Incremental backup now works (tested, but not thoroughly)

12 files changed, 248 insertions, 82 deletions

diff --git a/src/main/java/com/keuin/kbackupfabric/KBCommands.java b/src/main/java/com/keuin/kbackupfabric/KBCommands.java
index 8f0e451..847fe7c 100644
--- a/src/main/java/com/keuin/kbackupfabric/KBCommands.java
+++ b/src/main/java/com/keuin/kbackupfabric/KBCommands.java
@@ -5,9 +5,12 @@ import com.keuin.kbackupfabric.operation.BackupOperation;
 import com.keuin.kbackupfabric.operation.DeleteOperation;
 import com.keuin.kbackupfabric.operation.RestoreOperation;
 import com.keuin.kbackupfabric.operation.abstracts.i.Invokable;
+import com.keuin.kbackupfabric.operation.backup.method.ConfiguredBackupMethod;
+import com.keuin.kbackupfabric.operation.backup.method.ConfiguredIncrementalBackupMethod;
 import com.keuin.kbackupfabric.operation.backup.method.ConfiguredPrimitiveBackupMethod;
 import com.keuin.kbackupfabric.util.PrintUtil;
 import com.keuin.kbackupfabric.util.backup.BackupFilesystemUtil;
+import com.keuin.kbackupfabric.util.backup.name.IncrementalBackupFileNameEncoder;
 import com.keuin.kbackupfabric.util.backup.name.PrimitiveBackupFileNameEncoder;
 import com.keuin.kbackupfabric.util.backup.suggestion.BackupNameSuggestionProvider;
 import com.mojang.brigadier.arguments.StringArgumentType;
@@ -120,7 +123,7 @@ public final class KBCommands {
             customBackupName = String.format("a%s", customBackupName);
             msgWarn(context, String.format("Pure numeric name is not allowed. Renaming to %s", customBackupName));
         }
-        return doBackup(context, customBackupName);
+        return doBackup(context, customBackupName, false);
     }
 
     /**
@@ -130,9 +133,24 @@ public final class KBCommands {
      * @return stat code.
      */
     public static int primitiveBackupWithDefaultName(CommandContext<ServerCommandSource> context) {
-        return doBackup(context, DEFAULT_BACKUP_NAME);
+        return doBackup(context, DEFAULT_BACKUP_NAME, false);
     }
 
+    public static int incrementalBackup(CommandContext<ServerCommandSource> context) {
+        String customBackupName = StringArgumentType.getString(context, "backupName");
+        if (customBackupName.matches("[0-9]*")) {
+            // Numeric param is not allowed
+            customBackupName = String.format("a%s", customBackupName);
+            msgWarn(context, String.format("Pure numeric name is not allowed. Renaming to %s", customBackupName));
+        }
+        return doBackup(context, customBackupName, true);
+    }
+
+    public static int incrementalBackupWithDefaultName(CommandContext<ServerCommandSource> context) {
+        return doBackup(context, DEFAULT_BACKUP_NAME, true);
+    }
+
+
 //    public static int incrementalBackup(CommandContext<ServerCommandSource> context) {
 //        //KBMain.backup("name")
 //        String backupName = StringArgumentType.getString(context, "backupName");
@@ -208,13 +226,24 @@ public final class KBCommands {
         // Update pending task
         //pendingOperation = AbstractConfirmableOperation.createRestoreOperation(context, backupName);
 //        File backupFile = new File(getBackupSaveDirectory(server), getBackupFileName(backupName));
-        pendingOperation = new RestoreOperation(context, getBackupSaveDirectory(server).getAbsolutePath(), getLevelPath(server), backupFileName);
+        // TODO: improve this
+        ConfiguredBackupMethod method = backupFileName.endsWith(".zip") ?
+                new ConfiguredPrimitiveBackupMethod(
+                        backupFileName, getLevelPath(server), getBackupSaveDirectory(server).getAbsolutePath()
+                ) : new ConfiguredIncrementalBackupMethod(
+                backupFileName, getLevelPath(server),
+                getBackupSaveDirectory(server).getAbsolutePath(),
+                getIncrementalBackupBaseDirectory(server).getAbsolutePath()
+        );
+        // String backupSavePath, String levelPath, String backupFileName
+//        getBackupSaveDirectory(server).getAbsolutePath(), getLevelPath(server), backupFileName
+        pendingOperation = new RestoreOperation(context, method);
 
         msgWarn(context, String.format("RESET WARNING: You will LOSE YOUR CURRENT WORLD PERMANENTLY! The worlds will be replaced with backup %s . Use /kb confirm to start or /kb cancel to abort.", backupFileName), true);
         return SUCCESS;
     }
 
