Implemented session tokens for persistent users.

README.md

@@ -10,7 +10,7 @@ This platform will be organized by many independent servers, each of which will
 - [x] Private message between users in a server. **No support for private messaging users outside the context of a server.**
 - [ ] Banning users from the server.
 - [ ] Voice channels.
-- [ ] Persistent users. Connect and disconnect from a server multiple times, while keeping your information intact.
+- [x] Persistent users. Connect and disconnect from a server multiple times, while keeping your information intact.
 
 
 Here's a short demonstration of its current features:

client/pom.xml

@@ -33,6 +33,25 @@
             <artifactId>jna-platform</artifactId>
             <version>5.9.0</version>
         </dependency>
+
+        <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+            <version>2.12.4</version>
+        </dependency>
+        <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-core -->
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-core</artifactId>
+            <version>2.12.4</version>
+        </dependency>
+        <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-annotations -->
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-annotations</artifactId>
+            <version>2.12.4</version>
+        </dependency>
     </dependencies>
 
     <build>

client/src/main/java/module-info.java

@@ -4,4 +4,7 @@ module concord_client {
 	requires com.sun.jna;
 	requires com.sun.jna.platform;
 	requires static lombok;
+	requires com.fasterxml.jackson.databind;
+	requires com.fasterxml.jackson.core;
+	requires com.fasterxml.jackson.annotation;
 }

client/src/main/java/nl/andrewl/concord_client/ConcordClient.java

@@ -1,5 +1,6 @@
 package nl.andrewl.concord_client;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
 import com.googlecode.lanterna.gui2.MultiWindowTextGUI;
 import com.googlecode.lanterna.gui2.Window;
 import com.googlecode.lanterna.gui2.WindowBasedTextGUI;
@@ -23,7 +24,11 @@ import java.io.DataInputStream;
 import java.io.DataOutputStream;
 import java.io.IOException;
 import java.net.Socket;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
 public class ConcordClient implements Runnable {
 	private final Socket socket;
@@ -38,13 +43,13 @@ public class ConcordClient implements Runnable {
 
 	private volatile boolean running;
 
-	public ConcordClient(String host, int port, String nickname) throws IOException {
+	public ConcordClient(String host, int port, String nickname, Path tokensFile) throws IOException {
 		this.eventManager = new EventManager(this);
 		this.socket = new Socket(host, port);
 		this.in = new DataInputStream(this.socket.getInputStream());
 		this.out = new DataOutputStream(this.socket.getOutputStream());
 		this.serializer = new Serializer();
-		this.model = this.initializeConnectionToServer(nickname);
+		this.model = this.initializeConnectionToServer(nickname, tokensFile);
 
 		// Add event listeners.
 		this.eventManager.addHandler(MoveToChannel.class, new ChannelMovedHandler());
@@ -61,16 +66,19 @@ public class ConcordClient implements Runnable {
 	 * placed in by the server.
 	 * @param nickname The nickname to send to the server that it should know
 	 *                 us by.
+	 * @param tokensFile Path to the file where session tokens are stored.
 	 * @return The client model that contains the server's metadata and other
 	 * information that should be kept up-to-date at runtime.
 	 * @throws IOException If an error occurs while reading or writing the
 	 * messages, or if the server sends an unexpected response.
 	 */
-	private ClientModel initializeConnectionToServer(String nickname) throws IOException {
-		this.serializer.writeMessage(new Identification(nickname), this.out);
+	private ClientModel initializeConnectionToServer(String nickname, Path tokensFile) throws IOException {
+		String token = this.getSessionToken(tokensFile);
+		this.serializer.writeMessage(new Identification(nickname, token), this.out);
 		Message reply = this.serializer.readMessage(this.in);
 		if (reply instanceof ServerWelcome welcome) {
 			var model = new ClientModel(welcome.getClientId(), nickname, welcome.getCurrentChannelId(), welcome.getCurrentChannelName(), welcome.getMetaData());
+			this.saveSessionToken(welcome.getSessionToken(), tokensFile);
 			// Start fetching initial data for the channel we were initially put into.
 			this.sendMessage(new ChatHistoryRequest(model.getCurrentChannelId(), ""));
 			return model;
@@ -117,6 +125,44 @@ public class ConcordClient implements Runnable {
 		}
 	}
 
