Separate the sync layer from its clients. #112

briar-api/src/org/briarproject/api/sync/MessageValidator.java

@@ -0,0 +1,13 @@
+package org.briarproject.api.sync;
+
+import org.briarproject.api.db.Metadata;
+import org.briarproject.api.lifecycle.Service;
+
+public interface MessageValidator extends Service {
+
+	/**
+	 * Validates the given message and returns its metadata if the message
+	 * is valid, or null if the message is invalid.
+	 */
+	Metadata validateMessage(Message m);
+}