S ADD: Initial implementation of FlightRecords sweeper/feeder, and

S FIX: FlightRecords sweeper auto-replays the first time point after 'O' command, and
S CHG: FlightRecorder is now thread-safe

SimViewer/src/main/java/de/mpicbg/ulman/simviewer/FlightRecorder.java

+package de.mpicbg.ulman.simviewer;
+
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.io.IOException;
+import java.util.ListIterator;
+
+/**
+ * Operates on a given file that consists of messages that could be normally
+ * transferred over the network but were instead saved into this file.
+ * Owing to this class, the messages can be extracted from the file, and
+ * can be injected to the NetworkScene as if the messages would come over
+ * the network. This way, a simulation can be replayed (even backwards!)
+ * provided the file's content shows a history of some simulation -- in
+ * which case the individual time points are separated with the "tick"
+ * messages.
+ *
+ * This file was created and is being developed by Vladimir Ulman, 2019.
+ */
+public class FlightRecorder
+{
+	/** constructor to create connection to a displayed window */
+	public FlightRecorder(final NetworkScene ns)
+	{
+		//keep the reference
+		netCommandsProcessor = ns;
+	}
+
+	/** setup the reading of the FRfilename  (FR = Flight Recording) */
+	public synchronized
+	void open(final String FRfilename)
+	throws IOException
+	{
+		nextMsgs = null;
+		//NB: stays null if the consequent operations should fail
+
+		nextMsgs = Files.readAllLines(Paths.get(FRfilename)).listIterator();
+		sendNextTimepointMessages();
+	}
+
+	/** reference on the processor of the network (display) commands */
+	private
+	final NetworkScene netCommandsProcessor;
+
+	/** should always point just before the first message of a time point,
+	    this time point is termed as the "next time point"; that often
+	    means that this iterator should point just after some "tick" message */
+	private
+	ListIterator<String> nextMsgs = null;
+
+	//--------------------------------------------
+
+	/** extracts the messages from the current timepoint up to the next one,
+	    and sends the messages to the associated NetworkScene; returns true
+	    if the operation was successful */
+	public synchronized
+	boolean sendNextTimepointMessages()
+	{
+		if (nextMsgs == null) return false; //stop if the no file is opened
+
+		//advance and "transmit" the messages up to the next tick messages
+		boolean readNextMsg = true;
+		while (nextMsgs.hasNext() && readNextMsg)
+		{
+			final String msg = nextMsgs.next();
+			netCommandsProcessor.processMsg(msg);
+
+			if (msg.startsWith("v1 tick")) readNextMsg = false;
+		}
+
+		return true;
+	}
+
+	/** extracts the messages from the previous timepoint (that is the time point
+	    that is just before this one, which was just replayed), and sends the messages
+	    to the associated NetworkScene; returns true if the operation was successful */
+	public synchronized
+	boolean sendPrevTimepointMessages()
+	{
+		if (nextMsgs == null) return false; //stop if the no file is opened
+
+		//skip (very likely) over the "tick" message of the currently-replayed time point
+		if (nextMsgs.hasPrevious()) nextMsgs.previous();
+
+		//list back until "tick" message is found -- that was over the currently-replayed point
+		while (nextMsgs.hasPrevious() && !nextMsgs.previous().startsWith("v1 tick"));
+
+		//list back until "tick" message is found -- over the wanted time point,
+		//and move forward over it (to satisfy the nextMsgs's "invariant")
+		while (nextMsgs.hasPrevious() && !nextMsgs.previous().startsWith("v1 tick"));
+		if (nextMsgs.hasNext()) nextMsgs.next();
+
+		return sendNextTimepointMessages();
+	}
+
+	/** similar to the sendNextTimepointMessages() except that it acts on the very
+	    first time point (that is recorded in the currently opened file);
+	    returns true if the operation was successful */
+	public synchronized
+	boolean rewindAndSendFirstTimepoint()
+	{
+		if (nextMsgs == null) return false; //stop if the no file is opened
+
+		//reach the very beginning and then replay the "next" time point
+		while (nextMsgs.hasPrevious()) nextMsgs.previous();
+		return sendNextTimepointMessages();
+	}
+
+	/** similar to the sendNextTimepointMessages() except that it acts on the very
+	    last time point (that is recorded in the currently opened file);
+	    returns true if the operation was successful */
+	public synchronized
+	boolean rewindAndSendLastTimepoint()
+	{
+		if (nextMsgs == null) return false; //stop if the no file is opened
+
+		//reach the very end and then traverse back over the tp to be sent (the last tp)
+		while (nextMsgs.hasNext()) nextMsgs.next();
+
+		//skip (very likely) over the last "tick" message (if present...)
+		if (nextMsgs.hasPrevious()) nextMsgs.previous();
+
+		//list back until "tick" message is found, and move forward over it
+		while (nextMsgs.hasPrevious() && !nextMsgs.previous().startsWith("v1 tick"));
+		if (nextMsgs.hasNext()) nextMsgs.next();
+
+		return sendNextTimepointMessages();
+	}
+}

SimViewer/src/main/java/de/mpicbg/ulman/simviewer/NetworkScene.java

@@ -94,7 +94,7 @@ public class NetworkScene implements Runnable
 	}
 
 
-	private
+	//not private, so anyone around can use it (esp. the FlightRecorder)
 	void processMsg(final String msg)
 	{
 		try {