-    private static int doBackup(CommandContext<ServerCommandSource> context, String customBackupName) {
+    private static int doBackup(CommandContext<ServerCommandSource> context, String customBackupName, boolean incremental) {
         // Real backup name (compatible with legacy backup): date_name, such as 2020-04-23_21-03-00_test
         //KBMain.backup("name")
 //        String backupName = BackupNameTimeFormatter.getTimeString() + "_" + customBackupName;
@@ -232,10 +261,15 @@ public final class KBCommands {
 
         // configure backup method
         MinecraftServer server = context.getSource().getMinecraftServer();
-        ConfiguredPrimitiveBackupMethod method = new ConfiguredPrimitiveBackupMethod(
+        ConfiguredBackupMethod method = !incremental ? new ConfiguredPrimitiveBackupMethod(
                 new PrimitiveBackupFileNameEncoder().encode(customBackupName, LocalDateTime.now()),
                 getLevelPath(server),
                 getBackupSaveDirectory(server).getAbsolutePath()
+        ) : new ConfiguredIncrementalBackupMethod(
+                new IncrementalBackupFileNameEncoder().encode(customBackupName, LocalDateTime.now()),
+                getLevelPath(server),
+                getBackupSaveDirectory(server).getAbsolutePath(),
+                getIncrementalBackupBaseDirectory(server).getAbsolutePath()
         );
 
         // dispatch to operation worker
diff --git a/src/main/java/com/keuin/kbackupfabric/KBCommandsRegister.java b/src/main/java/com/keuin/kbackupfabric/KBCommandsRegister.java
index 4154464..d9ace66 100644
--- a/src/main/java/com/keuin/kbackupfabric/KBCommandsRegister.java
+++ b/src/main/java/com/keuin/kbackupfabric/KBCommandsRegister.java
@@ -18,18 +18,16 @@ public final class KBCommandsRegister {
         // register /kb list for showing the backup list. OP is required.
         dispatcher.register(CommandManager.literal("kb").then(CommandManager.literal("list").requires(PermissionValidator::op).executes(KBCommands::list)));
 
-//        // register /kb backup incremental [name]
-//        dispatcher.register(CommandManager.literal("kb").then(CommandManager.literal("backup").then(
-//                CommandManager.literal("incremental").then(
-//                        CommandManager.argument("backupName", StringArgumentType.greedyString()).requires(PermissionValidator::op).executes(KBCommands::incrementalBackup)
-//                ).requires(PermissionValidator::op).executes(KBCommands::incrementalBackupWithDefaultName)))
-//        );
-
         // register /kb backup [name] for performing backup. OP is required.
         dispatcher.register(CommandManager.literal("kb").then(CommandManager.literal("backup").then(
                 CommandManager.argument("backupName", StringArgumentType.greedyString()).requires(PermissionValidator::op).executes(KBCommands::primitiveBackup)
         ).requires(PermissionValidator::op).executes(KBCommands::primitiveBackupWithDefaultName)));
 
+        // register /kb incbak [name] for performing incremental backup. OP is required.
+        dispatcher.register(CommandManager.literal("kb").then(CommandManager.literal("incbak").then(
+                CommandManager.argument("backupName", StringArgumentType.greedyString()).requires(PermissionValidator::op).executes(KBCommands::incrementalBackup)
+        ).requires(PermissionValidator::op).executes(KBCommands::incrementalBackupWithDefaultName)));
+
         // register /kb restore <name> for performing restore. OP is required.
         dispatcher.register(CommandManager.literal("kb").then(CommandManager.literal("restore").then(CommandManager.argument("backupName", StringArgumentType.greedyString()).suggests(BackupNameSuggestionProvider.getProvider()).requires(PermissionValidator::op).executes(KBCommands::restore)).executes(KBCommands::list)));
 
diff --git a/src/main/java/com/keuin/kbackupfabric/operation/BackupOperation.java b/src/main/java/com/keuin/kbackupfabric/operation/BackupOperation.java
index 645facd..b38921d 100644
--- a/src/main/java/com/keuin/kbackupfabric/operation/BackupOperation.java
+++ b/src/main/java/com/keuin/kbackupfabric/operation/BackupOperation.java
@@ -9,13 +9,11 @@ import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.command.ServerCommandSource;
 import net.minecraft.world.World;
 
