from bson import ObjectId
from pymongo import Connection

from django.core.exceptions import ImproperlyConfigured
from django.core.urlresolvers import reverse
from django.conf import settings

from tastypie.bundle import Bundle
from tastypie.resources import Resource


db = Connection(
    host=getattr(settings, "MONGODB_HOST", None),
    port=getattr(settings, "MONGODB_PORT", None)
)[settings.MONGODB_DATABASE]


class Document(dict):
    # dictionary-like object for mongodb documents.
    __getattr__ = dict.get

class MongoDBResource(Resource):
    """
    A base resource that allows to make CRUD operations for mongodb.
    """
    def get_collection(self):
        """
        Encapsulates collection name.
        """
        try:
            return db[self._meta.collection]
        except AttributeError:
            raise ImproperlyConfigured("Define a collection in your resource.")

    def obj_get_list(self, request=None, **kwargs):
        """
        Maps mongodb documents to Document class.
        """
        return map(Document, self.get_collection().find())

    def obj_get(self, request=None, **kwargs):
        """
        Returns mongodb document from provided id.
        """
        return Document(self.get_collection().find_one({
            "_id": ObjectId(kwargs.get("pk"))
        }))

    def obj_create(self, bundle, **kwargs):
        """
        Creates mongodb document from POST data.
        """
        self.get_collection().insert(bundle.data)
        return bundle

    def obj_update(self, bundle, request=None, **kwargs):
        """
        Updates mongodb document.
        """
        self.get_collection().update({
            "_id": ObjectId(kwargs.get("pk"))
        }, {
            "$set": bundle.data
        })
        return bundle

    def obj_delete(self, request=None, **kwargs):
        """
        Removes single document from collection
        """
        self.get_collection().remove({ "_id": ObjectId(kwargs.get("pk")) })

    def obj_delete_list(self, request=None, **kwargs):
        """
        Removes all documents from collection
        """
        self.get_collection().remove()

    def get_resource_uri(self, item):
        """
        Returns resource URI for bundle or object.
        """
        if isinstance(item, Bundle):
            pk = item.obj._id
        else:
            pk = item._id
        return reverse("api_dispatch_detail", kwargs={
            "resource_name": self._meta.resource_name,
            "pk": pk
        })