using System;
using System.Numerics;
using AcDream.Core.Physics;
using Xunit;
using Xunit.Abstractions;

namespace AcDream.Core.Tests.Physics;

/// <summary>
/// S6 (Campaign S, 2026-08-07) — reachability proof + containment guard for
/// the AP-83/AP-91 PerfectClip time-of-impact tails
/// (<c>TransitionTypes.CylCollideWithPoint</c> / <c>SphereCollideWithPoint</c>).
/// Contract: docs/research/2026-08-07-s6-perfectclip-containment-contract.md.
///
/// <para>
/// FINDING (not a failure — the contract explicitly anticipates this outcome):
/// BOTH scoping-doc candidate arguments for "the camera can never reach these
/// tails" fail. <c>CollisionExemption.ShouldSkip</c> only exempts a viewer
/// mover against a CREATURE target (CollisionExemption.cs:91-94) — a
/// non-creature Cyl/Sphere shadow entry passes straight through. And
/// <c>FindObjCollisionsInCell</c> walks every cell's shadow list
/// unconditionally, with no viewer skip-all gate before the per-target loop
/// (TransitionTypes.cs:3806, reached from <c>FindPrimaryCellCollisions</c> with
/// no mover-flag check, TransitionTypes.cs:2477). So the camera
/// (<c>PhysicsCameraCollisionProbe.SweepEye</c> — the ONLY production
/// PerfectClip setter, grep-confirmed against the whole src tree) DOES reach
/// both TOI tails whenever its PathClipped, never-grounded foot sphere
/// (moverFlags carry PathClipped; body=null + isOnGround=false means neither
/// Contact nor OnWalkable is ever seeded) overlaps a non-creature Cyl/Sphere
/// shadow entry. That population is real production content: static
/// landblock scenery with a CylSphere/Sphere and no physics BSP registers
/// with <c>EntityCollisionFlags.None</c>
/// (<c>LandblockPhysicsPublisher.PublishStaticEntity</c>, tracked live via
/// <c>publication.CylinderOwnerCount</c>).
/// </para>
///
/// <para>
/// These tests drive the REAL production resolve
/// (<c>PhysicsEngine.ResolveWithTransition</c>) with the camera's exact call
/// shape (IsViewer|PathClipped|FreeRotate|PerfectClip, single 0.3 m sphere,
/// body=null, isOnGround=false — mirrors <c>PhysicsCameraCollisionProbe
/// .SweepEye</c> and the harness already used by
/// <c>CameraCornerSealReplayTests</c> / <c>Issue180CorridorSweepHysteresis
/// ReplayTests</c>) against a synthetic Cyl/Sphere shadow entry, and assert
/// the guard (<c>PhysicsDiagnostics.RecordCylPerfectClipTailReach</c> /
/// <c>RecordSpherePerfectClipTailReach</c>) records the reach as camera-live,
/// never as unverified.
/// </para>
///
/// <para>
/// <b>Sabotage</b> (deliverable 3): the contract's literal wording is "disable
/// the exemption that cuts the chain and watch the reachability flip" — but
/// the proof found NOTHING currently cuts the chain for a non-creature
/// target, so there is no existing cut to disable. The faithful adaptation
/// flips the SAME one axis <c>CollisionExemption.ShouldSkip</c> actually
/// reads (<c>EntityCollisionFlags.IsCreature</c>) from off to on and asserts
/// reachability inverts: the guard goes silent and the camera walks straight
/// through, exactly the retail "camera ray ignores creatures" rule
/// (acclient_2013_pseudo_c.txt:276787-276790). This proves the guard is wired
/// to the actual condition the reachability proof depends on, not merely
/// "always fires regardless of input".
/// </para>
/// </summary>
public class S6PerfectClipTailContainmentTests
{
    private readonly ITestOutputHelper _out;
    public S6PerfectClipTailContainmentTests(ITestOutputHelper output) => _out = output;

    private const uint TestLandblockId = 0xA9B40000u;
    private const uint TestCellId = TestLandblockId | 0x0001u;   // landcell (0,0), matches CylSphereFamilyTests/SphereCollisionFamilyTests

    private const float ViewerSphereRadius = 0.3f;   // retail viewer_sphere (acclient :93314)

    private static readonly ObjectInfoState CameraMoverFlags =
        ObjectInfoState.IsViewer | ObjectInfoState.PathClipped
        | ObjectInfoState.FreeRotate | ObjectInfoState.PerfectClip;

    // ───────────────────────────────────────────────────────────────
    // Sphere tail (AP-91)
    // ───────────────────────────────────────────────────────────────

    [Fact]
    public void CameraSweep_HitsNonCreatureSphereProp_ReachesTail_RecordsCameraLive()
    {
        PhysicsDiagnostics.ResetPerfectClipTailGuardForTest();
        var engine = BuildEngine();
        RegisterSphere(engine, 0x00005001u, new Vector3(12f, 14f, 1.0f), radius: 1.0f,
            flags: EntityCollisionFlags.None);   // static prop, not a creature