-import java.io.File;
 import java.io.IOException;
 import java.util.HashMap;
 import java.util.Map;
 
 import static com.keuin.kbackupfabric.util.PrintUtil.msgInfo;
-import static com.keuin.kbackupfabric.util.backup.BackupFilesystemUtil.getBackupSaveDirectory;
 
 public class BackupOperation extends InvokableAsyncBlockingOperation {
 
@@ -39,15 +37,12 @@ public class BackupOperation extends InvokableAsyncBlockingOperation {
             //// Do our main backup logic
 
             // Create backup saving directory
-            File backupSaveDirectoryFile = getBackupSaveDirectory(server);
-            backupSaveDirectory = backupSaveDirectoryFile.getName();
-            if (!backupSaveDirectoryFile.isDirectory() && !backupSaveDirectoryFile.mkdir()) {
-                msgInfo(context, String.format("Failed to create backup saving directory: %s. Failed to backup.", backupSaveDirectory));
+            if (!configuredBackupMethod.touch()) {
+                PrintUtil.msgErr(context, "Failed to create backup save directory. Cannot backup.");
                 return;
             }
 
-            // Make zip
-
+            // Backup
             BackupFeedback result = configuredBackupMethod.backup();
             if (result.isSuccess()) {
                 // Restore old auto-save switch stat
diff --git a/src/main/java/com/keuin/kbackupfabric/operation/RestoreOperation.java b/src/main/java/com/keuin/kbackupfabric/operation/RestoreOperation.java
index 011d2e2..b870746 100644
--- a/src/main/java/com/keuin/kbackupfabric/operation/RestoreOperation.java
+++ b/src/main/java/com/keuin/kbackupfabric/operation/RestoreOperation.java
@@ -2,37 +2,35 @@ package com.keuin.kbackupfabric.operation;
 
 import com.keuin.kbackupfabric.operation.abstracts.InvokableBlockingOperation;
 import com.keuin.kbackupfabric.operation.backup.method.ConfiguredBackupMethod;
-import com.keuin.kbackupfabric.operation.backup.method.ConfiguredPrimitiveBackupMethod;
 import com.keuin.kbackupfabric.util.PrintUtil;
 import com.mojang.brigadier.context.CommandContext;
 import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.command.ServerCommandSource;
 
 import java.io.IOException;
+import java.util.Objects;
 
 public class RestoreOperation extends InvokableBlockingOperation {
 
     //private static final Logger LOGGER = LogManager.getLogger();
-    private final String backupFileName;
     private final Thread serverThread;
     private final CommandContext<ServerCommandSource> context;
     private final MinecraftServer server;
     private final ConfiguredBackupMethod configuredBackupMethod;
 
-    public RestoreOperation(CommandContext<ServerCommandSource> context, String backupSavePath, String levelPath, String backupFileName) {
-        server = context.getSource().getMinecraftServer();
-        this.backupFileName = backupFileName;
-        this.serverThread = server.getThread();
-        this.context = context;
-        this.configuredBackupMethod = new ConfiguredPrimitiveBackupMethod(backupFileName, levelPath, backupSavePath);
+    public RestoreOperation(CommandContext<ServerCommandSource> context, ConfiguredBackupMethod configuredBackupMethod) {
+        server = Objects.requireNonNull(context.getSource().getMinecraftServer());
+        this.serverThread = Objects.requireNonNull(server.getThread());
+        this.context = Objects.requireNonNull(context);
+        this.configuredBackupMethod = Objects.requireNonNull(configuredBackupMethod);
     }
 
     @Override
     protected boolean blockingContext() {
         // do restore to backupName
-        PrintUtil.broadcast(String.format("Restoring to backup %s ...", backupFileName));
+        PrintUtil.broadcast(String.format("Restoring to backup %s ...", configuredBackupMethod.getBackupFileName()));
 
-        PrintUtil.debug("Backup file name: " + backupFileName);
+        PrintUtil.debug("Backup file name: " + configuredBackupMethod.getBackupFileName());
 
