From 6bbd6936e09bc405ae021a030900de5daf5fb523 Mon Sep 17 00:00:00 2001
From: CyB3RC0nN0R <kske@outlook.de>
Date: Thu, 6 Feb 2020 18:35:05 +0100
Subject: [PATCH 1/7] Replaced MessageCache by Cache<T>

This class will be used to implement the offline cache for both messages
and events.
---
 src/main/java/envoy/client/data/Cache.java    | 58 +++++++++++++++++++
 src/main/java/envoy/client/net/Client.java    |  5 +-
 .../java/envoy/client/net/MessageCache.java   | 54 -----------------
 src/main/java/envoy/client/ui/Startup.java    | 10 ++--
 4 files changed, 65 insertions(+), 62 deletions(-)
 create mode 100644 src/main/java/envoy/client/data/Cache.java
 delete mode 100644 src/main/java/envoy/client/net/MessageCache.java

diff --git a/src/main/java/envoy/client/data/Cache.java b/src/main/java/envoy/client/data/Cache.java
new file mode 100644
index 0000000..366f703
--- /dev/null
+++ b/src/main/java/envoy/client/data/Cache.java
@@ -0,0 +1,58 @@
+package envoy.client.data;
+
+import java.util.LinkedList;
+import java.util.Queue;
+import java.util.function.Consumer;
+import java.util.logging.Logger;
+
+import envoy.client.util.EnvoyLog;
+
+/**
+ * Stores elements in a queue to process them later.<br>
+ * <br>
+ * Project: <strong>envoy-client</strong><br>
+ * File: <strong>Cache.java</strong><br>
+ * Created: <strong>6 Feb 2020</strong><br>
+ *
+ * @param <T> the type of cached elements
+ * @author Kai S. K. Engelbart
+ * @since Envoy v0.3-alpha
+ */
+public class Cache<T> implements Consumer<T> {
+
+	private final Queue<T>	elements	= new LinkedList<>();
+	private Consumer<T>		processor;
+
+	private static final Logger logger = EnvoyLog.getLogger(Cache.class.getSimpleName());
+
+	/**
+	 * Adds an element to the cache.
+	 *
+	 * @param element the element to add
+	 * @since Envoy v0.3-alpha
+	 */
+	@Override
+	public void accept(T element) {
+		logger.info(String.format("Adding element %s to cache", element));
+		elements.offer(element);
+	}
+
+	/**
+	 * Sets the processor to which cached elements are relayed.
+	 *
+	 * @param processor the processor to set
+	 * @since Envoy v0.3-alpha
+	 */
+	public void setProcessor(Consumer<T> processor) { this.processor = processor; }
+
+	/**
+	 * Relays all cached elements to the processor.
+	 *
+	 * @throws IllegalStateException if the processor is not initialized
+	 * @since Envoy v0.3-alpha
+	 */
+	public void relay() {
+		if (processor == null) throw new IllegalStateException("Processor is not defined");
+		elements.forEach(processor::accept);
+	}
+}
diff --git a/src/main/java/envoy/client/net/Client.java b/src/main/java/envoy/client/net/Client.java
index 91e9040..2e96b4a 100644
--- a/src/main/java/envoy/client/net/Client.java
+++ b/src/main/java/envoy/client/net/Client.java
@@ -10,6 +10,7 @@ import java.util.logging.Logger;
 import javax.naming.TimeLimitExceededException;
 
 import envoy.client.Config;
+import envoy.client.data.Cache;
 import envoy.client.data.LocalDb;
 import envoy.client.util.EnvoyLog;
 import envoy.data.*;
@@ -61,7 +62,7 @@ public class Client implements Closeable {
 	 *                   failed for some other reason
 	 * @since Envoy v0.2-alpha
 	 */
-	public MessageCache onlineInit(LoginCredentials credentials, LocalDb localDb) throws Exception {
+	public Cache<Message> onlineInit(LoginCredentials credentials, LocalDb localDb) throws Exception {
 		// Establish TCP connection
 		logger.info(String.format("Attempting connection to server %s:%d...", config.getServer(), config.getPort()));
 		socket = new Socket(config.getServer(), config.getPort());
@@ -71,7 +72,7 @@ public class Client implements Closeable {
 		receiver = new Receiver(socket.getInputStream());
 
 		// Create cache for unread messages
-		final MessageCache cache = new MessageCache();
+		final Cache<Message> cache = new Cache<>();
 
 		// Register user creation processor, contact list processor and message cache
 		receiver.registerProcessor(User.class, sender -> { logger.info("Acquired user object " + sender); this.sender = sender; });
diff --git a/src/main/java/envoy/client/net/MessageCache.java b/src/main/java/envoy/client/net/MessageCache.java
deleted file mode 100644
index 1fc49c3..0000000
--- a/src/main/java/envoy/client/net/MessageCache.java
+++ /dev/null
@@ -1,54 +0,0 @@
-package envoy.client.net;
-
-import java.util.LinkedList;
-import java.util.Queue;
-import java.util.function.Consumer;
-import java.util.logging.Logger;
-
-import envoy.client.util.EnvoyLog;
-import envoy.data.Message;
-
-/**
- * Stores messages in a queue until the application initialization is complete.
- * The messages can then be relayed to a processor.<br>
- * <br>
- * Project: <strong>envoy-client</strong><br>
- * File: <strong>MessageCache.java</strong><br>
- * Created: <strong>4 Feb 2020</strong><br>
- *
- * @author Kai S. K. Engelbart
- * @since Envoy v0.3-alpha
- */
-public class MessageCache implements Consumer<Message> {
-
-	private final Queue<Message>	messages	= new LinkedList<>();
-	private Consumer<Message>		processor;
-
-	private static final Logger logger = EnvoyLog.getLogger(MessageCache.class.getSimpleName());
-
-	/**
-	 * Adds a message to the cache.
-	 *
-	 * @since Envoy v0.3-alpha
-	 */
-	@Override
-	public void accept(Message message) {
-		logger.info(String.format("Adding message %s to cache", message));
-		messages.add(message);
-	}
-
-	/**
-	 * Sets the processor to which messages are relayed.
-	 *
-	 * @param processor the processor to set
-	 * @since Envoy v0.3-alpha
-	 */
-	public void setProcessor(Consumer<Message> processor) { this.processor = processor; }
-
-	/**
-	 * Relays all cached messages to the processor.
-	 *
-	 * @since Envoy v0.3-alpha
-	 */
-	public void relayMessages() { messages.forEach(processor::accept); }
-}
diff --git a/src/main/java/envoy/client/ui/Startup.java b/src/main/java/envoy/client/ui/Startup.java
index 9f308dc..1a38da9 100644
--- a/src/main/java/envoy/client/ui/Startup.java
+++ b/src/main/java/envoy/client/ui/Startup.java
@@ -13,13 +13,11 @@ import javax.swing.SwingUtilities;
 
