Prevents book migration from locking up the server thread

src/main/java/net/knarcraft/bookswithoutborders/BooksWithoutBorders.java

@@ -30,6 +30,7 @@ import net.knarcraft.bookswithoutborders.config.BooksWithoutBordersConfig;
 import net.knarcraft.bookswithoutborders.config.BwBCommand;
 import net.knarcraft.bookswithoutborders.config.StaticMessage;
 import net.knarcraft.bookswithoutborders.config.Translatable;
+import net.knarcraft.bookswithoutborders.container.MigrationRequest;
 import net.knarcraft.bookswithoutborders.handler.BookshelfHandler;
 import net.knarcraft.bookswithoutborders.listener.BookEventListener;
 import net.knarcraft.bookswithoutborders.listener.BookshelfListener;
@@ -56,9 +57,11 @@ import org.jetbrains.annotations.Nullable;
 import java.io.File;
 import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Queue;
 import java.util.UUID;
 import java.util.logging.Level;
 
@@ -67,15 +70,17 @@ import java.util.logging.Level;
  */
 public class BooksWithoutBorders extends JavaPlugin {
 
-    private static ItemFactory itemFactory;
-    private static @NotNull Map<UUID, List<String>> playerBooksList = new HashMap<>();
-    private static @NotNull List<String> publicBooksList = new ArrayList<>();
-    private static Map<Character, Integer> publicLetterIndex;
-    private static Map<UUID, Map<Character, Integer>> playerLetterIndex;
     private static BooksWithoutBorders booksWithoutBorders;
-    private static BookshelfHandler bookshelfHandler;
-    private static StringFormatter stringFormatter;
-    private static BooksWithoutBordersConfig booksWithoutBordersConfig;
+
+    private ItemFactory itemFactory;
+    private @NotNull Map<UUID, List<String>> playerBooksList = new HashMap<>();
+    private @NotNull List<String> publicBooksList = new ArrayList<>();
+    private Map<Character, Integer> publicLetterIndex;
+    private Map<UUID, Map<Character, Integer>> playerLetterIndex;
+    private BookshelfHandler bookshelfHandler;
+    private StringFormatter stringFormatter;
+    private BooksWithoutBordersConfig booksWithoutBordersConfig;
+    private final Queue<MigrationRequest> migrationQueue = new LinkedList<>();
 
     /**
      * Logs a message to the console
@@ -93,7 +98,7 @@ public class BooksWithoutBorders extends JavaPlugin {
      * @return <p>The BwB configuration</p>
      */
     public static BooksWithoutBordersConfig getConfiguration() {
-        return booksWithoutBordersConfig;
+        return getInstance().booksWithoutBordersConfig;
     }
 
     /**
@@ -102,7 +107,16 @@ public class BooksWithoutBorders extends JavaPlugin {
      * @return <p>The string formatter</p>
      */
     public static StringFormatter getStringFormatter() {
-        return stringFormatter;
+        return getInstance().stringFormatter;
+    }
+
+    /**
+     * Gets the migration queue
+     *
+     * @return <p>The migration queue</p>
+     */
+    public static Queue<MigrationRequest> getMigrationQueue() {
+        return getInstance().migrationQueue;
     }
 
