--- a/net/minecraft/server/MinecraftServer.java
+++ b/net/minecraft/server/MinecraftServer.java
@@ -151,6 +150,23 @@
 import net.minecraft.world.level.levelgen.WorldOptions;
 import net.minecraft.world.level.levelgen.feature.ConfiguredFeature;
 import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplateManager;
+import net.minecraft.world.level.storage.WorldData;
+import net.minecraft.world.level.storage.loot.LootDataManager;
+import org.slf4j.Logger;
+
+// CraftBukkit start
+import com.mojang.serialization.Dynamic;
+import com.mojang.serialization.Lifecycle;
+import java.util.Random;
+import jline.console.ConsoleReader;
+import joptsimple.OptionSet;
+import net.minecraft.nbt.NbtException;
+import net.minecraft.nbt.ReportedNbtException;
+import net.minecraft.server.bossevents.CustomBossEvents;
+import net.minecraft.server.dedicated.DedicatedServer;
+import net.minecraft.server.dedicated.DedicatedServerProperties;
+import net.minecraft.world.level.levelgen.WorldDimensions;
+import net.minecraft.world.level.levelgen.presets.WorldPresets;
 import net.minecraft.world.level.storage.CommandStorage;
 import net.minecraft.world.level.storage.DerivedLevelData;
 import net.minecraft.world.level.storage.DimensionDataStorage;
@@ -163,7 +180,11 @@
 import net.minecraft.world.level.storage.loot.LootDataManager;
 import net.minecraft.world.phys.Vec2;
 import net.minecraft.world.phys.Vec3;
-import org.slf4j.Logger;
+import org.bukkit.Bukkit;
+import org.bukkit.craftbukkit.CraftServer;
+import org.bukkit.craftbukkit.Main;
+import org.bukkit.event.server.ServerLoadEvent;
+// CraftBukkit end
 
 public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTask> implements ServerInfo, CommandSource, AutoCloseable {
 
@@ -171,7 +192,7 @@
     public static final String VANILLA_BRAND = "vanilla";
     private static final float AVERAGE_TICK_TIME_SMOOTHING = 0.8F;
     private static final int TICK_STATS_SPAN = 100;
-    private static final long OVERLOADED_THRESHOLD_NANOS = 20L * TimeUtil.NANOSECONDS_PER_SECOND / 20L;
+    private static final long OVERLOADED_THRESHOLD_NANOS = 30L * TimeUtil.NANOSECONDS_PER_SECOND / 20L; // CraftBukkit
     private static final int OVERLOADED_TICKS_THRESHOLD = 20;
     private static final long OVERLOADED_WARNING_INTERVAL_NANOS = 10L * TimeUtil.NANOSECONDS_PER_SECOND;
     private static final int OVERLOADED_TICKS_WARNING_INTERVAL = 100;
@@ -254,7 +275,20 @@
     protected final WorldData worldData;
     private volatile boolean isSaving;
 
-    public static <S extends MinecraftServer> S spin(Function<Thread, S> function) {
+    // CraftBukkit start
+    public final WorldLoader.a worldLoader;
+    public org.bukkit.craftbukkit.CraftServer server;
+    public OptionSet options;
+    public org.bukkit.command.ConsoleCommandSender console;
+    public ConsoleReader reader;
+    public static int currentTick = (int) (System.currentTimeMillis() / 50);
+    public java.util.Queue<Runnable> processQueue = new java.util.concurrent.ConcurrentLinkedQueue<Runnable>();
+    public int autosavePeriod;
+    public Commands vanillaCommandDispatcher;
+    private boolean forceTicks;
+    // CraftBukkit end
+
+    public static <S extends MinecraftServer> S spin(Function<Thread, S> threadFunction) {
         AtomicReference<S> atomicreference = new AtomicReference();
         Thread thread = new Thread(() -> {
             ((MinecraftServer) atomicreference.get()).runServer();
@@ -295,7 +329,7 @@
         this.customBossEvents = new CustomBossEvents();
         this.registries = worldstem.registries();
         this.worldData = worldstem.worldData();
-        if (!this.registries.compositeAccess().registryOrThrow(Registries.LEVEL_STEM).containsKey(LevelStem.OVERWORLD)) {
+        if (false && !this.registries.compositeAccess().registryOrThrow(Registries.LEVEL_STEM).containsKey(LevelStem.OVERWORLD)) { // CraftBukkit - initialised later
             throw new IllegalStateException("Missing Overworld dimension data");
         } else {
             this.proxy = proxy;
@@ -319,6 +353,33 @@
             this.serverThread = thread;
             this.executor = Util.backgroundExecutor();
         }
+        // CraftBukkit start
+        this.options = options;
+        this.worldLoader = worldLoader;
+        this.vanillaCommandDispatcher = worldstem.dataPackResources().commands; // CraftBukkit
+        // Try to see if we're actually running in a terminal, disable jline if not
+        if (System.console() == null && System.getProperty("jline.terminal") == null) {
+            System.setProperty("jline.terminal", "jline.UnsupportedTerminal");
+            Main.useJline = false;
+        }
+
+        try {
+            reader = new ConsoleReader(System.in, System.out);
+            reader.setExpandEvents(false); // Avoid parsing exceptions for uncommonly used event designators
+        } catch (Throwable e) {
+            try {
+                // Try again with jline disabled for Windows users without C++ 2008 Redistributable
+                System.setProperty("jline.terminal", "jline.UnsupportedTerminal");
+                System.setProperty("user.language", "en");
+                Main.useJline = false;
+                reader = new ConsoleReader(System.in, System.out);
+                reader.setExpandEvents(false);
+            } catch (IOException ex) {
+                LOGGER.warn((String) null, ex);
+            }
+        }
+        Runtime.getRuntime().addShutdownHook(new org.bukkit.craftbukkit.util.ServerShutdownThread(this));
+        // CraftBukkit end
     }
 
