import copy
import numbers
from functools import partial

from bson import DBRef, ObjectId, SON, json_util
import pymongo
import six
from six import iteritems

from mongoengine import signals
from mongoengine.base.common import get_document
from mongoengine.base.datastructures import (BaseDict, BaseList,
                                             EmbeddedDocumentList,
                                             LazyReference,
                                             StrictDict)
from mongoengine.base.fields import ComplexBaseField
from mongoengine.common import _import_class
from mongoengine.errors import (FieldDoesNotExist, InvalidDocumentError,
                                LookUpError, OperationError, ValidationError)
from mongoengine.python_support import Hashable

__all__ = ('BaseDocument', 'NON_FIELD_ERRORS')

NON_FIELD_ERRORS = '__all__'


class BaseDocument(object):
    # TODO simplify how `_changed_fields` is used.
    # Currently, handling of `_changed_fields` seems unnecessarily convoluted:
    # 1. `BaseDocument` defines `_changed_fields` in its `__slots__`, yet it's
    #    not setting it to `[]` (or any other value) in `__init__`.
    # 2. `EmbeddedDocument` sets `_changed_fields` to `[]` it its overloaded
    #    `__init__`.
    # 3. `Document` does NOT set `_changed_fields` upon initialization. The
    #    field is primarily set via `_from_son` or `_clear_changed_fields`,
    #    though there are also other methods that manipulate it.
    # 4. The codebase is littered with `hasattr` calls for `_changed_fields`.
    __slots__ = ('_changed_fields', '_initialised', '_created', '_data',
                 '_dynamic_fields', '_auto_id_field', '_db_field_map',
                 '__weakref__')

    _dynamic = False
    _dynamic_lock = True
    STRICT = False

    def __init__(self, *args, **values):
        """
        Initialise a document or an embedded document.

        :param dict values: A dictionary of keys and values for the document.
            It may contain additional reserved keywords, e.g. "__auto_convert".
        :param bool __auto_convert: If True, supplied values will be converted
            to Python-type values via each field's `to_python` method.
        :param set __only_fields: A set of fields that have been loaded for
            this document. Empty if all fields have been loaded.
        :param bool _created: Indicates whether this is a brand new document
            or whether it's already been persisted before. Defaults to true.
        """
        self._initialised = False
        self._created = True

        if args:
            # Combine positional arguments with named arguments.
            # We only want named arguments.
            field = iter(self._fields_ordered)
            # If its an automatic id field then skip to the first defined field
            if getattr(self, '_auto_id_field', False):
                next(field)
            for value in args:
                name = next(field)
                if name in values:
                    raise TypeError(
                        'Multiple values for keyword argument "%s"' % name)
                values[name] = value

        __auto_convert = values.pop('__auto_convert', True)

        __only_fields = set(values.pop('__only_fields', values))

        _created = values.pop('_created', True)

        signals.pre_init.send(self.__class__, document=self, values=values)

        # Check if there are undefined fields supplied to the constructor,
        # if so raise an Exception.
        if not self._dynamic and (self._meta.get('strict', True) or _created):
            _undefined_fields = set(values.keys()) - set(
                list(self._fields.keys()) + ['id', 'pk', '_cls', '_text_score'])
            if _undefined_fields:
                msg = (
                    'The fields "{0}" do not exist on the document "{1}"'
                ).format(_undefined_fields, self._class_name)
                raise FieldDoesNotExist(msg)

        if self.STRICT and not self._dynamic:
            self._data = StrictDict.create(allowed_keys=self._fields_ordered)()
        else:
            self._data = {}

        self._dynamic_fields = SON()

        # Assign default values to the instance.
        # We set default values only for fields loaded from DB. See
        # https://github.com/mongoengine/mongoengine/issues/399 for more info.
        for key, field in iteritems(self._fields):
            if self._db_field_map.get(key, key) in __only_fields:
                continue
            value = getattr(self, key, None)
            setattr(self, key, value)

        if '_cls' not in values:
            self._cls = self._class_name

        # Set passed values after initialisation
        if self._dynamic:
            dynamic_data = {}
            for key, value in iteritems(values):
                if key in self._fields or key == '_id':
                    setattr(self, key, value)
                else:
                    dynamic_data[key] = value
        else:
            FileField = _import_class('FileField')
            for key, value in iteritems(values):
                key = self._reverse_db_field_map.get(key, key)
                if key in self._fields or key in ('id', 'pk', '_cls'):
                    if __auto_convert and value is not None:
                        field = self._fields.get(key)
                        if field and not isinstance(field, FileField):
                            value = field.to_python(value)
                    setattr(self, key, value)
                else:
                    self._data[key] = value

