'use strict';

function QueueSeeker(metadataBackend) {
    this.db = 5;
    this.channel = 'batch:hosts';
    this.redisPrefix = 'batch:queues:';
    this.pattern = this.redisPrefix + '*';
    this.metadataBackend = metadataBackend;
}

module.exports = QueueSeeker;

QueueSeeker.prototype.seek = function (onMessage, callback) {
    var initialCursor = ['0'];
    this.onMessage = onMessage;

    this._seek(initialCursor, callback);
};

QueueSeeker.prototype._seek = function (cursor, callback) {
    var self = this;
    var redisParams = [cursor[0], 'MATCH', self.pattern];

    self.metadataBackend.redisCmd(self.db, 'SCAN', redisParams, function (err, currentCursor) {
        if (err) {
            return callback(err);
        }

        // checks if iteration has ended
        if (currentCursor[0] === '0') {
            return callback(null);
        }

        var queues = currentCursor[1];

        if (!queues) {
            return callback(null);
        }

        queues.forEach(function (queue) {
            var host = queue.substr(self.redisPrefix.length);
            self.onMessage(self.channel, host);
        });

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