Do the same for the password generator

core/src/main/java/com/github/games647/fastlogin/core/AuthPlugin.java

@@ -1,10 +1,59 @@
 package com.github.games647.fastlogin.core;
 
+/**
+ * Represents a supporting authentication plugin in BungeeCord and Bukkit/Spigot/... servers
+ *
+ * @param <T> either org.bukkit.entity.Player for Bukkit or net.md_5.bungee.api.connection.ProxiedPlayer for BungeeCord
+ */
 public interface AuthPlugin<T> {
 
+    /**
+     * Login the premium (paid account) player after the player joined successfully the server.
+     *
+     * <strong>This operation will be performed async while the player successfully
+     * joined the server.</strong>
+     *
+     * @param player the player that needs to be logged in
+     * @return if the operation was successful
+     */
     boolean forceLogin(T player);
 
-    boolean forceRegister(T player, String password);
+    /**
+     * Forces a register in order to protect the paid account.
+     *
+     * <strong>This operation will be performed async while the player successfully
+     * joined the server.</strong>
+     *
+     * After a successful registration the player should be logged
+     * in too.
+     *
+     * The method will be called only for premium accounts.
+     * So it's recommended to set additionally premium property
+     * if possible.
+     *
+     * Background: If we don't register an account, cracked players
+     * could steal the unregistered account from the paid
+     * player account
+     *
+     * @param player the premium account
+     * @param password a strong random generated password
+     * @return if the operation was successful
+     */
+    boolean forceRegister(T player, String password) throws Exception;
 
+    /**
+     * Checks whether an account exists for this player name.
+     *
+     * This check should check if a cracked player account exists
+     * so we can be sure the premium player doesn't steal the account
+     * of that player.
+     *
+     * This operation will be performed async while the player is
+     * connecting.
+     *
+     * @param playerName player name
+     * @return if the player has an account
+     * @throws Exception if an error occurred
+     */
     boolean isRegistered(String playerName) throws Exception;
 }

core/src/main/java/com/github/games647/fastlogin/core/shared/DefaultPasswordGenerator.java

@@ -0,0 +1,20 @@
+package com.github.games647.fastlogin.core.shared;
+
+import java.util.Random;
+
+public class DefaultPasswordGenerator<T> implements PasswordGenerator<T> {
+
+    private final Random random = new Random();
+    private static final char[] PASSWORD_CHARACTERS = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
+            .toCharArray();
+
+    @Override
+    public String getRandomPassword(T player) {
+        StringBuilder generatedPassword = new StringBuilder(8);
+        for (int i = 1; i <= 8; i++) {
+            generatedPassword.append(PASSWORD_CHARACTERS[random.nextInt(PASSWORD_CHARACTERS.length - 1)]);
+        }
+
+        return generatedPassword.toString();
+    }
+}

core/src/main/java/com/github/games647/fastlogin/core/shared/JoinManagement.java

@@ -1,5 +1,9 @@
-package com.github.games647.fastlogin.core;
+package com.github.games647.fastlogin.core.shared;
 
+import com.github.games647.fastlogin.core.AuthPlugin;
+import com.github.games647.fastlogin.core.FastLoginCore;
+import com.github.games647.fastlogin.core.PlayerProfile;
+import com.github.games647.fastlogin.core.SharedConfig;
 import java.util.UUID;
 import java.util.logging.Level;
 

core/src/main/java/com/github/games647/fastlogin/core/shared/LoginSource.java

@@ -1,4 +1,4 @@
-package com.github.games647.fastlogin.core;
+package com.github.games647.fastlogin.core.shared;
 
 import java.net.InetSocketAddress;
 

core/src/main/java/com/github/games647/fastlogin/core/shared/PasswordGenerator.java

@@ -0,0 +1,6 @@
+package com.github.games647.fastlogin.core.shared;
+
+public interface PasswordGenerator<T> {
+
+    String getRandomPassword(T player);
+}