+	/**
+	 * Fetches the session token that this client should use for its currently
+	 * configured server, according to the socket address and port.
+	 * @param tokensFile The file containing the session tokens.
+	 * @return The session token, or null if none was found.
+	 * @throws IOException If the tokens file could not be read.
+	 */
+	@SuppressWarnings("unchecked")
+	private String getSessionToken(Path tokensFile) throws IOException {
+		String token = null;
+		String address = this.socket.getInetAddress().getHostName() + ":" + this.socket.getPort();
+		if (Files.exists(tokensFile)) {
+			ObjectMapper mapper = new ObjectMapper();
+			Map<String, String> sessionTokens = mapper.readValue(Files.newBufferedReader(tokensFile), Map.class);
+			token = sessionTokens.get(address);
+		}
+		return token;
+	}
+
+	/**
+	 * Saves a session token that this client should use the next time it
+	 * connects to the same server.
+	 * @param token The token to save.
+	 * @param tokensFile The file containing the session tokens.
+	 * @throws IOException If the tokens file could not be read or written to.
+	 */
+	@SuppressWarnings("unchecked")
+	private void saveSessionToken(String token, Path tokensFile) throws IOException {
+		String address = this.socket.getInetAddress().getHostName() + ":" + this.socket.getPort();
+		Map<String, String> tokens = new HashMap<>();
+		ObjectMapper mapper = new ObjectMapper();
+		if (Files.exists(tokensFile)) {
+			tokens = mapper.readValue(Files.newBufferedReader(tokensFile), Map.class);
+		}
+		tokens.put(address, token);
+		mapper.writerWithDefaultPrettyPrinter().writeValue(Files.newBufferedWriter(tokensFile), tokens);
+	}
+
 
 
 	public static void main(String[] args) throws IOException {

client/src/main/java/nl/andrewl/concord_client/gui/MainWindow.java

@@ -6,6 +6,7 @@ import com.googlecode.lanterna.input.KeyStroke;
 import nl.andrewl.concord_client.ConcordClient;
 
 import java.io.IOException;
+import java.nio.file.Path;
 import java.util.concurrent.atomic.AtomicBoolean;
 
 public class MainWindow extends BasicWindow {
@@ -49,7 +50,7 @@ public class MainWindow extends BasicWindow {
 		if (nickname == null) return;
 
 		try {
-			var client = new ConcordClient(host, port, nickname);
+			var client = new ConcordClient(host, port, nickname, Path.of("concord-session-tokens.json"));
 			var chatPanel = new ServerPanel(client, this);
 			client.getModel().addListener(chatPanel);
 			new Thread(client).start();

core/src/main/java/nl/andrewl/concord_core/msg/types/Identification.java

@@ -1,39 +1,56 @@
 package nl.andrewl.concord_core.msg.types;
 
+import lombok.AllArgsConstructor;
 import lombok.Data;
 import lombok.NoArgsConstructor;
 import nl.andrewl.concord_core.msg.Message;
-import nl.andrewl.concord_core.msg.MessageUtils;
 
 import java.io.DataInputStream;
 import java.io.DataOutputStream;
 import java.io.IOException;
 
+import static nl.andrewl.concord_core.msg.MessageUtils.*;
+
 /**
  * This message is sent from the client to a server, to provide identification
  * information about the client to the server when the connection is started.
  */
 @Data
+@AllArgsConstructor
 @NoArgsConstructor
 public class Identification implements Message {
+	/**
+	 * The nickname that a client wants to be identified by when in the server.
+	 * If a valid session token is provided, this can be left as null, and the
+	 * user will be given the same nickname they had in their previous session.
+	 */
 	private String nickname;
 
+	/**
+	 * A session token that's used to uniquely identify this client as the same
+	 * as one who has previously connected to the server. If this is null, the
+	 * client is indicating that they have not connected to this server before.
+	 */
+	private String sessionToken;
+
 	public Identification(String nickname) {
 		this.nickname = nickname;
 	}
 
 	@Override
 	public int getByteCount() {
-		return MessageUtils.getByteSize(this.nickname);
+		return getByteSize(this.nickname) + getByteSize(sessionToken);
 	}
 
 	@Override
 	public void write(DataOutputStream o) throws IOException {
-		MessageUtils.writeString(this.nickname, o);
+		writeString(this.nickname, o);
+		writeString(this.sessionToken, o);
 	}
 
 	@Override
 	public void read(DataInputStream i) throws IOException {
-		this.nickname = MessageUtils.readString(i);
+		this.nickname = readString(i);
+		this.sessionToken = readString(i);
 	}
 }

core/src/main/java/nl/andrewl/concord_core/msg/types/ServerWelcome.java

@@ -20,19 +20,41 @@ import static nl.andrewl.concord_core.msg.MessageUtils.*;
 @NoArgsConstructor
 @AllArgsConstructor
 public class ServerWelcome implements Message {
+	/**
+	 * The unique id of this client.
+	 */
 	private UUID clientId;
+
+	/**
+	 * The token which this client can use to reconnect to the server later and
+	 * still be recognized as the same user.
+	 */
+	private String sessionToken;
+
+	/**
+	 * The id of the channel that the user has been placed in.
+	 */
 	private UUID currentChannelId;
+
+	/**
+	 * The name of the channel that the user has been placed in.
+	 */
 	private String currentChannelName;
+
+	/**
+	 * Information about the server's structure.
+	 */
 	private ServerMetaData metaData;
 
