Improves code structure, and performs some necessary work for commands

src/main/java/net/knarcraft/blacksmith/command/BlackSmithCommand.java

@@ -1,5 +1,6 @@
 package net.knarcraft.blacksmith.command;
 
+import net.md_5.bungee.api.ChatColor;
 import org.bukkit.command.Command;
 import org.bukkit.command.CommandExecutor;
 import org.bukkit.command.CommandSender;
@@ -10,11 +11,20 @@ public class BlackSmithCommand implements CommandExecutor {
     @Override
     public boolean onCommand(@NotNull CommandSender sender, @NotNull Command command, @NotNull String label,
                              @NotNull String[] args) {
+        if (!sender.hasPermission("blacksmith.admin")) {
+            sender.sendMessage(ChatColor.RED + "You don't have the necessary permission for using this command.");
+            return true;
+        }
+
         //TODO: This command should have one config sub-command which changes the default config values, and all 
         // setting names which can be changed for each NPC.
         if (args.length > 0) {
             if (args[0].equalsIgnoreCase("reload")) {
                 return new ReloadCommand().onCommand(sender, command, label, args);
+            } else if (args[0].equalsIgnoreCase("config")) {
+                //TODO: Allow changing any global/default setting + reloading here
+            } else {
+                return new NPCSettingCommand().onCommand(sender, command, label, args);
             }
         }
         return false;

src/main/java/net/knarcraft/blacksmith/command/BlackSmithTabCompleter.java

@@ -0,0 +1,31 @@
+package net.knarcraft.blacksmith.command;
+
+import net.knarcraft.blacksmith.config.NPCSetting;
+import org.bukkit.command.Command;
+import org.bukkit.command.CommandSender;
+import org.bukkit.command.TabCompleter;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class BlackSmithTabCompleter implements TabCompleter {
+
+    @Nullable
+    @Override
+    public List<String> onTabComplete(@NotNull CommandSender sender, @NotNull Command command, @NotNull String label,
+                                      @NotNull String[] args) {
+        if (!sender.hasPermission("blacksmith.admin")) {
+            return new ArrayList<>();
+        }
+
+        List<String> availableCommands = new ArrayList<>();
+        for (NPCSetting setting : NPCSetting.values()) {
+            availableCommands.add(setting.getCommandName());
+        }
+        availableCommands.add("reload");
+        return availableCommands;
+    }
+
+}

src/main/java/net/knarcraft/blacksmith/command/NPCSettingCommand.java

@@ -0,0 +1,38 @@
+package net.knarcraft.blacksmith.command;
+
+import net.citizensnpcs.api.CitizensAPI;
+import net.citizensnpcs.api.npc.NPC;
+import net.knarcraft.blacksmith.config.NPCSetting;
+import net.knarcraft.blacksmith.trait.BlacksmithTrait;
+import org.bukkit.command.Command;
+import org.bukkit.command.CommandExecutor;
+import org.bukkit.command.CommandSender;
+import org.jetbrains.annotations.NotNull;
+
+public class NPCSettingCommand implements CommandExecutor {
+
+    @Override
+    public boolean onCommand(@NotNull CommandSender sender, @NotNull Command command, @NotNull String label, @NotNull String[] args) {
+        NPC npc = CitizensAPI.getDefaultNPCSelector().getSelected(sender);
+        if (npc == null || !npc.hasTrait(BlacksmithTrait.class)) {
+            sender.sendMessage("You must select an NPC before running this command");
+            return true;
+        }
+        BlacksmithTrait blacksmithTrait = npc.getTrait(BlacksmithTrait.class);
+
+        for (NPCSetting npcSetting : NPCSetting.values()) {
+            String commandName = npcSetting.getCommandName();
+            if (commandName.equalsIgnoreCase(args[0])) {
+                if (args.length < 2) {
+                    sender.sendMessage("Current value of " + commandName + ": " +
+                            blacksmithTrait.getSettings().getRawValue(npcSetting));
+                } else {
+                    blacksmithTrait.getSettings().changeSetting(npcSetting, args[1]);
+                }
+                return true;
+            }
+        }
+        return false;
+    }
+
+}