        # Set any get_<field>_display methods
        self.__set_field_display()

        if self._dynamic:
            self._dynamic_lock = False
            for key, value in iteritems(dynamic_data):
                setattr(self, key, value)

        # Flag initialised
        self._initialised = True
        self._created = _created

        signals.post_init.send(self.__class__, document=self)

    def __delattr__(self, *args, **kwargs):
        """Handle deletions of fields"""
        field_name = args[0]
        if field_name in self._fields:
            default = self._fields[field_name].default
            if callable(default):
                default = default()
            setattr(self, field_name, default)
        else:
            super(BaseDocument, self).__delattr__(*args, **kwargs)

    def __setattr__(self, name, value):
        # Handle dynamic data only if an initialised dynamic document
        if self._dynamic and not self._dynamic_lock:

            if not hasattr(self, name) and not name.startswith('_'):
                DynamicField = _import_class('DynamicField')
                field = DynamicField(db_field=name, null=True)
                field.name = name
                self._dynamic_fields[name] = field
                self._fields_ordered += (name,)

            if not name.startswith('_'):
                value = self.__expand_dynamic_values(name, value)

            # Handle marking data as changed
            if name in self._dynamic_fields:
                self._data[name] = value
                if hasattr(self, '_changed_fields'):
                    self._mark_as_changed(name)
        try:
            self__created = self._created
        except AttributeError:
            self__created = True

        if (
            self._is_document and
            not self__created and
            name in self._meta.get('shard_key', tuple()) and
            self._data.get(name) != value
        ):
            msg = 'Shard Keys are immutable. Tried to update %s' % name
            raise OperationError(msg)

        try:
            self__initialised = self._initialised
        except AttributeError:
            self__initialised = False
        # Check if the user has created a new instance of a class
        if (self._is_document and self__initialised and
                self__created and name == self._meta.get('id_field')):
            super(BaseDocument, self).__setattr__('_created', False)

        super(BaseDocument, self).__setattr__(name, value)

    def __getstate__(self):
        data = {}
        for k in ('_changed_fields', '_initialised', '_created',
                  '_dynamic_fields', '_fields_ordered'):
            if hasattr(self, k):
                data[k] = getattr(self, k)
        data['_data'] = self.to_mongo()
        return data

    def __setstate__(self, data):
        if isinstance(data['_data'], SON):
            data['_data'] = self.__class__._from_son(data['_data'])._data
        for k in ('_changed_fields', '_initialised', '_created', '_data',
                  '_dynamic_fields'):
            if k in data:
                setattr(self, k, data[k])
        if '_fields_ordered' in data:
            if self._dynamic:
                setattr(self, '_fields_ordered', data['_fields_ordered'])
            else:
                _super_fields_ordered = type(self)._fields_ordered
                setattr(self, '_fields_ordered', _super_fields_ordered)

        dynamic_fields = data.get('_dynamic_fields') or SON()
        for k in list(dynamic_fields.keys()):
            setattr(self, k, data['_data'].get(k))

    def __iter__(self):
        return iter(self._fields_ordered)

    def __getitem__(self, name):
        """Dictionary-style field access, return a field's value if present.
        """
        try:
            if name in self._fields_ordered:
                return getattr(self, name)
        except AttributeError:
            pass
        raise KeyError(name)

    def __setitem__(self, name, value):
        """Dictionary-style field access, set a field's value.
        """
        # Ensure that the field exists before settings its value
        if not self._dynamic and name not in self._fields:
            raise KeyError(name)
        return setattr(self, name, value)

    def __contains__(self, name):
        try:
            val = getattr(self, name)
            return val is not None
        except AttributeError:
            return False

    def __len__(self):
        return len(self._data)

    def __repr__(self):
        try:
            u = self.__str__()
        except (UnicodeEncodeError, UnicodeDecodeError):
            u = '[Bad Unicode data]'
        repr_type = str if u is None else type(u)
        return repr_type('<%s: %s>' % (self.__class__.__name__, u))

    def __str__(self):
        # TODO this could be simpler?
        if hasattr(self, '__unicode__'):
            if six.PY3:
                return self.__unicode__()
            else:
                return six.text_type(self).encode('utf-8')
        return six.text_type('%s object' % self.__class__.__name__)

    def __eq__(self, other):
        if isinstance(other, self.__class__) and hasattr(other, 'id') and other.id is not None:
            return self.id == other.id
        if isinstance(other, DBRef):
            return self._get_collection_name() == other.collection and self.id == other.id
        if self.id is None:
            return self is other
        return False

    def __ne__(self, other):
        return not self.__eq__(other)

    def clean(self):
        """
        Hook for doing document level data cleaning before validation is run.

