Added WriteProxy with creation method in Client, added caches to LocalDb

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();
 	}
 }

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; }
 }

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");
 	}
 
 	/**

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.

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);
+	}
+}