 import envoy.client.Config;
 import envoy.client.Settings;
-import envoy.client.data.LocalDb;
-import envoy.client.data.PersistentLocalDb;
-import envoy.client.data.TransientLocalDb;
+import envoy.client.data.*;
 import envoy.client.net.Client;
-import envoy.client.net.MessageCache;
 import envoy.client.util.EnvoyLog;
 import envoy.data.LoginCredentials;
+import envoy.data.Message;
 import envoy.data.User;
 import envoy.exception.EnvoyException;
 
@@ -108,7 +106,7 @@ public class Startup {
 		// Acquire the client user (with ID) either from the server or from the local
 		// database, which triggers offline mode
 		Client			client	= new Client();
-		MessageCache	cache	= null;
+		Cache<Message>	cache	= null;
 		try {
 			// Try entering online mode first
 			localDb.loadIdGenerator();
@@ -178,7 +176,7 @@ public class Startup {
 		});
 
 		// Relay unread messages from cache
-		if (cache != null) cache.relayMessages();
+		if (cache != null) cache.relay();
 
 		// Save Settings and PersistentLocalDb on shutdown
 		Runtime.getRuntime().addShutdownHook(new Thread(() -> {

From 0646445d3c4363dbade5faabd70fa50392a5dde0 Mon Sep 17 00:00:00 2001
From: CyB3RC0nN0R <kske@outlook.de>
Date: Thu, 6 Feb 2020 21:03:08 +0100
Subject: [PATCH 2/7] Added WriteProxy with creation method in Client, added
 caches to LocalDb

---
 src/main/java/envoy/client/data/Cache.java    |   5 +-
 src/main/java/envoy/client/data/LocalDb.java  |  36 ++++++-
 .../envoy/client/data/PersistentLocalDb.java  |  14 +--
 src/main/java/envoy/client/net/Client.java    |  11 ++
 .../java/envoy/client/net/WriteProxy.java     | 102 ++++++++++++++++++
 5 files changed, 155 insertions(+), 13 deletions(-)
 create mode 100644 src/main/java/envoy/client/net/WriteProxy.java

diff --git a/src/main/java/envoy/client/data/Cache.java b/src/main/java/envoy/client/data/Cache.java
index 366f703..458cb0a 100644
--- a/src/main/java/envoy/client/data/Cache.java
+++ b/src/main/java/envoy/client/data/Cache.java
@@ -20,8 +20,8 @@ import envoy.client.util.EnvoyLog;
  */
 public class Cache<T> implements Consumer<T> {
 
-	private final Queue<T>	elements	= new LinkedList<>();
-	private Consumer<T>		processor;
+	private final Queue<T>			elements	= new LinkedList<>();
+	private transient Consumer<T>	processor;
 
 	private static final Logger logger = EnvoyLog.getLogger(Cache.class.getSimpleName());
 
@@ -54,5 +54,6 @@ public class Cache<T> implements Consumer<T> {
 	public void relay() {
 		if (processor == null) throw new IllegalStateException("Processor is not defined");
 		elements.forEach(processor::accept);
+		elements.clear();
 	}
 }
diff --git a/src/main/java/envoy/client/data/LocalDb.java b/src/main/java/envoy/client/data/LocalDb.java
index 79368a8..a606856 100644
--- a/src/main/java/envoy/client/data/LocalDb.java
+++ b/src/main/java/envoy/client/data/LocalDb.java
@@ -3,7 +3,9 @@ package envoy.client.data;
 import java.util.*;
 
 import envoy.data.IdGenerator;
+import envoy.data.Message;
 import envoy.data.User;
+import envoy.event.MessageStatusChangeEvent;
 
 /**
  * Stores information about the current {@link User} and their {@link Chat}s.
@@ -18,10 +20,12 @@ import envoy.data.User;
  */
 public abstract class LocalDb {
 
-	protected User				user;
-	protected Map<String, User>	users	= new HashMap<>();
-	protected List<Chat>		chats	= new ArrayList<>();
-	protected IdGenerator		idGenerator;
+	protected User								user;
+	protected Map<String, User>					users	= new HashMap<>();
+	protected List<Chat>						chats	= new ArrayList<>();
+	protected IdGenerator						idGenerator;
+	protected Cache<Message>					messageCache;
+	protected Cache<MessageStatusChangeEvent>	statusCache;
 