 	@Override
 	public int getByteCount() {
-		return 2 * UUID_BYTES + getByteSize(this.currentChannelName) + this.metaData.getByteCount();
+		return 2 * UUID_BYTES + getByteSize(this.sessionToken) + getByteSize(this.currentChannelName) + this.metaData.getByteCount();
 	}
 
 	@Override
 	public void write(DataOutputStream o) throws IOException {
 		writeUUID(this.clientId, o);
+		writeString(this.sessionToken, o);
 		writeUUID(this.currentChannelId, o);
 		writeString(this.currentChannelName, o);
 		this.metaData.write(o);
@@ -41,6 +63,7 @@ public class ServerWelcome implements Message {
 	@Override
 	public void read(DataInputStream i) throws IOException {
 		this.clientId = readUUID(i);
+		this.sessionToken = readString(i);
 		this.currentChannelId = readUUID(i);
 		this.metaData = new ServerMetaData();
 		this.currentChannelName = readString(i);

server/src/main/java/nl/andrewl/concord_server/channel/Channel.java

@@ -49,31 +49,19 @@ public class Channel {
 	}
 
 	/**
-	 * Adds a client to this channel. Also sends an update to all clients,
-	 * including the new one, telling them that a user has joined.
+	 * Adds a client to this channel.
 	 * @param clientThread The client to add.
 	 */
 	public void addClient(ClientThread clientThread) {
 		this.connectedClients.add(clientThread);
-//		try {
-//			this.sendMessage(new ChannelUsersResponse(this.getUserData()));
-//		} catch (IOException e) {
-//			e.printStackTrace();
-//		}
 	}
 
 	/**
-	 * Removes a client from this channel. Also sends an update to all the
-	 * clients that are still connected, telling them that a user has left.
+	 * Removes a client from this channel.
 	 * @param clientThread The client to remove.
 	 */
 	public void removeClient(ClientThread clientThread) {
 		this.connectedClients.remove(clientThread);
-//		try {
-//			this.sendMessage(new ChannelUsersResponse(this.getUserData()));
-//		} catch (IOException e) {
-//			e.printStackTrace();
-//		}
 	}
 
 	/**

server/src/main/java/nl/andrewl/concord_server/client/ClientManager.java

@@ -1,11 +1,15 @@
 package nl.andrewl.concord_server.client;
 
 import nl.andrewl.concord_core.msg.Message;
-import nl.andrewl.concord_core.msg.types.Identification;
-import nl.andrewl.concord_core.msg.types.ServerUsers;
-import nl.andrewl.concord_core.msg.types.ServerWelcome;
-import nl.andrewl.concord_core.msg.types.UserData;
+import nl.andrewl.concord_core.msg.types.Error;
+import nl.andrewl.concord_core.msg.types.*;
 import nl.andrewl.concord_server.ConcordServer;
+import nl.andrewl.concord_server.util.CollectionUtils;
+import nl.andrewl.concord_server.util.StringUtils;
+import org.dizitart.no2.Document;
+import org.dizitart.no2.IndexType;
+import org.dizitart.no2.NitriteCollection;
+import org.dizitart.no2.filters.Filters;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
@@ -20,10 +24,17 @@ import java.util.stream.Collectors;
 public class ClientManager {
 	private final ConcordServer server;
 	private final Map<UUID, ClientThread> clients;
+	private final NitriteCollection userCollection;
 
 	public ClientManager(ConcordServer server) {
 		this.server = server;
 		this.clients = new ConcurrentHashMap<>();
+		this.userCollection = server.getDb().getCollection("users");
+		CollectionUtils.ensureIndexes(this.userCollection, Map.of(
+				"id", IndexType.Unique,
+				"sessionToken", IndexType.Unique,
+				"nickname", IndexType.Fulltext
+		));
 	}
 
