Implemented storing user messages in collections, improved network organization.

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

@@ -11,12 +11,8 @@ import lombok.Getter;
 import lombok.Setter;
 import nl.andrewl.concord_client.gui.MainWindow;
 import nl.andrewl.concord_core.msg.Message;
-import nl.andrewl.concord_core.msg.MessageUtils;
 import nl.andrewl.concord_core.msg.Serializer;
-import nl.andrewl.concord_core.msg.types.Chat;
+import nl.andrewl.concord_core.msg.types.*;
-import nl.andrewl.concord_core.msg.types.Identification;
-import nl.andrewl.concord_core.msg.types.ServerMetaData;
-import nl.andrewl.concord_core.msg.types.ServerWelcome;
 
 import java.io.DataInputStream;
 import java.io.DataOutputStream;
@@ -28,7 +24,6 @@ import java.util.Set;
 import java.util.UUID;
 
 public class ConcordClient implements Runnable {
-
 	private final Socket socket;
 	private final DataInputStream in;
 	private final DataOutputStream out;
@@ -53,6 +48,10 @@ public class ConcordClient implements Runnable {
 			this.id = welcome.getClientId();
 			this.currentChannelId = welcome.getCurrentChannelId();
 			this.serverMetaData = welcome.getMetaData();
+
+			// Start fetching initial data for the channel we were initially put into.
+			this.sendMessage(new ChannelUsersRequest(this.currentChannelId));
+			this.sendMessage(new ChatHistoryRequest(this.currentChannelId, ChatHistoryRequest.Source.CHANNEL, ""));
 		} else {
 			throw new IOException("Unexpected response from the server after sending identification message.");
 		}

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

@@ -10,11 +10,17 @@ import nl.andrewl.concord_client.ConcordClient;
 import java.io.IOException;
 import java.util.concurrent.atomic.AtomicBoolean;
 
+/**
+ * This panel occupies the center of the interface, and displays the list of
+ * recent messages, along with an input text box for the user to type messages
+ * into.
+ */
 public class ChannelChatBox extends Panel {
 	private final ConcordClient client;
 	private Border chatBorder;
 	@Getter
 	private final ChatList chatList;
+	@Getter
 	private final TextBox inputTextBox;
 	public ChannelChatBox(ConcordClient client, Window window) {
 		super(new BorderLayout());

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

@@ -1,9 +1,6 @@
 package nl.andrewl.concord_client.gui;
 
-import com.googlecode.lanterna.gui2.Button;
+import com.googlecode.lanterna.gui2.*;
-import com.googlecode.lanterna.gui2.Direction;
-import com.googlecode.lanterna.gui2.LinearLayout;
-import com.googlecode.lanterna.gui2.Panel;
 import nl.andrewl.concord_client.ConcordClient;
 import nl.andrewl.concord_core.msg.types.MoveToChannel;
 
@@ -11,7 +8,6 @@ import java.io.IOException;
 
 public class ChannelList extends Panel {
 	private final ConcordClient client;
-
 	public ChannelList(ConcordClient client) {
 		super(new LinearLayout(Direction.VERTICAL));
 		this.client = client;
@@ -25,11 +21,12 @@ public class ChannelList extends Panel {
 				name = "*" + name;
 			}
 			Button b = new Button(name, () -> {
-				System.out.println("Sending request to go to channel " + channel.getName());
+				if (!client.getCurrentChannelId().equals(channel.getId())) {
-				try {
+					try {
-					client.sendMessage(new MoveToChannel(channel.getId()));
+						client.sendMessage(new MoveToChannel(channel.getId()));
-				} catch (IOException e) {
+					} catch (IOException e) {
-					e.printStackTrace();
+						e.printStackTrace();
+					}
 				}
 			});
 			this.addComponent(b, LinearLayout.createLayoutData(LinearLayout.Alignment.End));

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

@@ -5,8 +5,7 @@ import lombok.Getter;
 import nl.andrewl.concord_client.ClientMessageListener;
 import nl.andrewl.concord_client.ConcordClient;
 import nl.andrewl.concord_core.msg.Message;
-import nl.andrewl.concord_core.msg.types.Chat;
+import nl.andrewl.concord_core.msg.types.*;
-import nl.andrewl.concord_core.msg.types.MoveToChannel;
 
 import java.io.IOException;
 
