Fixed NPE that could occur when stopping server.

src/main/java/org/samo_lego/simpleauth/SimpleAuth.java

@@ -5,6 +5,7 @@ import net.fabricmc.fabric.api.event.player.*;
 import net.fabricmc.fabric.api.event.server.ServerStopCallback;
 import net.fabricmc.fabric.api.registry.CommandRegistry;
 import net.fabricmc.loader.api.FabricLoader;
+import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.server.network.ServerPlayerEntity;
 import net.minecraft.text.LiteralText;
 import net.minecraft.text.Text;
@@ -12,10 +13,7 @@ import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.samo_lego.simpleauth.commands.*;
 import org.samo_lego.simpleauth.event.AuthEventHandler;
-import org.samo_lego.simpleauth.event.entity.player.ChatCallback;
+import org.samo_lego.simpleauth.event.entity.player.*;
-import org.samo_lego.simpleauth.event.entity.player.PlayerJoinServerCallback;
-import org.samo_lego.simpleauth.event.entity.player.PlayerLeaveServerCallback;
-import org.samo_lego.simpleauth.event.entity.player.PlayerMoveCallback;
 import org.samo_lego.simpleauth.event.item.DropItemCallback;
 import org.samo_lego.simpleauth.event.item.TakeItemCallback;
 import org.samo_lego.simpleauth.storage.AuthConfig;
@@ -75,6 +73,7 @@ public class SimpleAuth implements DedicatedServerModInitializer {
 		});
 
 		// Registering the events
+		PrePlayerJoinCallback.EVENT.register(AuthEventHandler::checkCanPlayerJoinServer);
 		PlayerJoinServerCallback.EVENT.register(AuthEventHandler::onPlayerJoin);
 		PlayerLeaveServerCallback.EVENT.register(AuthEventHandler::onPlayerLeave);
 		DropItemCallback.EVENT.register(AuthEventHandler::onDropItem);
@@ -115,6 +114,8 @@ public class SimpleAuth implements DedicatedServerModInitializer {
 
 	// De-authenticates player
 	public static void deauthenticatePlayer(ServerPlayerEntity player) {
+		if(db.isClosed())
+			return;
 		// Marking player as not authenticated, (re)setting login tries to zero
 		String uuid = player.getUuidAsString();
 		SimpleAuth.deauthenticatedUsers.put(uuid, new PlayerCache(uuid, player.getIp()));

src/main/java/org/samo_lego/simpleauth/commands/AuthCommand.java

@@ -99,7 +99,7 @@ public class AuthCommand {
         SimpleAuth.config.save(new File("./mods/SimpleAuth/config.json"));
 
         if(sender != null)
-            sender.sendSystemMessage(globalPasswordSet);
+            ((PlayerEntity) sender).sendMessage(globalPasswordSet, false);
         else
             LOGGER.info(SimpleAuth.config.lang.globalPasswordSet);
         return 1;

src/main/java/org/samo_lego/simpleauth/event/AuthEventHandler.java

@@ -1,10 +1,12 @@
 package org.samo_lego.simpleauth.event;
 
+import com.mojang.authlib.GameProfile;
 import net.minecraft.block.BlockState;
 import net.minecraft.block.Blocks;
 import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.item.ItemStack;
 import net.minecraft.network.packet.c2s.play.ChatMessageC2SPacket;
+import net.minecraft.server.PlayerManager;
 import net.minecraft.server.network.ServerPlayerEntity;
 import net.minecraft.text.LiteralText;
 import net.minecraft.text.Text;
@@ -14,6 +16,7 @@ import net.minecraft.util.math.BlockPos;
 import net.minecraft.world.World;
 import org.samo_lego.simpleauth.storage.PlayerCache;
 
+import java.net.SocketAddress;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -35,18 +38,40 @@ public class AuthEventHandler {
 
     private static Text successfulPortalRescue = new LiteralText(config.lang.successfulPortalRescue);
 