         PrintUtil.msgInfo(context, "Server will shutdown in a few seconds, depending on world size and disk speed, the progress may take from seconds to minutes.", true);
         PrintUtil.msgInfo(context, "Please do not force the server stop, or the level would be broken.", true);
@@ -58,7 +56,7 @@ public class RestoreOperation extends InvokableBlockingOperation {
 
     @Override
     public String toString() {
-        return String.format("restoration from %s", backupFileName);
+        return String.format("restoration from %s", configuredBackupMethod.getBackupFileName());
     }
 
     private class WorkerThread implements Runnable {
@@ -71,7 +69,7 @@ public class RestoreOperation extends InvokableBlockingOperation {
                 while (serverThread.isAlive()) {
                     try {
                         serverThread.join();
-                    } catch (InterruptedException ignored) {
+                    } catch (InterruptedException | RuntimeException ignored) {
                     }
                 }
 
@@ -85,7 +83,15 @@ public class RestoreOperation extends InvokableBlockingOperation {
                 }while(--cnt > 0);
 
                 ////////////////////
+                long startTime = System.currentTimeMillis();
                 if (configuredBackupMethod.restore()) {
+                    long endTime = System.currentTimeMillis();
+                    PrintUtil.info(String.format(
+                            "Restore complete! (%.2fs) Please restart the server manually.",
+                            (endTime - startTime) / 1000.0
+                    ));
+                    PrintUtil.info("If you want to restart automatically after restoring, " +
+                            "please check the manual at: https://github.com/keuin/KBackup-Fabric/blob/master/README.md");
                     //ServerRestartUtil.forkAndRestart();
                     System.exit(111);
                 } else {
@@ -94,9 +100,11 @@ public class RestoreOperation extends InvokableBlockingOperation {
 
             } catch (SecurityException e) {
                 PrintUtil.error("An exception occurred while restoring: " + e.getMessage());
+                e.printStackTrace();
             } catch (IOException e) {
                 PrintUtil.error(e.toString());
-                PrintUtil.error("Failed to restore.");
+                PrintUtil.error("Failed to restore due to an unhandled I/O exception.");
+                e.printStackTrace();
             }
             System.exit(0); // all failed restoration will eventually go here
         }
diff --git a/src/main/java/com/keuin/kbackupfabric/operation/backup/method/ConfiguredBackupMethod.java b/src/main/java/com/keuin/kbackupfabric/operation/backup/method/ConfiguredBackupMethod.java
index b1b8d90..bb80c80 100644
--- a/src/main/java/com/keuin/kbackupfabric/operation/backup/method/ConfiguredBackupMethod.java
+++ b/src/main/java/com/keuin/kbackupfabric/operation/backup/method/ConfiguredBackupMethod.java
@@ -20,4 +20,18 @@ public interface ConfiguredBackupMethod {
 
     boolean restore() throws IOException;
 
+    /**
+     * Create backup save directory and do some essential initialization before the backup process.
+     *
+     * @return false if failed, then the backup process won't proceed.
+     */
+    boolean touch();
+
+    /**
+     * Get the used backup file name.
+     *
+     * @return the file name.
+     */
+    String getBackupFileName();
+
 }
diff --git a/src/main/java/com/keuin/kbackupfabric/operation/backup/method/ConfiguredIncrementalBackupMethod.java b/src/main/java/com/keuin/kbackupfabric/operation/backup/method/ConfiguredIncrementalBackupMethod.java
index 0201d18..b5d2463 100644
--- a/src/main/java/com/keuin/kbackupfabric/operation/backup/method/ConfiguredIncrementalBackupMethod.java
+++ b/src/main/java/com/keuin/kbackupfabric/operation/backup/method/ConfiguredIncrementalBackupMethod.java
@@ -1,52 +1,92 @@
 package com.keuin.kbackupfabric.operation.backup.method;
 
 import com.keuin.kbackupfabric.operation.backup.feedback.IncrementalBackupFeedback;
+import com.keuin.kbackupfabric.util.FilesystemUtil;
+import com.keuin.kbackupfabric.util.PrintUtil;
 import com.keuin.kbackupfabric.util.backup.incremental.ObjectCollection;
 import com.keuin.kbackupfabric.util.backup.incremental.ObjectCollectionFactory;
 import com.keuin.kbackupfabric.util.backup.incremental.ObjectCollectionSerializer;
 import com.keuin.kbackupfabric.util.backup.incremental.identifier.Sha256Identifier;
 import com.keuin.kbackupfabric.util.backup.incremental.manager.IncrementalBackupStorageManager;
-import com.keuin.kbackupfabric.util.backup.name.IncrementalBackupFileNameEncoder;
 
 import java.io.File;
 import java.io.IOException;
 import java.nio.file.Paths;
-import java.time.LocalDateTime;
+import java.util.Arrays;
+import java.util.HashSet;
 
 public class ConfiguredIncrementalBackupMethod implements ConfiguredBackupMethod {
 
