2 files changed, 130 insertions, 0 deletions
diff --git a/source/game/components/items/Inventory.cs b/source/game/components/items/Inventory.cs
new file mode 100644
index 0000000..4309f5d
--- /dev/null
+++ b/source/game/components/items/Inventory.cs
@@ -0,0 +1,96 @@
+using System;
+using Celesteia.Resources;
+
+namespace Celesteia.Game.Components.Items {
+    public class Inventory {
+        private ItemStack[] items;
+        public readonly int Capacity;
+
+        public Inventory(int slots = 27, params ItemStack[] startingItems) {
+            Capacity = slots;
+            items = new ItemStack[slots];
+            
+            for (int i = 0; i < startingItems.Length; i++ ) items[i] = startingItems[i];
+        }
+
+        // Try adding an item to the inventory, return false if the inventory has no capacity for this action.
+        public bool AddItem(ItemStack stack) {
+            ItemStack existingStack = GetLastItemStack(stack.Key);
+
+            // If an item stack with this ID already exists, add the amount to that stack.
+            if (existingStack != null) {
+                existingStack.Amount += stack.Amount;
+
+                // If the max stack size was exceeded and a new stack has to be created, create it.
+                ItemStack newStack = existingStack.NewStack();
+                if (newStack != null) {
+                    if (!HasCapacity()) return false;
+                    existingStack.Amount = existingStack.Type.MaxStackSize;
+                    AddItemStack(newStack);
+                }
+            } else AddItemStack(stack);
+
+            return true;
+        }
+
+        public ItemStack GetItemStackWithID(byte id) {
+            return Array.FindLast(items, x => x != null && x.ID == id && x.Amount < x.Type.MaxStackSize);
+        }
+
+        public ItemStack GetLastItemStack(NamespacedKey key) {
+            return Array.FindLast(items, x => x != null && x.Key.Equals(key) && x.Amount < x.Type.MaxStackSize);
+        }
+
+        public ItemStack GetSlot(int slot) {
+            if (slot < 0 || slot > Capacity - 1) throw new ArgumentException($"Slot {slot} falls outside of the inventory's capacity.");
+            return items[slot];
+        }
+
+        public void SetSlot(int slot, ItemStack stack) {
+            if (slot < 0 || slot > Capacity - 1) throw new ArgumentException($"Slot {slot} falls outside of the inventory's capacity.");
+            items[slot] = stack;
+        }
+
+        public bool ContainsAmount(NamespacedKey key, int amount) {
+            return GetAmount(key) >= amount;
+        }
+
+        public int GetAmount(NamespacedKey key) {
+            int amount = 0;
+
+            ItemStack[] stacksOfItem = Array.FindAll(items, x => x != null && x.Key.Equals(key));
+            foreach (ItemStack stackOfItem in stacksOfItem) amount += stackOfItem.Amount;
+            
+            return amount;
+        }
+
+        public void RemoveAmount(NamespacedKey key, int amount) {
+            int amountToGo = amount;
+            
+            ItemStack lastStack;
+            while (amountToGo > 0) {
+                lastStack = Array.FindLast(items, x => x != null && x.Key.Equals(key));
+                int toRemove = Math.Min(lastStack.Amount, amountToGo);
+
+                lastStack.Amount -= toRemove;
+                amountToGo -= toRemove;
+                
+                AssertAmounts();
+            }
+        }
+
+        private void AddItemStack(ItemStack newStack) {
+            if (!HasCapacity()) return;
+            int i = Array.FindIndex(items, x => x == null);
+            items[i] = newStack;
+        }
+
+        private bool HasCapacity() {
+            return Array.Exists(items, x => x == null);
+        }
+
+        public void AssertAmounts() {
+            for (int i = 0; i < items.Length; i++) if (items[i] != null && items[i].Amount <= 0) items[i] = null;
+        }
+    }
+}
+\ No newline at end of file
diff --git a/source/game/components/items/ItemStack.cs b/source/game/components/items/ItemStack.cs
new file mode 100644
index 0000000..360904b
--- /dev/null
+++ b/source/game/components/items/ItemStack.cs
@@ -0,0 +1,34 @@
+using Celesteia.Resources;
+using Celesteia.Resources.Types;
+
+namespace Celesteia.Game.Components.Items {
+    public class ItemStack {
+        public byte ID;
+        public NamespacedKey Key;
+        public int Amount;
+        public readonly ItemType Type;
+
+        public ItemStack(NamespacedKey key, int amount) {
+            Key = key;
+            Amount = amount;
+
+            Type = ResourceManager.Items.GetResource(key) as ItemType;
+        }
+
+        public ItemStack NewStack() {
+            ItemStack stack = null;
+            if (Amount > Type.MaxStackSize) stack = new ItemStack(Key, Amount - Type.MaxStackSize);
+
+            return stack;
+        }
+
+        public ItemStack Clone() {
+            return new ItemStack(Key, Amount);
+        }
+
+        public override string ToString()
+        {
+            return $"{Amount}x {Type.Name}";
+        }
+    }
+}
+\ No newline at end of file