function belongsToClass(element, className) {
	return !!element.className && new RegExp('\\b' +
		className.replace(/\-/, '\\-') + '\\b').test(element.className);
}

function show(node) {
	node.style.display = '';
}

function hide(node) {
	node.style.display = 'none';
}

function update(node, text) {
	node.appendChild(document.createTextNode(text));
}

function clear(node) {
	while (node.hasChildNodes()) {
		node.removeChild(node.firstChild);
	}
}

function $(id) { return document.getElementById(id); }

function show$(tagname, classname) {
	elements = document.getElementsByTagName(tagname);
	for (index in elements) {
		if (belongsToClass(elements[index], classname)) {
			show(elements[index]);
		}
	}
}

function hide$(tagname, classname) {
	elements = document.getElementsByTagName(tagname);
	for (index in elements) {
		if (belongsToClass(elements[index], classname)) {
			hide(elements[index]);
		}
	}
}

function update$(tagname, classname, text) {
	elements = document.getElementsByTagName(tagname);
	for (index in elements) {
		if (belongsToClass(elements[index], classname)) {
			update(elements[index], text);
		}
	}
}

function clear$(tagname, classname) {
	elements = document.getElementsByTagName(tagname);
	for (index in elements) {
		if (belongsToClass(elements[index], classname)) {
			clear(elements[index]);
		}
	}
}

function updateInstructions(data) {
	show$('div', 'div_instructions');
	clear$('span', 'message_text');
	clear$('span', 'shortcode');
	clear$('span', 'message_cost');
	update$('span', 'message_text', [data.prefix, SERVICE].join(' '));
	update$('span', 'shortcode', data.number);
	update$('span', 'message_cost', [data.price, data.currency,
		(parseInt(data.vat)? '(including VAT)': '(without VAT)')].join(' '));
	clear$('p', 'notes');
	if (data.special) {
		update$('p', 'notes', data.special);
		show$('p', 'notes');
	} else {
		hide$('p', 'notes');
	}
}

function selectProvider(i) {
	if (i == '-') {
		hide$('div', 'div_instructions');
		return;
	}
	updateInstructions(DATA.providers[i]);
}

function selectCountry(i) {
	if (i == '-') {
		hide$('div', 'div_provider');
		hide$('div', 'div_instructions');
		return;
	}
	if (JSONResponse[i].providers && JSONResponse[i].providers.length) {
		hide$('div', 'div_instructions');
		show$('div', 'div_provider');
		DATA = JSONResponse[i];
		clear$('select', 'select_provider');
		selects = document.getElementsByTagName('select');
		for (index in selects) {
			if (belongsToClass(selects[index], 'select_provider')) {
				var def = document.createElement('option');
					update(def, SELECT_PROVIDER);
				def.value = '-';
				selects[index].appendChild(def);
				for (var j = 0; j < DATA.providers.length; ++j) {
					var opt = document.createElement('option');
					update(opt, DATA.providers[j].name);
					opt.value = j;
					selects[index].appendChild(opt);
				}
				selects[index].onchange = function() {
					selectProvider(this.value);
				}
			}
		}
	}
	else {
		hide$('div', 'div_provider');
		updateInstructions(JSONResponse[i]);
	}
}

function JSONHandleResponse() {
	//document.body.style.backgroundImage = 'none';
	if (!window.JSONResponse) {
		show$('div', 'div_fail');
		return;
	}
	show$('div', 'div_ui');
	selects = document.getElementsByTagName('select');
	for (index in selects) {
		if (belongsToClass(selects[index], 'select_country')) {
			for (var i = 0; i < JSONResponse.length; ++i) {
				var opt = document.createElement('option');
				update(opt, JSONResponse[i].country_name);
				opt.value = i;
				selects[index].appendChild(opt);
			}
			selects[index].onchange = function() {
				selectCountry(this.value);
			}
		}
	}
}

function JSONSendRequest() {
	var head_node = document.getElementsByTagName('head').item(0);
	var js_node = document.createElement('script');
	js_node.src = window.JSON_URL;
	js_node.type = 'text/javascript';
	js_node.charset = 'utf-8';
	if (navigator.product == 'Gecko' || navigator.userAgent.indexOf('Opera') != -1) {
		js_node.onload = JSONHandleResponse;
	}
	else {
		js_node.onreadystatechange = function(evt) {
			evt? 1: evt = window.event;
			var rs = (evt.target || evt.srcElement).readyState;
			if (rs == 'loaded' || rs == 'complete') {
				JSONHandleResponse();
			}
		}
	}
	head_node.appendChild(js_node);
}

if (window.addEventListener) {
	window.addEventListener('load', JSONSendRequest, false);
}
else if (window.attachEvent) {
	window.attachEvent('onload', JSONSendRequest);
}