from base import (DocumentMetaclass, TopLevelDocumentMetaclass, BaseDocument,
                  ValidationError)
from queryset import OperationError
from connection import _get_db

import pymongo


__all__ = ['Document', 'EmbeddedDocument', 'ValidationError', 'OperationError']


class EmbeddedDocument(BaseDocument):
    """A :class:`~mongoengine.Document` that isn't stored in its own
    collection.  :class:`~mongoengine.EmbeddedDocument`\ s should be used as
    fields on :class:`~mongoengine.Document`\ s through the
    :class:`~mongoengine.EmbeddedDocumentField` field type.
    """
    
    __metaclass__ = DocumentMetaclass


class Document(BaseDocument):
    """The base class used for defining the structure and properties of
    collections of documents stored in MongoDB. Inherit from this class, and
    add fields as class attributes to define a document's structure.
    Individual documents may then be created by making instances of the
    :class:`~mongoengine.Document` subclass.

    By default, the MongoDB collection used to store documents created using a
    :class:`~mongoengine.Document` subclass will be the name of the subclass
    converted to lowercase. A different collection may be specified by
    providing :attr:`collection` to the :attr:`meta` dictionary in the class
    definition.

    A :class:`~mongoengine.Document` subclass may be itself subclassed, to
    create a specialised version of the document that will be stored in the
    same collection. To facilitate this behaviour, `_cls` and `_types`
    fields are added to documents (hidden though the MongoEngine interface
    though). To disable this behaviour and remove the dependence on the
    presence of `_cls` and `_types`, set :attr:`allow_inheritance` to
    ``False`` in the :attr:`meta` dictionary.

    A :class:`~mongoengine.Document` may use a **Capped Collection** by 
    specifying :attr:`max_documents` and :attr:`max_size` in the :attr:`meta`
    dictionary. :attr:`max_documents` is the maximum number of documents that
    is allowed to be stored in the collection, and :attr:`max_size` is the 
    maximum size of the collection in bytes. If :attr:`max_size` is not 
    specified and :attr:`max_documents` is, :attr:`max_size` defaults to 
    10000000 bytes (10MB).

    Indexes may be created by specifying :attr:`indexes` in the :attr:`meta`
    dictionary. The value should be a list of field names or tuples of field 
    names. Index direction may be specified by prefixing the field names with
    a **+** or **-** sign.
    """

    __metaclass__ = TopLevelDocumentMetaclass

    def save(self, safe=True, force_insert=False):
        """Save the :class:`~mongoengine.Document` to the database. If the
        document already exists, it will be updated, otherwise it will be
        created.

        If ``safe=True`` and the operation is unsuccessful, an 
        :class:`~mongoengine.OperationError` will be raised.

        :param safe: check if the operation succeeded before returning
        :param force_insert: only try to create a new document, don't allow 
            updates of existing documents
        """
        self.validate()
        doc = self.to_mongo()
        try:
            collection = self.__class__.objects._collection
            if force_insert:
                object_id = collection.insert(doc, safe=safe)
            else:
                object_id = collection.save(doc, safe=safe)
        except pymongo.errors.OperationFailure, err:
            message = 'Could not save document (%s)'
            if 'duplicate key' in str(err):
                message = 'Tried to save duplicate unique keys (%s)'
            raise OperationError(message % str(err))
        id_field = self._meta['id_field']
        self[id_field] = self._fields[id_field].to_python(object_id)

    def delete(self, safe=False):
        """Delete the :class:`~mongoengine.Document` from the database. This
        will only take effect if the document has been previously saved.

        :param safe: check if the operation succeeded before returning
        """
        id_field = self._meta['id_field']
        object_id = self._fields[id_field].to_mongo(self[id_field])
        try:
            self.__class__.objects(**{id_field: object_id}).delete(safe=safe)
        except pymongo.errors.OperationFailure, err:
            raise OperationError('Could not delete document (%s)' % str(err))

    def reload(self):
        """Reloads all attributes from the database.

        .. versionadded:: 0.1.2
        """
        id_field = self._meta['id_field']
        obj = self.__class__.objects(**{id_field: self[id_field]}).first()
        for field in self._fields:
            setattr(self, field, obj[field])

    @classmethod
    def drop_collection(cls):
        """Drops the entire collection associated with this
        :class:`~mongoengine.Document` type from the database.
        """
        db = _get_db()
        db.drop_collection(cls._meta['collection'])


class MapReduceDocument(object):
    """A document returned from a map/reduce query.
    
    :param collection: An instance of :class:`~pymongo.Collection`
    :param key: Document/result key, often an instance of 
                :class:`~pymongo.objectid.ObjectId`. If supplied as 
                an ``ObjectId`` found in the given ``collection``, 
                the object can be accessed via the ``key_object`` property.
    :param value: The result(s) for this key. If given as a dictionary,
                  each key in the dictionary will be available as
                  an instance attribute.
    
    .. versionadded:: 0.2.2
 
    """
    
    def __init__(self, collection, key, value):
        self._collection = collection
        self.key = key
        self.value = value
        
        if isinstance(value, dict):
            # create attributes for each named result
            for k, v in value.iteritems():
                setattr(self, k, v)
    
    @property
    def object(self):
        """Lazy-load the object referenced by ``self.key``. If ``self.key``
        is not an ``ObjectId``, simply return ``self.key``.
        """
        if not isinstance(self.key, pymongo.objectid.ObjectId):
            return self.key
        if not hasattr(self, "_key_object"):
            self._key_object = self._collection.find_one(self.key)
            return self._key_object
        return self._key_object