        Any ValidationError raised by this method will not be associated with
        a particular field; it will have a special-case association with the
        field defined by NON_FIELD_ERRORS.
        """
        pass

    def get_text_score(self):
        """
        Get text score from text query
        """

        if '_text_score' not in self._data:
            raise InvalidDocumentError('This document is not originally built from a text query')

        return self._data['_text_score']

    def to_mongo(self, use_db_field=True, fields=None):
        """
        Return as SON data ready for use with MongoDB.
        """
        fields = fields or []

        data = SON()
        data['_id'] = None
        data['_cls'] = self._class_name

        # only root fields ['test1.a', 'test2'] => ['test1', 'test2']
        root_fields = {f.split('.')[0] for f in fields}

        for field_name in self:
            if root_fields and field_name not in root_fields:
                continue

            value = self._data.get(field_name, None)
            field = self._fields.get(field_name)

            if field is None and self._dynamic:
                field = self._dynamic_fields.get(field_name)

            if value is not None:
                f_inputs = field.to_mongo.__code__.co_varnames
                ex_vars = {}
                if fields and 'fields' in f_inputs:
                    key = '%s.' % field_name
                    embedded_fields = [
                        i.replace(key, '') for i in fields
                        if i.startswith(key)]

                    ex_vars['fields'] = embedded_fields

                if 'use_db_field' in f_inputs:
                    ex_vars['use_db_field'] = use_db_field

                value = field.to_mongo(value, **ex_vars)

            # Handle self generating fields
            if value is None and field._auto_gen:
                value = field.generate()
                self._data[field_name] = value

            if (value is not None) or (field.null):
                if use_db_field:
                    data[field.db_field] = value
                else:
                    data[field.name] = value

        # Only add _cls if allow_inheritance is True
        if not self._meta.get('allow_inheritance'):
            data.pop('_cls')

        return data

    def validate(self, clean=True):
        """Ensure that all fields' values are valid and that required fields
        are present.

        Raises :class:`ValidationError` if any of the fields' values are found
        to be invalid.
        """
        # Ensure that each field is matched to a valid value
        errors = {}
        if clean:
            try:
                self.clean()
            except ValidationError as error:
                errors[NON_FIELD_ERRORS] = error

        # Get a list of tuples of field names and their current values
        fields = [(self._fields.get(name, self._dynamic_fields.get(name)),
                   self._data.get(name)) for name in self._fields_ordered]

        EmbeddedDocumentField = _import_class('EmbeddedDocumentField')
        GenericEmbeddedDocumentField = _import_class(
            'GenericEmbeddedDocumentField')

        for field, value in fields:
            if value is not None:
                try:
                    if isinstance(field, (EmbeddedDocumentField,
                                          GenericEmbeddedDocumentField)):
                        field._validate(value, clean=clean)
                    else:
                        field._validate(value)
                except ValidationError as error:
                    errors[field.name] = error.errors or error
                except (ValueError, AttributeError, AssertionError) as error:
                    errors[field.name] = error
            elif field.required and not getattr(field, '_auto_gen', False):
                errors[field.name] = ValidationError('Field is required',
                                                     field_name=field.name)

        if errors:
            pk = 'None'
            if hasattr(self, 'pk'):
                pk = self.pk
            elif self._instance and hasattr(self._instance, 'pk'):
                pk = self._instance.pk
            message = 'ValidationError (%s:%s) ' % (self._class_name, pk)
            raise ValidationError(message, errors=errors)

    def to_json(self, *args, **kwargs):
        """Convert this document to JSON.

