PlayerInventory.cs

using UnityEngine;

public class PlayerInventory : MonoBehaviour
{
    public static PlayerInventory Instance;
    
    public int inventorySize;
    public int selectedSlot;
    public ItemSO currentHeldItem;

    [SerializeField] private Transform handTransform;
    [SerializeField] private ItemSO[] playerInventory;

    private GameObject _displayedItem;

    private void Awake()
    {
        if (Instance == null)
            Instance = this;
        
        playerInventory = new ItemSO[inventorySize];
    }

    public bool TryAddItem(ItemSO item)
    {
        int emptySlot = FindEmptySlot();
        
        if (emptySlot == -1) return false;
        
        playerInventory[emptySlot] = item;
        UpdateHeldItem();
        return true;
    }
    
    public bool TryRemoveItem(ItemSO item)
    {
        if(playerInventory[selectedSlot] == null) return false;
        
        playerInventory[selectedSlot] = null;
        UpdateHeldItem();
        return true;
    }
    
    public void SelectSlot(int slotIndex)
    {
        if(slotIndex < 0 || slotIndex >= playerInventory.Length) return;
        
        selectedSlot = slotIndex;
        UpdateHeldItem();
    }

    private int FindEmptySlot()
    {
        for (int i = 0; i < playerInventory.Length; i++)
        {
            if (playerInventory[i] == null)
                return i;
        }
        return -1;
    }

    private void UpdateHeldItem()
    {
        if(_displayedItem != null) Destroy(_displayedItem);
        
        currentHeldItem = playerInventory[selectedSlot];

        if (currentHeldItem == null) return;
        
        _displayedItem = Instantiate(currentHeldItem.itemPrefab, handTransform);
    }
}