// TOUCH-EVENTS SINGLE-FINGER SWIPE-SENSING JAVASCRIPT
// Courtesy of PADILICIOUS.COM and MACOSXAUTOMATION.COM

// this script can be used with one or more page elements to perform actions based on them being swiped with a single finger

var triggerElementID = null; // this variable is used to identity the triggering element
var fingerCount = 0;
var startX = 0;
var startY = 0;
var curX = 0;
var curY = 0;
var deltaX = 0;
var deltaY = 0;
var horzDiff = 0;
var vertDiff = 0;
var minLength = 72; // the shortest distance the user may swipe
var swipeLength = 0;
var swipeAngle = null;
var swipeDirection = null;

// The 4 Touch Event Handlers

// NOTE: the touchStart handler should also receive the ID of the triggering element
// make sure its ID is passed in the event call placed in the element declaration, like:
// <div id="picture-frame" ontouchstart="touchStart(event,'picture-frame');"  ontouchend="touchEnd(event);" ontouchmove="touchMove(event);" ontouchcancel="touchCancel(event);">

function touchStart(event,passedName) {
	// disable the standard ability to select the touched object
	event.preventDefault();
	// get the total number of fingers touching the screen
	fingerCount = event.touches.length;
	// since we're looking for a swipe (single finger) and not a gesture (multiple fingers),
	// check that only one finger was used
	if ( fingerCount == 1 ) {
		// get the coordinates of the touch
		startX = event.touches[0].pageX;
		startY = event.touches[0].pageY;
		// store the triggering element ID
		triggerElementID = passedName;
	} else {
		// more than one finger touched so cancel
		touchCancel(event);
		return true;
	}
}

function touchMove(event) {
	event.preventDefault();
	if ( event.touches.length == 1 ) {
		curX = event.touches[0].pageX;
		curY = event.touches[0].pageY;
	} else {
		touchCancel(event);
	}
}

function touchEnd(event) {
	
	
	event.preventDefault();
	// check to see if more than one finger was used and that there is an ending coordinate
	if ( fingerCount == 1 && curX != 0 ) {
		// use the Distance Formula to determine the length of the swipe
		swipeLength = Math.round(Math.sqrt(Math.pow(curX - startX,2) + Math.pow(curY - startY,2)));
		// if the user swiped more than the minimum length, perform the appropriate action
		if ( swipeLength >= minLength ) {
			caluculateAngle();
			determineSwipeDirection();
			processingRoutine();
			touchCancel(event); // reset the variables
		} else {
			touchCancel(event);
		}	
	} else {
		touchCancel(event);
		return true;
	
	}
}

function touchCancel(event) {
	// reset the variables back to default values
	fingerCount = 0;
	startX = 0;
	startY = 0;
	curX = 0;
	curY = 0;
	deltaX = 0;
	deltaY = 0;
	horzDiff = 0;
	vertDiff = 0;
	swipeLength = 0;
	swipeAngle = null;
	swipeDirection = null;
	triggerElementID = null;
}

function caluculateAngle() {
	var X = startX-curX;
	var Y = curY-startY;
	var Z = Math.round(Math.sqrt(Math.pow(X,2)+Math.pow(Y,2))); //the distance - rounded - in pixels
	var r = Math.atan2(Y,X); //angle in radians (Cartesian system)
	swipeAngle = Math.round(r*180/Math.PI); //angle in degrees
	if ( swipeAngle < 0 ) { swipeAngle =  360 - Math.abs(swipeAngle); }
}

function determineSwipeDirection() {
	if ( (swipeAngle <= 45) && (swipeAngle >= 0) ) {
		swipeDirection = 'left';
	} else if ( (swipeAngle <= 360) && (swipeAngle >= 315) ) {
		swipeDirection = 'left';
	} else if ( (swipeAngle >= 135) && (swipeAngle <= 225) ) {
		swipeDirection = 'right';
	} else if ( (swipeAngle > 45) && (swipeAngle < 135) ) {
		swipeDirection = 'down';
	} else {
		swipeDirection = 'up';
	}
}


function processingRoutine() {
	
	
	switch(swipeDirection) {
	case 'left':
		switch(sPage) {
		case 'publications':
			// Left for publications
			doNextItem();
			break;
			
		case 'portfolio':
			navBgImage(1,'forward');
			break;
			
		}
		
		break;
		
	case 'right':
		switch(sPage) {
		case 'publications':
			// Right for publictions
			doPrevItem();
			break;
			
		case 'portfolio':
			navBgImage(1,'back');
			break;
		}
		
		break;
		
	case 'up':
		
		break;
		
	case 'down':
		
		break;
	
	}
	
}