     /**
@@ -115,17 +129,17 @@ public class BooksWithoutBorders extends JavaPlugin {
     @NotNull
     public static List<String> getAvailableBooks(@NotNull CommandSender sender, boolean getPublic) {
         if (getPublic) {
-            return new ArrayList<>(publicBooksList);
+            return new ArrayList<>(getInstance().publicBooksList);
         } else if (sender instanceof Player player) {
             UUID playerUUID = player.getUniqueId();
-            if (!playerBooksList.containsKey(playerUUID)) {
+            if (!getInstance().playerBooksList.containsKey(playerUUID)) {
                 List<String> newFiles = BookFileHelper.listFiles(sender, false);
                 if (newFiles != null) {
-                    playerBooksList.put(playerUUID, newFiles);
-                    playerLetterIndex.put(playerUUID, BookFileHelper.populateLetterIndices(newFiles));
+                    getInstance().playerBooksList.put(playerUUID, newFiles);
+                    getInstance().playerLetterIndex.put(playerUUID, BookFileHelper.populateLetterIndices(newFiles));
                 }
             }
-            return new ArrayList<>(playerBooksList.get(playerUUID));
+            return new ArrayList<>(getInstance().playerBooksList.get(playerUUID));
         } else {
             return new ArrayList<>();
         }
@@ -140,9 +154,9 @@ public class BooksWithoutBorders extends JavaPlugin {
     @NotNull
     public static Map<Character, Integer> getLetterIndex(@Nullable UUID playerIndex) {
         if (playerIndex == null) {
-            return publicLetterIndex;
+            return getInstance().publicLetterIndex;
         } else {
-            Map<Character, Integer> letterIndex = playerLetterIndex.get(playerIndex);
+            Map<Character, Integer> letterIndex = getInstance().playerLetterIndex.get(playerIndex);
             return Objects.requireNonNullElseGet(letterIndex, HashMap::new);
         }
     }
@@ -159,11 +173,11 @@ public class BooksWithoutBorders extends JavaPlugin {
             return;
         }
         if (updatePublic) {
-            publicBooksList = newFiles;
-            publicLetterIndex = BookFileHelper.populateLetterIndices(newFiles);
+            getInstance().publicBooksList = newFiles;
+            getInstance().publicLetterIndex = BookFileHelper.populateLetterIndices(newFiles);
         } else if (sender instanceof Player player) {
-            playerBooksList.put(player.getUniqueId(), newFiles);
-            playerLetterIndex.put(player.getUniqueId(), BookFileHelper.populateLetterIndices(newFiles));
+            getInstance().playerBooksList.put(player.getUniqueId(), newFiles);
+            getInstance().playerLetterIndex.put(player.getUniqueId(), BookFileHelper.populateLetterIndices(newFiles));
         }
     }
 
@@ -171,8 +185,8 @@ public class BooksWithoutBorders extends JavaPlugin {
      * Clears book data such as per-player lists and per-player character indexes
      */
     public static void clearBookData() {
-        playerBooksList = new HashMap<>();
-        playerLetterIndex = new HashMap<>();
+        getInstance().playerBooksList = new HashMap<>();
+        getInstance().playerLetterIndex = new HashMap<>();
     }
 
 
@@ -308,7 +322,7 @@ public class BooksWithoutBorders extends JavaPlugin {
      * @return <p>The bookshelf handler</p>
      */
     public static BookshelfHandler getBookshelfHandler() {
-        return bookshelfHandler;
+        return getInstance().bookshelfHandler;
     }
 
     /**
@@ -318,7 +332,7 @@ public class BooksWithoutBorders extends JavaPlugin {
      */
     @NotNull
     public static ItemFactory getItemFactory() {
-        return itemFactory;
+        return getInstance().itemFactory;
     }
 
     /**

src/main/java/net/knarcraft/bookswithoutborders/command/CommandMigrate.java

@@ -2,24 +2,19 @@ package net.knarcraft.bookswithoutborders.command;
 
 import net.knarcraft.bookswithoutborders.BooksWithoutBorders;
 import net.knarcraft.bookswithoutborders.config.Translatable;
-import net.knarcraft.bookswithoutborders.utility.BookFileHelper;
-import net.knarcraft.bookswithoutborders.utility.BookHelper;
-import net.knarcraft.bookswithoutborders.utility.BookToFromTextHelper;
-import org.bukkit.Bukkit;
-import org.bukkit.Material;
-import org.bukkit.OfflinePlayer;
+import net.knarcraft.bookswithoutborders.container.MigrationRequest;
+import net.knarcraft.bookswithoutborders.thread.MigrationQueueThread;
 import org.bukkit.command.Command;
 import org.bukkit.command.CommandSender;
 import org.bukkit.command.TabExecutor;
 import org.bukkit.entity.Player;
-import org.bukkit.inventory.meta.BookMeta;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import java.io.File;
-import java.io.IOException;
+import java.util.LinkedList;
 import java.util.List;
-import java.util.UUID;
+import java.util.Queue;
 import java.util.logging.Level;
 
