/**
 * PeriodicalUpdater - jQuery plugin for timed, decaying ajax calls
 *
 * Smokejumper Version by Robert Fischer, Smokejumper IT
 * Based on version from http://www.360innovate.co.uk
 *
 * Copyright (c) 2009 by the following:
 *	 * Robert Fischer (http://smokejumperit.com)
 *	 * 360innovate (http://www.360innovate.co.uk)
 * Dual licensed under the MIT and GPL licenses:
 * http://www.opensource.org/licenses/mit-license.php
 * http://www.gnu.org/licenses/gpl.html
 *
 * Version: 2.0
 */

(function($) {
		function pu_log(msg) {
			try {
				console.log(msg);
			} catch(err) {}
		}

		// Now back to our regularly scheduled work
		$.PeriodicalUpdater = function(url, options, callback){

				var settings = jQuery.extend(true, {
					url: url,								// URL of ajax request
					cache: false,						// By default, don't allow caching
					method: 'GET',					// method; get or post
					data: '',								// array of values to be passed to the page - e.g. {name: "John", greeting: "hello"}
					minTimeout: 1000,				// starting value for the timeout in milliseconds
					maxTimeout: 8000,				// maximum length of time between requests
					multiplier: 2						// if set to 2, timerInterval will double each time the response hasn't changed (up to maxTimeout)
				}, options);
				
				// set some initial values, then begin
				var timerInterval = settings.minTimeout;

				// Function to boost the timer (nop unless multiplier > 1)
				var boostPeriod = function() { return; };
				if(settings.multiplier > 1) {
					boostPeriod = function() { 
						timerInterval = timerInterval * settings.multiplier;
						
						if(timerInterval > settings.maxTimeout) {
								timerInterval = settings.maxTimeout;
						}
					};
				} 

				// Construct the settings for $.ajax based on settings
				var ajaxSettings = jQuery.extend(true, {}, settings);
				if(settings.type && !ajaxSettings.dataType) ajaxSettings.dataType = settings.type;
				if(settings.sendData) ajaxSettings.data = settings.sendData;
				ajaxSettings.type = settings.method; // 'type' is used internally for jQuery.  Who knew?
				ajaxSettings.ifModified = true;

				// Create the function to get data
				// TODO It'd be nice to do the options.data check once (a la boostPeriod)
				function getdata() {
					var toSend = jQuery.extend(true, {}, ajaxSettings); // jQuery screws with what you pass in
					if(typeof(options.data) == 'function') {
						toSend.data = options.data();
						if(toSend.data) {
							// Handle transformations (only strings and objects are understood)
							if(typeof(toSend.data) == "number") {
								toSend.data = toSend.data.toString();
							}
						}
					}
					$.ajax(toSend); 
				}

				// Implement the tricky behind logic
				var remoteData = null;
				var prevData = null;
				
				ajaxSettings.success = function(data) {
					pu_log("Successful run! (In 'success')");
					remoteData = data;
					timerInterval = settings.minTimeout;
				};

				ajaxSettings.complete = function(xhr, success) {
					pu_log("Status of call: " + success + " (In 'complete')");
					if(success == "success" || success == "notmodified") {
						var rawData = $.trim(xhr.responseText);
						if(prevData == rawData) {
							boostPeriod();
						} else {
							timerInterval = settings.minTimeout;
							prevData = rawData;
							if(remoteData == null) remoteData = rawData;
							if(settings.success) { settings.success(remoteData); }
							if(callback) callback(remoteData);
						}
					}
					remoteData = null;
					setTimeout(getdata, timerInterval);
				}


				ajaxSettings.error = function (xhr, textStatus) { 
					pu_log("Error message: " + textStatus + " (In 'error')");
					if(textStatus == "notmodified") {
						boostPeriod();
					} else {
						prevData = null;
						timerInterval = settings.minTimeout;
					}
					if(settings.error) { settings.error(xhr, textStatus); }
				};

				// Make the first call
				$(function() { getdata(); });
		};	
})(jQuery);