@@ -24,16 +23,16 @@ public class ChatPanel extends Panel implements ClientMessageListener {
 	private final UserList userList;
 
 	private final ConcordClient client;
+	private final TextGUIThread guiThread;
 
 	public ChatPanel(ConcordClient client, Window window) {
 		super(new BorderLayout());
+		this.guiThread = window.getTextGUI().getGUIThread();
 		this.client = client;
 		this.channelChatBox = new ChannelChatBox(client, window);
 		this.channelList = new ChannelList(client);
 		this.channelList.setChannels();
-		this.userList = new UserList();
+		this.userList = new UserList(client);
-		this.userList.addItem("andrew");
-		this.userList.addItem("tester");
 
 		Border b;
 		b = Borders.doubleLine("Channels");
@@ -53,9 +52,25 @@ public class ChatPanel extends Panel implements ClientMessageListener {
 			this.channelChatBox.getChatList().addItem(chat);
 		} else if (message instanceof MoveToChannel moveToChannel) {
 			client.setCurrentChannelId(moveToChannel.getChannelId());
-			this.channelList.setChannels();
+			try {
-			this.channelChatBox.getChatList().clearItems();
+				client.sendMessage(new ChatHistoryRequest(moveToChannel.getChannelId(), ChatHistoryRequest.Source.CHANNEL, ""));
-			this.channelChatBox.refreshBorder();
+				client.sendMessage(new ChannelUsersRequest(moveToChannel.getChannelId()));
+			} catch (IOException e) {
+				e.printStackTrace();
+			}
+			this.guiThread.invokeLater(() -> {
+				this.channelList.setChannels();
+				this.channelChatBox.getChatList().clearItems();
+				this.channelChatBox.refreshBorder();
+				this.channelChatBox.getInputTextBox().takeFocus();
+			});
+		} else if (message instanceof ChannelUsersResponse channelUsersResponse) {
+			this.guiThread.invokeLater(() -> {
+				this.userList.updateUsers(channelUsersResponse);
+			});
+		} else if (message instanceof ChatHistoryResponse chatHistoryResponse) {
+			System.out.println("Got chat history response: " + chatHistoryResponse.getSourceId());
+			System.out.println(chatHistoryResponse.getMessages());
 		}
 	}
 }

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

@@ -1,6 +1,27 @@
 package nl.andrewl.concord_client.gui;
 
-import com.googlecode.lanterna.gui2.AbstractListBox;
+import com.googlecode.lanterna.gui2.Button;
+import com.googlecode.lanterna.gui2.Direction;
+import com.googlecode.lanterna.gui2.LinearLayout;
+import com.googlecode.lanterna.gui2.Panel;
+import nl.andrewl.concord_client.ConcordClient;
+import nl.andrewl.concord_core.msg.types.ChannelUsersResponse;
 
-public class UserList extends AbstractListBox<String, UserList> {
+public class UserList extends Panel {
+	private final ConcordClient client;
+
+	public UserList(ConcordClient client) {
+		super(new LinearLayout(Direction.VERTICAL));
+		this.client = client;
+	}
+
+	public void updateUsers(ChannelUsersResponse usersResponse) {
+		this.removeAllComponents();
+		for (var user : usersResponse.getUsers()) {
+			Button b = new Button(user.getName(), () -> {
+				System.out.println("Opening DM channel with user " + user.getName() + ", id: " + user.getId());
+			});
+			this.addComponent(b);
+		}
+	}
 }

core/src/main/java/nl/andrewl/concord_core/msg/Serializer.java

@@ -19,6 +19,8 @@ public class Serializer {
 		registerType(3, MoveToChannel.class);
 		registerType(4, ChatHistoryRequest.class);
 		registerType(5, ChatHistoryResponse.class);
+		registerType(6, ChannelUsersRequest.class);
+		registerType(7, ChannelUsersResponse.class);
 	}
 
 	private static void registerType(int id, Class<? extends Message> clazz) {

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

@@ -0,0 +1,35 @@
+package nl.andrewl.concord_core.msg.types;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+import nl.andrewl.concord_core.msg.Message;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.util.UUID;
+
+import static nl.andrewl.concord_core.msg.MessageUtils.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class ChannelUsersRequest implements Message {
+	private UUID channelId;
+
+	@Override
+	public int getByteCount() {
+		return UUID_BYTES;
+	}
+
+	@Override
+	public void write(DataOutputStream o) throws IOException {
+		writeUUID(this.channelId, o);
+	}
+
+	@Override
+	public void read(DataInputStream i) throws IOException {
+		this.channelId = readUUID(i);
+	}
+}

