Chest Minecart contraptions

src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/Contraption.java

@@ -828,4 +828,5 @@ public abstract class Contraption {
 		return seats;
 	}
 
+	public void addExtraInventories(Entity entity) {};
 }

src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/ContraptionEntity.java

@@ -77,6 +77,7 @@ public class ContraptionEntity extends Entity implements IEntityAdditionalSpawnD
 	protected boolean initialized;
 	final List<Entity> collidingEntities = new ArrayList<>();
 	private boolean isSerializingFurnaceCart;
+	private boolean attachedExtraInventories;
 
 	private static final Ingredient FUEL_ITEMS = Ingredient.fromItems(Items.COAL, Items.CHARCOAL);
 	private static final DataParameter<Boolean> STALLED =
@@ -104,6 +105,7 @@ public class ContraptionEntity extends Entity implements IEntityAdditionalSpawnD
 		motionBeforeStall = Vec3d.ZERO;
 		stationary = entityTypeIn == AllEntityTypes.STATIONARY_CONTRAPTION.get();
 		isSerializingFurnaceCart = false;
+		attachedExtraInventories = false;
 		forcedAngle = -1;
 	}
 
@@ -323,6 +325,10 @@ public class ContraptionEntity extends Entity implements IEntityAdditionalSpawnD
 		Entity riding = e;
 		while (riding.getRidingEntity() != null)
 			riding = riding.getRidingEntity();
+		if (!attachedExtraInventories) {
+			contraption.addExtraInventories(riding);
+			attachedExtraInventories = true;
+		}
 
 		boolean isOnCoupling = false;
 		if (contraption instanceof MountedContraption) {

src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/mounted/CartAssemblerBlock.java

@@ -25,6 +25,7 @@ import net.minecraft.block.BlockState;
 import net.minecraft.block.material.PushReaction;
 import net.minecraft.entity.Entity;
 import net.minecraft.entity.item.minecart.AbstractMinecartEntity;
+import net.minecraft.entity.item.minecart.ChestMinecartEntity;
 import net.minecraft.entity.item.minecart.FurnaceMinecartEntity;
 import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.item.Item;
@@ -166,7 +167,7 @@ public class CartAssemblerBlock extends AbstractRailBlock
 	}
 
 	public static boolean canAssembleTo(AbstractMinecartEntity cart) {
-		return cart.canBeRidden() || cart instanceof FurnaceMinecartEntity;
+		return cart.canBeRidden() || cart instanceof FurnaceMinecartEntity || cart instanceof ChestMinecartEntity;
 	}
 
 	@Override

src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/mounted/ItemHandlerModifiableFromIInventory.java