        :param use_db_field: Serialize field names as they appear in
            MongoDB (as opposed to attribute names on this document).
            Defaults to True.
        """
        use_db_field = kwargs.pop('use_db_field', True)
        return json_util.dumps(self.to_mongo(use_db_field), *args, **kwargs)

    @classmethod
    def from_json(cls, json_data, created=False):
        """Converts json data to a Document instance

        :param json_data: The json data to load into the Document
        :param created: If True, the document will be considered as a brand new document
                        If False and an id is provided, it will consider that the data being
                        loaded corresponds to what's already in the database (This has an impact of subsequent call to .save())
                        If False and no id is provided, it will consider the data as a new document
                        (default ``False``)
        """
        return cls._from_son(json_util.loads(json_data), created=created)

    def __expand_dynamic_values(self, name, value):
        """Expand any dynamic values to their correct types / values."""
        if not isinstance(value, (dict, list, tuple)):
            return value

        # If the value is a dict with '_cls' in it, turn it into a document
        is_dict = isinstance(value, dict)
        if is_dict and '_cls' in value:
            cls = get_document(value['_cls'])
            return cls(**value)

        if is_dict:
            value = {
                k: self.__expand_dynamic_values(k, v)
                for k, v in list(value.items())
            }
        else:
            value = [self.__expand_dynamic_values(name, v) for v in value]

        # Convert lists / values so we can watch for any changes on them
        EmbeddedDocumentListField = _import_class('EmbeddedDocumentListField')
        if (isinstance(value, (list, tuple)) and
                not isinstance(value, BaseList)):
            if issubclass(type(self), EmbeddedDocumentListField):
                value = EmbeddedDocumentList(value, self, name)
            else:
                value = BaseList(value, self, name)
        elif isinstance(value, dict) and not isinstance(value, BaseDict):
            value = BaseDict(value, self, name)

        return value

    def _mark_as_changed(self, key):
        """Mark a key as explicitly changed by the user."""
        if not key:
            return

        if not hasattr(self, '_changed_fields'):
            return

        if '.' in key:
            key, rest = key.split('.', 1)
            key = self._db_field_map.get(key, key)
            key = '%s.%s' % (key, rest)
        else:
            key = self._db_field_map.get(key, key)

        if key not in self._changed_fields:
            levels, idx = key.split('.'), 1
            while idx <= len(levels):
                if '.'.join(levels[:idx]) in self._changed_fields:
                    break
                idx += 1
            else:
                self._changed_fields.append(key)
                # remove lower level changed fields
                level = '.'.join(levels[:idx]) + '.'
                remove = self._changed_fields.remove
                for field in self._changed_fields[:]:
                    if field.startswith(level):
                        remove(field)

    def _clear_changed_fields(self):
        """Using _get_changed_fields iterate and remove any fields that
        are marked as changed.
        """
        for changed in self._get_changed_fields():
            parts = changed.split('.')
            data = self
            for part in parts:
                if isinstance(data, list):
                    try:
                        data = data[int(part)]
                    except IndexError:
                        data = None
                elif isinstance(data, dict):
                    data = data.get(part, None)
                else:
                    data = getattr(data, part, None)

                if not isinstance(data, LazyReference) and hasattr(data, '_changed_fields'):
                    if getattr(data, '_is_document', False):
                        continue

                    data._changed_fields = []

        self._changed_fields = []

    def _nestable_types_changed_fields(self, changed_fields, base_key, data):
        """Inspect nested data for changed fields

        :param changed_fields: Previously collected changed fields
        :param base_key: The base key that must be used to prepend changes to this data
        :param data: data to inspect for changes
        """
        # Loop list / dict fields as they contain documents
        # Determine the iterator to use
        if not hasattr(data, 'items'):
            iterator = enumerate(data)
        else:
            iterator = iteritems(data)

        for index_or_key, value in iterator:
            item_key = '%s%s.' % (base_key, index_or_key)
            # don't check anything lower if this key is already marked
            # as changed.
            if item_key[:-1] in changed_fields:
                continue

            if hasattr(value, '_get_changed_fields'):
                changed = value._get_changed_fields()
                changed_fields += ['%s%s' % (item_key, k) for k in changed if k]
            elif isinstance(value, (list, tuple, dict)):
                self._nestable_types_changed_fields(
                    changed_fields, item_key, value)

    def _get_changed_fields(self):
        """Return a list of all fields that have explicitly been changed.
        """
        EmbeddedDocument = _import_class('EmbeddedDocument')
        ReferenceField = _import_class('ReferenceField')
        GenericReferenceField = _import_class('GenericReferenceField')
        SortedListField = _import_class('SortedListField')