     private void readScoreboard(DimensionDataStorage dimensiondatastorage) {
@@ -327,7 +388,7 @@
 
     protected abstract boolean initServer() throws IOException;
 
-    protected void loadLevel() {
+    protected void loadLevel(String s) { // CraftBukkit
         if (!JvmProfiler.INSTANCE.isRunning()) {
             ;
         }
@@ -335,8 +396,7 @@
         boolean flag = false;
         ProfiledDuration profiledduration = JvmProfiler.INSTANCE.onWorldLoadedStarted();
 
-        this.worldData.setModdedInfo(this.getServerModName(), this.getModdedStatus().shouldReportAsModified());
-        ChunkProgressListener chunkprogresslistener = this.progressListenerFactory.create(11);
+        loadWorld0(s); // CraftBukkit
 
         this.createLevels(chunkprogresslistener);
         this.forceDifficulty();
@@ -357,16 +414,9 @@
 
     protected void forceDifficulty() {}
 
-    protected void createLevels(ChunkProgressListener chunkprogresslistener) {
-        ServerLevelData serverleveldata = this.worldData.overworldData();
-        boolean flag = this.worldData.isDebugWorld();
-        Registry<LevelStem> registry = this.registries.compositeAccess().registryOrThrow(Registries.LEVEL_STEM);
-        WorldOptions worldoptions = this.worldData.worldGenOptions();
-        long i = worldoptions.seed();
-        long j = BiomeManager.obfuscateSeed(i);
-        List<CustomSpawner> list = ImmutableList.of(new PhantomSpawner(), new PatrolSpawner(), new CatSpawner(), new VillageSiege(), new WanderingTraderSpawner(serverleveldata));
-        LevelStem levelstem = (LevelStem) registry.get(LevelStem.OVERWORLD);
-        ServerLevel serverlevel = new ServerLevel(this, this.executor, this.storageSource, serverleveldata, Level.OVERWORLD, levelstem, chunkprogresslistener, flag, j, list, true, (RandomSequences) null);
+    // CraftBukkit start
+    private void loadWorld0(String s) {
+        LevelStorageSource.LevelStorageAccess worldSession = this.storageSource;
 
         this.levels.put(Level.OVERWORLD, serverlevel);
         DimensionDataStorage dimensiondatastorage = serverlevel.getDataStorage();
@@ -375,7 +425,207 @@
         this.commandStorage = new CommandStorage(dimensiondatastorage);
         WorldBorder worldborder = serverlevel.getWorldBorder();
 
