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
{
    private readonly ElementInfo _info;
    private readonly Func<uint, (uint tex, int w, int h)> _resolve;

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

    /// <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>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 }

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

    /// <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)
    {
        _info    = info;
        _resolve = resolve;
        ClickThrough = false;   // buttons are interactive — opt OUT of click-through

        // 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 (info.StateMedia.ContainsKey("Normal"))
            ActiveState = "Normal";
        // else ActiveState stays "" (DirectState)
    }

    /// <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()
        => _info.StateMedia.TryGetValue(ActiveState, out var m) ? m.File
         : _info.StateMedia.TryGetValue("", out var d) ? d.File : 0u;

    protected override void OnDraw(UiRenderContext ctx)
    {
        uint file = ActiveFile();
        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.
                ctx.DrawSprite(tex, 0, 0, Width, Height, 0, 0, Width / tw, Height / th, Vector4.One);
            }
        }

        if (Label is { Length: > 0 } label && LabelFont is { } lf)
        {
            float tx = LabelAlign == LabelAlignment.Left
                ? 3f                                                  // small left pad (room for a future checkbox box)
                : (Width - lf.MeasureWidth(label)) * 0.5f;            // centered (default)
            float ty = (Height - lf.LineHeight) * 0.5f;
            ctx.DrawStringDat(lf, label, tx, ty, LabelColor);
        }
    }

    public override bool OnEvent(in UiEvent e)
    {
        if (e.Type == UiEventType.Click && OnClick is not null) { OnClick(); return true; }
        return false;
    }
}