/**
 *
 * Copyright 2013 Joel Grenon
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
var Q = require('q'),
    redis = require('redis'),
    _ = require('lodash'),
    async = require('async'),
    moment = require('moment');

require('underscore-query');

module.exports = function(request) {
    var _this = this;
    this.log.trace(request, "Handling subscribe command");
    var defer = Q.defer();
    Q.nextTick(function() {
        _this.log.debug("Subscribing agent %s to event %s", request.id, request.event);

        // Look for an existing subscription for this agent
        var subscription = _.query.build( _this.eventSubscriptions ).and({"agentId":request.id}).first();
        if(!subscription) {
            subscription = new EventSubscription(_this, request.id);
            _this.eventSubscriptions.push(subscription);
        }

        // Add a local handler to propagate these events to this subscription
        if(! _.contains(subscription.events, request.event)) {
            _this.on(request.event, subscription.listener(request));
            subscription.events.push(request.event);
            _this.log.debug("Subscription to event %s was successfully established for agent %s", request.event, request.id);
        }
        else
            _this.log.warn("Subscription to event %s is already in place. It will be reused", request.event);

        defer.resolve({success:true});
    });

    return defer.promise;
};

/**
 * Abstract an agent subscription for various custom events. Each event will be broadcast to the agent
 * as they are received by the dispatcher through the standard emit method.
 *
 * @param dispatcher
 * @param spec
 * @constructor
 */
var EventSubscription = function(dispatcher, agentId) {
    this.events = [];
    this.agentId = agentId;

    this.listener = function(s) {
        return function(e) {
            // Append this event to our event list
            dispatcher.emitTo(s.id, s.event, e);
        };
    };

};