Obtain filename of referenced graphic

I am trying to create a script that I can run individually on referenced graphics which would return me information on what file it is, and which document it is located in.

So far I have this script

var graphic = null;

var doc = app.ActiveDoc;

if(doc.ObjectValid() == true)

{

       graphic = doc.FirstSelectedGraphicInDoc;

       if(graphic.constructor.name != "Inset")

        {

            graphic = null;

            alert("inset not found");

        }

}

if(graphic != null && graphic.ObjectValid() == true)

{

    var promptMessage = "The currently-selected graphic is:\n\n" +

       graphic.Name +"\n\n" + doc.Name;

        alert(promptMessage);

    }

else

{

    alert("No active document or no referenced graphic selected. " +

        "Cannot continue.");

}

alert("script complete!");

Right now when I have a graphic selected it produces the alert which correctly tells me what document the file is in but says "undefined" in the space I expect to see the image filename.

What is the correct way to obtain this information?