-        if (!serverleveldata.isInitialized()) {
+            if (dimensionKey == LevelStem.NETHER) {
+                if (isNetherEnabled()) {
+                    dimension = -1;
+                } else {
+                    continue;
+                }
+            } else if (dimensionKey == LevelStem.END) {
+                if (server.getAllowEnd()) {
+                    dimension = 1;
+                } else {
+                    continue;
+                }
+            } else if (dimensionKey != LevelStem.OVERWORLD) {
+                dimension = -999;
+            }
+
+            String worldType = (dimension == -999) ? dimensionKey.location().getNamespace() + "_" + dimensionKey.location().getPath() : org.bukkit.World.Environment.getEnvironment(dimension).toString().toLowerCase();
+            String name = (dimensionKey == LevelStem.OVERWORLD) ? s : s + "_" + worldType;
+            if (dimension != 0) {
+                File newWorld = LevelStorageSource.getStorageFolder(new File(name).toPath(), dimensionKey).toFile();
+                File oldWorld = LevelStorageSource.getStorageFolder(new File(s).toPath(), dimensionKey).toFile();
+                File oldLevelDat = new File(new File(s), "level.dat"); // The data folders exist on first run as they are created in the PersistentCollection constructor above, but the level.dat won't
+
+                if (!newWorld.isDirectory() && oldWorld.isDirectory() && oldLevelDat.isFile()) {
+                    MinecraftServer.LOGGER.info("---- Migration of old " + worldType + " folder required ----");
+                    MinecraftServer.LOGGER.info("Unfortunately due to the way that Minecraft implemented multiworld support in 1.6, Bukkit requires that you move your " + worldType + " folder to a new location in order to operate correctly.");
+                    MinecraftServer.LOGGER.info("We will move this folder for you, but it will mean that you need to move it back should you wish to stop using Bukkit in the future.");
+                    MinecraftServer.LOGGER.info("Attempting to move " + oldWorld + " to " + newWorld + "...");
+
+                    if (newWorld.exists()) {
+                        MinecraftServer.LOGGER.warn("A file or folder already exists at " + newWorld + "!");
+                        MinecraftServer.LOGGER.info("---- Migration of old " + worldType + " folder failed ----");
+                    } else if (newWorld.getParentFile().mkdirs()) {
+                        if (oldWorld.renameTo(newWorld)) {
+                            MinecraftServer.LOGGER.info("Success! To restore " + worldType + " in the future, simply move " + newWorld + " to " + oldWorld);
+                            // Migrate world data too.
+                            try {
+                                com.google.common.io.Files.copy(oldLevelDat, new File(new File(name), "level.dat"));
+                                org.apache.commons.io.FileUtils.copyDirectory(new File(new File(s), "data"), new File(new File(name), "data"));
+                            } catch (IOException exception) {
+                                MinecraftServer.LOGGER.warn("Unable to migrate world data.");
+                            }
+                            MinecraftServer.LOGGER.info("---- Migration of old " + worldType + " folder complete ----");
+                        } else {
+                            MinecraftServer.LOGGER.warn("Could not move folder " + oldWorld + " to " + newWorld + "!");
+                            MinecraftServer.LOGGER.info("---- Migration of old " + worldType + " folder failed ----");
+                        }
+                    } else {
+                        MinecraftServer.LOGGER.warn("Could not create path for " + newWorld + "!");
+                        MinecraftServer.LOGGER.info("---- Migration of old " + worldType + " folder failed ----");
+                    }
+                }
+
+                try {
+                    worldSession = LevelStorageSource.createDefault(server.getWorldContainer().toPath()).validateAndCreateAccess(name, dimensionKey);
+                } catch (IOException | ContentValidationException ex) {
+                    throw new RuntimeException(ex);
+                }
+            }
+
+            Dynamic<?> dynamic;
+            if (worldSession.hasWorldData()) {
+                LevelSummary worldinfo;
+
+                try {
+                    dynamic = worldSession.getDataTag();
+                    worldinfo = worldSession.getSummary(dynamic);
