using System.Collections.Generic;
using UnityEngine;

namespace Ashwild.Inventory
{
    /// <summary>
    /// Network-safe registry mapping every ItemData to a stable numeric id and back. Because
    /// ScriptableObject references cannot be sent over the network, the inventory syncs item ids
    /// instead and resolves them through this database. All machines share the same asset (same
    /// build → same order → same ids). Lives in a Resources folder so it loads without wiring.
    /// </summary>
    [CreateAssetMenu(fileName = "ItemDatabase", menuName = "Items/Item Database")]
    public class ItemDatabase : ScriptableObject
    {
        #region Serialized Fields

        /// <summary>
        /// All items, in a fixed order. The network id of an item is its index + 1 (0 = none).
        /// Rebuilt by Tools ▸ Ashwild ▸ Rebuild Item Database.
        /// </summary>
        [SerializeField] private ItemData[] items;

        #endregion

        #region State

        private static ItemDatabase instance;
        private Dictionary<ItemData, ushort> idByItem;

        #endregion

        #region Public API

        /// <summary>
        /// The shared database, lazily loaded from Resources/ItemDatabase.
        /// </summary>
        public static ItemDatabase Instance
        {
            get
            {
                if (instance == null)
                {
                    instance = Resources.Load<ItemDatabase>("ItemDatabase");
                    if (instance == null)
                        Debug.LogError("[ItemDatabase] No 'ItemDatabase' asset found in a Resources folder — run Tools ▸ Ashwild ▸ Rebuild Item Database.");
                    else
                        instance.BuildLookup();
                }
                return instance;
            }
        }

        /// <summary>
        /// All registered items, in id order.
        /// </summary>
        public ItemData[] Items => items;

        /// <summary>
        /// Returns the network id of an item (0 when null or not registered).
        /// </summary>
        public ushort GetId(ItemData item)
        {
            if (item == null) return 0;
            if (idByItem == null) BuildLookup();
            return idByItem.TryGetValue(item, out ushort id) ? id : (ushort)0;
        }

        /// <summary>
        /// Resolves a network id back to its ItemData (null when id is 0 or out of range).
        /// </summary>
        public ItemData GetItem(ushort id)
        {
            if (id == 0 || items == null || id > items.Length) return null;
            return items[id - 1];
        }

        #endregion

        #region Internal Helpers

        /// <summary>
        /// (Re)builds the item → id lookup from the serialized array.
        /// </summary>
        private void BuildLookup()
        {
            idByItem = new Dictionary<ItemData, ushort>();
            if (items == null) return;

            for (int i = 0; i < items.Length; i++)
                if (items[i] != null) idByItem[items[i]] = (ushort)(i + 1);
        }

        #endregion

    #if UNITY_EDITOR
        /// <summary>
        /// Editor-only: replaces the item list (used by the rebuild tool).
        /// </summary>
        public void EditorSetItems(ItemData[] all)
        {
            items = all;
        }
    #endif
    }
}