Show a status screen when opening the database or applying migrations

bramble-api/src/main/java/org/briarproject/bramble/api/db/DatabaseComponent.java

@@ -43,7 +43,7 @@ public interface DatabaseComponent {
 	 * @throws DataTooOldException if the data uses an older schema than the
 	 * current code and cannot be migrated
 	 */
-	boolean open() throws DbException;
+	boolean open(@Nullable MigrationListener listener) throws DbException;
 
 	/**
 	 * Waits for any open transactions to finish and closes the database.

bramble-api/src/main/java/org/briarproject/bramble/api/db/DatabaseMigrationEvent.java

@@ -0,0 +1,9 @@
+package org.briarproject.bramble.api.db;
+
+import org.briarproject.bramble.api.event.Event;
+
+/**
+ * An event that is broadcast before database migrations are being applied.
+ */
+public class DatabaseMigrationEvent extends Event {
+}

bramble-api/src/main/java/org/briarproject/bramble/api/db/MigrationListener.java

@@ -0,0 +1,11 @@
+package org.briarproject.bramble.api.db;
+
+public interface MigrationListener {
+
+	/**
+	 * This is called when a migration is started while opening the database.
+	 * It will be called once for each migration being applied.
+	 */
+	void onMigrationRun();
+
+}

bramble-api/src/main/java/org/briarproject/bramble/api/lifecycle/LifecycleManager.java

@@ -29,6 +29,14 @@ public interface LifecycleManager {
 		SUCCESS
 	}
 
+	/**
+	 * The state the lifecycle can be in.
+	 * Returned by {@link #getLifecycleState()}
+	 */
+	enum LifecycleState {
+		STARTING, MIGRATING, RUNNING
+	}
+
 	/**
 	 * Registers a {@link Service} to be started and stopped.
 	 */
@@ -76,4 +84,10 @@ public interface LifecycleManager {
 	 * the {@link DatabaseComponent} to be closed before returning.
 	 */
 	void waitForShutdown() throws InterruptedException;
+
+	/**
+	 * Returns the current state of the lifecycle.
+	 */
+	LifecycleState getLifecycleState();
+
 }

bramble-api/src/main/java/org/briarproject/bramble/api/lifecycle/event/StartupEvent.java

@@ -0,0 +1,10 @@
+package org.briarproject.bramble.api.lifecycle.event;
+
+import org.briarproject.bramble.api.event.Event;
+
+/**
+ * An event that is broadcast when the app is starting.
+ * This happens after the database was opened and services were started.
+ */
+public class StartupEvent extends Event {
+}