+                } catch (NbtException | ReportedNbtException | IOException ioexception) {
+                    LevelStorageSource.LevelDirectory convertable_b = worldSession.getLevelDirectory();
+
+                    MinecraftServer.LOGGER.warn("Failed to load world data from {}", convertable_b.dataFile(), ioexception);
+                    MinecraftServer.LOGGER.info("Attempting to use fallback");
+
+                    try {
+                        dynamic = worldSession.getDataTagFallback();
+                        worldinfo = worldSession.getSummary(dynamic);
+                    } catch (NbtException | ReportedNbtException | IOException ioexception1) {
+                        MinecraftServer.LOGGER.error("Failed to load world data from {}", convertable_b.oldDataFile(), ioexception1);
+                        MinecraftServer.LOGGER.error("Failed to load world data from {} and {}. World files may be corrupted. Shutting down.", convertable_b.dataFile(), convertable_b.oldDataFile());
+                        return;
+                    }
+
+                    worldSession.restoreLevelDataFromOld();
+                }
+
+                if (worldinfo.requiresManualConversion()) {
+                    MinecraftServer.LOGGER.info("This world must be opened in an older version (like 1.6.4) to be safely converted");
+                    return;
+                }
+
+                if (!worldinfo.isCompatible()) {
+                    MinecraftServer.LOGGER.info("This world was created by an incompatible version.");
+                    return;
+                }
+            } else {
+                dynamic = null;
+            }
+
+            org.bukkit.generator.ChunkGenerator gen = this.server.getGenerator(name);
+            org.bukkit.generator.BiomeProvider biomeProvider = this.server.getBiomeProvider(name);
+
+            PrimaryLevelData worlddata;
+            WorldLoader.a worldloader_a = this.worldLoader;
+            Registry<LevelStem> iregistry = worldloader_a.datapackDimensions().registryOrThrow(Registries.LEVEL_STEM);
+            if (dynamic != null) {
+                LevelDataAndDimensions leveldataanddimensions = LevelStorageSource.getLevelDataAndDimensions(dynamic, worldloader_a.dataConfiguration(), iregistry, worldloader_a.datapackWorldgen());
+
+                worlddata = (PrimaryLevelData) leveldataanddimensions.worldData();
+            } else {
+                LevelSettings worldsettings;
+                WorldOptions worldoptions;
+                WorldDimensions worlddimensions;
+
+                if (this.isDemo()) {
+                    worldsettings = MinecraftServer.DEMO_SETTINGS;
+                    worldoptions = WorldOptions.DEMO_OPTIONS;
+                    worlddimensions = WorldPresets.createNormalWorldDimensions(worldloader_a.datapackWorldgen());
+                } else {
+                    DedicatedServerProperties dedicatedserverproperties = ((DedicatedServer) this).getProperties();
+
+                    worldsettings = new LevelSettings(dedicatedserverproperties.levelName, dedicatedserverproperties.gamemode, dedicatedserverproperties.hardcore, dedicatedserverproperties.difficulty, false, new GameRules(), worldloader_a.dataConfiguration());
+                    worldoptions = options.has("bonusChest") ? dedicatedserverproperties.worldOptions.withBonusChest(true) : dedicatedserverproperties.worldOptions;
+                    worlddimensions = dedicatedserverproperties.createDimensions(worldloader_a.datapackWorldgen());
+                }
+
+                WorldDimensions.b worlddimensions_b = worlddimensions.bake(iregistry);
+                Lifecycle lifecycle = worlddimensions_b.lifecycle().add(worldloader_a.datapackWorldgen().allRegistriesLifecycle());
+
+                worlddata = new PrimaryLevelData(worldsettings, worldoptions, worlddimensions_b.specialWorldProperty(), lifecycle);
+            }
+            worlddata.checkName(name); // CraftBukkit - Migration did not rewrite the level.dat; This forces 1.8 to take the last loaded world as respawn (in this case the end)
+            if (options.has("forceUpgrade")) {
+                net.minecraft.server.Main.forceUpgrade(worldSession, DataFixers.getDataFixer(), options.has("eraseCache"), () -> {
+                    return true;
+                }, dimensions);
+            }
+
+            PrimaryLevelData iworlddataserver = worlddata;
+            boolean flag = worlddata.isDebugWorld();
