"""Shortcode management.

A shortcode is an incremental number that's unique per project and per type.
Example types are 'task' and 'shot.
"""

import logging

from bson import ObjectId
from flask import current_app
import pymongo

log = logging.getLogger(__name__)


def generate_shortcode(project_id, node_type, prefix):
    """Generates and returns a new shortcode.

    :param project_id: project ID
    :type project_id: bson.ObjectId
    :param node_type: the type, for now 'attract_task' or 'attract_shot', but can be extended.
    :type node_type: unicode
    :param prefix: one-letter prefix for these shortcodes
    :type prefix: unicode
    """

    assert isinstance(project_id, ObjectId)

    db = current_app.db()
    db_fieldname = 'extension_props.attract.last_used_shortcodes.%s' % node_type

    log.debug('Incrementing project %s shortcode for type %r',
              project_id, node_type)

    new_proj = db['projects'].find_one_and_update(
        {'_id': project_id},
        {'$inc': {db_fieldname: 1}},
        {db_fieldname: 1},
        return_document=pymongo.ReturnDocument.AFTER,
    )

    shortcode = new_proj['extension_props']['attract']['last_used_shortcodes'][node_type]
    return '%s%i' % (prefix, shortcode)