 	/**
@@ -36,18 +47,29 @@ public class ClientManager {
 	 * @param clientThread The client manager thread.
 	 */
 	public void registerClient(Identification identification, ClientThread clientThread) {
-		var id = this.server.getIdProvider().newId();
-		System.out.printf("Client \"%s\" joined with id %s.\n", identification.getNickname(), id);
-		this.clients.put(id, clientThread);
-		clientThread.setClientId(id);
-		clientThread.setClientNickname(identification.getNickname());
-		// Immediately add the client to the default channel and send the initial welcome message.
+		ClientConnectionData data;
+		try {
+			data = identification.getSessionToken() == null ? getNewClientData(identification) : getClientDataFromDb(identification);
+		} catch (InvalidIdentificationException e) {
+			clientThread.sendToClient(Error.warning(e.getMessage()));
+			return;
+		}
+
+		this.clients.put(data.id, clientThread);
+		clientThread.setClientId(data.id);
+		clientThread.setClientNickname(data.nickname);
 		var defaultChannel = this.server.getChannelManager().getDefaultChannel().orElseThrow();
-		clientThread.sendToClient(new ServerWelcome(id, defaultChannel.getId(), defaultChannel.getName(), this.server.getMetaData()));
+		clientThread.sendToClient(new ServerWelcome(data.id, data.sessionToken, defaultChannel.getId(), defaultChannel.getName(), this.server.getMetaData()));
 		// It is important that we send the welcome message first. The client expects this as the initial response to their identification message.
 		defaultChannel.addClient(clientThread);
 		clientThread.setCurrentChannel(defaultChannel);
-		System.out.println("Moved client " + clientThread + " to " + defaultChannel);
+		System.out.printf(
+				"Client %s(%s) joined%s, and was put into %s.\n",
+				data.nickname,
+				data.id,
+				data.newClient ? " for the first time" : "",
+				defaultChannel
+		);
 		this.broadcast(new ServerUsers(this.getClients()));
 	}
 
@@ -98,4 +120,43 @@ public class ClientManager {
 	public Optional<ClientThread> getClientById(UUID id) {
 		return Optional.ofNullable(this.clients.get(id));
 	}
+
+	private static record ClientConnectionData(UUID id, String nickname, String sessionToken, boolean newClient) {}
+
+	private ClientConnectionData getClientDataFromDb(Identification identification) throws InvalidIdentificationException {
+		var cursor = this.userCollection.find(Filters.eq("sessionToken", identification.getSessionToken()));
+		Document doc = cursor.firstOrDefault();
+		if (doc != null) {
+			UUID id = doc.get("id", UUID.class);
+			String nickname = identification.getNickname();
+			if (nickname != null) {
+				doc.put("nickname", nickname);
+			} else {
+				nickname = doc.get("nickname", String.class);
+			}
+			String sessionToken = StringUtils.random(128);
+			doc.put("sessionToken", sessionToken);
+			this.userCollection.update(doc);
+			return new ClientConnectionData(id, nickname, sessionToken, false);
+		} else {
+			throw new InvalidIdentificationException("Invalid session token.");
+		}
+	}
+
+	private ClientConnectionData getNewClientData(Identification identification) throws InvalidIdentificationException {
+		UUID id = this.server.getIdProvider().newId();
+		String nickname = identification.getNickname();
+		if (nickname == null) {
+			throw new InvalidIdentificationException("Missing nickname.");
+		}
+		String sessionToken = StringUtils.random(128);
+		Document doc = new Document(Map.of(
+				"id", id,
+				"nickname", nickname,
+				"sessionToken", sessionToken,
+				"createdAt", System.currentTimeMillis()
+		));
+		this.userCollection.insert(doc);
+		return new ClientConnectionData(id, nickname, sessionToken, true);
+	}
 }

server/src/main/java/nl/andrewl/concord_server/client/InvalidIdentificationException.java

@@ -0,0 +1,10 @@
+package nl.andrewl.concord_server.client;
+
+/**
+ * Exception that's thrown when a client's identification information is invalid.
+ */
+public class InvalidIdentificationException extends Exception {
+	public InvalidIdentificationException(String message) {
+		super(message);
+	}
+}

server/src/main/java/nl/andrewl/concord_server/util/Pair.java

@@ -0,0 +1,3 @@
+package nl.andrewl.concord_server.util;
+
+public record Pair<A, B>(A first, B second) {}

server/src/main/java/nl/andrewl/concord_server/util/StringUtils.java

@@ -0,0 +1,17 @@
+package nl.andrewl.concord_server.util;
+
+import java.security.SecureRandom;
+import java.util.Random;
+
+public class StringUtils {
+
+	public static String random(int length) {
+		Random random = new SecureRandom();
+		final String alphabet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_-=+[]{}()<>";
+		StringBuilder sb = new StringBuilder(length);
+		for (int i = 0; i < length; i++) {
+			sb.append(alphabet.charAt(random.nextInt(alphabet.length())));
+		}
+		return sb.toString();
+	}
+}