+            WorldOptions worldoptions = worlddata.worldGenOptions();
+            long i = worldoptions.seed();
+            long j = BiomeManager.obfuscateSeed(i);
+            List<CustomSpawner> list = ImmutableList.of(new MobSpawnerPhantom(), new PatrolSpawner(), new CatSpawner(), new VillageSiege(), new WanderingTraderSpawner(iworlddataserver));
+            LevelStem worlddimension = (LevelStem) dimensions.get(dimensionKey);
+
+            org.bukkit.generator.WorldInfo worldInfo = new org.bukkit.craftbukkit.generator.CraftWorldInfo(iworlddataserver, worldSession, org.bukkit.World.Environment.getEnvironment(dimension), worlddimension.type().value());
+            if (biomeProvider == null && gen != null) {
+                biomeProvider = gen.getDefaultBiomeProvider(worldInfo);
+            }
+
+            ResourceKey<Level> worldKey = ResourceKey.create(Registries.DIMENSION, dimensionKey.location());
+
+            if (dimensionKey == LevelStem.OVERWORLD) {
+                this.worldData = worlddata;
+                this.worldData.setGameType(((DedicatedServer) this).getProperties().gamemode); // From DedicatedServer.init
+
+                ChunkProgressListener worldloadlistener = this.progressListenerFactory.create(11);
+
+                world = new ServerLevel(this, this.executor, worldSession, iworlddataserver, worldKey, worlddimension, worldloadlistener, flag, j, list, true, (RandomSequences) null, org.bukkit.World.Environment.getEnvironment(dimension), gen, biomeProvider);
+                DimensionDataStorage worldpersistentdata = world.getDataStorage();
+                this.readScoreboard(worldpersistentdata);
+                this.server.scoreboardManager = new org.bukkit.craftbukkit.scoreboard.CraftScoreboardManager(this, world.getScoreboard());
+                this.commandStorage = new CommandStorage(worldpersistentdata);
+            } else {
+                ChunkProgressListener worldloadlistener = this.progressListenerFactory.create(11);
+                world = new ServerLevel(this, this.executor, worldSession, iworlddataserver, worldKey, worlddimension, worldloadlistener, flag, j, ImmutableList.of(), true, this.overworld().getRandomSequences(), org.bukkit.World.Environment.getEnvironment(dimension), gen, biomeProvider);
+            }
+
+            worlddata.setModdedInfo(this.getServerModName(), this.getModdedStatus().shouldReportAsModified());
+            this.initWorld(world, worlddata, worldData, worldoptions);
+
+            this.addLevel(world);
+            this.getPlayerList().addWorldborderListener(world);
+
+            if (worlddata.getCustomBossEvents() != null) {
+                this.getCustomBossEvents().load(worlddata.getCustomBossEvents());
+            }
+        }
+        this.forceDifficulty();
+        for (ServerLevel worldserver : this.getAllLevels()) {
+            this.prepareLevels(worldserver.getChunkSource().chunkMap.progressListener, worldserver);
+            worldserver.entityManager.tick(); // SPIGOT-6526: Load pending entities so they are available to the API
+            this.server.getPluginManager().callEvent(new org.bukkit.event.world.WorldLoadEvent(worldserver.getWorld()));
+        }
+
+        this.server.enablePlugins(org.bukkit.plugin.PluginLoadOrder.POSTWORLD);
+        this.server.getPluginManager().callEvent(new ServerLoadEvent(ServerLoadEvent.LoadType.STARTUP));
+        this.connection.acceptConnections();
+    }
+
+    public void initWorld(ServerLevel worldserver, ServerLevelData iworlddataserver, WorldData saveData, WorldOptions worldoptions) {
+        boolean flag = saveData.isDebugWorld();
+        // CraftBukkit start
+        if (worldserver.generator != null) {
+            worldserver.getWorld().getPopulators().addAll(worldserver.generator.getDefaultPopulators(worldserver.getWorld()));
+        }
+        WorldBorder worldborder = worldserver.getWorldBorder();
+        worldborder.applySettings(iworlddataserver.getWorldBorder()); // CraftBukkit - move up so that WorldBorder is set during WorldInitEvent
+        this.server.getPluginManager().callEvent(new org.bukkit.event.world.WorldInitEvent(worldserver.getWorld())); // CraftBukkit - SPIGOT-5569: Call WorldInitEvent before any chunks are generated
+
+        if (!iworlddataserver.isInitialized()) {
             try {
                 setInitialSpawn(serverlevel, serverleveldata, worldoptions.generateBonusChest(), flag);
                 serverleveldata.setInitialized(true);
@@ -421,17 +648,30 @@
 
