var portion = 3;
var total = 0;
var position = 0;

var parent = '131';
var exclude = '';

jQuery(document).ready(function(){
	jQuery.ajax({
		type: "GET",
		url: "http://"+window.location.hostname+'/ajax/sections_navigation.php',
		data: {
			getTotal: 1,
			parent: parent,
			exclude: exclude
		}
	})
		.done(function( data ) {
			total = data;
			BuildStudies();
		}
	);
});

function CheckNavigation() {
	if (position == 0) {
		jQuery('.listblock .studies_navigation .prev').hide();
	}
	else {
		jQuery('.listblock .studies_navigation .prev').show();
	}

	if (position + portion >= total) {
		jQuery('.listblock .studies_navigation .next').hide();
	}
	else {
		jQuery('.listblock .studies_navigation .next').show();
	}
}

function BuildStudies() {
	CheckNavigation();
	var limit = portion;
	if (position + portion > total) {
		limit = total - position;
	}
	jQuery.ajax({
		type: "GET",
		url: "http://"+window.location.hostname+'/ajax/sections_navigation.php',
		data: {
			getStudies: 1,
			start: position,
			limit: limit,
			parent: parent,
			exclude: exclude
		}
	})
		.done(function( data ) {
			jQuery('.listblock .item').add('.listblock .sep').remove();
			jQuery('.listblock .hdr').after(data);
		}
	);
}

function SectionsNavigationNext() {
	if (position + portion < total ) {
		position += portion;
	}
	BuildStudies();
}

function SectionsNavigationPrev() {
	if (position >= portion ) {
		position -= portion;
	}
	BuildStudies();
}