Adds tab completion to the delete command

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

@@ -4,11 +4,12 @@ import net.knarcraft.bookswithoutborders.BooksWithoutBorders;
 import net.knarcraft.bookswithoutborders.utility.FileHelper;
 import net.knarcraft.bookswithoutborders.utility.InputCleaningHelper;
 import org.bukkit.command.Command;
-import org.bukkit.command.CommandExecutor;
 import org.bukkit.command.CommandSender;
+import org.bukkit.command.TabExecutor;
 import org.bukkit.entity.Player;
 
 import java.io.File;
+import java.util.ArrayList;
 import java.util.List;
 
 import static net.knarcraft.bookswithoutborders.BooksWithoutBordersSettings.getBookFolder;
@@ -17,7 +18,7 @@ import static net.knarcraft.bookswithoutborders.BooksWithoutBordersSettings.getS
 /**
  * Command executor for the delete command
  */
-public class CommandDelete implements CommandExecutor {
+public class CommandDelete implements TabExecutor {
 
     @Override
     public boolean onCommand(CommandSender sender, Command command, String label, String[] args) {
@@ -46,19 +47,14 @@ public class CommandDelete implements CommandExecutor {
         //Delete the file
         if (args.length == 1) {
             List<String> availableBooks = BooksWithoutBorders.getAvailableBooks(sender, deletePublic);
-            if (availableBooks == null) {
+            if (!availableBooks.isEmpty()) {
-                BooksWithoutBorders.sendErrorMessage(sender, "You must first use /deletebook to create a list of delete-able files!");
+                performBookDeletion(sender, args[0], deletePublic);
-                return false;
+                //Update the book list
+                BooksWithoutBorders.updateBooks(sender, deletePublic);
+                return true;
             } else {
-                if (!availableBooks.isEmpty()) {
+                BooksWithoutBorders.sendErrorMessage(sender, "No files available to delete!");
-                    performBookDeletion(sender, args[0], deletePublic);
+                return false;
-                    //Update the book list
-                    BooksWithoutBorders.updateBooks(sender, deletePublic);
-                    return true;
-                } else {
-                    BooksWithoutBorders.sendErrorMessage(sender, "No files available to delete!");
-                    return false;
-                }
             }
         }
         BooksWithoutBorders.sendErrorMessage(sender, "Incorrect number of arguments for this command!");
@@ -110,4 +106,24 @@ public class CommandDelete implements CommandExecutor {
         }
     }
 
+    @Override
+    public List<String> onTabComplete(CommandSender sender, Command command, String alias, String[] args) {
+        return doTabCompletion(sender, args, false);
+    }
+
+    /**
+     * Performs tab completion
+     * @param sender <p>The sender of the command</p>
+     * @param args <p>The arguments given</p>
+     * @param deletePublic <p>Whether to delete a public book</p>
+     * @return <p>A list of available arguments</p>
+     */
+    protected List<String> doTabCompletion(CommandSender sender, String[] args, boolean deletePublic) {
+        int argumentCount = args.length;
+        if (argumentCount == 1) {
+            return BooksWithoutBorders.getAvailableBooks(sender, deletePublic);
+        }
+        return new ArrayList<>();
+    }
+
 }