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

@@ -0,0 +1,65 @@
+package nl.andrewl.concord_core.msg.types;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+import nl.andrewl.concord_core.msg.Message;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.util.List;
+import java.util.UUID;
+
+import static nl.andrewl.concord_core.msg.MessageUtils.*;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class ChannelUsersResponse implements Message {
+	private List<UserData> users;
+
+	@Override
+	public int getByteCount() {
+		return getByteSize(this.users);
+	}
+
+	@Override
+	public void write(DataOutputStream o) throws IOException {
+		writeList(this.users, o);
+	}
+
+	@Override
+	public void read(DataInputStream i) throws IOException {
+		try {
+			this.users = readList(UserData.class, i);
+		} catch (ReflectiveOperationException e) {
+			throw new IOException(e);
+		}
+	}
+
+	@Data
+	@NoArgsConstructor
+	@AllArgsConstructor
+	public static class UserData implements Message {
+		private UUID id;
+		private String name;
+
+		@Override
+		public int getByteCount() {
+			return UUID_BYTES + getByteSize(this.name);
+		}
+
+		@Override
+		public void write(DataOutputStream o) throws IOException {
+			writeUUID(this.id, o);
+			writeString(this.name, o);
+		}
+
+		@Override
+		public void read(DataInputStream i) throws IOException {
+			this.id = readUUID(i);
+			this.name = readString(i);
+		}
+	}
+}

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

@@ -1,5 +1,6 @@
 package nl.andrewl.concord_core.msg.types;
 
+import lombok.AllArgsConstructor;
 import lombok.Data;
 import lombok.NoArgsConstructor;
 import nl.andrewl.concord_core.msg.Message;
@@ -46,6 +47,7 @@ import static nl.andrewl.concord_core.msg.MessageUtils.*;
  */
 @Data
 @NoArgsConstructor
+@AllArgsConstructor
 public class ChatHistoryRequest implements Message {
 	public enum Source {CHANNEL, THREAD, DIRECT_MESSAGE}
 

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

@@ -1,5 +1,6 @@
 package nl.andrewl.concord_core.msg.types;
 
+import lombok.AllArgsConstructor;
 import lombok.Data;
 import lombok.NoArgsConstructor;
 import nl.andrewl.concord_core.msg.Message;
@@ -17,6 +18,7 @@ import java.util.UUID;
  */
 @Data
 @NoArgsConstructor
+@AllArgsConstructor
 public class ChatHistoryResponse implements Message {
 	private UUID sourceId;
 	private ChatHistoryRequest.Source sourceType;

server/pom.xml

@@ -24,5 +24,24 @@
             <version>3.4.3</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>
 </project>

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

@@ -1,9 +1,14 @@
 module concord_server {
 	requires nitrite;
 	requires static lombok;
+	requires com.fasterxml.jackson.databind;
+	requires com.fasterxml.jackson.core;
+	requires com.fasterxml.jackson.annotation;
 
 	requires java.base;
 	requires java.logging;
 
 	requires concord_core;
+
+	opens nl.andrewl.concord_server.config to com.fasterxml.jackson.databind;
 }

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

@@ -3,12 +3,12 @@ package nl.andrewl.concord_server;
 import lombok.Getter;
 import nl.andrewl.concord_core.msg.Message;
 import nl.andrewl.concord_core.msg.Serializer;
+import nl.andrewl.concord_core.msg.types.ChannelUsersResponse;
+import org.dizitart.no2.NitriteCollection;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.util.Objects;
+import java.util.*;
-import java.util.Set;
-import java.util.UUID;
 import java.util.concurrent.ConcurrentHashMap;
 
 /**
@@ -23,19 +23,32 @@ public class Channel {
 
 	private final Set<ClientThread> connectedClients;
 
