Fix velocity crash #3 (#10)

* Fixed [Velocity crash](https://gist.github.com/Netherwhal/5e37bd8a1656dbb9ac8cc88530144a65) happening when users in list are null

* Added forced stack trace to individuate error on Velocity restart

* Removed internal static list and reworked constructor

* Created UsersManager to keep track of loaded users

* Added usersManager field

* Added addUser method

* Updated some methods to use users manager

* Updated to use users manager to retrieve users

* Updated SimplePermProvider

src/main/java/net/simplyvanilla/simplyperms/SimplePermProvider.java

@@ -10,18 +10,24 @@
 import java.util.UUID;
 
 public class SimplePermProvider implements PermissionProvider {
+    protected final SimplyPerms plugin;
+
+    public SimplePermProvider(SimplyPerms plugin) {
+        this.plugin = plugin;
+    }
+
     @Override
     public PermissionFunction createFunction(final PermissionSubject subject) {
-        return new SimplePermFunction(subject);
+        return new SimplePermFunction(this.plugin, subject);
     }
 
-    private record SimplePermFunction(PermissionSubject subject) implements PermissionFunction {
+    private record SimplePermFunction(SimplyPerms plugin, PermissionSubject subject) implements PermissionFunction {
 
         @Override
         public Tristate getPermissionValue(final String permission) {
             if (this.subject instanceof Player) {
                 UUID uuid = ((Player) this.subject).getUniqueId();
-                User user = User.getUser(uuid);
+                User user = this.plugin.getUsersManager().getUser(uuid);
                 return user.getPermissionState(permission);
             }
             return Tristate.TRUE;

src/main/java/net/simplyvanilla/simplyperms/SimplyPerms.java

@@ -13,6 +13,7 @@
 import net.simplyvanilla.simplyperms.listeners.CommandListener;
 import net.simplyvanilla.simplyperms.users.User;
 import net.simplyvanilla.simplyperms.users.UserYAMLParser;
+import net.simplyvanilla.simplyperms.users.UsersManager;
 import net.simplyvanilla.simplyperms.utils.GroupUtils;
 import it.fulminazzo.yamlparser.configuration.ConfigurationSection;
 import it.fulminazzo.yamlparser.configuration.FileConfiguration;
@@ -44,6 +45,7 @@ public class SimplyPerms {
     private final File dataDirectory;
 
     private FileConfiguration configuration;
+    private UsersManager usersManager;
 
     static {
         FileConfiguration.addParsers(new GroupYAMLParser());
@@ -62,6 +64,8 @@ public SimplyPerms(final ProxyServer proxyServer, final Logger logger, final @Da
     public void onEnable(final ProxyInitializeEvent event) {
         this.configuration = loadConfiguration("config.yml");
 
+        this.usersManager = new UsersManager();
+
         loadGroups();
         loadUsers();
 
@@ -76,7 +80,7 @@ public void onDisable(final ProxyShutdownEvent event) {
 
     @Subscribe
     public void on(PermissionsSetupEvent event) {
-        event.setProvider(new SimplePermProvider());
+        event.setProvider(new SimplePermProvider(this));
     }
 
     public List<String> getAllowedCommands() {
@@ -108,7 +112,7 @@ private void loadUsers() {
         final ConfigurationSection usersSection = this.configuration.getConfigurationSection("users");
         if (usersSection != null)
             for (final String key : usersSection.getKeys()) {
-                usersSection.get(key, User.class);
+                this.usersManager.addUser(usersSection.get(key, User.class));
             }
     }
 
@@ -117,6 +121,6 @@ private void unloadGroups() {
     }
 
     private void unloadUsers() {
-        User.clearUsers();
+        this.usersManager.clearUsers();
     }
 }

src/main/java/net/simplyvanilla/simplyperms/users/User.java

@@ -2,27 +2,24 @@
 
 import com.velocitypowered.api.permission.Tristate;
 import it.fulminazzo.fulmicollection.objects.Printable;
+import lombok.Getter;
 import net.simplyvanilla.simplyperms.PermissionHolder;
 import net.simplyvanilla.simplyperms.groups.Group;
-import lombok.Getter;
 
 import java.util.*;
 import java.util.stream.Collectors;
 
 @Getter
 public class User extends Printable implements PermissionHolder {
-    private static final List<User> USERS = new LinkedList<>();
     private final UUID uniqueId;
     Set<String> groups = new LinkedHashSet<>();
 
-    public User(final String rawId) {
+    User(final String rawId) {
         try {
             this.uniqueId = UUID.fromString(rawId);
         } catch (Exception e) {
             throw new IllegalArgumentException(String.format("'%s' is not a valid UUID", rawId));
         }
-
-        USERS.add(this);
     }
 
     @Override
@@ -56,19 +53,4 @@ public Set<Group> getGroups() {
                 .sorted(Comparator.comparing(g -> -Group.getWeight(g)))
                 .collect(Collectors.toCollection(LinkedHashSet::new));
     }
-
-    public static User getUser(final UUID uniqueId) {
-        return uniqueId == null ? null : getUsers().stream()
-                .filter(g -> g.getUniqueId().equals(uniqueId))
-                .findFirst().orElseGet(() -> new User(uniqueId.toString()));
-    }
-
-    public static List<User> getUsers() {
-        USERS.removeIf(Objects::isNull);
-        return new LinkedList<>(USERS);
-    }
-
-    public static void clearUsers() {
-        USERS.clear();
-    }
 }

src/main/java/net/simplyvanilla/simplyperms/users/UsersManager.java

@@ -0,0 +1,33 @@
+package net.simplyvanilla.simplyperms.users;
+
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Objects;
+import java.util.UUID;
+
+public class UsersManager {
+    private final List<User> users;
+
+    public UsersManager() {
+        this.users = new LinkedList<>();
+    }
+
+    public void addUser(User user) {
+        this.users.add(user);
+    }
+
+    public User getUser(final UUID uniqueId) {
+        return uniqueId == null ? null : getUsers().stream()
+            .filter(g -> g.getUniqueId().equals(uniqueId))
+            .findFirst().orElseGet(() -> new User(uniqueId.toString()));
+    }
+
+    public List<User> getUsers() {
+        this.users.removeIf(Objects::isNull);
+        return new LinkedList<>(this.users);
+    }
+
+    public void clearUsers() {
+        this.users.clear();
+    }
+}