using System.Collections.Generic;
using FishNet.Connection;
using FishNet.Object;
using FishNet.Object.Synchronizing;
using UnityEngine;
using Ashwild.Inventory;

namespace Ashwild.Network
{
    /// <summary>
    /// Registry for Pickables. On top of the shared WorldObjectRegistry plumbing (claimed scene ids,
    /// hide/show, catch-up) it adds runtime drops: a synced dictionary of active drops so every client
    /// spawns the same local visual, and the server-authoritative pickup/drop RPCs that grant items to
    /// the requesting player. One per scene.
    /// </summary>
    public class PickableRegistry : WorldObjectRegistry
    {
        #region Types

        /// <summary>
        /// Synced description of a runtime drop so all clients spawn the same local visual.
        /// </summary>
        public struct DropRecord
        {
            public ushort itemId;
            public int quantity;
            public Vector3 position;
            public Quaternion rotation;
        }

        #endregion

        #region Singleton

        /// <summary>
        /// The pickup registry for the active game scene.
        /// </summary>
        public static PickableRegistry Instance { get; private set; }

        #endregion

        #region State

        /// <summary>
        /// Active runtime drops, keyed by a negative drop id.
        /// </summary>
        private readonly SyncDictionary<int, DropRecord> activeDrops = new SyncDictionary<int, DropRecord>();

        /// <summary>
        /// Local visuals instantiated for active drops, keyed by drop id.
        /// </summary>
        private readonly Dictionary<int, Pickable> dropInstances = new Dictionary<int, Pickable>();

        /// <summary>
        /// Server-side counter for the negative drop-id space.
        /// </summary>
        private int nextDropId = -1;

        #endregion

        #region Lifecycle

        protected override void Awake()
        {
            base.Awake();
            if (Instance != null && Instance != this)
            {
                Destroy(this);
                return;
            }
            Instance = this;
        }

        protected override void OnDestroy()
        {
            base.OnDestroy();
            if (Instance == this) Instance = null;
        }

        public override void OnStartNetwork()
        {
            base.OnStartNetwork();
            activeDrops.OnChange += OnDropsChanged;
        }

        public override void OnStartClient()
        {
            base.OnStartClient();
            foreach (KeyValuePair<int, DropRecord> kv in activeDrops.Collection)
                SpawnDropVisual(kv.Key, kv.Value);
        }

        public override void OnStopNetwork()
        {
            base.OnStopNetwork();
            activeDrops.OnChange -= OnDropsChanged;
        }

        #endregion

        #region Public API

        /// <summary>
        /// Returns whether a pickup (scene id >= 0 or drop id < 0) is no longer available.
        /// </summary>
        public bool IsClaimed(int id)
        {
            if (id >= 0) return IsInactive(id);
            return !activeDrops.ContainsKey(id);
        }

        /// <summary>
        /// Owner-side entry: asks the server to claim a pickup and grant its item.
        /// </summary>
        [ServerRpc(RequireOwnership = false)]
        public void RequestPickupServerRpc(int id, NetworkConnection conn = null)
        {
            PlayerInventory inventory = ResolveInventory(conn);
            if (inventory == null) return;

            if (id >= 0)
            {
                // Scene pickup — the server reads the item from its own copy of the object.
                if (IsInactive(id)) return;
                if (!TryGetObject(id, out WorldObject obj) || obj is not Pickable pickup) return;
                if (pickup.ItemData == null) return;

                MarkInactive(id);
                inventory.GrantItemFromServer(pickup.ItemData, pickup.Quantity);
            }
            else
            {
                // Runtime drop — the server reads the item from the synced record.
                if (!activeDrops.TryGetValue(id, out DropRecord record)) return;
                ItemData item = ItemDatabase.Instance != null ? ItemDatabase.Instance.GetItem(record.itemId) : null;

                activeDrops.Remove(id);
                if (item != null) inventory.GrantItemFromServer(item, record.quantity);
            }
        }

        /// <summary>
        /// Owner-side entry: asks the server to spawn a dropped item into the world.
        /// </summary>
        [ServerRpc(RequireOwnership = false)]
        public void RequestDropServerRpc(ushort itemId, int quantity, Vector3 position, Quaternion rotation, NetworkConnection conn = null)
        {
            if (ItemDatabase.Instance == null || ItemDatabase.Instance.GetItem(itemId) == null) return;

            int dropId = nextDropId--;
            activeDrops.Add(dropId, new DropRecord
            {
                itemId = itemId,
                quantity = quantity,
                position = position,
                rotation = rotation
            });
        }

        #endregion

        #region Internal Helpers

        /// <summary>
        /// Spawns or removes a drop visual when the active-drops dictionary changes.
        /// </summary>
        private void OnDropsChanged(SyncDictionaryOperation op, int id, DropRecord record, bool asServer)
        {
            if (op == SyncDictionaryOperation.Add) SpawnDropVisual(id, record);
            else if (op == SyncDictionaryOperation.Remove) RemoveDropVisual(id);
        }

        /// <summary>
        /// Instantiates the local visual for a drop (idempotent).
        /// </summary>
        private void SpawnDropVisual(int id, DropRecord record)
        {
            if (dropInstances.ContainsKey(id)) return;

            ItemData item = ItemDatabase.Instance != null ? ItemDatabase.Instance.GetItem(record.itemId) : null;
            if (item == null || item.WorldPrefab == null) return;

            GameObject go = Instantiate(item.WorldPrefab, record.position, record.rotation);
            Pickable pickup = go.GetComponent<Pickable>();
            if (pickup != null) pickup.InitializeAsDrop(id, item, record.quantity);
            dropInstances[id] = pickup;
        }

        /// <summary>
        /// Destroys the local visual for a claimed/removed drop.
        /// </summary>
        private void RemoveDropVisual(int id)
        {
            if (dropInstances.TryGetValue(id, out Pickable pickup))
            {
                if (pickup != null) Destroy(pickup.gameObject);
                dropInstances.Remove(id);
            }
        }

        #endregion
    }
}