 /**
@@ -35,12 +30,15 @@ public class CommandMigrate implements TabExecutor {
             return false;
         }
         File bookDirectory = new File(BooksWithoutBorders.getConfiguration().getBookFolder());
-        boolean success = migrateFiles(bookDirectory, player);
-        if (success) {
-            BooksWithoutBorders.sendSuccessMessage(player, "Successfully migrated all books!");
-        } else {
-            BooksWithoutBorders.sendErrorMessage(player, "Failed to migrate all books!");
-        }
+        BooksWithoutBorders.sendSuccessMessage(player, "Starting book migration...");
+        Queue<MigrationRequest> filesToMigrate = new LinkedList<>();
+        findFilesToMigrate(bookDirectory, filesToMigrate, player);
+        BooksWithoutBorders.getMigrationQueue().addAll(filesToMigrate);
+
+        BooksWithoutBorders instance = BooksWithoutBorders.getInstance();
+        MigrationQueueThread queueThread = new MigrationQueueThread();
+        int taskId = instance.getServer().getScheduler().runTaskTimer(instance, queueThread, 1L, 1L).getTaskId();
+        queueThread.setTaskId(taskId);
         return true;
     }
 
@@ -52,98 +50,25 @@ public class CommandMigrate implements TabExecutor {
     }
 
     /**
-     * Migrates the given folder recursively
+     * Finds all books that should be migrated
      *
-     * @param folder <p>The folder to migrate files for</p>
-     * @param player <p>The player causing this code to be executed</p>
-     * @return <p>If all migrations were successful</p>
+     * @param folder <p>The folder to search for books</p>
+     * @param queue  <p>The list to append found files to</p>
+     * @param player <p>The player that initiated the migration</p>
      */
-    private boolean migrateFiles(@NotNull File folder, @NotNull Player player) {
+    private void findFilesToMigrate(@NotNull File folder, @NotNull Queue<MigrationRequest> queue, @NotNull Player player) {
         File[] files = folder.listFiles();
         if (files == null) {
             BooksWithoutBorders.log(Level.WARNING, "Unable to access directory " + folder.getName() + " !");
-            return false;
+            return;
         }
-        boolean success = true;
         for (File file : files) {
             if (file.isDirectory()) {
-                success = success & migrateFiles(file, player);
+                findFilesToMigrate(file, queue, player);
             } else if (file.isFile()) {
-                success = success & migrateFile(file, player);
+                queue.add(new MigrationRequest(file, player));
             }
         }
-        return success;
-    }
-
-    /**
-     * Migrates a single book file
-     *
-     * @param file   <p>The file to migrate</p>
-     * @param player <p>The player causing this code to be executed</p>
-     * @return <p>True if the migration completed successfully</p>
-     */
-    private boolean migrateFile(@NotNull File file, @NotNull Player player) {
-        BookMeta bookMeta = (BookMeta) BooksWithoutBorders.getItemFactory().getItemMeta(Material.WRITTEN_BOOK);
-        if (bookMeta == null) {
-            return false;
-        }
-        BookMeta loadedBook;
-        String extension = BookFileHelper.getExtensionFromPath(file.getName());
-        if (extension.equalsIgnoreCase("yml")) {
-            loadedBook = BookToFromTextHelper.encryptedBookFromYml(file, bookMeta, "", true);
-        } else if (extension.equalsIgnoreCase("txt")) {
-            loadedBook = BookToFromTextHelper.bookFromFile(file, bookMeta);
-        } else {
-            BooksWithoutBorders.log(Level.WARNING, "File with unexpected extension " + extension + " encountered!");
-            return true;
-        }
-
-        if (loadedBook == null) {
-            BooksWithoutBorders.log(Level.SEVERE, "Unable to load book: " + file.getName());
-            return false;
-        }
-
-        // Attempt to retain UUID naming
-        boolean isPublic = true;
-        OfflinePlayer author = player;
-        try {
-            UUID authorId = UUID.fromString(file.getParentFile().getName());
-            author = Bukkit.getOfflinePlayer(authorId);
-            isPublic = false;
-        } catch (IllegalArgumentException ignored) {
-        }
-
-        try {
-            String newName = BookHelper.getBookFile(loadedBook, author, isPublic);
-            return saveBook(file.getParentFile(), newName, loadedBook, file);
-        } catch (IllegalArgumentException exception) {
-            BooksWithoutBorders.sendErrorMessage(player, "Failed to migrate book: " + file.getName() + " Cause:");
-            BooksWithoutBorders.sendErrorMessage(player, exception.getMessage());
-            return false;
-        }
-    }
-
-    /**
-     * Saves a migrated book
-     *
-     * @param parent   <p>The parent folder the file belongs to</p>
-     * @param newName  <p>The new name of the file</p>
-     * @param bookMeta <p>The metadata of the book to migrate</p>
-     * @param oldFile  <p>The old file path, in case it should be deleted</p>
-     * @return <p>True if successfully saved</p>
-     */
-    private boolean saveBook(@NotNull File parent, @NotNull String newName, @NotNull BookMeta bookMeta,
-                             @NotNull File oldFile) {
-        try {
-            BookToFromTextHelper.bookToYml(parent.getAbsolutePath(), newName, bookMeta);
-            if (!oldFile.getAbsolutePath().equalsIgnoreCase(new File(parent, newName + ".yml").getAbsolutePath())) {
-                return oldFile.delete();
-            }
-            return true;
-        } catch (IOException exception) {
-            BooksWithoutBorders.log(Level.SEVERE, "Failed to save migrated book: " + newName);
-            return false;
-        }
     }
 