 	/**
 	 * Initializes a storage space for a user-specific list of chats.
@@ -115,4 +119,28 @@ public abstract class LocalDb {
 	 * @since Envoy v0.3-alpha
 	 */
 	public boolean hasIdGenerator() { return idGenerator != null; }
+
+	/**
+	 * @return the offline message cache
+	 * @since Envoy v0.3-alpha
+	 */
+	public Cache<Message> getMessageCache() { return messageCache; }
+
+	/**
+	 * @param messageCache the offline message cache to set
+	 * @since Envoy v0.3-alpha
+	 */
+	public void setMessageCache(Cache<Message> messageCache) { this.messageCache = messageCache; }
+
+	/**
+	 * @return the offline status cache
+	 * @since Envoy v0.3-alpha
+	 */
+	public Cache<MessageStatusChangeEvent> getStatusCache() { return statusCache; }
+
+	/**
+	 * @param statusCache the offline status cache to set
+	 * @since Envoy v0.3-alpha
+	 */
+	public void setStatusCache(Cache<MessageStatusChangeEvent> statusCache) { this.statusCache = statusCache; }
 }
diff --git a/src/main/java/envoy/client/data/PersistentLocalDb.java b/src/main/java/envoy/client/data/PersistentLocalDb.java
index 7856517..7052c60 100644
--- a/src/main/java/envoy/client/data/PersistentLocalDb.java
+++ b/src/main/java/envoy/client/data/PersistentLocalDb.java
@@ -40,18 +40,18 @@ public class PersistentLocalDb extends LocalDb {
 	 * Constructs an empty local database. To serialize any chats to the file
 	 * system, call {@link PersistentLocalDb#initializeUserStorage()}.
 	 *
-	 * @param localDBDir the directory in which to store users and chats
+	 * @param localDbDir the directory in which to store users and chats
 	 * @throws IOException if the PersistentLocalDb could not be initialized
 	 * @since Envoy v0.1-alpha
 	 */
-	public PersistentLocalDb(File localDBDir) throws IOException {
-		this.localDBDir = localDBDir;
+	public PersistentLocalDb(File localDbDir) throws IOException {
+		localDBDir = localDbDir;
 
 		// Initialize local database directory
-		if (localDBDir.exists() && !localDBDir.isDirectory())
-			throw new IOException(String.format("LocalDBDir '%s' is not a directory!", localDBDir.getAbsolutePath()));
-		usersFile		= new File(localDBDir, "users.db");
-		idGeneratorFile	= new File(localDBDir, "id_generator.db");
+		if (localDbDir.exists() && !localDbDir.isDirectory())
+			throw new IOException(String.format("LocalDbDir '%s' is not a directory!", localDbDir.getAbsolutePath()));
+		usersFile		= new File(localDbDir, "users.db");
+		idGeneratorFile	= new File(localDbDir, "id_generator.db");
 	}
 
 	/**
diff --git a/src/main/java/envoy/client/net/Client.java b/src/main/java/envoy/client/net/Client.java
index 2e96b4a..29b2f03 100644
--- a/src/main/java/envoy/client/net/Client.java
+++ b/src/main/java/envoy/client/net/Client.java
@@ -118,6 +118,17 @@ public class Client implements Closeable {
 		return cache;
 	}
 
+	/**
+	 * Creates a new write proxy that uses this client to communicate with the
+	 * server.
+	 *
+	 * @param localDb the local database that the write proxy will use to access
+	 *                caches
+	 * @return a new write proxy
+	 * @since Envoy Client v0.3-alpha
+	 */
+	public WriteProxy createWriteProxy(LocalDb localDb) { return new WriteProxy(this, localDb); }
+
 	/**
 	 * Sends a message to the server. The message's status will be incremented once
 	 * it was delivered successfully.
diff --git a/src/main/java/envoy/client/net/WriteProxy.java b/src/main/java/envoy/client/net/WriteProxy.java
new file mode 100644
index 0000000..454751f
--- /dev/null
+++ b/src/main/java/envoy/client/net/WriteProxy.java
@@ -0,0 +1,102 @@
+package envoy.client.net;
+
+import java.io.IOException;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+import envoy.client.data.LocalDb;
+import envoy.client.util.EnvoyLog;
+import envoy.data.Message;
+import envoy.event.MessageStatusChangeEvent;
+
+/**
+ * Implements methods to send {@link Message}s and
+ * {@link MessageStatusChangeEvent}s to the server or cache them inside a
+ * {@link LocalDb} depending on the online status.<br>
+ * <br>
+ * Project: <strong>envoy-client</strong><br>
+ * File: <strong>WriteProxy.java</strong><br>
+ * Created: <strong>6 Feb 2020</strong><br>
+ *
+ * @author Kai S. K. Engelbart
+ * @since Envoy v0.3-alpha
+ */
+public class WriteProxy {
+
+	private final Client	client;
+	private final LocalDb	localDb;
+
+	private static final Logger logger = EnvoyLog.getLogger(WriteProxy.class.getSimpleName());
+
+	/**
+	 * Initializes a write proxy using a client and a local database. The
+	 * corresponding cache processors are injected into the caches.
+	 *
+	 * @param client  the client used to send messages and message status change
+	 *                events
+	 * @param localDb the local database used to cache messages and message status
+	 *                change events
+	 * @since Envoy v0.3-alpha
+	 */
+	public WriteProxy(Client client, LocalDb localDb) {
+		this.client		= client;
+		this.localDb	= localDb;
+
+		// Initialize cache processors for messages and message status change events
+		localDb.getMessageCache().setProcessor(msg -> {
+			try {
+				client.sendMessage(msg);
+			} catch (IOException e) {
+				logger.log(Level.SEVERE, "Could not send cached message", e);
+			}
+		});
+		localDb.getStatusCache().setProcessor(evt -> {
+			try {
+				client.sendEvent(evt);
+			} catch (IOException e) {
+				logger.log(Level.SEVERE, "Could not send cached message status change event", e);
+			}
+		});
+	}
+
+	/**
+	 * Sends cached {@link Message}s and {@link MessageStatusChangeEvent}s to the
+	 * server.
+	 * 
+	 * @since Envoy v0.3-alpha
+	 */
+	public void flushCache() {
+
+		// Send messages
+		localDb.getMessageCache().relay();
+
+		// Send message status change events
+		localDb.getStatusCache().relay();
+	}
+
+	/**
+	 * Delivers a message to the server if online. Otherwise the message is cached
+	 * inside the local database.
+	 *
+	 * @param message the message to send
+	 * @throws IOException if the message could not be sent
+	 * @since Envoy v0.3-alpha
+	 */
+	public void writeMessage(Message message) throws IOException {
+		if (client.isOnline()) client.sendMessage(message);
+		else localDb.getMessageCache().accept(message);
+	}
+
+	/**
+	 * Delivers a message status change event to the server if online. Otherwise the
+	 * event is cached inside the local database.
+	 *
+	 * @param evt the event to send
+	 * @throws IOException if the event could not be sent
+	 * @since Envoy v0.3-alpha
+	 */
+	public void writeMessageStatusChangeEvent(MessageStatusChangeEvent evt) throws IOException {
+		if (client.isOnline()) client.sendEvent(evt);
+		else localDb.getStatusCache().accept(evt);
+	}
+}