        Vector3 pivot = new(12f, 10f, 1.0f);
        Vector3 eye   = new(12f, 20f, 1.0f);   // straight through the prop's center

        var r = SweepViewer(engine, pivot, eye, TestCellId);

        _out.WriteLine(FormattableString.Invariant($"ok={r.Ok} pos=({r.Position.X:F3},{r.Position.Y:F3},{r.Position.Z:F3}) collNorm={r.CollisionNormalValid} normal=({r.CollisionNormal.X:F3},{r.CollisionNormal.Y:F3},{r.CollisionNormal.Z:F3}) cameraLive={PhysicsDiagnostics.SphereToiCameraLiveCount} unverified={PhysicsDiagnostics.SphereToiUnverifiedCount}"));

        Assert.True(PhysicsDiagnostics.SphereToiCameraLiveCount > 0,
            "The camera's PathClipped, never-grounded sweep must reach the Sphere PerfectClip TOI tail (AP-91) for a non-creature target.");
        Assert.Equal(0, PhysicsDiagnostics.SphereToiUnverifiedCount);

        // Golden: the sphere prop must have stopped the camera's forward sweep
        // (PathClipped hard-stops at first contact) well short of the far side.
        Assert.True(r.Position.Y < 14f,
            $"camera must be stopped by the prop, not pass through it; got Y={r.Position.Y:F3}");
        Assert.True(r.Position.Y > 11f,
            $"camera must actually reach the prop's surface, not stop early; got Y={r.Position.Y:F3}");
    }

    [Fact]
    public void CameraSweep_HitsCreatureFlaggedSphere_ExemptionCutsChain_GuardStaysSilent()
    {
        PhysicsDiagnostics.ResetPerfectClipTailGuardForTest();
        var engine = BuildEngine();
        // SABOTAGE: flip the one axis CollisionExemption.ShouldSkip reads for a
        // viewer mover — everything else about the geometry is identical to the
        // reached case above.
        RegisterSphere(engine, 0x00005002u, new Vector3(12f, 14f, 1.0f), radius: 1.0f,
            flags: EntityCollisionFlags.IsCreature);

        Vector3 pivot = new(12f, 10f, 1.0f);
        Vector3 eye   = new(12f, 20f, 1.0f);

        var r = SweepViewer(engine, pivot, eye, TestCellId);

        _out.WriteLine(FormattableString.Invariant($"ok={r.Ok} pos=({r.Position.X:F3},{r.Position.Y:F3},{r.Position.Z:F3}) cameraLive={PhysicsDiagnostics.SphereToiCameraLiveCount}"));

        Assert.Equal(0, PhysicsDiagnostics.SphereToiCameraLiveCount);
        Assert.Equal(0, PhysicsDiagnostics.SphereToiUnverifiedCount);
        // Reachability flips: CollisionExemption now exempts the whole target
        // for the viewer mover before shape dispatch, so the camera sails
        // straight through to the far side (retail: camera ray ignores
        // creatures, acclient_2013_pseudo_c.txt:276787-276790).
        Assert.True(r.Position.Y > 19f,
            $"a creature-flagged prop must be fully exempt for a viewer mover; got Y={r.Position.Y:F3}");
    }

    // ───────────────────────────────────────────────────────────────
    // Cyl tail (AP-83)
    // ───────────────────────────────────────────────────────────────

    [Fact]
    public void CameraSweep_HitsNonCreatureCylinderProp_ReachesTail_RecordsCameraLive()
    {
        PhysicsDiagnostics.ResetPerfectClipTailGuardForTest();
        var engine = BuildEngine();
        RegisterCylinder(engine, 0x00006001u, new Vector3(12f, 14f, 0f), radius: 1.0f, height: 2.0f,
            flags: EntityCollisionFlags.None);

        Vector3 pivot = new(12f, 10f, 1.0f);
        Vector3 eye   = new(12f, 20f, 1.0f);

        var r = SweepViewer(engine, pivot, eye, TestCellId);

        _out.WriteLine(FormattableString.Invariant($"ok={r.Ok} pos=({r.Position.X:F3},{r.Position.Y:F3},{r.Position.Z:F3}) collNorm={r.CollisionNormalValid} normal=({r.CollisionNormal.X:F3},{r.CollisionNormal.Y:F3},{r.CollisionNormal.Z:F3}) cameraLive={PhysicsDiagnostics.CylToiCameraLiveCount} unverified={PhysicsDiagnostics.CylToiUnverifiedCount}"));

        Assert.True(PhysicsDiagnostics.CylToiCameraLiveCount > 0,
            "The camera's PathClipped, never-grounded sweep must reach the Cyl PerfectClip TOI tail (AP-83) for a non-creature target.");
        Assert.Equal(0, PhysicsDiagnostics.CylToiUnverifiedCount);

