Fix #10323: Inefficient Ender Dragon respawn sequence

This issue likely arose from the method findExitPortal(),
which has been optimized. This optimization will ensure
better server performance during the respawn sequence
and smoother gameplay.

Signed-off-by: Afonso Jacinto
<[email protected]>

Author: AfonsoMendoncaJacinto

paper-server/patches/sources/net/minecraft/world/level/dimension/end/EndDragonFight.java.patch

@@ -1,5 +1,13 @@
 --- a/net/minecraft/world/level/dimension/end/EndDragonFight.java
 +++ b/net/minecraft/world/level/dimension/end/EndDragonFight.java
+@@ -48,6 +_,7 @@
+ import net.minecraft.world.level.block.state.pattern.BlockPattern;
+ import net.minecraft.world.level.block.state.pattern.BlockPatternBuilder;
+ import net.minecraft.world.level.block.state.predicate.BlockPredicate;
++import net.minecraft.world.level.block.state.BlockState;
+ import net.minecraft.world.level.chunk.ChunkAccess;
+ import net.minecraft.world.level.chunk.LevelChunk;
+ import net.minecraft.world.level.chunk.status.ChunkStatus;
 @@ -69,8 +_,9 @@
      private static final int GATEWAY_DISTANCE = 96;
      public static final int DRAGON_SPAWN_Y = 128;
@@ -37,6 +45,81 @@
                  this.dragonUUID = null;
              }
          }
+@@ -267,21 +_,45 @@
+         return false;
+     }
+ 
++    // Paper start - Fix inefficient Ender Dragon respawn sequence
+     @Nullable
+     public BlockPattern.BlockPatternMatch findExitPortal() {
++
++        BlockPos location = EndPodiumFeature.getLocation(this.origin);
++        int i1 = this.level.getHeightmapPos(Heightmap.Types.MOTION_BLOCKING, location).getY();
++        BlockPos current_position;
++        BlockState state;
++    
++        for (int i2 = i1; i2 >= this.level.getMinY(); i2--) {
++
++            current_position = new BlockPos(location.getX(), i2, location.getZ());
++            state = level.getBlockState(current_position);
++
++            if (state.getBlock() == Blocks.BEDROCK) {
++                BlockPattern.BlockPatternMatch blockPatternMatch1 = this.exitPortalPattern.find(this.level, current_position);
++                if (blockPatternMatch1 != null) {
++                    if (this.portalLocation == null) {
++                        this.portalLocation = blockPatternMatch1.getBlock(3, 3, 3).getPos();
++                    }
++
++                    return blockPatternMatch1;
++                }
++            }
++        }
++
+         ChunkPos chunkPos = new ChunkPos(this.origin);
+ 
+         for (int i = -8 + chunkPos.x; i <= 8 + chunkPos.x; i++) {
+-            for (int i1 = -8 + chunkPos.z; i1 <= 8 + chunkPos.z; i1++) {
++            for (i1 = -8 + chunkPos.z; i1 <= 8 + chunkPos.z; i1++) {
+                 LevelChunk chunk = this.level.getChunk(i, i1);
+ 
+                 for (BlockEntity blockEntity : chunk.getBlockEntities().values()) {
+                     if (blockEntity instanceof TheEndPortalBlockEntity) {
+                         BlockPattern.BlockPatternMatch blockPatternMatch = this.exitPortalPattern.find(this.level, blockEntity.getBlockPos());
+                         if (blockPatternMatch != null) {
+-                            BlockPos pos = blockPatternMatch.getBlock(3, 3, 3).getPos();
++
+                             if (this.portalLocation == null) {
+-                                this.portalLocation = pos;
++                                this.portalLocation = blockPatternMatch.getBlock(3, 3, 3).getPos();
+                             }
+ 
+                             return blockPatternMatch;
+@@ -290,23 +_,10 @@
+                 }
+             }
+         }
+-
+-        BlockPos location = EndPodiumFeature.getLocation(this.origin);
+-        int i1 = this.level.getHeightmapPos(Heightmap.Types.MOTION_BLOCKING, location).getY();
+-
+-        for (int i2 = i1; i2 >= this.level.getMinY(); i2--) {
+-            BlockPattern.BlockPatternMatch blockPatternMatch1 = this.exitPortalPattern.find(this.level, new BlockPos(location.getX(), i2, location.getZ()));
+-            if (blockPatternMatch1 != null) {
+-                if (this.portalLocation == null) {
+-                    this.portalLocation = blockPatternMatch1.getBlock(3, 3, 3).getPos();
+-                }
+-
+-                return blockPatternMatch1;
+-            }
+-        }
+-
++    
+         return null;
+     }
++    // Paper end - Fix inefficient Ender Dragon respawn sequence
+ 
+     private boolean isArenaLoaded() {
+         if (this.skipArenaLoadedCheck) {
 @@ -365,12 +_,22 @@
              this.dragonEvent.setVisible(false);
              this.spawnExitPortal(true);