From 3f7544cea3bae7e4ab86a5ba26a2498080600203 Mon Sep 17 00:00:00 2001
From: CyB3RC0nN0R <kske@outlook.de>
Date: Thu, 6 Feb 2020 21:28:02 +0100
Subject: [PATCH 3/7] Integrated WriteProxy into the sending process

---
 src/main/java/envoy/client/data/Chat.java     | 12 +++--
 src/main/java/envoy/client/ui/ChatWindow.java | 44 +++++++++----------
 src/main/java/envoy/client/ui/Startup.java    | 14 ++++--
 3 files changed, 37 insertions(+), 33 deletions(-)

diff --git a/src/main/java/envoy/client/data/Chat.java b/src/main/java/envoy/client/data/Chat.java
index f10e816..49083a7 100644
--- a/src/main/java/envoy/client/data/Chat.java
+++ b/src/main/java/envoy/client/data/Chat.java
@@ -3,7 +3,7 @@ package envoy.client.data;
 import java.io.IOException;
 import java.io.Serializable;
 
-import envoy.client.net.Client;
+import envoy.client.net.WriteProxy;
 import envoy.client.ui.list.ComponentListModel;
 import envoy.data.Message;
 import envoy.data.Message.MessageStatus;
@@ -52,22 +52,20 @@ public class Chat implements Serializable {
 	 * {@code READ} starting from the bottom and stopping once a read message is
 	 * found.
 	 *
-	 * @param client the client instance used to notify the server about the message
-	 *               status changes
+	 * @param writeProxy the write proxy instance used to notify the server about
+	 *                   the message status changes
 	 * @throws IOException if a {@link MessageStatusChangeEvent} could not be
 	 *                     delivered to the server
 	 * @since Envoy v0.3-alpha
 	 */
-	public void read(Client client) throws IOException {
+	public void read(WriteProxy writeProxy) throws IOException {
 		for (int i = model.size() - 1; i >= 0; --i) {
 			final Message m = model.get(i);
 			if (m.getSenderId() == recipient.getId()) {
 				if (m.getStatus() == MessageStatus.READ) break;
 				else {
 					m.setStatus(MessageStatus.READ);
-
-					// TODO: Cache events in offline mode
-					client.sendEvent(new MessageStatusChangeEvent(m));
+					writeProxy.writeMessageStatusChangeEvent(new MessageStatusChangeEvent(m));
 				}
 			}
 		}
diff --git a/src/main/java/envoy/client/ui/ChatWindow.java b/src/main/java/envoy/client/ui/ChatWindow.java
index 3abd54a..7d537bf 100644
--- a/src/main/java/envoy/client/ui/ChatWindow.java
+++ b/src/main/java/envoy/client/ui/ChatWindow.java
@@ -16,6 +16,7 @@ import envoy.client.data.LocalDb;
 import envoy.client.event.MessageCreationEvent;
 import envoy.client.event.ThemeChangeEvent;
 import envoy.client.net.Client;
+import envoy.client.net.WriteProxy;
 import envoy.client.ui.list.ComponentList;
 import envoy.client.ui.settings.SettingsScreen;
 import envoy.client.util.EnvoyLog;
@@ -39,8 +40,9 @@ import envoy.event.MessageStatusChangeEvent;
 public class ChatWindow extends JFrame {
 
 	// User specific objects
-	private Client	client;
-	private LocalDb	localDb;
+	private Client		client;
+	private WriteProxy	writeProxy;
+	private LocalDb		localDb;
 
 	// GUI components
 	private JPanel					contentPane				= new JPanel();
@@ -211,7 +213,7 @@ public class ChatWindow extends JFrame {
 
 		// Listen to received messages
 		EventBus.getInstance().register(MessageCreationEvent.class, (evt) -> {
-			Message message = ((MessageCreationEvent) evt).get();
+			Message	message	= ((MessageCreationEvent) evt).get();
 			Chat	chat	= localDb.getChats().stream().filter(c -> c.getRecipient().getId() == message.getSenderId()).findFirst().get();
 			chat.appendMessage(message);
 
@@ -301,8 +303,7 @@ public class ChatWindow extends JFrame {
 				.build();
 
 			// Send message
-			// TODO: Store offline messages
-			client.sendMessage(message);
+			writeProxy.writeMessage(message);
 
 			// Add message to PersistentLocalDb and update UI
 			currentChat.appendMessage(message);
@@ -345,7 +346,7 @@ public class ChatWindow extends JFrame {
 
 	private void readCurrentChat() {
 		try {
-			currentChat.read(client);
+			currentChat.read(writeProxy);
 			messageList.synchronizeModel();
 		} catch (IOException e) {
 			e.printStackTrace();
@@ -354,24 +355,23 @@ public class ChatWindow extends JFrame {
 	}
 
 	/**
-	 * Sets the {@link Client} used by this {@link ChatWindow}.
+	 * Initializes the components responsible server communication and
+	 * persistence.<br>
+	 * <br>
+	 * This will trigger the display of the contact list.
 	 *
-	 * @param client the {@link Client} used to send and receive messages
-	 * @since Envoy v0.2-alpha
+	 * @param client     the client used to send and receive messages
+	 * @param localDb    the local database used to manage stored messages
+	 *                   and users
+	 * @param writeProxy the write proxy used to send messages and status change
+	 *                   events to the server or cache them inside the local
+	 *                   database
+	 * @since Envoy v0.3-alpha
 	 */
-	public void setClient(Client client) { this.client = client; }
-
-	/**
-	 * Sets the {@link LocalDb} used by this {@link ChatWindow}. After
-	 * invoking this
-	 * method, users and chats will be loaded from the database into the GUI.
-	 *
-	 * @param localDb the {@link LocalDb} used to manage stored messages
-	 *                and users
-	 * @since Envoy v0.2-alpha
-	 */
-	public void setLocalDB(LocalDb localDb) {
-		this.localDb = localDb;
+	public void initContent(Client client, LocalDb localDb, WriteProxy writeProxy) {
+		this.client		= client;
+		this.localDb	= localDb;
+		this.writeProxy	= writeProxy;
 		loadUsersAndChats();
 	}
 }
diff --git a/src/main/java/envoy/client/ui/Startup.java b/src/main/java/envoy/client/ui/Startup.java
index 1a38da9..1c68e41 100644
--- a/src/main/java/envoy/client/ui/Startup.java
+++ b/src/main/java/envoy/client/ui/Startup.java
@@ -15,6 +15,7 @@ import envoy.client.Config;
 import envoy.client.Settings;
 import envoy.client.data.*;
 import envoy.client.net.Client;
+import envoy.client.net.WriteProxy;
 import envoy.client.util.EnvoyLog;
 import envoy.data.LoginCredentials;
 import envoy.data.Message;
@@ -148,14 +149,19 @@ public class Startup {
 					JOptionPane.WARNING_MESSAGE);
 		}
 
