var current_image = 0;
var num_images = 0;

// onload function
function listingInit() {
	num_images = image_array.length;
	document.getElementById('listing-image-info').innerHTML = updateImageInfo();
}

function updateImageInfo() {	
	return 'Image ' + (current_image + 1) + ' of ' + num_images;
}

function imageChange(change_state) {
	var ajax_request = createAJAXobject();
	
	// Create a function that will receive data sent from the server
	ajax_request.onreadystatechange = function() {
		if (ajax_request.readyState == 4) {
			document.getElementById('listing-image').innerHTML = ajax_request.responseText;
			document.getElementById('listing-image-info').innerHTML = updateImageInfo();
		}
	}
	
	switch (change_state) {
		case 'prev':
			current_image--;
			if (current_image < 0) {
				current_image = num_images - 1;
			}
			break;
		case 'next':	
			current_image++;
			if (current_image >= num_images) {
				current_image = 0;
			}
			break;
	}
	
	var request_url = 'scripts/listing-image-gallery.php?image=' + image_array[current_image];
	ajax_request.open('GET', request_url, true);
	ajax_request.send(null);
}