using System;
using System.Numerics;
using AcDream.App.UI;
using AcDream.Core.Items;

namespace AcDream.App.UI.Layout;

/// <summary>
/// Binds the imported gmInventoryUI tree (LayoutDesc 0x21000023) and populates it from
/// <see cref="ClientObjectTable"/>. The acdream analogue of retail
/// gmInventoryUI/gmBackpackUI/gm3DItemsUI ::PostInit (named-retail decomp 176236/176596/176728).
/// Container-switching is live (click a side bag → Use 0x0036 → ViewContents 0x0196 full-replace);
/// drag-into-bag / wield-drop wire are later sub-phases.
/// </summary>
public sealed class InventoryController : IItemListDragHandler
{
    // Element ids — spec §1 (dat dump of 0x21000022 / 0x21000021 + the *::PostInit binds).
    public const uint ContentsGridId    = 0x100001C6u;  // gm3DItemsUI m_itemList ("Contents of Backpack")
    public const uint ContainerListId   = 0x100001CAu;  // gmBackpackUI m_containerList (side-bag selector)
    public const uint TopContainerId    = 0x100001C9u;  // gmBackpackUI m_topContainer (main-pack cell)
    public const uint BurdenMeterId     = 0x100001D9u;  // gmBackpackUI m_burdenMeter (vertical)
    public const uint BurdenTextId      = 0x100001D8u;  // gmBackpackUI m_burdenText ("%d%%")
    public const uint BurdenCaptionId   = 0x100001D7u;  // "Burden"
    public const uint ContentsCaptionId = 0x100001C5u;  // "Contents of Backpack"
    public const uint ContentsScrollbarId = 0x100001C7u; // gm3DItemsUI gutter scrollbar (right of the grid)

    // Scrollbar chrome from base layout 0x2100003E (shared with the chat scrollbar; see
    // ChatWindowController). Both inventory + chat scrollbars inherit this base.
    private const uint ScrollTrackSprite  = 0x06004C5Fu;
    private const uint ScrollThumbSprite  = 0x06004C63u;  // 3-slice middle tile
    private const uint ScrollThumbTop     = 0x06004C60u;  // 3-slice top cap
    private const uint ScrollThumbBot     = 0x06004C66u;  // 3-slice bottom cap
    private const uint ScrollUpSprite     = 0x06004C6Cu;  // up arrow (top button)
    private const uint ScrollDownSprite   = 0x06004C69u;  // down arrow (bottom button)

    // 3D-items grid: 192x96 → 6 cols x 3 rows of the 32x32 UIItem cell (template 0x21000037).
    private const int   ContentsColumns = 6;
    private const float ContentsCellPx = 32f;   // gm3DItemsUI grid (192x96 = 6x3 of 32px)
    private const float BackpackCellPx = 36f;   // gmBackpackUI column cells (0x100001C9/CA = 36px)
    private const int   SideBagSlots   = 7;     // 0x100001CA is 36x252 = 7 slots
    private const int   MainPackSlots  = 102;   // retail main-pack capacity (Wiki: "up to 102 items")
    private const int   SidePackSlots = 24;     // standard side-pack capacity (reference_retail_inventory_paperdoll)

    private readonly ClientObjectTable _objects;
    private readonly Func<uint> _playerGuid;
    private readonly Func<ItemType, uint, uint, uint, uint, uint> _iconIds;
    private readonly Func<int?> _strength;

    private readonly UiItemList? _contentsGrid;
    private readonly UiItemList? _containerList;
    private readonly UiItemList? _topContainer;
    private readonly UiMeter?    _burdenMeter;

    private float _burdenFill;
    private int   _burdenPercent;
    private static readonly Vector4 CaptionColor = new(1f, 1f, 1f, 1f);

    private uint _openContainer;   // 0 = the main pack (the player); else the open side bag's guid
    private uint _selectedItem;    // 0 = none; the panel-wide selected item (green square)
    private readonly Action<uint>? _sendUse;
    private readonly Action<uint>? _sendNoLongerViewing;
    private readonly Action<uint, uint, int>? _sendPutItemInContainer;   // (item, container, placement)

