function if_upload_img( element_id ) {
	hide_error('upload_error_file_1', 'upload_error_file_2');	
	hide_error('upload_error_url_1');
	hide_error('upload_error_flickr_1');
	clear_element('upload_message_file');	
	clear_element('upload_message_url');
	clear_element('upload_message_flickr');

	var element = document.getElementById( element_id );
	if( element && element.value.length == 0 ) {
		show_error( 'upload_error_file_1' );		
		return false;
	} else {
		if( ! check_format(element.value) ) {
			show_error( 'upload_error_file_2' );
			return false;
		}
		show_element( element_id );
		show_element( 'waiter_file' );
		setTimeout( 'document.getElementById("waiter_file_img").src = "http://www.retocafoto.com/img/design/uploading.gif"', 500 );
		var upload_form = document.getElementById( 'upload-form-file' );
		upload_form.submit();
		return true;
	}
}

function if_upload_flickr( element_id ) {
	hide_error('upload_error_url_1');
	hide_error('upload_error_file_1', 'upload_error_file_2');
	hide_error('upload_error_flickr_1');
	clear_element('upload_message_file');	        
	clear_element('upload_message_url');
	clear_element('upload_message_flickr');

	var flickr_tag = document.getElementById( 'upload_flickr_tag' );
	var flickr_user = document.getElementById( 'upload_flickr_username' );
	if( flickr_tag && flickr_tag.value.length == 0 && flickr_user && flickr_user.value.length == 0 ) { 
		show_error( 'upload_error_flickr_1' );
		return false;
	} else {
		show_element( 'do_upload_flickr' );
		show_element( 'upload_flickr_data' );
		if( document.getElementById('flickr-photos') ) { show_element( 'flickr-photos' ); }
		show_element( 'waiter_flickr' );
		setTimeout( 'document.getElementById("waiter_flickr_img").src = "http://www.retocafoto.com/img/design/uploading.gif"', 500 );
		return true;
	}
}

function if_upload_url( element_id ) {
	hide_error('upload_error_flickr_1');
	hide_error('upload_error_file_1', 'upload_error_file_2');
	hide_error('upload_error_url_1');
	clear_element('upload_message_file');	
	clear_element('upload_message_url');
	clear_element('upload_message_flickr');

	var element = document.getElementById( element_id );
	if( element && element.value.length == 0 ) {
		show_error( 'upload_error_url_1' );
		return false;
	} else {
		show_element( 'do_upload_url' );
		show_element( element_id );
		show_element( 'waiter_url' );
		setTimeout( 'document.getElementById("waiter_url_img").src = "http://www.retocafoto.com/img/design/uploading.gif"', 500 );
		return true;
	}
}

function check_format( str ) {
	if( str.match(/jpg/i) ){ return true; }
	if( str.match(/jpeg/i) ){ return true; }
	if( str.match(/gif/i) ){ return true; }
	if( str.match(/png/i) ){ return true; }
	return false;
}

function clear_input( element_id ) {
	var element = document.getElementById( element_id );
	if( element ){ element.value = ''; }
}

function clear_element( element_id ) {
	var element = document.getElementById( element_id );
	if( element ){ element.innerHTML = ''; }
}

function show_error ( element_id ) {
	var element = document.getElementById( element_id );
	if( element ) { element.style.display = "block"; }
}

function hide_error ( elements ) {
	var i = 0;
	while( i < hide_error.arguments.length ) {
		var element =  document.getElementById(hide_error.arguments[i]);
		if( element ){ 	element.style.display = "none";	}
		i++;
	}
}

function show_element ( element_id ) {
	var element = document.getElementById( element_id );
//	alert( "before: " + element_id + ' => ' + element.style.display );
	if( element.style.display == 'none' ) {
		element.style.display = 'block';
		element.style.visibility = 'visible';
	} else {
		element.style.display = 'none';
		element.style.visibility = 'hidden';
	}
//	alert( "after: " + element_id + ' => ' + element.style.display );
}

function switch_upload_menu_tabs( tab_id ) {
	var tabs = [
		{ tab_id: 'tab-file', zone_id: 'zone-file' },
		{ tab_id: 'tab-url', zone_id: 'zone-url' }
	];

<!-- ,{ tab_id: 'tab-flickr', zone_id: 'zone-flickr' } -->

	for(var i = 0; i < tabs.length; i++) {
		var tab = tabs[i];
		var tab_obj = document.getElementById( tab.tab_id );
		var zone_obj = document.getElementById( tab.zone_id );
		if( tab.tab_id == tab_id ) {
			if( tab_id == "tab-flickr" ) {
				if( document.getElementById('flickr_done').value == 1 ) {
					document.getElementById('zone-upload').style.height = "320px";
				}
			} else {
				document.getElementById('zone-upload').style.height = "120px";
			}
			tab_obj.className = "active";
			zone_obj.className = "display-block";
		} 
		else {
			tab_obj.className = "inactive";
			zone_obj.className = "display-none";
		}
	}
}

function pause(millis) 
{
        var date = new Date();
        var curDate = null;

        do { curDate = new Date(); } 
        while(curDate-date < millis)
} 

function check_email_form( sender, recip ) {
	var sender_obj = document.getElementById( sender );	
	var recip_obj = document.getElementById( recip );

	hide_error( 'email_form_error_1', 'email_form_error_2' );

	if( sender_obj && ! sender_obj.value ) {
		show_error( 'email_form_error_1' );	
		return false;
	}
	if( recip_obj && ! recip_obj.value ) {
		show_error( 'email_form_error_2' );
		return false;
	}

	return true;
}

function show_feedback_desc( obj ) {
        if( obj.value == 'delete' ) {
        	show_error( 'feedback-desc' );
        } else {
		hide_error( 'feedback-desc' );
    	}
}