using System;
using FishNet.Connection;
using FishNet.Object;
using FishNet.Object.Synchronizing;
using UnityEngine;
using Ashwild.Interaction;
using Ashwild.Inventory;

namespace Ashwild.Storage
{
    /// <summary>
    /// A networked storage chest and the single IInteractable that opens it. Interacting opens the
    /// inventory window in chest mode (the player's inventory on the left, this chest's module on the
    /// right); all item moves are requested through server RPCs.
    ///
    /// Multiplayer: the chest is **server-authoritative** so two players browsing the same chest can
    /// never clobber or duplicate items. The server owns the rich model (<see cref="InventorySlot"/>[])
    /// and replicates a compact per-slot view (<see cref="ChestSlotView"/>: item id + quantity + uses)
    /// through a SyncList that every client renders from. The player inventory itself stays
    /// client-authoritative: depositing removes the item locally then asks the server to store it
    /// (refunded if it no longer fits), and withdrawing has the server grant the item back through
    /// <see cref="PlayerInventory.GrantItemFromServer"/> — mirroring the CookingStation pattern.
    /// </summary>
    [DisallowMultipleComponent]
    [RequireComponent(typeof(NetworkObject))]
    public class Chest : NetworkBehaviour, IInteractable
    {
        #region Types

        /// <summary>
        /// Replicated per-slot view: the stored item's network id (0 = empty), how many, and the
        /// remaining uses of a uses-tracked instance (-1 for items without a uses bar). Clients render
        /// the slot from this; the authoritative model stays server-side.
        /// </summary>
        public struct ChestSlotView
        {
            public ushort rawId;
            public int quantity;
            public int uses;
        }

        #endregion

        #region Serialized Fields

        [Header("Data")]
        [Tooltip("Authoring data for this chest: slot count, title and grid width.")]
        [SerializeField] private ChestData data;

        #endregion

        #region Networked State

        /// <summary>
        /// One view per storage slot, seeded server-side and replicated to every client. The UI reads
        /// this on both the server and clients so a host and a pure client render identically.
        /// </summary>
        private readonly SyncList<ChestSlotView> slotViews = new SyncList<ChestSlotView>();

        #endregion

        #region Server State

        /// <summary>
        /// Server-only authoritative contents, parallel to <see cref="slotViews"/>. Null on clients,
        /// which never read it — every mutation happens inside a ServerRpc body.
        /// </summary>
        private InventorySlot[] slots;

        #endregion

        #region Events

        /// <summary>
        /// Fired when a slot's replicated view changes so the open <see cref="ChestPanelUI"/> can refresh
        /// just that cell. An index of -1 means the whole collection changed (a full refresh).
        /// </summary>
        public event Action<int> SlotViewChanged;

        #endregion

        #region Public API

        /// <summary>
        /// Number of storage slots this chest exposes, taken from its data (falls back to the
        /// replicated view count if the data is missing).
        /// </summary>
        public int SlotCount => data != null ? data.SlotCount : slotViews.Count;

        /// <summary>
        /// Title shown at the top of the chest window.
        /// </summary>
        public string DisplayName => data != null ? data.DisplayName : "Coffre";

        #endregion

        #region Unity Lifecycle

        /// <summary>
        /// Warns early when the chest has no data, so a misconfigured prefab is obvious in the console.
        /// </summary>
        private void Awake()
        {
            if (data == null)
                Debug.LogError($"[Chest] '{name}' has no ChestData assigned — the chest will have no slots.", this);
        }

        #endregion

        #region Network Lifecycle

        /// <summary>
        /// Subscribes to the replicated state so the open window follows it on every machine.
        /// </summary>
        public override void OnStartNetwork()
        {
            base.OnStartNetwork();
            slotViews.OnChange += OnSlotViewChanged;
        }

        /// <summary>
        /// Server-side: builds the authoritative slot model and seeds one empty view per slot so
        /// clients receive a correctly sized collection.
        /// </summary>
        public override void OnStartServer()
        {
            base.OnStartServer();

            int count = data != null ? data.SlotCount : 0;
            slots = new InventorySlot[count];
            for (int i = 0; i < count; i++) slots[i] = new InventorySlot();

            slotViews.Clear();
            for (int i = 0; i < count; i++)
                slotViews.Add(new ChestSlotView { rawId = 0, quantity = 0, uses = -1 });
        }

        /// <summary>
        /// Unsubscribes — mirrors OnStartNetwork exactly.
        /// </summary>
        public override void OnStopNetwork()
        {
            base.OnStopNetwork();
            slotViews.OnChange -= OnSlotViewChanged;
        }

