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

namespace Ashwild.Inventory
{
    /// <summary>
    /// The inventory window and the manager of its right-side modules. It is a local UI panel
    /// (opening/closing is purely local — the item data lives in the networked <see cref="PlayerInventory"/>),
    /// driven by the GameUIManager panel stack. The left grid + hotbar are always the player's inventory;
    /// the right area swaps between two modules: the hover description (normal browsing) and the chest
    /// module (<see cref="ChestPanelUI"/>) when a chest is opened. Opening a chest reuses this same window
    /// — the inventory and hotbar cells double as the deposit source, so nothing is rebuilt — and every
    /// drop is routed here into the right operation, chest transfers going through the chest's
    /// server-authoritative RPCs so two players sharing a chest stay in sync.
    /// </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). A chest reuses this same window/kind.
        /// </summary>
        public override PanelKind Kind => PanelKind.Inventory;

        /// <summary>
        /// The single inventory window in the scene, reached by a chest's Interact() and by slot cells
        /// routing their drops here.
        /// </summary>
        public static InventoryUI Instance { get; private set; }

        #region Serialized Fields

        [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("Right Modules")]
        [Tooltip("Holder of the hover-description module — shown while browsing, hidden while a chest is open.")]
        [SerializeField] private GameObject descriptionModule;
        [SerializeField] private HoverDescriptionUI hoverDescription;
        [Tooltip("The chest module shown in place of the description while a chest is open.")]
        [SerializeField] private ChestPanelUI chestPanel;

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

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

        #endregion

        #region State

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

        /// <summary>
        /// The chest bound while the window is in chest mode (null during normal inventory browsing).
        /// </summary>
        private Chest boundChest;

        #endregion

        #region Unity Lifecycle

        /// <summary>
        /// Registers the singleton (in addition to the base panel setup).
        /// </summary>
        protected override void Awake()
        {
            base.Awake();
            Instance = this;
        }

        /// <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 + chest) — 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>
        /// Clears the listener and the singleton on teardown.
        /// </summary>
        private void OnDestroy()
        {
            if (inventory != null)
                inventory.onSlotChanged.RemoveListener(RefreshSlot);
            if (Instance == this) Instance = null;
        }

        #endregion

        #region Build

        /// <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(SlotContainer.Inventory, slotIndex,
                    HandleSlotDrop, OnSlotClicked, OnSlotHoverEnter, OnSlotHoverExit);
                slotUIs[i] = slotUI;
            }

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

        #endregion

        #region Panel Lifecycle

        /// <summary>
        /// Binds a chest and opens this window in chest mode through the panel stack. Called from a
        /// chest's Interact(); the chest is picked up in Show().
        /// </summary>
        public void OpenChest(Chest chest)
        {
            if (chest == null) return;
            boundChest = chest;

            if (UIManager.Instance != null)
                UIManager.Instance.OpenPanel(this);
        }

        /// <summary>
        /// Opens the inventory window. Enters chest mode when a chest was bound (right side shows the
        /// chest module, category is forced to and locked on the inventory), otherwise normal browsing
        /// (right side shows the description). Always lands on the inventory category, never craft.
        /// </summary>
        public override void Show()
        {
            inventoryPanel.SetActive(true);
            bool chestMode = boundChest != null;

            if (categoryManager != null)
            {
                categoryManager.Open();
                categoryManager.SetLocked(chestMode);
            }

            if (chestMode)
            {
                if (descriptionModule != null) descriptionModule.SetActive(false);
                if (chestPanel != null) chestPanel.Bind(boundChest);
                PlayerEvents.RaiseChestOpenChanged(true);
            }
            else
            {
                if (chestPanel != null) chestPanel.Hide();
                if (descriptionModule != null) descriptionModule.SetActive(true);
            }

            RefreshAll();

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

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

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

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

            if (categoryManager != null)
            {
                categoryManager.SetLocked(false);
                categoryManager.Close();
            }