-		// Save all users to the local database
-		if (client.isOnline()) localDb.setUsers(client.getUsers());
+		// Initialize write proxy
+		final WriteProxy writeProxy = client.createWriteProxy(localDb);
+
+		// Save all users to the local database and flush cache
+		if (client.isOnline()) {
+			localDb.setUsers(client.getUsers());
+			writeProxy.flushCache();
+		}
 
 		// Display ChatWindow and StatusTrayIcon
 		EventQueue.invokeLater(() -> {
 			try {
-				chatWindow.setClient(client);
-				chatWindow.setLocalDB(localDb);
+				chatWindow.initContent(client, localDb, writeProxy);
 
 				try {
 					new StatusTrayIcon(chatWindow).show();

From fe6cc9f4648d456f3f1cf120de01c329c2327faf Mon Sep 17 00:00:00 2001
From: CyB3RC0nN0R <kske@outlook.de>
Date: Thu, 6 Feb 2020 21:42:17 +0100
Subject: [PATCH 4/7] Persisting cache in PersistentLocalDb

---
 src/main/java/envoy/client/data/Cache.java    |  4 +++-
 src/main/java/envoy/client/data/LocalDb.java  |  8 ++++----
 .../envoy/client/data/PersistentLocalDb.java  | 20 ++++++++++++++-----
 src/main/java/envoy/client/ui/Startup.java    |  2 +-
 4 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/src/main/java/envoy/client/data/Cache.java b/src/main/java/envoy/client/data/Cache.java
index 458cb0a..80ef26f 100644
--- a/src/main/java/envoy/client/data/Cache.java
+++ b/src/main/java/envoy/client/data/Cache.java
@@ -1,5 +1,6 @@
 package envoy.client.data;
 
+import java.io.Serializable;
 import java.util.LinkedList;
 import java.util.Queue;
 import java.util.function.Consumer;
@@ -18,12 +19,13 @@ import envoy.client.util.EnvoyLog;
  * @author Kai S. K. Engelbart
  * @since Envoy v0.3-alpha
  */
-public class Cache<T> implements Consumer<T> {
+public class Cache<T> implements Consumer<T>, Serializable {
 
 	private final Queue<T>			elements	= new LinkedList<>();
 	private transient Consumer<T>	processor;
 
 	private static final Logger logger = EnvoyLog.getLogger(Cache.class.getSimpleName());
+	private static final long	serialVersionUID	= 7343544675545545076L;
 
 	/**
 	 * Adds an element to the cache.
diff --git a/src/main/java/envoy/client/data/LocalDb.java b/src/main/java/envoy/client/data/LocalDb.java
index a606856..8034e2a 100644
--- a/src/main/java/envoy/client/data/LocalDb.java
+++ b/src/main/java/envoy/client/data/LocalDb.java
@@ -24,8 +24,8 @@ public abstract class LocalDb {
 	protected Map<String, User>					users	= new HashMap<>();
 	protected List<Chat>						chats	= new ArrayList<>();
 	protected IdGenerator						idGenerator;
-	protected Cache<Message>					messageCache;
-	protected Cache<MessageStatusChangeEvent>	statusCache;
+	protected Cache<Message>					messageCache	= new Cache<>();
+	protected Cache<MessageStatusChangeEvent>	statusCache		= new Cache<>();
 
 	/**
 	 * Initializes a storage space for a user-specific list of chats.
@@ -52,12 +52,12 @@ public abstract class LocalDb {
 	public void loadUsers() throws Exception {}
 
 	/**
-	 * Loads all chat data of the client user.
+	 * Loads all data of the client user.
 	 *
 	 * @throws Exception if the loading process failed
 	 * @since Envoy v0.3-alpha
 	 */
-	public void loadChats() throws Exception {}
+	public void loadUserData() throws Exception {}
 
 	/**
 	 * Loads the ID generator. Any exception thrown during this process is ignored.
diff --git a/src/main/java/envoy/client/data/PersistentLocalDb.java b/src/main/java/envoy/client/data/PersistentLocalDb.java
index 7052c60..d6e594a 100644
--- a/src/main/java/envoy/client/data/PersistentLocalDb.java
+++ b/src/main/java/envoy/client/data/PersistentLocalDb.java
@@ -23,7 +23,7 @@ import envoy.util.SerializationUtils;
  */
 public class PersistentLocalDb extends LocalDb {
 
-	private File localDBDir, localDBFile, usersFile, idGeneratorFile;
+	private File localDBDir, localDBFile, usersFile, idGeneratorFile, messageCacheFile, statusCacheFile;
 
 	/**
 	 * Initializes an empty local database without a directory. All changes made to
@@ -63,7 +63,9 @@ public class PersistentLocalDb extends LocalDb {
 	@Override
 	public void initializeUserStorage() {
 		if (user == null) throw new NullPointerException("Client user is null");
-		localDBFile = new File(localDBDir, user.getId() + ".db");
+		localDBFile			= new File(localDBDir, user.getId() + ".db");
+		messageCacheFile	= new File(localDBDir, user.getId() + "_message_cache.db");
+		statusCacheFile		= new File(localDBDir, user.getId() + "_status_cache.db");
 	}
 
