import {app, shell} from 'electron';
import {URL} from 'url';

/**
 * List of origins that you allow open INSIDE the application and permissions for each of them.
 *
 * In development mode you need allow open `VITE_DEV_SERVER_URL`
 */
const ALLOWED_ORIGINS_AND_PERMISSIONS = new Map<string, Set<'clipboard-read' | 'media' | 'display-capture' | 'mediaKeySystem' | 'geolocation' | 'notifications' | 'midi' | 'midiSysex' | 'pointerLock' | 'fullscreen' | 'openExternal' | 'unknown'>>(
  import.meta.env.DEV && import.meta.env.VITE_DEV_SERVER_URL
    ? [[new URL(import.meta.env.VITE_DEV_SERVER_URL).origin, new Set]]
    : [],
);

/**
 * List of origins that you allow open IN BROWSER.
 * Navigation to origins below is possible only if the link opens in a new window
 *
 * @example
 * <a
 *   target="_blank"
 *   href="https://github.com/"
 * >
 */
const ALLOWED_EXTERNAL_ORIGINS = new Set<`https://${string}`>([
  'https://github.com',
]);


app.on('web-contents-created', (_, contents) => {

  /**
   * Block navigation to origins not on the allowlist.
   *
   * Navigation is a common attack vector. If an attacker can convince the app to navigate away
   * from its current page, they can possibly force the app to open web sites on the Internet.
   *
   * @see https://www.electronjs.org/docs/latest/tutorial/security#13-disable-or-limit-navigation
   */
  contents.on('will-navigate', (event, url) => {
    const {origin} = new URL(url);
    if (ALLOWED_ORIGINS_AND_PERMISSIONS.has(origin)) {
      return;
    }

    // Prevent navigation
    event.preventDefault();

    if (import.meta.env.DEV) {
      console.warn('Blocked navigating to an unallowed origin:', origin);
    }
  });


  /**
   * Block requested unallowed permissions.
   * By default, Electron will automatically approve all permission requests.
   *
   * @see https://www.electronjs.org/docs/latest/tutorial/security#5-handle-session-permission-requests-from-remote-content
   */
  contents.session.setPermissionRequestHandler((webContents, permission, callback) => {
    const {origin} = new URL(webContents.getURL());

    const permissionGranted = !!ALLOWED_ORIGINS_AND_PERMISSIONS.get(origin)?.has(permission);
    callback(permissionGranted);

    if (!permissionGranted && import.meta.env.DEV) {
      console.warn(`${origin} requested permission for '${permission}', but was blocked.`);
    }
  });


  /**
   * Hyperlinks to allowed sites open in the default browser.
   *
   * The creation of new `webContents` is a common attack vector. Attackers attempt to convince the app to create new windows,
   * frames, or other renderer processes with more privileges than they had before; or with pages opened that they couldn't open before.
   * You should deny any unexpected window creation.
   *
   * @see https://www.electronjs.org/docs/latest/tutorial/security#14-disable-or-limit-creation-of-new-windows
   * @see https://www.electronjs.org/docs/latest/tutorial/security#15-do-not-use-openexternal-with-untrusted-content
   */
  contents.setWindowOpenHandler(({url}) => {
    const {origin} = new URL(url);

    // @ts-expect-error Type checking is performed in runtime
    if (ALLOWED_EXTERNAL_ORIGINS.has(origin)) {
      // Open default browser
      shell.openExternal(url).catch(console.error);

    } else if (import.meta.env.DEV) {
      console.warn('Blocked the opening of an unallowed origin:', origin);
    }

    // Prevent creating new window in application
    return {action: 'deny'};
  });


  /**
   * Verify webview options before creation
   *
   * Strip away preload scripts, disable Node.js integration, and ensure origins are on the allowlist.
   *
   * @see https://www.electronjs.org/docs/latest/tutorial/security#12-verify-webview-options-before-creation
   */
  contents.on('will-attach-webview', (event, webPreferences, params) => {
    const {origin} = new URL(params.src);
    if (!ALLOWED_ORIGINS_AND_PERMISSIONS.has(origin)) {

      if (import.meta.env.DEV) {
        console.warn(`A webview tried to attach ${params.src}, but was blocked.`);
      }

      event.preventDefault();
      return;
    }

    // Strip away preload scripts if unused or verify their location is legitimate
    delete webPreferences.preload;
    // @ts-expect-error `preloadURL` exists - see https://www.electronjs.org/docs/latest/api/web-contents#event-will-attach-webview
    delete webPreferences.preloadURL;

    // Disable Node.js integration
    webPreferences.nodeIntegration = false;
  });
});