Custom tick subscription documentation (#3851)

Author: jurrejelle

.gitignore

@@ -8,7 +8,6 @@ out/
 output/
 bin/
 libs/
-docs/site
 
 .classpath
 */.factorypath

docs/content/Modpacks/Other-Topics/Custom-Machine-Behavior.md

@@ -0,0 +1,71 @@
+---
+title: Custom Machine Behavior
+---
+
+!!! Warning
+    Custom Machine Behavior is currently only supported in Java.
+
+Sometimes, you want to do something in a machine that's not possible via Recipe Conditions or Recipe Modifiers. For this, Custom Machine Behavior might be the correct tool.
+
+It works by registering a custom TickableSubscription, which gets called every tick.
+Here, we want to make a greenhouse that, while running, also turns all the dirt above it into grass.
+```java
+
+public class Greenhouse extends WorkableElectricMultiblockMachine {
+
+    private TickableSubscription tickSubscription;
+
+    @Override
+    public void onStructureFormed() {
+        super.onStructureFormed();
+        if (!isRemote()) {
+            tickSubscription = this.subscribeServerTick(this::turnGreenery);
+        }
+    }
+
+    @Override
+    public void onStructureInvalid() {
+        super.onStructureInvalid();
+        if (!isRemote()) {
+            tickSubscription.unsubscribe();
+            tickSubscription = null;
+        }
+    }
+    
+    private void turnGreenery(){
+        if(!getRecipeLogic().isActive()) return;
+        BlockPos currentPosition = getRecipeLogic().getMachine().getHolder().getCurrentPos();
+        BlockPos abovePosition = currentPosition.above();
+        if(this.getLevel().getBlockState(abovePosition).equals(Blocks.DIRT.defaultBlockState())){
+            this.getLevel().setBlock(abovePosition, Blocks.GRASS.defaultBlockState(), 3);
+        }
+    }
+}
+```
+The `tickSubscription` field is a reference to the current subscription that should be called every tick. When this subscription is created, we tell the server to run `this.turnGreenery()` every tick.  
+
+In there, we simply check if the recipe logic is active, and if so, we turn the block above the machine into grass if it was already dirt.  
+
+To use it, you would do:
+```java
+    public static final MultiblockMachineDefinition GREENHOUSE = REGISTRATE
+        .multiblock("green_house", Greenhouse::new)
+        .rotationState(RotationState.ALL)
+        .recipeType(MyRecipeTypes.GREENHOUSE)
+        .recipeModifiers(OC_PERFECT_SUBTICK, BATCH_MODE)
+        .appearanceBlock(CASING_PTFE_INERT)
+        .pattern(definition -> {
+            var casing = blocks(CASING_PTFE_INERT.get()).setMinGlobalLimited(10);
+            var abilities = Predicates.autoAbilities(definition.getRecipeTypes())
+                    .or(Predicates.autoAbilities(true, false, false));
+            return FactoryBlockPattern.start()
+                    .aisle("XSX", "XXX", "XXX")
+                    .aisle("XXX", "XXX", "XXX")
+                    .where('S', Predicates.controller(blocks(definition.getBlock())))
+                    .where('X', casing.or(abilities))
+                    .build();
+        })
+        .workableCasingModel(GTCEu.id("block/casings/solid/machine_casing_inert_ptfe"),
+                GTCEu.id("block/multiblock/large_chemical_reactor"))
+        .register();
+```