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;

import static com.university.chat.Client.chatClient.userManager;

public class ClientSession implements Runnable {

    private String username;
    private final Socket socket;
    private final UserManager userManager;

    private ObjectInputStream in;
    private ObjectOutputStream out;

    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 {
            out = new ObjectOutputStream(socket.getOutputStream());
            out.flush();

            in = new ObjectInputStream(socket.getInputStream());
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    @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 msg)
                    || msg.getType() != MessageType.LOGIN) {

                socket.close();
                return;
            }
            username = msg.getSender();
            if (!userManager.addUser(username, this)) {

                send(new ChatMessage(
                        MessageType.LOGIN_FAILED,
                        "SERVER",
                        username,
                        "Username already exists"
                ));

                socket.close();
                return;
            }
            FileManager.createUserFolders(username);

            send(new ChatMessage(
                    MessageType.LOGIN_SUCCESS,
                    "SERVER",
                    username,
                    "Login successful"
            ));

            // 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 mesg){
                    handleChatMessage(mesg);
                }

                else if(obj instanceof FileMessage file){
                    handleFileMessage(file);
                }
            }

        } 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) {
            }
        }
    }


    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.send(msg);
                }
            }
            case PRIVATE_MESSAGE -> {
                ClientSession target =
                        userManager.getUser(msg.getReceiver());

                if(target != null){
                    target.send(msg);
                }
            }
            case USER_LIST -> {
                // TODO: Reply to the requester with the list of online users.
                send(new ChatMessage(
                        MessageType.USER_LIST,
                        "SERVER",
                        username,
                        userManager.listUsers()
                ));
            }
        }
    }

    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 target =
                userManager.getUser(
                        fileMsg.getReceiver()
                );

        if(target != null){
            target.send(fileMsg);
        }
    }

    public synchronized void send(Object obj)
            throws IOException {

        out.writeObject(obj);
        out.flush();
    }
}