        changed_fields = []
        changed_fields += getattr(self, '_changed_fields', [])

        for field_name in self._fields_ordered:
            db_field_name = self._db_field_map.get(field_name, field_name)
            key = '%s.' % db_field_name
            data = self._data.get(field_name, None)
            field = self._fields.get(field_name)

            if db_field_name in changed_fields:
                # Whole field already marked as changed, no need to go further
                continue

            if isinstance(field, ReferenceField):   # Don't follow referenced documents
                continue

            if isinstance(data, EmbeddedDocument):
                # Find all embedded fields that have been changed
                changed = data._get_changed_fields()
                changed_fields += ['%s%s' % (key, k) for k in changed if k]
            elif isinstance(data, (list, tuple, dict)):
                if (hasattr(field, 'field') and
                        isinstance(field.field, (ReferenceField, GenericReferenceField))):
                    continue
                elif isinstance(field, SortedListField) and field._ordering:
                    # if ordering is affected whole list is changed
                    if any(field._ordering in d._changed_fields for d in data):
                        changed_fields.append(db_field_name)
                        continue

                self._nestable_types_changed_fields(
                    changed_fields, key, data)
        return changed_fields

    def _delta(self):
        """Returns the delta (set, unset) of the changes for a document.
        Gets any values that have been explicitly changed.
        """
        # Handles cases where not loaded from_son but has _id
        doc = self.to_mongo()

        set_fields = self._get_changed_fields()
        unset_data = {}
        if hasattr(self, '_changed_fields'):
            set_data = {}
            # Fetch each set item from its path
            for path in set_fields:
                parts = path.split('.')
                d = doc
                new_path = []
                for p in parts:
                    if isinstance(d, (ObjectId, DBRef)):
                        # Don't dig in the references
                        break
                    elif isinstance(d, list) and p.isdigit():
                        # An item of a list (identified by its index) is updated
                        d = d[int(p)]
                    elif hasattr(d, 'get'):
                        # dict-like (dict, embedded document)
                        d = d.get(p)
                    new_path.append(p)
                path = '.'.join(new_path)
                set_data[path] = d
        else:
            set_data = doc
            if '_id' in set_data:
                del set_data['_id']

        # Determine if any changed items were actually unset.
        for path, value in list(set_data.items()):
            if value or isinstance(value, (numbers.Number, bool)):  # Account for 0 and True that are truthy
                continue

            parts = path.split('.')

            if (self._dynamic and len(parts) and parts[0] in
                    self._dynamic_fields):
                del set_data[path]
                unset_data[path] = 1
                continue

            # If we've set a value that ain't the default value don't unset it.
            default = None
            if path in self._fields:
                default = self._fields[path].default
            else:  # Perform a full lookup for lists / embedded lookups
                d = self
                db_field_name = parts.pop()
                for p in parts:
                    if isinstance(d, list) and p.isdigit():
                        d = d[int(p)]
                    elif (hasattr(d, '__getattribute__') and
                          not isinstance(d, dict)):
                        real_path = d._reverse_db_field_map.get(p, p)
                        d = getattr(d, real_path)
                    else:
                        d = d.get(p)

                if hasattr(d, '_fields'):
                    field_name = d._reverse_db_field_map.get(db_field_name,
                                                             db_field_name)
                    if field_name in d._fields:
                        default = d._fields.get(field_name).default
                    else:
                        default = None

            if default is not None:
                default = default() if callable(default) else default

            if value != default:
                continue

            del set_data[path]
            unset_data[path] = 1
        return set_data, unset_data

    @classmethod
    def _get_collection_name(cls):
        """Return the collection name for this class. None for abstract
        class.
        """
        return cls._meta.get('collection', None)

    @classmethod
    def _from_son(cls, son, _auto_dereference=True, only_fields=None, created=False):
        """Create an instance of a Document (subclass) from a PyMongo SON."""
        if not only_fields:
            only_fields = []

        if son and not isinstance(son, dict):
            raise ValueError("The source SON object needs to be of type 'dict'")

        # Get the class name from the document, falling back to the given
        # class if unavailable
        class_name = son.get('_cls', cls._class_name)

