light.patch

diff --git a/src/main/java/net/minecraft/server/LightEngineThreaded.java b/src/main/java/net/minecraft/server/LightEngineThreaded.java
index 721f86a5405..e8223670017 100644
--- a/src/main/java/net/minecraft/server/LightEngineThreaded.java
+++ b/src/main/java/net/minecraft/server/LightEngineThreaded.java
@@ -17,9 +17,10 @@ public class LightEngineThreaded extends LightEngine implements AutoCloseable {
     private final ThreadedMailbox<Runnable> b; ThreadedMailbox<Runnable> mailbox; // Paper
     // Paper start
     private static final int MAX_PRIORITIES = PlayerChunkMap.GOLDEN_TICKET + 2;
+    private final java.util.concurrent.ConcurrentLinkedQueue<Runnable> priorityChanges = new java.util.concurrent.ConcurrentLinkedQueue<>();
 
     public void changePriority(long pair, int currentPriority, int priority) {
-        this.mailbox.queue(() -> {
+        this.priorityChanges.add(() -> {
             ChunkLightQueue remove = this.queue.buckets[currentPriority].remove(pair);
             if (remove != null) {
                 ChunkLightQueue existing = this.queue.buckets[priority].put(pair, remove);
@@ -31,6 +32,15 @@ public class LightEngineThreaded extends LightEngine implements AutoCloseable {
         });
     }
 
+    private boolean isChunkLightStatus(long pair) {
+        PlayerChunk playerChunk = playerChunkMap.getUpdatingChunk(pair);
+        if (playerChunk == null) {
+            return false;
+        }
+        ChunkStatus status = PlayerChunk.getChunkStatus(playerChunk.getTicketLevel());
+        return status != null && status.isAtLeastStatus(ChunkStatus.LIGHT);
+    }
+
     static class ChunkLightQueue {
         public boolean shouldFastUpdate;
         java.util.ArrayDeque<Runnable> pre = new java.util.ArrayDeque<Runnable>();
@@ -41,7 +51,7 @@ public class LightEngineThreaded extends LightEngine implements AutoCloseable {
 
 
     // Retain the chunks priority level for queued light tasks
-    private static class LightQueue {
+    private class LightQueue {
         private int size = 0;
         private int lowestPriority = MAX_PRIORITIES;
         private final it.unimi.dsi.fastutil.longs.Long2ObjectLinkedOpenHashMap<ChunkLightQueue>[] buckets = new it.unimi.dsi.fastutil.longs.Long2ObjectLinkedOpenHashMap[MAX_PRIORITIES];
@@ -81,6 +91,10 @@ public class LightEngineThreaded extends LightEngine implements AutoCloseable {
         }
 
         public boolean poll(java.util.List<Runnable> pre, java.util.List<Runnable> post) {
+            Runnable run;
+            while ((run = priorityChanges.poll()) != null) {
+                run.run();
+            }
             boolean hasWork = false;
             it.unimi.dsi.fastutil.longs.Long2ObjectLinkedOpenHashMap<ChunkLightQueue>[] buckets = this.buckets;
             while (lowestPriority < MAX_PRIORITIES && !isEmpty()) {
@@ -106,14 +120,14 @@ public class LightEngineThreaded extends LightEngine implements AutoCloseable {
 
     private final LightQueue queue = new LightQueue();
     // Paper end
-    private final PlayerChunkMap d;
+    private final PlayerChunkMap d; private final PlayerChunkMap playerChunkMap; // Paper
     private final Mailbox<ChunkTaskQueueSorter.a<Runnable>> e;
     private volatile int f = 5;
     private final AtomicBoolean g = new AtomicBoolean();
 
     public LightEngineThreaded(ILightAccess ilightaccess, PlayerChunkMap playerchunkmap, boolean flag, ThreadedMailbox<Runnable> threadedmailbox, Mailbox<ChunkTaskQueueSorter.a<Runnable>> mailbox) {
         super(ilightaccess, true, flag);
-        this.d = playerchunkmap;
+        this.d = playerchunkmap; this.playerChunkMap = d; // Paper
         this.e = mailbox;
         this.mailbox = this.b = threadedmailbox; // Paper
     }
@@ -203,11 +217,8 @@ public class LightEngineThreaded extends LightEngine implements AutoCloseable {
         this.e.a(ChunkTaskQueueSorter.a(() -> {
             // Paper start
             int priority = intsupplier.getAsInt();
-            this.queue.add(ChunkCoordIntPair.pair(i, j), priority, lightenginethreaded_update, runnable); // Paper
-            if (priority <= 25) { // don't auto kick off unless priority
-                // Paper end
-                this.b();
-            }
+            this.queue.add(ChunkCoordIntPair.pair(i, j), priority, lightenginethreaded_update, runnable);
+            // Paper end
 
         }, ChunkCoordIntPair.pair(i, j), intsupplier));
     }
@@ -226,13 +237,23 @@ public class LightEngineThreaded extends LightEngine implements AutoCloseable {
     public CompletableFuture<IChunkAccess> a(IChunkAccess ichunkaccess, boolean flag) {
         ChunkCoordIntPair chunkcoordintpair = ichunkaccess.getPos();
 
-        ichunkaccess.b(false);
         // Paper start
+        //ichunkaccess.b(false); // Don't need to disable this
         long pair = chunkcoordintpair.pair();
         CompletableFuture<IChunkAccess> future = new CompletableFuture<>();
-        IntSupplier prioritySupplier = d.getPrioritySupplier(pair);
+        IntSupplier prioritySupplier = playerChunkMap.getPrioritySupplier(pair);
         this.e.a(ChunkTaskQueueSorter.a(() -> {
+            // Chunk's no longer needed
+            if (!isChunkLightStatus(pair)) {
+                System.out.println("drop chunk 1 " + ichunkaccess.getPos() + ichunkaccess.getChunkStatus());
+                future.complete(ichunkaccess);
+                return;
+            }
             this.queue.add(pair, prioritySupplier.getAsInt(), LightEngineThreaded.Update.PRE_UPDATE, SystemUtils.a(() -> {
+                if (!isChunkLightStatus(pair)) {
+                    System.out.println("drop chunk 2 " + ichunkaccess.getPos() + ichunkaccess.getChunkStatus());
+                    return;
+                }
                 // Paper end
             ChunkSection[] achunksection = ichunkaccess.getSections();
 
@@ -258,7 +279,11 @@ public class LightEngineThreaded extends LightEngine implements AutoCloseable {
         }));
 
         this.queue.add(pair, prioritySupplier.getAsInt(), LightEngineThreaded.Update.POST_UPDATE, () -> {
-            ichunkaccess.b(true);
+            // Paper start - only mark as lit if still at lit status
+            if (flag || isChunkLightStatus(pair)) {
+                ichunkaccess.b(true);
+            }
+            // Paper end
             super.b(chunkcoordintpair, false);
             // Paper start
             future.complete(ichunkaccess);