 	@Override
@@ -71,8 +73,12 @@ public class PersistentLocalDb extends LocalDb {
 		// Save users
 		SerializationUtils.write(usersFile, users);
 
-		// Save chats
-		if (user != null) SerializationUtils.write(localDBFile, chats);
+		// Save user data
+		if (user != null) {
+			SerializationUtils.write(localDBFile, chats);
+			SerializationUtils.write(messageCacheFile, messageCache);
+			SerializationUtils.write(statusCacheFile, statusCache);
+		}
 
 		// Save id generator
 		if (hasIdGenerator()) SerializationUtils.write(idGeneratorFile, idGenerator);
@@ -82,7 +88,11 @@ public class PersistentLocalDb extends LocalDb {
 	public void loadUsers() throws ClassNotFoundException, IOException { users = SerializationUtils.read(usersFile, HashMap.class); }
 
 	@Override
-	public void loadChats() throws ClassNotFoundException, IOException { chats = SerializationUtils.read(localDBFile, ArrayList.class); }
+	public void loadUserData() throws ClassNotFoundException, IOException {
+		chats			= SerializationUtils.read(localDBFile, ArrayList.class);
+		messageCache	= SerializationUtils.read(messageCacheFile, Cache.class);
+		statusCache		= SerializationUtils.read(statusCacheFile, Cache.class);
+	}
 
 	@Override
 	public void loadIdGenerator() {
diff --git a/src/main/java/envoy/client/ui/Startup.java b/src/main/java/envoy/client/ui/Startup.java
index 1c68e41..46f7951 100644
--- a/src/main/java/envoy/client/ui/Startup.java
+++ b/src/main/java/envoy/client/ui/Startup.java
@@ -138,7 +138,7 @@ public class Startup {
 		// Initialize chats in local database
 		try {
 			localDb.initializeUserStorage();
-			localDb.loadChats();
+			localDb.loadUserData();
 		} catch (FileNotFoundException e) {
 			// The local database file has not yet been created, probably first login
 		} catch (Exception e) {

From abd02b2c6f5bceac14c184178f7f01876d8cbec0 Mon Sep 17 00:00:00 2001
From: CyB3RC0nN0R <kske@outlook.de>
Date: Thu, 6 Feb 2020 22:17:14 +0100
Subject: [PATCH 5/7] Implemented login through command line arguments

* Moved Config and ConfigItem to data package
* Added mandatory property to ConfigItem
* Added user and password ConfigItems to Config
---
 src/main/java/envoy/client/Settings.java      |  1 +
 .../java/envoy/client/{ => data}/Config.java  | 59 +++++++++++++++----
 .../envoy/client/{ => data}/ConfigItem.java   | 46 ++++++++++++---
 .../envoy/client/data/PersistentLocalDb.java  |  1 -
 src/main/java/envoy/client/net/Client.java    |  2 +-
 src/main/java/envoy/client/ui/Startup.java    |  7 +--
 src/main/java/envoy/client/util/EnvoyLog.java |  2 +-
 7 files changed, 91 insertions(+), 27 deletions(-)
 rename src/main/java/envoy/client/{ => data}/Config.java (69%)
 rename src/main/java/envoy/client/{ => data}/ConfigItem.java (56%)

diff --git a/src/main/java/envoy/client/Settings.java b/src/main/java/envoy/client/Settings.java
index 02b6c88..efb03d6 100644
--- a/src/main/java/envoy/client/Settings.java
+++ b/src/main/java/envoy/client/Settings.java
@@ -6,6 +6,7 @@ import java.util.HashMap;
 import java.util.Map;
 import java.util.prefs.Preferences;
 
+import envoy.client.data.Config;
 import envoy.client.ui.Color;
 import envoy.client.ui.Theme;
 import envoy.util.SerializationUtils;
diff --git a/src/main/java/envoy/client/Config.java b/src/main/java/envoy/client/data/Config.java
similarity index 69%
rename from src/main/java/envoy/client/Config.java
rename to src/main/java/envoy/client/data/Config.java
index 24e7780..1f351ea 100644
--- a/src/main/java/envoy/client/Config.java
+++ b/src/main/java/envoy/client/data/Config.java
@@ -1,9 +1,12 @@
-package envoy.client;
+package envoy.client.data;
 
 import java.io.File;
+import java.security.NoSuchAlgorithmException;
 import java.util.*;
+import java.util.function.Function;
 import java.util.logging.Level;
 
+import envoy.data.LoginCredentials;
 import envoy.exception.EnvoyException;
 
 /**
@@ -26,14 +29,15 @@ public class Config {
 	private static Config config;
 
 	private Config() {
-		items.put("server", new ConfigItem<>("server", "s", (input) -> input, null));
-		items.put("port", new ConfigItem<>("port", "p", (input) -> Integer.parseInt(input), null));
-		items.put("localDB", new ConfigItem<>("localDB", "db", (input) -> new File(input), new File("localDB")));
-		items.put("ignoreLocalDB", new ConfigItem<>("ignoreLocalDB", "nodb", (input) -> Boolean.parseBoolean(input), false));
-		items.put("homeDirectory",
-				new ConfigItem<>("homeDirectory", "h", (input) -> new File(input), new File(System.getProperty("user.home"), ".envoy")));
-		items.put("fileLevelBarrier", new ConfigItem<>("fileLevelBarrier", "fb", (input) -> Level.parse(input), Level.CONFIG));
-		items.put("consoleLevelBarrier", new ConfigItem<>("consoleLevelBarrier", "cb", (input) -> Level.parse(input), Level.FINEST));
+		items.put("server", new ConfigItem<>("server", "s", Function.identity(), null, true));
+		items.put("port", new ConfigItem<>("port", "p", Integer::parseInt, null, true));
+		items.put("localDB", new ConfigItem<>("localDB", "db", File::new, new File("localDB"), true));
+		items.put("ignoreLocalDB", new ConfigItem<>("ignoreLocalDB", "nodb", Boolean::parseBoolean, false, false));
+		items.put("homeDirectory", new ConfigItem<>("homeDirectory", "h", File::new, new File(System.getProperty("user.home"), ".envoy"), true));
+		items.put("fileLevelBarrier", new ConfigItem<>("fileLevelBarrier", "fb", Level::parse, Level.CONFIG, true));
+		items.put("consoleLevelBarrier", new ConfigItem<>("consoleLevelBarrier", "cb", Level::parse, Level.FINEST, true));
+		items.put("user", new ConfigItem<>("user", "u", Function.identity()));
+		items.put("password", new ConfigItem<>("password", "pw", String::toCharArray));
 	}
 
