Added message queue manager.

briar-api/src/org/briarproject/api/clients/MessageQueueManager.java

@@ -0,0 +1,38 @@
+package org.briarproject.api.clients;
+
+import org.briarproject.api.db.DbException;
+import org.briarproject.api.db.Metadata;
+import org.briarproject.api.db.Transaction;
+import org.briarproject.api.sync.ClientId;
+import org.briarproject.api.sync.Group;
+
+public interface MessageQueueManager {
+
+	/**
+	 * The key used for storing the queue's state in the group metadata.
+	 */
+	String QUEUE_STATE_KEY = "queueState";
+
+	/**
+	 * Sends a message using the given queue.
+	 */
+	QueueMessage sendMessage(Transaction txn, Group queue, long timestamp,
+			byte[] body, Metadata meta) throws DbException;
+
+	/**
+	 * Sets the message validator for the given client.
+	 */
+	void registerMessageValidator(ClientId c, QueueMessageValidator v);
+
+	/**
+	 * Sets the incoming message hook for the given client. The hook will be
+	 * called once for each incoming message that passes validation. Messages
+	 * are passed to the hook in order.
+	 */
+	void registerIncomingMessageHook(ClientId c, IncomingQueueMessageHook hook);
+
+	interface IncomingQueueMessageHook {
+		void incomingMessage(Transaction txn, QueueMessage q, Metadata meta)
+				throws DbException;
+	}
+}