$(function(){

	$('#tags_input')
	// don't navigate away from the field on tab when selecting an item
	.bind( "keydown", function( event ) {
		if ( event.keyCode === $.ui.keyCode.TAB &&
				$( this ).data( "autocomplete" ).menu.active ) {
			event.preventDefault();
		}
	});
	$('#tags_input').autocomplete({
		minLength: 0,
		source: function( request, response ) {
			// delegate back to autocomplete, but extract the last term
			response( $.ui.autocomplete.filter(
				availableTags, extractLast( request.term ) ) );
		},
		focus: function() {
			// prevent value inserted on focus
			return false;
		},
		select: function( event, ui ) {
			var terms = split( this.value );
			// remove the current input
			terms.pop();
			// add the selected item
			terms.push( ui.item.value );
			// add placeholder to get the comma-and-space at the end
			terms.push( "" );
			this.value = terms.join( ", " );
			return false;
		}
	});	
});
function split( val ) {
	return val.split( /,\s*/ );
}
function extractLast( term ) {
	return split( term ).pop();
}