        #endregion

        #region IInteractable

        /// <summary>
        /// Prompt shown while aiming at the chest.
        /// </summary>
        public string InteractionPrompt => $"Ouvrir {DisplayName}";

        /// <summary>
        /// Opens the inventory window in chest mode, bound to this chest. Runs on the interacting client
        /// only.
        /// </summary>
        public void Interact()
        {
            if (InventoryUI.Instance == null)
            {
                Debug.LogError("[Chest] No InventoryUI found in the scene — cannot open the chest.", this);
                return;
            }
            InventoryUI.Instance.OpenChest(this);
        }

        #endregion

        #region View Access

        /// <summary>
        /// Resolves a slot's stored item from the replicated view. Returns false for an empty slot or
        /// an unknown id. Safe on server and clients (both read the replicated view).
        /// </summary>
        public bool TryGetSlot(int index, out ItemData item, out int quantity, out int uses)
        {
            item = null;
            quantity = 0;
            uses = -1;

            if (index < 0 || index >= slotViews.Count) return false;

            ChestSlotView v = slotViews[index];
            if (v.rawId == 0) return false;

            item = ItemDatabase.Instance != null ? ItemDatabase.Instance.GetItem(v.rawId) : null;
            if (item == null) return false;

            quantity = v.quantity;
            uses = v.uses;
            return true;
        }

        #endregion

        #region Client Requests

        /// <summary>
        /// The one drag-and-drop operation for anything involving this chest: chest→inventory,
        /// inventory→chest and chest→chest, in either direction. It never decides *what* happens — the
        /// shared <see cref="SlotTransfer.Move"/> rules do — so dropping a stack on a chest cell behaves
        /// exactly like dropping it on an inventory cell (move, merge or swap).
        ///
        /// For a cross-container move the player's slot is read and cleared locally (the inventory is
        /// client-authoritative) and sent along as a payload; the server reconciles it against the chest
        /// slot and grants whatever comes back into that same slot, which is why an item never lands
        /// somewhere unexpected like the first free hotbar cell.
        /// </summary>
        public void RequestMove(SlotContainer fromContainer, int fromIndex, SlotContainer toContainer, int toIndex)
        {
            if (fromContainer == SlotContainer.Chest && toContainer == SlotContainer.Chest)
            {
                if (fromIndex != toIndex) MoveWithinServerRpc(fromIndex, toIndex);
                return;
            }

            PlayerInventory inv = PlayerInventory.Instance;
            if (inv == null) return;

            bool chestIsSource = fromContainer == SlotContainer.Chest;
            int chestIndex = chestIsSource ? fromIndex : toIndex;
            int inventoryIndex = chestIsSource ? toIndex : fromIndex;

            if (chestIndex < 0 || chestIndex >= slotViews.Count) return;
            if (inv.GetSlot(inventoryIndex) == null) return;

            SlotContent payload = inv.ReadSlot(inventoryIndex);
            bool chestSlotFilled = TryGetSlot(chestIndex, out _, out _, out _);

            // Nothing to move: the side the player dragged from is empty.
            if (chestIsSource ? !chestSlotFilled : payload.IsEmpty) return;

            ushort id = 0;
            if (!payload.IsEmpty)
            {
                id = ItemDatabase.Instance != null ? ItemDatabase.Instance.GetId(payload.Item) : (ushort)0;
                if (id == 0)
                {
                    Debug.LogError($"[Chest] '{payload.Item.ItemName}' is not in the ItemDatabase — cannot store. Run Rebuild Item Database.", this);
                    return;
                }
                inv.WriteSlot(inventoryIndex, SlotContent.Empty);
            }

            MoveCrossServerRpc(chestIndex, inventoryIndex, chestIsSource, id, payload.Quantity, payload.Uses);
        }

        /// <summary>
        /// Quick transfer (right-click): sends a stack to the other container without the player picking a
        /// destination, so it is auto-placed into the first slot that accepts it. Deliberately a different
        /// operation from <see cref="RequestMove"/> — here the player expressed no target.
        /// </summary>
        public void RequestQuickTransfer(SlotContainer fromContainer, int index)
        {
            PlayerInventory inv = PlayerInventory.Instance;
            if (inv == null) return;

            if (fromContainer == SlotContainer.Chest)
            {
                if (!TryGetSlot(index, out ItemData item, out int quantity, out _)) return;
                if (!inv.CanFit(item, quantity))
                {
                    Debug.LogWarning($"[Chest] Inventaire plein — impossible de retirer '{item.ItemName}'.", this);
                    return;
                }
                QuickWithdrawServerRpc(index);
                return;
            }

