#nullable enable
using System;
using Godot;
using System.Collections.Generic;
using System.Linq;
using Babushka.scripts.CSharp.Common.Savegame;
using Babushka.scripts.CSharp.GameEntity.LoadSave;
using Newtonsoft.Json.Linq;

namespace Babushka.scripts.CSharp.Common.Inventory;

public partial class InventoryInstance : IJsonSerializable
{
    private readonly List<InventorySlot> _slots;
    public IReadOnlyList<InventorySlot> Slots => _slots;

    public event Action? SlotAmountChanged;
    public event Action? InventoryContentsChanged;

    /// <summary>
    /// The total amount of InventorySlots in the inventory (empty and occupied).
    /// </summary>
    [Export]
    public int SlotAmount
    {
        get => _slots.Count;
        set
        {
            if (value < _slots.Count)
            {
                _slots.RemoveRange(value, _slots.Count - value);
            }
            else if (value > _slots.Count)
            {
                for (var i = _slots.Count; i < value; i++)
                {
                    _slots.Add(new InventorySlot());
                }
            }

            SlotAmountChanged?.Invoke();
        }
    }

    public InventoryInstance(int slotCount)
    {
        _slots = new();
        SlotAmount = slotCount;
    }

    public InventoryActionResult AddItem(ItemInstance newItem)
    {
        var result = AddItemAndStackRecursive(newItem, 0);
        InventoryContentsChanged?.Invoke();
        return result;
    }

    private InventoryActionResult AddItemAndStackRecursive(ItemInstance newItem, int slotSearch)
    {
        if (newItem.blueprint == null || newItem.amount == 0)
            return InventoryActionResult.SourceDoesNotExist;

        var slotIndex = -1;
        // find stackable slot
        for (var i = slotSearch; i < _slots.Count; i++)
        {
            if (_slots[i].itemInstance?.blueprint == newItem.blueprint)
            {
                slotIndex = i;
                break;
            }
        }

        if (slotIndex < 0)
        {
            // find empty slot
            for (var i = slotSearch; i < _slots.Count; i++)
            {
                if (_slots[i].IsEmpty())
                {
                    slotIndex = i;
                    break;
                }
            }
        }

        if (slotIndex < 0)
        {
            return InventoryActionResult.DestinationFull;
        }

        var itemInstance = _slots[slotIndex].itemInstance ??
                           new ItemInstance { blueprint = newItem.blueprint, amount = 0 };
        var maxStack = itemInstance!.blueprint.maxStack;
        var freeOnStack = maxStack - itemInstance.amount;
        var moveAmount = Math.Min(freeOnStack, newItem.amount);
        itemInstance.amount += moveAmount;
        newItem.amount -= moveAmount;
        _slots[slotIndex].itemInstance = itemInstance;
        return newItem.amount <= 0
            ? InventoryActionResult.Success
            : AddItemAndStackRecursive(newItem, slotIndex + 1);
    }

    public InventoryActionResult RemoveItem(int inventorySlot, out ItemInstance? itemInstance)
    {
        if (inventorySlot < 0 || inventorySlot >= _slots.Count)
        {
            itemInstance = null;
            return InventoryActionResult.SourceDoesNotExist;
        }

        if (_slots[inventorySlot].IsEmpty())
        {
            itemInstance = null;
            return InventoryActionResult.SourceIsEmpty;
        }

        itemInstance = _slots[inventorySlot].itemInstance;
        if (itemInstance == null)
            return InventoryActionResult.SourceDoesNotExist;

        itemInstance.amount -= 1;

        if (itemInstance.amount == 0)
            _slots[inventorySlot].itemInstance = null;

        InventoryContentsChanged?.Invoke();
        return InventoryActionResult.Success;
    }

    public InventoryActionResult RemoveItem(int inventorySlot)
    {
        return RemoveItem(inventorySlot, out _);
    }

    public InventoryActionResult TryRemoveAllItems(ItemInstance items)
    {
        var hasItemsCount = TotalItemsOfBlueprint(items.blueprint);
        if (hasItemsCount < items.amount)
            return InventoryActionResult.SourceDoesNotExist;

        var amountToRemove = items.amount;
        foreach (var s in _slots)
        {
            if (s.IsEmpty() || s.itemInstance!.blueprint != items.blueprint)
                continue;

            var slotItem = s.itemInstance!;
            if (slotItem.amount <= amountToRemove)
            {
                amountToRemove -= slotItem.amount;
                s.itemInstance = null;
            }
            else
            {
                slotItem.amount -= amountToRemove;
                amountToRemove = 0;
            }

            if (amountToRemove == 0)
                break;
        }

        InventoryContentsChanged?.Invoke();
        return InventoryActionResult.Success;
    }

    public InventoryActionResult AddItemToSlot(ItemInstance itemInstance, int destinationSlot)
    {
        if (destinationSlot < 0 || destinationSlot >= _slots.Count)
            return InventoryActionResult.DestinationDoesNotExist;

        if (!_slots[destinationSlot].IsEmpty())
            return InventoryActionResult.DestinationFull;

        _slots[destinationSlot].itemInstance = itemInstance;
        InventoryContentsChanged?.Invoke();
        return InventoryActionResult.Success;
    }

    public int TotalItemsOfBlueprint(ItemResource blueprint)
    {
        return _slots
            .Where(i => !i.IsEmpty() && i.itemInstance!.blueprint == blueprint)
            .Sum(i => i.itemInstance!.amount);
    }

    public bool HasItems(ItemInstance item)
    {
        return TotalItemsOfBlueprint(item.blueprint) >= item.amount;
    }

    public bool HasItems(IEnumerable<ItemInstance> items)
    {
        return items.All(HasItems);
    }

    public void LoadFromJson(JObject json)
    {
        var itemsArray = (JArray?)json["items"];
        if (itemsArray == null) return;

        foreach (var (itemToken, slot) in itemsArray.Zip(_slots))
        {
            var itemObj = (JObject?)itemToken;
            if (itemObj == null) continue;
            slot.LoadFromJson(itemObj);
        }

        InventoryContentsChanged?.Invoke();
    }

    public JObject SaveToJson()
    {
        return new JObject
        {
            ["items"] = new JArray(_slots.Select(s => s.SaveToJson()))
        };
    }
}