-    // Player joining the server
+    // Player pre-join
-    public static void onPlayerJoin(ServerPlayerEntity player) {
+    // Returns text as a reason for disconnect or null to pass
+    public static LiteralText checkCanPlayerJoinServer(SocketAddress socketAddress, GameProfile profile, PlayerManager manager) {
+        // Getting the player
+        String incomingPlayerUsername = profile.getName();
+        PlayerEntity onlinePlayer = manager.getPlayer(incomingPlayerUsername);
+
         // Checking if player username is valid
         String regex = config.main.usernameRegex;
 
         Pattern pattern = Pattern.compile(regex);
-        Matcher matcher = pattern.matcher(player.getName().getString());
+        Matcher matcher = pattern.matcher(incomingPlayerUsername);
-        if (!matcher.matches()) {
-            player.networkHandler.disconnect(new LiteralText(String.format(config.lang.disallowedUsername, regex)));
-            return;
-        }
 
+        if(onlinePlayer != null && config.experimental.disableAnotherLocationKick) {
+            // Player needs to be kicked, since there's already a player with that name
+            // playing on the server
+            return new LiteralText(
+                    String.format(
+                            config.lang.playerAlreadyOnline, onlinePlayer.getName().asString()
+                    )
+            );
+        }
+        else if(!matcher.matches()) {
+            return new LiteralText(
+                    String.format(
+                            config.lang.disallowedUsername, regex
+                    )
+            );
+        }
+        return null;
+    }
+
+    // Player joining the server
+    public static void onPlayerJoin(ServerPlayerEntity player) {
         // Checking if session is still valid
         String uuid = player.getUuidAsString();
         PlayerCache playerCache = deauthenticatedUsers.getOrDefault(uuid, null);
@@ -143,8 +168,8 @@ public class AuthEventHandler {
         // Setting that player was actually authenticated before leaving
         PlayerCache playerCache = deauthenticatedUsers.get(player.getUuidAsString());
         playerCache.wasAuthenticated = true;
+        // Setting the session expire time
         playerCache.validUntil = System.currentTimeMillis() + config.main.sessionTimeoutTime * 1000;
-
     }
 
     // Player chatting

src/main/java/org/samo_lego/simpleauth/event/entity/player/PrePlayerJoinCallback.java

@@ -0,0 +1,28 @@
+package org.samo_lego.simpleauth.event.entity.player;
+
+import com.mojang.authlib.GameProfile;
+import net.fabricmc.fabric.api.event.Event;
+import net.fabricmc.fabric.api.event.EventFactory;
+import net.minecraft.server.PlayerManager;
+import net.minecraft.text.LiteralText;
+
+import java.net.SocketAddress;
+
+public interface PrePlayerJoinCallback {
+    Event<PrePlayerJoinCallback> EVENT = EventFactory.createArrayBacked(
+            PrePlayerJoinCallback.class, listeners -> (
+                    socketAddress, profile, manager
+            ) -> {
+        for (PrePlayerJoinCallback event : listeners) {
+
+            LiteralText returnText = event.checkCanPlayerJoinServer(socketAddress, profile, manager);
+
+            if (returnText != null) {
+                return returnText;
+            }
+        }
+        return null;
+    });
+
+    LiteralText checkCanPlayerJoinServer(SocketAddress socketAddress, GameProfile profile, PlayerManager manager);
+}

src/main/java/org/samo_lego/simpleauth/mixin/MixinPlayerManager.java

@@ -1,14 +1,24 @@
 package org.samo_lego.simpleauth.mixin;
 
+import com.mojang.authlib.GameProfile;
 import net.minecraft.network.ClientConnection;
+import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.PlayerManager;
 import net.minecraft.server.network.ServerPlayerEntity;
+import net.minecraft.text.LiteralText;
+import net.minecraft.text.Text;
 import org.samo_lego.simpleauth.event.entity.player.PlayerJoinServerCallback;
 import org.samo_lego.simpleauth.event.entity.player.PlayerLeaveServerCallback;
+import org.samo_lego.simpleauth.event.entity.player.PrePlayerJoinCallback;
+import org.spongepowered.asm.mixin.Final;
 import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
 import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.Inject;
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+
+import java.net.SocketAddress;
 
