"""Event Man(ager) database backend

Classes and functions used to manage events and attendants database.
"""

import pymongo
from bson.objectid import ObjectId


class EventManDB(object):
    """MongoDB connector."""
    db = None
    connection = None

    def __init__(self, url=None, dbName='eventman'):
        """Initialize the instance, connecting to the database.

        :param url: URL of the database
        :type url: str (or None to connect to localhost)
        """
        self._url = url
        self._dbName = dbName
        self.connect(url)

    def connect(self, url=None, dbName=None):
        """Connect to the database.

        :param url: URL of the database
        :type url: str (or None to connect to localhost)

        :return: the database we're connected to
        :rtype: :class:`~pymongo.database.Database`
        """
        if self.db is not None:
            return self.db
        if url:
            self._url = url
        if dbName:
            self._dbName = dbName
        self.connection = pymongo.MongoClient(self._url)
        self.db = self.connection[self._dbName]
        return self.db

    def get(self, collection, _id):
        """Get a single document with the specified `_id`.

        :param collection: search the document in this collection
        :type collection: str
        :param _id: unique ID of the document
        :type _id: str or :class:`~bson.objectid.ObjectId`

        :return: the document with the given `_id`
        :rtype: dict
        """
        if not isinstance(_id, ObjectId):
            _id = ObjectId(_id)
        results = self.query(collection, {'_id': _id})
        return results and results[0] or {}

    def query(self, collection, query=None):
        """Get multiple documents matching a query.

        :param collection: search for documents in this collection
        :type collection: str
        :param query: search for documents with those attributes
        :type query: dict or None

        :return: list of matching documents
        :rtype: list
        """
        db = self.connect()
        query = query or {}
        if'_id' in query and not isinstance(query['_id'], ObjectId):
            query['_id'] = ObjectId(query['_id'])
        results = list(db[collection].find(query))
        for result in results:
            result['_id'] = str(result['_id'])
        return results

    def add(self, collection, data):
        """Insert a new document.

        :param collection: insert the document in this collection
        :type collection: str
        :param data: the document to store
        :type data: dict

        :return: the document, as created in the database
        :rtype: dict
        """
        db = self.connect()
        _id = db[collection].insert(data)
        return self.get(collection, _id)

    def update(self, collection, _id, data):
        """Update an existing document.

        :param collection: update a document in this collection
        :type collection: str
        :param _id: unique ID of the document to be updatd
        :type _id: str or :class:`~bson.objectid.ObjectId`
        :param data: the updated information to store
        :type data: dict

        :return: the document, after the update
        :rtype: dict
        """
        db = self.connect()
        data = data or {}
        if '_id' in data:
            del data['_id']
        db[collection].update({'_id': ObjectId(_id)}, {'$set': data})
        return self.get(collection, _id)

    def delete(self, collection, _id_or_query=None, force=False):
        """Remove one or more documents from a collection.

        :param collection: search the documents in this collection
        :type collection: str
        :param _id_or_query: unique ID of the document or query to match multiple documents
        :type _id_or_query: str or :class:`~bson.objectid.ObjectId` or dict
        :param force: force the deletion of all documents, when `_id_or_query` is empty
        :type force: bool
        """
        if not _id_or_query and not force:
            return
        db = self.connect()
        if not isinstance(_id_or_query, (ObjectId, dict)):
            _id_or_query = ObjectId(_id_or_query)
        db[collection].remove(_id_or_query)