More work on this, added a new event and deprecated the old ones.

src/main/java/io/github/thebusybiscuit/slimefun4/api/events/AsyncGeneratorProcessCompleteEvent.java

@@ -16,7 +16,10 @@ import me.mrCookieSlime.Slimefun.Objects.SlimefunItem.SlimefunItem;
  *
  * @author poma123
  *
+ * @deprecated This event is no longer fired. Use the {@link AsyncMachineOperationFinishEvent} instead.
+ *
  */
+@Deprecated
 public class AsyncGeneratorProcessCompleteEvent extends AsyncMachineProcessCompleteEvent {
 
     private static final HandlerList handlers = new HandlerList();

src/main/java/io/github/thebusybiscuit/slimefun4/api/events/AsyncMachineOperationFinishEvent.java

@@ -0,0 +1,77 @@
+package io.github.thebusybiscuit.slimefun4.api.events;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+import org.bukkit.Bukkit;
+import org.bukkit.Location;
+import org.bukkit.event.Event;
+import org.bukkit.event.HandlerList;
+
+import io.github.thebusybiscuit.slimefun4.core.machines.MachineOperation;
+import io.github.thebusybiscuit.slimefun4.core.machines.MachineProcessor;
+
+/**
+ * This {@link Event} is fired whenever an {@link MachineProcessor} has completed a {@link MachineOperation}.
+ *
+ * @author poma123
+ * @author TheBusyBiscuit
+ *
+ */
+public class AsyncMachineOperationFinishEvent extends Event {
+
+    private static final HandlerList handlers = new HandlerList();
+
+    private final Location location;
+    private final MachineProcessor<?> machineProcessor;
+    private final MachineOperation machineOperation;
+
+    public <T extends MachineOperation> AsyncMachineOperationFinishEvent(Location l, MachineProcessor<T> processor, T operation) {
+        super(!Bukkit.isPrimaryThread());
+
+        this.location = l;
+        this.machineProcessor = processor;
+        this.machineOperation = operation;
+    }
+
+    /**
+     * This returns the {@link Location} of the machine.
+     *
+     * @return The {@link Location} of the machine
+     */
+    @Nonnull
+    public Location getLocation() {
+        return location;
+    }
+
+    /**
+     * The {@link MachineProcessor} instance of the machine.
+     *
+     * @return The {@link MachineProcessor} instance of the machine
+     */
+    @Nullable
+    public MachineProcessor<?> getProcessor() {
+        return machineProcessor;
+    }
+
+    /**
+     * This returns the used {@link MachineOperation} in the process.
+     *
+     * @return The {@link MachineOperation} of the process
+     */
+    @Nullable
+    public MachineOperation getOperation() {
+        return machineOperation;
+    }
+
+    @Nonnull
+    public static HandlerList getHandlerList() {
+        return handlers;
+    }
+
+    @Nonnull
+    @Override
+    public HandlerList getHandlers() {
+        return getHandlerList();
+    }
+}

src/main/java/io/github/thebusybiscuit/slimefun4/api/events/AsyncMachineProcessCompleteEvent.java

@@ -17,7 +17,10 @@ import me.mrCookieSlime.Slimefun.Objects.SlimefunItem.SlimefunItem;
  *
  * @author poma123
  *
+ * @deprecated This event is no longer fired. Use the {@link AsyncMachineOperationFinishEvent} instead.
+ *
  */
+@Deprecated
 public class AsyncMachineProcessCompleteEvent extends Event {
 
     private static final HandlerList handlers = new HandlerList();

src/main/java/io/github/thebusybiscuit/slimefun4/api/events/AsyncReactorProcessCompleteEvent.java

@@ -15,8 +15,11 @@ import me.mrCookieSlime.Slimefun.Objects.SlimefunItem.SlimefunItem;
  * This {@link Event} is fired whenever a {@link Reactor} has completed its process.
  *
  * @author poma123
+ * 
+ * @deprecated This event is no longer fired. Use the {@link AsyncMachineOperationFinishEvent} instead.
  *
  */
+@Deprecated
 public class AsyncReactorProcessCompleteEvent extends AsyncMachineProcessCompleteEvent {
 
     private static final HandlerList handlers = new HandlerList();

src/main/java/io/github/thebusybiscuit/slimefun4/core/machines/MachineProcessor.java

