from __future__ import unicode_literals

import warnings
from bisect import bisect
from collections import OrderedDict, defaultdict
from itertools import chain

from django.apps import apps
from django.conf import settings
from django.core.exceptions import FieldDoesNotExist
from django.db import connections
from django.db.models.fields import AutoField
from django.db.models.fields.proxy import OrderWrt
from django.db.models.fields.related import ManyToManyField
from django.utils import six
from django.utils.datastructures import ImmutableList, OrderedSet
from django.utils.deprecation import RemovedInDjango110Warning
from django.utils.encoding import (
    force_text, python_2_unicode_compatible, smart_text,
)
from django.utils.functional import cached_property
from django.utils.lru_cache import lru_cache
from django.utils.text import camel_case_to_spaces
from django.utils.translation import override, string_concat

PROXY_PARENTS = object()

EMPTY_RELATION_TREE = tuple()

IMMUTABLE_WARNING = (
    "The return type of '%s' should never be mutated. If you want to manipulate this list "
    "for your own use, make a copy first."
)

DEFAULT_NAMES = ('verbose_name', 'verbose_name_plural', 'db_table', 'ordering',
                 'unique_together', 'permissions', 'get_latest_by',
                 'order_with_respect_to', 'app_label', 'db_tablespace',
                 'abstract', 'managed', 'proxy', 'swappable', 'auto_created',
                 'index_together', 'apps', 'default_permissions',
                 'select_on_save', 'default_related_name',
                 'required_db_features', 'required_db_vendor')


class raise_deprecation(object):
    def __init__(self, suggested_alternative):
        self.suggested_alternative = suggested_alternative

    def __call__(self, fn):
        def wrapper(*args, **kwargs):
            warnings.warn(
                "'%s is an unofficial API that has been deprecated. "
                "You may be able to replace it with '%s'" % (
                    fn.__name__,
                    self.suggested_alternative,
                ),
                RemovedInDjango110Warning, stacklevel=2
            )
            return fn(*args, **kwargs)
        return wrapper


def normalize_together(option_together):
    """
    option_together can be either a tuple of tuples, or a single
    tuple of two strings. Normalize it to a tuple of tuples, so that
    calling code can uniformly expect that.
    """
    try:
        if not option_together:
            return ()
        if not isinstance(option_together, (tuple, list)):
            raise TypeError
        first_element = next(iter(option_together))
        if not isinstance(first_element, (tuple, list)):
            option_together = (option_together,)
        # Normalize everything to tuples
        return tuple(tuple(ot) for ot in option_together)
    except TypeError:
        # If the value of option_together isn't valid, return it
        # verbatim; this will be picked up by the check framework later.
        return option_together


def make_immutable_fields_list(name, data):
    return ImmutableList(data, warning=IMMUTABLE_WARNING % name)


@python_2_unicode_compatible
class Options(object):
    FORWARD_PROPERTIES = ('fields', 'many_to_many', 'concrete_fields',
                          'local_concrete_fields', '_forward_fields_map')
    REVERSE_PROPERTIES = ('related_objects', 'fields_map', '_relation_tree')

    def __init__(self, meta, app_label=None):
        self._get_fields_cache = {}
        self.proxied_children = []
        self.local_fields = []
        self.local_many_to_many = []
        self.virtual_fields = []
        self.model_name = None
        self.verbose_name = None
        self.verbose_name_plural = None
        self.db_table = ''
        self.ordering = []
        self._ordering_clash = False
        self.unique_together = []
        self.index_together = []
        self.select_on_save = False
        self.default_permissions = ('add', 'change', 'delete')
        self.permissions = []
        self.object_name = None
        self.app_label = app_label
        self.get_latest_by = None
        self.order_with_respect_to = None
        self.db_tablespace = settings.DEFAULT_TABLESPACE
        self.required_db_features = []
        self.required_db_vendor = None
        self.meta = meta
        self.pk = None
        self.has_auto_field = False
        self.auto_field = None
        self.abstract = False
        self.managed = True
        self.proxy = False
        # For any class that is a proxy (including automatically created
        # classes for deferred object loading), proxy_for_model tells us
        # which class this model is proxying. Note that proxy_for_model
        # can create a chain of proxy models. For non-proxy models, the
        # variable is always None.
        self.proxy_for_model = None
        # For any non-abstract class, the concrete class is the model
        # in the end of the proxy_for_model chain. In particular, for
        # concrete models, the concrete_model is always the class itself.
        self.concrete_model = None
        self.swappable = None
        self.parents = OrderedDict()
        self.auto_created = False

        # To handle various inheritance situations, we need to track where
        # managers came from (concrete or abstract base classes). `managers`
        # keeps a list of 3-tuples of the form:
        # (creation_counter, instance, abstract(=True))
        self.managers = []

        # List of all lookups defined in ForeignKey 'limit_choices_to' options
        # from *other* models. Needed for some admin checks. Internal use only.
        self.related_fkey_lookups = []

        # A custom app registry to use, if you're making a separate model set.
        self.apps = apps

        self.default_related_name = None

    @lru_cache(maxsize=None)
    def _map_model(self, link):
        # This helper function is used to allow backwards compatibility with
        # the previous API. No future methods should use this function.
        # It maps a field to (field, model or related_model,) depending on the
        # field type.
        model = link.model._meta.concrete_model
        if model is self.model:
            model = None
        return link, model

    @lru_cache(maxsize=None)
    def _map_model_details(self, link):
        # This helper function is used to allow backwards compatibility with
        # the previous API. No future methods should use this function.
        # This function maps a field to a tuple of:
        #  (field, model or related_model, direct, is_m2m) depending on the
        # field type.
        direct = not link.auto_created or link.concrete
        model = link.model._meta.concrete_model
        if model is self.model:
            model = None
        m2m = link.is_relation and link.many_to_many
        return link, model, direct, m2m

