Only recalculate and sync net items when a player has the terminal open

src/main/kotlin/net/shadowfacts/phycon/network/block/terminal/TerminalBlockEntity.kt

@@ -27,9 +27,10 @@ import net.shadowfacts.phycon.util.toTag
 class TerminalBlockEntity: DeviceBlockEntity(PhyBlockEntities.TERMINAL), InventoryListener, BlockEntityClientSerializable {
 
 	private val inventoryCache = mutableMapOf<MACAddress, GroupedItemInv>()
-	val cachedNetItems = ItemStackCollections.intMap()
 	val internalBuffer = BasicInventory(18)
 
+	private var observers = 0
+	val cachedNetItems = ItemStackCollections.intMap()
 	var counter = 0
 
 	init {
@@ -61,15 +62,25 @@ class TerminalBlockEntity: DeviceBlockEntity(PhyBlockEntities.TERMINAL), Invento
 		}
 	}
 
+	fun addObserver() {
+		observers++
+	}
+
+	fun removeObserver() {
+		observers--
+	}
+
 	override fun tick() {
 		super.tick()
-		if (!world!!.isClient && (++counter % 20) == 0) {
+
+		if (observers > 0 && (++counter % 20) == 0) {
+			counter = 0
+			if (world!!.isClient) {
+				println(cachedNetItems)
+			} else {
 				updateNetItems()
 				sync()
 			}
-
-		if (world!!.isClient && (++counter % 20) == 0) {
-			println(cachedNetItems)
 		}
 	}
 
@@ -81,6 +92,7 @@ class TerminalBlockEntity: DeviceBlockEntity(PhyBlockEntities.TERMINAL), Invento
 				buf.writeBlockPos(pos)
 			}
 		}
+		addObserver()
 	}
 
 	override fun onInvChange(inv: Inventory) {

src/main/kotlin/net/shadowfacts/phycon/network/block/terminal/TerminalContainer.kt

@@ -39,4 +39,10 @@ class TerminalContainer(syncId: Int, playerInv: PlayerInventory, val terminal: T
 	override fun canUse(player: PlayerEntity): Boolean {
 		return true
 	}
+
+	override fun close(player: PlayerEntity) {
+		super.close(player)
+
+		terminal.removeObserver()
+	}
 }