-    private final String backupFileName;
+    private final String backupIndexFileName;
     private final String levelPath;
-    private final String backupSavePath;
+    private final String backupIndexFileSaveDirectory;
+    private final String backupBaseDirectory;
 
-    public ConfiguredIncrementalBackupMethod(String backupFileName, String levelPath, String backupSavePath) {
-        this.backupFileName = backupFileName;
+    public ConfiguredIncrementalBackupMethod(String backupIndexFileName, String levelPath, String backupIndexFileSaveDirectory, String backupBaseDirectory) {
+        this.backupIndexFileName = backupIndexFileName;
         this.levelPath = levelPath;
-        this.backupSavePath = backupSavePath;
+        this.backupIndexFileSaveDirectory = backupIndexFileSaveDirectory;
+        this.backupBaseDirectory = backupBaseDirectory;
     }
 
     @Override
     public IncrementalBackupFeedback backup() throws IOException {
-        String customBackupName = new IncrementalBackupFileNameEncoder().decode(backupFileName).customName;
-        String backupIndexFileName = new IncrementalBackupFileNameEncoder().encode(customBackupName, LocalDateTime.now());
         File levelPathFile = new File(levelPath);
 
         // construct incremental backup index
+        PrintUtil.info("Hashing files...");
         ObjectCollection collection = new ObjectCollectionFactory<>(Sha256Identifier.getFactory())
-                .fromDirectory(levelPathFile);
+                .fromDirectory(levelPathFile, new HashSet<>(Arrays.asList("session.lock", "kbackup_metadata")));
 
         // update storage
-        IncrementalBackupStorageManager storageManager = new IncrementalBackupStorageManager(Paths.get(backupSavePath));
+        PrintUtil.info("Copying files...");
+        IncrementalBackupStorageManager storageManager = new IncrementalBackupStorageManager(Paths.get(backupBaseDirectory));
         int filesAdded = storageManager.addObjectCollection(collection, levelPathFile);
 
         // save index file
-        ObjectCollectionSerializer.toFile(collection, new File(backupSavePath, backupIndexFileName));
+        PrintUtil.info("Saving index file...");
+        ObjectCollectionSerializer.toFile(collection, new File(backupIndexFileSaveDirectory, backupIndexFileName));
 
+        // return result
+        PrintUtil.info("Incremental backup finished.");
         return new IncrementalBackupFeedback(filesAdded >= 0, filesAdded);
     }
 
     @Override
     public boolean restore() throws IOException {
-        return false;
+        // load collection
+        PrintUtil.info("Loading file list...");
+        ObjectCollection collection = ObjectCollectionSerializer.fromFile(
+                new File(backupIndexFileSaveDirectory, backupIndexFileName)
+        );
+
+        // delete old level
+        File levelPathFile = new File(levelPath);
+        PrintUtil.info("Deleting old level...");
+        if (!FilesystemUtil.forceDeleteDirectory(levelPathFile)) {
+            PrintUtil.info("Failed to delete old level!");
+            return false;
+        }
+
+        // restore file
+        PrintUtil.info("Copying files...");
+        IncrementalBackupStorageManager storageManager = new IncrementalBackupStorageManager(Paths.get(backupBaseDirectory));
+        int restoreObjectCount = storageManager.restoreObjectCollection(collection, levelPathFile);
+
+        PrintUtil.info(String.format("%d file(s) restored.", restoreObjectCount));
+        return true;
+    }
+
+    @Override
+    public boolean touch() {
+        File baseDirectoryFile = new File(backupBaseDirectory);
+        return baseDirectoryFile.isDirectory() || baseDirectoryFile.mkdir();
+    }
+
+    @Override
+    public String getBackupFileName() {
+        return backupIndexFileName;
     }
+
+
 }
diff --git a/src/main/java/com/keuin/kbackupfabric/operation/backup/method/ConfiguredPrimitiveBackupMethod.java b/src/main/java/com/keuin/kbackupfabric/operation/backup/method/ConfiguredPrimitiveBackupMethod.java
index c3013e9..1c3c9f6 100644
--- a/src/main/java/com/keuin/kbackupfabric/operation/backup/method/ConfiguredPrimitiveBackupMethod.java
+++ b/src/main/java/com/keuin/kbackupfabric/operation/backup/method/ConfiguredPrimitiveBackupMethod.java
@@ -15,8 +15,6 @@ import java.io.IOException;
 import java.nio.file.Paths;
 import java.time.LocalDateTime;
 
