Add base files

src/main/java/com/university/chat/Client/ServerListener.java

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+package com.university.chat.Client;
+
+public class ServerListener implements Runnable{
+    // TODO: store the ObjectInputStream from the user socket
+    //          (this should be the same input stream the
+    //           chatClient created when connecting)
+
+    @Override
+    public void run() {
+        try {
+            // TODO: In an infinite loop read objects from the server
+            //   - if it's a ChatMessage  -> print "<sender>: <content>"
+            //   - if it's a FileMessage  -> print that a file was received
+            //                               (filename + sender), it's already
+            //                               saved to disk by the server.
+        } catch (Exception e){
+            System.out.println("Disconnected from server");
+        }
+    }
+}

src/main/java/com/university/chat/Client/TransferProgress.java

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+package com.university.chat.Client;
+
+public class TransferProgress {
+
+    private final long total;
+    private final long startTime;
+    private static final int WIDTH = 30;
+
+    public TransferProgress(long total) {
+        this.total = total;
+        this.startTime = System.currentTimeMillis();
+    }
+
+    public void update(long current) {
+
+        double percent = (double) current / total;
+        int filled = (int) (percent * WIDTH);
+
+        StringBuilder bar = new StringBuilder("[");
+        for (int i = 0; i < WIDTH; i++) {
+            bar.append(i < filled ? "█" : " ");
+        }
+        bar.append("]");
+
+        long elapsed = System.currentTimeMillis() - startTime;
+        double speed = current / 1024.0 / 1024.0 / (elapsed / 1000.0 + 0.001);
+
+        System.out.printf("\r%s %3d%% | %.2f MB/s",
+                bar,
+                (int) (percent * 100),
+                speed);
+
+        if (current >= total) {
+            System.out.println();
+        }
+    }
+}

src/main/java/com/university/chat/Client/chatClient.java

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+package com.university.chat.Client;
+
+public class chatClient {
+    public static void main() {
+        // TODO: Connecting to the server
+        //  1. Create a socket and connect to the server
+        //  2. Create an ObjectOutputStream (out) and ObjectInputStream (in)
+        //      from the socket's streams — output FIRST, then input.
+        //  2. Get the username, and send a LOGIN ChatMessage with that username
+        //  3. Start a new Thread running a ServerListener(in) so incoming
+        //      messages are handled concurrently.
+
+        while (true){
+            try {
+                // TODO: Program loop — read a line from the console and act on it:
+                //   - "/msg <user> <text>"        -> build & send a PRIVATE_MESSAGE
+                //   - "/users"                    -> build & send a USER_LIST request
+                //   - "/sendfile <user> <path>"   -> read the file into a byte[]
+                //                                     (you can use TransferProgress
+                //                                     to show progress)
+                //                                     and send it as a FileMessage
+                //   - anything else               -> send a PUBLIC_MESSAGE
+                //   Remember to flush() the output stream after writeObject().
+            } catch (Exception e){
+                System.out.println("command failed: " + e.getMessage());
+            }
+        }
+    }
+}

src/main/java/com/university/chat/Common/ChatMessage.java

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+package com.university.chat.Common;
+
+import java.io.Serializable;
+
+public class ChatMessage implements Serializable {
+
+    private static final long serialVersionUID = 1L;
+
+    private MessageType type;
+    private String sender;
+    private String receiver;
+    private String content;
+
+    public ChatMessage(MessageType type, String sender, String receiver, String content) {
+        this.type = type;
+        this.sender = sender;
+        this.receiver = receiver;
+        this.content = content;
+    }
+
+    public MessageType getType() { return type; }
+    public String getSender() { return sender; }
+    public String getReceiver() { return receiver; }
+    public String getContent() { return content; }
+}

src/main/java/com/university/chat/Common/FileMessage.java

@@ -0,0 +1,36 @@
+package com.university.chat.Common;
+
+import java.io.Serializable;
+
+public class FileMessage implements Serializable {
+
+    private static final long SerialVersionUID = 1L;
+
+    private String sender;
+    private String receiver;
+    private String filename;
+    private byte[] data;
+
+    public FileMessage(String sender, String receiver, String filename, byte[] data) {
+        this.sender = sender;
+        this.receiver = receiver;
+        this.filename = filename;
+        this.data = data;
+    }
+
+    public String getSender() {
+        return sender;
+    }
+
+    public String getReceiver() {
+        return receiver;
+    }
+
+    public String getFilename() {
+        return filename;
+    }
+
+    public byte[] getData() {
+        return data;
+    }
+}