            SlotContent content = inv.ReadSlot(index);
            if (content.IsEmpty) return;

            ushort id = ItemDatabase.Instance != null ? ItemDatabase.Instance.GetId(content.Item) : (ushort)0;
            if (id == 0)
            {
                Debug.LogError($"[Chest] '{content.Item.ItemName}' is not in the ItemDatabase — cannot store. Run Rebuild Item Database.", this);
                return;
            }

            inv.WriteSlot(index, SlotContent.Empty);
            QuickDepositServerRpc(id, content.Quantity, content.Uses, index);
        }

        /// <summary>
        /// Stores every inventory stack in the chest, auto-placing each. Safe: the server refunds whatever
        /// does not fit back to the slot it came from.
        /// </summary>
        public void RequestDepositAll()
        {
            PlayerInventory inv = PlayerInventory.Instance;
            if (inv == null) return;

            for (int i = 0; i < inv.InventorySize; i++)
                RequestQuickTransfer(SlotContainer.Inventory, i);
        }

        /// <summary>
        /// Takes every chest stack into the inventory. Each slot is CanFit-checked as it goes; because the
        /// grants come back asynchronously the checks do not account for items still in flight, so a chest
        /// larger than the free inventory space may leave some items behind.
        /// </summary>
        public void RequestWithdrawAll()
        {
            for (int i = 0; i < slotViews.Count; i++)
                RequestQuickTransfer(SlotContainer.Chest, i);
        }

        #endregion

        #region Server RPCs

        /// <summary>
        /// Server-side chest-to-chest move: both slots are ours, so the shared rules run straight on the
        /// authoritative model.
        /// </summary>
        [ServerRpc(RequireOwnership = false)]
        private void MoveWithinServerRpc(int fromIndex, int toIndex)
        {
            if (fromIndex < 0 || fromIndex >= slots.Length) return;
            if (toIndex < 0 || toIndex >= slots.Length) return;

            SlotContent from = ReadServerSlot(fromIndex);
            SlotContent to = ReadServerSlot(toIndex);

            if (!SlotTransfer.Move(ref from, ref to)) return;

            WriteServerSlot(fromIndex, from);
            WriteServerSlot(toIndex, to);
        }

        /// <summary>
        /// Server-side inventory↔chest move, both directions. The player's slot arrives as a payload (empty
        /// when they dragged onto an empty cell); the same rules that drive an inventory-to-inventory drag
        /// decide between move, merge and swap, then whatever ends up on the player's side is granted back
        /// into the exact slot they used. An out-of-range chest index refunds the payload rather than
        /// swallowing it.
        /// </summary>
        [ServerRpc(RequireOwnership = false)]
        private void MoveCrossServerRpc(int chestIndex, int inventoryIndex, bool chestIsSource, ushort id, int quantity, int uses, NetworkConnection conn = null)
        {
            ItemData payloadItem = id != 0 && ItemDatabase.Instance != null ? ItemDatabase.Instance.GetItem(id) : null;
            SlotContent playerContent = SlotContent.Of(payloadItem, quantity, uses);

            if (chestIndex < 0 || chestIndex >= slots.Length)
            {
                GrantBack(conn, playerContent, inventoryIndex);
                return;
            }

            SlotContent chestContent = ReadServerSlot(chestIndex);

            if (chestIsSource) SlotTransfer.Move(ref chestContent, ref playerContent);
            else SlotTransfer.Move(ref playerContent, ref chestContent);

            WriteServerSlot(chestIndex, chestContent);
            GrantBack(conn, playerContent, inventoryIndex);
        }

        /// <summary>
        /// Server-side quick deposit: auto-places the incoming stack and refunds any leftover to the slot
        /// it was taken from.
        /// </summary>
        [ServerRpc(RequireOwnership = false)]
        private void QuickDepositServerRpc(ushort id, int quantity, int uses, int originIndex, NetworkConnection conn = null)
        {
            ItemData item = ItemDatabase.Instance != null ? ItemDatabase.Instance.GetItem(id) : null;
            SlotContent incoming = SlotContent.Of(item, quantity, uses);
            if (incoming.IsEmpty) return;

            AutoPlace(ref incoming);
            GrantBack(conn, incoming, originIndex);
        }

        /// <summary>
        /// Server-side quick withdraw: empties the chest slot and lets the player's inventory auto-place it.
        /// </summary>
        [ServerRpc(RequireOwnership = false)]
        private void QuickWithdrawServerRpc(int chestIndex, NetworkConnection conn = null)
        {
            if (chestIndex < 0 || chestIndex >= slots.Length) return;