 	/**
@@ -95,10 +99,12 @@ public class Config {
 	}
 
 	/**
-	 * @return {@code true} if server, port and localDB directory are known.
+	 * @return {@code true} if all mandatory config items are initialized
 	 * @since Envoy v0.1-alpha
 	 */
-	public boolean isInitialized() { return items.values().stream().map(ConfigItem::get).noneMatch(Objects::isNull); }
+	public boolean isInitialized() {
+		return items.values().stream().filter(ConfigItem::isMandatory).map(ConfigItem::get).noneMatch(Objects::isNull);
+	}
 
 	/**
 	 * @return the host name of the Envoy server
@@ -141,4 +147,35 @@ public class Config {
 	 * @since Envoy v0.2-alpha
 	 */
 	public Level getConsoleLevelBarrier() { return (Level) items.get("consoleLevelBarrier").get(); }
+
+	/**
+	 * @return the user name
+	 * @since Envoy v0.3-alpha
+	 */
+	public String getUser() { return (String) items.get("user").get(); }
+
+	/**
+	 * @return the password
+	 * @since Envoy v0.3-alpha
+	 */
+	public char[] getPassword() { return (char[]) items.get("password").get(); }
+
+	/**
+	 * @return {@code true} if user name and password are set
+	 * @since Envoy v0.3-alpha
+	 */
+	public boolean hasLoginCredentials() { return getUser() != null && getPassword() != null; }
+
+	/**
+	 * @return login credentials for the specified user name and password, without
+	 *         the registration option
+	 * @since Envoy v0.3-alpha
+	 */
+	public LoginCredentials getLoginCredentials() {
+		try {
+			return new LoginCredentials(getUser(), getPassword(), false);
+		} catch (NoSuchAlgorithmException e) {
+			return null;
+		}
+	}
 }
\ No newline at end of file
diff --git a/src/main/java/envoy/client/ConfigItem.java b/src/main/java/envoy/client/data/ConfigItem.java
similarity index 56%
rename from src/main/java/envoy/client/ConfigItem.java
rename to src/main/java/envoy/client/data/ConfigItem.java
index 87e927b..440a81c 100644
--- a/src/main/java/envoy/client/ConfigItem.java
+++ b/src/main/java/envoy/client/data/ConfigItem.java
@@ -1,4 +1,4 @@
-package envoy.client;
+package envoy.client.data;
 
 import java.util.function.Function;
 
@@ -9,49 +9,70 @@ import java.util.function.Function;
  * Project: <strong>envoy-clientChess</strong><br>
  * File: <strong>ConfigItem.javaEvent.java</strong><br>
  * Created: <strong>21.12.2019</strong><br>
- * 
+ *
  * @author Kai S. K. Engelbart
  * @param <T> the type of the config item's value
  * @since Envoy v0.2-alpha
  */
 public class ConfigItem<T> {
 
-	private String				commandLong, commandShort;
-	private Function<String, T>	parseFunction;
-	private T					value;
+	private final String				commandLong, commandShort;
+	private final Function<String, T>	parseFunction;
+	private final boolean				mandatory;
+
+	private T value;
 
 	/**
 	 * Initializes a {@link ConfigItem}
-	 * 
+	 *
 	 * @param commandLong   the long command line argument to set this value
 	 * @param commandShort  the short command line argument to set this value
 	 * @param parseFunction the {@code Function<String, T>} that parses the value
 	 *                      from a string
 	 * @param defaultValue  the optional default value to set before parsing
+	 * @param mandatory     indicated that this config item must be initialized with
+	 *                      a non-null value
 	 * @since Envoy v0.2-alpha
 	 */
-	public ConfigItem(String commandLong, String commandShort, Function<String, T> parseFunction, T defaultValue) {
+	public ConfigItem(String commandLong, String commandShort, Function<String, T> parseFunction, T defaultValue, boolean mandatory) {
 		this.commandLong	= commandLong;
 		this.commandShort	= commandShort;
 		this.parseFunction	= parseFunction;
+		this.mandatory		= mandatory;
 		value				= defaultValue;
 	}
 
+	/**
+	 * Initializes an optional {@link ConfigItem} without a default value.
+	 *
+	 * @param commandLong   the long command line argument to set this value
+	 * @param commandShort  the short command line argument to set this value
+	 * @param parseFunction the {@code Function<String, T>} that parses the value
+	 *                      from a string
+	 * @since Envoy v0.3-alpha
+	 */
+	public ConfigItem(String commandLong, String commandShort, Function<String, T> parseFunction) {
+		this(commandLong, commandShort, parseFunction, null, false);
+	}
+
 	/**
 	 * Parses this {@ConfigItem}'s value from a string
+	 *
 	 * @param input the string to parse from
 	 * @since Envoy v0.2-alpha
 	 */
 	public void parse(String input) { value = parseFunction.apply(input); }
 
 	/**
-	 * @return The long command line argument to set the value of this {@link ConfigItem}
+	 * @return The long command line argument to set the value of this
+	 *         {@link ConfigItem}
 	 * @since Envoy v0.2-alpha
 	 */
 	public String getCommandLong() { return commandLong; }
 
