ModelBase)]
        if not parents:
            return super_new(cls, name, bases, attrs)

        # Create the class.
        module = attrs.pop('__module__')
        new_class = super_new(cls, name, bases, {'__module__': module})
        attr_meta = attrs.pop('Meta', None)
        abstract = getattr(attr_meta, 'abstract', False)
        if not attr_meta:
            meta = getattr(new_class, 'Meta', None)
        else:
            meta = attr_meta
        base_meta = getattr(new_class, '_meta', None)

        app_label = None

        # Look for an application configuration to attach the model to.
        app_config = apps.get_containing_app_config(module)

        if getattr(meta, 'app_label', None) is None:
            if app_config is None:
                if not abstract:
                    raise RuntimeError(
                        "Model class %s.%s doesn't declare an explicit "
                        "app_label and isn't in an application in "
                        "INSTALLED_APPS." % (module, name)
                    )

            else:
                app_label = app_config.label

        new_class.add_to_class('_meta', Options(meta, app_label))
        if not abstract:
            new_class.add_to_class(
                'DoesNotExist',
                subclass_exception(
                    str('DoesNotExist'),
                    tuple(
                        x.DoesNotExist for x in parents if hasattr(x, '_meta') and not x._meta.abstract
                    ) or (ObjectDoesNotExist,),
                    module,
                    attached_to=new_class))
            new_class.add_to_class(
                'MultipleObjectsReturned',
                subclass_exception(
                    str('MultipleObjectsReturned'),
                    tuple(
                        x.MultipleObjectsReturned for x in parents if hasattr(x, '_meta') and not x._meta.abstract
                    ) or (MultipleObjectsReturned,),
                    module,
                    attached_to=new_class))
            if base_meta and not base_meta.abstract:
                # Non-abstract child classes inherit some attributes from their
                # non-abstract parent (unless an ABC comes before it in the
                # method resolution order).
                if not hasattr(meta, 'ordering'):
                    new_class._meta.ordering = base_meta.ordering
                if not hasattr(meta, 'get_latest_by'):
                    new_class._meta.get_latest_by = base_meta.get_latest_by

        is_proxy = new_class._meta.proxy

        # If the model is a proxy, ensure that the base class
        # hasn't been swapped out.
        if is_proxy and base_meta and base_meta.swapped:
            raise TypeError("%s cannot proxy the swapped model '%s'." % (name, base_meta.swapped))

        if getattr(new_class, '_default_manager', None):
            if not is_proxy:
                # Multi-table inheritance doesn't inherit default manager from
                # parents.
                new_class._default_manager = None
                new_class._base_manager = None
            else:
                # Proxy classes do inherit parent's default manager, if none is
                # set explicitly.
                new_class._default_manager = new_class._default_manager._copy_to_model(new_class)
                new_class._base_manager = new_class._base_manager._copy_to_model(new_class)

        # Add all attributes to the class.
        for obj_name, obj in attrs.items():
            new_class.add_to_class(obj_name, obj)

        # All the fields of any type declared on this model
        new_fields = chain(
            new_class._meta.local_fields,
            new_class._meta.local_many_to_many,
            new_class._meta.virtual_fields
        )
        field_names = {f.name for f in new_fields}

        # Basic setup for proxy models.
        if is_proxy:
            base = None
            for parent in [kls for kls in parents if hasattr(kls, '_meta')]:
                if parent._meta.abstract:
                    if parent._meta.fields:
                        raise TypeError(
                            "Abstract base class containing model fields not "
                            "permitted for proxy model '%s'." % name
                        )
                    else:
                        continue
                if base is not None:
                    raise TypeError("Proxy model '%s' has more than one non-abstract model base class." % name)
                else:
                    base = parent
            if base is None:
                raise TypeError("Proxy model '%s' has no non-abstract model base class." % name)
            new_class._meta.setup_proxy(base)
            new_class._meta.concrete_model = base._meta.concrete_model
            base._meta.concrete_model._meta.proxied_children.append(new_class._meta)
        else:
            new_class._meta.concrete_model = new_class

        # Collect the parent links for multi-table inheritance.
        parent_links = {}
        for base in reversed([new_class] + parents):
            # Conceptually equivalent to `if base is Model`.
            if not hasattr(base, '_meta'):
                continue
            # Skip concrete parent classes.
            if base != new_class and not base._meta.abstract:
                continue
            # Locate OneToOneField instances.
            for field in base._meta.local_fields:
                if isinstance(field, OneToOneField):
                    related = resolve_relation(new_class, field.remote_field.model)
                    parent_links[make_model_tuple(related)] = field
        # Do the appropriate setup for any model parents.
        for base in parents:
            original_base = base
            if not hasattr(base, '_meta'):
                # Things without _meta aren't functional models, so they're
                # uninteresting parents.
                continue

