const { app, BrowserWindow, nativeTheme, Menu, MenuItem } = require('electron/main');
const path = require('node:path');
const fs = require('fs');
const os = require('os');
const log = require('electron-log/main');
const { linkExists } = require('link-exists');
const { setInterval } = require('node:timers/promises');

const isMac = process.platform === 'darwin';

//------------------------------------------------------------------------------
// Properties
//------------------------------------------------------------------------------

let config;
let win;
let menu;

//------------------------------------------------------------------------------
// Function
//------------------------------------------------------------------------------

/**
 * Loads a config file from disc.
 * The file is expected to be named `config.json` and is searched for in these
 * locations and in this order:
 * 
 * 1. `/assets/presentation/config.json` (Tooloop OS)
 * 2. Path of the executable  
 *    - Linux: `app.getPath('exe')`  
 *    - MacOS: `path.resolve(app.getPath('exe'), "../../../../")`  
 * 3. `__dirname` (Development)
 */
function loadConfig() {
    const locations = [
        '/assets/presentation',
        isMac ? path.resolve(app.getPath('exe'), "../../../../") : app.getPath('exe'),
        __dirname
    ];

    let filePath;

    // Check all locations
    for (const location of locations) {
        // Update the filepath
        filePath = path.join(location, 'config.json');
        try {
            // Try access
            fs.accessSync(filePath);

            // Parse the file if found
            console.info('Found config file at ' + filePath);
            const data = fs.readFileSync(filePath, { encoding: 'utf8' });
            config = JSON.parse(data);

            // Break the loop
            break;
        } catch (err) {
            console.warn('No config file found at ' + filePath);
        }
    }

}


/**
 * Creates the browser window
 */
function createWindow() {
    win = new BrowserWindow({
        width: 1920,
        height: 1080,
        backgroundColor: '#000000',
        icon: 'images/icon-512.png',
        autoHideMenuBar: true,
        webPreferences: {
            preload: path.join(__dirname, 'preload.js'),
            webSecurity: false,
            disableDialogs: true
        },
    });

    nativeTheme.themeSource = 'dark';

    // register event callbacks
    win.on("closed", function () { win = null; });
    win.webContents.on("will-frame-navigate", (event) => validateDomain(event));
    win.webContents.setWindowOpenHandler(({ url }) => {
        // we need to manually validate the url as `loadURL` 
        // doesn’t trigger the `will-navigate` event
        let event = new Event("DummyNavigation");
        event.url = url;
        if (validateDomain(event)) {
            win.loadURL(url);
        }
        return { action: 'deny' };
    });

    // show black window
    win.setKiosk(true);
    win.show();


    // Load page from config file
    if (config != undefined && 'url' in config) {
        loadUrlAsync(config.url);
    } else {
        try {
            // Load file from data folder if available
            fs.accessSync('/assets/data/index.html');
            win.loadFile('/assets/data/index.html');
        } catch {
            // Load fallback page
            win.loadFile('index.html');
        }
    }
}


/**
 * Creates all available keyboard shortcuts
 */
function createMenu() {
    menu = new Menu();

    menu.append(new MenuItem({
        label: app.name,
        submenu: [
            {
                label: 'Toggle Fullscreen',
                accelerator: isMac ? 'Cmd+F' : 'Ctrl+F',
                click: () => { win.setKiosk(!win.kiosk); }
            },
            { role: 'reload', },
            { role: 'quit', }
        ]
    }));

    Menu.setApplicationMenu(menu);
}


/**
 * Validates the url of a navigatio event against the list of allowed domains in
 * the config file. See https://www.electronjs.org/docs/latest/api/web-contents#event-will-frame-navigate
 * @param {Event} event 
 * @returns `true` if the url is allowed, `false` otherwise
 */
function validateDomain(event) {
    if (config == undefined) return true;

    let url = new URL(event.url);

    // allow local urls
    if (['file:', 'file'].includes(url.protocol)) return true;

    if ('allowedDomains' in config && !config.allowedDomains.includes(url.hostname)) {
        event.preventDefault();
        log.info("Navigation to " + event.url + " prevented");
        return false;
    }

    return true;
}

/**
 * Tests if the host of the url is reachable.
 * Access is tried in a 1 second interval and the url is loaded if successfull.
 * @param {string} testurl 
 */
async function loadUrlAsync(testurl) {
    try {
        let url = new URL(testurl);
        // If it’s an online url, test whether it’s reachable
        if (['https:', 'http:', 'https', 'http'].includes(url.protocol) &&
            !['127.0.0.1', 'localhost'].includes(url.host)) {
            reachable = await linkExists(url.href);
            if (reachable) {
                log.info("Successfull access to " + url.hostname);
                log.info("Loading " + config.url);
                win.loadURL(config.url);
            } else {
                log.warn("Could not reach " + url.hostname);

                for await (_ of setInterval(1000)) {
                    reachable = await linkExists(url.href);
                    if (reachable) {
                        log.info("Successfull access to " + url.hostname);
                        log.info("Loading " + config.url);
                        win.loadURL(config.url);
                        // break the interval
                        break;
                    } else {
                        log.warn("Could not reach " + url.hostname);
                    }
                }
            }

        }
        // Load other protocols (i. e. offline) immedately
        else {
            win.loadURL(config.url);
        }

    } catch (err) {
        log.error(err);
    }
}


//------------------------------------------------------------------------------
// Init electron app
//------------------------------------------------------------------------------

app.whenReady().then(() => {
    loadConfig();

    log.initialize();
    if (config != undefined && 'logPath' in config) {
        log.transports.file.resolvePathFn = () => config.logPath;
    }

    log.info('----------------------------------------------');
    log.info('Starting Tooloop Kiosk Browser...');

    createMenu();
    createWindow();
});

app.on('activate', () => {
    if (BrowserWindow.getAllWindows().length === 0) {
        createWindow();
    }
})

app.on('window-all-closed', () => {
    app.quit()
});

app.on('quit', () => {
    log.info('Quit');
});

// prevent error dialogs in case of exceptions
process.on('uncaughtException', function (error) {
    log.error(error);
});