    // ACE PropertyInt ids read by retail InqLoad (decomp 0x0058f130: InqInt(5)/InqInt(0xe6)).
    private const uint EncumbranceValProperty = 5u;    // total carried burden
    private const uint EncumbranceAugProperty = 0xE6u; // carry-capacity augmentation

    private InventoryController(
        ImportedLayout layout,
        ClientObjectTable objects,
        Func<uint> playerGuid,
        Func<ItemType, uint, uint, uint, uint, uint> iconIds,
        Func<int?> strength,
        UiDatFont? datFont,
        uint contentsEmptySprite,
        uint sideBagEmptySprite,
        uint mainPackEmptySprite,
        Action<uint>? sendUse,
        Action<uint>? sendNoLongerViewing,
        Action<uint, uint, int>? sendPutItemInContainer)
    {
        _objects    = objects;
        _playerGuid = playerGuid;
        _iconIds    = iconIds;
        _strength   = strength;
        _sendUse            = sendUse;
        _sendNoLongerViewing = sendNoLongerViewing;
        _sendPutItemInContainer = sendPutItemInContainer;

        _contentsGrid  = layout.FindElement(ContentsGridId)  as UiItemList;
        _containerList = layout.FindElement(ContainerListId) as UiItemList;
        _topContainer  = layout.FindElement(TopContainerId)  as UiItemList;

        if (_contentsGrid is not null)
        {
            _contentsGrid.Columns    = ContentsColumns;
            _contentsGrid.CellWidth  = ContentsCellPx;
            _contentsGrid.CellHeight = ContentsCellPx;
        }

        // Bind the gutter scrollbar to the contents grid's scroll model (the factory built
        // 0x100001C7 as a bare Type-11 UiScrollbar; wire it like ChatWindowController does).
        if (_contentsGrid is not null
            && layout.FindElement(ContentsScrollbarId) is UiScrollbar bar)
        {
            bar.Model          = _contentsGrid.Scroll;
            bar.SpriteResolve  = _contentsGrid.SpriteResolve;   // chrome resolve from the factory ctor
            bar.TrackSprite    = ScrollTrackSprite;
            bar.ThumbSprite    = ScrollThumbSprite;
            bar.ThumbTopSprite = ScrollThumbTop;
            bar.ThumbBotSprite = ScrollThumbBot;
            bar.UpSprite       = ScrollUpSprite;
            bar.DownSprite     = ScrollDownSprite;
        }
        if (_containerList is not null)
        {
            _containerList.Columns    = 1;
            _containerList.CellWidth  = BackpackCellPx;
            _containerList.CellHeight = BackpackCellPx;
        }

        // Per-list empty-slot art, resolved from the dat cell template (retail attr 0x1000000e
        // -> catalog 0x21000037 prototype's ItemSlot_Empty). 0 = leave the UiItemSlot default.
        if (_contentsGrid  is not null) _contentsGrid.CellEmptySprite  = contentsEmptySprite;
        if (_containerList is not null) _containerList.CellEmptySprite = sideBagEmptySprite;
        if (_topContainer  is not null) _topContainer.CellEmptySprite  = mainPackEmptySprite;

        // B-Drag: register this controller as the drag handler on all three lists.
        _contentsGrid?.RegisterDragHandler(this);
        _containerList?.RegisterDragHandler(this);
        _topContainer?.RegisterDragHandler(this);

        // Burden meter: vertical 11×58 bar (gmBackpackUI m_burdenMeter, retail direction 4).
        _burdenMeter = layout.FindElement(BurdenMeterId) as UiMeter;
        if (_burdenMeter is not null)
        {
            _burdenMeter.Vertical = true;            // 11x58 vertical bar
            _burdenMeter.FillFromBottom = true;      // retail direction 4 (visual-confirmed)
            _burdenMeter.Fill = () => _burdenFill;
        }

        // Captions: drive each host UiText directly with the known string (the caption
        // elements resolve to UiText). "Contents of Backpack" + "%d%%" are procedural in retail
        // (gm3DItemsUI/gmBackpackUI PostInit/SetLoadLevel); "Burden" is the dat label. (Spec §5.)
        AttachCaption(layout.FindElement(BurdenCaptionId),   () => "Burden", datFont);
        AttachCaption(layout.FindElement(ContentsCaptionId), () => "Contents of " + OpenContainerName(), datFont);
        AttachCaption(layout.FindElement(BurdenTextId),      () => _burdenPercent + "%", datFont);

