using System;
using System.Numerics;
using AcDream.App.UI.Layout;

namespace AcDream.App.UI;

/// <summary>
/// Generic dat-widget button — the production replacement for any dat element of
/// Type 1 (UIElement_Button, registered via RegisterElementClass(1, UIElement_Button::Create)
/// @ acclient_2013_pseudo_c.txt:125828).
///
/// <para>
/// Draws per-state sprite media exactly like <see cref="UiDatElement"/> (same
/// <c>ActiveState</c> defaulting, same <c>ActiveMedia()</c> fallback chain, same tiled
/// <c>DrawSprite</c> call with UV-repeat so chrome edges tile correctly) plus an
/// optional centered text label. The click behavior mirrors <see cref="UiDatElement"/>
/// one-for-one so the chat Send and Max/Min buttons that previously bound through
/// <c>UiDatElement.OnClick</c> continue to work without behavioral change.
/// </para>
///
/// <para>
/// State selection: picks <see cref="ElementInfo.DefaultStateName"/> if set, then
/// "Normal" if the element has a Normal state sprite, then falls back to the unnamed
/// DirectState ("" key) — identical to <see cref="UiDatElement"/>.
/// </para>
///
/// <para>
/// Built by <see cref="DatWidgetFactory"/> for Type-1 elements (chat Send 0x10000019,
/// Max/Min 0x1000046F). NOT the same as <see cref="UiSimpleButton"/>, which is an
/// earlier dev-scaffold widget with no dat sprites.
/// </para>
/// </summary>
public sealed class UiButton : UiElement, IUiGlobalTimeListener, IUiDatStateful
{
    private readonly ElementInfo _info;
    private readonly ElementInfo _mediaInfo;
    private readonly FaceSegment[] _faceSegments;
    private readonly Func<uint, (uint tex, int w, int h)> _resolve;
    private readonly HashSet<uint> _availableStates = new();
    private bool _pressed;
    private bool _pointerOver;
    private bool _selected;
    private bool _hotClicking;
    private bool _suppressNextClick;
    private int _pointerX;
    private int _pointerY;
    private double _nextHotClickTime = double.NaN;

    /// <summary>Optional click handler. Wired by the controller (e.g. chat Submit, ToggleMaximize).</summary>
    public Action? OnClick { get; set; }

    /// <summary>
    /// Optional pointer transition handlers. These expose retail's distinct
    /// pressed/released element messages for controls such as the combat-height
    /// buttons, where mouse-down begins charging and mouse-up commits the attack.
    /// </summary>
    public Action? OnPressed { get; set; }
    public Action? OnReleased { get; set; }

    /// <summary>
    /// Optional position-aware click handler. Coordinates are local pixels in this button,
    /// matching retail's <c>UIElementMessageInfo.ptWindow</c> paperdoll hit-test input.
    /// </summary>
    public Action<int, int>? OnClickAt { get; set; }

    /// <summary>
    /// Optional item-drop target callbacks. Retail uses ordinary buttons as drop surfaces
    /// in a few panels (notably gmToolbarUI's inventory button), so this belongs on the
    /// retained button rather than in UiRoot or a panel-specific hit-test workaround.
    /// </summary>
    public Func<ItemDragPayload, ItemDragAcceptance>? OnItemDragOver { get; set; }
    public Action<ItemDragPayload>? OnItemDrop { get; set; }
    public uint ItemDragAcceptSprite { get; set; }
    public uint ItemDragRejectSprite { get; set; }
    private ItemDragAcceptance _itemDragAcceptance;

    internal ItemDragAcceptance ItemDragAcceptanceForTest => _itemDragAcceptance;

    /// <summary>The dat element id from <see cref="ElementInfo.Id"/>.</summary>
    public uint ElementId => _info.Id;

    /// <summary>Optional centered text label drawn over the sprite (e.g. "Send" on a blank gold frame).</summary>
    public string? Label { get; set; }

    /// <summary>Dat font for <see cref="Label"/>. Required for the label to draw.</summary>
    public UiDatFont? LabelFont { get; set; }

