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Low Level Design (LLD) Coding

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Design (LLD) Twitter - Machine Coding

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techlinks.in
·Dec 31, 2022·

5 min read

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Low-level design (LLD) for Twitter:

  1. User accounts and authentication: Twitter will need to allow users to create accounts, log in, and log out. We will also need to implement measures to ensure the security of user accounts, such as password hashing and potentially two-factor authentication.

  2. Tweet creation and posting: Twitter will need to allow users to create and post tweets, which will involve creating forms and handling the associated server-side logic to process the input and store the tweets in a database.

  3. User profiles and followers: Twitter will need to store information about users, such as their username, display name, and bio, as well as allow users to follow and be followed by other users. This will likely involve creating tables or data structures to store this information and implementing the necessary logic to manage the relationships between users.

  4. Timeline and feed: Twitter will need to display a timeline or feed of tweets to each user, which will involve querying the database for the relevant tweets and displaying them to the user.

  5. Search and hashtags: Twitter will need to allow users to search for tweets and users, as well as support hashtags to allow users to discover tweets about specific topics. This will involve implementing search functionality and handling any interactions with the server-side logic.

  6. User interface: Finally, Twitter will need to design the user interface for the service, including the layout, navigation, and any necessary graphics or styling. This will involve creating wireframes and mockups, as well as implementing the front-end code to bring the design to life.

Here is an example of the implementation of a low-level design of a Twitter-like social media platform in Java:

public class Twitter {
    private Map<String, User> users;
    private Map<Long, Tweet> tweets;
    private Map<String, List<Notification>> notifications;

    public Twitter() {
        this.users = new HashMap<>();
        this.tweets = new HashMap<>();
        this.notifications = new HashMap<>();
    }

    public void createUser(String name, String username, String profilePictureUrl) {
        User user = new User(name, username, profilePictureUrl);
        users.put(username, user);
    }

    public void followUser(String followerUsername, String followeeUsername) {
        User follower = users.get(followerUsername);
        User followee = users.get(followeeUsername);
        follower.follow(followee);
        followee.addFollower(follower);
    }

    public void createTweet(String username, String text) {
        User user = users.get(username);
        Tweet tweet = new Tweet(user, text, LocalDateTime.now());
        tweets.put(tweet.getId(), tweet);
        user.addTweet(tweet);
        notifyFollowers(tweet);
    }

    public void likeTweet(String username, long tweetId) {
        User user = users.get(username);
        Tweet tweet = tweets.get(tweetId);
        tweet.addLike(user);
        user.addLikedTweet(tweet);
        notifyUser(tweet.getUser(), tweet, NotificationType.LIKE);
    }

    public void commentOnTweet(String username, long tweetId, String text) {
        User user = users.get(username);
        Tweet tweet = tweets.get(tweetId);
        Comment comment = new Comment(user, text, LocalDateTime.now());
        tweet.addComment(comment);
        user.addCommentedTweet(tweet);
        notifyUser(tweet.getUser(), tweet, NotificationType.COMMENT);
    }

    public List<Tweet> searchTweets(String query) {
        // search the tweets for the given query
    }

    public List<String> getTrendingHashtags() {
        // retrieve the most popular hashtags
    }

    private void notifyFollowers(Tweet tweet) {
        String username = tweet.getUser().getUsername();
        List<Notification> userNotifications = notifications.get(username);
        for (User follower : tweet.getUser().getFollowers()) {
            Notification notification = new Notification(tweet, follower, NotificationType.TWEET);
            userNotifications.add(notification);
            follower.addNotification(notification);
        }
    }

    private void notifyUser(User user, Tweet tweet, NotificationType type) {
        List<Notification> userNotifications = notifications.get(user.getUsername());
        Notification notification = new Notification(tweet, user, type);
        userNotifications.add(notification);
        user.addNotification(notification);
    }
}
public class User {
    private String name;
    private String username;
    private String profilePictureUrl;
    private Set<User> followers;
    private Set<User> following;
    private List<Tweet> tweets;
    private List<Tweet> likedTweets;
    private List<Tweet> commentedTweets;
    private List<Notification> notifications;