        // Rebuild on any change to the player's possessions.
        _objects.ObjectAdded   += OnObjectChanged;
        _objects.ObjectMoved   += OnObjectMoved;
        _objects.ObjectRemoved += OnObjectChanged;
        _objects.ObjectUpdated += OnObjectChanged;

        Populate();
    }

    public static InventoryController Bind(
        ImportedLayout layout,
        ClientObjectTable objects,
        Func<uint> playerGuid,
        Func<ItemType, uint, uint, uint, uint, uint> iconIds,
        Func<int?> strength,
        UiDatFont? datFont,
        uint contentsEmptySprite = 0u,
        uint sideBagEmptySprite  = 0u,
        uint mainPackEmptySprite = 0u,
        Action<uint>? sendUse = null,
        Action<uint>? sendNoLongerViewing = null,
        Action<uint, uint, int>? sendPutItemInContainer = null)
        => new InventoryController(layout, objects, playerGuid, iconIds, strength, datFont,
                                   contentsEmptySprite, sideBagEmptySprite, mainPackEmptySprite,
                                   sendUse, sendNoLongerViewing, sendPutItemInContainer);

    private void OnObjectChanged(ClientObject o)        { if (Concerns(o)) Populate(); }
    private void OnObjectMoved(ClientObject o, uint from, uint to)
        { if (Concerns(o) || from == _playerGuid() || to == _playerGuid()) Populate(); }

    /// <summary>True if the object is in (or wielded by) the player — i.e. a rebuild is warranted.</summary>
    private bool Concerns(ClientObject o)
    {
        uint p = _playerGuid();
        return o.ObjectId == p                          // the player object IS the burden source
            || o.ContainerId == p || o.WielderId == p
            || o.ContainerId == EffectiveOpen()         // the OPEN container's contents drive the grid
            || (o.ContainerId != 0 && _objects.Get(o.ContainerId)?.ContainerId == p);  // 2-deep
    }

    public void Populate()
    {
        uint p = _playerGuid();
        uint open = EffectiveOpen();

        _contentsGrid?.Flush();
        _containerList?.Flush();

        // Side-bag column: ALWAYS the player's bags (constant across container switches; only the
        // open/selected indicators move). Equipped items never appear here.
        foreach (var guid in _objects.GetContents(p))
        {
            var item = _objects.Get(guid);
            if (item is null || item.CurrentlyEquippedLocation != EquipMask.None) continue;
            bool isBag = item.Type.HasFlag(ItemType.Container) || item.ItemsCapacity > 0;
            if (isBag) AddCell(_containerList, guid, isContainer: true);
        }

        // Contents grid: the OPEN container's loose items. (Bags live in the column; a side bag has
        // no sub-bags, so the isBag skip is a no-op when a bag is open.)
        foreach (var guid in _objects.GetContents(open))
        {
            var item = _objects.Get(guid);
            if (item is null || item.CurrentlyEquippedLocation != EquipMask.None) continue;
            bool isBag = item.Type.HasFlag(ItemType.Container) || item.ItemsCapacity > 0;
            if (!isBag) AddCell(_contentsGrid, guid, isContainer: false);
        }

        // Pad the grid to the OPEN container's capacity (main pack 102 / side bag 24).
        if (_contentsGrid is not null)
        {
            int cap = _objects.Get(open)?.ItemsCapacity ?? 0;
            int slots = cap > 0 ? cap : (open == p ? MainPackSlots : SidePackSlots);
            while (_contentsGrid.GetNumUIItems() < slots) AddEmptyCell(_contentsGrid);
        }

        // Pad the side-bag column to capacity, clamped to the 7-slot column (AP-52).
        if (_containerList is not null)
        {
            int capacity = _objects.Get(p)?.ContainersCapacity ?? 0;
            int bags = _containerList.GetNumUIItems();
            int slots = capacity > 0 ? capacity : SideBagSlots;
            slots = Math.Max(slots, bags);
            slots = Math.Min(slots, SideBagSlots);
            while (_containerList.GetNumUIItems() < slots) AddEmptyCell(_containerList);
        }

