'use strict';

var QUEUE = require('../job_queue').QUEUE;

function QueueSeeker(pool) {
    this.pool = pool;
}

module.exports = QueueSeeker;

QueueSeeker.prototype.seek = function (callback) {
    var initialCursor = ['0'];
    var users = {};
    var self = this;

    this.pool.acquire(QUEUE.DB, function(err, client) {
        if (err) {
            return callback(err);
        }
        self._seek(client, initialCursor, users, function(err, users) {
            self.pool.release(QUEUE.DB, client);
            return callback(err, Object.keys(users));
        });
    });
};

QueueSeeker.prototype._seek = function (client, cursor, users, callback) {
    var self = this;
    var redisParams = [cursor[0], 'MATCH', QUEUE.PREFIX + '*'];

    client.scan(redisParams, function(err, currentCursor) {
        if (err) {
            return callback(null, users);
        }

        var queues = currentCursor[1];
        if (queues) {
            queues.forEach(function (queue) {
                var user = queue.substr(QUEUE.PREFIX.length);
                users[user] = true;
            });
        }

        var hasMore = currentCursor[0] !== '0';
        if (!hasMore) {
            return callback(null, users);
        }

        self._seek(client, currentCursor, users, callback);
    });
};