Resolve NeoForge equivilent of '#261 autoback (backup after autosaves) is not currently supported on Forge'

Mixins are used in much the same way they are in the fabric version.

Author: stewi1014

neoforge/src/main/java/net/pcal/fastback/mod/neoforge/ForgeCommonProvider.java

@@ -9,6 +9,7 @@
 import net.minecraft.world.level.storage.LevelResource;
 import net.neoforged.neoforge.common.NeoForge;
 import net.neoforged.neoforge.event.RegisterCommandsEvent;
+import net.neoforged.neoforge.event.level.LevelEvent;
 import net.neoforged.neoforge.event.server.ServerStartedEvent;
 import net.neoforged.neoforge.event.server.ServerStoppingEvent;
 import net.neoforged.bus.api.IEventBus;
@@ -35,13 +36,13 @@
  * @author pcal
  * @since 0.16.0
  */
-class ForgeCommonProvider implements MinecraftProvider {
+class ForgeCommonProvider implements MinecraftProvider, MixinGateway {
 
     static final String MOD_ID = "fastback";
     private MinecraftServer logicalServer;
     private LifecycleListener lifecycleListener = null;
     private Runnable autoSaveListener;
-    private boolean isWorldSaveEnabled;
+    private boolean isWorldSaveEnabled = true;
 
     ForgeCommonProvider() {
         final IEventBus modEventBus = ModLoadingContext.get().getActiveContainer().getEventBus();
@@ -76,15 +77,6 @@ private void onRegisterCommandEvent(RegisterCommandsEvent event) {
         commandDispatcher.register(backupCommand);
     }
 
-    /**
-     TODO This one isn't it.  We need to hear about it when an autosaves (and only autosaves) are completed.
-     Might have to delve into Forge mixins to do this.
-     private void onLevelSaveEvent(LevelEvent.Save event) {
-     provider.onAutoSaveComplete();
-     }
-     **/
-
-
     // ======================================================================
     // Protected
 
@@ -104,6 +96,7 @@ void onInitialize() {
         syslog().warn("Please note that this is an alpha release.  A list of known issues is available here:");
         syslog().warn("https://github.com/pcal43/fastback/issues?q=is%3Aissue+is%3Aopen+label%3Aforge");
         syslog().warn("------------------------------------------------------------------------------------");
+        MixinGateway.Singleton.register(this);
     }
 
 
@@ -135,25 +128,32 @@ public String getModVersion() {
         return "0.15.3+1.20.1-alpha"; //FIXME
     }
 
-    //FIXME!!
-    void onAutoSaveComplete() {
-        syslog().debug("onAutoSaveComplete");
+    @Override
+    public void autoSaveCompleted() {
+        syslog().debug("autoSaveCompleted");
         this.autoSaveListener.run();
     }
 
     @Override
     public Path getWorldDirectory() {
-        if (this.logicalServer == null) throw new IllegalStateException("minecraftServer is null");
+        if (logicalServer == null) throw new IllegalStateException("minecraftServer is null");
         return logicalServer.getWorldPath(LevelResource.ROOT).toAbsolutePath().normalize();
     }
 
     @Override
     public void setWorldSaveEnabled(boolean enabled) {
+        isWorldSaveEnabled = enabled;
+        if (logicalServer == null) throw new IllegalStateException("minecraftServer is null");
         for (ServerLevel world : logicalServer.getAllLevels()) {
             world.noSave = !enabled;
         }
     }
 
+    @Override
+    public boolean isWorldSaveEnabled() {
+        return isWorldSaveEnabled;
+    }
+
     @Override
     public void saveWorld() {
         if (this.logicalServer == null) throw new IllegalStateException();
@@ -215,5 +215,4 @@ public Collection<Path> getModsBackupPaths() {
          **/
         return out;
     }
-
 }

neoforge/src/main/java/net/pcal/fastback/mod/neoforge/MixinGateway.java

@@ -0,0 +1,44 @@
+/*
+ * FastBack - Fast, incremental Minecraft backups powered by Git.
+ * Copyright (C) 2022 pcal.net
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package net.pcal.fastback.mod.neoforge;
+
+/**
+ * Singleton 'gateway' that mixin code goes through to call back into the mod.
+ *
+ * @author pcal
+ * @since 0.13.1
+ */
+public interface MixinGateway {
+
+    static MixinGateway get() {
+        return Singleton.INSTANCE;
+    }
+
+    boolean isWorldSaveEnabled();
+
+    void autoSaveCompleted();
+
+    class Singleton {
+        private static MixinGateway INSTANCE = null;
+
+        public static void register(MixinGateway gateway) {
+            Singleton.INSTANCE = gateway;
+        }
+    }
+}

neoforge/src/main/java/net/pcal/fastback/mod/neoforge/mixins/MinecraftServerMixin.java