        // Main-pack cell: the player's own container — clicking it opens/selects the main pack.
        // Retail draws a CONSTANT backpack icon here, NOT the player's body icon: IconData::RenderIcons
        // (0x0058d1ee) has an IsThePlayer() branch that draws a fixed backpack with m_itemType =
        // TYPE_CONTAINER. Compose that backpack base over the Container type-underlay (the player
        // object's own IconId is the character body, which would render wrong here). The backpack
        // RenderSurface is 0x0600127E, VISUALLY CONFIRMED at the live gate 2026-06-22 (the earlier
        // 0x060011F4 from a research dat-dump of GetDIDByEnum(0x10000004,7) was a green tile, not the
        // pack — the index value was misreported). Retires AP-51.
        if (_topContainer is not null)
        {
            const uint PlayerPackBaseIcon = 0x0600127Eu;   // constant main-pack backpack (visual gate)
            _topContainer.Flush();
            var main = new UiItemSlot { SpriteResolve = _topContainer.SpriteResolve };
            main.SetItem(p, _iconIds(ItemType.Container, PlayerPackBaseIcon, 0u, 0u, 0u));
            main.DragAcceptSprite = 0x060011F7u; main.DragRejectSprite = 0x060011F8u;
            main.Clicked = () => OpenContainer(p);
            SetCapacityBar(main, p);               // main-pack fullness (items / ItemsCapacity)
            _topContainer.AddItem(main);
        }

        ApplyIndicators();
        RefreshBurden();
    }

    /// <summary>The effective open container — the explicit one, or the player (main pack) by default.
    /// Resolved live (not cached at ctor) so a late-arriving player guid is handled. The default
    /// sentinel is 0; once the main pack is explicitly opened, <c>_openContainer</c> holds the player
    /// guid instead — both resolve here to the same main-pack container, so the paths are equivalent.</summary>
    private uint EffectiveOpen() => _openContainer != 0 ? _openContainer : _playerGuid();

    /// <summary>Add a populated cell wired to its click role: container cell → open+select,
    /// item cell → select-only.</summary>
    private void AddCell(UiItemList? list, uint guid, bool isContainer)
    {
        if (list is null) return;
        var item = _objects.Get(guid);
        uint tex = item is null ? 0u
            : _iconIds(item.Type, item.IconId, item.IconUnderlayId, item.IconOverlayId, item.Effects);
        var cell = new UiItemSlot { SpriteResolve = list.SpriteResolve };
        cell.SetItem(guid, tex);
        cell.SlotIndex = list.GetNumUIItems();                 // index it will occupy (== its slot in a packed list)
        cell.DragAcceptSprite = 0x060011F7u;                   // green insert arrow (export-confirmed)
        cell.DragRejectSprite = 0x060011F8u;                   // red circle
        if (isContainer) { cell.Clicked = () => OpenContainer(guid); SetCapacityBar(cell, guid); }
        else             cell.Clicked = () => SelectItem(guid);
        list.AddItem(cell);
    }

    private static void AddEmptyCell(UiItemList list)
    {
        var cell = new UiItemSlot { SpriteResolve = list.SpriteResolve, SlotIndex = list.GetNumUIItems() };
        cell.DragAcceptSprite = 0x060011F7u;
        cell.DragRejectSprite = 0x060011F8u;
        list.AddItem(cell);
    }

    /// <summary>Set the per-cell container capacity bar — retail UIElement_UIItem::UpdateCapacityDisplay
    /// (0x004e16e0): visible only for a container with itemsCapacity &gt; 0; fill =
    /// GetNumContainedItems / itemsCapacity, clamped [0,1]. -1 hides the bar (non-container / unknown
    /// capacity). For a CLOSED side bag the contents aren't indexed until it's opened (ViewContents),
    /// so the bar reads empty until then — faithful to retail's known-children count.</summary>
    private void SetCapacityBar(UiItemSlot cell, uint containerGuid)
    {
        int cap = _objects.Get(containerGuid)?.ItemsCapacity ?? 0;
        if (cap <= 0) { cell.CapacityFill = -1f; return; }
        int n = _objects.GetContents(containerGuid).Count;
        cell.CapacityFill = Math.Clamp(n / (float)cap, 0f, 1f);
    }