    /// <summary>Label color (default white).</summary>
    public Vector4 LabelColor { get; set; } = Vector4.One;

    /// <summary>Optional authored face rectangle. Full-button by default; retail
    /// UIOption_Checkbox uses its 13x13 indicator child as the button face.</summary>
    public float FaceLeft { get; set; }
    public float FaceTop { get; set; }
    public float FaceWidth { get; set; }
    public float FaceHeight { get; set; }

    /// <summary>Additional left inset for left-aligned labels.</summary>
    public float LabelOffsetX { get; set; } = 3f;

    /// <summary>Horizontal alignment of <see cref="Label"/>. Center (default) for normal buttons;
    /// Left for the paperdoll "Slots" caption that sits at the left edge, before the slots.</summary>
    public LabelAlignment LabelAlign { get; set; } = LabelAlignment.Center;

    /// <summary>Label horizontal alignment options.</summary>
    public enum LabelAlignment { Center, Left }

    public bool ToggleBehavior { get; }
    public bool RolloverEnabled { get; }
    public bool HotClickEnabled { get; }
    public float HotClickInitialDelay { get; }
    public float HotClickRepeatInterval { get; }

    public bool Selected
    {
        get => _selected;
        set
        {
            if (_selected == value) return;
            _selected = value;
            UpdateVisualState();
        }
    }

    /// <summary>
    /// Active state name, runtime-settable (e.g. Max/Min toggling Normal ↔ Minimized).
    /// Matches <see cref="UiDatElement.ActiveState"/>.
    /// </summary>
    public string ActiveState { get; set; } = "";

    public uint ActiveRetailStateId
    {
        get
        {
            if (string.IsNullOrEmpty(ActiveState))
                return UiStateInfo.DirectStateId;
            foreach (var (id, state) in _mediaInfo.States)
                if (string.Equals(state.Name, ActiveState, StringComparison.Ordinal))
                    return id;
            return UiButtonStateMachine.TryStateId(ActiveState, out uint standard)
                ? standard
                : RetailUiStateIds.TryStateId(ActiveState, out uint custom) ? custom : 0u;
        }
    }

    /// <summary>Reads a resolved enum-valued DAT attribute from this button.</summary>
    public bool TryGetEnumAttribute(uint propertyId, out uint value)
    {
        if (_info.TryGetEffectiveProperty(propertyId, out var property)
            && property.Kind == UiPropertyKind.Enum)
        {
            value = checked((uint)property.UnsignedValue);
            return true;
        }

        value = 0;
        return false;
    }

    public override string ActiveCursorStateName => ActiveState;

    public bool TrySetRetailState(uint stateId)
    {
        if (ToggleBehavior && stateId is UiButtonStateMachine.Normal or UiButtonStateMachine.Highlight)
        {
            Selected = stateId == UiButtonStateMachine.Highlight;
            return true;
        }
        if (stateId == UiButtonStateMachine.Ghosted)
        {
            Enabled = false;
            return true;
        }
        if (!Enabled && stateId != UiButtonStateMachine.Ghosted)
            Enabled = true;

        if (stateId == UiStateInfo.DirectStateId)
        {
            if (!TryFindState(stateId, out _) && !HasStateMedia(""))
                return false;
            ActiveState = "";
            return true;
        }
        if (TryFindState(stateId, out var state))
        {
            ActiveState = state.Name;
            return true;
        }
        string stateName = UiButtonStateMachine.StateName(stateId);
        if (string.IsNullOrEmpty(stateName))
            stateName = RetailUiStateIds.StateName(stateId);
        if (!string.IsNullOrEmpty(stateName) && HasStateMedia(stateName))
        {
            ActiveState = stateName;
            return true;
        }
        return false;
    }

    /// <param name="info">Merged <see cref="ElementInfo"/> for this element.</param>
    /// <param name="resolve">Dat file-id → (GL texture handle, native px width, native px height).
    /// Returns (0,0,0) when the texture is not yet uploaded.</param>
    public UiButton(
        ElementInfo info,
        Func<uint, (uint tex, int w, int h)> resolve,
        ElementInfo? mediaInfo = null,
        IReadOnlyList<ElementInfo>? faceSegments = null)
    {
        _info = info;
        _mediaInfo = mediaInfo ?? info;
        _faceSegments = faceSegments is null
            ? []
            : faceSegments.Select(static segment => new FaceSegment(segment)).ToArray();
        _resolve = resolve;
        ClickThrough = false;   // buttons are interactive — opt OUT of click-through

