using UnityEngine;
using UnityEngine.UI;
using TMPro;
using Ashwild.Player;
using Ashwild.UI;

namespace Ashwild.Inventory
{
    /// <summary>
    /// The inventory window. It is a local UI panel (opening/closing is purely local — the item
    /// data itself lives in the networked <see cref="PlayerInventory"/>), so it is driven by the
    /// GameUIManager panel stack like any other panel. The controller object stays active so it can
    /// build its grid when the local player spawns; Show/Hide only toggle the visual window.
    /// </summary>
    public class InventoryUI : UIPanel
    {
        /// <summary>
        /// Marks this panel as the inventory: input is locked and the cursor shows, but the world
        /// keeps running (unlike the pause menu).
        /// </summary>
        public override PanelKind Kind => PanelKind.Inventory;

        [Header("References")]
        [SerializeField] private GameObject inventoryPanel;
        [SerializeField] private Transform slotContainer;
        [SerializeField] private GameObject slotPrefab;

        [Header("Drag Ghost")]
        [SerializeField] private GameObject ghostObject;
        [SerializeField] private Image ghostIcon;
        [SerializeField] private TextMeshProUGUI ghostQuantityText;

        [Header("Context Menu")]
        [SerializeField] private SlotContextMenu contextMenu;

        [Header("Categories")]
        [SerializeField] private InventoryCategoryManager categoryManager;

        [Header("Hotbar")]
        [SerializeField] private HotbarUI hotbarUI;

        private SlotUI[] slotUIs;
        private PlayerInventory inventory;
        private bool bound;

        /// <summary>
        /// Waits for the networked local player to spawn before building the inventory grid.
        /// </summary>
        private void OnEnable()
        {
            PlayerEvents.LocalPlayerSpawned += HandleLocalPlayerSpawned;
        }

        /// <summary>
        /// Unsubscribes — mirrors OnEnable exactly.
        /// </summary>
        private void OnDisable()
        {
            PlayerEvents.LocalPlayerSpawned -= HandleLocalPlayerSpawned;
        }

        private void Start()
        {
            // Setup shared ghost for all SlotUIs (hotbar + inventory) — does not need the player.
            SlotUI.SetupGhost(ghostObject, ghostIcon, ghostQuantityText);
            inventoryPanel.SetActive(false);

            // The player may already exist (late UI init); otherwise we wait for the spawn event.
            if (PlayerInventory.Instance != null)
                BuildInventory();
        }

        /// <summary>
        /// Builds the grid as soon as the local player has spawned on the network.
        /// </summary>
        private void HandleLocalPlayerSpawned() => BuildInventory();

        /// <summary>
        /// Creates the non-hotbar slot UIs from the local player's inventory; runs once.
        /// </summary>
        private void BuildInventory()
        {
            if (bound) return;
            inventory = PlayerInventory.Instance;
            if (inventory == null) return;
            bound = true;

            // Only create slots for non-hotbar indices (hotbarSize to inventorySize-1)
            int nonHotbarCount = inventory.InventorySize - inventory.HotbarSize;
            slotUIs = new SlotUI[nonHotbarCount];
            for (int i = 0; i < nonHotbarCount; i++)
            {
                int slotIndex = inventory.HotbarSize + i;
                GameObject slotGO = Instantiate(slotPrefab, slotContainer);
                SlotUI slotUI = slotGO.GetComponent<SlotUI>();
                slotUI.Initialize(slotIndex, OnSwapRequested, OnSlotClicked);
                slotUIs[i] = slotUI;
            }

            inventory.onSlotChanged.AddListener(RefreshSlot);
            RefreshAll();
        }

        private void OnDestroy()
        {
            if (inventory != null)
                inventory.onSlotChanged.RemoveListener(RefreshSlot);
        }

        /// <summary>
        /// Opens the inventory window (called by the GameUIManager panel stack).
        /// </summary>
        public override void Show()
        {
            inventoryPanel.SetActive(true);
            RefreshAll();

            if (categoryManager != null)
                categoryManager.Open();

            if (hotbarUI != null)
                hotbarUI.OnInventoryOpen();
        }

        /// <summary>
        /// Closes the inventory window and tears down its transient UI (ghost, context menu).
        /// </summary>
        public override void Hide()
        {
            if (ghostObject != null)
                ghostObject.SetActive(false);

            if (contextMenu != null)
                contextMenu.Hide();

            if (categoryManager != null)
                categoryManager.Close();

            if (hotbarUI != null)
                hotbarUI.OnInventoryClose();

            inventoryPanel.SetActive(false);
        }

        /// <summary>
        /// Instant hide used when the manager initializes panels — just parks the window closed.
        /// </summary>
        public override void HideInstant()
        {
            if (ghostObject != null)
                ghostObject.SetActive(false);

            inventoryPanel.SetActive(false);
        }

        // Called by any SlotUI (inventory or hotbar) when a drag-drop completes
        public static void OnSwapRequested(int fromIndex, int toIndex)
        {
            PlayerInventory inv = PlayerInventory.Instance;
            InventorySlot fromSlot = inv.GetSlot(fromIndex);
            InventorySlot toSlot = inv.GetSlot(toIndex);

            // Same stackable item: merge
            if (!fromSlot.IsEmpty && !toSlot.IsEmpty
                && fromSlot.ItemData == toSlot.ItemData
                && toSlot.CanAccept(fromSlot.ItemData))
            {
                int leftover = toSlot.AddQuantity(fromSlot.Quantity);
                if (leftover <= 0)
                    fromSlot.Clear();
                else
                    fromSlot.Set(fromSlot.ItemData, leftover);

                inv.onSlotChanged?.Invoke(fromIndex);
                inv.onSlotChanged?.Invoke(toIndex);
            }
            else
            {
                // Swap
                inv.SwapSlots(fromIndex, toIndex);
            }
        }

        private void OnSlotClicked(int index, bool rightClick)
        {
            if (rightClick)
            {
                if (contextMenu != null)
                    contextMenu.Show(index);
                else
                    inventory.UseItem(index);
            }
        }

        private void RefreshSlot(int index)
        {
            if (slotUIs == null) return;

            int localIndex = index - inventory.HotbarSize;
            if (localIndex >= 0 && localIndex < slotUIs.Length)
                slotUIs[localIndex].UpdateVisual(inventory.GetSlot(index));
        }

        private void RefreshAll()
        {
            if (slotUIs == null) return;

            for (int i = 0; i < slotUIs.Length; i++)
            {
                int slotIndex = inventory.HotbarSize + i;
                slotUIs[i].UpdateVisual(inventory.GetSlot(slotIndex));
            }
        }
    }
}