itunes script to rename selected tracks' artist, title, and number using an arbitrary shell command given the track name through stdin

ack_tracks_js.scpt

var app = Application.currentApplication();
var itunes = new Application('iTunes');
var selection;

app.includeStandardAdditions = true;
itunes.includeStandardAdditions = true;

var artistNameDialog = {
  text: "function for artist name?    echo \"$track_name\" | $this_command",
  default: "/usr/local/bin/ack '^(\\d+) (.*) *- *(.*)$' --output '$2'"
};
var trackNameDialog = {
  text: "function for track name?    echo \"$track_name\" | $this_command",
  default: "/usr/local/bin/ack '^(\\d+) (.*) *- *(.*)$' --output '$3'"
};
var trackNumberDialog = {
  text: "function for track number?    echo \"$track_name\" | $this_command",
  default: "/usr/local/bin/ack '^(\\d+) (.*) *- *(.*)$' --output '$1'"
};

var functionForArtistName  = app.displayDialog(artistNameDialog.text,  { defaultAnswer: artistNameDialog.default }).textReturned;
var functionForTrackName   = app.displayDialog(trackNameDialog.text,   { defaultAnswer: trackNameDialog.default }).textReturned;
var functionForTrackNumber = app.displayDialog(trackNumberDialog.text, { defaultAnswer: trackNumberDialog.default }).textReturned;

selection = itunes.selection();

var wrappedDoShellScript = function(app, fnString, input, onFailureReturn) {
  try {
    return app.doShellScript("echo \"" + input + "\" | " + fnString);
  } catch(e) {
    return onFailureReturn;
  }
}

if (selection.length > 0) {
  for (var i in selection) {
    var track = selection[i];
    var trackName = track.name();

    track.name        = wrappedDoShellScript(app, functionForTrackName, trackName, trackName);
    track.artist      = wrappedDoShellScript(app, functionForArtistName, trackName, track.artist());
    track.trackNumber = wrappedDoShellScript(app, functionForTrackNumber, trackName, track.trackNumber());
  };
}