This PR includes the current progress for the migration of the AngularJS frontend to Angular.
There is still a lot of work left to do, but I think now would be a good time to get some feedback on the code.

Overview

The new frontend consists of one Angular app and two Angular libraries:

• guacamole-frontend

  • contains the main application

• guacamole-frontend-lib

  • contains components that could be useful when building a custom Guacamole-Angular application

• guacamole-frontend-ext-lib

  • contains services and classes for extensions that provide a clear interface for registering additional routes and field types

The application and both libraries are included in the maven build.

TODOs:

• any changes and new features after revision 4664764 (2023-06-02)
• migrate import module
• migrate index/services/iconService.js
• migrate manage/directives/connectionPermissionEditor.js
• migrate manage/controllers/manageSharingProfileController.js
• caching of API responses
• refactor the managed client so that reusable code can be moved to the guacamole-frontend-lib
• some documentation in the code is missing
• TODOs in the code
• code style might not be correct all the time
• some styles are not applied properly since Angular's components introduce additional DOM elements
• the functionality to serve complex extensions from the Java code
• guacamole-common-js should be copied to the frontend in the build process. At the moment I just included a copy at projects/guacamole-frontend-lib/src/assets/. Are there any plans to release an official NPM package for guacamole-common-js?
• type declarations for guacamole-common-js (projects/guacamole-frontend-lib/src/lib/types/Guacamole.ts). They will be replaced by the package @types/guacamole-common-js once it is updated.
• automatic generation of the LICENSE and NOTICE files in the maven build.
  The angular build creates a 3rdpartylicenses.txt file, but I don't really know what to do with it.
  Any comments on this will be appreciated.
• Do not assume that the application is always deployed at /guacamole/

Extensions

The biggest challenge in the migration was to build an extension system in Angular that was as flexible as the one in AngularJS.

• Adding and modifying translation strings was mostly handled by the REST API and should work like before.
• Inject additional HTML and CSS should work just like in AngularJS.
  • See apply-patches.service.ts and style-loader.service.ts
    in projects/guacamole-frontend/src/app/index/services/
• More complex extensions can now be implemented as a separate Angular application
  • Extensions are loaded as a remote module via webpack module federation and the module federation plugin for Angular. Routes and form field can be added by implementing a bootstrap function. Adding custom Angular components to arbitrary locations will also be possible.
  • See doc/guacamole-frontend-extension-example for an example.
  • Note: the module federation configuration file (at the moment hard coded as projects/guacamole-frontend/src/moduleFederation/mf.manifest.json ) should be generated by the Java server in the future

Implementation notes

• AngularJS services that mostly serve as data containers are replaced by simple classes with instance or static
  methods. Some of the more complex services are replaced by Angular services.
• Named functions are mostly replaced by arrow functions.
• Functions that return a promise with data from REST API are mostly replaced by functions that return an RxJS observable.
• AngularJS's directives are replaced by Angular...
  • components if they are configured with restrict: 'E',
  • directives if they are configured with restrict: 'A'.
• All styles are defined globally so that they can be overritten by extension styles
• The authentication service method to perform HTTP request with the current token (AuthenticationService.request())
  is replaced by a HTTP interceptor
  (auth/interceptor/authentication.interceptor.ts).
• The error handling of the HTTP requests (rest/services/requestService.js) is replaced by a HTTP interceptor
  (rest/interceptor/error-handling.interceptor.ts).
• The configuration of the $http service (httpDefaults.js) is replaced by an HTTP
  interceptor (index/config/default-headers.interceptor.ts).
• To disable certain interceptors for specific requests, the HttpContextTokens in the InterceptorService can be used.
• angular-translate is replaced by transloco (https://ngneat.github.io/transloco/).
  • A noticeable difference is that transloco uses double curly braces by default to link to other translations keys
    instead of the @: prefix. However, I change it to @:...:@ to prevent transcloco from removing parts of ICU messages (Bug(messageformat): Plural translation starting and ending with a variables fails jsverse/transloco#621).
• I refactored the GuacFileBrowser to simply use an *ngFor loop. In my tests I didn't notice any performance issues.
• I added Cypress for E2E Tests in the cypress folder. The tests are not integrated in the build process, and I did not
  include a proper configuration file because of the various possible testing setups.
• I removed workarounds for IE since Angular itself does no longer support IE. Should these workarounds still be
  kept?
  • TunnelService~uploadToStream
  • TunnelService~downloadStream
  • UserCredentials.getLink
  • UserCredentialService~getLink
• To replace the $parse function of AngularJS I used the NPM package angular-expressions
  which is a copy of the AngularJS code as standalone module.
• There are some more questions directly in the code marked as a TODO.

Running the code

For my setup the easiest way to run the code was to build the frontend with maven and use the war file in a docker-compose setup. Since the module federation config is hard coded for now there will be some errors when the example extension (doc/guacamole-frontend-extension-example) is not running (ng serve) at localhost:4202. If the extension is running, the content will be available at /extension-example.

It is also possible to run the frontend using ng serve and benefit from live reloading with a way to work around the same origin policy (modify HTTP headers/proxy/disable web security). Therefore, the libraries need to be built manually: ng build guacamole-frontend-lib and ng build guacamole-frontend-ext-lib. Additionally, the following code might be necessary to redirect the requests to the REST API:

// projects/guacamole-frontend/src/app/auth/interceptor/authentication.interceptor.ts
if(!request.url.startsWith('assets'))
    request = request.clone({url: `http://localhost:8080/guacamole/${request.url}`});

// projects/guacamole-frontend/src/app/client/services/managed-client.service.ts getInstance()
  tunnel = new Guacamole.ChainedTunnel(
      new Guacamole.WebSocketTunnel('ws://localhost:8080/guacamole/websocket-tunnel'),
      new Guacamole.HTTPTunnel('http://localhost:8080/guacamole/tunnel')

When using ng serve, the REST API from this branch should still be used.

To run the Cypress test I used the following configuration to disable web security for Chrome:

// guacamole/src/main/guacamole-frontend/cypress.config.ts
e2e: {
  setupNodeEvents(on, config) {
      on('before:browser:launch', (browser, launchOptions) => {

          if (browser.family === 'chromium') {
              launchOptions.args.push('--disable-web-security');
          }

          return launchOptions;
      })
  },
  baseUrl: "http://localhost:4200"
}