OldBlueWater/BlueWater/Assets/02.Scripts/PlayerInventory.cs

using System;
using System.Collections.Generic;
using UnityEngine;

// ReSharper disable once CheckNamespace
namespace BlueWaterProject
{
    [Serializable]
    public class PlayerInventory
    {
        [SerializeField] private List<Item> items = new();
        
        public void AddItem(IItem item)
        {
            var existingItem = items.Find(i => i.ItemName == item.ItemName);
            
            if (existingItem != null)
            {
                existingItem.ItemCount += item.ItemCount;
            }
            else
            {
                items.Add(new Item(item.ItemName, item.ItemCount));
            }
        }
    }
}