TextTwitter.java

/* SELF NOTES: Started Jan 2nd 2025. Finished March 11th 2025 (hurray)
   Currently learning C++ might do it in that language for practice.
   Shout out to the Liang textbook and my TA for always checking my code and
   helping me out in ideas or new methods to try.
 */

import java.io.*;
import java.util.*;

public class TextTwitter {

    //  Map to store users, using the username as the key and User object as the value
    private static Map<String, User> users = new HashMap<>();
    // The currently logged-in user
    private static User currentUser = null;
    // File names for saving and loading user and tweet data
    private static final String USER_DATA_FILE = "users_data.txt";
    private static final String TWEETS_DATA_FILE = "tweets_data.txt";
    private static Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) {
        // Load users and tweets data from the files
        loadUsersData();
        loadTweetsData();

        // Main loop for the program
        while (true) {
            // Display the menu
            showMenu();
            // Get the user's choice from input
            int choice = scanner.nextInt();
            scanner.nextLine(); // Consume newline left-over

            // Process the user's choice
            switch (choice) {
                case 1:
                    registerUser(); // Register a new user
                    break;
                case 2:
                    loginUser(); // Log in an existing user
                    break;
                case 3:
                    postTweet(); // Post a new tweet
                    break;
                case 4:
                    displayAllTweets(); // View all tweets
                    break;
                case 5:
                    followUser(); // Follow another user
                    break;
                case 6:
                    likeTweet(); // Like a tweet
                    break;
                case 7:
                    logout(); // Log out the current user
                    break;
                case 8:
                    exit(); // Exit the program
                    return;
                default:
                    System.out.println("Invalid choice! Try again.");
            }
        }
    }

    // Displays the main menu based on the current user status (logged in or not)
    private static void showMenu() {
        System.out.println("\nWelcome to TextTwitter!");
        if (currentUser == null) {
            // If not logged in, show options for registering or logging in
            System.out.println("1. Register a new user");
            System.out.println("2. Login");
        } else {
            // If logged in, show options for tweeting, following, and liking
            System.out.println("Logged in as: " + currentUser.username);
            System.out.println("3. Post a tweet");
            System.out.println("4. View all tweets");
            System.out.println("5. Follow a user");
            System.out.println("6. Like a tweet");
            System.out.println("7. Logout");
        }
        // Always show exit option
        System.out.println("8. Exit");
        System.out.print("Choose an option: ");
    }

    // Registers a new user by getting their username and password
    private static void registerUser() {
        System.out.print("Enter username to register: ");
        String username = scanner.nextLine();

        // Check if the username already exists
        if (users.containsKey(username)) {
            System.out.println("Username already exists! Please choose a different one.");
            return;
        }

        System.out.print("Enter a password: ");
        String password = scanner.nextLine();

        // Create a new User and store it in the map
        User newUser = new User(username, password);
        users.put(username, newUser);
        saveUsersData(); // Save updated user data to file
        System.out.println("User registered successfully!");
    }

    // Logs in an existing user by verifying their username and password
    private static void loginUser() {
        System.out.print("Enter username to login: ");
        String username = scanner.nextLine();

        // Check if the user exists in the database
        if (!users.containsKey(username)) {
            System.out.println("User not found! Please register first.");
            return;
        }

        System.out.print("Enter password: ");
        String password = scanner.nextLine();

        // Verify the password
        User user = users.get(username);
        if (user.password.equals(password)) {
            currentUser = user;
            System.out.println("Logged in successfully!");
        } else {
            System.out.println("Incorrect password! Try again.");
        }
    }

    // Allows the logged-in user to post a tweet
    private static void postTweet() {
        if (currentUser == null) {
            System.out.println("You need to log in first!");
            return;
        }

        // Get the tweet message from the user
        System.out.print("What's happening? ");
        String message = scanner.nextLine();
        currentUser.postTweet(message); // Post the tweet using the User object
        saveTweetsData(); // Save the tweet data to file
        System.out.println("Tweet posted!");
    }

    // Displays all tweets from users the current user is following or their own tweets
    private static void displayAllTweets() {
        if (currentUser == null) {
            System.out.println("You need to log in first!");
            return;
        }

