Mob Spawner API Enhancements

== AT ==
public net.minecraft.world.level.BaseSpawner isNearPlayer(Lnet/minecraft/world/level/Level;Lnet/minecraft/core/BlockPos;)Z
public net.minecraft.world.level.BaseSpawner delay(Lnet/minecraft/world/level/Level;Lnet/minecraft/core/BlockPos;)V
public net.minecraft.world.level.BaseSpawner setNextSpawnData(Lnet/minecraft/world/level/Level;Lnet/minecraft/core/BlockPos;Lnet/minecraft/world/level/SpawnData;)V

paper-server/src/main/java/org/bukkit/craftbukkit/block/CraftCreatureSpawner.java

@@ -29,7 +29,7 @@ import org.bukkit.craftbukkit.entity.CraftEntityType;
 import org.bukkit.entity.EntitySnapshot;
 import org.bukkit.entity.EntityType;
 
-public class CraftCreatureSpawner extends CraftBlockEntityState<SpawnerBlockEntity> implements CreatureSpawner {
+public class CraftCreatureSpawner extends CraftBlockEntityState<SpawnerBlockEntity> implements CreatureSpawner, org.bukkit.craftbukkit.spawner.PaperSharedSpawnerLogic { // Paper - more spawner API
 
     public CraftCreatureSpawner(World world, SpawnerBlockEntity tileEntity) {
         super(world, tileEntity);
@@ -291,4 +291,38 @@ public class CraftCreatureSpawner extends CraftBlockEntityState<SpawnerBlockEnti
                 new HashMap<>(nms.slotDropChances().entrySet().stream().collect(Collectors.toMap((entry) -> CraftEquipmentSlot.getSlot(entry.getKey()), Map.Entry::getValue)))
         )).orElse(null);
     }
+
+    // Paper start - more spawner API
+    @Override
+    public boolean isActivated() {
+        requirePlaced();
+        return org.bukkit.craftbukkit.spawner.PaperSharedSpawnerLogic.super.isActivated();
+    }
+
+    @Override
+    public void resetTimer() {
+        requirePlaced();
+        org.bukkit.craftbukkit.spawner.PaperSharedSpawnerLogic.super.resetTimer();
+    }
+
+    @Override
+    public void setNextSpawnData(final SpawnData spawnData) {
+        this.getSpawner().setNextSpawnData(this.isPlaced() ? this.getInternalWorld() : null, this.getInternalPosition(), spawnData);
+    }
+
+    @Override
+    public BaseSpawner getSpawner() {
+        return this.getSnapshot().getSpawner();
+    }
+
+    @Override
+    public net.minecraft.core.BlockPos getInternalPosition() {
+        return this.getPosition();
+    }
+
+    @Override
+    public net.minecraft.world.level.Level getInternalWorld() {
+        return this.world.getHandle();
+    }
+    // Paper end - more spawner API
 }

paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftMinecartMobSpawner.java

@@ -16,7 +16,7 @@ import org.bukkit.entity.EntitySnapshot;
 import org.bukkit.entity.EntityType;
 import org.bukkit.entity.minecart.SpawnerMinecart;
 
-final class CraftMinecartMobSpawner extends CraftMinecart implements SpawnerMinecart {
+final class CraftMinecartMobSpawner extends CraftMinecart implements SpawnerMinecart, org.bukkit.craftbukkit.spawner.PaperSharedSpawnerLogic { // Paper - more spawner API
     CraftMinecartMobSpawner(CraftServer server, MinecartSpawner entity) {
         super(server, entity);
     }
@@ -171,4 +171,21 @@ final class CraftMinecartMobSpawner extends CraftMinecart implements SpawnerMine
     public String toString() {
         return "CraftMinecartMobSpawner";
     }
+
+    // Paper start - more spawner API
+    @Override
+    public net.minecraft.world.level.BaseSpawner getSpawner() {
+        return this.getHandle().getSpawner();
+    }
+
+    @Override
+    public net.minecraft.world.level.Level getInternalWorld() {
+        return this.getHandle().level();
+    }
+
+    @Override
+    public net.minecraft.core.BlockPos getInternalPosition() {
+        return this.getHandle().blockPosition();
+    }
+    // Paper end - more spawner API
 }

paper-server/src/main/java/org/bukkit/craftbukkit/spawner/PaperSharedSpawnerLogic.java

@@ -0,0 +1,56 @@
+package org.bukkit.craftbukkit.spawner;
+
+import com.google.common.base.Preconditions;
+import java.util.Optional;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.entity.EntityType;
+import net.minecraft.world.level.BaseSpawner;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.SpawnData;
+import org.bukkit.craftbukkit.inventory.CraftItemStack;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.spawner.Spawner;
+
+/**
+ * A common parent interface for both the {@link org.bukkit.craftbukkit.block.CraftCreatureSpawner} and minecart mob spawner.
+ */
+public interface PaperSharedSpawnerLogic extends Spawner {
+
+    BaseSpawner getSpawner();
+
+    Level getInternalWorld();
+
+    BlockPos getInternalPosition();
+
+    default boolean isActivated() {
+        return this.getSpawner().isNearPlayer(this.getInternalWorld(), this.getInternalPosition());
+    }
+
+    default void resetTimer() {
+        this.getSpawner().delay(this.getInternalWorld(), this.getInternalPosition());
+    }
+
+    default void setNextSpawnData(SpawnData spawnData) {
+        this.getSpawner().setNextSpawnData(this.getInternalWorld(), this.getInternalPosition(), spawnData);
+    }
+
+    default void setSpawnedItem(final ItemStack itemStack) {
+        Preconditions.checkArgument(itemStack != null && !itemStack.getType().isAir(), "spawners cannot spawn air");
+
+        final net.minecraft.world.item.ItemStack item = CraftItemStack.asNMSCopy(itemStack);
+        final CompoundTag entity = new CompoundTag();
+        entity.putString(Entity.ID_TAG, BuiltInRegistries.ENTITY_TYPE.getKey(EntityType.ITEM).toString());
+        entity.put("Item", item.save(this.getInternalWorld().registryAccess()));
+
+        this.setNextSpawnData(
+            new net.minecraft.world.level.SpawnData(
+                entity,
+                java.util.Optional.empty(),
+                Optional.ofNullable(this.getSpawner().nextSpawnData).flatMap(SpawnData::equipment)
+            )
+        );
+    }
+}