using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;
using TMPro;
using System;

namespace Ashwild.Inventory
{
    /// <summary>
    /// Which container a slot cell maps to, so a drop can be routed to the right operation: a plain
    /// inventory swap, or a deposit/withdraw/move when a chest is involved.
    /// </summary>
    public enum SlotContainer
    {
        Inventory,
        Chest
    }

    /// <summary>
    /// One draggable slot cell, used everywhere the same way: the inventory grid, the hotbar and the
    /// chest module. It is a dumb view — it renders whatever it is handed and reports its drags, clicks
    /// and hovers back to a manager as a (container, index) pair; it never mutates any model itself.
    /// The manager turns a drop into the matching operation (swap, deposit, withdraw, move).
    /// </summary>
    public class SlotUI : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler, IDropHandler, IPointerClickHandler, IPointerEnterHandler, IPointerExitHandler
    {
        #region Serialized Fields

        [Header("References")]
        [SerializeField] private Image iconImage;
        [SerializeField] private TextMeshProUGUI quantityText;
        [SerializeField] private Image highlightImage;

        [Header("Uses Bar")]
        [Tooltip("Root object of the uses/durability bar — shown only for items that track uses.")]
        [SerializeField] private GameObject usageBarRoot;
        [Tooltip("Filled image whose fillAmount maps to the remaining uses (Image Type = Filled).")]
        [SerializeField] private Image usageBarFill;
        [Tooltip("Icon tint applied when the item still has uses left.")]
        [SerializeField] private Color normalTint = Color.white;
        [Tooltip("Icon (and bar) tint applied when the item is depleted — a broken repairable tool / empty container.")]
        [SerializeField] private Color depletedTint = Color.red;

        #endregion

        #region State

        private SlotContainer container;
        private int slotIndex;
        private bool hasItem;

        private Action<SlotContainer, int, SlotContainer, int> onDrop;
        private Action<SlotContainer, int, bool> onClicked;
        private Action<SlotContainer, int> onHoverEnter;
        private Action onHoverExit;

        public int SlotIndex => slotIndex;
        public SlotContainer Container => container;

        // Static drag state shared across every cell (inventory, hotbar and chest grids).
        private static SlotUI draggedSlot;
        private static GameObject ghostObject;
        private static Image ghostIcon;
        private static TextMeshProUGUI ghostQuantity;

        #endregion

        #region Setup

        /// <summary>
        /// Wires the single shared drag ghost used by every slot cell in the scene.
        /// </summary>
        public static void SetupGhost(GameObject ghost, Image icon, TextMeshProUGUI qty)
        {
            ghostObject = ghost;
            ghostIcon = icon;
            ghostQuantity = qty;
            if (ghostObject != null) ghostObject.SetActive(false);
        }

        /// <summary>
        /// Binds this cell to a container and index and the manager callbacks it reports interactions to.
        /// Drops carry both the dragged and the target (container, index) so the manager can route them.
        /// </summary>
        public void Initialize(SlotContainer slotContainer, int index,
            Action<SlotContainer, int, SlotContainer, int> dropCallback,
            Action<SlotContainer, int, bool> clickCallback,
            Action<SlotContainer, int> hoverEnterCallback = null,
            Action hoverExitCallback = null)
        {
            container = slotContainer;
            slotIndex = index;
            onDrop = dropCallback;
            onClicked = clickCallback;
            onHoverEnter = hoverEnterCallback;
            onHoverExit = hoverExitCallback;
        }

        #endregion

        #region Rendering

        /// <summary>
        /// Redraws the cell from an inventory slot (the local, client-authoritative container).
        /// </summary>
        public void UpdateVisual(InventorySlot slot)
        {
            if (slot == null || slot.IsEmpty)
            {
                RenderEmpty();
                return;
            }

            ItemData item = slot.ItemData;
            bool hasUses = item.HasUses;
            float fill = hasUses && item.MaxUses > 0 ? (float)slot.CurrentUses / item.MaxUses : 0f;
            RenderItem(item.Icon, slot.Quantity, hasUses, hasUses && slot.IsDepleted, fill);
        }

        /// <summary>
        /// Redraws the cell from a resolved chest view (item + quantity + remaining uses). A null item
        /// renders the empty look. Uses -1 for items that do not track uses.
        /// </summary>
        public void UpdateVisual(ItemData item, int quantity, int uses)
        {
            if (item == null)
            {
                RenderEmpty();
                return;
            }

            bool hasUses = item.HasUses;
            bool depleted = hasUses && uses <= 0;
            float fill = hasUses && item.MaxUses > 0 ? (float)Mathf.Max(0, uses) / item.MaxUses : 0f;
            RenderItem(item.Icon, quantity, hasUses, depleted, fill);
        }

