// IndoorDrawPlan.cs
//
// Pure (GL-free) port of the membership half of retail PView::DrawCells (0x5a4840):
// the reverse cell_draw_list iterated per portal_view slice. EVERY visible cell with a
// non-empty view is included — there is NO "drawable" filter. Dropping cells without a
// clip-slot was the grey-walls bug (the cell's sealed shell never drew → clear color showed).
using System.Collections.Generic;

namespace AcDream.App.Rendering;

public readonly record struct CellDrawEntry(uint CellId, IReadOnlyList<ViewPolygon> Slices);

public static class IndoorDrawPlan
{
    /// <summary>Reverse OrderedVisibleCells (far→near), each visible cell with its view
    /// slices. Mirrors DrawCells' shell/object loops. Cells whose view is empty are skipped
    /// (they are not actually visible); no other cell is ever dropped.</summary>
    public static List<CellDrawEntry> ShellPass(PortalVisibilityFrame frame)
    {
        var result = new List<CellDrawEntry>(frame.OrderedVisibleCells.Count);
        for (int i = frame.OrderedVisibleCells.Count - 1; i >= 0; i--)
        {
            uint cellId = frame.OrderedVisibleCells[i];
            if (!frame.CellViews.TryGetValue(cellId, out var view) || view.IsEmpty)
                continue;
            result.Add(new CellDrawEntry(cellId, view.Polygons));
        }
        return result;
    }
}