var cur_advice = 0;
var ttl_advices = 0;

function hide_advice(num) {
	var obj = gebi(num+'_advice');
	if (obj == undefined) return;
	obj.style.display = 'none';
}

function show_advice(num) {
	var obj = gebi(num+'_advice');
	if (obj == undefined) return;
	obj.style.display = 'block';
}

function hide_advices(cnt) {
	for (k = 1;k <= cnt;k++) hide_advice(k);
}

function init_advices(cnt) {
	ttl_advices = cnt;
	hide_advices(cnt);
}

function prev_advice() {
	var new_advice = cur_advice-1;
	if (new_advice < 1) new_advice = ttl_advices;
	switch_advice(new_advice);
}

function next_advice() {
	var new_advice = cur_advice+1;
	if (new_advice > ttl_advices) new_advice = 1;
	switch_advice(new_advice);
}

function switch_advice(num) {
	if (cur_advice != 0) 
		if (num == cur_advice) return;
		else hide_advice(cur_advice);
	
	if (num != 0) show_advice(num);
	cur_advice = num;
}