var resourceLoader;

// app starting point
App.onLaunch = function(options) {
  // JS files included in our app (besides bootstrap)
  var javascriptFiles = [
    `${options.BASEURL}atv/js/ResourceLoader.js`, 
    `${options.BASEURL}atv/js/Presenter.js`,
  ];
 
  // see if scripts are broken; load menu if not, else display an error
  evaluateScripts(javascriptFiles, function(success) {
    if(success) {
      resourceLoader = new ResourceLoader(options.BASEURL);
      // load our main menu
      resourceLoader.fetch({
          url: `${options.BASEURL}atv/templates/MainMenu.xml`,
          success: function(document) {
            document.addEventListener('select', Presenter.load.bind(Presenter));
            Presenter.pushDocument(document);
          },
          error: function(xhr) {
            var errorDoc = createAlert("XML Parsing Error", `${options.BASEURL}appletv/templates/MainMenu.xml`);
            navigationDocument.presentModal(errorDoc);
          }
      });
      // resourceLoader.loadResource(`${options.BASEURL}appletv/templates/MainMenu.xml.js`, function(resource) {
      //   // create DOM from template information
      //   var doc = Presenter.makeDocument(resource);
      //   doc.addEventListener("select", Presenter.load.bind(Presenter));
      //   Presenter.pushDocument(doc);
      // });
    } else {
      var errorDoc = createAlert("Evaluate Scripts Error", "Error attempting to evaluate external JavaScript files.");
      navigationDocument.presentModal(errorDoc);
    }
  });
};
 
// simple function to create a templatized alert
var createAlert = function(title, description) {
  var alertString = `<?xml version="1.0" encoding="UTF-8" ?>
    <document>
      <alertTemplate>
        <title>${title}</title>
        <description>${description}</description>
        <button>
            <text>OK</text>
        </button>
      </alertTemplate>
    </document>`
    var parser = new DOMParser();
    var alertDoc = parser.parseFromString(alertString, "application/xml");

    return alertDoc;
};

/**
 * Convenience function to create a TVML alert document with a title and description.
 */
function createAlertDocument(title, description, isModal) {
    // Ensure the text color is appropriate if the alert isn't going to be shown modally.
    const textStyle = (isModal) ? "" : "color: rgb(0,0,0)";

    const template = `<?xml version="1.0" encoding="UTF-8" ?>
        <document>
            <alertTemplate>
                <title style="${textStyle}">${title}</title>
                <description style="${textStyle}">${description}</description>
            </alertTemplate>
        </document>
    `;
    return new DOMParser().parseFromString(template, "application/xml");
}

/**
 * Convenience function to create a TVML alert for a failed XMLHttpRequest.
 */
function createLoadErrorAlertDocument(url, xhr, isModal) {
    const title = (xhr.status) ? `Fetch Error ${xhr.status}` : "Fetch Error";
    const description = `Could not load document:\n${url}\n(${xhr.statusText})`;
    return createAlertDocument(title, description, isModal);
}