        /// <summary>
        /// Draws an item: icon, quantity (hidden for single stacks) and the uses bar. Preserves the
        /// current icon alpha so a mid-drag fade survives a refresh, and tints the icon red when
        /// depleted. Shared by both the inventory and the chest render paths.
        /// </summary>
        private void RenderItem(Sprite icon, int quantity, bool hasUses, bool depleted, float fill)
        {
            hasItem = true;

            iconImage.gameObject.SetActive(true);
            iconImage.sprite = icon;

            bool showQty = quantity > 1;
            quantityText.gameObject.SetActive(showQty);
            if (showQty) quantityText.text = quantity.ToString();

            if (usageBarRoot != null) usageBarRoot.SetActive(hasUses);

            Color tint = depleted ? depletedTint : normalTint;
            tint.a = iconImage.color.a;
            iconImage.color = tint;

            if (hasUses && usageBarFill != null) usageBarFill.fillAmount = fill;
        }

        /// <summary>
        /// Clears the cell to its empty look.
        /// </summary>
        private void RenderEmpty()
        {
            hasItem = false;
            iconImage.gameObject.SetActive(false);
            quantityText.gameObject.SetActive(false);
            if (usageBarRoot != null) usageBarRoot.SetActive(false);
        }

        /// <summary>
        /// Toggles the selection highlight (used by the hotbar for the active slot).
        /// </summary>
        public void SetSelected(bool selected)
        {
            if (highlightImage != null)
                highlightImage.gameObject.SetActive(selected);
        }

        #endregion

        #region Drag & Drop

        /// <summary>
        /// Starts dragging this cell's stack (left button, non-empty only), building the shared ghost
        /// from what the cell currently shows — container-agnostic, so inventory and chest cells drag
        /// identically.
        /// </summary>
        public void OnBeginDrag(PointerEventData eventData)
        {
            if (eventData.button != PointerEventData.InputButton.Left) return;
            if (!hasItem) return;

            draggedSlot = this;

            if (ghostObject != null)
            {
                ghostObject.SetActive(true);
                ghostIcon.sprite = iconImage.sprite;
                ghostIcon.gameObject.SetActive(true);

                bool showQty = quantityText.gameObject.activeSelf;
                ghostQuantity.gameObject.SetActive(showQty);
                if (showQty) ghostQuantity.text = quantityText.text;

                ghostObject.transform.position = eventData.position;
            }

            Color c = iconImage.color;
            c.a = 0.4f;
            iconImage.color = c;
        }

        /// <summary>
        /// Moves the ghost with the pointer.
        /// </summary>
        public void OnDrag(PointerEventData eventData)
        {
            if (draggedSlot != this) return;
            if (ghostObject != null) ghostObject.transform.position = eventData.position;
        }

        /// <summary>
        /// Ends the drag: hides the ghost and restores the source cell's opacity.
        /// </summary>
        public void OnEndDrag(PointerEventData eventData)
        {
            if (draggedSlot != this) return;

            if (ghostObject != null) ghostObject.SetActive(false);

            Color c = iconImage.color;
            c.a = 1f;
            iconImage.color = c;

            draggedSlot = null;
        }

        /// <summary>
        /// Drop target: reports the dragged and target (container, index) so the manager routes the
        /// transfer (swap, deposit, withdraw or move).
        /// </summary>
        public void OnDrop(PointerEventData eventData)
        {
            if (draggedSlot == null || draggedSlot == this) return;
            onDrop?.Invoke(draggedSlot.container, draggedSlot.slotIndex, container, slotIndex);
        }

        /// <summary>
        /// Reports a right-click so the manager can act (context menu in normal mode, quick transfer
        /// while a chest is open).
        /// </summary>
        public void OnPointerClick(PointerEventData eventData)
        {
            if (eventData.dragging) return;

            if (eventData.button == PointerEventData.InputButton.Right)
                onClicked?.Invoke(container, slotIndex, true);
        }

        /// <summary>
        /// Reports the hovered cell so the manager can show its description panel. Suppressed while a
        /// drag is in progress, where the panel would only get in the way.
        /// </summary>
        public void OnPointerEnter(PointerEventData eventData)
        {
            if (draggedSlot != null) return;
            onHoverEnter?.Invoke(container, slotIndex);
        }

        /// <summary>
        /// Reports that the pointer left the cell so the manager can hide the description panel.
        /// </summary>
        public void OnPointerExit(PointerEventData eventData)
        {
            onHoverExit?.Invoke();
        }

        #endregion
    }
}