PaperMC/nms-patches/EntityEnderDragon.patch

--- a/net/minecraft/server/EntityEnderDragon.java
+++ b/net/minecraft/server/EntityEnderDragon.java
@@ -6,7 +6,13 @@
 import javax.annotation.Nullable;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+// CraftBukkit start
+import org.bukkit.craftbukkit.block.CraftBlock;
+import org.bukkit.event.entity.EntityExplodeEvent;
+import org.bukkit.event.entity.EntityRegainHealthEvent;
+// CraftBukkit end
 
+// PAIL: Fixme
 public class EntityEnderDragon extends EntityInsentient implements IMonster {
 
     private static final Logger LOGGER = LogManager.getLogger();
@@ -38,6 +44,7 @@
     private final PathPoint[] bJ = new PathPoint[24];
     private final int[] bK = new int[24];
     private final Path bL = new Path();
+    private Explosion explosionSource = new Explosion(null, this, null, null, Double.NaN, Double.NaN, Double.NaN, Float.NaN, true, Explosion.Effect.DESTROY); // CraftBukkit - reusable source for CraftTNTPrimed.getSource()
 
     public EntityEnderDragon(EntityTypes<? extends EntityEnderDragon> entitytypes, World world) {
         super(EntityTypes.ENDER_DRAGON, world);
@@ -175,7 +182,7 @@
 
                     Vec3D vec3d1 = idragoncontroller.g();
 
-                    if (vec3d1 != null) {
+                    if (vec3d1 != null && idragoncontroller.getControllerPhase() != DragonControllerPhase.HOVER) { // CraftBukkit - Don't move when hovering
                         d0 = vec3d1.x - this.locX();
                         d1 = vec3d1.y - this.locY();
                         d2 = vec3d1.z - this.locZ();
@@ -313,7 +320,14 @@
             if (this.currentEnderCrystal.dead) {
                 this.currentEnderCrystal = null;
             } else if (this.ticksLived % 10 == 0 && this.getHealth() < this.getMaxHealth()) {
-                this.setHealth(this.getHealth() + 1.0F);
+                // CraftBukkit start
+                EntityRegainHealthEvent event = new EntityRegainHealthEvent(this.getBukkitEntity(), 1.0F, EntityRegainHealthEvent.RegainReason.ENDER_CRYSTAL);
+                this.world.getServer().getPluginManager().callEvent(event);
+
+                if (!event.isCancelled()) {
+                    this.setHealth((float) (this.getHealth() + event.getAmount()));
+                }
+                // CraftBukkit end
             }
         }
 
@@ -388,6 +402,9 @@
         int j1 = MathHelper.floor(axisalignedbb.maxZ);
         boolean flag = false;
         boolean flag1 = false;
+        // CraftBukkit start - Create a list to hold all the destroyed blocks
+        List<org.bukkit.block.Block> destroyedBlocks = new java.util.ArrayList<org.bukkit.block.Block>();
+        // CraftBukkit end
 
         for (int k1 = i; k1 <= l; ++k1) {
             for (int l1 = j; l1 <= i1; ++l1) {
@@ -398,7 +415,11 @@
 
                     if (!iblockdata.isAir() && iblockdata.getMaterial() != Material.FIRE) {
                         if (this.world.getGameRules().getBoolean(GameRules.MOB_GRIEFING) && !TagsBlock.DRAGON_IMMUNE.isTagged(block)) {
-                            flag1 = this.world.a(blockposition, false) || flag1;
+                            // CraftBukkit start - Add blocks to list rather than destroying them
+                            // flag1 = this.world.a(blockposition, false) || flag1;
+                            flag1 = true;
+                            destroyedBlocks.add(CraftBlock.at(world, blockposition));
+                            // CraftBukkit end
                         } else {
                             flag = true;
                         }
@@ -407,6 +428,51 @@
             }
         }
 
+        // CraftBukkit start - Set off an EntityExplodeEvent for the dragon exploding all these blocks
+        // SPIGOT-4882: don't fire event if nothing hit
+        if (!flag1) {
+            return flag;
+        }
+
+        org.bukkit.entity.Entity bukkitEntity = this.getBukkitEntity();
+        EntityExplodeEvent event = new EntityExplodeEvent(bukkitEntity, bukkitEntity.getLocation(), destroyedBlocks, 0F);
+        bukkitEntity.getServer().getPluginManager().callEvent(event);
+        if (event.isCancelled()) {
+            // This flag literally means 'Dragon hit something hard' (Obsidian, White Stone or Bedrock) and will cause the dragon to slow down.
+            // We should consider adding an event extension for it, or perhaps returning true if the event is cancelled.
+            return flag;
+        } else if (event.getYield() == 0F) {
+            // Yield zero ==> no drops
+            for (org.bukkit.block.Block block : event.blockList()) {
+                this.world.a(new BlockPosition(block.getX(), block.getY(), block.getZ()), false);
+            }
+        } else {
+            for (org.bukkit.block.Block block : event.blockList()) {
+                org.bukkit.Material blockId = block.getType();
+                if (blockId.isAir()) {
+                    continue;
+                }
+
+                CraftBlock craftBlock = ((CraftBlock) block);
+                BlockPosition blockposition = craftBlock.getPosition();
+
+                Block nmsBlock = craftBlock.getNMS().getBlock();
+                if (nmsBlock.a(explosionSource)) {
+                    TileEntity tileentity = nmsBlock.isTileEntity() ? this.world.getTileEntity(blockposition) : null;
+                    LootTableInfo.Builder loottableinfo_builder = (new LootTableInfo.Builder((WorldServer) this.world)).a(this.world.random).set(LootContextParameters.ORIGIN, Vec3D.a(blockposition)).set(LootContextParameters.TOOL, ItemStack.b).set(LootContextParameters.EXPLOSION_RADIUS, 1.0F / event.getYield()).setOptional(LootContextParameters.BLOCK_ENTITY, tileentity);
+
+                    craftBlock.getNMS().a(loottableinfo_builder).forEach((itemstack) -> {
+                        Block.a(world, blockposition, itemstack);
+                    });
+                    craftBlock.getNMS().dropNaturally((WorldServer) world, blockposition, ItemStack.b);
+                }
+                nmsBlock.wasExploded(world, blockposition, explosionSource);
+
+                this.world.a(blockposition, false);
+            }
+        }
+        // CraftBukkit end
+
         if (flag1) {
             BlockPosition blockposition1 = new BlockPosition(i + this.random.nextInt(l - i + 1), j + this.random.nextInt(i1 - j + 1), k + this.random.nextInt(j1 - k + 1));