using System.Numerics;
using AcDream.App.Rendering;

namespace AcDream.App.Tests.Rendering;

/// <summary>
/// S3 landing hygiene (H2): <see cref="TerrainModernRenderer.CollectVisibleCells"/>
/// is frustum-only now — its clip-plane-list and NDC-AABB scissor
/// parameters and the CPU/GPU clip-region equivalence check they fed had
/// exactly one production caller (<see cref="TerrainModernRenderer.Draw"/>),
/// and that caller never actually passed either (grep). The doorway-clip/scissor
/// rejection cases this file used to pin (<c>RejectsCellsOutsideDoorwayClipPlanes</c>,
/// <c>RejectsCellsOutsideDoorwayScissorAabb</c>, <c>UnionsCellsFromEveryLandscapeSlice</c>)
/// pinned a mechanism nothing in production ever fed — deleted with the
/// parameters. What remains still pins the one thing this method's callers
/// actually rely on: it publishes the visible terrain cell set per landblock,
/// respecting an explicit frustum when one is given.
/// </summary>
public sealed class TerrainParticleCellVisibilityTests
{
    [Fact]
    public void CollectVisibleCells_PublishesLandscapeCellsWithoutEntitySurvivors()
    {
        var cells = new HashSet<uint>();

        TerrainModernRenderer.CollectVisibleCells(
            cells,
            0xA9B4FFFFu,
            Vector3.Zero,
            zMin: 0f,
            zMax: 20f,
            frustum: null);

        Assert.Equal(64, cells.Count);
        Assert.Contains(0xA9B40001u, cells);
        Assert.Contains(0xA9B40040u, cells);
    }

    [Fact]
    public void CollectVisibleCells_ForceDrawnParentStillUsesCellFrustum()
    {
        var cells = new HashSet<uint>();
        FrustumPlanes frustum = FrustumPlanes.FromViewProjection(Matrix4x4.Identity);

        // The parent landblock may have entered TerrainModernRenderer's draw
        // list through neverCullLandblockId. The cell collector deliberately
        // receives no such bypass and still rejects its off-frustum cells.
        TerrainModernRenderer.CollectVisibleCells(
            cells,
            0xA9B4FFFFu,
            new Vector3(100f, 100f, 100f),
            zMin: 100f,
            zMax: 120f,
            frustum);

        Assert.Empty(cells);
    }
}