    // ── IItemListDragHandler (B-Drag) — drop an item to move it (optimistic + wire) ──────────────
    /// <summary>Inventory items do NOT lift-remove (unlike the toolbar): the item stays in its slot
    /// until the server confirms the move. Retail dims the source; we leave it + the floating ghost.</summary>
    public void OnDragLift(UiItemList sourceList, UiItemSlot sourceCell, ItemDragPayload payload) { }

    /// <summary>Advisory accept/reject overlay (green insert-arrow / red circle). Grid drops are always
    /// valid (reorder/insert); a side-bag/main-pack drop is valid unless that container is KNOWN-full.</summary>
    public bool OnDragOver(UiItemList targetList, UiItemSlot targetCell, ItemDragPayload payload)
    {
        if (payload.ObjId == 0) return false;
        if (targetList == _contentsGrid) return true;
        if (targetList == _containerList || targetList == _topContainer)
        {
            if (targetCell.ItemId == 0 || targetCell.ItemId == payload.ObjId) return false;
            return !IsContainerFull(targetCell.ItemId);
        }
        return false;
    }

    /// <summary>Perform the move: resolve (container, placement) from the target, optimistically move
    /// locally (instant), and send PutItemInContainer. Retail: HandleDropRelease + ItemList_InsertItem.</summary>
    public void HandleDropRelease(UiItemList targetList, UiItemSlot targetCell, ItemDragPayload payload)
    {
        uint item = payload.ObjId;
        if (item == 0) return;

        uint container; int placement;
        if (targetList == _contentsGrid)
        {
            container = EffectiveOpen();
            placement = targetCell.ItemId != 0
                ? targetCell.SlotIndex                                                        // insert-before = the target's GRID INDEX (gapless), not its raw ContainerSlot
                : _objects.GetContents(container).Count;                                      // first empty = append
        }
        else if (targetList == _containerList || targetList == _topContainer)
        {
            if (targetCell.ItemId == 0 || targetCell.ItemId == item) return;
            container = targetCell.ItemId;                                                     // the bag / main pack
            if (IsContainerFull(container)) return;                                            // red already shown
            placement = _objects.GetContents(container).Count;                                 // append into it
        }
        else return;

        if (container == item) return;                                                         // never into itself
        _objects.MoveItemOptimistic(item, container, placement);                               // instant local move
        _sendPutItemInContainer?.Invoke(item, container, placement);
    }

    /// <summary>True only when we KNOW the container is full (capacity known + contents indexed). A
    /// closed bag (unknown count) returns false → advisory accept; the server is authoritative.</summary>
    private bool IsContainerFull(uint container)
    {
        int cap = _objects.Get(container)?.ItemsCapacity ?? 0;
        if (cap <= 0) return false;
        return _objects.GetContents(container).Count >= cap;
    }

    /// <summary>Select an item (panel-wide green square) without changing the open container or
    /// touching the wire. Retail: UIElement_ItemList::ItemList_SetSelectedItem (0x004e2fe0).</summary>
    private void SelectItem(uint guid)
    {
        if (guid == 0) return;
        _selectedItem = guid;
        ApplyIndicators();
    }

    /// <summary>Open a container (side bag or main pack): it becomes both the selected item and the
    /// open container. Sends Use to open a side bag server-side (ViewContents arrives async), and
    /// NoLongerViewingContents when switching away from a previously-open side bag. Retail:
    /// gmBackpackUI container-selection + CM_Physics::Event_Use.</summary>
    private void OpenContainer(uint guid)
    {
        if (guid == 0) return;
        _selectedItem = guid;                       // the container cell is also the selected item
        uint open = EffectiveOpen();
        if (guid == open) { ApplyIndicators(); return; }   // already open — just move the square

        uint p = _playerGuid();
        if (open != p && open != 0)
            _sendNoLongerViewing?.Invoke(open);     // close the previously-open side bag
        _openContainer = guid;
        if (guid != p)
            _sendUse?.Invoke(guid);                 // open the side bag (ViewContents will land)
        Populate();                                  // repaint the grid for the new open container
    }