         worldborder.applySettings(serverleveldata.getWorldBorder());
     }
+    // CraftBukkit end
 
     private static void setInitialSpawn(ServerLevel serverlevel, ServerLevelData serverleveldata, boolean flag, boolean flag1) {
         if (flag1) {
             serverleveldata.setSpawn(BlockPos.ZERO.above(80), 0.0F);
         } else {
-            ServerChunkCache serverchunkcache = serverlevel.getChunkSource();
-            ChunkPos chunkpos = new ChunkPos(serverchunkcache.randomState().sampler().findSpawnPosition());
-            int i = serverchunkcache.getGenerator().getSpawnHeight(serverlevel);
+            ServerChunkCache chunkproviderserver = level.getChunkSource();
+            ChunkPos chunkcoordintpair = new ChunkPos(chunkproviderserver.randomState().sampler().findSpawnPosition());
+            // CraftBukkit start
+            if (level.generator != null) {
+                Random rand = new Random(level.getSeed());
+                org.bukkit.Location spawn = level.generator.getFixedSpawnLocation(level.getWorld(), rand);
 
-            if (i < serverlevel.getMinBuildHeight()) {
-                BlockPos blockpos = chunkpos.getWorldPosition();
+                if (spawn != null) {
+                    if (spawn.getWorld() != level.getWorld()) {
+                        throw new IllegalStateException("Cannot set spawn point for " + levelData.getLevelName() + " to be in another world (" + spawn.getWorld().getName() + ")");
+                    } else {
+                        levelData.setSpawn(new BlockPos(spawn.getBlockX(), spawn.getBlockY(), spawn.getBlockZ()), spawn.getYaw());
+                        return;
+                    }
+                }
+            }
+            // CraftBukkit end
+            int i = chunkproviderserver.getGenerator().getSpawnHeight(level);
 
                 i = serverlevel.getHeight(Heightmap.Types.WORLD_SURFACE, blockpos.getX() + 8, blockpos.getZ() + 8);
             }
@@ -487,8 +730,11 @@
         serverleveldata.setGameType(GameType.SPECTATOR);
     }
 
-    private void prepareLevels(ChunkProgressListener chunkprogresslistener) {
-        ServerLevel serverlevel = this.overworld();
+    // CraftBukkit start
+    public void prepareLevels(ChunkProgressListener worldloadlistener, ServerLevel worldserver) {
+        // WorldServer worldserver = this.overworld();
+        this.forceTicks = true;
+        // CraftBukkit end
 
         MinecraftServer.LOGGER.info("Preparing start region for dimension {}", serverlevel.dimension().location());
         BlockPos blockpos = serverlevel.getSharedSpawnPos();
@@ -497,7 +743,9 @@
         ServerChunkCache serverchunkcache = serverlevel.getChunkSource();
 
         this.nextTickTimeNanos = Util.getNanos();
-        serverchunkcache.addRegionTicket(TicketType.START, new ChunkPos(blockpos), 11, Unit.INSTANCE);
+        // CraftBukkit start
+        if (worldserver.getWorld().getKeepSpawnInMemory()) {
+            chunkproviderserver.addRegionTicket(TicketType.START, new ChunkPos(blockposition), 11, Unit.INSTANCE);
 
         while (serverchunkcache.getTickingGenerated() != 441) {
             this.nextTickTimeNanos = Util.getNanos() + MinecraftServer.PREPARE_LEVELS_DEFAULT_DELAY_NANOS;
@@ -508,9 +757,10 @@
         this.waitUntilNextTick();
         Iterator iterator = this.levels.values().iterator();
 
-        while (iterator.hasNext()) {
-            ServerLevel serverlevel1 = (ServerLevel) iterator.next();
-            ForcedChunksSavedData forcedchunkssaveddata = (ForcedChunksSavedData) serverlevel1.getDataStorage().get(ForcedChunksSavedData.factory(), "chunks");
+        if (true) {
+            ServerLevel worldserver1 = worldserver;
+            // CraftBukkit end
+            ForcedChunksSavedData forcedchunk = (ForcedChunksSavedData) worldserver1.getDataStorage().get(ForcedChunksSavedData.factory(), "chunks");
 
             if (forcedchunkssaveddata != null) {
                 LongIterator longiterator = forcedchunkssaveddata.getChunks().iterator();
@@ -524,10 +774,17 @@
             }
         }
 
-        this.nextTickTimeNanos = Util.getNanos() + MinecraftServer.PREPARE_LEVELS_DEFAULT_DELAY_NANOS;
-        this.waitUntilNextTick();
-        chunkprogresslistener.stop();
-        this.updateMobSpawningFlags();
+        // CraftBukkit start
+        // this.nextTickTimeNanos = SystemUtils.getNanos() + MinecraftServer.PREPARE_LEVELS_DEFAULT_DELAY_NANOS;
+        this.executeModerately();
+        // CraftBukkit end
+        worldloadlistener.stop();
+        // CraftBukkit start
+        // this.updateMobSpawningFlags();
+        worldserver.setSpawnSettings(this.isSpawningMonsters(), this.isSpawningAnimals());
+
+        this.forceTicks = false;
+        // CraftBukkit end
     }
 
     public GameType getDefaultGameType() {
@@ -557,13 +814,17 @@
             serverlevel.save((ProgressListener) null, flag1, serverlevel.noSave && !flag2);
         }
 