        Assert.True(r.Position.Y < 14f,
            $"camera must be stopped by the prop, not pass through it; got Y={r.Position.Y:F3}");
        Assert.True(r.Position.Y > 11f,
            $"camera must actually reach the prop's surface, not stop early; got Y={r.Position.Y:F3}");
    }

    [Fact]
    public void CameraSweep_HitsCreatureFlaggedCylinder_ExemptionCutsChain_GuardStaysSilent()
    {
        PhysicsDiagnostics.ResetPerfectClipTailGuardForTest();
        var engine = BuildEngine();
        RegisterCylinder(engine, 0x00006002u, new Vector3(12f, 14f, 0f), radius: 1.0f, height: 2.0f,
            flags: EntityCollisionFlags.IsCreature);

        Vector3 pivot = new(12f, 10f, 1.0f);
        Vector3 eye   = new(12f, 20f, 1.0f);

        var r = SweepViewer(engine, pivot, eye, TestCellId);

        _out.WriteLine(FormattableString.Invariant($"ok={r.Ok} pos=({r.Position.X:F3},{r.Position.Y:F3},{r.Position.Z:F3}) cameraLive={PhysicsDiagnostics.CylToiCameraLiveCount}"));

        Assert.Equal(0, PhysicsDiagnostics.CylToiCameraLiveCount);
        Assert.Equal(0, PhysicsDiagnostics.CylToiUnverifiedCount);
        Assert.True(r.Position.Y > 19f,
            $"a creature-flagged prop must be fully exempt for a viewer mover; got Y={r.Position.Y:F3}");
    }

    // ───────────────────────────────────────────────────────────────
    // Harness (mirrors CylSphereFamilyTests / SphereCollisionFamilyTests)
    // ───────────────────────────────────────────────────────────────

    private static PhysicsEngine BuildEngine()
    {
        var cache = new PhysicsDataCache();
        var engine = new PhysicsEngine { DataCache = cache };

        // Flat terrain at Z=0 across the whole landblock — irrelevant to these
        // sweeps (they travel at Z≈1.0, well above ground) but required so the
        // outdoor cell resolves.
        var heights = new byte[81];
        var heightTable = new float[256];   // all zero → terrain Z = 0
        engine.AddLandblock(
            landblockId:  TestLandblockId,
            terrain:      new TerrainSurface(heights, heightTable),
            cells:        Array.Empty<CellSurface>(),
            portals:      Array.Empty<PortalPlane>(),
            worldOffsetX: 0f,
            worldOffsetY: 0f);

        return engine;
    }

    /// <summary>
    /// Mirror of PhysicsCameraCollisionProbe.SweepEye's transition call — same
    /// shape already used by CameraCornerSealReplayTests,
    /// Issue180CorridorSweepHysteresisReplayTests, and CylSphereFamilyTests'
    /// landblock (0x0100 low word stays below the AdjustPosition threshold, so
    /// the outdoor cellId is used as-is).
    /// </summary>
    private static ResolveResult SweepViewer(PhysicsEngine engine, Vector3 pivot, Vector3 desiredEye, uint cellId)
    {
        Vector3 begin = pivot      - new Vector3(0f, 0f, ViewerSphereRadius);
        Vector3 end   = desiredEye - new Vector3(0f, 0f, ViewerSphereRadius);

        return engine.ResolveWithTransition(
            currentPos:     begin,
            targetPos:      end,
            cellId:         cellId,
            sphereRadius:   ViewerSphereRadius,
            sphereHeight:   0f,
            stepUpHeight:   0f,
            stepDownHeight: 0f,
            isOnGround:     false,
            body:           null,
            moverFlags:     CameraMoverFlags,
            movingEntityId: 0);
    }

    private static void RegisterSphere(PhysicsEngine engine, uint entityId, Vector3 worldPos,
        float radius, EntityCollisionFlags flags)
    {
        engine.ShadowObjects.Register(
            entityId, gfxObjId: 0u,
            worldPos, Quaternion.Identity, radius,
            worldOffsetX: 0f, worldOffsetY: 0f, landblockId: TestLandblockId,
            collisionType: ShadowCollisionType.Sphere,
            cylHeight: 0f, scale: 1f,
            state: 0u,
            flags: flags,
            isStatic: true);
    }

    private static void RegisterCylinder(PhysicsEngine engine, uint entityId, Vector3 worldPos,
        float radius, float height, EntityCollisionFlags flags)
    {
        engine.ShadowObjects.Register(
            entityId, gfxObjId: 0u,
            worldPos, Quaternion.Identity, radius,
            worldOffsetX: 0f, worldOffsetY: 0f, landblockId: TestLandblockId,
            collisionType: ShadowCollisionType.Cylinder,
            cylHeight: height, scale: 1f,
            state: 0u,
            flags: flags,
            isStatic: true);
    }
}