        // Loop through all users and display tweets from followed users or the current user
        for (User user : users.values()) {
            if (currentUser.isFollowing(user.username) || user.username.equals(currentUser.username)) {
                user.displayTweets(); // Show tweets from the user
            }
        }
    }

    // Allows the current user to follow another user
    private static void followUser() {
        if (currentUser == null) {
            System.out.println("You need to log in first!");
            return;
        }

        System.out.print("Enter the username to follow: ");
        String username = scanner.nextLine();

        // Check if the user to follow exists
        if (!users.containsKey(username)) {
            System.out.println("User not found!");
            return;
        }

        if (username.equals(currentUser.username)) {
            System.out.println("You can't follow yourself!");
            return;
        }

        // Follow the user and add the current user as a follower of the target user
        currentUser.followUser(username);
        users.get(username).addFollower(currentUser.username);
        System.out.println("Now following @" + username);
    }

    // Allows the current user to like a tweet
    private static void likeTweet() {
        if (currentUser == null) {
            System.out.println("You need to log in first!");
            return;
        }

        System.out.print("Enter the username of the tweet you want to like: ");
        String username = scanner.nextLine();

        // Check if the user exists
        if (!users.containsKey(username)) {
            System.out.println("User not found!");
            return;
        }

        User user = users.get(username);
        user.displayTweets(); // Display all tweets from the user

        // Get the tweet index to like
        System.out.print("Enter the index of the tweet to like: ");
        int index = scanner.nextInt();
        scanner.nextLine(); // Consume newline left-over

        // Check if the tweet index is valid
        if (index < 0 || index >= user.tweets.size()) {
            System.out.println("Invalid tweet index!");
            return;
        }

        Tweet tweet = user.tweets.get(index);
        currentUser.likeTweet(tweet); // Like the tweet
        System.out.println("You liked the tweet!");
    }

    // Logs out the current user
    private static void logout() {
        if (currentUser != null) {
            System.out.println("Logged out successfully!");
            currentUser = null;
        } else {
            System.out.println("You're not logged in!");
        }
    }

    // Exits the program and saves all data
    private static void exit() {
        System.out.println("Goodbye!");
        saveUsersData(); // Save all users' data to file
        saveTweetsData(); // Save all tweets' data to file
    }

    // Loads user data from the file and populates the users map
    private static void loadUsersData() {
        try (BufferedReader reader = new BufferedReader(new FileReader(USER_DATA_FILE))) {
            String line;
            while ((line = reader.readLine()) != null) {
                // Split the line to get username and password
                String[] userInfo = line.split(",");
                String username = userInfo[0];
                String password = userInfo[1];
                // Create and store the user
                User user = new User(username, password);
                users.put(username, user);
            }
        } catch (IOException e) {
            System.out.println("No previous user data found.");
        }
    }

    // Saves all users' data to the file
    private static void saveUsersData() {
        try (BufferedWriter writer = new BufferedWriter(new FileWriter(USER_DATA_FILE))) {
            // Loop through all users and save their data to the file
            for (User user : users.values()) {
                writer.write(user.username + "," + user.password);
                writer.newLine();
            }
        } catch (IOException e) {
            System.out.println("Error saving user data.");
        }
    }

    // Loads tweet data from the file and populates users' tweets
    private static void loadTweetsData() {
        try (BufferedReader reader = new BufferedReader(new FileReader(TWEETS_DATA_FILE))) {
            String line;
            while ((line = reader.readLine()) != null) {
                // Split the line to get username and tweet message
                String[] tweetData = line.split(",", 2);
                String username = tweetData[0];
                String message = tweetData[1];
                // If the user exists, post the tweet
                if (users.containsKey(username)) {
                    users.get(username).postTweet(message);
                }
            }
        } catch (IOException e) {
            System.out.println("No previous tweet data found.");
        }
    }

    // Saves all tweets' data to the file
    private static void saveTweetsData() {
        try (BufferedWriter writer = new BufferedWriter(new FileWriter(TWEETS_DATA_FILE))) {
            // Loop through all users and their tweets and save them to the file
            for (User user : users.values()) {
                for (Tweet tweet : user.tweets) {
                    writer.write(tweet.username + "," + tweet.message);
                    writer.newLine();
                }
            }
        } catch (IOException e) {
            System.out.println("Error saving tweet data.");
        }
    }
}