-        ServerLevel serverlevel1 = this.overworld();
-        ServerLevelData serverleveldata = this.worldData.overworldData();
+        // CraftBukkit start - moved to WorldServer.save
+        /*
+        WorldServer worldserver1 = this.overworld();
+        IWorldDataServer iworlddataserver = this.worldData.overworldData();
 
         serverleveldata.setWorldBorder(serverlevel1.getWorldBorder().createSettings());
         this.worldData.setCustomBossEvents(this.getCustomBossEvents().save());
         this.storageSource.saveDataTag(this.registryAccess(), this.worldData, this.getPlayerList().getSingleplayerData());
-        if (flag1) {
+        */
+        // CraftBukkit end
+        if (flush) {
             Iterator iterator1 = this.getAllLevels().iterator();
 
             while (iterator1.hasNext()) {
@@ -598,18 +858,40 @@
         this.stopServer();
     }
 
+    // CraftBukkit start
+    private boolean hasStopped = false;
+    private final Object stopLock = new Object();
+    public final boolean hasStopped() {
+        synchronized (stopLock) {
+            return hasStopped;
+        }
+    }
+    // CraftBukkit end
+
     public void stopServer() {
+        // CraftBukkit start - prevent double stopping on multiple threads
+        synchronized(stopLock) {
+            if (hasStopped) return;
+            hasStopped = true;
+        }
+        // CraftBukkit end
         if (this.metricsRecorder.isRecording()) {
             this.cancelRecordingMetrics();
         }
 
         MinecraftServer.LOGGER.info("Stopping server");
+        // CraftBukkit start
+        if (this.server != null) {
+            this.server.disablePlugins();
+        }
+        // CraftBukkit end
         this.getConnection().stop();
         this.isSaving = true;
         if (this.playerList != null) {
             MinecraftServer.LOGGER.info("Saving players");
             this.playerList.saveAll();
             this.playerList.removeAll();
+            try { Thread.sleep(100); } catch (InterruptedException ex) {} // CraftBukkit - SPIGOT-625 - give server at least a chance to send packets
         }
 
         MinecraftServer.LOGGER.info("Saving worlds");
@@ -714,6 +996,7 @@
                     if (j > MinecraftServer.OVERLOADED_THRESHOLD_NANOS + 20L * i && this.nextTickTimeNanos - this.lastOverloadWarningNanos >= MinecraftServer.OVERLOADED_WARNING_INTERVAL_NANOS + 100L * i) {
                         long k = j / i;
 
+                        if (server.getWarnOnOverload()) // CraftBukkit
                         MinecraftServer.LOGGER.warn("Can't keep up! Is the server overloaded? Running {}ms or {} ticks behind", j / TimeUtil.NANOSECONDS_PER_MILLISECOND, k);
                         this.nextTickTimeNanos += k * i;
                         this.lastOverloadWarningNanos = this.nextTickTimeNanos;
@@ -727,6 +1010,7 @@
                     this.debugCommandProfiler = new MinecraftServer.TimeProfiler(Util.getNanos(), this.tickCount);
                 }
 
+                MinecraftServer.currentTick = (int) (System.currentTimeMillis() / 50); // CraftBukkit
                 this.nextTickTimeNanos += i;
                 this.startMetricsRecordingTick();
                 this.profiler.push("tick");
@@ -771,6 +1055,12 @@
                     this.services.profileCache().clearExecutor();
                 }
 
+                // CraftBukkit start - Restore terminal to original settings
+                try {
+                    reader.getTerminal().restore();
+                } catch (Exception ignored) {
+                }
+                // CraftBukkit end
                 this.onServerExit();
             }
 
@@ -804,9 +1094,16 @@
     }
 
     private boolean haveTime() {
-        return this.runningTask() || Util.getNanos() < (this.mayHaveDelayedTasks ? this.delayedTasksMaxNextTickTimeNanos : this.nextTickTimeNanos);
+        // CraftBukkit start
+        return this.forceTicks || this.runningTask() || Util.getNanos() < (this.mayHaveDelayedTasks ? this.delayedTasksMaxNextTickTimeNanos : this.nextTickTimeNanos);
     }
 
+    private void executeModerately() {
+        this.runAllTasks();
+        java.util.concurrent.locks.LockSupport.parkNanos("executing tasks", 1000L);
+        // CraftBukkit end
+    }
+
     protected void waitUntilNextTick() {
         this.runAllTasks();
         this.managedBlock(() -> {
@@ -914,8 +1207,10 @@
         }
 
