import pymongo
from bson.son import SON
import datetime

DBHOST = '172.16.2.15'
DBNAME = 'iot'
DBCOLL = 'iot'
FILENAME = 'measurementData.xls'


client = pymongo.MongoClient(DBHOST)
db = client[DBNAME]
coll = db[DBCOLL]

startDate = datetime.datetime(2015, 8, 13)

cursor = coll.aggregate(
            [
                {"$match":{"metadata.device":"MeterbusHub", "metadata.name": {"$in": ["light", "laundry", "dishwasher"]}, "metadata.day": {"$gte": startDate}}},
                {"$sort":SON([("metadata.name",1),("metadata.day",1), ("metadata.seconds",1)])},
                {"$group":{"_id":{"device":"$metadata.name","day":"$metadata.day"}, "first":{"$first":"$data.energy"},"last":{"$last":"$data.energy"}}},
                {"$sort":{"_id":1}},
                {"$project": {"energy":{"$subtract":["$last","$first"]}}}
            ],
            useCursor=True
        )    

for c in cursor:
    print(c)