        // Visual transitions can select only states with an actual button face.
        // Retail layouts commonly declare an empty Normal_pressed descriptor while
        // supplying art only for Normal/Highlight. Treating that property-only state
        // as drawable briefly blanks the button during mouse-down.
        if (_faceSegments.Length == 0)
            AddAvailableStates(_mediaInfo);
        else
            foreach (FaceSegment segment in _faceSegments)
                AddAvailableStates(segment.Info);

        ToggleBehavior = info.TryGetEffectiveBool(0x0Bu, out bool toggle) && toggle;
        RolloverEnabled = info.TryGetEffectiveBool(0x13u, out bool rollover) && rollover;
        HotClickEnabled = info.TryGetEffectiveBool(0x0Fu, out bool hotClick) && hotClick;
        HotClickInitialDelay = info.TryGetEffectiveFloat(0x10u, out float initialDelay)
            ? initialDelay
            : 0f;
        HotClickRepeatInterval = info.TryGetEffectiveFloat(0x11u, out float repeatInterval)
            ? repeatInterval
            : 0f;
        _selected = info.TryGetEffectiveBool(0x0Eu, out bool selected) && selected;
        bool disabled = info.TryGetEffectiveBool(0x0Du, out bool ghosted) && ghosted;

        // State defaulting matches UiDatElement exactly:
        // DefaultStateName wins; else "Normal" if that state has a sprite; else DirectState ("").
        if (!string.IsNullOrEmpty(info.DefaultStateName))
            ActiveState = info.DefaultStateName;
        else if (HasStateMedia("Normal"))
            ActiveState = "Normal";
        // else ActiveState stays "" (DirectState)

        Enabled = !disabled;
        FaceWidth = mediaInfo?.Width ?? info.Width;
        FaceHeight = mediaInfo?.Height ?? info.Height;
        UpdateVisualState();
    }

    /// <summary>The button draws its own face + label; any dat label child is reproduced
    /// procedurally, so the importer must not build the button's children as widgets.</summary>
    public override bool ConsumesDatChildren => true;

    /// <summary>A button is interactive — it must receive its Click even inside a whole-window-Draggable
    /// frame (e.g. the paperdoll "Slots" toggle in the inventory window), so it opts out of the
    /// IA-12 whole-window-drag that would otherwise swallow the press.</summary>
    public override bool HandlesClick => true;

    /// <summary>
    /// Returns the File id for the current <see cref="ActiveState"/>, falling back to
    /// the DirectState ("" key) if the named state is absent.
    /// Returns 0 if neither exists.
    /// Mirrors <see cref="UiDatElement.ActiveMedia()"/>.
    /// </summary>
    private uint ActiveFile(ElementInfo mediaInfo)
        => mediaInfo.StateMedia.TryGetValue(ActiveState, out var m) ? m.File
         : mediaInfo.StateMedia.TryGetValue("", out var d) ? d.File : 0u;

    protected override void OnDraw(UiRenderContext ctx)
    {
        if (_faceSegments.Length != 0)
        {
            foreach (FaceSegment segment in _faceSegments)
                DrawFace(ctx, ActiveFile(segment.Info), segment.Rect(Width, Height));
        }
        else
        {
            uint file = ActiveFile(_mediaInfo);
            if (file != 0)
            {
                var (tex, tw, th) = _resolve(file);
                if (tex != 0 && tw != 0 && th != 0)
                {
                    // Tiled draw — same call shape as UiDatElement.OnDraw (UV-repeat; GL_REPEAT-wrapped
                    // UI texture). Matches ImgTex::TileCSI; no Stretch mode exists.
                    float faceWidth = FaceWidth > 0f ? FaceWidth : Width;
                    float faceHeight = FaceHeight > 0f ? FaceHeight : Height;
                    ctx.DrawSprite(tex, FaceLeft, FaceTop, faceWidth, faceHeight,
                        0, 0, faceWidth / tw, faceHeight / th, Vector4.One);
                }
            }
        }

