from pymongo import MongoClient
import logging
import argparse


def open_connection(host, port):
    return MongoClient(host=host, port=port)


def merge(con1, con2, database_name='metrik'):
    database1 = con1[database_name]
    database2 = con2[database_name]
    collections = database1.collection_names()
    for collection_name in collections:
        collection1 = database1[collection_name]
        collection2 = database2[collection_name]
        for item in collection1.find():
            if collection2.find({'_id': item['_id']}) is None:
                collection2.save(item)
                collection1.delete_one({'_id': item['_id']})
            else:
                logging.warning('Not moving item {} as the same ID already'
                                ' exists in the `right` database.'.format(
                    item['_id']
                ))


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument('-h', '--host-1', dest='host1',
                        help='The `left` database to copy from')
    parser.add_argument('-g', '--host-2', dest='host2',
                        help='The `right` database to copy into')
    parser.add_argument('-p', '--port-1', default=27017, dest='port1', type=int,
                        help='The port number of the `left` database')
    parser.add_argument('-o', '--port-2', default=27017, dest='port2', type=int,
                        help='The port number of the `right` database')
    parser.add_argument('-d', '--database', default='metrik',
                        help='The database to merge from one host to the other')
    args = parser.parse_args()
    con1 = open_connection(args.host1, args.port1)
    con2 = open_connection(args.host2, args.port2)
    merge(con1, con2, args.database)


if __name__ == '__main__':
    main()