docs: add comments to functions for better understanding

frontend/src/app/services/movie.service.ts

@@ -21,20 +21,46 @@ export class MovieService {
     private authService: AuthService
   ) {}
 
+  /**
+   * Fetch all movies available on the server
+   *
+   * @returns a promise resolving to an array of movie objects
+   */
   getAllMovies(): Promise<any> {
     return firstValueFrom(this.apiService.get('/video/', true));
   }
 
+  /**
+   * Fetch a movie by its video URL
+   *
+   * @param videoUrl the ID of the movie to fetch
+   * @returns a promise resolving to the movie object
+   */
   getMovieFiles(videoUrl: number): Promise<any> {
     return firstValueFrom(this.apiService.get(`/${videoUrl}`, true));
   }
 
+  /**
+   * Upload a movie to the server
+   *
+   * @param formData the FormData object representing the movie to upload
+   * @returns a promise resolved when the upload is successful
+   */
   uploadMovie(formData: FormData): Promise<any> {
     return firstValueFrom(
       this.apiService.post('/video/upload/', formData, true)
     );
   }
 
+  /**
+   * Checks if a movie with the given video ID has been uploaded in the following resolutions: 360p, 720p, 1080p.
+   *
+   * @param videoID the ID of the movie to check
+   * @returns an observable that emits an object with the following properties:
+   *  - '360': a boolean indicating whether the movie has been uploaded in 360p resolution
+   *  - '720': a boolean indicating whether the movie has been uploaded in 720p resolution
+   *  - '1080': a boolean indicating whether the movie has been uploaded in 1080p resolution
+   */
   isMovieResolutionUploaded(
     videoID: number
   ): Observable<{ [resolution: string]: boolean }> {

frontend/src/app/services/token.service.ts

@@ -9,12 +9,24 @@ export class TokenService {
 
   constructor(private router: Router) {}
 
+  /**
+   * Store the given authentication token in either local or session storage.
+   *
+   * @param token The authentication token to store.
+   * @param storage Whether to store the token in local storage (true) or session storage (false).
+   */
   setToken(token: string, storage: boolean): void {
     storage
       ? localStorage.setItem(this.TOKEN_KEY, token)
       : sessionStorage.setItem(this.TOKEN_KEY, token);
   }
 
+  /**
+   * Returns the authentication token if it exists in either local or session storage.
+   * Note that session storage takes precedence over local storage.
+   *
+   * @returns The authentication token if found, or null otherwise.
+   */
   getToken(): string | null {
     const tokenFromSession = sessionStorage.getItem(this.TOKEN_KEY);
     if (tokenFromSession) {
@@ -25,11 +37,18 @@ export class TokenService {
     return tokenFromLocal;
   }
 
+  /**
+   * Remove the authentication token from both local and session storage.
+   * Note that this does not navigate the user away from the current page.
+   */
   removeToken(): void {
     localStorage.removeItem(this.TOKEN_KEY);
     sessionStorage.removeItem(this.TOKEN_KEY);
   }
 
+  /**
+   * Clear the session by removing the token from storage and navigating to the home route.
+   */
   clearSession(): void {
     this.removeToken();
     this.router.navigate(['/']);

frontend/src/app/services/user.service.ts

@@ -10,12 +10,25 @@ export class UserService {
 
   constructor(private apiService: ApiService) {}
 
+  /**
+   * Fetch the list of movies liked and watched by the current user
+   *
+   * @returns a promise resolving to an object with two properties:
+   *   - `liked_movies`: a list of movie IDs liked by the current user
+   *   - `watched_movies`: a list of movie IDs watched by the current user
+   */
   getLikedAndWatchedMovies(): Promise<any> {
     return firstValueFrom(
       this.apiService.get(`/users/${this.currentUserId}/`, true)
     );
   }
 
+  /**
+   * Update the list of liked movies for the current user
+   *
+   * @param likedMovies a list of movie IDs liked by the current user
+   * @returns a promise resolved when the update is successful
+   */
   updateLikedMovies(likedMovies: any): Promise<any> {
     return firstValueFrom(
       this.apiService.put(

frontend/src/app/shared/components/error-toast/error-toast.component.ts

@@ -13,16 +13,29 @@ export class ErrorToastComponent implements OnInit {
 
   constructor(private errorService: ErrorService) {}
 
+  /**
+   * Listens to the errorText$ observable and updates the component's errorText
+   * property with the latest error message.
+   */
   ngOnInit(): void {
     this.errorService.errorText$.subscribe((message: string) => {
       this.errorText = message;
     });
   }
 
+  /**
+   * Stops the propagation of an event to prevent the component from closing
+   * when the user clicks on the error message.
+   * @param event The MouseEvent to stop propagating.
+   */
   stopPropagation(event: MouseEvent) {
     event.stopPropagation();
   }
 
+  /**
+   * Clears the current error message from the error service when the user clicks
+   * anywhere outside the error toast.
+   */
   closeError() {
     this.errorService.clearError();
   }

frontend/src/app/shared/components/header/header.component.ts

@@ -20,10 +20,19 @@ export class HeaderComponent {
     private tokenService: TokenService
   ) {}
 
+  /**
+   * Emits the moviesChange event with the newMovies array as the payload.
+   * This is used to reset the movies displayed in the movie-list component.
+   * @param newMovies The new array of movies to be displayed.
+   */
   backToOverview(newMovies: any[]) {
     this.moviesChange.emit(newMovies);
   }
 
+  /**
+   * Logs out the user by calling the logout method of AuthService and clears the session using TokenService.
+   * If an error occurs during the process, it is logged to the console.
+   */
   async logout() {
     try {
       await this.authService.logout();