-	public Channel(ConcordServer server, UUID id, String name) {
+	private final NitriteCollection messageCollection;
+
+	public Channel(ConcordServer server, UUID id, String name, NitriteCollection messageCollection) {
 		this.server = server;
 		this.id = id;
 		this.name = name;
 		this.connectedClients = ConcurrentHashMap.newKeySet();
+		this.messageCollection = messageCollection;
 	}
 
 	public void addClient(ClientThread clientThread) {
 		this.connectedClients.add(clientThread);
+		try {
+			this.sendMessage(new ChannelUsersResponse(this.getUserData()));
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
 	}
 
 	public void removeClient(ClientThread clientThread) {
 		this.connectedClients.remove(clientThread);
+		try {
+			this.sendMessage(new ChannelUsersResponse(this.getUserData()));
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
 	}
 
 	/**
@@ -53,6 +66,15 @@ public class Channel {
 		}
 	}
 
+	public List<ChannelUsersResponse.UserData> getUserData() {
+		List<ChannelUsersResponse.UserData> users = new ArrayList<>();
+		for (var clientThread : this.getConnectedClients()) {
+			users.add(new ChannelUsersResponse.UserData(clientThread.getClientId(), clientThread.getClientNickname()));
+		}
+		users.sort(Comparator.comparing(ChannelUsersResponse.UserData::getName));
+		return users;
+	}
+
 	@Override
 	public boolean equals(Object o) {
 		if (this == o) return true;

server/src/main/java/nl/andrewl/concord_server/ChannelManager.java

@@ -2,7 +2,10 @@ package nl.andrewl.concord_server;
 
 import nl.andrewl.concord_core.msg.types.MoveToChannel;
 
-import java.util.*;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.UUID;
 import java.util.concurrent.ConcurrentHashMap;
 
 public class ChannelManager {
@@ -14,10 +17,6 @@ public class ChannelManager {
 		this.server = server;
 		this.channelNameMap = new ConcurrentHashMap<>();
 		this.channelIdMap = new ConcurrentHashMap<>();
-		Channel general = new Channel(server, server.getIdProvider().newId(), "general");
-		Channel memes = new Channel(server, server.getIdProvider().newId(), "memes");
-		this.addChannel(general);
-		this.addChannel(memes);
 	}
 
 	public Set<Channel> getChannels() {
@@ -44,7 +43,8 @@ public class ChannelManager {
 
 	public void moveToChannel(ClientThread client, Channel channel) {
 		if (client.getCurrentChannel() != null) {
-			client.getCurrentChannel().removeClient(client);
+			var previousChannel = client.getCurrentChannel();
+			previousChannel.removeClient(client);
 		}
 		channel.addClient(client);
 		client.setCurrentChannel(channel);

server/src/main/java/nl/andrewl/concord_server/ClientThread.java

@@ -6,7 +6,6 @@ import lombok.extern.java.Log;
 import nl.andrewl.concord_core.msg.Message;
 import nl.andrewl.concord_core.msg.Serializer;
 import nl.andrewl.concord_core.msg.types.Identification;
-import nl.andrewl.concord_core.msg.types.ServerWelcome;
 
 import java.io.DataInputStream;
 import java.io.DataOutputStream;
@@ -16,7 +15,7 @@ import java.util.UUID;
 
 /**
  * This thread is responsible for handling the connection to a single client of
- * a server.
+ * a server. The client thread acts as the server's representation of a client.
  */
 @Log
 public class ClientThread extends Thread {
@@ -26,8 +25,11 @@ public class ClientThread extends Thread {
 
 	private final ConcordServer server;
 
+	@Getter
+	@Setter
 	private UUID clientId = null;
 	@Getter
+	@Setter
 	private String clientNickname = null;
 
 	@Getter
@@ -43,7 +45,7 @@ public class ClientThread extends Thread {
 		this.out = new DataOutputStream(socket.getOutputStream());
 	}
 
-	public void sendToClient(Message message) {
+	public synchronized void sendToClient(Message message) {
 		try {
 			Serializer.writeMessage(message, this.out);
 		} catch (IOException e) {
@@ -51,7 +53,7 @@ public class ClientThread extends Thread {
 		}
 	}
 
