Lignes et tchat

public record Point2D(BigDecimal x, BigDecimal y) {}

public class Line {
  private final Point2D point1;
  private final Point2D point2;
  public Line(Point2D point1, Point2D point2) {
    this.point1 = point1;
    this.point2 = point2;
  }
  public BigDecimal distance(Point2D point) {
    // Context d'opération avec 10000 chiffres significatifs
    MathContext mathContext = new MathContext(10000); 
    BigDecimal x2MinusX1 = point2.x().subtract(point1.x());
    BigDecimal y2MinusY1 = point2.y().subtract(point1.y());
    BigDecimal x1MinusX0 = point1.x().subtract(point.x());
    BigDecimal y1MinusY0 = point1.y().subtract(point.y());
    BigDecimal resultNumerator = 
        (x2MinusX1.multiply(y1MinusY0)).subtract(x1MinusX0.multiply(y2MinusY1));
    BigDecimal resultDenominator = 
        (x2MinusX1.pow(2).add(y2MinusY1.pow(2))).sqrt(mathContext);
    return (resultNumerator.divide(resultDenominator, mathContext)).abs();
  }
  public boolean contains(Point2D point) { return distance(point).compareTo(BigDecimal.ZERO) == 0; }
  public Point2D point1() { return point1; }
  public Point2D point2() { return point2; }
}

public class Segment extends Line {
  public Segment(Point2D point1, Point2D point2) {
    super(point1, point2);
  }
  public boolean contains(Point2D point) {
    BigDecimal minX = point1().x().min(point2().x());
    BigDecimal maxX = point1().x().max(point2().x());
    BigDecimal minY = point1().y().min(point2().y());
    BigDecimal maxY = point1().y().max(point2().y());
    return super.contains(point)
            && point.x().compareTo(minX) >= 0 && point.x().compareTo(maxX) <= 0
            && point.y().compareTo(minY) >= 0 && point.y().compareTo(maxY) <= 0;
  }
}

public class App {
    public static void main(String[] args) {
        BigDecimal five = new BigDecimal("5");
        BigDecimal ten = new BigDecimal("10");
        BigDecimal fifteen = new BigDecimal("15");
        BigDecimal twenty = new BigDecimal("20");
        BigDecimal thirty = new BigDecimal("30");
        Point2D p1 = new Point2D(ten, ten);
        Point2D p2 = new Point2D(twenty, twenty);
        Line line = new Line(p1, p2);
        Line segment = new Segment(p1, p2);
        System.out.println(line.contains(new Point2D(fifteen, fifteen)));
        System.out.println(line.contains(new Point2D(thirty, thirty)));
        System.out.println(line.contains(new Point2D(five, thirty)));
        System.out.println(segment.contains(new Point2D(thirty, thirty)));
    }
}

public class App {
    public static void main(String[] args) {
        BigDecimal five = new BigDecimal("5");
        BigDecimal ten = new BigDecimal("10");
        BigDecimal fifteen = new BigDecimal("15");
        BigDecimal twenty = new BigDecimal("20");
        BigDecimal thirty = new BigDecimal("30");
        Point2D p1 = new Point2D(ten, ten);
        Point2D p2 = new Point2D(twenty, twenty);
        Shape line = new Line(p1, p2);
        Shape segment = new Segment(p1, p2);
        System.out.println(line.contains(new Point2D(fifteen, fifteen)));
        System.out.println(line.contains(new Point2D(thirty, thirty)));
        System.out.println(line.contains(new Point2D(five, thirty)));
        System.out.println(segment.contains(new Point2D(thirty, thirty)));
    }
}

public class User {
    private Server server;
    private final boolean isAdmin;
    private String userName;
    public User(String userName, boolean isAdmin) {
        this.userName = userName;
        this.server = null;
        this.isAdmin = isAdmin;
    }
    public void executeCommand(String commandLine) {
        if(server == null) {
            throw new IllegalStateException("Server not initialized");
        }
        String[] tokens = commandLine.split(" ");
        String commandName = tokens[0];
        String commandArgument = tokens[1];
        switch (commandName) {
            case "broadcast" -> runBroadcastCommand(commandArgument);
            case "set_username" -> runSetUserNameCommand(commandArgument);
            case "kick" -> {if (isAdmin) runKickCommand(commandArgument);}
            default -> System.out.println("Unknown command: " + commandName);
        }
    }
    public void setUserName(String userName) { this.userName = userName; }
    public String username() { return userName; }
    private void runSetUserNameCommand(String commandArgument) {
        if (server.usernameExists(commandArgument)) return;
        this.setUserName(commandArgument);
    }
    private void runBroadcastCommand(String commandArgument) {
        server.broadcastMessage(this, commandArgument);
    }
    private void runKickCommand(String commandArgument) {
        User kickedUser = server.getUserByName(commandArgument);
        if (kickedUser==null) return;
        server.closeConnection(kickedUser);
    }
    public void setServer(Server server) { this.server = server; }
}

/**
 * Represents a server interface that provides methods to manage users and broadcast 
 * messages.
 */
public interface Server {
    /**
     * Checks if a username already exists among the connected users.
     *
     * @param username The username to check.
     * @return {@code true} if the username exists, {@code false} otherwise.
     */
    boolean usernameExists(String username);
    /**
     * Broadcasts a message from the sender to all connected users.
     *
     * @param sender  The user sending the message.
     * @param message The message to broadcast.
     */
    void broadcastMessage(User user, String message);
    /**
     * Retrieves a user object by their username.
     *
     * @param username the username of the user to retrieve
     * @return the {@link User} object if the user exists, or {@code null} if not found
     */
    User getUserByName(String username);
    /**
     * Removes a user from the server and terminates their connection.
     *
     * @param kickedUser The user to disconnect from the server.
     */
    void closeConnection(User kickedUser);
    /**
     * Adds a user to the server and establishes a connection.
     *
     * @param user The user to connect to the server.
     */
    void connectUser(User user);
}

public class MainAppServer {
    public static void main(String[] args) {
        Server server = new ServerSimulator();
        User david = new User("david", true);
        server.connectUser(david);
        User jeanMichel = new User("jean-michel", false);
        server.connectUser(jeanMichel);
        david.executeCommand("broadcast message1");
        jeanMichel.executeCommand("kick david");
        david.executeCommand("kick jean-michel");
        david.executeCommand("set_username jean");
        david.executeCommand("broadcast message2");
    }
}

User connected: david
User connected: jean-michel
Message sent by david to david: message1
Message sent by david to jean-michel: message1
User disconnected: jean-michel
Message sent by jean to jean: message2

User jeanMichel = new User("jean-michel");
jeanMichel.addCommand(new SetUsernameCommand()); 
jeanMichel.addCommand(new BroadcastCommand());

User jeanMichel = new UserBuilder().setName("jean-michel").build();

User david = new UserBuilder().setName("david").enableAdminCommands().build();