        # Convert SON to a data dict, making sure each key is a string and
        # corresponds to the right db field.
        data = {}
        for key, value in iteritems(son):
            key = str(key)
            key = cls._db_field_map.get(key, key)
            data[key] = value

        # Return correct subclass for document type
        if class_name != cls._class_name:
            cls = get_document(class_name)

        errors_dict = {}

        fields = cls._fields
        if not _auto_dereference:
            fields = copy.deepcopy(fields)

        for field_name, field in iteritems(fields):
            field._auto_dereference = _auto_dereference
            if field.db_field in data:
                value = data[field.db_field]
                try:
                    data[field_name] = (value if value is None
                                        else field.to_python(value))
                    if field_name != field.db_field:
                        del data[field.db_field]
                except (AttributeError, ValueError) as e:
                    errors_dict[field_name] = e

        if errors_dict:
            errors = '\n'.join(['%s - %s' % (k, v)
                                for k, v in list(errors_dict.items())])
            msg = ('Invalid data to create a `%s` instance.\n%s'
                   % (cls._class_name, errors))
            raise InvalidDocumentError(msg)

        # In STRICT documents, remove any keys that aren't in cls._fields
        if cls.STRICT:
            data = {k: v for k, v in iteritems(data) if k in cls._fields}

        obj = cls(
            __auto_convert=False,
            _created=created,
            __only_fields=only_fields,
            **data
        )
        obj._changed_fields = []
        if not _auto_dereference:
            obj._fields = fields

        return obj

    @classmethod
    def _build_index_specs(cls, meta_indexes):
        """Generate and merge the full index specs."""
        geo_indices = cls._geo_indices()
        unique_indices = cls._unique_with_indexes()
        index_specs = [cls._build_index_spec(spec) for spec in meta_indexes]

        def merge_index_specs(index_specs, indices):
            """Helper method for merging index specs."""
            if not indices:
                return index_specs

            # Create a map of index fields to index spec. We're converting
            # the fields from a list to a tuple so that it's hashable.
            spec_fields = {
                tuple(index['fields']): index for index in index_specs
            }

            # For each new index, if there's an existing index with the same
            # fields list, update the existing spec with all data from the
            # new spec.
            for new_index in indices:
                candidate = spec_fields.get(tuple(new_index['fields']))
                if candidate is None:
                    index_specs.append(new_index)
                else:
                    candidate.update(new_index)

            return index_specs

        # Merge geo indexes and unique_with indexes into the meta index specs.
        index_specs = merge_index_specs(index_specs, geo_indices)
        index_specs = merge_index_specs(index_specs, unique_indices)
        return index_specs

    @classmethod
    def _build_index_spec(cls, spec):
        """Build a PyMongo index spec from a MongoEngine index spec."""
        if isinstance(spec, six.string_types):
            spec = {'fields': [spec]}
        elif isinstance(spec, (list, tuple)):
            spec = {'fields': list(spec)}
        elif isinstance(spec, dict):
            spec = dict(spec)

        index_list = []
        direction = None

        # Check to see if we need to include _cls
        allow_inheritance = cls._meta.get('allow_inheritance')
        include_cls = (
            allow_inheritance and
            not spec.get('sparse', False) and
            spec.get('cls', True) and
            '_cls' not in spec['fields']
        )

        # 733: don't include cls if index_cls is False unless there is an explicit cls with the index
        include_cls = include_cls and (spec.get('cls', False) or cls._meta.get('index_cls', True))
        if 'cls' in spec:
            spec.pop('cls')
        for key in spec['fields']:
            # If inherited spec continue
            if isinstance(key, (list, tuple)):
                continue

            # ASCENDING from +
            # DESCENDING from -
            # TEXT from $
            # HASHED from #
            # GEOSPHERE from (
            # GEOHAYSTACK from )
            # GEO2D from *
            direction = pymongo.ASCENDING
            if key.startswith('-'):
                direction = pymongo.DESCENDING
            elif key.startswith('$'):
                direction = pymongo.TEXT
            elif key.startswith('#'):
                direction = pymongo.HASHED
            elif key.startswith('('):
                direction = pymongo.GEOSPHERE
            elif key.startswith(')'):
                direction = pymongo.GEOHAYSTACK
            elif key.startswith('*'):
                direction = pymongo.GEO2D
            if key.startswith(('+', '-', '*', '$', '#', '(', ')')):
                key = key[1:]