        if (Label is { Length: > 0 } label && LabelFont is { } lf)
        {
            float tx = LabelAlign == LabelAlignment.Left
                ? LabelOffsetX
                : (Width - lf.MeasureWidth(label)) * 0.5f;            // centered (default)
            float ty = (Height - lf.LineHeight) * 0.5f;
            ctx.DrawStringDat(lf, label, tx, ty, LabelColor);
        }

        uint dragSprite = _itemDragAcceptance switch
        {
            ItemDragAcceptance.Accept => ItemDragAcceptSprite,
            ItemDragAcceptance.Reject => ItemDragRejectSprite,
            _ => 0u,
        };
        if (dragSprite != 0)
        {
            var (tex, _, _) = _resolve(dragSprite);
            if (tex != 0)
                ctx.DrawSprite(tex, 0f, 0f, Width, Height, 0f, 0f, 1f, 1f, Vector4.One);
        }
    }

    private void DrawFace(UiRenderContext ctx, uint file, UiPixelRect rect)
    {
        if (file == 0 || rect.Width <= 0 || rect.Height <= 0)
            return;
        var (texture, textureWidth, textureHeight) = _resolve(file);
        if (texture == 0 || textureWidth == 0 || textureHeight == 0)
            return;

        // Same tiled/cropped media path as UiDatElement. Segment geometry is
        // first reflowed by its own four-edge retail layout policy.
        ctx.DrawSprite(texture, rect.X0, rect.Y0, rect.Width, rect.Height,
            0f, 0f, (float)rect.Width / textureWidth, (float)rect.Height / textureHeight,
            Vector4.One);
    }

    private void AddAvailableStates(ElementInfo mediaInfo)
    {
        foreach (string stateName in mediaInfo.StateMedia.Keys)
            if (UiButtonStateMachine.TryStateId(stateName, out uint stateId))
                _availableStates.Add(stateId);
    }

    private bool HasStateMedia(string stateName)
    {
        if (_faceSegments.Length == 0)
            return _mediaInfo.StateMedia.ContainsKey(stateName);
        foreach (FaceSegment segment in _faceSegments)
            if (segment.Info.StateMedia.ContainsKey(stateName))
                return true;
        return false;
    }

    private bool TryFindState(uint stateId, out UiStateInfo state)
    {
        if (_faceSegments.Length == 0)
            return _mediaInfo.States.TryGetValue(stateId, out state!);
        foreach (FaceSegment segment in _faceSegments)
            if (segment.Info.States.TryGetValue(stateId, out state!))
                return true;
        state = null!;
        return false;
    }

    private sealed class FaceSegment
    {
        private readonly UiPixelRect _original;
        private readonly UiLayoutPolicy? _layout;

        public FaceSegment(ElementInfo info)
        {
            Info = info;
            _original = UiPixelRect.FromPositionAndSize(
                (int)info.X, (int)info.Y, (int)info.Width, (int)info.Height);
            if (info.HasOriginalParentSize)
                _layout = new UiLayoutPolicy(
                    info.Left, info.Top, info.Right, info.Bottom,
                    _original,
                    UiPixelRect.FromPositionAndSize(
                        0, 0, (int)info.OriginalParentWidth, (int)info.OriginalParentHeight));
        }

        public ElementInfo Info { get; }

        public UiPixelRect Rect(float parentWidth, float parentHeight)
        {
            if (_layout is null)
                return _original;
            return _layout.Apply(
                _original,
                UiPixelRect.FromPositionAndSize(0, 0, (int)parentWidth, (int)parentHeight));
        }
    }

