const { app, BrowserWindow, nativeTheme, Menu, MenuItem, ipcMain } = require('electron/main');
const path = require('node:path');
const { fileURLToPath } = require('node:url');
const fs = require('fs');
const log = require('electron-log/main');
const { default: isReachable } = require('is-reachable');
const { setTimeout: delay } = require('node:timers/promises');
const config = require('./js/config.js');
const { Config } = require('./js/config.js');
const { isAuthorizedWatchdogEvent: isWatchdogEventAuthorized, registerWatchdogHandler } = require('./js/watchdog.js');


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

let win;
let menu;
let navigationController;
let navigationRequest = 0;
let restartScheduled = false;
let rendererRecoveryScheduled = false;
let restartTimer;

const restartArgument = '--tooloop-restart-count=';
const restartCount = Number(
    process.argv.find(argument => argument.startsWith(restartArgument))?.slice(restartArgument.length) || 0
);
const maxAutomaticRestarts = 3;

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


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

/**
 * Creates the browser window
 */
function createMainWindow() {
    win = new BrowserWindow({
        width: 1920,
        height: 1080,
        backgroundColor: '#000000',
        icon: 'images/icon-512.png',
        autoHideMenuBar: true,
        kiosk: true,
        alwaysOnTop: true,
        webPreferences: {
            preload: path.join(__dirname, 'js/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(config.data.url);
        }
        return { action: 'deny' };
    });
    win.webContents.on("did-fail-load", (event, errorCode, errorDescription, validatedURL, isMainFrame) => {
        log.error(`Failed to load URL: ${validatedURL} with error: ${errorDescription}`);
        if (errorCode !== -3 && config.data?.url) {
            loadOfflinePage();
        }
    });
    win.webContents.on("render-process-gone", (_event, details) => {
        rendererRecoveryScheduled = false;
        log.error('Renderer process gone: ' + JSON.stringify(details));
        loadOfflinePage();
    });
    win.webContents.on("unresponsive", () => {
        log.error('Renderer became unresponsive');
        if (rendererRecoveryScheduled || win.isDestroyed()) return;

        rendererRecoveryScheduled = true;
        try {
            win.webContents.forcefullyCrashRenderer();
        } catch (error) {
            rendererRecoveryScheduled = false;
            log.error('Could not restart renderer: ' + (error?.stack || error));
            loadOfflinePage();
        }
    });
    win.webContents.on("responsive", () => {
        rendererRecoveryScheduled = false;
        log.info('Renderer became responsive');
    });
    win.on("page-title-updated", (event) => event.preventDefault());

    // Load page from config file
    if (config.data && 'url' in config.data && config.data.url) {
        loadUrlAsync(config.data.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('./html/onboarding.html');
        }
    }
}

function loadOfflinePage() {
    log.warn('Loading offline page');
    if (win && !win.isDestroyed()) {
        win.loadFile(path.join(__dirname, 'html/offline.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' },
            {
                label: 'Config',
                accelerator: isMac ? 'Cmd+,' : 'Ctrl+,',
                click: () => {
                    config.showWindow(
                        win,
                        (newConfig) => { loadUrlAsync(newConfig.url); }
                    );
                }
            }
        ]
    }));

    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 (isUrlAllowed(event.url)) return true;
    event.preventDefault();
    log.info("Navigation to " + event.url + " prevented");
    return false;
}

function isUrlAllowed(urlString) {
    if (config == undefined || config.data == undefined) return true;

    let url;
    try {
        url = new URL(urlString);
    } catch {
        return false;
    }

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

    if ('whitelist' in config.data &&
        Array.isArray(config.data.whitelist) &&
        config.data.whitelist.length > 0 &&
        !config.data.whitelist.includes(url.hostname)) {
        return false;
    }

    return true;
}

function isAuthorizedWatchdogEvent(event) {
    return isWatchdogEventAuthorized(event, win, isUrlAllowed);
}

function logWatchdogError(error) {
    log.warn('Watchdog reset failed: ' + (error?.message || error));
}

function registerWatchdogBridge() {
    registerWatchdogHandler(ipcMain, {
        isAuthorized: isAuthorizedWatchdogEvent,
        onError: logWatchdogError
    });
}

/**
 * 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) {
    const request = ++navigationRequest;
    navigationController?.abort();
    navigationController = new AbortController();
    const { signal } = navigationController;

    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)) {
            let fallbackShown = false;

            while (!signal.aborted && request === navigationRequest) {
                const timeoutSignal = AbortSignal.timeout(3000);
                const reachable = await isReachable(url.href, {
                    signal: AbortSignal.any([signal, timeoutSignal])
                });

                if (signal.aborted || request !== navigationRequest) return;

                if (reachable) {
                    log.info("Successful access to " + url.hostname);
                    log.info("Loading " + testurl);
                    if (!win.isDestroyed()) win.loadURL(testurl);
                    return;
                }

                log.warn("Could not reach " + url.hostname);
                if (!fallbackShown && !win.isDestroyed()) {
                    loadOfflinePage();
                    fallbackShown = true;
                }
                await delay(1000, undefined, { signal });
            }

        }
        // Load local files and other protocols immediately
        else if (url.protocol === 'file:') {
            if (!signal.aborted && request === navigationRequest && !win.isDestroyed()) {
                await win.loadFile(fileURLToPath(url), {
                    search: url.search,
                    hash: url.hash
                });
            }
        }
        else {
            if (!signal.aborted && request === navigationRequest && !win.isDestroyed()) {
                win.loadURL(testurl);
            }
        }

    } catch (err) {
        if (signal.aborted || request !== navigationRequest) return;
        log.error(err.message);
        // Load fallback page
        loadOfflinePage();
    }
}

function resolveLogPath() {
    if (config.data != undefined && 'logPath' in config.data) {
        if (fs.existsSync(config.data.logPath)) {
            return config.data.logPath;
        } else {
            return "tooloop-kiosk-browser.log";
        }
    }
}


function restartAfterFatalError(error) {
    log.error('Fatal main-process error: ' + (error?.stack || error));
    if (restartScheduled) return;
    restartScheduled = true;

    if (restartCount >= maxAutomaticRestarts) {
        log.error('Automatic restart limit reached; exiting');
        app.exit(1);
        return;
    }

    const relaunchArgs = process.argv.slice(1)
        .filter(argument => !argument.startsWith(restartArgument));
    relaunchArgs.push(restartArgument + (restartCount + 1));
    log.warn('Restarting application in 5 seconds (attempt ' + (restartCount + 1) + '/' + maxAutomaticRestarts + ')');
    restartTimer = setTimeout(() => {
        app.relaunch({ args: relaunchArgs });
        app.exit(1);
    }, 5000);
}


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

// https://github.com/electron/electron/issues/17972
app.commandLine.appendSwitch('--no-sandbox');
app.commandLine.appendSwitch('no-sandbox');

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

    config.load();

    log.initialize();
    log.transports.file.resolvePathFn = resolveLogPath;

    log.info('----------------------------------------------');
    log.info('Starting Tooloop Kiosk Browser...');
    log.info('Logging to ' + log.transports.file.resolvePathFn());

    registerWatchdogBridge();
    createMenu();
    createMainWindow();
});

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

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

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

// prevent error dialogs in case of exceptions
process.on('uncaughtException', restartAfterFatalError);
process.on('unhandledRejection', restartAfterFatalError);