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

public class Inventory
{
    public event EventHandler OnItemListChanged;

    private List<Item> itemList;
    private Item selectedItem;

    public Inventory()
    {
        itemList = new List<Item>();
        selectedItem = null;
    }

    public void AddItem(Item item)
    {
        bool itemAlreadyInInventory = false;

        foreach (Item itemSlot in itemList)
        {
            if (itemSlot.Prefab == item.Prefab)
            {
                itemSlot.Increase(item.Amount);
                itemAlreadyInInventory = true;
            }
        }

        if (!itemAlreadyInInventory) itemList.Add(item);
        if (selectedItem == null) selectedItem = item;

        OnItemListChanged?.Invoke(this, EventArgs.Empty);
    }

    public void RemoveItem(Item item)
    {
        Item itemInInventory = null;

        foreach (Item inventoryItem in itemList)
        {
            if (inventoryItem.Prefab == item.Prefab)
            {
                inventoryItem.Decrease(item.Amount);
                itemInInventory = inventoryItem;
            }
        }

        if (itemInInventory != null && itemInInventory.IsEmpty())
        {
            if (itemInInventory == selectedItem)
                selectedItem = ItemAfter(selectedItem) ?? ItemBefore(selectedItem);

            itemList.Remove(itemInInventory);
        }

        OnItemListChanged?.Invoke(this, EventArgs.Empty);
    }

    public List<Item> GetItemList()
    {
        return itemList;
    }

    public Item GetSelectedItem()
    {
        return selectedItem;
    }

    public Item ItemBefore(Item item)
    {
        int idx = itemList.IndexOf(item);

        if (idx == -1 || idx == 0) return null;
        return itemList[idx - 1];
    }

    public Item ItemAfter(Item item)
    {
        int idx = itemList.IndexOf(item);

        if (idx == -1 || idx == itemList.Count) return null;
        return itemList[idx + 1];
    }

    public void SelectPreviousItem()
    {
        Item newSelected = ItemBefore(selectedItem);
        if (newSelected == null) return;

        OnItemListChanged?.Invoke(this, EventArgs.Empty);
    }

    public void SelectNextItem()
    {
        Item newSelected = ItemAfter(selectedItem);
        if (newSelected == null) return;

        OnItemListChanged?.Invoke(this, EventArgs.Empty);
    }
}