-import static org.apache.commons.io.FileUtils.forceDelete;
-
 public class ConfiguredPrimitiveBackupMethod implements ConfiguredBackupMethod {
 
     private final String backupFileName;
@@ -56,37 +54,17 @@ public class ConfiguredPrimitiveBackupMethod implements ConfiguredBackupMethod {
     public boolean restore() throws IOException {
         // Delete old level
         PrintUtil.info("Server stopped. Deleting old level ...");
-        File levelDirFile = new File(levelPath);
-        long startTime = System.currentTimeMillis();
-
-        int failedCounter = 0;
-        final int MAX_RETRY_TIMES = 20;
-        while (failedCounter < MAX_RETRY_TIMES) {
-            System.gc();
-            if (!levelDirFile.delete() && levelDirFile.exists()) {
-                System.gc();
-                forceDelete(levelDirFile); // Try to force delete.
-            }
-            if (!levelDirFile.exists())
-                break;
-            ++failedCounter;
-            try {
-                Thread.sleep(500);
-            } catch (InterruptedException ignored) {
-            }
-        }
-        if (levelDirFile.exists()) {
-            PrintUtil.error(String.format("Cannot restore: failed to delete old level %s .", levelDirFile.getName()));
+        if (!FilesystemUtil.forceDeleteDirectory(new File(levelPath))) {
+            PrintUtil.info("Failed to delete old level!");
             return false;
         }
 
+
         // TODO: Refactor this to the concrete BackupMethod.
         // Decompress archive
         PrintUtil.info("Decompressing archived level ...");
         ZipUtil.unzip(Paths.get(backupSavePath, backupFileName).toString(), levelPath, false);
-        long endTime = System.currentTimeMillis();
-        PrintUtil.info(String.format("Restore complete! (%.2fs) Please restart the server manually.", (endTime - startTime) / 1000.0));
-        PrintUtil.info("If you want to restart automatically after restoring, please check the manual at: https://github.com/keuin/KBackup-Fabric/blob/master/README.md");
+
 
 //        try {
 //            Thread.sleep(1000);
@@ -95,4 +73,16 @@ public class ConfiguredPrimitiveBackupMethod implements ConfiguredBackupMethod {
 
         return true;
     }
+
+    @Override
+    public boolean touch() {
+        File backupSaveDirectoryFile = new File(backupSavePath);
+        return backupSaveDirectoryFile.isDirectory() || backupSaveDirectoryFile.mkdir();
+    }
+
+    @Override
+    public String getBackupFileName() {
+        return backupFileName;
+    }
+
 }
diff --git a/src/main/java/com/keuin/kbackupfabric/util/FilesystemUtil.java b/src/main/java/com/keuin/kbackupfabric/util/FilesystemUtil.java
index 7f74725..f245cff 100644
--- a/src/main/java/com/keuin/kbackupfabric/util/FilesystemUtil.java
+++ b/src/main/java/com/keuin/kbackupfabric/util/FilesystemUtil.java
@@ -1,6 +1,9 @@
 package com.keuin.kbackupfabric.util;
 
 import java.io.File;
+import java.io.IOException;
+
+import static org.apache.commons.io.FileUtils.forceDelete;
 
 public class FilesystemUtil {
 
@@ -22,12 +25,43 @@ public class FilesystemUtil {
 
     public static long getFileSizeBytes(String filePath) {
         long fileSize = -1;
-        try{
+        try {
             File backupZipFile = new File(filePath);
             fileSize = backupZipFile.length();
-        } catch (SecurityException ignored){
+        } catch (SecurityException ignored) {
         }
         return fileSize;
     }
 
