logic.js

const ObjectID = mongodb.ObjectID;

var cacheVk = {};

/**
 * @TODO: add token refresh logicб fallback ect
 */
export function vk (userId, db = null, f = null, collName = "users", tokPath = "vk.session.sid") {
    let project = {};
    project[tokPath] = 1;
    return f && f(db, userId, collName, tokPath) ||
        _.isObject(userId) && !db && P.promisify(vkontakte(_.get(userId, tokPath))) ||
        cacheVk[userId] && new  P.promisify(vkontakte(cacheVk[userId]))  ||
        db.collection(collName)
            .findOneAsync({_id: new ObjectID(userId)}, project)
            .then((res) => {
                let token = _.get(res, tokPath);
                if (typeof token === "string") {
                    cacheVk[userId] = token;
                }
                return P.promisify(vkontakte(token));
            })
}