 }

src/main/java/net/knarcraft/bookswithoutborders/container/MigrationRequest.java

@@ -0,0 +1,15 @@
+package net.knarcraft.bookswithoutborders.container;
+
+import org.bukkit.entity.Player;
+import org.jetbrains.annotations.NotNull;
+
+import java.io.File;
+
+/**
+ * A request for migrating a book
+ *
+ * @param file   <p>The file to migrate</p>
+ * @param player <p>The player that initiated the migration</p>
+ */
+public record MigrationRequest(@NotNull File file, @NotNull Player player) {
+}

src/main/java/net/knarcraft/bookswithoutborders/thread/MigrationQueueThread.java

@@ -0,0 +1,150 @@
+package net.knarcraft.bookswithoutborders.thread;
+
+import net.knarcraft.bookswithoutborders.BooksWithoutBorders;
+import net.knarcraft.bookswithoutborders.container.MigrationRequest;
+import net.knarcraft.bookswithoutborders.utility.BookFileHelper;
+import net.knarcraft.bookswithoutborders.utility.BookHelper;
+import net.knarcraft.bookswithoutborders.utility.BookToFromTextHelper;
+import org.bukkit.Bukkit;
+import org.bukkit.Material;
+import org.bukkit.OfflinePlayer;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.meta.BookMeta;
+import org.jetbrains.annotations.NotNull;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.UUID;
+import java.util.logging.Level;
+
+/**
+ * A thread for doing book migrations without locking up the main thread
+ */
+public class MigrationQueueThread implements Runnable {
+
+    private Boolean success = null;
+    private int taskId;
+
+    @Override
+    public void run() {
+        long systemTime = System.nanoTime();
+        //Repeat for at most 0.025 seconds
+        while (System.nanoTime() - systemTime < 25000000) {
+            if (pollQueue()) {
+                break;
+            }
+        }
+    }
+
+    /**
+     * Sets the task id used for stopping this task
+     *
+     * @param taskId <p>The id of this task</p>
+     */
+    public void setTaskId(int taskId) {
+        this.taskId = taskId;
+    }
+
+    /**
+     * Polls the migration queue for any waiting requests
+     *
+     * @return <p>True if the queue is empty and it's safe to quit</p>
+     */
+    public boolean pollQueue() {
+        MigrationRequest migrationRequest = BooksWithoutBorders.getMigrationQueue().poll();
+        if (migrationRequest == null) {
+            return true;
+        }
+
+        if (success == null) {
+            success = true;
+        }
+
+        success = success & migrateFile(migrationRequest.file(), migrationRequest.player());
+
+        if (BooksWithoutBorders.getMigrationQueue().peek() == null) {
+            Player player = migrationRequest.player();
+            if (success) {
+                BooksWithoutBorders.sendSuccessMessage(player, "Successfully migrated all books");
+            } else {
+                BooksWithoutBorders.sendErrorMessage(player, "Failed to migrate all books");
+            }
+            BooksWithoutBorders.getInstance().getServer().getScheduler().cancelTask(this.taskId);
+            success = null;
+            return true;
+        }
+        return false;
+    }
+
+    /**
