function changeImage (aProductId, aOptionId, aValueId){
	var sizeSelect = document.getElementsByTagName('select')[1];
	if (aValueId == ''){
	
			sizeSelect.disabled = true;
	      	sizeSelect.length = 1;
	      	sizeSelect.options[0].innerHTML = "Primero selecciona un modelo";

	      	return;
	}
	
	new Ajax.Request('productOptionImage.php',
	  {
	    method:'get',
	    parameters: {productId: aProductId, optionId: aOptionId,valueId:aValueId},
	    onSuccess: function(transport){
	      var response = transport.responseXML;
	      
	      // changes image
	      var product = response.getElementsByTagName('product')[0];
	      var image = product.getElementsByTagName('image')[0].firstChild.data;
	      var newPath = image;
	      document.getElementById("productImage").src = newPath;
	      
	      // changes popup link
	      var bigImage = product.getElementsByTagName('bigImage')[0].firstChild.data;
	      var link = document.getElementById("productImageLink").href;
	      index = link.lastIndexOf("'");
	      var newLink = link.substr(0,index) + "&imagePath="+bigImage + "')";
	      document.getElementById("productImageLink").href = newLink;
	      //alert(newLink);
	      
	      // sets the message
	
	      if (product.getElementsByTagName('message')[0].firstChild != null){
	      	document.getElementById("imageMessage").innerHTML = product.getElementsByTagName('message')[0].firstChild.data;
	      }else {
	      	document.getElementById("imageMessage").innerHTML = "<br/>";	
	      }
	      
	      // gets the size group
	      var sizeGroup = product.getElementsByTagName('sizeGroup')[0].firstChild.data;
	      
	      
	      // sets the sizes      
	      if (sizeSelect.name == "id[2]"){
	      	sizeSelect.disabled = false;
	      	
	      	//alert(sizeSelect.options.length);
	      	sizeSelect.length = 1;
	
	      	sizeSelect.options[0].innerHTML = "Selecciona una talla";
	      	
	      	var sizes;
	      	var values;
	      	if (sizeGroup == 1){
	      		sizes = new Array("M","L","XL");
	      		values = new Array(25,26,27);
	      	}else if (sizeGroup == 2){
	      		sizes = new Array("M","L","XL");	
	      		values = new Array(28,29,62);
	      	}else if (sizeGroup == 3){
	      		sizes = new Array("S","U");	
	      		values = new Array(64,48);
	      	}else { // en cualquier otro caso muestra todos las tallas
	      		sizes = new Array("M","L","XL","S","U");		
	      	}
	      	
	      	
	      	for ( var i = 0; i < sizes.length; i++){
	       	  	var nuevaOpcion=document.createElement("option"); 
	      		nuevaOpcion.value= values [i]; 
	      		nuevaOpcion.innerHTML = sizes [i];
	      		sizeSelect.appendChild(nuevaOpcion);       		
	      	}
	
	      }
	      
	      
	    },
	    onFailure: function(){ alert('Something went wrong...') }
	  });
}

  function checkAddProductForm (aForm){
  	var modelSelect =  aForm.getElementsByTagName('select')[0];
  	var sizeSelect =  aForm.getElementsByTagName('select')[1];
  	
  	if (modelSelect.value == ""){
  		alert("Debes seleccionar un modelo");
  		return false;
  	}
  	
    if (sizeSelect.value == ""){
  		alert("Debes seleccionar una talla");
  		return false;
  	}
	
  	return true;
  
  }