/*

See LICENSE.txt for this sample’s licensing information.

Abstract:

This is the entry point to the application and handles the initial loading of required JavaScript files.

        This application uses custom attributes specified in the markup to define document URLs to be loaded on select / play event.

        These attributes are mapped to a corresponding controller class defined in this application, which are responsible for handling 

        the life-cycle and events of that document. 

        The following attributes are used in this application:

        - "documentURL" maps to DocumentController: this is the default controller that is used to fetch and push a document on the navigation stack.

        - "menuBarDocumentURL" maps to MenuBarController: the menuBarTemplate itself is pushed on navigation stack (hence subclasses from DocumentController),

                but this controller manages the document controllers associated with the menu items of the template.

        - "modalDocumentURL" maps to ModalController: This controller is similar to DocumentController but presents the 

                document as modal.

        - "searchDocumentURL" maps to SearchController: Handles the search template. This example demonstrates a default shelf

                , suggestions list and search results from iTunes store. The default results and suggestions are mocked.

        - "listDocumentURL" maps to ListController: Handles the list with segment and tumbler elements.

        - "slideshowImageURLs" maps to SlideshowController: Handles the presentation of slideshow of photos specified by the 

                attribute.

*/

/**

 * @description The onLaunch callback is invoked after the application JavaScript

 * has been parsed into a JavaScript context. The handler is passed an object

 * that contains options. These options are defined in the Swift or objective-c client code.

 * Options can be used to communicate data and state information to your JavaScript code.

 *

 * The location attribute is automatically added to the options object and represents

 * the URL that was used to retrieve the application JavaScript.

 */

App.onLaunch = function(options) {

    // Determine the base URL for remote server fetches from launch options, which will be used to resolve the URLs

    // in XML files for this app.

    const baseURL = options.baseURL;

    // Specify all the URLs for helper JavaScript files

    const helperScriptURLs = [

        "DocumentLoader",

        "DocumentController",

        "ListController",

        "MenuBarController",

        "ModalController",

        "SearchController",

        "SlideshowController"

    ].map(

        moduleName => `${baseURL}js/${moduleName}.js`

    );

    // Show a loading spinner while additional JavaScript files are being evaluated

    let loadingDocument = createLoadingDocument();

    if (typeof navigationDocument !== "undefined") {

        navigationDocument.pushDocument(loadingDocument);

    }

    // evaluateScripts is responsible for loading the JavaScript files neccessary

    // for this app to run. It can be used at any time in your apps lifecycle.

    evaluateScripts(helperScriptURLs, function(scriptsAreLoaded) {

        if (scriptsAreLoaded) {

            // Instantiate the DocumentLoader, which will be used to fetch and resolve URLs from the fecthed XML documents.

            // This instance is passed along to subsequent DocumentController objects.

            const documentLoader = new DocumentLoader(baseURL);

            const documentURL = documentLoader.prepareURL("/templates/Index.xml");

            // Instantiate the controller with root template. The controller is passed in the loading document which

            // was pushed while scripts were being evaluated, and controller will replace it with root template once

            // fetched from the server.

            new DocumentController({documentLoader, documentURL, loadingDocument});

        } else {

            // Handle error cases in your code. You should present a readable and user friendly

            // error message to the user in an alert dialog.

            const alertDocument = createEvalErrorAlertDocument();

            navigationDocument.replaceDocument(alertDocument, loadingDocument);

            throw new EvalError("TVMLCatalog application.js: unable to evaluate scripts.");

        }

    });

};

/**

 * Convenience function to create a TVML loading document with a specified title.

 */

function createLoadingDocument(title) {

    // If no title has been specified, fall back to "Loading...".

    title = title || "Loading...";

    const template = `<?xml version="1.0" encoding="UTF-8" ?>

        <document>

            <loadingTemplate>

                <activityIndicator>

                    <title>${title}</title>

                </activityIndicator>

            </loadingTemplate>

        </document>

    `;

    return new DOMParser().parseFromString(template, "application/xml");

}

/**

 * Convenience function to create a TVML alert document with a title and description.

 */

function createAlertDocument(title, description) {

    const template = `<?xml version="1.0" encoding="UTF-8" ?>

        <document>

            <alertTemplate>

                <title>${title}</title>

                <description>${description}</description>

            </alertTemplate>

        </document>

    `;

    return new DOMParser().parseFromString(template, "application/xml");

}

/**

 * Convenience function to create a TVML alert document with a title and description.

 */

function createDescriptiveAlertDocument(title, description) {

    const template = `<?xml version="1.0" encoding="UTF-8" ?>

        <document>

            <descriptiveAlertTemplate>

                <title>${title}</title>

                <description>${description}</description>

            </descriptiveAlertTemplate>

        </document>

    `;

    return new DOMParser().parseFromString(template, "application/xml");

}

/**

 * Convenience function to create a TVML alert for failed evaluateScripts.

 */

function createEvalErrorAlertDocument() {

    const title = "Evaluate Scripts Error";

    const description = [

        "There was an error attempting to evaluate the external JavaScript files.",

        "Please check your network connection and try again later."

    ].join("\n\n");

    return createAlertDocument(title, description);

}

/**

 * Convenience function to create a TVML alert for a failed XMLHttpRequest.

 */

function createLoadErrorAlertDocument(url, xhr) {

    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);

}