HW-10-Socket-Programming/src/main/java/com/university/chat/Server/ClientSession.java

package com.university.chat.Server;

import com.university.chat.Common.ChatMessage;
import com.university.chat.Common.FileMessage;
import com.university.chat.Common.MessageType;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.Socket;
import java.nio.file.Files;

public class ClientSession implements Runnable {

    private final Socket socket;
    private final UserManager userManager;
    private ObjectOutputStream out;
    private ObjectInputStream in;

    private String username;

    public ClientSession(Socket socket, UserManager userManager) {
        // TODO : Create an ObjectOutputStream from socket.getOutputStream()
        //         and an ObjectInputStream from socket.getInputStream().
        this.socket = socket;
        this.userManager = userManager;
        try {
            this.out = new ObjectOutputStream(socket.getOutputStream());
            this.in = new ObjectInputStream(socket.getInputStream());
        } catch (IOException e) {
            System.out.println("Failed to open streams: " + e.getMessage());
        }
    }

    @Override
    public void run() {
        try {

            // TODO: Welcome the user (login step)
            //  1. Read the first object sent by the client.
            //  2. Check it's a ChatMessage with type LOGIN.
            //  3. Extract the username.
            //  4. Try to register the user via userManager.addUser(...).
            //  5. If the username is taken, send back LOGIN_FAILED and close the socket.
            //  6. Otherwise, create the user's folders with FileManager.createUserFolders(...)
            //      and send back LOGIN_SUCCESS.
            Object first = in.readObject();
            if (!(first instanceof ChatMessage loginMsg) || loginMsg.getType() != MessageType.LOGIN) {
                sendMessage(new ChatMessage(MessageType.LOGIN_FAILED, "server", null, "Expected LOGIN message"));
                socket.close();
                return;
            }

            username = loginMsg.getSender();

            if (!userManager.addUser(username, this)) {
                sendMessage(new ChatMessage(MessageType.LOGIN_FAILED, "server", username, "Username already taken"));
                socket.close();
                return;
            }

            FileManager.createUserFolders(username);
            sendMessage(new ChatMessage(MessageType.LOGIN_SUCCESS, "server", username, "Welcome, " + username + "!"));

            // TODO: Main message loop
            //   In a loop, call in.readObject(), you can separate messages by their type:
            //     - if it's a ChatMessage      -> call handleChatMessage(msg)
            //     - if it's a FileMessage      -> call handleFileMessage(fileMsg)
            //   Keep looping until the connection is closed (an exception will be thrown).
            while (true) {
                Object obj = in.readObject();
                if (obj instanceof ChatMessage msg) {
                    handleChatMessage(msg);
                } else if (obj instanceof FileMessage fileMsg) {
                    handleFileMessage(fileMsg);
                }
            }

        } catch (Exception e) {
            System.out.println("Disconnected: " + username);
        } finally {
            // TODO: Remove the user from UserManager so they no longer
            //        receive broadcasts or appear in users list
            if (username != null) {
                userManager.removeUser(username);
            }
            try {
                socket.close();
            } catch (IOException ignored) {
            }
        }
    }

    public synchronized void sendMessage(Object obj) throws IOException {
        out.writeObject(obj);
        out.flush();
    }

    private void handleChatMessage(ChatMessage msg) throws IOException {
        switch (msg.getType()) {
            case PUBLIC_MESSAGE -> {
                // TODO: Broadcast this message to every connected client.
                for (ClientSession session : userManager.getAllSessions()) {
                    session.sendMessage(msg);
                }
            }
            case PRIVATE_MESSAGE -> {
                // TODO: Forward this message to the receiver user.
                ClientSession receiver = userManager.getUser(msg.getReceiver());
                if (receiver != null) {
                    receiver.sendMessage(msg);
                } else {
                    sendMessage(new ChatMessage(MessageType.PRIVATE_MESSAGE, "server", username,
                            "User '" + msg.getReceiver() + "' is not online."));
                }
            }
            case USER_LIST -> {
                // TODO: Reply to the requester with the list of online users.
                sendMessage(new ChatMessage(MessageType.USER_LIST, "server", username, userManager.listUsers()));
            }
            default -> {
            }
        }
    }

    private void handleFileMessage(FileMessage fileMsg) throws IOException {
        // Storing the file
        var sentPath = FileManager.getSentPath(fileMsg.getSender(), fileMsg.getFilename());
        var recvPath = FileManager.getReceivedPath(fileMsg.getReceiver(), fileMsg.getFilename());

        Files.write(sentPath, fileMsg.getData());
        Files.write(recvPath, fileMsg.getData());

        // TODO: Forward the received file-message to the destination user.
        ClientSession receiver = userManager.getUser(fileMsg.getReceiver());
        if (receiver != null) {
            receiver.sendMessage(fileMsg);
        }
    }
}