import operator
from functools import partial

import pymongo
from bson.dbref import DBRef

from mongoengine import signals
from mongoengine.common import _import_class
from mongoengine.errors import (ValidationError, InvalidDocumentError,
                                LookUpError)
from mongoengine.python_support import (PY3, UNICODE_KWARGS, txt_type,
                                        to_str_keys_recursive)

from .common import get_document, ALLOW_INHERITANCE
from .datastructures import BaseDict, BaseList
from .fields import ComplexBaseField

__all__ = ('BaseDocument', )


class BaseDocument(object):

    _dynamic = False
    _created = True
    _dynamic_lock = True
    _initialised = False

    def __init__(self, **values):
        signals.pre_init.send(self.__class__, document=self, values=values)

        self._data = {}

        # Assign default values to instance
        for key, field in self._fields.iteritems():
            if self._db_field_map.get(key, key) in values:
                continue
            value = getattr(self, key, None)
            setattr(self, key, value)

        # Set passed values after initialisation
        if self._dynamic:
            self._dynamic_fields = {}
            dynamic_data = {}
            for key, value in values.iteritems():
                if key in self._fields or key == '_id':
                    setattr(self, key, value)
                elif self._dynamic:
                    dynamic_data[key] = value
        else:
            for key, value in values.iteritems():
                key = self._reverse_db_field_map.get(key, key)
                setattr(self, key, value)

        # Set any get_fieldname_display methods
        self.__set_field_display()

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

        # Flag initialised
        self._initialised = True
        signals.post_init.send(self.__class__, document=self)

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

            field = None
            if not hasattr(self, name) and not name.startswith('_'):
                DynamicField = _import_class("DynamicField")
                field = DynamicField(db_field=name)
                field.name = name
                self._dynamic_fields[name] = field

            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)

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

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

    def __getstate__(self):
        removals = ("get_%s_display" % k
                    for k, v in self._fields.items() if v.choices)
        for k in removals:
            if hasattr(self, k):
                delattr(self, k)
        return self.__dict__

    def __setstate__(self, __dict__):
        self.__dict__ = __dict__
        self.__set_field_display()

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

    def __getitem__(self, name):
        """Dictionary-style field access, return a field's value if present.
        """
        try:
            if name in self._fields:
                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 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 = type(u)
        return repr_type('<%s: %s>' % (self.__class__.__name__, u))

    def __str__(self):
        if hasattr(self, '__unicode__'):
            if PY3:
                return self.__unicode__()
            else:
                return unicode(self).encode('utf-8')
        return txt_type('%s object' % self.__class__.__name__)

    def __eq__(self, other):
        if isinstance(other, self.__class__) and hasattr(other, 'id'):
            if self.id == other.id:
                return True
        return False

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

    def __hash__(self):
        if self.pk is None:
            # For new object
            return super(BaseDocument, self).__hash__()
        else:
            return hash(self.pk)

    def to_mongo(self):
        """Return data dictionary ready for use with MongoDB.
        """
        data = {}
        for field_name, field in self._fields.items():
            value = getattr(self, field_name, None)
            if value is not None:
                data[field.db_field] = field.to_mongo(value)
        # Only add _cls if allow_inheritance is not False
        if not (hasattr(self, '_meta') and
           self._meta.get('allow_inheritance', ALLOW_INHERITANCE) == False):
            data['_cls'] = self._class_name
        if '_id' in data and data['_id'] is None:
            del data['_id']

        if not self._dynamic:
            return data

        for name, field in self._dynamic_fields.items():
            data[name] = field.to_mongo(self._data.get(name, None))
        return data

    def validate(self):
        """Ensure that all fields' values are valid and that required fields
        are present.
        """
        # Get a list of tuples of field names and their current values
        fields = [(field, getattr(self, name))
                  for name, field in self._fields.items()]

        # Ensure that each field is matched to a valid value
        errors = {}
        for field, value in fields:
            if value is not None:
                try:
                    field._validate(value)
                except ValidationError, error:
                    errors[field.name] = error.errors or error
                except (ValueError, AttributeError, AssertionError), error:
                    errors[field.name] = error
            elif field.required:
                errors[field.name] = ValidationError('Field is required',
                                                     field_name=field.name)
        if errors:
            raise ValidationError('ValidationError', errors=errors)