            SlotContent content = ReadServerSlot(chestIndex);
            if (content.IsEmpty) return;

            WriteServerSlot(chestIndex, SlotContent.Empty);
            GrantBack(conn, content, -1);
        }

        #endregion

        #region Server Helpers

        /// <summary>
        /// Auto-places a stack into the chest through the shared rule: merge into matching stacks first,
        /// then fill empty slots. Never swaps — the player picked no destination. Whatever does not fit is
        /// left in <paramref name="incoming"/> for the caller to refund.
        /// </summary>
        private void AutoPlace(ref SlotContent incoming)
        {
            for (int i = 0; i < slots.Length && !incoming.IsEmpty; i++)
                if (!slots[i].IsEmpty) StackIntoSlot(i, ref incoming);

            for (int i = 0; i < slots.Length && !incoming.IsEmpty; i++)
                if (slots[i].IsEmpty) StackIntoSlot(i, ref incoming);
        }

        /// <summary>
        /// Pushes as much of the incoming stack as one chest slot accepts, writing it back when it changed.
        /// </summary>
        private void StackIntoSlot(int index, ref SlotContent incoming)
        {
            SlotContent target = ReadServerSlot(index);
            if (!SlotTransfer.TryStack(ref incoming, ref target)) return;
            WriteServerSlot(index, target);
        }

        /// <summary>
        /// Reads a chest slot from the authoritative model as a container-agnostic snapshot.
        /// </summary>
        private SlotContent ReadServerSlot(int index)
        {
            InventorySlot s = slots[index];
            if (s.IsEmpty) return SlotContent.Empty;
            return SlotContent.Of(s.ItemData, s.Quantity, s.CurrentUses);
        }

        /// <summary>
        /// Writes a snapshot into the authoritative model and pushes it into the replicated view in one
        /// step, so the two can never drift apart. Carries the remaining uses, so a worn tool stored in a
        /// chest comes back out just as worn.
        /// </summary>
        private void WriteServerSlot(int index, SlotContent content)
        {
            InventorySlot s = slots[index];

            if (content.IsEmpty)
            {
                s.Clear();
                slotViews[index] = new ChestSlotView { rawId = 0, quantity = 0, uses = -1 };
                return;
            }

            s.Set(content.Item, content.Quantity, content.Uses);

            ushort id = ItemDatabase.Instance != null ? ItemDatabase.Instance.GetId(content.Item) : (ushort)0;
            slotViews[index] = new ChestSlotView { rawId = id, quantity = content.Quantity, uses = content.Uses };
        }

        /// <summary>
        /// Grants a stack to the requesting player's (client-authoritative) inventory. No-op when empty.
        /// <paramref name="preferredIndex"/> is the slot the player used, so a refund or a swapped-out
        /// stack returns exactly there instead of auto-filling the first free slot (the hotbar). Negative
        /// means auto-place. Always flagged as a transfer: taking a stack out of a chest is shuffling
        /// items between the player's own containers, not a gain, so the HUD must not announce it.
        /// </summary>
        private void GrantBack(NetworkConnection conn, SlotContent content, int preferredIndex)
        {
            if (content.IsEmpty) return;
            PlayerInventory inv = ResolveInventory(conn);
            if (inv != null) inv.GrantItemFromServer(content.Item, content.Quantity, content.Uses, preferredIndex, isTransfer: true);
        }

        /// <summary>
        /// Returns the PlayerInventory on the player object owned by the given connection.
        /// </summary>
        private PlayerInventory ResolveInventory(NetworkConnection conn)
        {
            NetworkObject playerObject = conn != null ? conn.FirstObject : null;
            return playerObject != null ? playerObject.GetComponent<PlayerInventory>() : null;
        }

        #endregion

        #region Replication Handlers

        /// <summary>
        /// Forwards a replicated slot change to the open window: a single index for point edits, or -1
        /// when the whole collection is (re)seeded on join.
        /// </summary>
        private void OnSlotViewChanged(SyncListOperation op, int index, ChestSlotView oldItem, ChestSlotView newItem, bool asServer)
        {
            switch (op)
            {
                case SyncListOperation.Add:
                case SyncListOperation.Insert:
                case SyncListOperation.Set:
                case SyncListOperation.RemoveAt:
                    SlotViewChanged?.Invoke(index);
                    break;

                case SyncListOperation.Clear:
                case SyncListOperation.Complete:
                    SlotViewChanged?.Invoke(-1);
                    break;
            }
        }

        #endregion
    }
}