         --this.ticksUntilAutosave;
-        if (this.ticksUntilAutosave <= 0) {
-            this.ticksUntilAutosave = this.computeNextAutosaveInterval();
+        // CraftBukkit start
+        if (this.autosavePeriod > 0 && this.ticksUntilAutosave <= 0) {
+            this.ticksUntilAutosave = this.autosavePeriod;
+            // CraftBukkit end
             MinecraftServer.LOGGER.debug("Autosave started");
             this.profiler.push("save");
             this.saveEverything(true, false, false);
@@ -996,11 +1291,26 @@
         this.getPlayerList().getPlayers().forEach((serverplayer) -> {
             serverplayer.connection.suspendFlushing();
         });
+        this.server.getScheduler().mainThreadHeartbeat(this.tickCount); // CraftBukkit
         this.profiler.push("commandFunctions");
         this.getFunctions().tick();
         this.profiler.popPush("levels");
         Iterator iterator = this.getAllLevels().iterator();
 
+        // CraftBukkit start
+        // Run tasks that are waiting on processing
+        while (!processQueue.isEmpty()) {
+            processQueue.remove().run();
+        }
+
+        // Send time updates to everyone, it will get the right time from the world the player is in.
+        if (this.tickCount % 20 == 0) {
+            for (int i = 0; i < this.getPlayerList().players.size(); ++i) {
+                ServerPlayer entityplayer = (ServerPlayer) this.getPlayerList().players.get(i);
+                entityplayer.connection.send(new ClientboundSetTimePacket(entityplayer.level().getGameTime(), entityplayer.getPlayerTime(), entityplayer.level().getGameRules().getBoolean(GameRules.RULE_DAYLIGHT))); // Add support for per player time
+            }
+        }
+
         while (iterator.hasNext()) {
             ServerLevel serverlevel = (ServerLevel) iterator.next();
 
@@ -1012,6 +1323,7 @@
                 this.synchronizeTime(serverlevel);
                 this.profiler.pop();
             }
+            // CraftBukkit end */
 
             this.profiler.push("tick");
 
@@ -1101,6 +1413,22 @@
         return (ServerLevel) this.levels.get(resourcekey);
     }
 
+    // CraftBukkit start
+    public void addLevel(ServerLevel level) {
+        Map<ResourceKey<Level>, ServerLevel> oldLevels = this.levels;
+        Map<ResourceKey<Level>, ServerLevel> newLevels = Maps.newLinkedHashMap(oldLevels);
+        newLevels.put(level.dimension(), level);
+        this.levels = Collections.unmodifiableMap(newLevels);
+    }
+
+    public void removeLevel(ServerLevel level) {
+        Map<ResourceKey<Level>, ServerLevel> oldLevels = this.levels;
+        Map<ResourceKey<Level>, ServerLevel> newLevels = Maps.newLinkedHashMap(oldLevels);
+        newLevels.remove(level.dimension());
+        this.levels = Collections.unmodifiableMap(newLevels);
+    }
+    // CraftBukkit end
+
     public Set<ResourceKey<Level>> levelKeys() {
         return this.levels.keySet();
     }
@@ -1133,7 +1458,7 @@
 
     @DontObfuscate
     public String getServerModName() {
-        return "vanilla";
+        return server.getName(); // CraftBukkit - cb > vanilla!
     }
 
     public SystemReport fillSystemReport(SystemReport systemreport) {
@@ -1920,6 +2237,22 @@
 
     }
 
+    // CraftBukkit start
+    @Override
+    public boolean isSameThread() {
+        return super.isSameThread() || this.isStopped(); // CraftBukkit - MC-142590
+    }
+
+    public boolean isDebugging() {
+        return false;
+    }
+
+    @Deprecated
+    public static MinecraftServer getServer() {
+        return (Bukkit.getServer() instanceof CraftServer) ? ((CraftServer) Bukkit.getServer()).getServer() : null;
+    }
+    // CraftBukkit end
+
     private void startMetricsRecordingTick() {
         if (this.willStartRecordingMetrics) {
             this.metricsRecorder = ActiveMetricsRecorder.createStarted(new ServerMetricsSamplersProvider(Util.timeSource, this.isDedicatedServer()), Util.timeSource, Util.ioPool(), new MetricsPersister("server"), this.onMetricsRecordingStopped, (path) -> {
@@ -2046,6 +2379,11 @@
 
     }
 
+    // CraftBukkit start
+    public final java.util.concurrent.ExecutorService chatExecutor = java.util.concurrent.Executors.newCachedThreadPool(
+            new com.google.common.util.concurrent.ThreadFactoryBuilder().setDaemon(true).setNameFormat("Async Chat Thread - #%d").build());
+    // CraftBukkit end
+
     public ChatDecorator getChatDecorator() {
         return ChatDecorator.PLAIN;
     }