    public override bool OnEvent(in UiEvent e)
    {
        switch (e.Type)
        {
            case UiEventType.HoverEnter:
                _pointerOver = true;
                UpdateVisualState();
                return true;
            case UiEventType.HoverLeave:
                _pointerOver = false;
                UpdateVisualState();
                return true;
            case UiEventType.MouseDown:
                _pointerX = e.Data1;
                _pointerY = e.Data2;
                _pointerOver = ContainsLocal(e.Data1, e.Data2);
                _pressed = true;
                UpdateVisualState();
                if (Enabled)
                    OnPressed?.Invoke();
                if (HotClickEnabled && Enabled)
                {
                    OnClick?.Invoke();
                    OnClickAt?.Invoke(_pointerX, _pointerY);
                    _hotClicking = true;
                    _nextHotClickTime = double.NaN;
                }
                return true;
            case UiEventType.MouseMove:
                if (_pressed)
                {
                    _pointerX = e.Data1;
                    _pointerY = e.Data2;
                    _pointerOver = ContainsLocal(e.Data1, e.Data2);
                    UpdateVisualState();
                    return true;
                }
                return false;
            case UiEventType.MouseUp:
                _pointerX = e.Data1;
                _pointerY = e.Data2;
                _pointerOver = ContainsLocal(e.Data1, e.Data2);
                _suppressNextClick = _hotClicking && _pointerOver;
                _hotClicking = false;
                _nextHotClickTime = double.NaN;
                if (_pressed && _pointerOver && Enabled && ToggleBehavior)
                    _selected = !_selected;
                if (_pressed && Enabled)
                    OnReleased?.Invoke();
                _pressed = false;
                UpdateVisualState();
                return true;
            case UiEventType.Click:
                if (!Enabled) return true;
                if (_suppressNextClick)
                {
                    _suppressNextClick = false;
                    return true;
                }
                OnClick?.Invoke();
                OnClickAt?.Invoke(e.Data1, e.Data2);
                return OnClick is not null || OnClickAt is not null;
            case UiEventType.DragEnter:
                _itemDragAcceptance = e.Payload is ItemDragPayload payload
                    ? OnItemDragOver?.Invoke(payload) ?? ItemDragAcceptance.None
                    : ItemDragAcceptance.None;
                return OnItemDragOver is not null;
            case UiEventType.DragOver:
                _itemDragAcceptance = ItemDragAcceptance.None;
                return OnItemDragOver is not null;
            case UiEventType.DropReleased:
                _itemDragAcceptance = ItemDragAcceptance.None;
                if (e.Payload is ItemDragPayload dropped)
                    OnItemDrop?.Invoke(dropped);
                return OnItemDrop is not null;
            default:
                return false;
        }
    }

    protected override void OnEnabledChanged()
    {
        if (!Enabled)
        {
            _pressed = false;
            _hotClicking = false;
            _nextHotClickTime = double.NaN;
        }
        UpdateVisualState();
    }

    internal int FaceSegmentCount => _faceSegments.Length;

    internal IReadOnlyList<UiPixelRect> FaceSegmentRectsForTest()
        => _faceSegments.Select(segment => segment.Rect(Width, Height)).ToArray();

    public void OnGlobalUiTime(double nowSeconds)
    {
        if (!_hotClicking || !HotClickEnabled)
            return;

        if (double.IsNaN(_nextHotClickTime))
            _nextHotClickTime = nowSeconds + HotClickInitialDelay;

        if (!_pointerOver && nowSeconds >= _nextHotClickTime)
        {
            _nextHotClickTime = nowSeconds;
            return;
        }

        if (_pointerOver && nowSeconds >= _nextHotClickTime)
        {
            OnClick?.Invoke();
            OnClickAt?.Invoke(_pointerX, _pointerY);
            _nextHotClickTime += HotClickRepeatInterval;
        }
    }

    private bool ContainsLocal(int x, int y)
        => x >= 0 && y >= 0 && x < Width && y < Height;

    private void UpdateVisualState()
    {
        uint requested = UiButtonStateMachine.RequestedState(new UiButtonVisualInput(
            Disabled: !Enabled,
            Selected: _selected,
            RolloverEnabled: RolloverEnabled,
            Pressed: _pressed,
            PointerOver: _pointerOver));
        if (_availableStates.Contains(requested))
            ActiveState = UiButtonStateMachine.StateName(requested);
    }
}