Add inventory system

scripts/Systems/ItemSystem.gd

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+class_name ItemSystem
+const Item = preload("res://scripts/Items/Item.gd");
+const ItemStack = preload("res://scripts/Items/ItemStack.gd");
+
+enum ItemSortType {
+	NAME,
+	TYPE
+};
+
+class ItemStackNameComparator:
+	static func _sort(a, b):
+		return a.item.getName().to_lower() < b.item.getName().to_lower()
+
+class ItemStackTypeComparator:
+	static func _sort(a, b):
+		return a.item.getCategory() < b.item.getCategory()
+
+# Constants
+const ITEM_STACK_SIZE_MAX = 99;
+var ITEM_POTION = preload("res://scripts/Items/Potion.gd").new()
+var inventory:Array[ItemStack] = [];
+
+# Methods
+func addItem(item: Item, quantity: int = 1) -> void:
+	print("Adding ", quantity, "x ", item.getName());
+	if !item.isStackable():
+		# Item cannot be stacked, add each item to inv
+		for i in range(quantity):
+			inventory.append(ItemStack.new(item, 1))
+		return
+		
+	# Check for existing stacks
+	for stack in inventory:
+		if stack.item != item or stack.quantity >= ITEM_STACK_SIZE_MAX:
+			continue
+			
+		var spaceAvailable = ITEM_STACK_SIZE_MAX - stack.quantity
+		
+		if quantity <= spaceAvailable:
+			stack.quantity += quantity;
+			return
+			
+		stack.quantity = ITEM_STACK_SIZE_MAX;
+		quantity -= spaceAvailable;
+	
+	# Add any remaining inventory as new stack.
+	while quantity > 0:
+		var newStackQuantity = min(quantity, ITEM_STACK_SIZE_MAX);
+		inventory.append(ItemStack.new(item, newStackQuantity));
+		quantity -= newStackQuantity;
+
+func removeItem(item: Item, quantity: int) -> void:
+	var totalQuantity = 0
+	
+	# Calculate total quantity of the item in the inventory
+	for stack in inventory:
+		if stack.item != item:
+			continue
+		totalQuantity += stack.quantity
+	
+	if totalQuantity < quantity:
+		push_error("Not enough quantity to remove");
+		return
+	
+	# Remove the quantity from the stacks
+	for stack in inventory:
+		if stack.item != item:
+			continue
+
+		if stack.quantity < quantity:
+			quantity -= stack.quantity
+			inventory.erase(stack)
+
+		stack.quantity -= quantity
+		if stack.quantity == 0:
+			inventory.erase(stack)
+
+		if quantity == 0:
+			return
+
+func sortBy(by:ItemSortType) -> void:
+	match by:
+		ItemSortType.NAME:
+			inventory.sort_custom(ItemStackNameComparator._sort)
+		ItemSortType.TYPE:
+			inventory.sort_custom(ItemStackTypeComparator._sort)

scripts/Systems/Systems.gd

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+class_name Systems extends Node
+
+var ITEM = preload("res://scripts/Systems/ItemSystem.gd").new()