using System.Collections.Generic;
using UnityEngine;
using Object = UnityEngine.Object;

namespace SpellBoundAR.Items.Inventories.UI
{
    public class InventoryDisplay : MonoBehaviour
    {
        [SerializeField] private Object inventoryObject;
        [SerializeField] protected InventoryEntryDisplay entryPrefab;
        [SerializeField] protected Transform entriesParent;
        [SerializeField] private int minimumEntries = 9;
        [SerializeField] private bool ensureCountIsMultiple = false;
        [SerializeField] private int multiples = 1;

        [Header("Cache")]
        private IInventory _inventory;
        
        public IInventory Inventory
        {
            get
            {
                if (_inventory != null) return _inventory;
                OnValidate();
                return _inventory;
            }
            set
            {
                if (_inventory == value) return;
                if (_inventory != null) _inventory.OnEntriesChanged -= Refresh;
                _inventory = value;
                inventoryObject = value as Object;
                if (_inventory != null && isActiveAndEnabled) _inventory.OnEntriesChanged += Refresh;
                Refresh();
            }
        }

        private void ValidateInventoryObject()
        {
            if (inventoryObject is GameObject target) inventoryObject = target.GetComponent<IInventory>() as Object;
            if (inventoryObject is not IInventory) inventoryObject = null;
            _inventory = inventoryObject as IInventory;
        }

        private void OnValidate()
        {
            ValidateInventoryObject();
            if (minimumEntries < 0) minimumEntries = 0;
            if (multiples < 1) multiples = 1;
        }

        private void OnEnable()
        {
            if (Inventory != null) Inventory.OnEntriesChanged += Refresh;
            Refresh();
        }

        private void OnDisable()
        {
            if (Inventory != null) Inventory.OnEntriesChanged -= Refresh;
        }

        public void Refresh()
        {
            DestroyAllEntries();
            int entries = SpawnEntries();
            FillRemainingSlots(entries);
        }

        private void DestroyAllEntries()
        {
            if (!entriesParent) return;
            foreach (Transform entry in entriesParent)
            {
                if (!entry || !entry.gameObject) continue;
                Destroy(entry.gameObject);
            }
        }

        protected virtual bool SpawnEntry(IInventoryEntry entry)
        {
            if (!entryPrefab) return false;
            InventoryEntryDisplay instantiated = Instantiate(entryPrefab, entriesParent);
            if (!instantiated) return false;
            instantiated.Entry = entry;
            return true;
        }

        protected virtual int SpawnEntries()
        {            
            int count = 0;
            if (Inventory == null) return count;
            List<IInventoryEntry> entries = Inventory.GetAllEntries();
            foreach (IInventoryEntry entry in entries)
            {
                if (entry?.ItemTypeData == null || !entry.ItemTypeData.ShowInInventory) continue;
                if (SpawnEntry(entry)) count++;
            }
            return count;
        }

        private void FillRemainingSlots(int amountPresent)
        {
            while (amountPresent < minimumEntries
                   || ensureCountIsMultiple && amountPresent % multiples != 0)
            {
                SpawnEntry(null);
                amountPresent++;
            }
        }
    }
}