-	public void sendToClient(byte[] bytes) {
+	public synchronized void sendToClient(byte[] bytes) {
 		try {
 			this.out.write(bytes);
 			this.out.flush();
@@ -112,8 +114,7 @@ public class ClientThread extends Thread {
 			try {
 				var msg = Serializer.readMessage(this.in);
 				if (msg instanceof Identification id) {
-					this.clientNickname = id.getNickname();
+					this.server.registerClient(id, this);
-					this.clientId = this.server.registerClient(id, this);
 					return true;
 				}
 			} catch (IOException e) {

server/src/main/java/nl/andrewl/concord_server/ConcordServer.java

@@ -5,11 +5,15 @@ import lombok.extern.java.Log;
 import nl.andrewl.concord_core.msg.types.Identification;
 import nl.andrewl.concord_core.msg.types.ServerMetaData;
 import nl.andrewl.concord_core.msg.types.ServerWelcome;
+import nl.andrewl.concord_server.config.ServerConfig;
+import org.dizitart.no2.IndexOptions;
+import org.dizitart.no2.IndexType;
 import org.dizitart.no2.Nitrite;
 
 import java.io.IOException;
 import java.net.ServerSocket;
 import java.net.Socket;
+import java.nio.file.Path;
 import java.util.Comparator;
 import java.util.Map;
 import java.util.UUID;
@@ -22,6 +26,7 @@ import java.util.stream.Collectors;
 public class ConcordServer implements Runnable {
 	private final Map<UUID, ClientThread> clients;
 	private final int port;
+	private final String name;
 	@Getter
 	private final IdProvider idProvider;
 	@Getter
@@ -34,9 +39,11 @@ public class ConcordServer implements Runnable {
 	@Getter
 	private final ChannelManager channelManager;
 
-	public ConcordServer(int port) {
+	public ConcordServer() {
-		this.port = port;
 		this.idProvider = new UUIDProvider();
+		ServerConfig config = ServerConfig.loadOrCreate(Path.of("server-config.json"), idProvider);
+		this.port = config.port();
+		this.name = config.name();
 		this.db = Nitrite.builder()
 				.filePath("concord-server.db")
 				.openOrCreate();
@@ -45,6 +52,33 @@ public class ConcordServer implements Runnable {
 		this.executorService = Executors.newCachedThreadPool();
 		this.eventManager = new EventManager(this);
 		this.channelManager = new ChannelManager(this);
+		for (var channelConfig : config.channels()) {
+			this.channelManager.addChannel(new Channel(
+					this,
+					UUID.fromString(channelConfig.id()),
+					channelConfig.name(),
+					this.db.getCollection("channel-" + channelConfig.id())
+			));
+		}
+		this.initDatabase();
+	}
+
+	private void initDatabase() {
+		for (var channel : this.channelManager.getChannels()) {
+			var col = channel.getMessageCollection();
+			if (!col.hasIndex("timestamp")) {
+				log.info("Adding timestamp index to collection for channel " + channel.getName());
+				col.createIndex("timestamp", IndexOptions.indexOptions(IndexType.NonUnique));
+			}
+			if (!col.hasIndex("senderNickname")) {
+				log.info("Adding senderNickname index to collection for channel " + channel.getName());
+				col.createIndex("senderNickname", IndexOptions.indexOptions(IndexType.Fulltext));
+			}
+			if (!col.hasIndex("message")) {
+				log.info("Adding message index to collection for channel " + channel.getName());
+				col.createIndex("message", IndexOptions.indexOptions(IndexType.Fulltext));
+			}
+		}
 	}
 
 	/**
@@ -55,28 +89,34 @@ public class ConcordServer implements Runnable {
 	 * channel.
 	 * @param identification The client's identification data.
 	 * @param clientThread The client manager thread.
-	 * @return The id of the client.
 	 */
-	public UUID registerClient(Identification identification, ClientThread clientThread) {
+	public void registerClient(Identification identification, ClientThread clientThread) {
 		var id = this.idProvider.newId();
 		log.info("Registering new client " + identification.getNickname() + " with id " + id);
 		this.clients.put(id, clientThread);
+		clientThread.setClientId(id);
+		clientThread.setClientNickname(identification.getNickname());
 		// Send a welcome reply containing all the initial server info the client needs.
 		ServerMetaData metaData = new ServerMetaData(
-				"Testing Server",
+				this.name,
 				this.channelManager.getChannels().stream()
 						.map(channel -> new ServerMetaData.ChannelData(channel.getId(), channel.getName()))
 						.sorted(Comparator.comparing(ServerMetaData.ChannelData::getName))
 						.collect(Collectors.toList())
 		);
+		// Immediately add the client to the default channel and send the initial welcome message.
 		var defaultChannel = this.channelManager.getChannelByName("general").orElseThrow();
+		clientThread.sendToClient(new ServerWelcome(id, defaultChannel.getId(), metaData));
+		// 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);
-		clientThread.sendToClient(new ServerWelcome(id, defaultChannel.getId(), metaData));
-
-		return id;
 	}
 
