User-friendly update scheduling

src/main/java/net/minestom/server/instance/Instance.java

@@ -16,6 +16,7 @@ import net.minestom.server.network.packet.server.play.ChunkDataPacket;
 import net.minestom.server.utils.BlockPosition;
 import net.minestom.server.utils.ChunkUtils;
 import net.minestom.server.utils.Position;
+import net.minestom.server.utils.time.TimeUnit;
 import net.minestom.server.world.Dimension;
 
 import java.io.File;
@@ -353,4 +354,14 @@ public abstract class Instance implements BlockModifier, DataContainer {
         return entities != null ? entities : new CopyOnWriteArraySet<>();
     }
 
+    /**
+     * Schedule a block update at a given position.
+     * Does nothing if no custom block is present at 'position'.
+     * Cancelled if the block changes between this call and the actual update
+     * @param time in how long this update must be performed?
+     * @param unit in what unit is the time expressed
+     * @param position the location of the block to update
+     */
+    public abstract void scheduleUpdate(int time, TimeUnit unit, BlockPosition position);
+
 }

src/main/java/net/minestom/server/instance/InstanceContainer.java

@@ -1,6 +1,7 @@
 package net.minestom.server.instance;
 
 import io.netty.buffer.ByteBuf;
+import net.minestom.server.MinecraftServer;
 import net.minestom.server.data.Data;
 import net.minestom.server.entity.Player;
 import net.minestom.server.event.PlayerBlockBreakEvent;
@@ -14,10 +15,13 @@ import net.minestom.server.network.packet.server.play.ParticlePacket;
 import net.minestom.server.network.packet.server.play.UnloadChunkPacket;
 import net.minestom.server.particle.Particle;
 import net.minestom.server.particle.ParticleCreator;
+import net.minestom.server.timer.TaskRunnable;
 import net.minestom.server.utils.BlockPosition;
 import net.minestom.server.utils.ChunkUtils;
 import net.minestom.server.utils.Position;
 import net.minestom.server.utils.SerializerUtils;
+import net.minestom.server.utils.time.TimeUnit;
+import net.minestom.server.utils.time.UpdateOption;
 import net.minestom.server.world.Dimension;
 
 import java.io.File;
@@ -376,4 +380,24 @@ public class InstanceContainer extends Instance {
         chunk.sendPacketToViewers(blockChangePacket);
     }
 
+    @Override
+    public void scheduleUpdate(int time, TimeUnit unit, BlockPosition position) {
+        Instance instance = this;
+        CustomBlock toUpdate = getCustomBlock(position);
+        if(toUpdate == null) {
+            return;
+        }
+        MinecraftServer.getSchedulerManager().addDelayedTask(new TaskRunnable() {
+            @Override
+            public void run() {
+                CustomBlock currentBlock = instance.getCustomBlock(position);
+                if(currentBlock == null)
+                    return;
+                if(currentBlock.getCustomBlockId() != toUpdate.getCustomBlockId()) { // block changed
+                    return;
+                }
+                currentBlock.update(instance, position, getBlockData(position));
+            }
+        }, new UpdateOption(time, unit));
+    }
 }

src/main/java/net/minestom/server/instance/SharedInstance.java

@@ -6,6 +6,7 @@ import net.minestom.server.instance.batch.BlockBatch;
 import net.minestom.server.instance.batch.ChunkBatch;
 import net.minestom.server.utils.BlockPosition;
 import net.minestom.server.utils.Position;
+import net.minestom.server.utils.time.TimeUnit;
 
 import java.io.File;
 import java.util.Collection;
@@ -154,6 +155,11 @@ public class SharedInstance extends Instance {
         instanceContainer.setSeparateBlocks(x, y, z, blockId, customBlockId, data);
     }
 
+    @Override
+    public void scheduleUpdate(int time, TimeUnit unit, BlockPosition position) {
+        instanceContainer.scheduleUpdate(time, unit, position);
+    }
+
     public InstanceContainer getInstanceContainer() {
         return instanceContainer;
     }