Add file versioning to the file handler

src/main/java/com/backsun/lod/handlers/LodDimensionFileHandler.java

@@ -18,7 +18,7 @@ import com.backsun.lod.objects.LodRegion;
  * to file.
  * 
  * @author James Seibel
- * @version 03-31-2021
+ * @version 05-19-2021
  */
 public class LodDimensionFileHandler
 {
@@ -30,6 +30,13 @@ public class LodDimensionFileHandler
 	private final String FILE_NAME_PREFIX = "lod";
 	private final String FILE_EXTENSION = ".txt";
 	
+	/** This is the file version currently accepted by this
+	 * file handler, older versions (smaller numbers) will be deleted and overwritten,
+	 * newer versions (larger numbers) will be ignored and won't be read. */
+	public static final int LOD_SAVE_FILE_VERSION = 1;
+	/** This is the string written before the file version */
+	private static final String LOD_FILE_VERSION_PREFIX = "lod_save_file_version";
+	
 	/** Allow saving asynchronously, but never try to save multiple regions
 	 * at a time */
 	private ExecutorService fileWritingThreadPool = Executors.newSingleThreadExecutor();
@@ -83,7 +90,41 @@ public class LodDimensionFileHandler
 		{
 			BufferedReader br = new BufferedReader(new FileReader(f));
 			String s = br.readLine();
+			int fileVersion = -1;
 			
+			// try to get the file version
+			try
+			{
+				fileVersion = Integer.parseInt(s.substring(s.indexOf(' ')).trim());
+			}
+			catch(NumberFormatException | StringIndexOutOfBoundsException e)
+			{
+				// this file doesn't have a version
+				// keep the version as -1
+			}
+			
+			// check if this file can be read by this file handler
+			if(fileVersion < LOD_SAVE_FILE_VERSION)
+			{
+				// the file we are reading is an older version,
+				// close the reader and delete the file.
+				br.close();
+				f.delete();
+				
+				return null;
+			}
+			else if(fileVersion > LOD_SAVE_FILE_VERSION)
+			{
+				// the file we are reading is an newer version,
+				// close the reader and ignore the file, we don't
+				// want to accidently delete anything the user may want.
+				br.close();
+				
+				return null;
+			}
+			
+			
+			// this file is a readable version, begin reading the file
 			while(s != null && !s.isEmpty())
 			{
 				try
@@ -98,6 +139,8 @@ public class LodDimensionFileHandler
 					// we were unable to create this chunk
 					// for whatever reason.
 					// skip to the next chunk
+					
+					// TODO write this to the log
 				}
 				
 				s = br.readLine();
@@ -107,9 +150,7 @@ public class LodDimensionFileHandler
 		}
 		catch (IOException e)
 		{
-			// File not found
-			
-			// or the buffered reader encountered a 
+			// the buffered reader encountered a 
 			// problem reading the file
 			return null;
 		}
@@ -175,6 +216,10 @@ public class LodDimensionFileHandler
 			
 			FileWriter fw = new FileWriter(f);
 			
+			// add the version of this file
+			fw.write(LOD_FILE_VERSION_PREFIX + " " + LOD_SAVE_FILE_VERSION + "\n");
+			
+			// add each LodChunk to the file
 			for(LodChunk[] chunkArray : region.getAllLods())
 				for(LodChunk chunk : chunkArray)
 					if(chunk != null && !chunk.isPlaceholder())