+	/**
+	 * De-registers a client from the server, removing them from any channel
+	 * they're currently in.
+	 * @param clientId The id of the client to remove.
+	 */
 	public void deregisterClient(UUID clientId) {
 		var client = this.clients.remove(clientId);
 		if (client != null) {
@@ -104,7 +144,7 @@ public class ConcordServer implements Runnable {
 	}
 
 	public static void main(String[] args) {
-		var server = new ConcordServer(8123);
+		var server = new ConcordServer();
 		server.run();
 	}
 }

server/src/main/java/nl/andrewl/concord_server/EventManager.java

@@ -2,15 +2,19 @@ package nl.andrewl.concord_server;
 
 import lombok.extern.java.Log;
 import nl.andrewl.concord_core.msg.Message;
+import nl.andrewl.concord_core.msg.types.ChannelUsersRequest;
 import nl.andrewl.concord_core.msg.types.Chat;
+import nl.andrewl.concord_core.msg.types.ChatHistoryRequest;
 import nl.andrewl.concord_core.msg.types.MoveToChannel;
-import nl.andrewl.concord_server.event.ChannelMoveHandler;
+import nl.andrewl.concord_server.event.*;
-import nl.andrewl.concord_server.event.ChatHandler;
-import nl.andrewl.concord_server.event.MessageHandler;
 
 import java.util.HashMap;
 import java.util.Map;
 
+/**
+ * The event manager is responsible for the server's ability to respond to
+ * various client requests.
+ */
 @Log
 public class EventManager {
 	private final Map<Class<? extends Message>, MessageHandler<?>> messageHandlers;
@@ -21,8 +25,25 @@ public class EventManager {
 		this.messageHandlers = new HashMap<>();
 		this.messageHandlers.put(Chat.class, new ChatHandler());
 		this.messageHandlers.put(MoveToChannel.class, new ChannelMoveHandler());
+		this.messageHandlers.put(ChannelUsersRequest.class, new ChannelUsersRequestHandler());
+		this.messageHandlers.put(ChatHistoryRequest.class, new ChatHistoryRequestHandler());
 	}
 
+	/**
+	 * Handles a new message that was sent from a client. Tries to find an
+	 * appropriate handler for the message, and if one is found, calls the
+	 * {@link MessageHandler#handle(Message, ClientThread, ConcordServer)}
+	 * method on it.
+	 * <p>
+	 *     Note that it is expected that client threads will invoke this method
+	 *     during their {@link ClientThread#run()} method, so concurrent
+	 *     invocation is expected.
+	 * </p>
+	 * @param message The message that was sent by a client.
+	 * @param client The client thread that is used for communicating with the
+	 *               client.
+	 * @param <T> The type of message.
+	 */
 	@SuppressWarnings("unchecked")
 	public <T extends Message> void handle(T message, ClientThread client) {
 		MessageHandler<T> handler = (MessageHandler<T>) this.messageHandlers.get(message.getClass());
@@ -30,6 +51,7 @@ public class EventManager {
 			try {
 				handler.handle(message, client, this.server);
 			} catch (Exception e) {
+				e.printStackTrace();
 				log.warning("Exception occurred while handling message: " + e.getMessage());
 			}
 		}

server/src/main/java/nl/andrewl/concord_server/config/ServerConfig.java

@@ -0,0 +1,52 @@
+package nl.andrewl.concord_server.config;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import lombok.extern.java.Log;
+import nl.andrewl.concord_server.IdProvider;
+
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+@Log
+public record ServerConfig(
+		String name,
+		int port,
+		ChannelConfig[] channels
+) {
+
+	public static record ChannelConfig (
+			String id,
+			String name,
+			String description
+	) {}
+
+	public static ServerConfig loadOrCreate(Path filePath, IdProvider idProvider) {
+		ObjectMapper mapper = new ObjectMapper();
+		ServerConfig config;
+		if (Files.notExists(filePath)) {
+			config = new ServerConfig(
+					"My Concord Server",
+					8123,
+					new ServerConfig.ChannelConfig[]{
+							new ServerConfig.ChannelConfig(idProvider.newId().toString(), "general", "Default channel for general discussion.")
+					}
+			);
+			try (var out = Files.newOutputStream(filePath)) {
+				mapper.writerWithDefaultPrettyPrinter().writeValue(out, config);
+			} catch (IOException e) {
+				throw new UncheckedIOException(e);
+			}
+			log.info(filePath + " does not exist. Creating it with initial values. Edit and restart to apply changes.");
+		} else {
+			try {
+				config = mapper.readValue(Files.newInputStream(filePath), ServerConfig.class);
+			} catch (IOException e) {
+				throw new UncheckedIOException(e);
+			}
+			log.info("Loaded configuration from " + filePath);
+		}
+		return config;
+	}
+}