@@ -0,0 +1,84 @@
+/*
+ * FastBack - Fast, incremental Minecraft backups powered by Git.
+ * Copyright (C) 2022 pcal.net
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; If not, see <http://www.gnu.org/licenses/>.
+ */
+package net.pcal.fastback.mod.neoforge.mixins;
+
+import net.minecraft.server.MinecraftServer;
+import net.pcal.fastback.mod.neoforge.MixinGateway;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.Redirect;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+
+import static net.pcal.fastback.logging.SystemLogger.syslog;
+
+/**
+ * Allows us to disable vanilla saving during 'git add' to avoid coherency problems in the backup snapshots.  Also
+ * sends notifications when autosaving completes so we can follow them with automated backups.
+ *
+ * @author pcal
+ * @since 0.0.1
+ */
+@Mixin(MinecraftServer.class)
+public class MinecraftServerMixin {
+
+    /**
+     * Intercept the call to saveAll that triggers on autosave, pass it through and then send out notification that
+     * the autosave is done.
+     */
+    @Redirect(method = "autoSave()V",
+            at = @At(value = "INVOKE", target = "Lnet/minecraft/server/MinecraftServer;saveEverything(ZZZ)Z"))
+    public boolean fastback_saveAll(MinecraftServer instance, boolean suppressLogs, boolean flush, boolean force) {
+        boolean result = instance.saveEverything(suppressLogs, flush, force);
+        MixinGateway.get().autoSaveCompleted();
+        return result;
+    }
+
+    /**
+     * Intercept save so we can hard-disable saving during critical parts of the backup.
+     */
+    @Inject(at = @At("HEAD"), method = "saveAllChunks(ZZZ)Z", cancellable = true)
+    public void fastback_save(boolean suppressLogs, boolean flush, boolean force, CallbackInfoReturnable<Boolean> ci) {
+        synchronized (this) {
+            if (MixinGateway.get().isWorldSaveEnabled()) {
+                syslog().debug("world saves are enabled, doing requested save");
+            } else {
+                syslog().warn("Skipping requested save because a backup is in progress.");
+                ci.setReturnValue(false);
+                ci.cancel();
+            }
+        }
+    }
+
+    /**
+     * Intercept saveAll so we can hard-disable saving during critical parts of the backup.
+     */
+    @Inject(at = @At("HEAD"), method = "saveEverything(ZZZ)Z", cancellable = true)
+    public void fastback_saveAll(boolean suppressLogs, boolean flush, boolean force, CallbackInfoReturnable<Boolean> ci) {
+        synchronized (this) {
+            if (MixinGateway.get().isWorldSaveEnabled()) {
+                syslog().debug("world saves are enabled, doing requested saveAll");
+                //TODO should call save here to ensure all synced?
+            } else {
+                syslog().warn("Skipping requested saveAll because a backup is in progress.");
+                ci.setReturnValue(false);
+                ci.cancel();
+            }
+        }
+    }
+}

neoforge/src/main/resources/META-INF/neoforge.mods.toml

@@ -27,3 +27,6 @@ mandatory = true
 versionRange = "1.21.3"
 ordering = "NONE"
 side = "CLIENT"
+
+[[mixins]]
+config="fastback.mixins.json"

neoforge/src/main/resources/fastback.mixins.json

@@ -0,0 +1,12 @@
+{
+  "required": true,
+  "minVersion": "0.8",
+  "package": "net.pcal.fastback.mod.neoforge.mixins",
+  "compatibilityLevel": "JAVA_16",
+  "mixins": [
+    "MinecraftServerMixin"
+  ],
+  "injectors": {
+    "defaultRequire": 1
+  }
+}