@@ -0,0 +1,140 @@
+package com.simibubi.create.content.contraptions.components.structureMovement.mounted;
+
+import mcp.MethodsReturnNonnullByDefault;
+import net.minecraft.inventory.IInventory;
+import net.minecraft.item.ItemStack;
+import net.minecraftforge.items.IItemHandlerModifiable;
+import net.minecraftforge.items.ItemHandlerHelper;
+
+import javax.annotation.Nonnull;
+import javax.annotation.ParametersAreNonnullByDefault;
+
+
+@MethodsReturnNonnullByDefault
+@ParametersAreNonnullByDefault
+public class ItemHandlerModifiableFromIInventory implements IItemHandlerModifiable {
+	private final IInventory inventory;
+
+	public ItemHandlerModifiableFromIInventory(IInventory inventory) {
+		this.inventory = inventory;
+	}
+
+	@Override
+	public void setStackInSlot(int slot, ItemStack stack) {
+		inventory.setInventorySlotContents(slot, stack);
+	}
+
+	@Override
+	public int getSlots() {
+		return inventory.getSizeInventory();
+	}
+
+	@Override
+	public ItemStack getStackInSlot(int slot) {
+		return inventory.getStackInSlot(slot);
+	}
+
+	@Override
+	@Nonnull
+	public ItemStack insertItem(int slot, @Nonnull ItemStack stack, boolean simulate)
+	{
+		if (stack.isEmpty())
+			return ItemStack.EMPTY;
+
+		if (!isItemValid(slot, stack))
+			return stack;
+
+		validateSlotIndex(slot);
+
+		ItemStack existing = getStackInSlot(slot);
+
+		int limit = getStackLimit(slot, stack);
+
+		if (!existing.isEmpty())
+		{
+			if (!ItemHandlerHelper.canItemStacksStack(stack, existing))
+				return stack;
+
+			limit -= existing.getCount();
+		}
+
+		if (limit <= 0)
+			return stack;
+
+		boolean reachedLimit = stack.getCount() > limit;
+
+		if (!simulate)
+		{
+			if (existing.isEmpty())
+			{
+				setStackInSlot(slot, reachedLimit ? ItemHandlerHelper.copyStackWithSize(stack, limit) : stack);
+			}
+			else
+			{
+				existing.grow(reachedLimit ? limit : stack.getCount());
+			}
+		}
+
+		return reachedLimit ? ItemHandlerHelper.copyStackWithSize(stack, stack.getCount()- limit) : ItemStack.EMPTY;
+	}
+
+	@Override
+	@Nonnull
+	public ItemStack extractItem(int slot, int amount, boolean simulate)
+	{
+		if (amount == 0)
+			return ItemStack.EMPTY;
+
+		validateSlotIndex(slot);
+
+		ItemStack existing = getStackInSlot(slot);
+
+		if (existing.isEmpty())
+			return ItemStack.EMPTY;
+
+		int toExtract = Math.min(amount, existing.getMaxStackSize());
+
+		if (existing.getCount() <= toExtract)
+		{
+			if (!simulate)
+			{
+				setStackInSlot(slot, ItemStack.EMPTY);
+				return existing;
+			}
+			else
+			{
+				return existing.copy();
+			}
+		}
+		else
+		{
+			if (!simulate)
+			{
+				setStackInSlot(slot, ItemHandlerHelper.copyStackWithSize(existing, existing.getCount() - toExtract));
+			}
+
+			return ItemHandlerHelper.copyStackWithSize(existing, toExtract);
+		}
+	}
+
+	@Override
+	public int getSlotLimit(int slot) {
+		return inventory.getInventoryStackLimit();
+	}
+
+	@Override
+	public boolean isItemValid(int slot, ItemStack stack) {
+		return inventory.isItemValidForSlot(slot, stack);
+	}
+
+	private void validateSlotIndex(int slot)
+	{
+		if (slot < 0 || slot >= getSlots())
+			throw new RuntimeException("Slot " + slot + " not in valid range - [0," + getSlots() + ")");
+	}
+
+	private int getStackLimit(int slot, ItemStack stack)
+	{
+		return Math.min(getSlotLimit(slot), stack.getMaxStackSize());
+	}
+}

src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/mounted/MountedContraption.java

@@ -27,6 +27,9 @@ import net.minecraft.util.math.BlockPos;
 import net.minecraft.world.IWorld;
 import net.minecraft.world.World;
 import net.minecraft.world.gen.feature.template.Template.BlockInfo;
+import net.minecraft.entity.Entity;
+import net.minecraft.inventory.IInventory;
+import net.minecraftforge.items.wrapper.CombinedInvWrapper;
 
 public class MountedContraption extends Contraption {
 
@@ -86,6 +89,7 @@ public class MountedContraption extends Contraption {
 							if (!CartAssemblerBlock.canAssembleTo(abstractMinecartEntity))
 								break;
 							connectedCart = abstractMinecartEntity;
+							addExtraInventories(abstractMinecartEntity);
 						}
 					}
 				}
@@ -126,4 +130,9 @@ public class MountedContraption extends Contraption {
 		return AllBlocks.MINECART_ANCHOR.has(state);
 	}
 
+	@Override
+	public void addExtraInventories(Entity cart) {
+		if (cart instanceof IInventory)
+			inventory = new CombinedInvWrapper(new ItemHandlerModifiableFromIInventory((IInventory) cart), inventory);
+	}
 }