function count_buy_ads()
{
	var inputs_array = document.getElementsByTagName("input");
	var num_inputs = inputs_array.length;
	var checked_inputs = 0;
	for (var i = 0; i < num_inputs; i++)
	{
		if (inputs_array[i].name == "buy_ads[]" && inputs_array[i].checked)
		{
			checked_inputs++;
		}
	}

	return checked_inputs;
}

function rota()
{
	if (typeof(ban) != "undefined" && ban.length > 1)
	{
		if (indice ==  ban.length)
		{
			indice = 0;
		}

		if (document.images)
		{
			document.images.ad_image.src = ban[indice].src;
		}
		else
		{
			document.getElementById("ad_image").src = ban[indice].src;
		}

		indice++;
		setTimeout("rota()", 4000);
	}
}

function set_buy_form()
{
	var buy_form = document.getElementById("buy_ads_form");
	if (buy_form)
	{
		buy_form.onsubmit = function()
		{
			var num_buy_ads = document.getElementById("num_buy_ads").value;
			var num_elected_ads = count_buy_ads();
			var code_obj = document.getElementById("code");
			if (code_obj.value == "")
			{
				alert("Debe poner un código");
				return false;
			}
			else if (num_elected_ads > num_buy_ads)
			{
				alert("Sólo puede comprar " + num_buy_ads + " anuncios con cada código. Usted ha escogido " + num_elected_ads + ".");
				return false;
			}
			else if (num_elected_ads < num_buy_ads)
			{
				return confirm("Ha escogido " + num_elected_ads + " anuncios. Puede escoger hasta " + num_buy_ads + ".\n¿Quiere continuar?");
			}
		}
	}
}
	
function set_onload()
{
	set_buy_form();
	rota();
}

window.onload = set_onload;