Yggdrasil account offline logging in

HMCL/src/main/java/org/jackhuang/hmcl/game/LauncherHelper.java

@@ -20,10 +20,7 @@ package org.jackhuang.hmcl.game;
 import com.jfoenix.concurrency.JFXUtilities;
 import javafx.application.Platform;
 import org.jackhuang.hmcl.Main;
-import org.jackhuang.hmcl.auth.Account;
+import org.jackhuang.hmcl.auth.*;
-import org.jackhuang.hmcl.auth.AuthInfo;
-import org.jackhuang.hmcl.auth.AuthenticationException;
-import org.jackhuang.hmcl.auth.SpecificCharacterSelector;
 import org.jackhuang.hmcl.download.DefaultDependencyManager;
 import org.jackhuang.hmcl.launch.*;
 import org.jackhuang.hmcl.mod.CurseCompletionTask;
@@ -91,6 +88,11 @@ public final class LauncherHelper {
                 .then(Task.of(Main.i18n("account.methods"), variables -> {
                     try {
                         variables.set("account", account.logIn(new SpecificCharacterSelector(Accounts.getCurrentCharacter(account)), Settings.INSTANCE.getProxy()));
+                    } catch (ServerDisconnectException e) {
+                        if (account.canPlayOffline())
+                            variables.set("account", account.playOffline());
+                        else
+                            throw e;
                     } catch (AuthenticationException e) {
                         variables.set("account", DialogController.logIn(account));
                         JFXUtilities.runInFX(() -> Controllers.dialog(launchingStepsPane));

HMCLCore/src/main/java/org/jackhuang/hmcl/auth/Account.java

@@ -57,6 +57,14 @@ public abstract class Account {
      */
     public abstract AuthInfo logIn(MultiCharacterSelector selector, Proxy proxy) throws AuthenticationException;
 
+    public abstract boolean canPlayOffline();
+
+    /**
+     * Play offline.
+     * @return the specific offline player's info.
+     */
+    public abstract AuthInfo playOffline();
+
     public abstract void logOut();
 
     protected abstract Map<Object, Object> toStorageImpl();

HMCLCore/src/main/java/org/jackhuang/hmcl/auth/OfflineAccount.java

@@ -69,6 +69,16 @@ public class OfflineAccount extends Account {
         // Offline account need not log out.
     }
 
+    @Override
+    public boolean canPlayOffline() {
+        return false;
+    }
+
+    @Override
+    public AuthInfo playOffline() {
+        throw new IllegalStateException();
+    }
+
     @Override
     public Map<Object, Object> toStorageImpl() {
         return Lang.mapOf(

HMCLCore/src/main/java/org/jackhuang/hmcl/auth/yggdrasil/YggdrasilAccount.java

@@ -171,6 +171,19 @@ public final class YggdrasilAccount extends Account {
             userProperties.putAll(user.getProperties());
     }
 
+    @Override
+    public boolean canPlayOffline() {
+        return isLoggedIn() && getSelectedProfile() != null && !canPlayOnline();
+    }
+
+    @Override
+    public AuthInfo playOffline() {
+        if (!canPlayOffline())
+            throw new IllegalStateException("Current account " + this + " cannot play offline.");
+
+        return new AuthInfo(selectedProfile, accessToken, userType, GSON.toJson(userProperties));
+    }
+
     @Override
     public void logOut() {
         password = null;