using System;
using System.Collections.Generic;
using System.Numerics;

namespace AcDream.App.UI;

/// <summary>
/// Generic dropdown menu. Ports retail <c>UIElement_Menu</c>
/// (<c>RegisterElementClass(6) @ acclient_2013_pseudo_c.txt:120163</c>) +
/// <c>UIElement_Menu::MakePopup @0x46d310</c>: the button is labelled with
/// the active target; clicking opens a column-major popup on the dat-driven menu
/// chrome (panel + per-row + selected-row sprites). Items and all chat-channel
/// knowledge are populated by the controller, not baked into this widget. Built
/// by <see cref="AcDream.App.UI.Layout.DatWidgetFactory"/> for Type-6 elements.
/// </summary>
public sealed class UiMenu : UiElement
{
    /// <summary>One menu row: its label + an opaque payload the controller maps back.</summary>
    public readonly record struct MenuItem(string Label, object? Payload);

    /// <summary>The rows, populated by the controller. Laid out column-major:
    /// rows 0..RowsPerColumn-1 in column 0, then the next group in column 1, etc.</summary>
    public IReadOnlyList<MenuItem> Items { get; set; } = System.Array.Empty<MenuItem>();

    /// <summary>The currently-selected payload (drives the highlighted row).</summary>
    public object? Selected { get; set; }

    /// <summary>Fired with the picked item's payload when a row is chosen.</summary>
    public Action<object?>? OnSelect { get; set; }

    /// <summary>Per-payload enabled gate (disabled rows render greyed + are inert). Null ⇒ all enabled.</summary>
    public Func<object?, bool>? EnabledProvider { get; set; }

    /// <summary>Button-face caption (the active target). Null ⇒ blank face.</summary>
    public Func<string>? ButtonLabelProvider { get; set; }

    public int   RowsPerColumn { get; set; } = 7;     // items per column (dat item template)
    public float RowHeight     { get; set; } = 17f;   // dat item template 0x1000001E H=17
    public float ColumnWidth   { get; set; } = 191f;  // dat item template W=191

    private const int Border = RetailChromeSprites.Border; // 8-piece bevel thickness (5px)
    // The row sprites 0x0600124E/4D bake a checkbox/checkmark into the leftmost ~17px
    // square; the label starts just past it (box width + small gap) so text aligns with
    // the box instead of overlapping it.
    private const float TextIndent = 19f;
    // The button face sprite (0x06004D65/66) bakes a status LED (red→green) into its
    // left socket (~x4–20 of the 46px button); the caption starts past it so it doesn't
    // render over the LED.
    private const float ButtonTextIndent = 20f;

    public UiDatFont? DatFont { get; set; }
    public AcDream.App.Rendering.BitmapFont? Font { get; set; }
    public Func<uint, (uint tex, int w, int h)>? SpriteResolve { get; set; }

    // Button face sprites (dat menu element 0x10000014).
    public uint NormalSprite { get; set; }
    public uint PressedSprite { get; set; }
    // Popup chrome sprites (dat menu popup template, layout 0x21000006).
    public uint PopupBgSprite { get; set; }       // 0x0600124C — panel fill (191×2 tiles)
    public uint ItemNormalSprite { get; set; }    // 0x0600124E — a row background (191×17)
    public uint ItemHighlightSprite { get; set; } // 0x0600124D — the active channel's row

    public Vector4 TextColor { get; set; } = new(1f, 0.92f, 0.72f, 1f);
    /// <summary>Available item text — retail white #FFFFFF (gmMainChatUI talk-focus
    /// enabled state). Confirmed via decomp: enabled items render white.</summary>
    public Vector4 TextColorAvailable { get; set; } = new(1f, 1f, 1f, 1f);
    /// <summary>Disabled/unavailable item text — retail GREYS these (UIElement state 0xd
    /// disabled StateDesc colour). NOT the salmon colorPink (0x81c528) we had before — that
    /// belongs to the chat-MESSAGE palette and was misapplied. Exact float lives in the dat
    /// StateDesc (not a code symbol); ~0.5 neutral grey here pending a live cdb dump.</summary>
    public Vector4 TextColorGhosted { get; set; } = new(0.5f, 0.5f, 0.5f, 1f);

    private bool _open;
    // Interior = the row content; Outer = interior + the 8-piece bevel ring.
    private int   ColumnCount => (Items.Count + RowsPerColumn - 1) / System.Math.Max(1, RowsPerColumn);
    private float InteriorW => ColumnCount * ColumnWidth;
    private float InteriorH => RowsPerColumn * RowHeight;
    private float OuterW => InteriorW + 2 * Border;
    private float OuterH => InteriorH + 2 * Border;

    public UiMenu() { CapturesPointerDrag = true; }

    /// <summary>The menu draws its own button face + popup; its dat label/row children
    /// must NOT be built (an invisible label child would intercept the button click).</summary>
    public override bool ConsumesDatChildren => true;

    protected override void OnDraw(UiRenderContext ctx)
    {
        var resolve = SpriteResolve;