    @property
    def label(self):
        return '%s.%s' % (self.app_label, self.object_name)

    @property
    def label_lower(self):
        return '%s.%s' % (self.app_label, self.model_name)

    @property
    def app_config(self):
        # Don't go through get_app_config to avoid triggering imports.
        return self.apps.app_configs.get(self.app_label)

    @property
    def installed(self):
        return self.app_config is not None

    @property
    def abstract_managers(self):
        return [
            (counter, instance.name, instance) for counter, instance, abstract
            in self.managers if abstract
        ]

    @property
    def concrete_managers(self):
        return [
            (counter, instance.name, instance) for counter, instance, abstract
            in self.managers if not abstract
        ]

    def contribute_to_class(self, cls, name):
        from django.db import connection
        from django.db.backends.utils import truncate_name

        cls._meta = self
        self.model = cls
        # First, construct the default values for these options.
        self.object_name = cls.__name__
        self.model_name = self.object_name.lower()
        self.verbose_name = camel_case_to_spaces(self.object_name)

        # Store the original user-defined values for each option,
        # for use when serializing the model definition
        self.original_attrs = {}

        # Next, apply any overridden values from 'class Meta'.
        if self.meta:
            meta_attrs = self.meta.__dict__.copy()
            for name in self.meta.__dict__:
                # Ignore any private attributes that Django doesn't care about.
                # NOTE: We can't modify a dictionary's contents while looping
                # over it, so we loop over the *original* dictionary instead.
                if name.startswith('_'):
                    del meta_attrs[name]
            for attr_name in DEFAULT_NAMES:
                if attr_name in meta_attrs:
                    setattr(self, attr_name, meta_attrs.pop(attr_name))
                    self.original_attrs[attr_name] = getattr(self, attr_name)
                elif hasattr(self.meta, attr_name):
                    setattr(self, attr_name, getattr(self.meta, attr_name))
                    self.original_attrs[attr_name] = getattr(self, attr_name)

            self.unique_together = normalize_together(self.unique_together)
            self.index_together = normalize_together(self.index_together)

            # verbose_name_plural is a special case because it uses a 's'
            # by default.
            if self.verbose_name_plural is None:
                self.verbose_name_plural = string_concat(self.verbose_name, 's')

            # order_with_respect_and ordering are mutually exclusive.
            self._ordering_clash = bool(self.ordering and self.order_with_respect_to)

            # Any leftover attributes must be invalid.
            if meta_attrs != {}:
                raise TypeError("'class Meta' got invalid attribute(s): %s" % ','.join(meta_attrs.keys()))
        else:
            self.verbose_name_plural = string_concat(self.verbose_name, 's')
        del self.meta

        # If the db_table wasn't provided, use the app_label + model_name.
        if not self.db_table:
            self.db_table = "%s_%s" % (self.app_label, self.model_name)
            self.db_table = truncate_name(self.db_table, connection.ops.max_name_length())

    def _prepare(self, model):
        if self.order_with_respect_to:
            # The app registry will not be ready at this point, so we cannot
            # use get_field().
            query = self.order_with_respect_to
            try:
                self.order_with_respect_to = next(
                    f for f in self._get_fields(reverse=False)
                    if f.name == query or f.attname == query
                )
            except StopIteration:
                raise FieldDoesNotExist('%s has no field named %r' % (self.object_name, query))

            self.ordering = ('_order',)
            if not any(isinstance(field, OrderWrt) for field in model._meta.local_fields):
                model.add_to_class('_order', OrderWrt())
        else:
            self.order_with_respect_to = None

        if self.pk is None:
            if self.parents:
                # Promote the first parent link in lieu of adding yet another
                # field.
                field = next(six.itervalues(self.parents))
                # Look for a local field with the same name as the
                # first parent link. If a local field has already been
                # created, use it instead of promoting the parent
                already_created = [fld for fld in self.local_fields if fld.name == field.name]
                if already_created:
                    field = already_created[0]
                field.primary_key = True
                self.setup_pk(field)
            else:
                auto = AutoField(verbose_name='ID', primary_key=True,
                        auto_created=True)
                model.add_to_class('id', auto)

    def add_field(self, field, virtual=False):
        # Insert the given field in the order in which it was created, using
        # the "creation_counter" attribute of the field.
        # Move many-to-many related fields from self.fields into
        # self.many_to_many.
        if virtual:
            self.virtual_fields.append(field)
        elif field.is_relation and field.many_to_many:
            self.local_many_to_many.insert(bisect(self.local_many_to_many, field), field)
        else:
            self.local_fields.insert(bisect(self.local_fields, field), field)
            self.setup_pk(field)

        # If the field being added is a relation to another known field,
        # expire the cache on this field and the forward cache on the field
        # being referenced, because there will be new relationships in the
        # cache. Otherwise, expire the cache of references *to* this field.
        # The mechanism for getting at the related model is slightly odd -
        # ideally, we'd just ask for field.related_model. However, related_model
        # is a cached property, and all the models haven't been loaded yet, so
        # we need to make sure we don't cache a string reference.
        if field.is_relation and hasattr(field.remote_field, 'model') and field.remote_field.model:
            try:
                field.remote_field.model._meta._expire_cache(forward=False)
            except AttributeError:
                pass
            self._expire_cache()
        else:
            self._expire_cache(reverse=False)

    def setup_pk(self, field):
        if not self.pk and field.primary_key:
            self.pk = field
            field.serialize = False

    def setup_proxy(self, target):
        """
        Does the internal setup so that the current model is a proxy for
        "target".
        """
        self.pk = target._meta.pk
        self.proxy_for_model = target
        self.db_table = target._meta.db_table