@Override
    public String exportUsersWithTheirPosts() {
        StringBuilder result = new StringBuilder();
        List<User> users = this.userRepository.findAll();

        Map<String, List<Post>> userPosts = new HashMap<>();

        for (User user : users) {
            List<Post> posts = this.postRepository.findByUserOrderByPictureSize(user);
            userPosts.put(user.getUsername(), posts);
        }

        users.sort((o1, o2) -> {
            int result1 = Integer.compare(userPosts.get(o2.getUsername()).size(), userPosts.get(o1.getUsername()).size());
            if (result1 == 0) {
                result1 = Integer.compare(o1.getId(), o2.getId());
            }
            return result1;
        });

        for (User user : users) {
            List<Post> posts = userPosts.get(user.getUsername());

            result.append("User: ").append(user.getUsername()).append(System.lineSeparator());
            result.append("Post count: ").append(posts.size()).append(System.lineSeparator());

            for (Post post : posts) {
                result.append("==Post Details:").append(System.lineSeparator());
                result.append("----Caption: ").append(post.getCaption()).append(System.lineSeparator());
                result.append(String.format("----Picture Size: %.2f%n", post.getPicture().getSize()));
            }
        }

        return result.toString().trim();
    }