    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

        is_list = False
        if not hasattr(value, 'items'):
            is_list = True
            value = dict([(k, v) for k, v in enumerate(value)])

        if not is_list and '_cls' in value:
            cls = get_document(value['_cls'])
            return cls(**value)

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

        if is_list:  # Convert back to a list
            data_items = sorted(data.items(), key=operator.itemgetter(0))
            value = [v for k, v in data_items]
        else:
            value = data

        # Convert lists / values so we can watch for any changes on them
        if (isinstance(value, (list, tuple)) and
            not isinstance(value, BaseList)):
            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):
        """Marks a key as explicitly changed by the user
        """
        if not key:
            return
        key = self._db_field_map.get(key, key)
        if (hasattr(self, '_changed_fields') and
            key not in self._changed_fields):
            self._changed_fields.append(key)

    def _get_changed_fields(self, key='', inspected=None):
        """Returns a list of all fields that have explicitly been changed.
        """
        EmbeddedDocument = _import_class("EmbeddedDocument")
        DynamicEmbeddedDocument = _import_class("DynamicEmbeddedDocument")
        _changed_fields = []
        _changed_fields += getattr(self, '_changed_fields', [])

        inspected = inspected or set()
        if hasattr(self, 'id'):
            if self.id in inspected:
                return _changed_fields
            inspected.add(self.id)

        field_list = self._fields.copy()
        if self._dynamic:
            field_list.update(self._dynamic_fields)

        for field_name in field_list:

            db_field_name = self._db_field_map.get(field_name, field_name)
            key = '%s.' % db_field_name
            field = self._data.get(field_name, None)
            if hasattr(field, 'id'):
                if field.id in inspected:
                    continue
                inspected.add(field.id)

            if (isinstance(field, (EmbeddedDocument, DynamicEmbeddedDocument))
               and db_field_name not in _changed_fields):
                 # Find all embedded fields that have been changed
                changed = field._get_changed_fields(key, inspected)
                _changed_fields += ["%s%s" % (key, k) for k in changed if k]
            elif (isinstance(field, (list, tuple, dict)) and
                    db_field_name not in _changed_fields):
                # Loop list / dict fields as they contain documents
                # Determine the iterator to use
                if not hasattr(field, 'items'):
                    iterator = enumerate(field)
                else:
                    iterator = field.iteritems()
                for index, value in iterator:
                    if not hasattr(value, '_get_changed_fields'):
                        continue
                    list_key = "%s%s." % (key, index)
                    changed = value._get_changed_fields(list_key, inspected)
                    _changed_fields += ["%s%s" % (list_key, k)
                                        for k in changed if k]
        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()
        set_data = {}
        unset_data = {}
        parts = []
        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, DBRef):
                        break
                    elif p.isdigit():
                        d = d[int(p)]
                    elif hasattr(d, 'get'):
                        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 set_data.items():
            if value or isinstance(value, bool):
                continue

            # If we've set a value that ain't the default value dont unset it.
            default = None
            if (self._dynamic and len(parts) and
                parts[0] in self._dynamic_fields):
                del(set_data[path])
                unset_data[path] = 1
                continue
            elif path in self._fields:
                default = self._fields[path].default
            else:  # Perform a full lookup for lists / embedded lookups
                d = self
                parts = path.split('.')
                db_field_name = parts.pop()
                for p in parts:
                    if 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:
                if callable(default):
                    default = default()
            if default != value:
                continue

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

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

    @classmethod
    def _from_son(cls, son):
        """Create an instance of a Document (subclass) from a PyMongo SON.
        """
        # get the class name from the document, falling back to the given
        # class if unavailable
        class_name = son.get('_cls', cls._class_name)
        data = dict(("%s" % key, value) for key, value in son.items())
        if not UNICODE_KWARGS:
            # python 2.6.4 and lower cannot handle unicode keys
            # passed to class constructor example: cls(**data)
            to_str_keys_recursive(data)

        if '_cls' in data:
            del data['_cls']

