Storage system improvement

src/main/java/net/minestom/server/data/Data.java

@@ -35,6 +35,13 @@ public class Data {
         return Collections.unmodifiableSet(data.keySet());
     }
 
+    /**
+     * @return true if the data does not contain anything, false otherwise
+     */
+    public boolean isEmpty() {
+        return data.isEmpty();
+    }
+
     public Data clone() {
         Data data = new Data();
         data.data = new ConcurrentHashMap<>(this.data);

src/main/java/net/minestom/server/storage/StorageManager.java

@@ -27,7 +27,9 @@ public class StorageManager {
      * @return the specified storage folder
      */
     public StorageFolder getFolder(String folderPath, StorageSystem storageSystem) {
-        return folderMap.computeIfAbsent(folderPath, s -> new StorageFolder(storageSystem, folderPath));
+        StorageFolder storageFolder =
+                folderMap.computeIfAbsent(folderPath, s -> new StorageFolder(storageSystem, folderPath));
+        return storageFolder;
     }
 
     /**
@@ -46,6 +48,32 @@ public class StorageManager {
         return getFolder(folderPath, storageSystem);
     }
 
+    /**
+     * Used to know if the specified folder already exist or not
+     *
+     * @param folderPath
+     * @param storageSystem
+     * @return true if the folder exists, false otherwise
+     */
+    public boolean folderExists(String folderPath, StorageSystem storageSystem) {
+        return storageSystem.exists(folderPath);
+    }
+
+    /**
+     * Call {@link #folderExists(String, StorageSystem)} with the default StorageSystem
+     *
+     * @param folderPath
+     * @return
+     */
+    public boolean folderExists(String folderPath) {
+        return folderExists(folderPath, defaultStorageSystemSupplier.get());
+    }
+
+    /**
+     * Get all folders which have been loaded by {@link #getFolder(String)} or {@link #getFolder(String, StorageSystem)}
+     *
+     * @return an unmodifiable list of all the loaded StorageFolder
+     */
     public Collection<StorageFolder> getLoadedFolders() {
         return Collections.unmodifiableCollection(folderMap.values());
     }

src/main/java/net/minestom/server/storage/StorageSystem.java

@@ -3,11 +3,17 @@ package net.minestom.server.storage;
 public interface StorageSystem {
 
     /**
-     * Called when a foler is opened with this StorageSystem
-     *
-     * @param folderName the name of the folder
+     * @param folderPath
+     * @return true if the folder exists, false otherwise
      */
-    void open(String folderName);
+    boolean exists(String folderPath);
+
+    /**
+     * Called when a folder is opened with this StorageSystem
+     *
+     * @param folderPath the name of the folder
+     */
+    void open(String folderPath);
 
     /**
      * @param key

src/main/java/net/minestom/server/storage/systems/FileStorageSystem.java

@@ -5,6 +5,8 @@ import org.rocksdb.Options;
 import org.rocksdb.RocksDB;
 import org.rocksdb.RocksDBException;
 
+import java.io.File;
+
 /**
  * A storage system which is local using OS files system
  * It does make use of the RocksDB library
@@ -18,11 +20,16 @@ public class FileStorageSystem implements StorageSystem {
     private RocksDB rocksDB;
 
     @Override
-    public void open(String folderName) {
+    public boolean exists(String folderPath) {
+        return new File(folderPath).exists();
+    }
+
+    @Override
+    public void open(String folderPath) {
         Options options = new Options().setCreateIfMissing(true);
 
         try {
-            this.rocksDB = RocksDB.open(options, folderName);
+            this.rocksDB = RocksDB.open(options, folderPath);
         } catch (RocksDBException e) {
             e.printStackTrace();
         }