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

public class Inventory : MonoBehaviour
{
    public static Inventory Instance { get; private set; }

    [Serializable]
    public class InventorySlot
    {
        public ItemData item;
        public int amount;
    }

    [SerializeField] private List<InventorySlot> slots = new List<InventorySlot>();

    public IReadOnlyList<InventorySlot> Slots => slots;
    public event Action OnInventoryChanged;

    private void Awake()
    {
        if (Instance != null && Instance != this)
        {
            Destroy(gameObject);
            return;
        }

        Instance = this;
    }

    public void AddItem(ItemData item, int amount)
    {
        AddItem(item, amount, true);
    }

    public void AddItem(ItemData item, int amount, bool notifyQuestManager)
    {
        if (item == null || amount <= 0)
        {
            return;
        }

        InventorySlot slot = slots.Find(candidate => candidate.item == item);
        if (slot == null)
        {
            slot = new InventorySlot { item = item, amount = 0 };
            slots.Add(slot);
        }

        slot.amount += amount;
        OnInventoryChanged?.Invoke();

        if (notifyQuestManager && QuestManager.Instance != null)
        {
            QuestManager.Instance.OnItemCollected(item, amount);
        }
    }

    public bool RemoveItem(ItemData item, int amount)
    {
        if (item == null || amount <= 0)
        {
            return false;
        }

        InventorySlot slot = slots.Find(candidate => candidate.item == item);
        if (slot == null || slot.amount < amount)
        {
            return false;
        }

        slot.amount -= amount;
        if (slot.amount <= 0)
        {
            slots.Remove(slot);
        }

        OnInventoryChanged?.Invoke();
        return true;
    }

    public bool HasItem(ItemData item, int amount)
    {
        return GetAmount(item) >= amount;
    }

    public int GetAmount(ItemData item)
    {
        if (item == null)
        {
            return 0;
        }

        InventorySlot slot = slots.Find(candidate => candidate.item == item);
        return slot == null ? 0 : slot.amount;
    }
}