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

            CloseChestMode();

            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);

            CloseChestMode();

            inventoryPanel.SetActive(false);
        }

        /// <summary>
        /// Leaves chest mode: hides the chest module, releases the chest and puts the description module
        /// back. Shared by both close paths so they can never drift apart — HideInstant used to forget
        /// the description and left the right side blank on the next open.
        /// </summary>
        private void CloseChestMode()
        {
            if (boundChest == null) return;

            if (chestPanel != null) chestPanel.Hide();
            boundChest = null;
            if (descriptionModule != null) descriptionModule.SetActive(true);
            PlayerEvents.RaiseChestOpenChanged(false);
        }

        #endregion

        #region Transfer Routing

        /// <summary>
        /// Routes a slot drop to whoever owns the slots: the inventory itself when both ends are local,
        /// otherwise the chest (which reconciles it server-side). Both paths end up in the same
        /// <see cref="SlotTransfer.Move"/> rules, so a chest drag behaves exactly like an inventory drag.
        /// Static so every cell (inventory, hotbar, chest) reports here without a per-cell reference.
        /// </summary>
        public static void HandleSlotDrop(SlotContainer fromContainer, int fromIndex, SlotContainer toContainer, int toIndex)
        {
            if (fromContainer == SlotContainer.Inventory && toContainer == SlotContainer.Inventory)
            {
                PlayerInventory inv = PlayerInventory.Instance;
                if (inv != null) inv.MoveSlot(fromIndex, toIndex);
                return;
            }

            Chest chest = Instance != null ? Instance.boundChest : null;
            if (chest == null) return;

            // Paint the chest cell as emptied now: its clear replicates on the SyncList (end of tick)
            // while the grant is an immediate TargetRpc, so without this the stack visibly lands in the
            // inventory before it leaves the chest.
            if (fromContainer == SlotContainer.Chest && Instance.chestPanel != null)
                Instance.chestPanel.PredictEmptied(fromIndex);

            chest.RequestMove(fromContainer, fromIndex, toContainer, toIndex);
        }

        /// <summary>
        /// Quick-transfers a stack to the other container (auto-placed), for right-clicks. Exposed so the
        /// hotbar — which cannot reach the private chest binding — can route its own cells here.
        /// </summary>
        public void RequestQuickTransfer(SlotContainer container, int index)
        {
            if (boundChest != null)
                boundChest.RequestQuickTransfer(container, index);
        }

        #endregion

        #region Event Handlers

        /// <summary>
        /// Right-click on an inventory cell: a quick deposit while a chest is open, otherwise the slot
        /// context menu.
        /// </summary>
        private void OnSlotClicked(SlotContainer container, int index, bool rightClick)
        {
            if (!rightClick) return;

            if (boundChest != null)
            {
                boundChest.RequestQuickTransfer(SlotContainer.Inventory, index);
                return;
            }

            if (contextMenu != null)
                contextMenu.Show(index);
            else if (inventory != null)
                inventory.UseItem(index);
        }

        /// <summary>
        /// Builds the description payload for the hovered slot and shows the side panel. Suppressed in
        /// chest mode (the description module is hidden) and for empty slots. The duration bar reflects
        /// the item's remaining uses/durability.
        /// </summary>
        private void OnSlotHoverEnter(SlotContainer container, int index)
        {
            if (boundChest != null) return;
            if (hoverDescription == null || inventory == null) return;

            InventorySlot slot = inventory.GetSlot(index);
            if (slot == null || slot.IsEmpty)
            {
                hoverDescription.Hide();
                return;
            }

            hoverDescription.Show(ItemDescriptionView.From(slot));
        }

        /// <summary>
        /// Hides the description panel when the pointer leaves a slot.
        /// </summary>
        private void OnSlotHoverExit()
        {
            if (hoverDescription != null)
                hoverDescription.Hide();
        }

        #endregion

        #region Refresh

        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));
            }
        }

        #endregion
    }
}