namespace AcDream.Core.Meshing;

/// <summary>
/// Should a hydrated stab/entity survive when its visual mesh flattens to
/// zero drawable parts?
///
/// <para>
/// <b>Why this exists (#79/#93, 2026-07-09).</b> A dat-authored "light attach
/// point" is a Setup whose sole purpose is to carry a <c>Setup.Lights</c>
/// entry — its own visual part is commonly a #136-class runtime-hidden
/// marker (degrades to nothing at any real distance, matching retail's
/// editor-only placement markers). Retail's light registration
/// (<c>CObjCell::add_light</c>, populated at <c>CEnvCell::UnPack</c>) is
/// entirely independent of a fixture's own mesh visibility — a mesh-less
/// carrier still lights the room. The Town Network fountain room's only
/// light (Setup 0x02000365, a ceiling fixture 5 m above the fountain) never
/// registered because the mesh-empty gate treated "nothing to draw" as
/// "nothing exists," dropping the entity — and its Lights — before the
/// light-registration pass ever saw it.
/// </para>
/// </summary>
public static class EntityHydrationRules
{
    /// <summary>
    /// True when the entity should still be added to the landblock's entity
    /// set even with zero mesh refs, because it has dat-authored lights to
    /// register. An entity with any mesh is always kept (unchanged from the
    /// pre-existing gate); the entity is dropped only when it has neither
    /// geometry to draw nor lights to register.
    /// </summary>
    public static bool ShouldKeepEntity(int meshRefCount, int setupLightCount)
        => meshRefCount > 0 || setupLightCount > 0;
}