            parent_fields = base._meta.local_fields + base._meta.local_many_to_many
            # Check for clashes between locally declared fields and those
            # on the base classes (we cannot handle shadowed fields at the
            # moment).
            for field in parent_fields:
                if field.name in field_names:
                    raise FieldError(
                        'Local field %r in class %r clashes '
                        'with field of similar name from '
                        'base class %r' % (field.name, name, base.__name__)
                    )
            if not base._meta.abstract:
                # Concrete classes...
                base = base._meta.concrete_model
                base_key = make_model_tuple(base)
                if base_key in parent_links:
                    field = parent_links[base_key]
                elif not is_proxy:
                    attr_name = '%s_ptr' % base._meta.model_name
                    field = OneToOneField(
                        base,
                        on_delete=CASCADE,
                        name=attr_name,
                        auto_created=True,
                        parent_link=True,
                    )
                    # Only add the ptr field if it's not already present;
                    # e.g. migrations will already have it specified
                    if not hasattr(new_class, attr_name):
                        new_class.add_to_class(attr_name, field)
                else:
                    field = None
                new_class._meta.parents[base] = field
            else:
                base_parents = base._meta.parents.copy()

                # .. and abstract ones.
                for field in parent_fields:
                    new_field = copy.deepcopy(field)
                    new_class.add_to_class(field.name, new_field)
                    # Replace parent links defined on this base by the new
                    # field as it will be appropriately resolved if required.
                    if field.one_to_one:
                        for parent, parent_link in base_parents.items():
                            if field == parent_link:
                                base_parents[parent] = new_field

                # Pass any non-abstract parent classes onto child.
                new_class._meta.parents.update(base_parents)

            # Inherit managers from the abstract base classes.
            new_class.copy_managers(base._meta.abstract_managers)

            # Proxy models inherit the non-abstract managers from their base,
            # unless they have redefined any of them.
            if is_proxy:
                new_class.copy_managers(original_base._meta.concrete_managers)

            # Inherit virtual fields (like GenericForeignKey) from the parent
            # class
            for field in base._meta.virtual_fields:
                if base._meta.abstract and field.name in field_names:
                    raise FieldError(
                        'Local field %r in class %r clashes '
                        'with field of similar name from '
                        'abstract base class %r' % (field.name, name, base.__name__)
                    )
                new_class.add_to_class(field.name, copy.deepcopy(field))

        if abstract:
            # Abstract base models can't be instantiated and don't appear in
            # the list of models for an app. We do the final setup for them a
            # little differently from normal models.
            attr_meta.abstract = False
            new_class.Meta = attr_meta
            return new_class

        new_class._prepare()
        new_class._meta.apps.register_model(new_class._meta.app_label, new_class)
        return new_class

    def copy_managers(cls, base_managers):
        # This is in-place sorting of an Options attribute, but that's fine.
        base_managers.sort()
        for _, mgr_name, manager in base_managers:  # NOQA (redefinition of _)
            val = getattr(cls, mgr_name, None)
            if not val or val is manager:
                new_manager = manager._copy_to_model(cls)
                cls.add_to_class(mgr_name, new_manager)

    def add_to_class(cls, name, value):
        # We should call the contribute_to_class method only if it's bound
        if not inspect.isclass(value) and hasattr(value, 'contribute_to_class'):
            value.contribute_to_class(cls, name)
        else:
            setattr(cls, name, value)

    def _prepare(cls):
        """
        Creates some methods once self._meta has been populated.
        """
        opts = cls._meta
        opts._prepare(cls)

        if opts.order_with_respect_to:
            cls.get_next_in_order = curry(cls._get_next_or_previous_in_order, is_next=True)
            cls.get_previous_in_order = curry(cls._get_next_or_previous_in_order, is_next=False)

            # Defer creating accessors on the foreign class until it has been
            # created and registered. If remote_field is None, we're ordering
            # with respect to a GenericForeignKey and don't know what the
            # foreign class is - we'll add those accessors later in
            # contribute_to_class().
            if opts.order_with_respect_to.remote_field:
                wrt = opts.order_with_respect_to
                remote = wrt.remote_field.model
                lazy_related_operation(make_foreign_order_accessors, cls, remote)

        # Give the class a docstring -- its definition.
        if cls.__doc__ is None:
            cls.__doc__ = "%s(%s)" % (cls.__name__, ", ".join(f.name for f in opts.fields))

        get_absolute_url_override = settings.ABSOLUTE_URL_OVERRIDES.get(opts.label_lower)
        if get_absolute_url_override:
            setattr(cls, 'get_absolute_url', get_absolute_url_override)

        ensure_default_manager(cls)
        signals.class_prepared.send(sender=cls)


class ModelState(object):
    """