# Mediator

// 抽象中介者
interface ChatMediator {
    void sendMessage(String msg, User user);
    void addUser(User user);
}

// 具体中介者：聊天室
class ChatRoom implements ChatMediator {
    private List<User> users = new ArrayList<>();

    @Override
    public void addUser(User user) {
        users.add(user);
    }

    @Override
    public void sendMessage(String msg, User sender) {
        for (User user : users) {
            // 不发给自己
            if (user != sender) {
                user.receive(msg, sender.getName());
            }
        }
    }
}

// 抽象同事类
abstract class User {
    protected ChatMediator mediator;
    protected String name;

    public User(ChatMediator mediator, String name) {
        this.mediator = mediator;
        this.name = name;
    }

    public String getName() {
        return name;
    }

    abstract void send(String msg);
    abstract void receive(String msg, String senderName);
}

// 具体同事类
class ChatUser extends User {
    public ChatUser(ChatMediator mediator, String name) {
        super(mediator, name);
    }

    @Override
    void send(String msg) {
        System.out.println(this.name + " 发送: " + msg);
        mediator.sendMessage(msg, this);
    }

    @Override
    void receive(String msg, String senderName) {
        System.out.println(this.name + " 收到来自 " + senderName + " 的消息: " + msg);
    }
}

// 测试类
public class MediatorPatternDemo {
    public static void main(String[] args) {
        ChatMediator chatRoom = new ChatRoom();

        User user1 = new ChatUser(chatRoom, "Alice");
        User user2 = new ChatUser(chatRoom, "Bob");
        User user3 = new ChatUser(chatRoom, "Charlie");

        chatRoom.addUser(user1);
        chatRoom.addUser(user2);
        chatRoom.addUser(user3);

        user1.send("大家好！");
        user2.send("嗨，Alice！");
    }
}