src/main/java/com/university/chat/Common/MessageType.java

@@ -0,0 +1,13 @@
+package com.university.chat.Common;
+
+import java.io.Serializable;
+
+public enum MessageType implements Serializable {
+    LOGIN,
+    LOGIN_SUCCESS,
+    LOGIN_FAILED,
+    PUBLIC_MESSAGE,
+    PRIVATE_MESSAGE,
+    USER_LIST,
+    FILE_TRANSFER
+}

src/main/java/com/university/chat/Server/ChatServer.java

@@ -0,0 +1,15 @@
+package com.university.chat.Server;
+
+public class ChatServer {
+    // TODO: declare a single shared UserManager instance (static final)
+    //         This MUST be shared by all ClientSession threads so that
+    //         broadcasting and private messaging work correctly.
+
+    public static void main(String[] args) {
+        // TODO: Create a ServerSocket
+
+        // TODO: In an infinite loop:
+        //  accept an incoming client connection
+        //  make a new thread running ClientSession for each user.
+    }
+}

src/main/java/com/university/chat/Server/ClientSession.java

@@ -0,0 +1,71 @@
+package com.university.chat.Server;
+
+import com.university.chat.Common.ChatMessage;
+import com.university.chat.Common.FileMessage;
+
+import java.io.IOException;
+import java.net.Socket;
+import java.nio.file.Files;
+
+public class ClientSession implements Runnable {
+
+    private String username;
+
+    public ClientSession(Socket socket, UserManager userManager) {
+        // TODO : Create an ObjectOutputStream from socket.getOutputStream()
+        //         and an ObjectInputStream from socket.getInputStream().
+    }
+
+    @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.
+
+            // 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).
+
+        } 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
+        }
+    }
+
+
+    private void handleChatMessage(ChatMessage msg) throws IOException {
+        switch (msg.getType()) {
+            case PUBLIC_MESSAGE -> {
+                // TODO: Broadcast this message to every connected client.
+            }
+            case PRIVATE_MESSAGE -> {
+                // TODO: Forward this message to the receiver user.
+            }
+            case USER_LIST -> {
+                // TODO: Reply to the requester with the list of online users.
+            }
+        }
+    }
+
+    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.
+    }
+}

src/main/java/com/university/chat/Server/FileManager.java

@@ -0,0 +1,25 @@
+package com.university.chat.Server;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+public class FileManager {
+
+    private static final String BASE_DIR = "server_data";
+
+    public static void createUserFolders(String username) throws IOException {
+        Path userPath = Paths.get(BASE_DIR, username);
+        Files.createDirectories(userPath.resolve("received"));
+        Files.createDirectories(userPath.resolve("sent"));
+    }
+
+    public static Path getReceivedPath(String username, String filename) {
+        return Paths.get(BASE_DIR, username, "received", filename);
+    }
+
+    public static Path getSentPath(String username, String filename) {
+        return Paths.get(BASE_DIR, username, "sent", filename);
+    }
+}

src/main/java/com/university/chat/Server/UserManager.java

@@ -0,0 +1,28 @@
+package com.university.chat.Server;
+
+import java.util.concurrent.ConcurrentHashMap;
+
+public class UserManager {
+
+    private final ConcurrentHashMap<String, ClientSession> users = new ConcurrentHashMap<>();
+
+    public boolean addUser(String username, ClientSession session) {
+        return users.putIfAbsent(username, session) == null;
+    }
+
+    public void removeUser(String username) {
+        users.remove(username);
+    }
+
+    public ClientSession getUser(String username) {
+        return users.get(username);
+    }
+
+    public String listUsers() {
+        return users.keySet().toString();
+    }
+
+    public Iterable<ClientSession> getAllSessions() {
+        return users.values();
+    }
+}