            # Use real field name, do it manually because we need field
            # objects for the next part (list field checking)
            parts = key.split('.')
            if parts in (['pk'], ['id'], ['_id']):
                key = '_id'
            else:
                fields = cls._lookup_field(parts)
                parts = []
                for field in fields:
                    try:
                        if field != '_id':
                            field = field.db_field
                    except AttributeError:
                        pass
                    parts.append(field)
                key = '.'.join(parts)
            index_list.append((key, direction))

        # Don't add cls to a geo index
        if include_cls and direction not in (
                pymongo.GEO2D, pymongo.GEOHAYSTACK, pymongo.GEOSPHERE):
            index_list.insert(0, ('_cls', 1))

        if index_list:
            spec['fields'] = index_list

        return spec

    @classmethod
    def _unique_with_indexes(cls, namespace=''):
        """Find unique indexes in the document schema and return them."""
        unique_indexes = []
        for field_name, field in list(cls._fields.items()):
            sparse = field.sparse

            # Generate a list of indexes needed by uniqueness constraints
            if field.unique:
                unique_fields = [field.db_field]

                # Add any unique_with fields to the back of the index spec
                if field.unique_with:
                    if isinstance(field.unique_with, six.string_types):
                        field.unique_with = [field.unique_with]

                    # Convert unique_with field names to real field names
                    unique_with = []
                    for other_name in field.unique_with:
                        parts = other_name.split('.')

                        # Lookup real name
                        parts = cls._lookup_field(parts)
                        name_parts = [part.db_field for part in parts]
                        unique_with.append('.'.join(name_parts))

                        # Unique field should be required
                        parts[-1].required = True
                        sparse = (not sparse and
                                  parts[-1].name not in cls.__dict__)

                    unique_fields += unique_with

                # Add the new index to the list
                fields = [
                    ('%s%s' % (namespace, f), pymongo.ASCENDING)
                    for f in unique_fields
                ]
                index = {'fields': fields, 'unique': True, 'sparse': sparse}
                unique_indexes.append(index)

            if field.__class__.__name__ in {'EmbeddedDocumentListField',
                                            'ListField', 'SortedListField'}:
                field = field.field

            # Grab any embedded document field unique indexes
            if (field.__class__.__name__ == 'EmbeddedDocumentField' and
                    field.document_type != cls):
                field_namespace = '%s.' % field_name
                doc_cls = field.document_type
                unique_indexes += doc_cls._unique_with_indexes(field_namespace)

        return unique_indexes

    @classmethod
    def _geo_indices(cls, inspected=None, parent_field=None):
        inspected = inspected or []
        geo_indices = []
        inspected.append(cls)

        geo_field_type_names = ('EmbeddedDocumentField', 'GeoPointField',
                                'PointField', 'LineStringField',
                                'PolygonField')

        geo_field_types = tuple([_import_class(field)
                                 for field in geo_field_type_names])

        for field in list(cls._fields.values()):
            if not isinstance(field, geo_field_types):
                continue

            if hasattr(field, 'document_type'):
                field_cls = field.document_type
                if field_cls in inspected:
                    continue

                if hasattr(field_cls, '_geo_indices'):
                    geo_indices += field_cls._geo_indices(
                        inspected, parent_field=field.db_field)
            elif field._geo_index:
                field_name = field.db_field
                if parent_field:
                    field_name = '%s.%s' % (parent_field, field_name)
                geo_indices.append({
                    'fields': [(field_name, field._geo_index)]
                })

        return geo_indices

    @classmethod
    def _lookup_field(cls, parts):
        """Given the path to a given field, return a list containing
        the Field object associated with that field and all of its parent
        Field objects.

        Args:
            parts (str, list, or tuple) - path to the field. Should be a
            string for simple fields existing on this document or a list
            of strings for a field that exists deeper in embedded documents.

        Returns:
            A list of Field instances for fields that were found or
            strings for sub-fields that weren't.