        // Button face (3-sliced so it can widen to fit the label) + the active-target label.
        if (resolve is not null)
        {
            var (tex, tw, _) = resolve(_open ? PressedSprite : NormalSprite);
            if (tex != 0 && tw > 0) DrawButtonFace(ctx, tex, tw);
        }
        DrawLabel(ctx, ButtonLabelProvider?.Invoke() ?? "", ButtonTextIndent, (Height - LineH()) * 0.5f, TextColor);
    }

    // 3-slice caps for the 46px LED-arrow button face (0x06004D65): a LEFT cap holding the
    // round LED socket, a stretchable plain-gold MIDDLE, and a RIGHT cap holding the arrow
    // point. Slicing keeps the LED + arrow undistorted when the button widens to its label.
    private const float FaceCapL = 20f, FaceCapR = 12f;

    private void DrawButtonFace(UiRenderContext ctx, uint tex, float tw)
    {
        float uL = FaceCapL / tw, uR = (tw - FaceCapR) / tw;
        float midDest = Width - FaceCapL - FaceCapR;
        ctx.DrawSprite(tex, 0f,               0f, FaceCapL, Height, 0f, 0f, uL, 1f, Vector4.One); // LED cap
        if (midDest > 0f)
            ctx.DrawSprite(tex, FaceCapL,      0f, midDest,  Height, uL, 0f, uR, 1f, Vector4.One); // gold body (stretched)
        ctx.DrawSprite(tex, Width - FaceCapR, 0f, FaceCapR, Height, uR, 0f, 1f, 1f, Vector4.One); // arrow cap
    }

    /// <summary>The button width that fits "LED cap + channel label + arrow cap" — retail
    /// sizes the talk-focus button to its selected label. The controller widens the button
    /// to this and reflows the input field to start after it.</summary>
    public float NaturalButtonWidth()
    {
        string text = ButtonLabelProvider?.Invoke() ?? "";
        float textW = DatFont?.MeasureWidth(text) ?? Font?.MeasureWidth(text) ?? text.Length * 7f;
        return ButtonTextIndent + textW + 4f + FaceCapR;   // text start (clears LED) + text + gap + arrow cap
    }

    /// <summary>The open popup draws in the OVERLAY pass so it sits on top of the whole
    /// UI — otherwise the translucent chat panel (drawn after this element in the main
    /// pass) greys out the part of the popup that overlaps it.</summary>
    protected override void OnDrawOverlay(UiRenderContext ctx)
    {
        var resolve = SpriteResolve;
        if (!_open || resolve is null) return;

        // Column-major popup opening UPWARD from the button, wrapped in the universal
        // 8-piece window bevel (retail UIElement_Menu::MakePopup spawns the popup as a
        // bevelled floating window). Force OPAQUE (a menu reads solid even though the
        // chat window is translucent). Draw bevel → panel fill → row sprites → labels,
        // all through the sprite bucket in submission order so labels land on top.
        ctx.PushAlphaAbsolute(1f);
        try
        {
            float outerTop = -OuterH;                 // popup bottom sits at the button top (y=0)
            float inX = Border, inY = outerTop + Border; // interior origin (inside the bevel)

            DrawBevel(ctx, resolve, 0f, outerTop, OuterW, OuterH);
            DrawSprite(ctx, resolve, PopupBgSprite, inX, inY, InteriorW, InteriorH);  // panel fill behind rows

            for (int i = 0; i < Items.Count; i++)
            {
                int col = i / RowsPerColumn, row = i % RowsPerColumn;
                float x = inX + col * ColumnWidth, y = inY + row * RowHeight;
                bool selected = Equals(Items[i].Payload, Selected);
                DrawSprite(ctx, resolve, selected ? ItemHighlightSprite : ItemNormalSprite, x, y, ColumnWidth, RowHeight);
            }

            float textY = (RowHeight - LineH()) * 0.5f;   // center the label in its row
            for (int i = 0; i < Items.Count; i++)
            {
                int col = i / RowsPerColumn, row = i % RowsPerColumn;
                // Items grey out when unavailable; when EnabledProvider is null all items are enabled.
                bool avail = EnabledProvider?.Invoke(Items[i].Payload) ?? true;
                DrawLabel(ctx, Items[i].Label, inX + col * ColumnWidth + TextIndent, inY + row * RowHeight + textY,
                          avail ? TextColorAvailable : TextColorGhosted);
            }
        }
        finally { ctx.PopAlpha(); }
    }

