/****************************************************************************************************************
 * CLASS geoLocation: helper-class for fetching geolocation (among others latitude, longitude)                  *
 *                    implemented as singleton-object                                                           *
 *                                                                                                              *
 *           methods: init(void):void --> initialize object and start fetching position                         *
 *                    startWatcher(void):void --> starts intervalled position-watching (ran by init)            *
 *                    getPosFromServer(void):void --> fetch GPS-position from server (actually one fixed point) *
 *                    distance(Object{lat:Number ,lon:Number} [,Object{lat:Number ,lon:Number}]):Number         *
 *                      └-> distance between two positions (or given and current one, if second one missing)    *
 *                                                                                                              *
 *            events: body.geoLocationError:Object{                                                             *
 *                                             error:Object{                                                    *
 *                                               number:Number,                                                 *
 *                                               message:String                                                 *
 *                                             },                                                               *
 *                                             position:Object{                                                 *
 *                                               latitude:Number,                                               *
 *                                               longitude:Number,                                              *
 *                                               accuracy:Number,                                               *
 *                                               timestamp:Number                                               *
 *                                             }                                                                *
 *                                           }                                                                  *
 *                    body.geoLocationGot:Object{                                                               *
 *                                             position:Object{                                                 *
 *                                               latitude:Number,                                               *
 *                                               longitude:Number,                                              *
 *                                               accuracy:Number,                                               *
 *                                               timestamp:Number                                               *
 *                                             }                                                                *
 *                                           }                                                                  *
 ****************************************************************************************************************/


var geoLocation = {						// implement as singleton
	latitude: null,
	longitude: null,
	accuracy: null,
	timestamp: null,
	_pwatcher: null,
	_ptimer: null,
	_disableWatcherAt: 50,
	
	_config: {
		enableHighAccuracy: true,
		maximumAge: 10000,				// 10 sec max cache lifetime (if geoposition cached)
		timeout: 60000					// 60 sec timeout
	},
	
	// event listeners
	_geoReady: function(position) {
		console.debug('geolocation api present - activate watcher');
		
//		this.startWatcher();
//		this._gotLocation(position);
	},
	
	_geoError: function(error) {
		console.debug('gelocation api not present or error');
		this._handle_error(error);
	},

	_gotLocation: function(position) {
		this.latitude = position.coords.latitude;
		this.longitude = position.coords.longitude;
		this.accuracy = position.coords.accuracy;
		this.timestamp = position.timestamp;
		
		if (this.accuracy <= this._disableWatcherAt)		// disable with timeout, if accurate location found
		{
			console.debug('disable watcher for 60 seconds', this._pwatcher);
			if (this._pwatcher !== null)
			{
				console.debug('watcher cleared');
				navigator.geolocation.clearWatch(this._pwatcher);
				this._pwatcher = null;
			}
			
			that = this;
			this._ptimer = setTimeout(function() {that.startWatcher.apply(that, arguments);}, 60000);
		}
		
		console.debug('got Position: ' + this.latitude + ', ' + this.longitude + '(' + this.accuracy + 'm < ' + this._disableWatcherAt + ': ' + (this.accuracy <= this._disableWatcherAt) + ')');
		$('body').trigger('geoLocationGot', {'position':{latitude: this.latitude, longitude: this.longitude, accuracy: this.accuracy, timestamp: this.timestamp}});
	},
	
	_handle_error: function(error) {
		console.debug(error);
		switch(error.code)
		{
		case error.PERMISSION_DENIED:
		if (_pwatcher != 'null') navigator.geolocation.clearWatch(_pwatcher);
		_pwatcher = 'null';
		
		break;
		
		case error.POSITION_UNAVAILABLE:
		break;
		
		case error.TIMEOUT:
		break;
		
		default:
		break;
		}
		
		$('body').trigger('geoLocationError',{'error':error,'position':{latitude: this.latitude, longitude: this.longitude, accuracy: this.accuracy, timestamp: this.timestamp}});
	},

	init: function() {
		var that = this;
		if (navigator.geolocation) {
			console.debug('test geolocation api');
			navigator.geolocation.getCurrentPosition(
				function() {that._geoReady.apply(that, arguments);},
				function() {that._geoError.apply(that, arguments);},
				this._config
			);
		}
	},
	
	startWatcher: function() {
		console.debug('waiting for location');
		that = this;
		if (this._pwatcher !== null) navigator.geolocation.clearWatch(this._pwatcher);

		clearTimeout(this._ptimer);
		
		this._pwatcher = navigator.geolocation.watchPosition(
			function() {that._gotLocation.apply(that, arguments);},
			function() {that._handle_error.apply(that, arguments);},
			this._config
		);
		console.debug('watcher started',this._pwatcher);
	},
	
	getPosFromServer: function() {
		console.debug('get position from server');
		that = this;
		$.getJSON('shippos.php', function(data) {
			console.debug('got server response: ',data);
			that._gotLocation.call(that, data);
		});
	},
	
	//haversine formula for distance between two positions in m (see http://www.movable-type.co.uk/scripts/latlong.html)
	distance:function(c1,c2)
	{
		PI180=Math.PI / 180;
		if(!c1) return false;
		if(!c2){ c2={'latitude':this.latitude, 'longitude':this.longitude}; }

		var dLat = (c2.latitude-c1.latitude) * PI180;		// delta in rad
		var dLon = (c2.longitude-c1.longitude) * PI180;
		var lat1 = c1.latitude * PI180;
		var lat2 = c2.latitude * PI180;

		var a = Math.sin(dLat/2) * Math.sin(dLat/2) + Math.sin(dLon/2) * Math.sin(dLon/2) * Math.cos(lat1) * Math.cos(lat2);
		var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));

		return (6371000 * c);			// earth-radius in m * 1000
	}
};	// geoLocation



$(document).ready(function() {
	$('body').on('geoLocationGot', function(e) {
		$('#no-gps').slideUp({duration: 500});
	});

	$('body').on('geoLocationError',function(e) {
		$('#no-gps').slideDown({duration: 500});
	});

	geoLocation.init();
});