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

        changed_fields = []
        errors_dict = {}

        for field_name, field in cls._fields.items():
            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), e:
                    errors_dict[field_name] = e
            elif field.default:
                default = field.default
                if callable(default):
                    default = default()
                if isinstance(default, BaseDocument):
                    changed_fields.append(field_name)

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

        obj = cls(**data)
        obj._changed_fields = changed_fields
        obj._created = False
        return obj

    @classmethod
    def _build_index_spec(cls, spec):
        """Build a PyMongo index spec from a MongoEngine index spec.
        """
        if isinstance(spec, basestring):
            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',
                                          ALLOW_INHERITANCE) != False
        include_cls = allow_inheritance and not spec.get('sparse', False)

        for key in spec['fields']:
            # If inherited spec continue
            if isinstance(key, (list, tuple)):
                continue

            # ASCENDING from +,
            # DESCENDING from -
            # GEO2D from *
            direction = pymongo.ASCENDING
            if key.startswith("-"):
                direction = pymongo.DESCENDING
            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'
                fields = []
            else:
                fields = cls._lookup_field(parts)
                parts = [field if field == '_id' else field.db_field
                         for field in fields]
                key = '.'.join(parts)
            index_list.append((key, direction))

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

        spec['fields'] = index_list
        if spec.get('sparse', False) and len(spec['fields']) > 1:
            raise ValueError(
                'Sparse indexes can only have one field in them. '
                'See https://jira.mongodb.org/browse/SERVER-2193')

        return spec

    @classmethod
    def _unique_with_indexes(cls, namespace=""):
        """
        Find and set unique indexes
        """
        unique_indexes = []
        for field_name, field in cls._fields.items():
            # Generate a list of indexes needed by uniqueness constraints
            if field.unique:
                field.required = True
                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, basestring):
                        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
                    unique_fields += unique_with

                # Add the new index to the list
                index = [("%s%s" % (namespace, f), pymongo.ASCENDING)
                         for f in unique_fields]
                unique_indexes.append(index)

            # 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 _lookup_field(cls, parts):
        """Lookup a field based on its attribute and return a list containing
        the field's parents and the field.
        """
        if not isinstance(parts, (list, tuple)):
            parts = [parts]
        fields = []
        field = None

        for field_name in parts:
            # Handle ListField indexing:
            if field_name.isdigit():
                new_field = field.field
                fields.append(field_name)
                continue

            if field is None:
                # Look up first field from the document
                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:
                    DynamicField = _import_class('DynamicField')
                    field = DynamicField(db_field=field_name)
                else:
                    raise LookUpError('Cannot resolve field "%s"'
                                                % field_name)
            else:
                ReferenceField = _import_class('ReferenceField')
                GenericReferenceField = _import_class('GenericReferenceField')
                if isinstance(field, (ReferenceField, GenericReferenceField)):
                    raise LookUpError('Cannot perform join in mongoDB: %s' %
                                      '__'.join(parts))
                if hasattr(getattr(field, 'field', None), 'lookup_member'):
                    new_field = field.field.lookup_member(field_name)
                else:
                   # Look up subfield on the previous field
                    new_field = field.lookup_member(field_name)
                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)

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

        EmbeddedDocumentField = _import_class("EmbeddedDocumentField")
        GeoPointField = _import_class("GeoPointField")

        for field in cls._fields.values():
            if not isinstance(field, (EmbeddedDocumentField, GeoPointField)):
                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)
            elif field._geo_index:
                geo_indices.append(field)
        return geo_indices

    def __set_field_display(self):
        """Dynamically set the display value for a field with choices"""
        for attr_name, field in self._fields.items():
            if field.choices:
                setattr(self,
                        'get_%s_display' % attr_name,
                        partial(self.__get_field_display, field=field))

    def __get_field_display(self, field):
        """Returns the display value for a choice field"""
        value = getattr(self, field.name)
        if field.choices and isinstance(field.choices[0], (list, tuple)):
            return dict(field.choices).get(value, value)
        return value