+     * Migrates a single book file
+     *
+     * @param file   <p>The file to migrate</p>
+     * @param player <p>The player causing this code to be executed</p>
+     * @return <p>True if the migration completed successfully</p>
+     */
+    private boolean migrateFile(@NotNull File file, @NotNull Player player) {
+        BookMeta bookMeta = (BookMeta) BooksWithoutBorders.getItemFactory().getItemMeta(Material.WRITTEN_BOOK);
+        if (bookMeta == null) {
+            return false;
+        }
+        BookMeta loadedBook;
+        String extension = BookFileHelper.getExtensionFromPath(file.getName());
+        if (extension.equalsIgnoreCase("yml")) {
+            loadedBook = BookToFromTextHelper.encryptedBookFromYml(file, bookMeta, "", true);
+        } else if (extension.equalsIgnoreCase("txt")) {
+            loadedBook = BookToFromTextHelper.bookFromFile(file, bookMeta);
+        } else {
+            BooksWithoutBorders.log(Level.WARNING, "File with unexpected extension " + extension + " encountered!");
+            return true;
+        }
+
+        if (loadedBook == null) {
+            BooksWithoutBorders.log(Level.SEVERE, "Unable to load book: " + file.getName());
+            return false;
+        }
+
+        // Attempt to retain UUID naming
+        boolean isPublic = true;
+        OfflinePlayer author = player;
+        try {
+            UUID authorId = UUID.fromString(file.getParentFile().getName());
+            author = Bukkit.getOfflinePlayer(authorId);
+            isPublic = false;
+        } catch (IllegalArgumentException ignored) {
+        }
+
+        try {
+            String newName = BookHelper.getBookFile(loadedBook, author, isPublic);
+            return saveBook(file.getParentFile(), newName, loadedBook, file);
+        } catch (IllegalArgumentException exception) {
+            BooksWithoutBorders.sendErrorMessage(player, "Failed to migrate book: " + file.getName() + " Cause:");
+            BooksWithoutBorders.sendErrorMessage(player, exception.getMessage());
+            return false;
+        }
+    }
+
+    /**
+     * Saves a migrated book
+     *
+     * @param parent   <p>The parent folder the file belongs to</p>
+     * @param newName  <p>The new name of the file</p>
+     * @param bookMeta <p>The metadata of the book to migrate</p>
+     * @param oldFile  <p>The old file path, in case it should be deleted</p>
+     * @return <p>True if successfully saved</p>
+     */
+    private boolean saveBook(@NotNull File parent, @NotNull String newName, @NotNull BookMeta bookMeta,
+                             @NotNull File oldFile) {
+        try {
+            BookToFromTextHelper.bookToYml(parent.getAbsolutePath(), newName, bookMeta);
+            if (!oldFile.getAbsolutePath().equalsIgnoreCase(new File(parent, newName + ".yml").getAbsolutePath())) {
+                return oldFile.delete();
+            }
+            return true;
+        } catch (IOException exception) {
+            BooksWithoutBorders.log(Level.SEVERE, "Failed to save migrated book: " + newName);
+            return false;
+        }
+    }
+
+}