+    public static boolean forceDeleteDirectory(File levelDirFile) throws IOException {
+        int failedCounter = 0;
+        final int MAX_RETRY_TIMES = 20;
+        IOException exception = null;
+        while (failedCounter < MAX_RETRY_TIMES) {
+            System.gc();
+            if (!levelDirFile.delete() && levelDirFile.exists()) {
+                System.gc();
+                try {
+                    forceDelete(levelDirFile); // Try to force delete.
+                } catch (IOException e) {
+                    exception = e;
+                }
+            }
+            if (!levelDirFile.exists())
+                break;
+            ++failedCounter;
+            try {
+                Thread.sleep(500);
+            } catch (InterruptedException ignored) {
+            }
+        }
+        if (exception != null)
+            throw exception;
+        if (levelDirFile.exists()) {
+            PrintUtil.error(String.format("Cannot restore: failed to delete old level %s .", levelDirFile.getName()));
+            return false;
+        }
+        return true;
+    }
+
 }
diff --git a/src/main/java/com/keuin/kbackupfabric/util/backup/BackupFilesystemUtil.java b/src/main/java/com/keuin/kbackupfabric/util/backup/BackupFilesystemUtil.java
index c1aa5fe..837b638 100644
--- a/src/main/java/com/keuin/kbackupfabric/util/backup/BackupFilesystemUtil.java
+++ b/src/main/java/com/keuin/kbackupfabric/util/backup/BackupFilesystemUtil.java
@@ -14,7 +14,8 @@ import java.util.regex.Pattern;
  */
 public final class BackupFilesystemUtil {
 
-    private static final String backupSaveDirectoryName = "backups";
+    private static final String BACKUP_SAVE_DIRECTORY_NAME = "backups";
+    private static final String INCREMENTAL_BASE_DIRECTORY_NAME = "incremental";
     private static final String backupFileNamePrefix = "kbackup-";
 
     @Deprecated
@@ -43,7 +44,11 @@ public final class BackupFilesystemUtil {
     }
 
     public static File getBackupSaveDirectory(MinecraftServer server) {
-        return new File(server.getRunDirectory(), backupSaveDirectoryName);
+        return new File(server.getRunDirectory(), BACKUP_SAVE_DIRECTORY_NAME);
+    }
+
+    public static File getIncrementalBackupBaseDirectory(MinecraftServer server) {
+        return new File(server.getRunDirectory(), INCREMENTAL_BASE_DIRECTORY_NAME);
     }
 
     public static String getLevelPath(MinecraftServer server) {
diff --git a/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/ObjectCollectionFactory.java b/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/ObjectCollectionFactory.java
index 627cb5c..2f3761c 100644
--- a/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/ObjectCollectionFactory.java
+++ b/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/ObjectCollectionFactory.java
@@ -1,5 +1,6 @@
 package com.keuin.kbackupfabric.util.backup.incremental;
 
+import com.keuin.kbackupfabric.util.PrintUtil;
 import com.keuin.kbackupfabric.util.backup.incremental.identifier.FileIdentifierProvider;
 import com.keuin.kbackupfabric.util.backup.incremental.identifier.ObjectIdentifier;
 
@@ -23,26 +24,32 @@ public class ObjectCollectionFactory<T extends ObjectIdentifier> {
         this.identifierFactory = identifierFactory;
     }
 
-    public ObjectCollection fromDirectory(File directory) throws IOException {
+    public ObjectCollection fromDirectory(File directory, Set<String> ignoredFiles) throws IOException {
         final Set<ObjectElement> subFiles = new HashSet<>();
         final Map<String, ObjectCollection> subCollections = new HashMap<>();
 
         if (!Objects.requireNonNull(directory).isDirectory())
             throw new IllegalArgumentException("given file is not a directory");
 
-        for (Iterator<Path> iter = Files.walk(directory.toPath(), 1).iterator(); iter.hasNext();) {
+        for (Iterator<Path> iter = Files.walk(directory.toPath(), 1).iterator(); iter.hasNext(); ) {
             Path path = iter.next();
             if (Files.isSameFile(path, directory.toPath()))
                 continue;
             File file = path.toFile();
             if (file.isDirectory()) {
-                subCollections.put(file.getName(), fromDirectory(file));
-            } else {
+                subCollections.put(file.getName(), fromDirectory(file, ignoredFiles));
+            } else if (!ignoredFiles.contains(file.getName())) {
                 subFiles.add(new ObjectElement(file.getName(), identifierFactory.fromFile(file)));
+            } else {
+                PrintUtil.info(String.format("Skipping file %s.", file.getName()));
             }
         }
 
         return new ObjectCollection(directory.getName(), subFiles, subCollections);
     }
 
