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

public class Inventory : MonoBehaviour
{
    public static Inventory Instance { get; private set; }
    public List<InventorySlot> items = new List<InventorySlot>();
    public int maxInventorySize = 20;

    private void Awake()
    {
        if (Instance == null)
        {
            Instance = this;
        }
        else
        {
            Destroy(gameObject);
        }
        if (SaveSystem.isGameLoaded)
        {
            LoadInventory();
        }
    }

    private void LoadInventory()
    {
        SaveDataPlayer save = SaveSystem.LoadPlayer();
        if (save != null)
        {
            foreach (SaveDataInventorySlot item in save.inventoryItems)
            {
                Item loadedItem = ItemDatabase.Instance.GetItem(item.itemId);
                if (loadedItem != null)
                {
                    items.Add(new InventorySlot(loadedItem, item.quantity));
                }
                else
                {
                    Debug.LogError($"Failed to load item with ID: {item.itemId}");
                }
            }
        }
    }

    public bool AddItem(Item item, int quantity = 1)
    {
        if (items.Count >= maxInventorySize && !item.isStackable)
        {
            //TODO: Show inventory full message
            Debug.Log("Inventory is full");
            return false;
        }

        InventorySlot existingSlot = items.Find(slot => slot.item.itemName == item.itemName);
        if (existingSlot != null && item.isStackable)
        {
            //Add to existing stack
            if (existingSlot.quantity + quantity <= item.maxStackSize)
            {
                existingSlot.quantity += quantity;
            }
            else
            {
                int remainingQuantity = item.maxStackSize - existingSlot.quantity;
                existingSlot.quantity = item.maxStackSize;
                //TODO: Show inventory overflow message
                Debug.Log("Inventory overflow");
                existingSlot.quantity += remainingQuantity;
            }

        }
        else
        {
            //Add new item to inventory
            items.Add(new InventorySlot(item, quantity));
        }
        GameStateEvents.inventoryChanged?.Invoke();
        return true;
    }

    public void RemoveItem(Item item, int quantity = 1)
    {
        InventorySlot existingSlot = items.Find(slot => slot.item.itemName == item.itemName);

        if (existingSlot != null)
        {
            if (existingSlot.quantity > quantity)
            {
                existingSlot.quantity -= quantity;
            }
            else
            {
                items.Remove(existingSlot);
            }
        }
        GameStateEvents.inventoryChanged?.Invoke();
    }
}

[System.Serializable]
public class InventorySlot
{
    public Item item;
    public int quantity;

    public InventorySlot(Item item, int quantity)
    {
        this.item = item;
        this.quantity = quantity;
    }
}