Add file locking to prevent concurrency issues

Added a file lock before performing a move or copy action in the FileDifference class to ensure that no concurrent modifications can happen during operation. With this, we can prevent potential data integrity issues when the file is accessed by another process at the same time. Two additional exceptions are added to handle the cases where the file is locked by another process or other unexpected situations occur.

src/main/java/fr/rakambda/filesecure/files/FileDifference.java

@@ -5,8 +5,12 @@
 import lombok.Getter;
 import lombok.extern.slf4j.Slf4j;
 import org.jetbrains.annotations.NotNull;
+import java.nio.channels.FileChannel;
+import java.nio.channels.OverlappingFileLockException;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.nio.file.StandardOpenOption;
+import java.util.Objects;
 import java.util.Optional;
 
 /**
@@ -40,22 +44,34 @@ public void applyStrategy(@NotNull BackupStrategy backupStrategy){
 			var targetPath = desiredTarget.getTargetFolder().resolve(finalName);
 			log.info("{} file {} to {}", backupStrategy.name(), sourcePath, targetPath);
 			if(!Main.parameters.isDryRun()){
-				try{
-					switch(backupStrategy){
-						case MOVE -> {
-							Files.createDirectories(desiredTarget.getTargetFolder());
-							if(Files.isDirectory(desiredTarget.getTargetFolder())){
-								Files.move(sourcePath, targetPath);
+
+				try(var channel = FileChannel.open(sourcePath, StandardOpenOption.WRITE, StandardOpenOption.READ)){
+					var fileLock = channel.tryLock();
+					if(Objects.isNull(fileLock)){
+						log.warn("Failed to get lock for {}", sourcePath);
+						return;
+					}
+
+					try(fileLock){
+						switch(backupStrategy){
+							case MOVE -> {
+								Files.createDirectories(desiredTarget.getTargetFolder());
+								if(Files.isDirectory(desiredTarget.getTargetFolder())){
+									Files.move(sourcePath, targetPath);
+								}
 							}
-						}
-						case COPY -> {
-							Files.createDirectories(desiredTarget.getTargetFolder());
-							if(Files.isDirectory(desiredTarget.getTargetFolder())){
-								Files.copy(sourcePath, targetPath);
+							case COPY -> {
+								Files.createDirectories(desiredTarget.getTargetFolder());
+								if(Files.isDirectory(desiredTarget.getTargetFolder())){
+									Files.copy(sourcePath, targetPath);
+								}
 							}
 						}
 					}
 				}
+				catch(OverlappingFileLockException e){
+					log.warn("File {} is locked, skipping", sourcePath);
+				}
 				catch(Exception e){
 					log.warn("Error applying strategy {} on file {}", backupStrategy, sourcePath, e);
 				}