server/src/main/java/nl/andrewl/concord_server/event/ChannelUsersRequestHandler.java

@@ -0,0 +1,17 @@
+package nl.andrewl.concord_server.event;
+
+import nl.andrewl.concord_core.msg.types.ChannelUsersRequest;
+import nl.andrewl.concord_core.msg.types.ChannelUsersResponse;
+import nl.andrewl.concord_server.ClientThread;
+import nl.andrewl.concord_server.ConcordServer;
+
+public class ChannelUsersRequestHandler implements MessageHandler<ChannelUsersRequest> {
+	@Override
+	public void handle(ChannelUsersRequest msg, ClientThread client, ConcordServer server) throws Exception {
+		var optionalChannel = server.getChannelManager().getChannelById(msg.getChannelId());
+		if (optionalChannel.isPresent()) {
+			var channel = optionalChannel.get();
+			client.sendToClient(new ChannelUsersResponse(channel.getUserData()));
+		}
+	}
+}

server/src/main/java/nl/andrewl/concord_server/event/ChatHandler.java

@@ -12,10 +12,8 @@ public class ChatHandler implements MessageHandler<Chat> {
 	@Override
 	public void handle(Chat msg, ClientThread client, ConcordServer server) throws IOException {
 		server.getExecutorService().submit(() -> {
-			var collection = server.getDb().getCollection("channel-" + client.getCurrentChannel().getId());
+			var collection = client.getCurrentChannel().getMessageCollection();
-			var messageId = server.getIdProvider().newId();
 			Document doc = new Document(Map.of(
-					"_id", messageId,
 					"senderId", msg.getSenderId(),
 					"senderNickname", msg.getSenderNickname(),
 					"timestamp", msg.getTimestamp(),

server/src/main/java/nl/andrewl/concord_server/event/ChatHistoryRequestHandler.java

@@ -0,0 +1,42 @@
+package nl.andrewl.concord_server.event;
+
+import nl.andrewl.concord_core.msg.types.Chat;
+import nl.andrewl.concord_core.msg.types.ChatHistoryRequest;
+import nl.andrewl.concord_core.msg.types.ChatHistoryResponse;
+import nl.andrewl.concord_server.ClientThread;
+import nl.andrewl.concord_server.ConcordServer;
+import org.dizitart.no2.Document;
+import org.dizitart.no2.FindOptions;
+import org.dizitart.no2.SortOrder;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.UUID;
+
+public class ChatHistoryRequestHandler implements MessageHandler<ChatHistoryRequest> {
+	@Override
+	public void handle(ChatHistoryRequest msg, ClientThread client, ConcordServer server) throws Exception {
+		var optionalChannel = server.getChannelManager().getChannelById(msg.getSourceId());
+		if (optionalChannel.isPresent()) {
+			var channel = optionalChannel.get();
+			System.out.println("Looking for chats in channel-" + channel.getId());
+			var col = server.getDb().getCollection("channel-" + channel.getId());
+			var cursor = col.find(
+					FindOptions.sort("timestamp", SortOrder.Ascending)
+						.thenLimit(0, 10)
+			);
+			List<Chat> chats = new ArrayList<>(10);
+			for (Document doc : cursor) {
+				chats.add(new Chat(
+						doc.get("senderId", UUID.class),
+						doc.get("senderNickname", String.class),
+						doc.get("timestamp", Long.class),
+						doc.get("message", String.class)
+				));
+			}
+			col.close();
+			System.out.println(chats);
+			client.sendToClient(new ChatHistoryResponse(msg.getSourceId(), msg.getSourceType(), chats));
+		}
+	}
+}