@@ -34,8 +34,31 @@ public class MachineProcessor<T extends MachineOperation> {
 
     private final ReadWriteLock lock = new ReentrantReadWriteLock();
     private final Map<BlockPosition, T> machines = new HashMap<>();
+    private final MachineProcessHolder<T> owner;
+
     private ItemStack progressBar;
 
+    /**
+     * This creates a new {@link MachineProcessor}.
+     * 
+     * @param owner
+     *            The owner of this {@link MachineProcessor}.
+     */
+    public MachineProcessor(@Nonnull MachineProcessHolder<T> owner) {
+        Validate.notNull(owner, "The MachineProcessHolder cannot be null.");
+        this.owner = owner;
+    }
+
+    /**
+     * This returns the owner of this {@link MachineProcessor}.
+     * 
+     * @return The owner / holder
+     */
+    @Nonnull
+    public MachineProcessHolder<T> getOwner() {
+        return owner;
+    }
+
     /**
      * This returns the progress bar icon for this {@link MachineProcessor}
      * or null if no progress bar was set.

src/main/java/io/github/thebusybiscuit/slimefun4/implementation/items/electric/reactors/Reactor.java

@@ -75,7 +75,7 @@ public abstract class Reactor extends AbstractEnergyProvider implements Hologram
     private static final int[] border_4 = { 25, 34, 43 };
 
     private final Set<Location> explosionsQueue = new HashSet<>();
-    private final MachineProcessor<FuelOperation> processor = new MachineProcessor<>();
+    private final MachineProcessor<FuelOperation> processor = new MachineProcessor<>(this);
 
     @ParametersAreNonnullByDefault
     protected Reactor(Category category, SlimefunItemStack item, RecipeType recipeType, ItemStack[] recipe) {

src/main/java/io/github/thebusybiscuit/slimefun4/implementation/items/geo/GEOMiner.java

@@ -57,7 +57,7 @@ public class GEOMiner extends SlimefunItem implements RecipeDisplayItem, EnergyN
     private static final int PROCESSING_TIME = 14;
     private static final int ENERGY_CONSUMPTION = 24;
 
-    private final MachineProcessor<MiningOperation> processor = new MachineProcessor<>();
+    private final MachineProcessor<MiningOperation> processor = new MachineProcessor<>(this);
 
     @ParametersAreNonnullByDefault
     public GEOMiner(Category category, SlimefunItemStack item, RecipeType recipeType, ItemStack[] recipe) {

src/main/java/me/mrCookieSlime/Slimefun/Objects/SlimefunItem/abstractItems/AContainer.java

@@ -51,7 +51,7 @@ public abstract class AContainer extends SlimefunItem implements InventoryBlock,
     private static final int[] BORDER_OUT = { 14, 15, 16, 17, 23, 26, 32, 33, 34, 35 };
 
     protected final List<MachineRecipe> recipes = new ArrayList<>();
-    private final MachineProcessor<CraftingOperation> processor = new MachineProcessor<>();
+    private final MachineProcessor<CraftingOperation> processor = new MachineProcessor<>(this);
 
     private int energyConsumedPerTick = -1;
     private int energyCapacity = -1;

src/main/java/me/mrCookieSlime/Slimefun/Objects/SlimefunItem/abstractItems/AGenerator.java

@@ -47,7 +47,7 @@ public abstract class AGenerator extends AbstractEnergyProvider implements Machi
     private static final int[] border_in = { 9, 10, 11, 12, 18, 21, 27, 28, 29, 30 };
     private static final int[] border_out = { 14, 15, 16, 17, 23, 26, 32, 33, 34, 35 };
 
-    private final MachineProcessor<FuelOperation> processor = new MachineProcessor<>();
+    private final MachineProcessor<FuelOperation> processor = new MachineProcessor<>(this);
 
     private int energyProducedPerTick = -1;
     private int energyCapacity = -1;