using UnityEngine;
using TMPro;
using Ashwild.Inventory;

namespace Ashwild.Storage
{
    /// <summary>
    /// The chest module of the inventory window: the right-side grid that shows the opened chest's
    /// contents, mirror of the hover-description module it replaces while a chest is open. It is a pure
    /// view driven by <see cref="InventoryUI"/> — it builds its grid of <see cref="SlotUI"/> cells from
    /// the bound chest's replicated view and refreshes them live, but it never routes transfers itself:
    /// every cell reports its drop to <see cref="InventoryUI.HandleSlotDrop"/>, which turns it into the
    /// matching server-authoritative deposit/withdraw/move on the <see cref="Chest"/>.
    /// </summary>
    [DisallowMultipleComponent]
    public class ChestPanelUI : MonoBehaviour
    {
        #region Serialized Fields

        [Header("Window")]
        [Tooltip("Root holder toggled on/off as the module is shown or hidden.")]
        [SerializeField] private GameObject root;
        [SerializeField] private TextMeshProUGUI titleText;

        [Header("Grid")]
        [Tooltip("Parent the chest cells are laid out under.")]
        [SerializeField] private Transform slotContainer;
        [Tooltip("Prefab carrying a SlotUI — the same cell used by the inventory grid and the hotbar.")]
        [SerializeField] private GameObject slotPrefab;

        #endregion

        #region State

        private SlotUI[] slots;
        private Chest boundChest;

        /// <summary>
        /// The chest currently shown (null while the module is hidden). Read by InventoryUI to route
        /// transfers.
        /// </summary>
        public Chest Chest => boundChest;

        #endregion

        #region Unity Lifecycle

        /// <summary>
        /// Parks the module hidden so it only appears once a chest is opened.
        /// </summary>
        private void Awake()
        {
            if (root != null) root.SetActive(false);
        }

        /// <summary>
        /// Unbinds the chest event if the module is torn down while open.
        /// </summary>
        private void OnDestroy()
        {
            if (boundChest != null) boundChest.SlotViewChanged -= HandleChestSlotChanged;
        }

        #endregion

        #region Show / Hide

        /// <summary>
        /// Binds a chest and shows the module: (re)builds the grid to the chest's slot count, subscribes
        /// to its replicated view so cells refresh live, sets the title and draws every cell.
        /// </summary>
        public void Bind(Chest chest)
        {
            if (boundChest != null) boundChest.SlotViewChanged -= HandleChestSlotChanged;

            boundChest = chest;
            if (root != null) root.SetActive(true);

            BuildGrid();

            if (boundChest != null)
            {
                boundChest.SlotViewChanged += HandleChestSlotChanged;
                if (titleText != null) titleText.text = boundChest.DisplayName;
            }

            RefreshAll();
        }

        /// <summary>
        /// Hides the module, unbinds the chest and releases it.
        /// </summary>
        public void Hide()
        {
            if (boundChest != null) boundChest.SlotViewChanged -= HandleChestSlotChanged;
            boundChest = null;
            if (root != null) root.SetActive(false);
        }

        #endregion

        #region Grid Building

        /// <summary>
        /// Builds (or rebuilds when the size differs) the grid to match the bound chest's slot count, so
        /// opening a small chest then a large one lays out the right number of cells.
        /// </summary>
        private void BuildGrid()
        {
            int count = boundChest != null ? boundChest.SlotCount : 0;
            if (slots != null && slots.Length == count) return;

            if (slots != null)
                foreach (SlotUI s in slots)
                    if (s != null) Destroy(s.gameObject);

            slots = new SlotUI[count];
            for (int i = 0; i < count; i++)
            {
                SlotUI slot = Instantiate(slotPrefab, slotContainer).GetComponent<SlotUI>();
                slot.Initialize(SlotContainer.Chest, i, InventoryUI.HandleSlotDrop, HandleChestSlotClicked);
                slots[i] = slot;
            }
        }

        #endregion

        #region Interaction

        /// <summary>
        /// Right-click on a chest cell quick-transfers its whole stack into the inventory (auto-placed).
        /// </summary>
        private void HandleChestSlotClicked(SlotContainer container, int index, bool rightClick)
        {
            if (!rightClick || boundChest == null) return;

            PredictEmptied(index);
            boundChest.RequestQuickTransfer(SlotContainer.Chest, index);
        }

        /// <summary>
        /// Draws a cell as emptied straight away, while its move is still in flight to the server.
        ///
        /// Emptying the chest travels on the SyncList (flushed at end of tick) but the matching grant is
        /// a TargetRpc (sent immediately), so the item would otherwise appear in the inventory a moment
        /// *before* leaving the chest — a visible double. This only repaints the cell: the authoritative
        /// model is untouched, so if the server disagrees (a co-op partner grabbed the stack first) the
        /// next replicated update simply paints the item back.
        /// </summary>
        public void PredictEmptied(int index)
        {
            if (slots == null || index < 0 || index >= slots.Length) return;
            slots[index].UpdateVisual((ItemData)null, 0, -1);
        }

        #endregion

        #region Refresh

        /// <summary>
        /// Refreshes a single cell, or the whole grid when the collection was (re)seeded (index -1).
        /// </summary>
        private void HandleChestSlotChanged(int index)
        {
            if (slots == null) return;
            if (index < 0) { RefreshAll(); return; }
            if (index < slots.Length) RefreshSlot(index);
        }

        /// <summary>
        /// Redraws every chest cell.
        /// </summary>
        private void RefreshAll()
        {
            if (slots == null) return;
            for (int i = 0; i < slots.Length; i++) RefreshSlot(i);
        }

        /// <summary>
        /// Draws one cell from the chest's replicated view, or empty when the slot holds nothing.
        /// </summary>
        private void RefreshSlot(int index)
        {
            if (boundChest != null && boundChest.TryGetSlot(index, out ItemData item, out int qty, out int uses))
                slots[index].UpdateVisual(item, qty, uses);
            else
                slots[index].UpdateVisual((ItemData)null, 0, -1);
        }

        #endregion
    }
}