using AcDream.Core.Physics;
using DatReaderWriter.Enums;
using System.Numerics;
using Xunit;

namespace AcDream.Core.Tests.Physics;

/// <summary>
/// L.2d slice 1 (2026-05-13) — unit coverage for the new
/// <see cref="PhysicsDiagnostics.ProbeBuildingEnabled"/> flag and
/// <see cref="PhysicsDiagnostics.LastBspHitPoly"/> diagnostic
/// side-channel.
///
/// <para>
/// The full multi-line <c>[resolve-bldg]</c> format itself is verified
/// by the slice's acceptance criterion #2 (live Holtburg-doorway
/// capture) — covering it here would require a heavy
/// <c>PhysicsEngine</c> + <c>ShadowObjectRegistry</c> + <c>Transition</c>
/// fixture for what's a diagnostic-only emission. These tests pin the
/// static API contract that the emission code depends on; if either of
/// these tests breaks the emission will start producing stale data or
/// failing to emit at all.
/// </para>
/// </summary>
public class PhysicsDiagnosticsTests
{
    // -----------------------------------------------------------------------
    // ProbeBuildingEnabled — flag gates the emission path.
    // -----------------------------------------------------------------------

    [Fact]
    public void ProbeBuilding_StaticApi_Roundtrip()
    {
        bool initial = PhysicsDiagnostics.ProbeBuildingEnabled;
        try
        {
            PhysicsDiagnostics.ProbeBuildingEnabled = true;
            Assert.True(PhysicsDiagnostics.ProbeBuildingEnabled);

            PhysicsDiagnostics.ProbeBuildingEnabled = false;
            Assert.False(PhysicsDiagnostics.ProbeBuildingEnabled);
        }
        finally
        {
            // Restore so a process-wide static doesn't leak between tests
            // (env-var init was the only thing that set this before).
            PhysicsDiagnostics.ProbeBuildingEnabled = initial;
        }
    }

    // -----------------------------------------------------------------------
    // LastBspHitPoly — side-channel set by BSPQuery, read by FindObjCollisions.
    //
    // TransitionTypes.FindObjCollisions clears this to null before each
    // shadow-entry dispatch; BSPQuery writes to it on hit when the probe is
    // on; the emission site reads it. A failure here means the side-channel
    // can't carry data through the call chain.
    // -----------------------------------------------------------------------

    [Fact]
    public void LastBspHitPoly_StaticApi_Roundtrip()
    {
        ResolvedPolygon? initial = PhysicsDiagnostics.LastBspHitPoly;
        try
        {
            PhysicsDiagnostics.LastBspHitPoly = null;
            Assert.Null(PhysicsDiagnostics.LastBspHitPoly);

            var synthetic = new ResolvedPolygon
            {
                Vertices = new[]
                {
                    new Vector3(-1f, 0f, 0f),
                    new Vector3( 1f, 0f, 0f),
                    new Vector3( 1f, 0f, 2f),
                    new Vector3(-1f, 0f, 2f),
                },
                Plane     = new System.Numerics.Plane(0f, 1f, 0f, -94.123f),
                NumPoints = 4,
                SidesType = CullMode.None,
            };
            PhysicsDiagnostics.LastBspHitPoly = synthetic;

            var read = PhysicsDiagnostics.LastBspHitPoly;
            Assert.NotNull(read);
            Assert.Equal(4, read!.NumPoints);
            Assert.Equal(synthetic.Plane.D, read.Plane.D);
            Assert.Same(synthetic, read);

            PhysicsDiagnostics.LastBspHitPoly = null;
            Assert.Null(PhysicsDiagnostics.LastBspHitPoly);
        }
        finally
        {
            PhysicsDiagnostics.LastBspHitPoly = initial;
        }
    }
}