window.addEvent('domready', function() {
	var previous = $('previous');
	var next = $('next');
	var mainImage = $('main_image');
	var imageNumber = mainImage.src;
	var num = '';

	// get the portfolio number from the original image, eg, "book1_image001.jpg" = "1"
	var portfolio = $('main_image').src;
	var pArray = portfolio.split('/');
	var pNum = pArray[pArray.length - 1];
	//total images specifies number of images in each book
	
	if (pArray[pArray.length - 1].split('')[4] == '1') {
		var pageNum = 1;
		var totalImages = '023';
	} else if (pArray[pArray.length - 1].split('')[4] == '2') {
		var pageNum = 2;
		var totalImages = '030';
	} else {
		var pageNum = 3;
		var totalImages = '026';
	}
	
	
	// get the number of the image, ie, "book1_image001.jpg" = "001.jpg"
	imageNumber = imageNumber.split('');
	for (var i = 7; i >= 1; i--) {
		num += imageNumber[imageNumber.length - i];
	}
	imageNumber = num;

	previous.addEvent('click', function() {
		if (parseInt(depad(imageNumber)) == '1') {
			imageNumber = totalImages;
		} else {
			imageNumber = parseInt(depad(imageNumber));
			imageNumber -= 1;
			imageNumber = pad(imageNumber, 3);
		}
		mainImage.src = 'images/book' + pageNum + '_image' + imageNumber + '.jpg';
	});

	/*previous.addEvent('mouseover', function() {
		previous.src = 'images/arrow_left_on.gif';
	});*/

	next.addEvent('click', function() {
		if (parseInt(depad(imageNumber)) == depad(totalImages)) {
			imageNumber = '001';
		} else {
			imageNumber = parseInt(depad(imageNumber));
			imageNumber += 1;
			imageNumber = pad(imageNumber, 3);
		}
		mainImage.src = 'images/book' + pageNum + '_image' + imageNumber + '.jpg';
	});
});

function pad(num, length) {
	var str = num + '';
	while (str.length < length) {
		str = '0' + str;
	}
	return str;
}

function depad(str) {
	str = str.split('');
	while (str[0] == '0') {
		str.splice(0, 1);
	}
	return str.join('');
}