    /// <summary>Stamp the open-container triangle + selected-item square onto every cell per the
    /// retail keying (item.itemID == openContainerId / selectedItemId).</summary>
    private void ApplyIndicators()
    {
        SetIndicators(_contentsGrid);
        SetIndicators(_containerList);
        SetIndicators(_topContainer);
    }

    private void SetIndicators(UiItemList? list)
    {
        if (list is null) return;
        uint open = EffectiveOpen();
        for (int i = 0; i < list.GetNumUIItems(); i++)
        {
            var cell = list.GetItem(i);
            if (cell is null) continue;
            cell.Selected        = cell.ItemId != 0 && cell.ItemId == _selectedItem;
            cell.IsOpenContainer = cell.ItemId != 0 && cell.ItemId == open;
        }
    }

    /// <summary>The open container's display name for the contents caption.</summary>
    private string OpenContainerName()
    {
        uint open = EffectiveOpen();
        return open == _playerGuid() ? "Backpack" : (_objects.Get(open)?.Name ?? "Backpack");
    }

    private void AttachCaption(UiElement? host, Func<string> text, UiDatFont? datFont)
    {
        if (host is null) return;

        // The caption elements (0x100001D7 "Burden", 0x100001C5 "Contents of Backpack",
        // 0x100001D8 "%") resolve to UiText (Type-0 inheriting a text base — confirmed live).
        // Drive the host UiText DIRECTLY: it is already in the paint tree and renders, whereas
        // a nested child UiText did not paint. Set it to a static centered single-line label.
        if (host is UiText t)
        {
            t.Centered = true;
            t.DatFont = datFont;
            t.ClickThrough = true;
            t.AcceptsFocus = false;
            t.IsEditControl = false;
            t.CapturesPointerDrag = false;
            t.LinesProvider = () =>
            {
                var s = text();
                return string.IsNullOrEmpty(s)
                    ? Array.Empty<UiText.Line>()
                    : new[] { new UiText.Line(s, CaptionColor) };
            };
            return;
        }

        // Fallback (non-UiText host): attach a centered label child.
        var label = new UiText
        {
            Left = 0f, Top = 0f, Width = host.Width, Height = host.Height,
            Anchors = AnchorEdges.Left | AnchorEdges.Top | AnchorEdges.Right,
            Centered = true, DatFont = datFont, ClickThrough = true,
            AcceptsFocus = false, IsEditControl = false, CapturesPointerDrag = false,
            LinesProvider = () =>
            {
                var s = text();
                return string.IsNullOrEmpty(s)
                    ? Array.Empty<UiText.Line>()
                    : new[] { new UiText.Line(s, CaptionColor) };
            },
        };
        host.AddChild(label);
    }

    /// <summary>Recompute the burden fill + percent. Port of CACQualities::InqLoad
    /// (decomp 0x0058f130) → gmBackpackUI::SetLoadLevel (0x004a6ea0). currentBurden:
    /// player wire EncumbranceVal (PropertyInt 5) if present, else the carried-Burden sum.</summary>
    private void RefreshBurden()
    {
        uint p = _playerGuid();
        int str = _strength() ?? 10;                       // InqAttribute default 0xa
        int aug = _objects.Get(p)?.Properties.GetInt(EncumbranceAugProperty) ?? 0;
        int capacity = BurdenMath.EncumbranceCapacity(str, aug);

        int? wire = _objects.Get(p)?.Properties.Ints.TryGetValue(EncumbranceValProperty, out var ev) == true
            ? ev : (int?)null;
        int burden = wire ?? _objects.SumCarriedBurden(p);

        float load = BurdenMath.LoadRatio(capacity, burden);
        _burdenFill    = BurdenMath.LoadToFill(load);
        _burdenPercent = BurdenMath.LoadToPercent(load);
    }

    /// <summary>Detach event handlers (idempotent).</summary>
    public void Dispose()
    {
        _objects.ObjectAdded   -= OnObjectChanged;
        _objects.ObjectMoved   -= OnObjectMoved;
        _objects.ObjectRemoved -= OnObjectChanged;
        _objects.ObjectUpdated -= OnObjectChanged;
    }
}