        Example:
            >>> user._lookup_field('name')
            [<mongoengine.fields.StringField at 0x1119bff50>]

            >>> user._lookup_field('roles')
            [<mongoengine.fields.EmbeddedDocumentListField at 0x1119ec250>]

            >>> user._lookup_field(['roles', 'role'])
            [<mongoengine.fields.EmbeddedDocumentListField at 0x1119ec250>,
             <mongoengine.fields.StringField at 0x1119ec050>]

            >>> user._lookup_field('doesnt_exist')
            raises LookUpError

            >>> user._lookup_field(['roles', 'doesnt_exist'])
            [<mongoengine.fields.EmbeddedDocumentListField at 0x1119ec250>,
             'doesnt_exist']

        """
        # TODO this method is WAY too complicated. Simplify it.
        # TODO don't think returning a string for embedded non-existent fields is desired

        ListField = _import_class('ListField')
        DynamicField = _import_class('DynamicField')

        if not isinstance(parts, (list, tuple)):
            parts = [parts]

        fields = []
        field = None

        for field_name in parts:
            # Handle ListField indexing:
            if field_name.isdigit() and isinstance(field, ListField):
                fields.append(field_name)
                continue

            # Look up first field from the document
            if field is None:
                if field_name == 'pk':
                    # Deal with "primary key" alias
                    field_name = cls._meta['id_field']

                if field_name in cls._fields:
                    field = cls._fields[field_name]
                elif cls._dynamic:
                    field = DynamicField(db_field=field_name)
                elif cls._meta.get('allow_inheritance') or cls._meta.get('abstract', False):
                    # 744: in case the field is defined in a subclass
                    for subcls in cls.__subclasses__():
                        try:
                            field = subcls._lookup_field([field_name])[0]
                        except LookUpError:
                            continue

                        if field is not None:
                            break
                    else:
                        raise LookUpError('Cannot resolve field "%s"' % field_name)
                else:
                    raise LookUpError('Cannot resolve field "%s"' % field_name)
            else:
                ReferenceField = _import_class('ReferenceField')
                GenericReferenceField = _import_class('GenericReferenceField')

                # If previous field was a reference, throw an error (we
                # cannot look up fields that are on references).
                if isinstance(field, (ReferenceField, GenericReferenceField)):
                    raise LookUpError('Cannot perform join in mongoDB: %s' %
                                      '__'.join(parts))

                # If the parent field has a "field" attribute which has a
                # lookup_member method, call it to find the field
                # corresponding to this iteration.
                if hasattr(getattr(field, 'field', None), 'lookup_member'):
                    new_field = field.field.lookup_member(field_name)

                # If the parent field is a DynamicField or if it's part of
                # a DynamicDocument, mark current field as a DynamicField
                # with db_name equal to the field name.
                elif cls._dynamic and (isinstance(field, DynamicField) or
                                       getattr(getattr(field, 'document_type', None), '_dynamic', None)):
                    new_field = DynamicField(db_field=field_name)

                # Else, try to use the parent field's lookup_member method
                # to find the subfield.
                elif hasattr(field, 'lookup_member'):
                    new_field = field.lookup_member(field_name)

                # Raise a LookUpError if all the other conditions failed.
                else:
                    raise LookUpError(
                        'Cannot resolve subfield or operator {} '
                        'on the field {}'.format(field_name, field.name)
                    )

                # If current field still wasn't found and the parent field
                # is a ComplexBaseField, add the name current field name and
                # move on.
                if not new_field and isinstance(field, ComplexBaseField):
                    fields.append(field_name)
                    continue
                elif not new_field:
                    raise LookUpError('Cannot resolve field "%s"' % field_name)

                field = new_field  # update field to the new field type

            fields.append(field)

        return fields

    @classmethod
    def _translate_field_name(cls, field, sep='.'):
        """Translate a field attribute name to a database field name.
        """
        parts = field.split(sep)
        parts = [f.db_field for f in cls._lookup_field(parts)]
        return '.'.join(parts)

    def __set_field_display(self):
        """For each field that specifies choices, create a
        get_<field>_display method.
        """
        fields_with_choices = [(n, f) for n, f in list(self._fields.items())
                               if f.choices]
        for attr_name, field in fields_with_choices:
            setattr(self,
                    'get_%s_display' % attr_name,
                    partial(self.__get_field_display, field=field))

    def __get_field_display(self, field):
        """Return the display value for a choice field"""
        value = getattr(self, field.name)
        if field.choices and isinstance(field.choices[0], (list, tuple)):
            if value is None:
                return None
            sep = getattr(field, 'display_sep', ' ')
            values = value if field.__class__.__name__ in ('ListField', 'SortedListField') else [value]
            return sep.join([
                six.text_type(dict(field.choices).get(val, val))
                for val in values or []])
        return value
