using System;
using System.Collections.Generic;
using OTGIntegrated.Core;
using OTGIntegrated.Items;
using UnityEngine;

namespace OTGIntegrated.Inventory
{
    public sealed class Inventory : MonoBehaviour
    {
        [SerializeField] private int maxSlots = 20;
        [SerializeField] private List<InventorySlot> slots = new List<InventorySlot>();

        public int MaxSlots => maxSlots;
        public event Action OnInventoryChanged;

        public bool AddItem(ItemData item, int amount)
        {
            if (!CanAddItem(item, amount))
            {
                GameEvents.RaiseNotification("Недостаточно места в инвентаре");
                return false;
            }

            AddItemInternal(item, amount);
            RaiseChanged();
            GameEvents.RaiseItemAdded(item, amount);
            GameEvents.RaiseNotification($"+{amount} {item.displayName}");
            return true;
        }

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

            int remaining = amount;
            for (int i = slots.Count - 1; i >= 0 && remaining > 0; i--)
            {
                InventorySlot slot = slots[i];
                if (slot == null || slot.item != item || slot.amount <= 0)
                {
                    continue;
                }

                int removed = Mathf.Min(slot.amount, remaining);
                slot.amount -= removed;
                remaining -= removed;

                if (slot.IsEmpty())
                {
                    slots.RemoveAt(i);
                }
            }

            RaiseChanged();
            GameEvents.RaiseItemRemoved(item, amount);
            return true;
        }

        public bool HasItem(ItemData item, int amount)
        {
            return item != null && amount > 0 && GetAmount(item) >= amount;
        }

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

            int total = 0;
            for (int i = 0; i < slots.Count; i++)
            {
                InventorySlot slot = slots[i];
                if (slot != null && slot.item == item && slot.amount > 0)
                {
                    total += slot.amount;
                }
            }

            return total;
        }

        public IReadOnlyList<InventorySlot> GetAllSlots()
        {
            return slots;
        }

        public void Clear()
        {
            slots.Clear();
            RaiseChanged();
        }

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

            int remaining = amount;
            int stackSize = Mathf.Max(1, item.maxStack);
            for (int i = 0; i < slots.Count; i++)
            {
                InventorySlot slot = slots[i];
                if (slot != null && slot.item == item && slot.amount > 0 && slot.amount < stackSize)
                {
                    remaining -= stackSize - slot.amount;
                    if (remaining <= 0)
                    {
                        return true;
                    }
                }
            }

            int freeSlots = Mathf.Max(0, maxSlots - slots.Count);
            int requiredSlots = Mathf.CeilToInt(remaining / (float)stackSize);
            return requiredSlots <= freeSlots;
        }

        public List<InventorySlotSaveData> SaveData()
        {
            List<InventorySlotSaveData> saveSlots = new List<InventorySlotSaveData>();
            for (int i = 0; i < slots.Count; i++)
            {
                InventorySlot slot = slots[i];
                if (slot == null || slot.IsEmpty())
                {
                    continue;
                }

                saveSlots.Add(new InventorySlotSaveData
                {
                    itemId = slot.item.itemId,
                    amount = slot.amount
                });
            }

            return saveSlots;
        }

        public void LoadData(List<InventorySlotSaveData> saveSlots, IEnumerable<ItemData> itemCatalog)
        {
            slots.Clear();
            Dictionary<string, ItemData> lookup = new Dictionary<string, ItemData>(StringComparer.Ordinal);
            if (itemCatalog != null)
            {
                foreach (ItemData item in itemCatalog)
                {
                    if (item != null && !string.IsNullOrWhiteSpace(item.itemId))
                    {
                        lookup[item.itemId] = item;
                    }
                }
            }

            if (saveSlots != null)
            {
                for (int i = 0; i < saveSlots.Count; i++)
                {
                    InventorySlotSaveData slot = saveSlots[i];
                    if (slot == null || string.IsNullOrWhiteSpace(slot.itemId) || slot.amount <= 0)
                    {
                        continue;
                    }

                    if (lookup.TryGetValue(slot.itemId, out ItemData item))
                    {
                        AddItemInternal(item, slot.amount);
                    }
                }
            }

            RaiseChanged();
        }

        private void AddItemInternal(ItemData item, int amount)
        {
            int remaining = amount;
            int stackSize = Mathf.Max(1, item.maxStack);

            for (int i = 0; i < slots.Count && remaining > 0; i++)
            {
                InventorySlot slot = slots[i];
                if (slot == null || slot.item != item || slot.amount >= stackSize)
                {
                    continue;
                }

                int added = Mathf.Min(stackSize - slot.amount, remaining);
                slot.amount += added;
                remaining -= added;
            }

            while (remaining > 0 && slots.Count < maxSlots)
            {
                int added = Mathf.Min(stackSize, remaining);
                slots.Add(new InventorySlot(item, added));
                remaining -= added;
            }
        }

        private void RaiseChanged()
        {
            OnInventoryChanged?.Invoke();
        }
    }
}