+    public ObjectCollection fromDirectory(File directory) throws IOException {
+        return fromDirectory(directory, Collections.emptySet());
+    }
+
 }
diff --git a/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/manager/IncrementalBackupStorageManager.java b/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/manager/IncrementalBackupStorageManager.java
index cd15499..a4271c6 100644
--- a/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/manager/IncrementalBackupStorageManager.java
+++ b/src/main/java/com/keuin/kbackupfabric/util/backup/incremental/manager/IncrementalBackupStorageManager.java
@@ -1,9 +1,11 @@
 package com.keuin.kbackupfabric.util.backup.incremental.manager;
 
+import com.keuin.kbackupfabric.util.PrintUtil;
 import com.keuin.kbackupfabric.util.backup.incremental.ObjectCollection;
 import com.keuin.kbackupfabric.util.backup.incremental.ObjectElement;
 
 import java.io.File;
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -11,6 +13,8 @@ import java.nio.file.Paths;
 import java.util.Map;
 import java.util.Objects;
 
+import static org.apache.commons.io.FileUtils.forceDelete;
+
 public class IncrementalBackupStorageManager {
 
     private final Path backupStorageBase;
@@ -63,13 +67,50 @@ public class IncrementalBackupStorageManager {
 
         int copyCount = 0;
 
+        // touch directory
+        if (!collectionBasePath.exists()) {
+            int retryCounter = 0;
+            boolean success = false;
+            while (retryCounter++ < 5) {
+                if (collectionBasePath.mkdirs()) {
+                    success = true;
+                    break;
+                }
+            }
+            if (!success) {
+                throw new IOException("Failed to create directory " + collectionBasePath.getAbsolutePath());
+            }
+        }
+
         // copy sub files
         for (Map.Entry<String, ObjectElement> entry : collection.getElementMap().entrySet()) {
             File copySource = new File(backupStorageBase.toFile(), entry.getValue().getIdentifier().getIdentification());
+            File copyTarget = new File(collectionBasePath.getAbsolutePath(), entry.getKey());
+
             if (!baseContainsObject(entry.getValue())) {
                 throw new IOException(String.format("File %s does not exist in the base.", copySource.getName()));
             }
-            Files.copy(copySource.toPath(), Paths.get(collectionBasePath.getAbsolutePath(), entry.getKey()));
+            if (copyTarget.exists()) {
+                boolean successDeleting = false;
+                for (int i = 0; i < 5; ++i) {
+                    try {
+                        forceDelete(copyTarget);
+                        successDeleting = true;
+                        break;
+                    } catch (FileNotFoundException ignored) {
+                        break;
+                    } catch (IOException e) {
+                        PrintUtil.error(String.format("Failed to delete file %s, retry.", copyTarget.getName()));
+                    }
+                }
+                if (!successDeleting) {
+                    String msg = String.format("Failed to delete file %s.", copyTarget.getName());
+                    PrintUtil.error(msg);
+                    throw new IOException(msg);
+                }
+            }
+
+            Files.copy(copySource.toPath(), copyTarget.toPath());
             ++copyCount;
         }
 
diff --git a/src/main/java/com/keuin/kbackupfabric/util/backup/name/IncrementalBackupFileNameEncoder.java b/src/main/java/com/keuin/kbackupfabric/util/backup/name/IncrementalBackupFileNameEncoder.java
index a0d4128..3c35201 100644
--- a/src/main/java/com/keuin/kbackupfabric/util/backup/name/IncrementalBackupFileNameEncoder.java
+++ b/src/main/java/com/keuin/kbackupfabric/util/backup/name/IncrementalBackupFileNameEncoder.java
@@ -6,7 +6,7 @@ import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
 public class IncrementalBackupFileNameEncoder implements BackupFileNameEncoder {
-    private static final String backupFileNamePrefix = "incremental-";
+    private static final String backupFileNamePrefix = "incremental";
     private static final DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd_HH-mm-ss");
 
     // TODO: make this private and use singleton pattern