 @Mixin(PlayerManager.class)
 public abstract class MixinPlayerManager {
@@ -22,4 +32,18 @@ public abstract class MixinPlayerManager {
     private void onPlayerLeave(ServerPlayerEntity serverPlayerEntity, CallbackInfo ci) {
         PlayerLeaveServerCallback.EVENT.invoker().onPlayerLeave(serverPlayerEntity);
     }
+
+    // Method for kicking player for
+    @Inject(method = "checkCanJoin(Ljava/net/SocketAddress;Lcom/mojang/authlib/GameProfile;)Lnet/minecraft/text/Text;", at = @At("HEAD"), cancellable = true)
+    private void checkCanJoin(SocketAddress socketAddress, GameProfile profile, CallbackInfoReturnable<Text> cir) {
+        // Getting the player that is trying to join the server
+        PlayerManager manager = (PlayerManager) (Object) this;
+
+        LiteralText returnText = PrePlayerJoinCallback.EVENT.invoker().checkCanPlayerJoinServer(socketAddress, profile, manager);
+
+        if(returnText != null) {
+            // Canceling player joining with the returnText message
+            cir.setReturnValue(returnText);
+        }
+    }
 }

src/main/java/org/samo_lego/simpleauth/mixin/MixinServerLoginNetworkHandler.java

@@ -1,43 +0,0 @@
-package org.samo_lego.simpleauth.mixin;
-
-import com.mojang.authlib.GameProfile;
-import net.minecraft.entity.player.PlayerEntity;
-import net.minecraft.server.MinecraftServer;
-import net.minecraft.server.network.ServerLoginNetworkHandler;
-import net.minecraft.text.LiteralText;
-import org.spongepowered.asm.mixin.Final;
-import org.spongepowered.asm.mixin.Mixin;
-import org.spongepowered.asm.mixin.Shadow;
-import org.spongepowered.asm.mixin.injection.At;
-import org.spongepowered.asm.mixin.injection.Inject;
-import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
-
-import static org.samo_lego.simpleauth.SimpleAuth.config;
-
-
-@Mixin(ServerLoginNetworkHandler.class)
-public abstract class MixinServerLoginNetworkHandler {
-
-    @Shadow @Final
-    private MinecraftServer server;
-
-    @Shadow
-    private GameProfile profile;
-
-    @Inject(method = "acceptPlayer()V", at = @At("HEAD"), cancellable = true)
-    private void acceptPlayer(CallbackInfo ci) {
-        //  Player pre-join event, we don't do standard callback, since
-        // there are lots of variables that would need to be passed over
-        PlayerEntity onlinePlayer = this.server.getPlayerManager().getPlayer(this.profile.getName());
-
-        // Getting network handler
-        ServerLoginNetworkHandler handler = (ServerLoginNetworkHandler) (Object) this;
-
-        if (config.experimental.disableAnotherLocationKick && onlinePlayer != null) {
-            // Player needs to be kicked, since there's already a player with that name
-            // playing on the server
-            handler.disconnect(new LiteralText(String.format(config.lang.playerAlreadyOnline, onlinePlayer.getName().asString())));
-            ci.cancel();
-        }
-    }
-}

src/main/java/org/samo_lego/simpleauth/storage/SimpleAuthDatabase.java

@@ -39,6 +39,12 @@ public class SimpleAuthDatabase {
         }
     }
 
+    // Tells whether db connection is closed
+    public boolean isClosed() {
+        return levelDBStore != null;
+    }
+
+
     // When player registers, we insert the data into DB
     public boolean registerUser(String uuid, String data) {
         try {

src/main/resources/mixins.simpleauth.json

@@ -7,7 +7,6 @@
   "server": [
     "MixinPlayerEntity",
     "MixinPlayerManager",
-    "MixinServerLoginNetworkHandler",
     "MixinServerPlayNetworkHandler",
     "MixinSlot"
   ],