    public User(String name, String username, String profilePictureUrl) {
        this.name = name;
        this.username = username;
        this.profilePictureUrl = profilePictureUrl;
        this.followers = new HashSet<>();
        this.following = new HashSet<>();
        this.tweets = new ArrayList<>();
        this.likedTweets = new ArrayList<>();
        this.commentedTweets = new ArrayList<>();
        this.notifications = new ArrayList<>();
    }

    public void follow(User user) {
        following.add(user);
    }

    public void addFollower(User user) {
        followers.add(user);
    }

    public void addTweet(Tweet tweet) {
        tweets.add(tweet);
    }

    public void addLikedTweet(Tweet tweet) {
        likedTweets.add(tweet);
    }

    public void addCommentedTweet(Tweet tweet) {
        commentedTweets.add(tweet);
    }

    public void addNotification(Notification notification) {
        notifications.add(notification);
    }

    public String getName() {
        return name;
    }

    public String getUsername() {
        return username;
    }

    public String getProfilePictureUrl() {
        return profilePictureUrl;
    }

    public Set<User> getFollowers() {
        return followers;
    }

    public Set<User> getFollowing() {
        return following;
    }

    public List<Tweet> getTweets() {
        return tweets;
    }

    public List<Tweet> getLikedTweets() {
        return likedTweets;
    }

    public List<Tweet> getCommentedTweets() {
        return commentedTweets;
    }

    public List<Notification> getNotifications() {
        return notifications;
    }
}
public class Tweet {
    private long id;
    private User user;
    private String text;
    private LocalDateTime createdAt;
    private Set<User> likes;
    private List<Comment> comments;

    public Tweet(User user, String text, LocalDateTime createdAt) {
        this.id = IdGenerator.generateId();
        this.user = user;
        this.text = text;
        this.createdAt = createdAt;
        this.likes = new HashSet<>();
        this.comments = new ArrayList<>();
    }

    public void addLike(User user) {
        likes.add(user);
    }

    public void addComment(Comment comment) {
        comments.add(comment);
    }

    public long getId() {
        return id;
    }

    public User getUser() {
        return user;
    }

    public String getText() {
        return text;
    }

    public LocalDateTime getCreatedAt() {
        return createdAt;
    }

    public Set<User> getLikes() {
        return likes;
    }

    public List<Comment> getComments() {
        return comments;
    }
}
public class Comment {
    private long id;
    private User user;
    private Tweet tweet;
    private String text;
    private LocalDateTime createdAt;

    public Comment(User user, Tweet tweet, String text, LocalDateTime createdAt) {
        this.id = IdGenerator.generateId();
        this.user = user;
        this.tweet = tweet;
        this.text = text;
        this.createdAt = createdAt;
    }

    public long getId() {
        return id;
    }

    public User getUser() {
        return user;
    }

    public Tweet getTweet() {
        return tweet;
    }

    public String getText() {
        return text;
    }

    public LocalDateTime getCreatedAt() {
        return createdAt;
    }
}
public class Notification {
    private long id;
    private User user;
    private String text;
    private LocalDateTime createdAt;
    private boolean read;

    public Notification(User user, String text, LocalDateTime createdAt) {
        this.id = IdGenerator.generateId();
        this.user = user;
        this.text = text;
        this.createdAt = createdAt;
        this.read = false;
    }

    public long getId() {
        return id;
    }

    public User getUser() {
        return user;
    }

    public String getText() {
        return text;
    }

    public LocalDateTime getCreatedAt() {
        return createdAt;
    }

    public boolean isRead() {
        return read;
    }

    public void setRead(boolean read) {
        this.read = read;
    }
}

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