    /// <summary>Draw the universal 8-piece retail window bevel (corners + tiled edges +
    /// tiled centre fill) framing the rect (<paramref name="x"/>,<paramref name="y"/>,
    /// <paramref name="w"/>,<paramref name="h"/>). Reuses the same geometry +
    /// <see cref="RetailChromeSprites"/> ids as <see cref="UiNineSlicePanel"/>; no resize
    /// grips (a menu popup is not resizable).</summary>
    private void DrawBevel(UiRenderContext ctx, Func<uint, (uint tex, int w, int h)> resolve,
        float x, float y, float w, float h)
    {
        var r = UiNineSlicePanel.ComputeFrameRects(w, h, Border);
        void P(uint id, in UiNineSlicePanel.Rect d) => DrawSprite(ctx, resolve, id, x + d.X, y + d.Y, d.W, d.H);
        P(RetailChromeSprites.CenterFill, r.Center);
        P(RetailChromeSprites.TopEdge,    r.Top);
        P(RetailChromeSprites.BottomEdge, r.Bottom);
        P(RetailChromeSprites.LeftEdge,   r.Left);
        P(RetailChromeSprites.RightEdge,  r.Right);
        P(RetailChromeSprites.CornerTL,   r.TL);
        P(RetailChromeSprites.CornerTR,   r.TR);
        P(RetailChromeSprites.CornerBL,   r.BL);
        P(RetailChromeSprites.CornerBR,   r.BR);
    }

    private float LineH() => DatFont?.LineHeight ?? Font?.LineHeight ?? 14f;

    private void DrawSprite(UiRenderContext ctx, Func<uint, (uint tex, int w, int h)> resolve,
        uint id, float x, float y, float w, float h)
    {
        if (id == 0) return;
        var (tex, tw, th) = resolve(id);
        if (tex == 0 || tw == 0 || th == 0) return;
        // Tile at native size (the panel fill is 191×2; rows are 191×17 = 1:1).
        ctx.DrawSprite(tex, x, y, w, h, 0f, 0f, w / tw, h / th, Vector4.One);
    }

    private void DrawLabel(UiRenderContext ctx, string s, float x, float y, Vector4 color)
    {
        if (DatFont is { } df) ctx.DrawStringDat(df, s, x, y, color);
        else ctx.DrawString(s, x, y, color, Font);
    }

    protected override bool OnHitTest(float lx, float ly)
        => _open ? (lx >= 0 && lx < OuterW && ly >= -OuterH && ly < Height)
                 : base.OnHitTest(lx, ly);

    public override bool OnEvent(in UiEvent e)
    {
        if (e.Type != UiEventType.MouseDown) return false;

        float lx = e.Data1, ly = e.Data2;
        if (_open && ly < 0)                       // clicked inside the upward popup
        {
            // Map into the bevel interior, then to (col,row). Clicks in the bevel ring
            // (outside the interior) just close the menu.
            float ix = lx - Border, iy = ly - (-OuterH + Border);
            if (ix >= 0 && ix < InteriorW && iy >= 0 && iy < InteriorH)
            {
                int col = (int)(ix / ColumnWidth);
                int row = (int)(iy / RowHeight);
                int idx = col * RowsPerColumn + row;
                // Only pick enabled items.
                if (row >= 0 && row < RowsPerColumn && idx >= 0 && idx < Items.Count
                    && (EnabledProvider?.Invoke(Items[idx].Payload) ?? true))
                {
                    // The widget REPORTS the pick; the controller owns Selected (it sets
                    // Selected only for payloads it acts on). This mirrors retail
                    // UIElement_Menu::NewSelection delegating to the owner rather than
                    // self-selecting — so a deferred/no-op item (e.g. the Squelch /
                    // Tell-to-Selected specials, null payload) leaves the current
                    // selection + highlight unchanged when the controller ignores it.
                    OnSelect?.Invoke(Items[idx].Payload);
                }
            }
            _open = false;
            return true;
        }

        _open = !_open;                            // toggle on button click
        return true;
    }
}