 	/**
-	 * @return The short command line argument to set the value of this {@link ConfigItem}
+	 * @return The short command line argument to set the value of this
+	 *         {@link ConfigItem}
 	 * @since Envoy v0.2-alpha
 	 */
 	public String getCommandShort() { return commandShort; }
@@ -61,4 +82,11 @@ public class ConfigItem<T> {
 	 * @since Envoy v0.2-alpha
 	 */
 	public T get() { return value; }
+
+	/**
+	 * @return {@code true} if this {@link ConfigItem} is mandatory for successful
+	 *         application initialization
+	 * @since Envoy v0.3-alpha
+	 */
+	public boolean isMandatory() { return mandatory; }
 }
diff --git a/src/main/java/envoy/client/data/PersistentLocalDb.java b/src/main/java/envoy/client/data/PersistentLocalDb.java
index d6e594a..0a04729 100644
--- a/src/main/java/envoy/client/data/PersistentLocalDb.java
+++ b/src/main/java/envoy/client/data/PersistentLocalDb.java
@@ -5,7 +5,6 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.HashMap;
 
-import envoy.client.ConfigItem;
 import envoy.data.IdGenerator;
 import envoy.util.SerializationUtils;
 
diff --git a/src/main/java/envoy/client/net/Client.java b/src/main/java/envoy/client/net/Client.java
index 29b2f03..d742f1b 100644
--- a/src/main/java/envoy/client/net/Client.java
+++ b/src/main/java/envoy/client/net/Client.java
@@ -9,8 +9,8 @@ import java.util.logging.Logger;
 
 import javax.naming.TimeLimitExceededException;
 
-import envoy.client.Config;
 import envoy.client.data.Cache;
+import envoy.client.data.Config;
 import envoy.client.data.LocalDb;
 import envoy.client.util.EnvoyLog;
 import envoy.data.*;
diff --git a/src/main/java/envoy/client/ui/Startup.java b/src/main/java/envoy/client/ui/Startup.java
index 46f7951..13f8676 100644
--- a/src/main/java/envoy/client/ui/Startup.java
+++ b/src/main/java/envoy/client/ui/Startup.java
@@ -11,7 +11,6 @@ import javax.swing.JFrame;
 import javax.swing.JOptionPane;
 import javax.swing.SwingUtilities;
 
-import envoy.client.Config;
 import envoy.client.Settings;
 import envoy.client.data.*;
 import envoy.client.net.Client;
@@ -63,7 +62,7 @@ public class Startup {
 			// Override configuration values with command line arguments
 			if (args.length > 0) config.load(args);
 
-			// Check if all configuration values have been initialized
+			// Check if all mandatory configuration values have been initialized
 			if (!config.isInitialized()) throw new EnvoyException("Server or port are not defined");
 		} catch (Exception e) {
 			JOptionPane
@@ -76,8 +75,8 @@ public class Startup {
 		EnvoyLog.setFileLevelBarrier(config.getFileLevelBarrier());
 		EnvoyLog.setConsoleLevelBarrier(config.getConsoleLevelBarrier());
 
-		// Ask the user for their user name and password
-		LoginCredentials credentials = new LoginDialog().getCredentials();
+		// Acquire login credentials
+		LoginCredentials credentials = config.hasLoginCredentials() ? config.getLoginCredentials() : new LoginDialog().getCredentials();
 
 		if (credentials == null) {
 			logger.info("The login process has been aborted by the user. Exiting...");
diff --git a/src/main/java/envoy/client/util/EnvoyLog.java b/src/main/java/envoy/client/util/EnvoyLog.java
index b59b714..ae6c6e5 100644
--- a/src/main/java/envoy/client/util/EnvoyLog.java
+++ b/src/main/java/envoy/client/util/EnvoyLog.java
@@ -4,7 +4,7 @@ import java.io.File;
 import java.io.IOException;
 import java.util.logging.*;
 
-import envoy.client.Config;
+import envoy.client.data.Config;
 
 /**
  * Project: <strong>envoy-client</strong><br>

From 581f2d9cdf2a3a1bc85cefaa42ae190ab8bbede1 Mon Sep 17 00:00:00 2001
From: CyB3RC0nN0R <kske@outlook.de>
Date: Fri, 7 Feb 2020 09:39:15 +0100
Subject: [PATCH 6/7] Added logging statement to WriteProxy#flushCache()

---
 src/main/java/envoy/client/net/WriteProxy.java | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/main/java/envoy/client/net/WriteProxy.java b/src/main/java/envoy/client/net/WriteProxy.java
index 454751f..98206ae 100644
--- a/src/main/java/envoy/client/net/WriteProxy.java
+++ b/src/main/java/envoy/client/net/WriteProxy.java
@@ -62,10 +62,11 @@ public class WriteProxy {
 	/**
 	 * Sends cached {@link Message}s and {@link MessageStatusChangeEvent}s to the
 	 * server.
-	 * 
+	 *
 	 * @since Envoy v0.3-alpha
 	 */
 	public void flushCache() {
+		logger.info("Sending cached messages and message status change events...");
 
 		// Send messages
 		localDb.getMessageCache().relay();

From fc57e39c8fa5f76ef00ae7b1a2e30350a3d8c42f Mon Sep 17 00:00:00 2001
From: Haramus Samsamus <CyB3RC0nN0R@users.noreply.github.com>
Date: Fri, 7 Feb 2020 13:44:09 +0100
Subject: [PATCH 7/7] Fixed Javadoc errors

---
 src/main/java/envoy/client/data/ConfigItem.java | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/main/java/envoy/client/data/ConfigItem.java b/src/main/java/envoy/client/data/ConfigItem.java
index 440a81c..6a987cb 100644
--- a/src/main/java/envoy/client/data/ConfigItem.java
+++ b/src/main/java/envoy/client/data/ConfigItem.java
@@ -23,7 +23,7 @@ public class ConfigItem<T> {
 	private T value;
 
 	/**
-	 * Initializes a {@link ConfigItem}
+	 * Initializes a {@link ConfigItem}.
 	 *
 	 * @param commandLong   the long command line argument to set this value
 	 * @param commandShort  the short command line argument to set this value
@@ -56,7 +56,7 @@ public class ConfigItem<T> {
 	}
 
 	/**
-	 * Parses this {@ConfigItem}'s value from a string
+	 * Parses this {@ConfigItem}'s value from a string.
 	 *
 	 * @param input the string to parse from
 	 * @since Envoy v0.2-alpha