using System.Collections.Generic;
using UnityEngine;

namespace Ashwild.Building
{
    /// <summary>
    /// Network-safe registry mapping every BuildableData to a stable numeric id and back. Because
    /// ScriptableObject references cannot be sent over the network, the build registry syncs 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.
    /// Mirrors ItemDatabase. Rebuilt by Tools ▸ Ashwild ▸ Rebuild Buildable Database.
    /// </summary>
    [CreateAssetMenu(fileName = "BuildableDatabase", menuName = "Building/Buildable Database")]
    public class BuildableDatabase : ScriptableObject
    {
        #region Serialized Fields

        /// <summary>
        /// All buildables, in a fixed order. The network id of a buildable is its index + 1 (0 = none).
        /// </summary>
        [SerializeField] private BuildableData[] buildables;

        #endregion

        #region State

        private static BuildableDatabase instance;
        private Dictionary<BuildableData, ushort> idByBuildable;

        #endregion

        #region Public API

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

        /// <summary>
        /// All registered buildables, in id order.
        /// </summary>
        public BuildableData[] Buildables => buildables;

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

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

        #endregion

        #region Internal Helpers

        /// <summary>
        /// (Re)builds the buildable → id lookup from the serialized array.
        /// </summary>
        private void BuildLookup()
        {
            idByBuildable = new Dictionary<BuildableData, ushort>();
            if (buildables == null) return;

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

        #endregion

    #if UNITY_EDITOR
        /// <summary>
        /// Editor-only: replaces the buildable list (used by the rebuild tool).
        /// </summary>
        public void EditorSetBuildables(BuildableData[] all)
        {
            buildables = all;
        }
    #endif
    }
}